today we're talking all about humidity. Humidity! Humidity is probably something that you are familiar with. But you're probably not used to measuring it in 12 million different ways.

Why do we measure it in 12 million different ways? I do not have a good answer for you. Um - but there, there's three main terms that I want to introduce you guys to today. That's relative humidity, specific humidity, and mixing ratio. Relative humidity is probably the one ya'll are most familiar with. So, when I was writing the script for this video it was 91 degrees outside and 43% humidity.

So, when we see humidity measure in a percent, that like 43%, like it usually is in weather forecasts or on your favorite weather app, that is relative humidity. Relative humidity measures how much water vapor is currently in the air versus how much water vapor can the air possibly hold and it has units of percent.

So, 100% humidity would be the air has as much water vapor as it can possibly hold. It can't hold any more. And if you tried to shove more water vapor into that parcel of air it would immediately condense out into a liquid. So for example, if you were inside a cloud or in fog the relative humidity in those two places is going to be 100%.

Specific humidity is different from relative humidity in that specific humidity is a measure of exactly how much water vapor there is in the air right now. So specific humidity actually looks like this: Specific humidity is the mass of the water vapor divided by the mass of the water vapor plus the mass of the dry air. And this is going to have units of grams per kilogram.

So how much water vapour do I have in one kilogram of air. Mixing ratio - super super similar - looks like this: It's the mass of the water vapor over just the mass of the dry air. It's also measured in grams per kilogram. Why do we have these two different things when they're so so so so similar? Um - I'm pretty sure mixing ration is a term that sort of comes over to us from chemistry.

I'm not exactly sure where specific humidity came from. But these guys are almost interchangeable but that is the difference. The difference is in the denominator. For mixing ratio it's just the dry air for specific humidity the mass of the water vapor is included in the denominator. Realistically, you can use either of those guys to calculate relative humidity.

Relative humidity then would just be this: The, let's say, specific humidity divided by the saturation value and then times 100% to get us into the right units. So what is this saturation value? And why is relative humidity often more intuitive than specific humidity or mixing ratio?

Two flight control surfaces are part of the high lift control system: the Leading Edge slats and the trailing Edge Flaps. In the sixth part of the series, we will understand the flap mechanism. The triple seven has four flaps: two single slotted outboard flaps and two double slotted inboard flaps. The flaps are fly-by-wire controlled and have three modes of operation.

The flap position is controlled by using the flap lever. The lever has multiple positions for different slat and flap configurations. A position transducer keeps track of the current flap lever position. A change in lever position causes the transducer position signal to change. The signal is received by the flap slat Electronics unit computer. The flap computer engages the primary mode. Flap lever position 1 results in slat movement. Since we are interested in trailing Edge flap movement, let's skip to flaps 5.

In position 5, the computer will operate the flap power Drive Unit. A signal is sent to the hydraulic control valve. Aircraft Center hydraulic system pressure is used to operate the flaps. The valve opens to run the hydraulic motor. The motor turns the PDU gearbox connected to the torque tubes. The torque tubes will now drive four transmission assemblies on each wing. The transmission assemblies rotate the ball screw using the torque tube's input. The torque tubes cannot run straight from the power Drive Unit to the last transmission assembly; therefore, tubes are rerouted with the help of angle gearboxes.

Of the four transmission assemblies, two will move the inboard flap, and the other two will move the outboard flap. Let's see how the transmission assemblies extend the flap. The ball screw rotation moves a nut. The nut is connected to the drive arm. The drive arm moves the carrier beam, and the flap extends.

Flaps 15. A similar mechanism extends the inboard flap. Two position sensors, one for each wing, measure the torque tube rotation to help the flap computer determine the current flap position. Flaps 20. When a flap position change command is given, the position sensor signal helps the flap computer to stop the movement once the flap has reached the selected setting. The inboard flap is a combination of two parts: main flap and the AFT flap. When the lever is selected to flaps 25, as the transmission assemblies extend the inboard flap, mechanical push rod connections will deflect the AFT flap more than the main flap.

The final flap lever position 30. If the commanded flaps fail to deflect due to hydraulic system failure, the flap computer will automatically switch to the secondary mode. In secondary mode, the FSEU will command the power Drive Unit electric motor to operate the flaps. The primary flight computer receives the flap position data from the FSEU. This allows the PFC to droop the flapperons and improve low-speed performance. The PFC also droops the ailerons in some flat positions.

Now let's retract the flaps to the up position. The retraction process is similar to extension. The lever command is received by the flap computer. The computer will run the motor in the opposite direction. This will reverse the torque tube rotation, and the flaps retract. If a flap computer or any other component failure prevents the system from working in the current mode, then the alternate flap switch can be used to extend or retract the flaps.

The system must be armed before using the alternate switch. The arm switch will send a signal to the FSEU to disengage the current mode, and the computer will stop controlling the flaps. Let's continue flap retraction using the alternate switch. When the alternate switch is used, a direct signal is sent to the electric motor to retract the flaps. The switch must be turned off after the flaps have reached the desired position.

Today we're talking about adiabatic processes. What in the world does adiabatic mean?

Well, imagine that you have a magic balloon and you want to change the temperature of the gas inside the balloon. You're probably thinking to yourself, "Ya - ya put it out in the sun, Maddie! You let it heat up. If you want to cool it down, put it in your freezer. This is not hard." And you're totally right, but those are both examples of diabatic processes.

A diabatic process is anything that is going to change the temperature of a system by either adding or removing heat from that system. So if that's what a diabatic process is, then an adiabatic, usually pronounced adiabatic, an adiabatic process is one that's going to change the temperature of our system without adding or removing heat.

Well, how in the world does that work? Great question. But we've actually seen this type of process. Uh, I think last video, when we did the ideal gas law. Imagine that we let our balloon go. Timmy here is sad. As the balloon rises, the pressure exerted on the balloon is going to decrease.

Fun Navy fact. In the Navy, you're not actually supposed to say increasing or decreasing. You're supposed to say goes up or goes down. Because increasing and decreasing sound too close to each other that if you're on an old like sound powered phone, then you might get them mixed up. So you're always supposed to say goes up or goes down when you're - for proper phone talking procedures. Believe it or not, every word in that sentence was correct.

So we're going to have to see temperature as well in order to keep the equation balanced. So density is going to go down. Now, assuming that we tied our knot really tight and no air is leaking out of the balloon, that change in density will look like an increase in volume. So we - we get a big balloon.

And then we'll also see the temperature go down. And that's what we're interested in here. So this drop in temperature was caused by an adiabatic process. The dark, dark science magic of being able to change temperature without actually doing anything to the heat energy of the system.

We actually usually think about adiabatic processes so that we can like eliminate them. Adiabatic processes don't drive the weather generally. They don't drive storms. So if I'm interested in something like how does the temperature change in the atmosphere leading up to storm "X" over here, um, matter for the storm's development, something like that, then what I would want to do is look at the change of temperature and first remove or subtract out all of the adiabatic changes in temperature so that all I'm left with are the diabatic changes.

The diabatic changes are generally the interesting, complex bits. So it helps to remove the adiabatic processes first. Or to think about those as separate things. Moving forward we're going to talk a lot about adiabatic and diabatic processes and now, good job you, you know the difference.

The Boeing 777 has 14 spoilers. The left wing has seven: five outboard and two inboard spoilers. Likewise, the right wing has seven: two inboard and five outboard spoilers. Spoilers serve two purposes on the aircraft. They assist the flaperons and ailerons during roll control, and they also act as speed brakes.

Each spoiler is connected to a power control unit (PCU). The PCUs are hydraulic actuators and use different hydraulic systems of the aircraft for redundancy. For the PCUs to actuate, they need input signals, and there are four possible sources. The roll signal can be given by using the control wheels or by the autopilot computer. The speed brake signal can be manual or automatic. The auto speed brake system will not be covered in the flight control series.

Let's start with the control wheels. As we saw in the previous chapter, when the control wheels are rotated to give a roll command, the position transducers send the wheel position signal to the flight computers. The control wheel rotation also sends a mechanical signal through cables. The mechanical signal will directly control numbers four and eleven spoilers. The electrical signal is processed by the actuator control electronics (ACE) and transferred to the primary flight computer (PFC). The PFC informs the ACE to deflect the flaperons and the ailerons. It also informs the ACE to operate the spoilers.

The ACE will now electrically open the control valves on the spoiler PCUs. On the left wing, as the flaperon and aileron deflect upwards, the spoilers move up. On the right wing, as the flaperon and aileron deflect downwards, no control input is given to the spoilers on the right side during a roll command. The number four spoiler on the left wing is not fly-by-wire controlled. It is operated by the mechanical cable connected directly to the control wheels. The cable movement opens the PCU hydraulic valve, and the spoiler moves up.

When a right roll command is given, the fly-by-wire controlled spoilers on the right wing deflect up, and the left-wing spoilers are not controlled. The number eleven spoiler will move with the mechanical input from the control wheels.

Next, the autopilot input resulting in spoiler deflection. The autopilot computer requests a roll command to the primary flight computer (PFC). The PFC will send two calculated signals: one for the ACE to move the control surfaces and the other for the autopilot computer to back drive the control wheels. As the ACE moves the fly-by-wire controlled spoilers and other surfaces, the autopilot computer back drives the control wheels. Control wheel rotation will move the mechanically controlled number four spoiler. Once the autopilot command is over, the surfaces and the control wheels will return to neutral position.

Finally, let's see the speed brake control. The speed brake lever is used to deflect the spoilers. The lever has three positions: spoilers down, armed for auto speed brake, and up for manual control. Selecting the lever to the up position will move a clutch assembly. The change in position is picked up by the transducer. The position transducer sends a signal to the flight computer through the ACE. The PFC commands the ACE to move all 14 spoilers to their maximum deflection. During an aircraft roll command, the control wheels give the mechanical signal to the number four and eleven spoilers, which is not possible when using the speed brake lever. Therefore, during speed brake extension, all spoilers are fly-by-wire controlled, including numbers four and eleven.

Gyroscopic instruments include the attitude indicator, the heading indicator, and the turn coordinator. These are considered gyroscopic instruments because each one relies upon a gyroscope to function. They can either be driven by air suction or electricity. These instruments provide the pilot with such things as their pitch, bank, yaw, and heading.

Before we get into each instrument, let's talk about what a gyroscope, or gyro, is and how it works. In its simplest form, a gyro is a heavily weighted spinning disk that is able to maintain its position and orientation. Gyros operate based on two principles: rigidity in space and precession. Rigidity in space refers to a gyro's ability to remain in a fixed position in the plane in which it is spinning. By mounting the gyroscope on a set of gimbal rings, the gyro is able to rotate freely in any direction. Thus, if the gimbal ring rotates, the spinning gyro will remain in the same plane in which it was originally spinning.

The other property of the gyro is known as precession. Precession is the tilting or turning of a gyro in response to a force. For instance, a small force is applied to the gyro whenever the airplane changes direction. However, instead of the gyro responding at the source of the force as expected, the result will instead occur 90 degrees ahead of that point in the direction of rotation. This means that sometimes the instruments may have some unwanted errors, such as slow drifting and minor erroneous indications. The good news is that all gyroscopic instruments have ways to either automatically or manually correct for this precession error.

In order for gyroscopic instruments to work, the gyros have to spin at a very high speed. As previously stated, the instruments can either be powered by air or electricity. For safety reasons, different instruments are powered by different sources so that if one source fails, the other source will still work. The attitude and heading indicators are typically powered by air, and the turn coordinator is powered by electricity. The spinning of the gyros with air is accomplished not by blowing but by sucking air around it. A vacuum pump connected to and powered by the engine draws filtered air from the cabin through the instruments, spinning the gyros, and then dumps out the air into the engine compartment.

Let's look at some of the different instruments that use gyros.

Attitude Indicator: An attitude indicator is an instrument used to inform the pilot of the orientation or attitude of the aircraft relative to Earth. It indicates pitch, which is the fore and aft tilt, and bank or roll, which is the side-to-side tilt, through the use of an artificial horizon and miniature airplane. The instrument depicts the position of the airplane in relation to the true horizon. This is especially useful when the natural horizon is obscured by clouds, the visibility is poor, or when flying at night. Along the outer rim are tick marks to indicate bank at the 0, 10, 20, 30, 60, and 90 degrees angles of bank. Degrees of pitch are located both above and below the artificial horizon in either 5 or 10 degree increments. At the top of the instrument is a small triangle that points to the correct bank angle. The plane in the center of the miniature airplane lines up with the current pitch. The gyro in this instrument spins around the vertical axis, meaning that the gyro rotates level with the horizon. The two gimbals holding the gyro allow the gyro to move freely and maintain its level orientation as the airplane manoeuvres. Connections to the instrument face will then show the aircraft's attitude to the pilots. Note that if the airplane is experiencing an excessive pitch or bank, or if the vacuum pump is not providing enough suction to spin the gyro, this instrument can read inaccurately.

Heading Indicator: The heading indicator senses the airplane's movements and displays heading based on the 360-degree azimuth in five degree increments. The tick marks are labeled every 30 degrees with the final zero omitted. For example, the number six indicates a heading of 60 degrees, 21 indicates a heading of 210 degrees. The heading indicator does not have any built-in heading sensing ability, so at the start of every flight after the engine is running, the pilot must realign the instrument to the correct heading by referencing the aircraft's magnetic compass. To accomplish this, push in the knob on the lower left side of the instrument. This both disconnects the gyro from the compass card and aligns the gear of the knob with the gears connected to the compass card. When complete, release the knob and the gyro will reconnect to the compass card. Unlike the attitude indicator, the heading indicator is oriented so that only the horizontal axis is used to drive the display. When the aircraft turns, the gyro and attached main drive gear remain in their original orientation. This then causes the main drive gear to rotate the compass card gear, which then rotates the compass card on the face of the instrument. Note that due to friction and precession, the heading indicator may slowly drift away from the correct heading. Because of this, the pilot should double-check the accuracy of the instrument against the magnetic compass and realign as necessary. This should be done roughly every 15 minutes or so. Keep in mind if the vacuum pump is not producing sufficient suction when the engine is idling, the drift may be greater.

Turn Coordinator: The turn coordinator is a supporting instrument used while banking. It is used both to indicate the rate and quality of the turn. It can also be used as a backup source of bank information in the event the attitude indicator fails. In the center of the face of the instrument lies a miniature airplane that indicates the rate of turn the aircraft is currently in. Two tick marks indicate level; the other two tick marks indicate what is called a standard rate turn. A standard rate turn is one that takes two minutes to complete a 360-degree full circle. This is the rate that all pilots fly when in instrument meteorological conditions, meaning they have no outside references to follow. Below the miniature aircraft is an inclinometer, which incorporates a ball inside a tube filled with kerosene. The ball can freely move left and right and will travel in whatever direction aerodynamic forces push and pull it. Ideally, the ball should always be centered, which means the aircraft is coordinated. If aerodynamic forces are unbalanced, the ball will slide left to right. This happens when there is either too much or too little rudder being used with the current amount of bank. These two conditions are referred to as a slip and a skid. In a slip, there is not a great enough rate of turn for the amount of bank; the pilot needs to add more rudder and/or reduce the bank. In a skid, there is too much of a rate of turn for the amount of bank; the pilot needs to add more bank and/or reduce the amount of rudder. The easiest way to remember how to fix these situations is just to step on the ball. This means that when the ball is deflected off-center, step on the respective rudder pedal that the ball is deflected toward. A ball deflected left means step on the left rudder; conversely, a ball deflected right means step on the right rudder.

