How important is it to have talent to become airline pilot? The situation that led me to ask the question is as follows:

I am a student pilot with only about 10 hours of flight time. I passed the aptitude and personality tests prepared by German Aerospace Center (German: Deutsches Zentrum für Luft- und Raumfahrt).

My instructor keeps on telling me since the very first couple of flights that I lack some talent and it's not really possible for me to become an airline pilot. (He has never flown as airliner, only military aircraft but he is obviously a good pilot with long teaching experience.)

So, what is the possibility that he is right? How much and what type of talent is required?

Please note that I haven't caused any major safety problems, and other students claim that they made pretty much the same mistakes I do.

Edit : Since some people misunderstood the situation, I'll clear some issues:
1-) I'm on some scholarship program of an airlines company. Money isn't an issue.
2-) I'm generally considered to be pretty smart.
3-) There's no reason that I could be discriminated by the instructor.

You are asking the wrong question. Ask yourself this:

Do I really want to become a pilot?

If the answer is yes, then you can become a pilot. You only require hard work, and a lot of money (but we are not talking about this).

Having talent is subjective. Sometimes you try to learn something new and you get into that relatively quickly. Sometimes you don't. It doesn't just depend on talent, but on several factors.

If you feel that you are not making any different mistakes than other student pilots, then change your instructor.

There are several discussions about changing flight instructors. You can benefit from these ones:

What to look for in a flight instructor?
Is there a downside to trying multiple flight instructors?

That is a polite way of saying you are not smart enough. You are not alone. For the majority of people who try to fly the same exact thing happens as happened to you. The instructor can tell in the first 5 minutes if a student can "make it", meaning they have the intelligence and coordination to learn to fly a plane. If they are sub-par, then the first flight just becomes a "ride" and when the aircraft gets on the ground the instructor gently breaks the news to the student somehow. In your case he tells you, you "lack talent". Each instructor has his own way of doing it.

Flying an aircraft is HARD. Things happen simultaneously in 3 dimensions with 6 degrees of freedom. You have to be a certain intelligence level to do it, which is about 130-135 IQ. If a person is below this level, it is very dangerous for them to fly and they have a high probability of making an error that will kill them and possibly other people. There is no shame in not being a genius. Every person needs to know and respect their limitations.

You are you lucky you had a good instructor. There are unscrupulous instructors out there who will string a non-candidate along, taking their money even though they know the student can never be soloed. This is greedy and dangerous, because they keep taking dangerous students up in the air. It sounds like your instructor has been taking you up multiple times, however, and he really shouldn't be doing this.

Flying is fun and a great dimension to life, but for most people, unfortunately, they need to do it from the passenger's seat. There are a lot of ways to enjoy flying without being a pilot. I encourage you to explore those other options.

Comment on some of the other answers: Some of the other answerers, who are obviously not CFIs, have said things to the effect that "anybody can fly if they want to hard enough." This is both a factually wrong idea and expresses a dangerous and delusional attitude. An aircraft is not like a car that just runs into a ditch when you screw up. An aircraft WILL kill anybody who is not fully competent and tries to fly, and I know of several such people who have killed themselves in that way. CFIs do not tell unqualified students not to fly because they are jerks. They tell them that to save their money and maybe their life. Listen to them.


What is the probability that passengers can survive a ditching in a 747 at MTOW? Let's suppose a catastrophic EFATO has occurred while climbing out of JFK from Runway 31L, the aircraft is at its MTOW and the best option is to set it down in Jamaica Bay. How long would the aeroplane float and what are the chances of surviving?

Aircraft are designed with ditching in mind, but the outcome depends on many circumstances, most importantly on how calm the water is and how well the aircraft can be controlled.

The Wikipedia article on Ditching lists emergency water landings and other accidents where aircraft ended in water.

There is no ditching by 747, so we don't have any specific reference. However:

B747 is not that different from other types of aircraft. Controlled ditchings on calm water were successful in different types; it is likely that one would be possible with B747 too.
How long the aircraft would remain afloat depends on the damage. But if it did not break up, it would likely manage to keep afloat for the 90 seconds needed for evacuation. And the slides can be used as life rafts.
There was one case where B747 ended up in water after overrunning runway (so at lower speed than landing), China Airlines flight 605, and the aircraft did remain afloat long enough to evacuate it.
Also any aircraft that will be used for flying across large bodies of water, which obviously includes all variants of B747, must be certified for ditching. This involves designing it so that, at least according to model, a controlled ditching will be smooth enough not to cause serious injuries to occupants and will leave it afloat long enough for successful evacuation.