To get this instrument to function, it is typically powered by electricity. For this instrument, the gyro rotates from a motor located in its center. The gyro is mounted so it can remain upright while in a turn. Mechanical linkages then connect the gyro to the miniature airplane on the front of the instrument. A spring is installed to help return the miniature airplane back to level. Because of this, the pilot would never know if the instrument has failed. So if the instrument is not receiving electrical power, a red flag will be visible on the face of the instrument. Another important aspect to notice on the inside of the instrument is that the gimbal holding the gyro is not level; in fact, it's actually rotated 30 degrees. Unlike its older cousin, the turn and slip indicator, this change allows the instrument to also measure the rate of roll as you enter the turn.

An aircraft with a fixed pitch propeller has only two engine control levers: throttle and mixture. You set the engine power output using the engine RPM. If your aircraft is fitted with a variable pitch propeller, an additional control lever and instrument are required. A variable pitch propeller can also be called a constant speed propeller. The throttle adjusts the amount of fuel going to the engine, but instead of RPM, the engine power output is monitored with a manifold absolute pressure gauge. This gauge is calibrated in inches of mercury, so it's common practice to refer to engine power output simply as inches, written as inches MAP.

he additional control lever is labeled RPM but is commonly called the prop lever, even by the examining authority. The forward position of the prop lever is used to increase RPM, while the aft position is used to decrease RPM. However, it's not quite that simple. As you learned when studying piston engines, the prop lever is only connected to the spring in the constant speed unit. It's better to think of the prop lever as a request lever. The constant speed unit will always try to give you the RPM you want, but under some situations, it won't be able to, as we will see shortly.

When an aircraft with a variable pitch propeller is on the ground, the prop lever is always positioned fully forward. The throttle is used to adjust thrust for taxiing as normal. The illustration shows an aircraft lined up on the runway ready to take off. The brakes are set, and the engine is idling. Under these conditions, the propeller will be in the fully fine position with the blades on their fine pitch stops. Gently open the throttle, and you can see both the RPM and the manifold pressure increasing to the takeoff values. Because the blades are at the optimum angle of attack, the propeller will give maximum efficiency.

Now, release the brakes. As soon as the aircraft begins to move forwards, the constant speed unit will start to increase the pitch; otherwise, the RPM would increase. This is why the variable pitch propeller is also called a constant speed propeller. The mechanism maintains a constant RPM when the true airspeed changes. There is a maximum time limit of five minutes for full takeoff thrust, so as soon as any obstacles are cleared and the aircraft is established in the climb, the engine power can be reduced to maximum continuous. In this example, the manifold pressure is reduced to 35 inches MAP.

Climb is then continued to the chosen cruise altitude. You can see the blade angle being increased to maintain the optimum angle of attack. You now have to level off and reduce power output to the cruise settings. In this example, we'll use 23 inches and 2,300 RPM for the cruise. The recommended practice when reducing the engine power is to reduce the manifold pressure first. Gently use the throttle to give 23 inches of manifold pressure. Now, gently pull the prop lever back to reduce the RPM to 2,300.

The advantage of a variable pitch propeller is that under most normal operating conditions, the optimum blade angle of attack is maintained, ensuring the propeller operates with maximum efficiency. But what would happen if the throttle is closed or the engine fails? There is now no shaft power trying to maintain the requested 2,300 RPM. The constant speed unit will fine off the blades, but it can only do so until they reach the fine pitch stop, after which the RPM will decrease. The propeller is now generating drag instead of thrust, and torque is acting to keep the propeller rotating. In fact, the forward motion of the aircraft is rotating the propeller. The propeller is said to be windmilling. The drag from a windmilling propeller is known as windmilling drag.

On a single-engine aircraft with a variable pitch propeller, there is no mechanism to feather the propeller to reduce windmilling drag. However, it is possible to reduce windmilling drag on a single-engine aircraft by pulling back the prop lever. You have requested a lower RPM, so the constant speed unit will drive the propeller blades towards coarse. This reduces windmilling drag.

On a multi-engine aircraft, windmilling drag on the failed engine must be reduced to keep VMC as slow as possible, so a mechanism is incorporated to drive the propeller past the coarse pitch stop into the feathered position. The blades are now at a zero lift angle of attack. There is no torque because the airflow is no longer able to rotate the propeller, and drag from the stationary propeller is minimised, thus reducing asymmetric thrust.

We know that a propeller generates thrust by accelerating air rearwards. Therefore, a more powerful engine will require a propeller that can accelerate a greater mass of air rearwards. A propeller can accelerate more air rearwards by increasing the RPM, but this will give increased tip speed. Increasing the blade length can also be used to accelerate more air rearwards, but this will also give increased tip speed. If the tip speed exceeds the local speed of sound, shockwaves will decrease thrust and increase the rotational drag. Supersonic tip speed will also greatly increase the noise generated by the propeller.

So maximum tip speed imposes a limit on propeller diameter and RPM. However, there are other limitations on propeller diameter. Adequate ground clearance is one consideration, and fuselage interference on multi-engine aircraft is another. With these restrictions in mind, increased power absorption from a propeller can be obtained by increasing the number of blades. A three-blade propeller can accelerate a greater mass of air rearwards without excessive tip speed or problems with ground clearance or fuselage interference. Increasing the number of blades increases the solidity of the propeller disc.

As you can see, a more powerful engine will require a propeller with four blades, which will further increase the solidity of the propeller disc. An even more powerful engine might require as many as five blades. For a conventional propeller, five blades is the maximum number. Beyond five blades, the solidity of the disc is so high that not enough air can pass between the blades to be accelerated, so propeller efficiency begins to decrease. Any further increase in engine power would require contra-rotating propellers, two propellers rotating in opposite directions on the same shaft. Contra-rotating propellers are not very common.

However, a type of propeller very common on light twin-piston engine aircraft is counter-rotating propellers. These have nothing to do with power absorption, but as their name is very similar, it is worth reviewing the difference. Counter-rotating propellers are two propellers rotating in opposite directions on different shafts. Counter-rotating propellers are fitted to eliminate a critical engine. The next lesson will cover more on this topic.

The rudder provides yaw control and can be operated using three different inputs: the rudder pedals, autopilot command, and the rudder trim system.

Let's start with the rudder pedals. The pedals move on their pivot axis with the help of pedal arms. Control rods connected to the arms rotate the jack shaft assembly. The jack shafts move the control rods connected to the left and right shaft assembly. The rods move to rotate the shaft assemblies. The two sets of pedals are connected with a bus rod. The bus rod ensures when one pilot operates the pedals, the other side has the same movement. This gives the other pilot an indication of pedal position. The rudder feel and centering mechanism provides the feel force to the rudder pedals. As the pedals travel further, it gets harder to push, and once the pedals are released, the spring force returns the pedal back to neutral.

Now let's see how pedal movement results in rudder deflection. The shaft assembly rotation is picked up by the position transducers. The transducers, in proportion to the pedal movement, send a signal to the actuator control electronics (ACE). The ACE relays the signal to the primary flight computer (PFC) for rudder movement calculation. The PFC returns the final signal to operate the rudder. The ACE sends control signals to the three rudder power control units (PCUs) in the vertical stabilizer of the aircraft. The PCUs are hydraulic actuators and use different hydraulic systems for redundancy.

The Triple Seven has a rudder tab connected to the rudder. When the PCU actuators move the rudder, the tab moves along with it. But the tab also has mechanical rod connections which deflect them further ahead of the rudder displacement. The mechanical connection is rigged to move the tab twice the distance of the rudder movement. By slipping further into the airstream, the tab increases the overall effectiveness of the rudder. Position transducers on the PCU send the rudder position to the primary flight computers. This allows the computers to control the rudder with precision.

Now let's look at the autopilot rudder control. The autopilot function is similar to the pitch command as seen in the previous elevator chapter. The autopilot computer sends a yaw command to the primary flight computer. The PFC commands the ACE to deflect the rudder to meet the autopilot demand. At the same time, the PFC commands the autopilot computer to backdrive the rudder pedals. The autopilot computer engages the backdrive actuator and runs the motor to match the rudder pedals to the current rudder position. Back-driven pedals inform the pilot of an autopilot rudder deflection. Once the autopilot command is over, the actuator clutch is released, and the pedals return to neutral.

Finally, let's see the rudder trim control. The rudder trim switch in the cockpit is used for trimming the rudder. The trim switch has to be rotated for a nose-left or a nose-right command. Let's rotate for a maximum nose-left trim. The trim switch sends a signal to the primary flight computer through the ACE. The PFC, in proportion to the trim requested, controls the rudder trim actuator connected to the feel and centering mechanism. The actuator moves the rudder pedals. The movement results in deflection of the rudder, just like manual control. The actuator will now hold the rudder in its new trim state. Pressing the trim cancel switch sends a signal to the PFC to return the rudder back to zero degrees.

Now, it's time to explore the control surfaces on the wings. For this chapter, we have selected the two roll control surfaces: the ailerons and the flaperons. Flaperons serve two purposes on the aircraft. During a roll command, the flaperons act as inboard ailerons, and during flap extension, they droop to assist the main flaps. In this chapter, we will understand the roll function. Three inputs can operate the surfaces: control wheels, the autopilot command, and the aileron trim function.

Let's start with the control wheels. Control wheels are used to give a left or right roll command. When rotated, the wheels move the control cables. The cable movement rotates the cable drums. The drums rotate the left and right shaft assemblies. The two shaft assemblies are connected, so the rotation of the wheel on one side transfers the movement to the other wheel. This ensures both pilots have an indication of aircraft roll command. Feel and centering mechanisms provide the spring force to the control wheels. The further it is rotated, the harder it gets, and once the wheels are released, the spring returns them to the neutral position.

Let's look at the aileron and flaperon deflection due to control wheel rotation. The wheel position is picked up by the position transducers and sent to the actuator control electronics (ACE). The ACE relays the signal to the primary flight computer (PFC) to calculate the movement. The PFC instructs the direction and deflection positions for all four surfaces. The ACE will now operate eight power control units (PCUs), two for each surface. PCUs are electrically controlled hydraulic actuators and use different hydraulic systems of the aircraft for redundancy. For a left roll command, the flaperon and the aileron on the left wing are deflected upwards. The command signal for the right wing surfaces is inverted, so the flaperon and the aileron on the right wing are deflected downwards. Position transducers on the PCUs indicate the surface position to the computer, allowing precise control of the control surfaces.

Moving on to the autopilot roll control. The autopilot computer gives a roll command to the primary flight computer (PFC). The PFC instructs the ACE to move the control surfaces to meet the autopilot demand. At the same time, the PFC instructs the autopilot computer to backdrive the control wheels. The autopilot computer now engages the backdrive actuators, runs the motors, and rotates the control wheel to match the control surface deflection. This gives an indication to the pilots of an autopilot roll change. Once the command is over, the actuators are disengaged, and the control wheels return to neutral.

Finally, the aileron trim function. Aileron trim measurement is different from pitch and rudder trim. During a pitch trim command, a single control surface deflects, which is the horizontal stabilizer. Therefore, it is easy for the indicator to represent one unit as one degree of horizontal stabilizer movement. Likewise, during rudder trim, the rudder is the single surface that deflects, and one trim unit indicates one degree of rudder movement. Trimming the aircraft in the roll axis will result in the movement of four control surfaces: the two flaperons and the two ailerons. They also deflect in varying degrees and opposite directions. Therefore, for simplification, the aileron trim is in proportion to the control wheel movement and not the control surfaces. One unit of aileron trim indicates five degrees of control wheel movement.

So let's trim for 20 degrees left control wheel position. When the trim switch is used, it sends a signal to the primary flight computer to rotate the control wheels. The PFC acknowledges and operates the aileron trim actuator. The control wheels are rotated until the switch is released. The wheel rotation results in flaperon and aileron deflection, just like a manual input. The trim actuator will now hold the control wheels in the trimmed state until a new trim input is given by using the switch again.

In the second part of the Triple Seven flight control series, we will understand the elevator mechanism. Before looking at the elevator, it's important to understand the control column function of the aircraft. The control column's backward and forward motion is used to control the elevator. The columns pivot on their respective torque tubes. When the pilot flying the aircraft moves the control column to change the pitch attitude, the other pilot should get an indication of the column movement. Therefore, the two columns are connected using a breakout mechanism.

The breakout mechanism ensures when one column is moved, the other moves along with it. However, if one of the control columns gets jammed, the pitch control of the aircraft will be compromised. In this situation, applying sufficient force on the other column will cause the breakout mechanism to disengage, releasing the column for free movement. After a pitch command, when released, the column must return to its neutral position. This is done by the elevator field units connected to the column torque tubes.

When the column was moved, work was done against the spring in the field units. Releasing the column causes the spring to return it to neutral. Now, let's see how the column controls the elevator. Column movement results in movement of the connecting rods of the elevator fuel unit. Position transducers measure the displacement and send an analog signal to the actuator control electronics (ACE). The ACE converts it into a digital signal and sends it to the primary flight computer (PFC).

The PFC calculates the final elevator position and informs the ACE. The ACE sends a signal to the elevator power control units (PCUs). There are four PCUs, two for each elevator, mounted on the rear spar of the horizontal stabilizer. The PCU is an electrically controlled hydraulic actuator. PCUs use different hydraulic systems of the aircraft for redundancy. The ACE signal causes the PCU actuators to move the elevator in the commanded direction. Position transducers on the PCU give the elevator position feedback. The computers, with the help of feedback signals, ensure the elevator has deflected exactly to the desired position, allowing precise control of the elevator.

When the autopilot system is engaged, it controls the pitch of the aircraft. The autopilot computer, to give a pitch command, has to send a signal to the primary flight computer (PFC). The PFC will calculate the elevator deflection for the pitch change requested by the autopilot computer and send the signal to the ACE. The rest of the function is similar to a manual command. The ACE will move the elevator PCUs as per PFC instructions. However, the PFC does one more important calculation when there is an autopilot-requested pitch change. It informs the autopilot computer to move the control columns to match the elevator deflection.

The autopilot computer controls the backdrive actuators connected to the column torque tubes. First, the computer engages the clutch on the actuator and then runs the motor, moving the control column. Moving the control column with the backdrive actuator gives an indication to the pilots whenever the autopilot system is changing the pitch of the aircraft. Once the column reaches the position to match the elevator deflection, the motors are stopped. After the pitch command is over, the autopilot disengages the actuator and the elevator fuel unit returns the column back to neutral.

When the Wright Brothers first took off in their flying machine over a century ago, they never could have imagined how ubiquitous air travel would become. Approximately 100,000 flights take off and land around the world each day, with ticket prices getting cheaper and cheaper as the industry develops.

After mankind had conquered the skies and made air travel a trivial affair, we looked towards the next frontier: space. But as engineers design new types of spacecraft, some might wonder why they go to all the trouble. After all, planes can fly pretty high. Couldn't we just fly them a little bit higher? Say...all the way into space?

Technically the answer is no, we absolutely couldn't. But why? That answer is a little bit more complicated.

Let's first look at how high planes can actually go. Commercial jets tend to fly at an altitude of around 28,000 to 35,000 feet, but they can reach heights of up to 40,000! Most of them aren't meant to go much higher than that, though there are exceptions, such as the Concorde, a supersonic commercial jet that could reach a cruising altitude of 60,000 feet. NASA also designed an airplane called Helios that was able to fly up to 97,000 feet.

Meanwhile, the minimum height required to exit the Earth’s atmosphere and enter orbital space is 62 miles or 327,360 feet. That's nearly ten times the average height most commercial jets tend to fly at.

So commercial planes and some scientific prototypes can't fly high enough to make it into space, but what's the reason for that? Why can't you just hop on a plane at LAX with a dream in your heart and soar off into the great unknown?

Well, there are a few different reasons for that. First, there are the forces that act on a plane: lift, weight, thrust, and drag. Planes are designed with these forces in mind, and they are an essential factor in a successful flight.

But in space, the gravitational force and air resistance ordinarily present are gone, and the forces required for the plane to act as intended are gone, too. Next, there is the matter of temperature. Re-entering the Earth's atmosphere generates a great deal of heat. Space shuttles are equipped with protective shielding that allows them to endure this heat without falling apart, but planes aren't quite so resilient.

Even if you were able to fly a plane into space successfully, reentering the atmosphere would roast any passengers unlucky enough to be inside. Don't pay for an economy ticket to space, folks. It's just not worth it.

Another obstacle standing between an ordinary commercial plane and space travel is the quality of air closer to space. The higher you go, the thinner the air becomes. At a high enough altitude, the air becomes too thin for the plane to maintain its lift. At this point, the plane reaches something ominously called a "Coffin Corner," in which it can no longer speed up, slow down, or climb any higher.

The only way to keep the aircraft from crashing once a Coffin Corner occurs is by reducing its altitude while carefully gaining speed during a controlled descent. And then, there's the issue of the plane's engine. Commercial airplane engines are unable to generate enough thrust to propel a craft through the atmosphere and into space, which requires approximately 7.2 million pounds of thrust.

For comparison, the Boeing 747's engine generates around 63,000 pounds of thrust. Airplane engines also rely on air in order to generate combustion. Without enough fresh air, that combustion ceases, and the engines die. Turns out the "air" part of "airplane" matters quite a bit.

This would pose a pretty big problem in space, given that it's pretty famous for being a place without much air. So what would happen if a pilot decided to try their luck and fly their plane into space anyway? Well, like the Greek myth of Icarus, in which the titular young man disobeyed his father and attempted to fly higher and higher using a pair of wax wings, only to have them melt from the heat of the sun, they would suffer a terrible fall back to Earth.

Surprisingly this has actually happened, with the most prominent example being the Pinnacle Airlines Flight 3701 in 2004. On October 14, 2004, Flight 3701 was due to transport an empty 50-seat Bombardier CRJ200 from Little Rock, Arkansas, to Minneapolis.

The planned cruising altitude for the flight was 33,000 feet, but shortly after the plane left its destination, it began to ascend rapidly. After only 14 minutes of flight, the pilots requested clearance to climb to 41,000 feet, the maximum operating altitude for the Bombardier CRJ series. They expressed to each other an eagerness to test the limits of the aircraft. Clearance was granted, and the plane quickly climbed to this ambitious new height. Once it did, however, disaster struck.

Both of the engines lost power, likely due to the sudden ascent to an altitude at the absolute limit of the craft's capabilities. The pilots declared an emergency and descended, but were unable to restart the engines. The flight crashed into the ground outside of Jefferson City, and both crew members were killed.

The National Transportation Safety Board listed the causes of the crash as, quote, “The pilots' unprofessional behavior, deviation from standard operating procedures, and poor airmanship.” Which seems a little harsh, given that they were already dead.

If the pilots’ goal was to get to space, well, let's just say they didn’t get close. Only reaching 41,000 feet, they were just over 12% of the way to escaping our atmosphere.

So, we know that airplanes can't fly into space, but there actually is a type of plane that can. That's right, you guessed it: spaceplanes. A spaceplane is a vehicle capable of flying and gliding like an aircraft while in Earth's atmosphere, and moving like a spacecraft once it's exited the atmosphere into outer space.

It's sort of the best of both worlds. There are four types of spaceplanes that have successfully launched into orbit, reentered the Earth's atmosphere, and landed safely: The U.S. Space Shuttle, the Russian Buran, the U.S. X-37, and the Chinese CSSHQ, or Reusable Experimental Spacecraft.

The Space Shuttle was a partially reusable NASA spacecraft system that was operated from 1981 to 2011. Its components included the Orbiter Vehicle, which served as the spaceplane, three rocket engines, a pair of solid rocket boosters, and an expendable external tank. The Space Shuttle launched vertically like a typical rocket. The solid rocket boosters would be jettisoned from the craft before reaching orbit, as the main engines continued powering it. Then, after the main engine cutoff and as the craft prepared to enter a steady orbit, the external tank was jettisoned as well.

When it was time for the craft to reenter the atmosphere, its thermal protection system kept it safe from high temperatures, and then it executed a runway landing as a spaceplane.

In response to the NASA Space Shuttle, the Soviet Union started the Buran program. Buran-class spacecrafts were similar to the Space Shuttle, but there were some notable differences in design. The main engines did not follow the spacecraft into orbit. Instead, small rocket engines on the body of the craft helped to propel it in orbit. It was also capable of fully automated landings and flying missions without a crew on board.

The Boeing X-37, also called the Orbital Test Vehicle, is a more modern spaceplane that was first used in 2010. It’s made up of a reusable robotic craft that is carried into space by a rocket-powered launch vehicle, where it remains in orbit to aid in exploration and research. Once it’s time for the X-37 to land, it will reenter the atmosphere and glide back to the ground as a spaceplane.

The CSSHQ is China’s answer to this new spaceplane arms race. It’s a reusable orbiting spacecraft, first launched in September 2020, that operates similarly to the other orbiting spaceplanes we’ve discussed so far. If it ain’t broke, don’t fix it.

In addition to these orbiting spaceplanes, there have been two rocket-powered aircrafts that have crossed the internationally recognized boundary into space: the X-15 and SpaceShipOne.

On July 19, 1963, American World War II Pilot, physicist, and astronaut Joseph A. Walker flew NASA's X-15 in the now-famous Flight 90. During this flight, the craft reached an altitude of 106.01 kilometers, crossing the Karman Line and entering space. While up there, the interior of the craft achieved weightlessness for between 3 and 5 minutes. As it reentered the atmosphere, some portions of the craft's exterior heated up to 650 degrees Celsius. This historic flight only lasted twelve minutes from launch to landing.

SpaceShipOne took flight many decades later, in 2004, as part of the competition for the 10 million dollar Ansari X Prize. The challenge was as simple to describe as it was difficult to achieve: be the first private organization to complete two successful piloted flights with two passengers in two weeks. Oh, and both of those flights needed to cross the boundary of space. This was achieved through several innovations working together. First, there was the launch aircraft, a hybrid rocket engine system named White Knight. This carried SpaceShipOne to a height of 47,000 feet, then dropped it. At this point, the pilot lit the craft’s hybrid rocket, sending SS1 shooting up toward its goal.

Another element of SS1 that allowed it to successfully complete its journey was the "feather" system. The feather here refers to the rear portion of SS1's wings, which would fold vertically before the craft reached its highest point. This would increase drag, slowing SS1's speed as it prepared to reenter the atmosphere. Then, the feather would be retracted, allowing the craft to glide to a smooth, safe landing. After a series of test flights, each creeping closer and closer to space, pilot Mike Melvill made history on June 21, 2004, when he passed the boundary of space by 150 meters. How did he celebrate this momentous occasion? He spent his few moments of weightlessness at the top of the world releasing chocolate into the cabin. How's that for a sweet victory?

SpaceShipOne continued to prove itself with more and more flights into space, and today, it’s prominently and proudly displayed at the Smithsonian Institution's National Air and Space Museum in Washington, DC.

In the decades since the first launch of the Space Shuttle, there have been few official developments in the world of spaceplanes capable of entering orbit. The Boeing X-37B is the only craft still frequently used today and pales in comparison to its predecessors such as the Space Shuttle. So, why aren't there more spaceplanes rocketing off into the sky?

Well, there are researchers trying to bring the reusable spaceplane back. Reaction Engines, a British aerospace company founded by three engineers following the cancellation of a British spaceplane project in 1989, intends to create Skylon, a single-stage-to-orbit spaceplane. They're also designing an engine to power it. The Synergetic Air-Breathing Rocket Engine, or "Sabre," is a hydrogen-powered engine intended to use the oxygen in the Earth's atmosphere to propel a spaceplane to hypersonic speeds before blasting off into space much in the style of a conventional rocket.

There are some pretty impressive names attached to this project, such as Rolls-Royce, Boeing, and British Aerospace. So when can we expect to see Skylon in action? In April of this year, Reaction Engines CEO Mark Thomas spoke about the project on the Aviation Xtended podcast, saying: "What's more likely is a two-stage-to-orbit system, so you'd still have a very capable and fully reusable first-stage launcher that could well operate in a horizontal take-off and landing configuration, but you'd have a more expendable, or less reusable, upper stage that did the ultimate push to orbit."

So, okay, the future of aerospace technology is cool and all, but what about the non-astronauts who want to take a spin on a spaceplane while watching old NBC sitcoms and eating potato chips in an uncomfortably stiff chair? Will spaceplane travel ever come to the regular joe consumer?

Well, as it turns out, the first commercial space flights have already happened! British business magnate Richard Branson's Virgin Galactic, a spaceflight company aiming to usher in a new era of space-based tourism, completed its first commercial flight into space on June 29, 2023. This maiden voyage aboard the rocket plane Unity included an instructor, the plane's two pilots, two Italian Air Force colonels, and an aerospace engineer from the National Research Council of Italy.

The suborbital ride lasted just 90 minutes, and as they experienced a few minutes of weightlessness at the highest point, the passengers unfolded an Italian flag in celebration. The first guests on Virgin Galactic were there as scientists just as much as tourists, one of them wearing a suit that measured his biometric data throughout the journey. Another conducted an experiment concerning the mixing properties of different liquids and solids in a low-gravity environment.

There were some concerns about the safety of the trip following the deadly crash of Virgin Galactic's SpaceShipTwo in 2014, and the disappointing results of Virgin Orbit's satellite launch, which ended abruptly when a rocket carrying the first-ever satellites to launch from British soil failed to make it to orbit. However, the flight went smoothly, and people began clamoring to be on the next trip to space. At the time of this first flight, the company had sold 800 tickets for future trips. Before you reach for your wallet, though, you should know that the price is a little steep for the average space enthusiast, clocking in at around $450,000 a seat. Sorry folks, unless you’re part of the 1%, commercial space travel is still a no go.

Okay, that's not exactly true. You could also be lucky enough to win a fundraising competition by the organization Space for Humanity, a non-profit intending to make space travel more accessible. That's what happened to Keisha Schahaff, who won a spot aboard the first Virgin Galactic flight for space tourists rather than passengers with professional experience.

Schahaff, her daughter, and former Olympian Jon Goodwin climbed aboard the Unity in August of 2023, along with the spaceplane's commander, the pilot, as well as Virgin Galactic's Chief Astronaut Instructor, Beth Moses. The Unity spaceplane was strapped to the wing of a Virgin twin-fuselage VMS Eve carrier jet, which took off from a 12,000-foot runway in the New Mexico desert at around 11 A.M. Once the carrier jet reached an altitude of approximately 45,000 feet, it released Unity, dropping it from the wing much like you might drop a bomb. But the only explosions involved in this vessel were minds being blown.

A few seconds after Unity was dropped, its hybrid rocket motor ignited to propel the craft upward and out of the lower atmosphere. Its velocity steadily increased until it was around three times the speed of sound, and then the rocket motor shut down, suspending the crew and passengers in a few minutes of weightlessness. It continued to climb upward until it reached its maximum altitude of 54.9 miles. During the descent, while still weightless, the passengers were able to remove their straps and float freely through the cabin. Then, once everyone was safely back in place, Unity feathered its wings, increasing drag to slow its descent, and began to make its way back to Earth. Once back in the atmosphere, it rotated its wings back into their original place and glided back onto the runway.

As impressive as the experience onboard a Virgin Galactic spaceplane might be, the voyage is strictly suborbital. Is there any hope for a commercial spaceplane that actually enters orbit like the Space Shuttle? Sierra Space is developing one, the Dream Chaser, a winged commercial spaceplane ideal for transporting cargo or even human passengers. Eventually, it could carry up to seven people, as well as cargo, back and forth from a point in low Earth orbit.

The cargo version of the Dream Chaser is intended to resupply the International Space Station, as well as transport cargo back to Earth from the ISS if necessary. For now, this version is being prioritized over the passenger-friendly version.

But they're not stopping there. Sierra Space is aiming even higher than a winged spaceplane capable of transporting people to the ISS. They're also developing the LIFE habitat. Not the cereal, or the board game, but the Large Integrated Flexible Environment habitat, a structure that launches via a rocket and, once in orbit, inflates to a height of three stories and a diameter of 27 feet. It'll likely be a while before it's ready, but the plans for this mobile habitat and workspace are ambitious.

As the Sierra Space website puts it, "Remote work will never be the same." They're promising three floors of living and working area, able to accommodate crews of between 4 and 12 people, life support systems that regulate the air pressure, humidity, temperature, and oxygen levels, a multi-layer shield able to withstand the harsh conditions of space, and an Astro Garden able to grow fresh plants and produce. That's quite a lot to accomplish, but they've already built a ground prototype, so who knows? Maybe sometime soon, working from home will expand to include "working from space."

This is as far as current technology will allow us to go when it comes to planes that can carry passengers into space. But here's another question: once you've hopped on that spaceplane, where are you taking it? What's the destination? Sure, maybe it's just "space, in general," but why stop there? Once we've taken planes into space, why not bring other aspects of flying along, too? Such as the airport itself, with its various shops, eateries, and the oh-so-exclusive airport lounge? They're working on that, too. Enter the Orbital Reef. Well, you can't enter it because it doesn't exist yet. But it's intended to be a "Mixed-Use Business Park in Space," and "The First Commercially Owned and Operated Space Station," a station in low Earth orbit centered around commerce, research, and space tourism.

The Orbital Reef promises to include the LIFE habitat as well as the Dream Chaser spaceplane in its operations. It also promises a variety of uses and experiences, from business, to a spacious research laboratory for physical, biological, or Earth science as well as product development, to pure tourism and curiosity about the experience of space. They intend for the Orbital Reef to be made a reality by the decade. It sounds like something out of a science fiction story, but in August 2022, Orbital Reef's plans passed a System Design Review by NASA.