Concerning floating: planes tend to float for a long time, potentially indefinitely. The reason for this is that they are much lighter than water. For example, jet fuel is about 80% of the density of fresh water, so even if the wings were fully loaded with fuel, they would be lighter than water. Some of the space in the wing tanks is air, which of course is even lighter. There are vents in the tanks, but it would tank a long time like many hours or probably days before a wing could even partially fill up with water.

Concerning survivability: there is no way to predict the outcome. It would depend completely on the reactions and skill of the pilot and exactly when the engines lost power. In general, landing on water is not a problem, as was seen in the accident of US Air 1549. A big plane can (and has) actually run over a small house and stay relatively intact. So, even if it went up one of the beaches on the spit it might be OK. The biggest threats are running at high speed into an object or terrain feature, or stalling; both of those not happening are largely dependent on the skill and cool nerve of the pilot.

When aircraft take off, they usually have a steep rate of ascent which would be a stall configuration in unpowered flight, so if the engines fail the pilot has to immediately react to avoid a stall. When this happens, the pilot has to react within a fraction of a second or so. If the pilot panics and pulls back on the stick, it's game over.

If the pilot is good, they will have an "emergency plan" and will mentally know ahead of time exactly what they will do if they lose power at any given point on any given runway. That plan includes a landing spot. For example, when I fly to a new airport I look at Google Earth and decide where I will land in the case of an emergency during take off. The plan sometimes has to have height thresholds, too. For example, if I lose power at 100 feet I do this, but if lose power at 400 feet I do that. The plan always has a "minimum turnaround altitude". This is the height where you are safe to do a 180-degree turn and go back to the runway.  Note that the plan has to recalculated every time you fly because of wind. So, if there is a crosswind coming from one direction or another that could affect your choice of emergency landing location.


What kind of cameras are onboard high altitude UAVs that aid in its control? I ask this question in the context of people flying their drones much higher than the usual hobby planes. Satellite based GPS navigated Autopilots using photogrammetry and/ or military drones.

What kind of cameras do first-person-view (FPV) pilots use and mount onboard to control the plane, and not for any sensors to collect data/ perform other tasks?

The Bottom Line Up Front

Infrared and visual video cameras aid in navigation of larger class UAVs and are helpful for safety but do not satisfy the legal requirements for unmanned aircraft to operate in US/international airspace. Instead, the use of onboard navigation systems like GPS, combined with air traffic control services and common flight safety rules allow safe navigation of high and medium altitude UAVs.

What UAVs Operate at High Altitude?

Northrop Grumman's "RQ-4" variants (e.g. USAF RQ-4B Global Hawk, US Navy MQ-4C Triton, NATO RQ-4D Phoenix) are the only widely recognized UAVs flown at high altitudes (FL500-600). The RQ-4 is also the largest UAV with a wingspan greater than a Boeing 757.  All other UAVs, including the MQ-9 Reaper, operate at medium or low altitudes.

How Does the RQ-4 Navigate?

The RQ-4 has sophisticated, GPS & gyro-enabled navigation computers that ensure it always knows where it is and where it is going. To avoid airborne hazards like other aircraft or bad weather, it follows the same instrument flight 'rules of the road' that manned aircraft rely on when flying at night or in the clouds. Specifically, air traffic controllers use radar to track aircraft from the ground and alert the pilots if they see an unsafe situation on their radar screens. These instances are rare, however, because everyone follows their flight plan and obeys air traffic controllers' instructions in order to remain safely separated in the air--even remotely piloted aircraft.

Does the RQ-4 Have Any Cameras Used to Aid in its Control?

Yes. As a backup to air traffic control clearances to taxi, takeoff, and land, the RQ-4 has a forward-facing infrared video camera on the nose of the airplane.  Although it is not legally required to have this camera, it is used only as a backup for the pilot to ensure the runway is clear of obstacles during taxi and prior to landing on the runway. Radio transmission of the video camera signal is via line-of-sight antennas only (not over satellites), so therefore it is limited only to the airfield/runway environment where the ground control station is located and is not used while away from the airfield during climb, cruise, or descent.