This review, which was conducted from mid-June to mid-July, served to confirm that the concept for the Orbital Reef met the requirements to function as intended. Orbital Reef wasn't the only space station concept to pass this review. Starlab station, a continuously crewed commercial space station being built by Voyager, passed the review, as well as another commercial space station concept from Northrop Grumman Corporation. Another company, Axiom Space, reached an agreement with NASA to add commercial modules to the International Space Station itself. These will later be formed into a commercial space station if all goes according to plan.

It all seems promising, but the talks of transitioning to commercial space stations by the close of the decade have not been met with only support. NASA's safety advisors and inspector general have criticized the short timeline, warning that these commercial stations might not be ready by the planned deadline. However, representatives from both NASA and the four companies involved in developing these stations disagree with these concerns. They are all making great progress, according to them, and Orbital Reef plans to launch its first modules in 2027.

So, while you can’t fly a commercial jet into space, and most people won't be able to snag a seat on a spaceplane either, as we develop better and better methods of space travel, it’s entirely possible that a future is coming where ordinary people will be able to purchase a business class ticket to the stars.

Pressure is one of the most important aspects of the atmosphere. Actually, if all you knew, if all the data you had was say like pressure and temperature and maybe wind speed, you could still say a lot about what the weather was going to be like wherever you were. This is because pressure is such a huge driver for atmospheric motion.

I think one of the most intuitive ways to think about atmospheric pressure is to think of it as the weight of the air above you. So, if this is the Earth and this is the atmosphere and this is Timmy, and this is the air above Timmy, then the atmospheric pressure on Timmy right now is five, because I drew five dots. But if Timmy were to get up and climb a ladder then when he's higher up the pressure on Timmy here would only be two. There's less air above him so the pressure has gone down.

This silly little picture gives us a pretty intuitive understanding of why pressure decreases with height. The higher up you go, the less air there is above you, the less weight there is pressing down on your head.

For atmospheric stuff, we're going to measure pressure in either hecto-Pascal or millibar. Hecto-Pascal is written "h" "P" "a", millibar is "m" "b". They're actually about the same, and in either unit, surface pressure is about 1000 millibars or hecto-Pascal.

At the beginning of this video, I told ya'll that if all you knew about your location was the surface pressure and the temperature you could still say a lot about the weather. Well, that's because low surface pressure is generally associated with stormy weather and rain whereas high surface pressure is generally associated with sunny, clear skies.

Let's take a brief look at why that is and how pressure drives atmospheric motion. This blob I just drew? Think of it as like - it's a, it's a container that filled with a liquid. Honestly? I think of it as like a waterbed. Right now, as I've drawn it, the pressure on the surface of this water bed is pretty constant. The pressure there is about the same as it is over here.

But what would happen if I came in and I pressed down really hard on this side? So we're going to make this a region of high surface pressure. So you could imagine that this surface would sort of dip down, but then the rest of it has to go somewhere. The water that was there has to go somewhere. We would expect it to pop up over here.

So then this green line would be our new surface of our water bed. Ah! I broke my chalk. Notice that over here, we actually have moved up. So now, we would say that the pressure over here is higher than the pressure over here, so I have a low pressure, low surface pressure over here and in general, we had water move from high to low.

This is the same fundamental principle that happens in the atmosphere. We get, say, high pressure at one region for one reason or another and then that causes air on the surface to move away from that high-pressure region. We'll end up at a low-pressure region and eventually we'll start to have rising air.

One of the things we're going to talk a lot about in this series is how rising air is related to, like, clouds and storms and things like that. So, just by these variations in pressure, we get a lot of motion of the atmosphere, right, we're going to move from high to low pressure, and even going to cause air to start to move up, get that rising motion in the atmosphere.

One thing to keep in mind is that high surface pressure is associated with air going down, um, and low surface pressure is associated with air going up. So we have sinking motion over regions of high pressure and rising motion over regions of low pressure.

That pretty much covers the very basics of atmospheric pressure. It's a topic we're going to talk about a whole lot in this series. So don't worry there is more to come. More atmospheric pressure to come for all of ya'll. But for now, I think that gives you a good intuitive understanding of how pressure relates to like, air movement.

The idea here is that if you have a gas that's made up of a bunch of other gases, then you could break down the total pressure being exerted by that gas into what's being exerted by each individual part. If this box is just sort of we've captured normal atmosphere in a box, then we would expect our Nitrogen to be 78% of what's in there, Oxygen 21% and then we know that last 1% remaining - 1%? Yeah - 1% remaining would be everything else.

So just to make our lives simple let's just think of that everything else as just the water vapor. It'd be really really easy to think that, "Okay, great! If Nitrogen is 78% of what's inside here, 78% of the atoms in this box are Nitrogen, diatomic Nitrogen, then shouldn't 78% of the pressure be coming from the Nitrogen?" But that's - we've got to be a little wary because that's a little too simple because what we forgot to take into account there was that Nitrogen and Oxygen and water vapor all have different masses.

So in diatomic oxygen, there's going to be, it's two oxygen atoms bound together, um, and so each of those is going to have like 32 neutrons and protons. It also has electrons, but electrons weigh very little compared to neutrons and protons. So for right this second let's just think about the weight as related to the number of things in the nucleus.

Diatomic Nitrogen, well Nitrogen has seven neutrons, seven protons, so diatomic Nitrogen would only have 28. So even though I have more Nitrogen than I have Oxygen, each Oxygen atom weighs more than each Nitrogen atom. So if I broke down the partial pressures, it's not going to be 78% of the pressure comes from the Nitrogen and 21% comes from Oxygen. A little more of the weight of this air is coming from the Oxygen than like the percentages.

Hope that makes sense. But anyway. The basic idea here is that if we know the partial pressure of each of our different atoms, right? Each of our different molecules. Then if we add all those pressures up we should get the total pressure.

So, in a quick formula, that looks like this: The total pressure is going to equal the pressure from the Nitrogen plus the pressure from the Oxygen, plus the pressure from the water vapor. I bet right now you're thinking to yourself, "Well that's all well and good, Maddie. But why in the world would we ever need to know the difference in pressure from Nitrogen and Oxygen?" And that is a totally fair question.

Because in reality, Nitrogen and Oxygen partial pressures aren't going to really change our chemistry or what's going on in the atmosphere very much. But what is really important is that water vapor. So, usually? When we're thinking about partial pressures in the atmosphere, we're not going to think about each individual component. We're going to think about the pressure from the dry air and the pressure from the water vapor.

The total pressure is the partial pressure from dry air plus the partial pressure of water vapor. I still haven't quite gotten to why this is a thing we would want to do. And for now, let's just think about how tricky and ill-behaved water vapor really is.

Because water in the atmosphere can be in its gaseous phase, in a liquid phase, or in a solid phase. Right? We can have clouds, so liquid water suspended up in the air, those clouds could also be made of ice particles instead of just liquid water. We could be making precipitation. Right? We could be condensing dew on the surface. So water vapor has this nasty habit of changing phase, left right and center, doing crazy stuff to like our atmospheric chemistry or what's going on in our atmosphere.

The phase of water is actually also really important for some temperature effects that we're going to get to in a few videos down the line. Since the phase of water is a function of both temperature and pressure, understanding how the pressure of water vapor is going to change can be something that's pretty important.

Dear friends and followers, welcome back to my channel. Today we'll be looking at this picture in more detail. Why do airplanes have a split rudder and others don't have this unique feature? And, an incident with this rudder system. I'll show you which plane has the "coolest" split rudder of all! So, let's get started!

Remember the last time you sat at the gate and an Airbus A380 or a Boeing 747 taxied by and you spotted this. What you see here is the so-called split rudder and obviously there is a reason why it is split in two.

But before we look at the rudder, we have to get a better understanding of the hydraulic layout of planes, in particular, the Boeing 747. The primary flight controls such as the ailerons, elevator, and rudder are hydraulically powered.

In the case of the Boeing 747, which has 4 independent hydraulic systems 1, 2, 3, and 4 are each powered and pressurized by its respective engine. If we look at this schematic, you see that the tail fin rudder or the vertical stabilizer is split into the upper and lower rudder. The upper rudder is deflected to either side by three actuators, two of them are powered by hydraulic system number 3, and one by system number 1.

The lower rudder comes with two actuators, one powered by system number 2, and the other by system number 4. As you apply force into the rudder pedals to either side, both the upper and lower rudder will deflect simultaneously towards the given input.

I'm sure many of you have steered a little boat before and you might remember as you were maneuvering the boat into a harbor or more in position, you need a lot of rudder deflection to actually steer the boat. Because the inputs are less effective due to the low speed, similar physics apply to airplanes. The slower you fly, the more deflection you need on the rudder to have an effect, and the faster you fly, the less deflection you need.

For example, as she comes in for landing if the pilots apply full left or right rudder, it will go to the maximum deflection of 31.5 degrees, which sometimes can be necessary in strong crosswind conditions. During cruise or speeds beyond 350 knots, with the same amount of input into the pedals, the rudder will only deflect 7.6 degrees or less to either side.

As an airline pilot, you always expect the same reply of your plane, no matter the speed, and therefore airplane engineers have fitted the flight control system with a so-called "Rudder Ratio Changer." The general purpose of the "Rudder Ratio Changer" is to gradually reduce the surface deflection of the rudder by the pedals with increasing airspeed.

Please do not mistake this with the yaw damper, that's a whole other system and video. But to be fair, you barely use the rudder during cruise flight except in non-normal situations like engine failures, etc. In case you need to center the slip skid indicator which shows if your plane is yawing to either side, for instance due to unbalanced loading, you can use the rudder trim to even out the yaw, which saves power and fuel.

If we quickly take a look at the Airbus A380, she has a very similar system. But one thing I can't really wrap my head around is why the Airbus A380 rudder sometimes points in either direction when being parked at the gate position. I did a whole video on that subject as the rudder is being deflected by the wind. But how can the A380 lower rudder point to the left and the upper rudder point to the right? It makes no sense to me. Please comment below if you know the answer to that question.

But that still doesn't answer the question of why they are split in the first place. Let's say hydraulic system number 1 would fail for some reason. Not yet to worry about the rudder as we still have system number 3 powering the two other actuators. Now let's say the situation is becoming even worse and system number 3 fails also. Trust me, if that were to happen, you are really having a bad day as all hydraulic systems also have a backup feature, so it is very unlikely. But let's imagine the worst-case scenario.

Meaning you have now lost complete control over the upper rudder. If it weren't for the split rudder, hydraulic system 2 and 4 backing up the lower rudder, you would have no more rudder authority which would make your landing very hazardous in case you've had engine failures leading to the hydraulic system losses, for example.

So, you see the primary reason for the split rudder as ever so often is redundancy, and the rudder isn't the only flight control which has a backup. The horizontal stabilizer comes also with inboard and outboard elevators, so technically they are also split and so are the inboard and outboard ailerons.

Redundancy is key, especially in terms of flight controls. But also, the split rudders provide a finer high-speed control and that only the lower one moves at high speed, reducing the exposed surface area and therefore the control effects as there is a structural benefit. By only using the lower rudder when the aircraft is at high speed, it reduces the twisting moment and transfers the load to a bigger, stronger part of the airframe, and that's the principle behind why the outboard ailerons are disabled at high speed.

The chances of multiple hydraulic system failures are very rare. Nevertheless, there was an incident in 2002 on a Boeing 747-400, which experienced a so-called lower rudder hardover event. The lower rudder suddenly went into the maximum deflection to the left, causing the plane to abruptly bank 30 to 40 degrees to the left.

The pilots acted fast and applied full right rudder. Unfortunately, that was still not enough to prevent the plane from losing altitude, yawing, and rolling to the left. So the right aileron was also needed. Due to the limited controllability, the pilots immediately declared an emergency and landed at the next suitable airport, which FYI was two hours away.

For two hours, the pilots were fighting with extreme forces on the control column and with decreasing speed, the rudder authority of the slightly smaller upper rudder was not enough to fly the plane in a straight line. The pilots then used differential thrust to counteract the yawing moment on approach.

The plane safely landed, and later investigation showed that the lower rudder control module had a broken housing due to metal fatigue causing the hardover. For more details, read the NTSB report on Northwest Flight 85.

Now you question: What about smaller jet airliners such as the Airbus A320 or the Boeing 737 which do not have a split rudder? On the Airbus A320, she has a 3 hydraulic system. The rudder is moved by 3 actuators each individually powered, and as a backup, you have the hydraulic power transfer unit as a 2nd backup, the ram air turbine, and as a 3rd, the mechanical connection. So the necessary redundancy is given, but please may Boeing 737 pilots comment below on how their rudder redundancy is given or just ask DutchPilotGirl.

The most unique split rudder you can find is on the B-2 bomber. As she has no vertical stabilizer/rudder, she still needs to be controllable along the yaw axis. The engineers placed these panels far out on her wing. They look like ailerons, which they are not as the secret is on the lower side. Another panel on the lower side deflects downwards as the top one goes upwards, creating the necessary drag, forcing the plane to yaw to either side, making it the most unique split rudder for yaw control. The panels you see here are the so-called elevons for roll control of the plane. That is so clever.

If you now want to know why the rudder very often points to the right or left whilst the plane is parked at the gate, click onto the video link which will pop up here in a few seconds. Also, check out my new t-shirt designs just above the description box. If you are a Boeing or Airbus lover, you definitely want to get one of my new shirts.

Have you ever noticed how it's often foggy around Bonfire Night? There's actually a good reason for that.

Yes, it's the depths of autumn, and autumn is often associated with fog. But Guy Fawkes Night actually provides an extra reason why the atmosphere may create fog.

Fog is just cloud that's on the surface. Like cloud, it's made up of millions upon millions of tiny water droplets. Water is always present in the air around us, but most of the time, you can't see it because it's in vapor form.

As air cools, like it does during the long autumn nights, the water cools and condenses. It changes from water vapor that you can't see into millions of tiny water droplets that you can.

But here's the key: for that change to happen, for the water to condense, it requires something else. It requires tiny little particles to be in the atmosphere. These are called condensation nuclei, and without these, the water just wouldn't change from its invisible form into its tiny droplet form.

Condensation nuclei is just a fancy name for bits of stuff in the atmosphere, like dust and smoke. The more of these condensation nuclei there are, the more likely it is that fog will form.

So yes, you guessed it. On Bonfire Night, bonfires and fireworks create more of these tiny particles, and so fog is more likely on Bonfire Night and on the morning of the 5th of November in New Zealand.

In this video, we're going to do a quick overview of the Magneto. The magneto is part of the ignition system. Basically, the magneto supplies a high voltage to the spark plugs for ignition.

Let's take a closer look and see how the magneto actually works.

So here we have a Magneto. Let's break it down. Let's start with the rotor. The rotor is a permanent magnet, and it rotates. It is rotated by an engine drive gear.

Next, we have the coil assembly. Let's take it apart to see what it's made up of.

Okay, so in the middle we have an iron core. Next, we have the primary coil, which is around 200 turns of heavy copper wire. Then, we have the secondary coil, which is a 100 times step-up, around 20,000 turns of fine copper wire.

Some important connections that the coil assembly has are first, a hot wire leaving from the primary coil going to ground. Also, there's a high voltage tab that leaves from the secondary coil going to the spark plugs.

When the rotor permanent magnet rotates, it induces a continuously changing flowing current in the primary coil, which creates a powerful magnetic field in the iron core. This magnetic field expands outwards, encircling the entire coil assembly.

When ignition is required, the grounding of the hot wire leaving the primary coil is disconnected. The flow of current is stopped, and this causes the magnetic field to collapse suddenly, cutting across the secondary coil. This induces a huge voltage spike in the secondary coil of around 20,000 to 30,000 volts.

This huge voltage spike leaves the secondary coil through the high voltage tab and goes to the spark plug, where the high voltage drives current across the gap in the spark plug, creating the spark required for ignition.

Now, let's cover a couple of select details before I wrap things up.

First detail: the disconnecting of ground on the hot wire from the primary coil is accomplished through breaker points. The contacts are opened, disconnecting the ground connection, which leads to the voltage spike in the coil assembly.

The last detail: there is more than one spark plug to consider. Well, this is where the distributor comes in. The distributor directs the high voltage to the spark plugs in proper sequence.

A cool thing to observe is that the magneto is its own little electrical powerhouse. The magnet in the magneto rotates off engine power. The magneto itself is completely independent of the alternator and battery in the airplane. So, if you have an aircraft electrical failure, the magneto won't be affected, and the engine will continue to run.

Turbulent weather can lead to passenger discomfort and, in extreme situations, can jeopardize the safety of the flight. To avoid flying into turbulence, the navigation systems must constantly provide information about the weather conditions ahead of the aircraft. To achieve this, the aircraft is equipped with a weather radar system.

The system has a high directional flat plate antenna in the radome of the aircraft and two weather radar computers in the avionics compartment. The computers are connected to the antenna with the help of waveguides. The weather computer controls the antenna using motors to perform an auto scan. The antenna can scan 80 degrees vertically and 180 degrees horizontally.

The weather radar system works on the echo principle. The selected weather computer generates high-frequency radio pulses in the range of 4 to 6 gigahertz and transfers them to the antenna through the waveguide. The antenna converts it into a narrow beam and transmits them ahead of the aircraft. The aircraft radome is made of special composite material which causes minimum interference to radio wave propagation.

Let's see how the system detects, calculates, and displays all possible weather conditions the aircraft can encounter. The radio pulses transmitted get scattered by the precipitation in the clouds. Some of them are scattered back towards the antenna. The weather computer tracks the direction of the returning pulses by using the antenna position data. Then it calculates the range by using a simple formula: c is the speed of radio wave propagation, which is the same as the speed of light, t is the elapsed time between transmission and reception, and dividing by two since the pulses have traveled twice the distance.

Finally, the computer measures the intensity of the radio pulse return. The higher the precipitation in the clouds, the more will be the echo of radio pulses. This means radio pulses hitting dense stormy clouds will have more returns compared to light weather clouds. The weather computer, now knowing the direction of the return, the distance from the clouds, and the intensity, maps out the weather condition ahead of the aircraft on the navigation displays.

Different colors signify different weather conditions, which are directly proportional to the intensity of the return. Green indicates light weather, yellow for medium, red signifies heavy conditions, and magenta for turbulence. The weather system provides information on turbulent weather conditions up to 40 nautical miles. With the help of the weather radar system, aircraft can be navigated to avoid turbulence, ensuring comfortable and safe flights.

Today we're going to be talking about stability and what makes an airplane stable. Stability is the ability of an aircraft to correct for disturbances in its equilibrium and to return to its original flight path. For example, if you're flying your airplane and it's pushed up by turbulence, a stable airplane would have a tendency to pitch back down to its original flight path.

Most airplanes, especially training aircraft, are designed with stability in mind. Some aircraft, however, like fighters, are designed to be less stable so they can be more maneuverable. When it comes to stability, all three axes are considered. Do you remember what those are from the last lesson? Let's talk about two types of stability that affect our three axes: static and dynamic.

Static stability is the initial tendency of the aircraft after the equilibrium is disturbed. In other words, what's your airplane's immediate reaction after you make a control input or one of the three axes are changed by some outside force? Let's say, for example, you pitch your airplane up five degrees. What's the initial tendency of your airplane? If it's to pitch back down to its original attitude, this would be known as positive static stability. On the other hand, if you pitch your airplane up and it continues in that same attitude, this would be known as neutral static stability. But what if we were to pitch up to 5 degrees and the aircraft continued to pitch beyond that 5 degrees? This would be known as negative static stability. For most aircraft, this is undesirable.

Now let's talk about dynamic stability. This is an airplane's response to an upset in the equilibrium over time. Let's say you pitch the nose of your airplane up again. Initially, it may pitch below the initial pitch attitude you had before, but over time these oscillations decrease. This would be known as positive dynamic stability. If these oscillations stayed the same over time, we would call this neutral dynamic stability. These oscillations could even get worse; we would call this negative dynamic stability.

Now that you understand the different types of stability, let's talk about some of the design features that make an aircraft more stable. First, let's talk about how we get longitudinal stability on the lateral axis of our airplane. Most airplanes are designed so that the center of gravity is in front of the center of lift or the center of pressure. This intentionally makes our aircraft nose-heavy, and there's a special feature to help balance it out. The horizontal stabilizer on the tail of the airplane is designed with a slightly negative angle of attack, so it exerts a downward pressure. This downward pressure balances the airplane at the optimum cruising speed.

If our airplane slows down below that optimum cruising speed, our horizontal stabilizer, which is basically an upside-down wing, won't create enough downward pressure to balance the aircraft. This will allow the nose to pitch down. When the nose of the aircraft pitches down, it'll also gain speed. With more speed, our upside-down wing creates more downward pressure, and that downward pressure will pitch the nose of our aircraft back up. And now you can kind of see a cycle developing or an oscillation. This is where we get our dynamic stability.

Let's talk about lateral stability on the longitudinal axis for just a minute. There are several different ways we can get lateral stability, but today we're only going to talk about two: dihedral and keel effect. Some airplanes are designed so that the outer tip of the wing is higher than the wing root. We call this dihedral. Let's say your airplane rolls to the left because some turbulence hit the right wing from the bottom. When this happens, the airplane will enter a side slip. This just means that the left wing yaws slightly in front of the right wing. When relative wind hits our wings, the wing in the front has a higher angle of attack. With a higher angle of attack, that will produce more lift, which will roll us back to level flight.

Keel effect is something that affects high-wing aircraft. For these, anytime the airplane rolls, the weight of the aircraft will simply act as a pendulum and swing it back to level flight.

The last thing we'll talk about today is directional stability and how it affects the yaw axis. We achieve directional stability by the weather vane effect. This is achieved by putting a vertical fin on the tail of the aircraft. Anytime the vertical fin is not aligned with the relative wind, the relative wind will push the tail back until it aligns itself, much like a weather vane.

The 777 was the first Boeing aircraft to incorporate the fly-by-wire system. A well-designed automatic flight control system that improves performance and safety combined with pilots having the ultimate authority in all situations of the flight has made the aircraft one of the best to fly.

In our triple seven flight control series, we will understand how the control surfaces function. Let's start with the horizontal stabilizer.

The horizontal stabilizer is used to trim the pitch of the aircraft and behaves differently in flight in comparison to ground operation. To best understand its architecture, let's operate them on the ground and the flight operations will be covered in the subsequent elevator chapter.

At the heart of the aircraft flight control system are the three primary flight computers. All control surface commands, whether from the pilots or the autopilot computers, have to go through the PFCs. To help the PFCs, there are four converters called the actuator control electronics. Multiple computers offer redundancy and accuracy. Let's keep one computer of each system for simplification.

The stabilizer trim switches are on the control columns. The switch in the up position gives aircraft nose down signal, and in the opposite direction gives a nose-up signal. The switch electrical signal goes to the actuator control electronics. The ACE converts the analog signal into digital and sends it to the PFC. In flight, the PFC takes several factors into consideration before calculating the speed of stabilizer movement. But since the aircraft is on the ground, the PFC allows the stabilizer to move at maximum speed.

The final calculated signal is sent back to the ACE. The ACE now converts the digital signal to analog and sends it to the two stabilizer trim control modules. The trim modules control the hydraulic power to the stabilizer actuator with the help of solenoid valves. Of the three hydraulic systems in the aircraft, one trim module uses the center system and the other uses the right system.

The signal from the ACE opens the nose-up solenoid valve of the module, and hydraulic pressure is now sent to release the brakes on the ball screw actuator assembly. Simultaneously, hydraulic pressure from the modules runs the two hydraulic motors. The motors, with the help of differential gears, turn the ball screw to which the stabilizer is connected. The leading edge of the stabilizer moves down to give the aircraft a nose-up attitude. Stabilizer position indication is given in the cockpit with the help of position transducers.

Once the stab trim switch is released, the trim module is directed to stop the stabilizer movement. The module stops the hydraulic motors and re-engages the hydraulic brakes. The brakes prevent inadvertent movement of the stabilizer when not commanded.

The aircraft also has an alternate pitch trim lever for manual control. The lever, through mechanical cables, is connected to the manual valves on the trim modules. Let's move the lever for a nose-down command. Cable movement causes the control rods to move the manual valve cranks. The trim modules now release their respective brakes and run the hydraulic motors. The direction of motor rotation depends on the direction of crank movement.

As the stabilizer moves to the nose-down trim, releasing the trim lever causes it to return to the neutral position. This closes the manual valves and the trim modules execute the stop procedure.

The troposphere is the layer that's in contact with Earth's surface where we live and climb mountains and fly in planes. Everything we do unless you're an astronaut or a very specialized type of pilot is going to be in the troposphere.

Above the troposphere is the stratosphere, then the mesosphere, and then finally the thermosphere. And I do want to make a point to say that there is not some distinct line up here that's like this is the thermosphere and this is our atmosphere and then this is space. It's not a hard boundary. It's very much a gradient and the thermosphere just sort of dissolves into space eventually.

Chemically, the atmosphere is made up of 70% Nitrogen, 21% Oxygen, like 0.93% Argon, and then after that you've got water vapor, and carbon dioxide, and methane and "NOx" and all of the other trace gases.

But of all of those trace gases, water vapor is going to vary the most. It can be up to like 5% of the atmosphere's makeup if you're over like the equator or a jungle or the ocean or something like that and it can get just almost nothing over say a desert region.

And that is in a nutshell what the atmosphere is made of.

In this video, we will be looking at what is the Instrument Landing System and why is it useful for an aircraft.

What is an Instrument Landing System? An Instrument Landing System or ILS is a precision runway approach navigation system which provides guidance to aircraft during approach and landing. The ILS is a short-range guidance system which is used by aircraft to land safely on the runway, especially in bad weather or in low visibility conditions.

Let's look at how an ILS works.

How does an ILS work? An ILS provides horizontal and vertical guidance information to an aircraft for approaching a runway. The horizontal guidance information is used to guide an aircraft towards the center line of the runway. The vertical guidance information is used to allow an aircraft to descend smoothly towards the runway. Horizontal guidance is provided by a localizer and the vertical guidance is provided by a glide slope. In addition to the localizer and the glide slope, marker beacons and runway lights may be included as a need to the Instrument Landing System.

Let's look at the horizontal and vertical guidance information in more detail.

The Horizontal Guidance: The horizontal guidance or localizer guides an aircraft to track the center line of the runway. The localizer aerial is located at the end of the runway. It transmits two intersecting beams, one towards the left and the other towards the right of the runway. The beams intersect exactly over the center line of the runway. Depending on the location of the aircraft, there are different indications given in the cockpit. These indications are used to fly towards the right or towards the left to reach the center line of the runway.

The Vertical Guidance: The vertical guidance or glide slope is used to allow the aircraft to descend smoothly towards the runway. The glide slope antenna also transmits two intersecting beams, one beam above the required descent trajectory and the other beam below the required trajectory. Where the beams intersect represents the optimum path for descending towards the runway. So depending on the location of the aircraft, indications are provided in the cockpit to descend or to climb towards the required descent path and maintain this path.

Localizer and Glide Slope: By combining the signals from the localizer and the glide slope, the aircraft can descend safely towards the center line of the runway. These signals are undisturbed by the weather conditions or the time of day, which makes it very useful for an aircraft to descend and land safely in any condition. On modern aircraft having the autopilot system, the aircraft will automatically use the localizer and glide slope signals to approach a runway.

Additions to the ILS: The localizer and the glide slope are the primary requirements for an ILS. Marker beacons may be installed at specific distances along the approach path towards the runway. The outer marker beacon would be at five nautical miles from touchdown and the middle marker would be one nautical mile from touchdown. Nowadays, instead of marker beacons, Distance Measuring Equipment or DME may be installed to provide distance information. High intensity runway lights may also be used to improve the visibility of the runway in all operating conditions. Normally, even if the ILS signals are captured and followed, a certain amount of visibility of the runway should be available in order to continue with the approach and land on the runway. The runway lighting system improves the visibility of the runway.

The Instrument Landing System with localizer and glide slope signals is called a precision approach system. So that's all for my video on the ILS.

In this Video we will understand how the leading edge devices on the wings work. The aircraft has 14 slats, 12 outboard and two inboard. Slats cannot be installed between the engine pylons and the inboard slats as their movement will be obstructed by the engine cowlings. Therefore, two Krueger flaps are installed to assist the slats. The slats are fly-by-wire controlled with three modes of operation: the flap lever is used to select the three available slat positions: up, sealed, and gapped.

Let's put the slats to the sealed position. When the flap lever is selected to 1, the position change signal is sent to the flap/slat electronics unit. The computer first engages the primary mode for slat control, then it sends a signal to the slat hydraulic valve. The center hydraulic system of the aircraft is used to operate the slats. The valve opens to run the hydraulic motor, which drives the slat power drive unit gearbox. Connected to the gearbox are the torque tubes. Angle gearboxes help route the torque tubes to the right wing.

Now let's see how the torque tube rotation results in slat extension. Offset gearbox uses the torque tube rotation to drive a rotary actuator. The actuator rotates the slat pinion gear. There are two gear connections for each slat. The gears extend the slat to the sealed position with the help of tracks. The Krueger flap has two positions: retracted or fully extended, and instead of gears and tracks, uses a pushrod connection. Just like the inboard slats, the outboard slats extend with the help of gears and tracks.

Position sensors on the offset gearbox measure the torque tube rotation and send the signal to the flap/slat computer. This allows the computer to determine the slat position and control them with precision. Flap lever position 5, 15, and 20 controls the trailing edge flaps. The slats remain in the sealed position. Changing the lever position from 20 to 25 results in both the flap and slat movement, but they will not extend simultaneously. The computer will follow a sequence: first, it will command the slat power drive unit and move the slats to the gapped position. After slats extend, the flaps are moved to 25. Flaps 30 will move the trailing edge flap to its maximum extension.

Now let's look at the retraction sequence. First, the flaps retract to 20. Next, the slats are commanded to the sealed position. If the hydraulic components fail during a slat command, the computer will automatically switch to the secondary mode. In secondary mode, signal is sent to the electric motor to operate the power drive unit. The torque tubes are driven in the opposite direction and the slats retract to the sealed position. Next step in the sequence, the computer retracts the flaps up. Finally, the slats are moved to the retracted position.