Note there are two small windows in the pressurized camera compartment: One upper window for the video camera lens and the lower window used to display the pressure dial for the camera compartment.

What About Medium/Low Altitude UAVs?

Medium altitude UAVs like the MQ-9 predator carry a variety of infrared (day/night) and electro-optical (day only) full motion video cameras used primarily for their mission rather than for navigation. Unlike the high-altitude RQ-4, they operate at the same altitude levels as commercial air traffic.  They can follow the same instrument flight 'rules of the road' that manned aircraft do when flying at night or in the clouds. Often, their mission requires them to fly in areas where following these rules aren't required by all aircraft. In this type of airspace, pilots of smaller aircraft like gliders and crop-dusters don't have the radios to communicate to air traffic control and count on other aircraft to 'see-and-avoid' them instead. The MQ-9 does not have a pilot onboard to look out the window and avoid these 'visual flight only' aircraft, so it needs other solutions to ensure safe navigation.

The MQ-9 does have a powerful ball-mounted, full-motion video camera onboard. However, the USA's Federal Aviation Administration and the worldwide International Civil Aviation Organization has not deemed the use of this camera as a sufficient substitute for the see-and-avoid requirement. Therefore, despite the MQ-9's robust visual/infrared camera system, it must rely on other methods of deconfliction like temporary/military restricted airspace, special clearances, and even chase airplanes, in order to conduct its training in the US and its missions overseas.  The same challenges exist with smaller, low-altitude military unmanned aerial systems and commercially operated drones.

Are Cameras Any Good For Long Range Navigation?

That depends on what you consider long range. Navigation using cameras, especially to avoid other aircraft, requires low-latency. It does little good to see a rogue aircraft filling your windscreen if, by the time you see it on the screen, the plane has already crashed into your UAV. This usually isn't a problem for FPV hobbyists because they have a line of sight video signal, directly from the RC aircraft, that feels instantaneous to the pilot wearing FPV goggles. On the other hand, truly long ranges require operation beyond line of sight, relying on satellites to pass information to/from the aircraft. This extra architecture causes video latency, sometimes up to multiple seconds, making it nearly impossible to visually react to a time-critical safety event.

A Better Alternative to Cameras

In addition to the video latency problem, video cameras on medium/high altitude UAVs are specialized to focus on small targets at long range--not scanning the skies for unidentified aircraft. Imagine trying to spot a fly buzzing around you while looking through a toilet paper tube. An additional, wide-angle navigation camera/lens could be carried on the aircraft but it would not be worth the additional cost, weight, space, and power consumption. Instead, long-range aircraft like the RQ-4 and MQ-9 rely on a framework of aircraft regulations, ground-based air traffic control, and segregated airspace to safely navigate.

Note: This response was drafted from scratch, solely to answer Rajath's question about cameras on high altitude UAVs. Thanks in advance for your feedback.

The Predator drone has an array of optics for various regimes of flight (there is no citation on wiki for this so take it at face value):

  The aircraft is equipped with the AN/AAS-52 Multi-spectral Targeting
  System, a color nose camera (generally used by the pilot for flight
  control), a variable aperture day-TV camera, and a variable aperture
  thermographic camera (for low light/night). Previously, Predators were
  equipped with a synthetic aperture radar for looking through smoke,
  clouds or haze, but lack of use validated its removal to reduce weight
  and conserve fuel. The cameras produce full motion video and the
  synthetic aperture radar produced still frame radar images.

The Predator also has a Raytheon built Multi-Spectral Targeting System (MTS).


Did DB Cooper's aircraft land safely with the aft stairs open? I've never seen a 727's aft stairs open, but presumably, based on an Wikipedia image and common sense, they do reach the ground when the aircraft is on the ground. Furthermore, (as I understand it), airliners land with a positive pitch, which means that assuming a level runway, the rear of the aircraft will touch down first. However, this suggests that if the aft stairs of the 727 were open during landing, they would impact the ground during landing and, given the pitch, do more than scrape the ground and cause damage to the aircraft.
However, DB Cooper's jump left the aft stairs open, and (as far as I can tell) it seems that the landing was uneventful besides the stress of having a hijacker potentially on board (although it's quite understandable if no one made any record of it, given there were slightly more important things to deal with).
If DB Cooper's flight did land without damage, why is that—did the 727's aft stairs not fully touch the ground? If the stairs did impact the ground, was there sufficient damage to require repairs?
(I meant this question to be more about the 727 than DB Cooper, but since his was the only landing with stairs open, there wasn't much room for speaking in general terms).