If the computer malfunctions, the flaps and slats can be controlled using the alternate mode. Arming the system will disengage the current mode and prevent the computer from controlling the flaps and slats. Let's extend the slats in alternate mode. The switch directly sends a signal to the electric motor to run. Since the computer has been bypassed, there will be no sequencing. The slats and flaps will extend simultaneously in the alternate mode. The slats can only be extended to the sealed position and flaps to maximum 20.

As we have covered all the flight control surfaces, in our next part of the series we will understand their function in flight.

Today we're working on how an airplane creates lift. As pilots, it's really important for us to know how an airplane uses relative winds and the shape of its wings in order to create lift. If you remember from lesson one, lift is that upward force that opposes weight. So how does the airplane create lift? It does it by using Bernoulli's principle. Let's take a closer look. Bernoulli's principle states that as the velocity of a moving fluid increases, the pressure within that fluid decreases. Narrow areas like this, which are often called a Venturi, force the fluid to increase its speed. And with that increase in speed, we get a decrease in pressure. Just like in a Venturi, the curved surface of the upper wing forces the air on top of the wing to travel more quickly than the air on the bottom of the wing. This forces an area of lower pressure on the upper surface of the wing.

So, what happens if there's lower pressure on the upper surface of the wing and higher pressure on the bottom surface of the wing? You get an upward force, and that upward force is known as lift.

In this video, we will be looking at what is a VOR, the operation of a VOR, how the VOR information is presented in an aircraft, and its uses. What is a VOR? VOR stands for VHF Omnidirectional Range. A VOR is a short-range navigational aid which has been in use since 1960. The VOR can be used during the day or during the night. The VOR may be paired with a DME, which will provide the range and the bearing information for an aircraft.

How does the VOR function? The VOR produces 360 radials at one-degree spacing. These radials are aligned to the magnetic north at the VOR location. The VOR transmits two signals: one signal is the reference signal which is frequency modulated, the other signal is a directional signal which is amplitude modulated. The directional signal will have a phase difference with the reference signal depending on the radial. Let's understand this with a few examples: if an aircraft is north of the VOR transmitter, then it is at the zero-degree radial. The phase difference between the reference signal and the directional signal will be 0 degrees. If the aircraft is east of the VOR, then it is at the 90-degree radial, the phase difference between the reference signal and the directional signal will be 90 degrees. Similarly, if the aircraft is south or west of the VOR, the radials will be 180 and 270 degrees. The phase difference between the signals will be 180 and 270 degrees. So the phase difference between the reference signal and the directional signal will be the same as the corresponding radial. The VOR transmits 360 radials, each at a spacing of 1 degree, so the phase difference will also vary accordingly.

But if we consider an aircraft at a particular radial, let's say 170, how will the aircraft know whether it is flying towards or away from that VOR? To understand this, let's look at how the VOR information is presented in the cockpit. The VOR information is presented on an instrument known as the coarse deviation indicator. To know whether an aircraft is flying towards or away from a VOR, a "To" or a "From" flag will appear on this indicator. "To" means the aircraft is flying towards the VOR, "From" means the aircraft is flying away from the VOR.

Let's look at some other indications and the function of this knob on this instrument. Once a particular VOR frequency is tuned on the navigation radio, the knob is used to select a particular bearing or radial. This knob is called the Omni Bearing Selector. The selected bearing will be shown on the instrument. Depending on the position of the needle, the aircraft may need to fly towards the right or towards the left. If the needle is towards the right, the aircraft has to fly towards the right. If the needle is towards the left, the aircraft has to fly towards the left to capture the selected bearing.

What are the factors that affect the VOR transmission? Since the VOR transmits in the VHF band, it operates in the line-of-sight range. The transmitter power has a direct impact on the range of VOR signals. The terrain around the VOR will also have an impact on the transmission. What is the cone of ambiguity? When flying towards a VOR, the radials will converge, which means the course deviation indicator will become inaccurate. The needle will oscillate rapidly, and an "off" flag may appear for some time. After crossing this cone, the "front" flag will appear and the needle will become steady.

How to identify a VOR? VORs can be identified by three-letter codes which are transmitted by that specific VOR. These signals are transmitted along with the reference signal. A monitoring system at the VOR transmitter location will continuously monitor the identifier signal, the navigation signals, the signal strength, and the status of the monitoring system itself. Nowadays, GPS is the primary navaid that is used in most of the modern aircraft, but VOR is also available as backup or for marking certain airways, for approach procedures, or as a holding point.

Your drone may be small but it can create a big hazard. That's why aviation rules say drones must not fly anywhere near aircraft taking off or landing. That means staying at least 4 kilometers away from any airport or aerodrome, including helipads at hospitals or those used for sightseeing operations.

But what's known as controlled airspace can go well beyond those four K's around airports so before you launch your drone check the area you're planning to fly in. The map on airshare.co.nz shows the controlled airspace within New Zealand. If your backyard is inside that controlled airspace these rules apply there too. You may be able to fly a drone in controlled airspace if you log your intended flight details on airshare.co.nz and ask air traffic control for clearance but there is a way you can fly your drone safely without that clearance. It's by doing what's called a shielded operation.

That means you fly your drone near and below the height of an object that shields your drone from other aircraft. The shielding object could be a building, a tree, or even your house. You must only fly your drone within a hundred metre zone around that object and never above the object's height. That way your drone is less likely to get in the way of another aircraft.

If you're flying a shielded operation within 4 kilometres of an airport or aerodrome, so where there are likely to be quite a few aircraft, you must also have a physical barrier between your drone and the airport. Whatever the barrier is it must be solid enough to stop your drone straying into the path of other aircraft, should you lose control. Keep your drone below the height of the barrier and the shielding object so there's no danger of the drone getting in an aircraft's way.

Doing a shielded operation also means you can safely fly your drone at night - something that's not usually allowed. Another thing to think about before you do a shielded operation is to turn off any obstacle avoidance features as these might make your drone automatically fly up and over your barrier. You can get training to fly a shielded operation safely. Go to the drones page on the CAA website for info.

Finally, wherever and whenever you're flying if you see another aircraft always get your drone out of the way and land immediately. If you need any more information or even just want to check something we're here to help. Get in touch - visit flyyourdrone.nz for more safety tips or follow Fly Your Drone on Facebook. Consider others, be responsible. That's how you fly the right way.

The job of being a pilot can be demanding. Whether it's dealing with long and unpredictable hours, average accommodation, or simply trying to find a decent meal, it's all a challenge. Add to this a full day of flying, including planning, demanding routes, dirt strips, refuelling, baggage handling, and not to mention passengers, it's a full-time gig. We haven't even included home-life pressures - bills, crying babies or second jobs - all adding their weight to a pilot's wellbeing. PILOT: Finally.

WOMAN: Sorry, I got stuck in traffic. MAN: And this makes high workloads, stress, lack of sleep and struggling to stay healthy real issues. They can be a simple daily challenge or an overwhelming problem. It just depends on how they're managed. IAN HOSEGOOD: Helping people help themselves can sometimes be challenging. We're not all as good at planning for our health and wellbeing as we might be, for example, planning for our finances. We think it's of mutual benefit for us to invest in people's wellness, and the things that they can do to feel well today and this year and this month, and there are things that they can do to make sure that they're still well in 5, 10, 20 years from now. So it's about investing in your future but also doing good health and wellbeing measures on any given day as well.

MICHAEL DRANE: Diet, I think, is... It's an interesting conundrum of the 21st century, because there are any number of programs for what you must eat. My mum, who is a nutritionist, said, "Moderation in all things. " And there's probably some sense in that. What we do know is that there are a whole range of illnesses associated with overweight and overeating, and Australia is unfortunately a world leader in that respect. And eating vast amounts of refined carbohydrate sugar is clearly not good for us. We're in the middle of an epidemic of diabetes. And so the common-sense advice to moderate the amount of sugar that we eat, to moderate the amount of unrefined carbohydrate, is sensible.

DARRELL BONETTI: Well, for pilots regarding nutrition, they really just need to focus on eating real food, focusing on eating real food, which is not being modified too much, which is difficult to achieve these days, but eating real food versus eating packet, processed food. Getting as close to nature as possible with your eating pattern. And that can be very, very broad. Making sure that an individual can eat fruit, vegetables, healthy meats, fish, nuts, eggs, dairy if that's appropriate for them - that is real food, and I think everyone can achieve that.

GLENN SINGLEMAN: The interesting thing about health and wellbeing is that the evidence is there. It's been there for 20 years. If you look after yourself, you stay fit, then you're going to live longer and live a better quality life. But people don't take this on board. I mean, the population exercise rate in Australia has actually declined over the last 20 years, instead of increased. And yet we've come to know that exercise is, you know, is really beneficial for our health and wellbeing. But we're not taking that information on board, because there are so many other priorities nipping at our heels, those societal priorities.

One of the benefits of being a doctor is, not only do I understand this research and what it means, I've been able to incorporate that into my life. I prioritise my health, so that I go running. I prioritise my diet, so I don't eat fatty foods. I'm actually a vegan, because it's the diet with the best evidence in terms of mortality and morbidity. Everybody knows this stuff. When you're sitting for hours in a seat, that's not a very healthy thing to do. It's not a natural thing to do. Our bodies were designed to move.

It's a well recognised risk factor that more than 48 hours' immobility per month dramatically increases your risk of getting a deep vein thrombosis. Pilots really do, and all their crew, need to spend a bit of time having health and their own health and safety and personal safety as a priority. And that, to me, is about exercise and diet.

Yeah, Qantas is very lucky to have an in-house medical department, and we do have a health and wellbeing program. Some smaller organisations may not have those sorts of resources to hand. But certainly, CASA itself has some really good health and wellbeing materials on its website. And then also what we tend to suggest is that these smaller organisations go to the peak bodies - The Heart Foundation for cardiac health, Diabetes Australia for good diabetes advice. So we look to those peak bodies, and they've got some fantastic resources that organisations just pick up and run with. When we look at creating a healthy culture, one of the risks to a healthy culture for us in particular is people being overseas on layovers in particular. And some of the risks that are there is that people can be quite isolated.

Not everybody is a social person, and we can see that isolation can be a risk factor. We've also got risk factors around people sometimes on layovers, you know, tending to drink too much alcohol, not get enough exercise and perhaps not eat so well either. So what we're doing is encouraging people through education and training and tools and resources that we provide to them about how to be connected, how to conduct activities like exercise and cycling and social connectedness, and finding out what's available in those locations,

rather than being in their hotel room and perhaps being isolated and otherwise perhaps just using alcohol as a way of dealing with the boredom when they're on a layover. (MACHINE BEEPS) (EXTENDED BEEP) KIRK CAMPBELL: At Seair, we've got a breathalyser in the office, and all our flight crew, all our engineering, anyone who is involved in the aviation sensitive activity is required to do a breathalyser in the morning.

That's a good result. PETER GASH: No alcohol detected. Smiley face for Kirk. The alcohol testing is great, 'cause it's just a part of the culture. They know the person sitting next to them is definitely a zero, that the guy in the workshop's definitely a zero. I'm also proud to say that in the 10 or 11 years, or whatever it is, maybe 12 years since we installed it - and we're onto its second one, we wore the first one out 'cause everyone blows in it every day - we've never had anyone blow over.

This is a part of my responsibility, my commitment to myself, my team, and I'm gonna do it right. - Post-alcohol impairment is really also known as a hangover, essentially, and how much of a hangover people get is affected by quite a few different factors. First of all, it might be affected by their tolerance, and that really relates to how much they regularly drink.

It also clearly obviously relates to how much they've drunk in that particular sitting. And some of the effects are obvious - things like being dehydrated, having a headache, feeling tired, concentration difficulty - those are all flight safety relevant issues. But some of them are a little less obvious, and, for example, what happens with alcohol is it actually gets into our semi-circular canals, which is our balance organ in our inner ear, and it makes the fluid in those inner ears far more sloshy or liquid,

and that means that our balance is actually put off. So those sorts of subtle performance impairments can last quite a long time after an alcohol session, so it's really important for people not just to consider if they don't have a headache anymore and they're feeling generally OK, that there may not be some impairment. There will be some impairment.

So it's really important that people understand that and they drink responsibly when they're in proximity to a flight operation. PILOT: Welcome aboard. PASSENGER: Thank you. - (LAUGHS) WOMAN: How you feeling? - Yeah, haven't been better. - (CHUCKLES) - Where pilots' mental health and wellbeing is concerned, one of the biggest difficulties is the lack of communication.

Who can you tell? The average alpha male finds it very difficult to say "help". And there's been a lot of effort put into developing pathways for people to say just that - "Help, things aren't going right." In the larger airlines, we know that they have put a lot of emphasis upon building peer support and channels for reporting of concerns.

We think peer support is the single most effective intervention that can be done for pilots with mental health issues and alcohol and other drug issues. It means that people are far more likely to seek help early and get referred in to the appropriate mechanisms. MELANIE TODD: A lot of young pilots are going, you know, moving a long way from home, they're without a basic peer support group in some remote locations.

They'll have other pilots, but if something happens or they're ostracised from that group or there's something about that group that doesn't click, then they don't have a support base. MAZ SALVATI: One thing that I've brought up with the team lately is mental health, you know... You know, you might see someone having a bit of a laugh at dinnertime, but they may have had a strenuous day and they may be stressed, so I think it's important to talk about it and not to hide, you know?

I always make sure that I'm asking people, "Are you OK? Are you stressed? "If so, why are you stressed?" - So being mindful of some of the signs in people that they're under additional stress. So, their personality can change in terms of how they respond to you. So somebody who is normally outgoing might become quiet.

Somebody who is normally quiet might snap more easily or be more vocal about not caring about anything anymore, you know? So, watching out for these general signs and saying, "OK, is something going on here?" and then actually having an intervention with that person to say, "Look, are you OK? This is not like you.

" - Sometimes we find ourselves in stressful situations, and it is what it is, you know? You can't help that. We're only humans. Humans get stressed and you'll never be able to beat that or fight that. But I think it's very important to just slow down, take a breath, and say, "Hey, look, listen, what's actually going on?" Because all it can take is one misjudged fuel calculation and you might find yourself in quite a fair bit of trouble.

There's some pretty basic things that you can do. First of all there's some attitudes that are very helpful in terms of wellbeing. So the attitudes that we look for is optimism. We try and make sure that people are looking at things in an optimistic way. There's gratitude, making sure that you feel grateful for what you've got.

And that really has been evidence-based shown to improve people's wellbeing. Mindfulness is a really good evidence-based skill that pilots and others can do to make sure that their mental wellbeing and resilience is strong. Also encouraging people to have social connectedness as well. Within Australia, we're very lucky to have an entire set-up, including CASA, which is aimed towards returning people to flying, not towards excluding people from flying.

Of course absolutely they need to be safe to return to the cockpit, but everybody's working towards making sure that we have that ability to do that. And people can come back in a limited capacity - they might need some supervision or some surveillance initially. As soon as they are safely able to return to the flight deck, they are.

TODD MICKLESON: Fatigue is a difficult one to manage, because fatigue affects everybody differently. It depends on a lot of things, you know, the hours that you work - some people are better working early mornings, late at night. Some people just are more robust at working longer hours than others. If you've got a duty where you're flying all night, you don't want to be up early in the morning and awake all day.

We've got to try and manage that, you know, try and get a sleep in the afternoon. (UPBEAT MUSIC) MATT FOX: Yeah, even at home, like, before I start night shift, um, it's helpful that my daughter's two, and she likes an afternoon sleep for a couple of hours, 'cause I sleep before night shift for two hours.

'Cause there are those nights, they don't happen often, but you can be out flying all night. And it is fatiguing between 2:00 and 6:00 in the morning, like, you do notice in the morning when the sun comes up, "Ooh, I've been flying all night." You do need those good rest hours. - Sleep is absolutely tantamount to wellbeing.

It has a significant impact on both physical health and mental health, and of course with the risk of fatigue within aviation operations, getting good sleep is really, really important. And the other thing we encourage within the sleep bucket is to make sure that people consider whether they may even have a sleep disorder.

So it's a pretty significantly common issue, particularly within the pilot community, to have sleep apnoea, for example. And sleep apnoea can affect not only your ability to deal with a difficult and challenging roster from an aviation perspective, but also can affect your health quite significantly as well, in terms of risk of heart disease and dementia and other health issues.

ROBERT FOSTERLEE: But fatigue is a multidimensional factor. I mean, there is loads of elements to fatigue. But sleep is at the base. You need to get reasonable amounts of sleep. And, you know, we have these kind of algorithms and rules of how many hours someone should get, but the one thing in life we don't learn is, what's your sleep? You might be a seven-hour sleeper.

I could be an eight-hour sleeper. And if I don't get my eight, I'm going to be fatigued. And so, we have to understand that sometimes when we look at these algorithms or these methods of kind of scheduling, what they're doing is, they're scheduling to the average. They're not scheduling to the individual.

And that can be, again, a bit dangerous, especially for those who might need more sleep than average. 'Cause there's...there are a few nine-hour sleepers out there too. And so by saying, "Oh, well, you got eight, you should be fine," that, again, can lead to someone developing fatigue. CARMEL HARRINGTON: Sleep is really essential, and if we don't sleep well, we're going to have cognitive deficits, so we're not going to be able to think and learn as well.

We're going to have health problems. We're more likely to develop cardiovascular or a chronic disease such as metabolic syndrome or type 2 diabetes. And on top of that, we're also not gonna feel very happy. So, we know lack of sleep affects our mental health as well. It's highly associated with the formation of... development of depression.

But if you're fatigued, you don't quite have the resources for it, and you become a bit short. You're irritable. Some people are susceptible to maybe anxiety or nervousness. Other people are more susceptible to maybe feeling negative mood states, we'd call it depression. So again, everybody's different, and they show that fatigue differently.

But the one thing that we can say is that it changes a person, their ability to kind of react. And so when I talk about the psychosocial, that means, oh, teamwork. It means communication. It means CRM. All of those things in the workplace get impacted from those elements of fatigue. "So, were you tired on the day?" "No, I wasn't tired, I was stressed.

" But isn't it a form of fatigue? I mean, it's not just about sleep. Oftentimes if you're emotionally upset, you don't sleep so well. Or sometimes you're not sleeping so well, and that leads again to that susceptibility to become more emotionally upset, and it's a bit of a spiral. I think sometimes if we focus too much on just getting sleep, we're missing out on the big picture and all of the other factors that kind of combine to facilitate performance.

PILOT: What the hell is going on in your head? CO-PILOT: I'm sorry, I'm just... - It's just not good enough! This is your incident! You deal with it! DREW DAWSON: Fatigue is always a shared responsibility. Both ours and many other people's research will show you that when somebody is fatigued in the workplace, it's about as likely to be a result of non-work-related factors as it is to be a result of work-related factors.

And as a result, the company or the organisation can only be really accountable for work-related fatigue. On the other hand, the individual needs to be responsible for non-work-related causes of fatigue. What we've seen in a number of the transport industry initiatives in the last few years is a tendency to realise that family are often the drivers of fatigue, and therefore families need to be part of the educational milieu in which that training and education occurs.

I think it's really important that we begin to understand, because it's fine if you decide, "I don't want to sleep tonight, "I'm gonna go and party or I'm gonna do whatever," provided you're not the driver of my child's school bus. It's a community issue, and we have to start judging people by what damage are you going to do by not sleeping? Are you gonna be my doctor? Are you gonna be my train driver? Are you gonna be my pilot? 'Cause maybe I've got a whole different interest in how you sleep if you're one of those people.

At present, BrahMos is the fastest and only supersonic cruise missile on the planet. During its cruise, it breaks the sound barrier by traveling three times faster than a sound wave, and no known weapon system can intercept it due to its speed. In the first stage, solid boosters power this missile, and the second stage features the ramjet engines. We'll learn more about these intriguing engines in this video. We thank brilliant.org for supporting this video. More about less.ex brilliant collaboration towards the end of this video.

To understand ramjet technology, we first need to understand the concept of shock waves. Everybody is familiar with the ripples that are created in water when an object is thrown into it; these ripples travel uniformly. Right now, take a look at this interesting scenario: suppose a boy is pulling a tennis ball towards him. The movement of the source produces ripples that are not concentric. Isn't that interesting? The same effect can happen with sound waves during aircraft movement. Here, the sound waves are taking the place of the water ripples, and the aircraft is taking the place of the tennis ball. In this scenario, the sound ripples will obviously travel at the speed of sound. But here's a brain teaser for you: what will happen if the aircraft moves at the speed of sound? Obviously, the sound waves won't be able to move forward, so if you move along with the aircraft, it will look as if the sound waves are stuck at the front, forming a sound barrier.

During World War II, the sound barrier was assumed to be an invisible wall due to the aircraft experiencing high drag. However, what if the aircraft moves faster than the sound waves? The concentrated waves at the front of the aircraft will suddenly form a distributed ripple pattern as shown. The aircraft needs to apply more thrust during this transition. The distributed pattern has a conical shape. The interesting thing is that a very narrow volume with a thickness of 200 nanometers and high temperature and pressure is formed on this conical shape. The pressure in this narrow region is almost 29 times that of the atmospheric pressure. This region is known as a shock wave.

Why is the shock wave formed when the airplane moves at a speed greater than the speed of sound? This result is because in fluid, the information travels at the speed of sound. When the airplane travels faster than sound, the air volume shaded in red color has absolutely no information about the disturbance the moving object is making. However, inside the green region, the disturbance in the fluid happened with prior information. When the disturbed fluids suddenly interact with fluid particles in the red region, which has no information about what is going on, a shock gets formed in the boundary.

Shock waves can cause harm to a human body. However, even though these high pressure waves are disastrous, opportunity lies in the middle of difficulty. Using the concept of the shock wave, let's understand how a ramjet engine works. Ramjet engines have a very simple geometry. They have only three main stationary parts: a diffuser region at the entrance, a combustion chamber in the middle, and a nozzle at the exit. The duty of the diffuser is to increase pressure and temperature of the air. The ramjet engines will work only in supersonic conditions. Since the flow is supersonic, the scientists tweaked the shock wave concept to increase the diffuser pressure. Let's see how.

The shock waves get generated from many points of this cylindrical object. Remember, in a shock wave, the high pressure and temperature are there only in a narrow region. However, when many such shock waves club together, something interesting happens. You can see at the inlet a conical region is formed with no effective shock wave at all; this will be a low-pressure region. It is also clear a high-pressure conical wall is getting generated at the inlet region. What about the remaining volume? To understand the remaining volume condition, let's take a cross-section of the cones at different lengths. You can see a flower-like shape. If you increase the number of cones, this flower will fill the entire area. Remember, the number of shock cones getting generated from a circle edge is infinite. This area filling is true for any length, which means after the initial void cone, a thick volume of high pressure and temperature air is formed inside the cylinder. In short, it forms automatic compression action with the help of shock waves. This is the ram effect.

This high pressure and high temperature air can create effective combustion in the combustion chamber. Hydrogen is commonly used as fuel for ramjet engines. The combustion chamber further increases the gas temperature and also the fluid velocity. According to Newton's third law, the greater the exhaust jet speed, the more thrust the rocket derives. To increase the speed of the jet further, a converging-diverging nozzle is also added at the exit.

Even though this simple diffuser arrangement achieves a very high-pressure boost, if the combustion pressure exceeds limits, the shock front will be blown out, resulting in compressed air spilling out around the front of the tube. This spill limits the speed of the ramjet to 1.2 Mach. Scientists didn't stop here; they further improved the ram effect with the help of an aerodynamically designed inner body. In this new geometry, you can see that the area allocated for the air is actually decreasing along with the flow. For supersonic flow, when the area decreases, the pressure increases. In ramjets, the majority of the pressure rise happens due to the shock effect and because of a concept called oblique shock wave. When air hits the nose of the inner body, it deflects with some angle, forming an oblique shock wave. This oblique shock wave hits the outer tube, deflects multiple times, and is finally terminated by a normal shock wave. In this method, the air spillout does not happen, and scientists were able to achieve a high Mach number for the ramjet engine.

Now let's learn a little more about the combustion chamber design of ramjet engines. The airflow speed through the ramjet is so high that the mixing of fuel completes within two to five milliseconds. For complete mixing of fuel and air, a flame holder is used, which helps to maintain continuous combustion. It also stops the flame from blowing out by sheltering it. Ramjets are the most efficient in the speed range of Mach 3 to Mach 6. When traveling at low speed, the thrust isn't sufficient to overcome the drag. As a result, the stand-alone ramjet engine is not feasible; it needs the solid booster to propel the missile towards supersonic speeds. The ramjet does not contain any moving parts, unlike jet engines.

Before you leave, please make use of brilliant.org lesix collaboration and get a discount of 20 percent. Brilliant has recently upped the interactivity on their platform to a new level. Check out this interactive lesson on the center of mass, for example. This is an example of Brilliant's newly updated scientific thinking course. Follow the link given below and be a brilliant and creative engineer. We hope you enjoyed the amazing technology of the ramjet engines.

In this lesson from Free Pilot Training, we'll be discussing the pitot-static instruments and we'll explain how those work. In the last few lessons, we've been discussing the gyroscopic instruments, but today we're going to talk about three of those primary flight instruments that use air pressure to give us information. These are the airspeed indicator, the altimeter, and the vertical speed indicator. These instruments are provided air pressure from the pitot tube and the static port, and they turn it into information that's really important for pilots in flight.

There are three types of air pressure that come into play when we talk about these instruments: static air pressure, dynamic air pressure, and total air pressure. Static pressure, which is also called ambient air pressure, is pressure that's caused by our atmosphere. This is always present, whether the airplane is stopped or moving, and although it might seem unnoticeable to you, these air molecules push on everything in our atmosphere. The closer you are to the center of the Earth, the more tightly these air molecules are packed, and because they're packed so tightly at lower elevations, the lower your altitude, the higher your static air pressure is. Our airplanes use static ports to sense this type of air pressure. These are usually placed on the side so they're not affected by relative wind. Static air pressure is measured in inches of mercury. On a normal standard day at sea level, the average air pressure is 29.92 inches of mercury. Now, the air pressure isn't always 29.92 inches of mercury there, but this is about the average, so this is what we call standard air pressure. Then every thousand feet above sea level, the pressure reduces by one inch of mercury.

In the next lesson, we're going to go into a lot more detail about this and how the altimeter works, so if you haven't already subscribed, please consider doing so now. Anytime an object like an airplane moves through the air, it's impacted by the air molecules that it is traveling through, and this creates a certain amount of pressure on the object that's equal and opposite to the airplane's direction of travel, and this is called dynamic air pressure. In order to understand how the pitot-static system works, you have to understand that this pressure is directly related to the speed at which the aircraft is flying.

Next, we have the total air pressure, and this is a combination of dynamic and static air pressure. While this may seem obvious at first, you'll see why we talk about this here in just a minute. Now, the altimeter uses a static port to sense the static pressure outside the aircraft, and because the static pressure changes one inch of mercury every thousand feet, the altimeter is able to give us an altitude reading because it senses that pressure. As I mentioned before, static ports are placed on the side of aircraft, and this keeps the instruments from being affected by dynamic air pressure, and this keeps the readings as accurate as possible.

The other instrument that uses a static port is the vertical speed indicator. This instrument allows air to escape or come in through a small hole, which is vented through the static port. By allowing air to come in or go out, this instrument senses the pressure differences as we climb or descend, then it gives us a reading in feet per minute. The airspeed indicator is a little bit different animal. It also receives air from the static port but not for reasons you might think. The airspeed indicator measures the ram air that comes from relative wind through the pitot tube, but this doesn't give us an accurate measurement because static air actually makes its way into the pitot tube as well, and this is that total air pressure we were talking about earlier. And by taking static air from the static port, the airspeed indicator is able to offset any static air that might come in through the pitot tube to keep the airspeed indicator as accurate as possible.

The people who designed your airplane usually put the pitot tube in a spot where it won't be affected by the prop wash, but there is something that can affect your airspeed indicator, and that's the angle of the pitot tube in relation to the relative wind. High angles of attack and different airplane configurations can affect the accuracy of your airspeed indicator, and that's because weird angles can make it difficult for the ram air to enter the pitot tube. Every airplane is different, but every airplane has some kind of error caused by this, and the manufacturers account for this by putting a chart in the POH. This is what we call calibrated airspeed. Once you make these corrections, something else you could run into that would cause these instruments to get errors is if the pitot tube or the static port got clogged up, and there's a lot of different things that could clog up these things—anything from bugs, mud, ice, and that's just to name a few.

One thing that shouldn't clog up your pitot tube, though, is water. That's because of this little drain hole here on the back, I call this the weeping hole. This is there so if water enters the front of your pitot tube, it'll just slide right out the back here. But if the water freezes in or on the pitot tube, then it can start clogging it up again, but that's what these little heating elements are for. You just turn the pitot heat on in your cockpit, and it should heat these up enough to melt that ice. So what happens if these things get clogged? Well, if the pitot tube gets clogged, the only instrument that's going to be affected is your airspeed indicator, and if you remember, that's because this is the only instrument that uses dynamic air pressure to give us a reading.

For the airspeed indicator, three possible problems could happen. The first would be if the hole in the front of the pitot tube for the ram air got clogged. As long as your drain hole doesn't get clogged, what will happen is your airspeed will drop to zero, and that's because the pitot tube is no longer taking in ram air but the static port and the drain hole are still both taking in static air which allow them to offset each other. The second possibility is if the front of the pitot tube and the drain hole get clogged. If this happens, any air pressure in the pitot system will be trapped, and your airspeed indicator is frozen at the last indication it was giving you. From here, if the static port is also plugged, you won't see any change, but if the static port is clear, then the airspeed indicator will make minor changes with altitude. I like to tell students that your airspeed indicator just turned into an altimeter at this point.

The third thing that could possibly happen is only the static port gets clogged. If this happens, the pitot tube is still taking in the dynamic and the static pressure from the front of the pitot tube, but the static port is unable to offset that static air that's also coming in the front. This means that your airspeed indicator is going to give you faster airspeeds than what you're actually going. Now, because the altimeter and the vertical speed indicator both use a static port to get their information, if this gets clogged, it's going to affect both of those too. For the altimeter, if the static port gets clogged, it's going to freeze at the last altitude that it was indicating. But the vertical speed indicator will only display 0 because it can no longer sense a climb or a descent. If you're lucky enough to have a clogged static port, I do have some good news for you, though.

On most newer training airplanes, they have something called an alternate static source. Typically, this is an alternate static port that's on the inside of your cockpit, and you can select this alternate static port by flipping a switch labeled "alternate static" on most airplanes. Just keep in mind when you use this alternate static source, it's not quite as accurate as the one on the outside of the airplane, and that's because the pressure difference on the inside of the cab is slightly different than outside. Now, if you don't have an alternate static source, one thing you can do is you can break the glass on any of the static instruments. If you do this, I recommend breaking the glass on the vertical speed indicator, and that's because it's by far the least important of the instruments.

Once again, if you do this, this is nowhere nearly as accurate as a static port on the outside of the airplane, but something is better than nothing, and in an emergency, this could save your life. I hope you enjoyed today's video. If you did, would you click that like button for me? Also, if you're really enjoying this training from the Free Pilot Training channel, be sure to check out our t-shirt store in the description below, then watch this video right here. You know you want to.

Developed over the course of decades, GPS has become far more ubiquitous than most people realize. Not just for navigation, its extreme accuracy in timekeeping (+/- 10 billionths of a second) has been used by countless businesses the world over for everything from aiding in power grid management to helping manage stock market and other banking transactions. The GPS system essentially allows for companies to have near atomic clock-level precision in their systems, including easy time synchronization across the globe, without actually needing to have an atomic clock or come up with their own systems for global synchronization.

The problem is that, owing to a quirk of the original specifications, on April 6, 2019, many GPS receivers are about to stop working correctly unless the firmware for them is updated promptly. So what’s going on here, how exactly does the GPS system work, and who first got the idea for such a system? On October 4, 1957, the Soviet Union launched Sputnik. As you might imagine, this tiny satellite, along with subsequent satellites in the line, were closely monitored by scientists the world over. Most pertinent to the topic at hand today were two physicists at Johns Hopkins University named William Guier and George Weiffenbach. As they studied the orbits and signals coming from the Sputnik satellites the pair realized that, thanks to how fast the satellites were going and the nature of their broadcasts, they could use the Doppler shift of the signal to very accurately determine the satellite’s position.

Not long after, one Frank McClure, also of Johns Hopkins University, asked the pair to study whether it would be possible to do this the other way around. They soon found that, indeed, using the satellite’s known orbit and studying the signal from it as it moved, the observer on the ground could in a relatively short time span determine their own location. This got the wheels turning. Various systems were proposed and, in some cases, developed. Most notable to the eventual evolution of GPS was the Navy’s Navigation Satellite System (also known as the Navy Transit Program), which was up and running fully by 1964. This system could, in theory, tell a submarine or ship crew where they were within about 25 meters, though location could only be updated about once per hour and took about 10-15 minutes to acquire.

Further, if the ship was moving, the precision would be off by about one nautical mile per 5 knots of speed. Another critical system to the ultimate development of GPS was known as Timation, which initially used quartz clocks synchronized on the ground and on the satellites as a key component of how the system determined where the ground observer was located. However, with such relatively imprecise clocks, the first tests resulted in an accuracy of only about 0.3 nautical miles and took about 15 minutes of receiving data to nail down that location. Subsequent advancements in Timation improved things, even testing using an atomic clock for increased accuracy. But Timation was about to go the way of the Dodo.

By the early 1970s, the Navigation System Using Timing and Ranging (Navstar, eventually Navstar-GPS) was proposed, essentially combining elements from systems like Transit, Timation, and a few other similar systems in an attempt to make a better system from what was learned in those projects. Fast-forward to 1983 and while the U.S. didn’t yet have a fully operational GPS system, the first prototype satellites were up and the system was being slowly tested and implemented. It was at this point that Korean Air Lines Flight 007, which originally departed from New York, refueled and took off from Anchorage, Alaska, bound for Seoul, South Korea. What does this have to do with ubiquitous GPS as we know it today? On its way, the pilots had an unnoticed autopilot issue, resulting in them unknowingly straying into Soviet airspace.

Convinced the passenger plane was actually a spy plane, the Soviets launched Su-15 jets to intercept the (apparently) most poorly crafted spy plane in history- the old “It’s so overt, it’s covert” approach to spying. Warning shots were fired, though the pilot who did it stated in a later interview, “I fired four bursts, more than 200 rounds. For all the good it did. After all, I was loaded with armor-piercing shells, not incendiary shells. It’s doubtful whether anyone could see them.” Not long after, the pilots of Korean Air 007 called Tokyo Area Control Center, requesting to climb to Flight Level 350 (35,000 feet) from Flight Level 330 (33,000 feet).

This resulted in the aircraft slowing below the speed the tracking high-speed interceptors normally operated at, and thus, them blowing right by the plane. This was interpreted as an evasive maneuver, even though it was actually just done for fuel economy reasons. A heated debate among the Soviet brass ensued over whether more time should be taken to identify the plane in case it was simply a passenger airliner as it appeared. But as it was about to fly into international waters, and may in fact already have been at that point, the decision was made to shoot first and ask questions later. The attacking pilot described what happened next: “Destroy the target…!” That was easy to say. But how? With shells? I had already expended 243 rounds. Ram it? I had always thought of that as poor taste. Ramming is the last resort. Just in case, I had already completed my turn and was coming down on top of him. Then, I had an idea. I dropped below him about two thousand meters… afterburners. Switched on the missiles and brought the nose up sharply. Success! I have a lock on. Two missiles were fired and exploded near the Boeing plane causing significant damage, though in a testament to how safe commercial airplanes typically are, the pilots were able to regain control over the aircraft, even for a time able to maintain level and stable flight. However, they eventually found themselves in a slow spiral which ended in a crash killing all 269 aboard.

As a direct result of this tragedy, President Ronald Reagan announced on September 16, 1983, that the GPS system that had previously been intended for U.S. military use only would now be made available for everyone to use, with the initial idea being the numerous safety benefits such a system would have in civil aviation over using then available navigation tools. This brings us to how exactly the GPS system works in the first place. Amazingly complex on some levels, the actual nuts and bolts of the system are relatively straightforward to understand. To begin with, consider what happens if you’re standing in an unknown location and you ask someone where you are. They reply simply- “You are 212 miles from Seattle, Washington.” You now can draw a circle on a map with a radius of 212 miles from Seattle. Assuming the person giving you that information is correct, you know you’re somewhere along that circular line. Not super helpful at this point by itself, you then ask someone else, and they say, “You are 150 miles from Vancouver BC.” Now you’re getting somewhere. When you draw that circle on the map, you’ll see it intersects at two points. You are standing on one of those two points. Noticing that you are not, in fact, floating in the ocean, you could at this point deduce which point you are on, but work with us here people. Instead of making such an assumption, you decide your senses are never to be trusted and, after all, Jesus stood on water, so why not you? Thus, you ask a third person- they say, “You are 500 miles from Boise, Idaho.” That circle drawn, you now know exactly where you are in two-dimensional space. Near Kamloops, Canada, as it turns out. This is more or less what’s happening with GPS, except in the case of GPS you need to think in terms of 3D spheres instead of 2D circles. Further, how the system tells you your exact distance from a reference point, in this case each of the satellites, is via transmitting the satellites’ exact locations in orbit and a timestamp of the exact time when said transmission was sent. This time is synchronized across the various satellites in the GPS constellation. The receiver then subtracts the current known time upon receiving the data from that transmission time to determine the time it took for that signal to be transmitted from the satellites to its location. Combining that with the known satellite locations and the known speed of light with which the radio signal was propagated, it can then crunch the numbers to determine with remarkable accuracy its location, with margins of error owing to things like the ionosphere interfering with the propagation of the signal, and various other real-world factors such as this potentially throwing things off a little. Even with these potential issues, however, the latest generation of the GPS system can, in theory, pinpoint your location within about a foot or about 30 centimeters. You may have spotted a problem here, however. While the GPS satellites are using extremely precise and synchronized atomic clocks, the GPS system in your car, for example, has no such synchronized atomic clock. So how does it accurately determine how long it took for the signal to get from the satellite to itself? It simply uses at least four, instead of three, satellites, giving it the extra data point it needs to solve the necessary equations to get the appropriate missing time variable. In a nutshell, there is only one point in time that will match the edge of all four spheres intersecting in one point in space on Earth. Thus, once the variables are solved for, the receiver can adjust its own timekeeping appropriately to be almost perfectly synchronized, at least momentarily, with the much more precise GPS atomic clocks. In some sense, this makes GPS something of a 4D system, in that, with it, you can know your precise point in not only space, but time. By continually updating its own internal clock in this way, the receiver on the ground ends up being nearly as accurate as an atomic clock and is a timekeeping device that is then almost perfectly synchronized with other such receivers across the globe, all for almost no cost at all to the end-users because the U.S. government is footing the bill for all the expensive bits of the system and maintaining it. Speaking of that maintenance, another problem you may have spotted is that various factors can, and do, continually move the GPS satellites off their original orbits. So how is this accounted for? Tracking stations on Earth continually monitor the exact orbits of the various GPS satellites, with this information, along with any needed time corrections to account for things like relativity, frequently updated in the GPS almanac and ephemeris. These two data sets are used for holding satellite status and positional information and are regularly broadcast to receivers, which is how said receivers know the exact positions of the satellites in the first place. The satellites themselves can also have their orbits adjusted if necessary, with this process simply being to mark the satellite as “unhealthy” so receivers will ignore it, then move it to its new position, track that orbit, and once that is accurately known, update the almanac and ephemeris and mark the satellite as “healthy” again. So that’s more or less how GPS came to be and how it works at a high level. What about the part where we said many GPS devices may potentially stop working very soon if not updated? Near the turn of the century something happened that had never happened before in the GPS world- dubbed a “dress rehearsal for the Y2K bug”. You see, as a part of the time stamp sent by the GPS satellites, there is something known as the Week Number- literally just the number of weeks that have passed since an epoch, originally set to January 6, 1980. Along with this Week Number, the number of seconds since midnight on the previous Saturday evening is sent, thus allowing the GPS receiver to calculate the exact date. So what’s the problem with this? It turns out every 1024 weeks (about every 19 years and 8 months) from the epoch, the number rolls back to 0 owing to this integer information being in 10-bit format. Thus, when this happens, any GPS receiver that doesn’t account for the Week Number Rollover will likely stop functioning correctly, though the nature of the malfunction varies from vendor to vendor and device, depending on how said vendor implemented their system. For some, the bug might manifest as a simple benign date reporting error. For others, such a date reporting error might mean everything from incorrect positioning to even a full system crash. If you’ve done the math, you’ve probably deduced that this issue first popped up in August of 1999, only about four years after the GPS system itself was fully operational. At this point, of course, GPS wasn’t something that was so ubiquitously depended on as it is today, with only 10-15 million GPS receivers in use worldwide in 1999 according to a 1999 report by the United States Department of Commerce’s Office of Telecommunications. Today, of course, that number is in the billions of devices. Thankfully, when the next Week Number Rollover event happens on April 6, 2019, it would seem most companies that rely on GPS for critical systems, like airlines, banking institutions, cell networks, power grids, etc., have already taken the necessary steps to account for the problem. The more realistic problems with this second Week Number Rollover event will probably mostly occur at the consumer level, as most people simply are not aware of the issue at all. Thankfully, if you’ve updated your firmware on your GPS device recently or simply own a GPS device purchased in the last few years, you’re probably going to be fine here. However, should you own a GPS device that is several years old, that may not be the case and you’ll most definitely want to go to the manufacturer’s website and download any relevant updates before the second GPS epoch. That public service announcement out of the way, if you’re now wondering why somebody doesn’t just change the specification altogether to stop using a 10-bit Week Number, well, you’re not the first to think of this. Under the latest GPS interface specifications, a 13-bit Week Number is now used, meaning in newer devices that support this, the issue won’t come up again for about a century and a half. As the machines are bound to rise up and enslave humanity long before that occurs, that’s really their issue to solve at that point.

In this video, we'll be talking about spins. According to the FAA, a spin is an aggravated stall where yaw is introduced, which causes a downward torque screw path. Just as we discussed in lesson three, when an airfoil exceeds its critical angle of attack, it will stall. When an aircraft stalls, it is possible for one wing to stall more than the other wing; this is called an aggravated stall.

This can happen when an airplane stalls in uncoordinated flight. Uncoordinated flight is what happens anytime the vertical axis of the aircraft is not aligned with the direction of travel; this is also known as a side slip. You can eliminate side slip conditions by using your inclinometer and rudder pedals. In a turn, you'll hear your instructor refer to these as slips or skids. An easy way to remember which pedal to use is to step on the ball. If the airplane does get into a side slip or yawed condition, then it stalls, whichever wing has stalled more will drop faster than the other one. One wing dropping more quickly than the other; the airplane will begin to rotate and then it will follow the corkscrew path.

Be sure to look at your aircraft's specific POH in order to know your aircraft's specific spin recovery procedures, but most instructors will use the acronym PARE: Power idle, Ailerons and elevator neutral, Rudder opposite until the spinning stops, then Elevator up to recover to level flight. You'll want to memorize these procedures when you start your flight training.

But for the FAA written exam, the most important thing to remember today is that in a spin, both wings are stalled. Thanks for joining me for today's lesson on spins. Please click that like button if you're getting value out of this training and don't forget to subscribe so you know when there's a new video on Free Pilot Training. Aircraft calling, safe position.

Airplanes generate thrust to overcome drag. Drag is the air resistance that opposes flight; it acts parallel and in the same direction as the relative airflow and is a relentless force that deserves a thorough Flight Club treatment and your full attention. Total drag consists of drag forces that are linked to lift production, known as induced drag, and those that are not linked to lift production, known as parasite drag.

Let's have a look at induced drag. At high angles of attack, the high-pressure air below the wing likes to swirl around the wingtip towards the low-pressure air above the wing. A twisting vortex of air forms behind the wing, deflecting the airflow downwards. An inclined local airflow is created, which is the average of relative airflow and the deflected airflow, resulting in the lift vector tilting backwards and contributing to total drag.

Now for parasite drag, which consists of form drag, skin friction drag, and interference drag. Form drag is caused by disturbed airflow that separated from the surface and spawned into turbulent wake. The more streamlined an object is, the less form drag it creates, so any obstruction to smooth airflow, such as dangling wheels, will produce form drag. If we flatten a spherical object completely, the only drag we get now is the skin friction. As the name suggests, skin friction depends on the quality of the skin surface the airflow passes over. A laminar flow results when the airflow passes over smooth surfaces, so drag is small. But introduce wing ice or exposed rivets, and a turbulent boundary layer forms, resulting in more skin friction drag.

The airflow around the wing may flow faster than the airflow around the fuselage, so where these different airflows meet, interference drag is born because they clash within the space they share. These graphs represent induced and parasite drag against airspeed. Induced drag is most significant at low airspeeds and high angles of attack, where the pressure differential between the top and bottom of the wing is the greatest. On the other hand, an increase in airspeed increases parasite drag by a factor of the square of airspeed. So, if you double the airspeed, for example, you get four times the parasite drag.