The aft airstair was partially deployed for the duration of the approach and landing.
The transcripts of ATC communications between NW305 and various ground stations are freely available (and a fascinating read). The relevant communications (with Reno) begin on PDF page 87 (numbered 213). Below are the mentions of the airstairs from that point on, with times given in PST, 1971-11-24. I added the text in brackets for clarity.

22:35, NW305: OKAY AH WE'RE TRYING TO MAKE CONTACT WITH [Cooper in] THE BACK [of the airplane] NOW AND AH WE'RE GOING TO GET THESE
STEPS UP BEFORE WE CAN MAKE OUR LANDING...
22:43, RENO: NORTHWEST THREE ZERO FIVE WHAT'S THE STATUS ON THE STAIRS NOW SIR
22:43, NW305: AH WE HAVEN'T BEEN ABLE TO GET AHOLD OF ANYBODY [in the back of the plane] YET UH TRYING TO CONTACT HIM AND THEY'RE STILL
DOWN SO I WE HAVEN'T DECIDED YET AH WE MIGHT COME IN AND LAND WITH
THEM DOWN THERE'D BE SOME SPARKS SO
22:48, NW305: APPROACH AH THREE ZERO FIVE WE CAN'T SEEM TO RAISE HIM BACK THERE WE KIND OF HATE TO WE'D JUST AS SOON LAND WITH THE
THING HANGING DOWN IT ISN'T ALL THE WAY DOWN AND THEN PROBABLY WON'T
HAVE ANY PRESSURE ON IT SO WE HOPE IT'LL (unintelligible) FREE...
22:57, NW305: ...WE'RE NOW MARKER INBOUND AND UH AH WE'RE GOING TO BE LANDING WITH THE AIR STAIR IN THE DOWN POSITION AH WE DON'T SEEM TO
GET ANY RESPONSE FROM OUR FRIEND IN THE BACK
[The aircraft touches down and is taxiing.]
23:03, NW305: SEE ANY SPARKS COMING OFF THE TAIL AT ANY TIME ON AH TOUCHDOWN
23:03, RENO: NEGATIVE NONE AT ALL THE ONLY THING THAT'S VISIBLE ON THE TAIL IS LIGHT AH APPARENTLY ON YOUR RAMP
23:03, NW305: ROGER UNDERSTAND STAIR LAMPS AH STAIR LIGHTS
23:03, RENO: I DO SEE SOME AH SPARKS NOW JUST A FEW AH TRAILING YOU AH AS YOU'RE TAXIING IN
23:03, NW305: OUR AH PASSENGER TRIED TO DISEMBARK
23:03, RENO: I STILL DON'T AH GETTING A FEW SPARKS NOT VERY MANY AT ALL
23:03, NW305: OKAY WE'LL TRY TO SLOW OUR TAXIING HERE AS MUCH AH IT PROBABLY IS DRAGGIN AH

Why did the crew not retract the airstair before landing?
The airstair can only be operated from two positions: one in the main cabin and one on the exterior of the aircraft. It cannot be operated from the flight deck. The testimony of Tina Mucklow, the flight attendant whom Cooper interacted with almost exclusively, reveals that

Approximately four minutes after takeoff, [Cooper] stood up, told [Mucklow] to go to the cockpit and close the first-class curtains, and for no one to come out from behind the curtains.

It should be noted that the airstair was still closed and locked at this point. In fact, it was Cooper himself who performed the deployment:

...he asked her to demonstrate to him the procedure for opening the rear door and extending the stairway. She did this and was under the impression that he understood how to do it. She commented that it occured to her at this time that this was the only function of the aircraft which she had discussed with the hijacker during the time she had been with him which he did not seem to be fully aware of.

Even though before Mucklow left Cooper in the cabin "...she pleaded with him to take the bomb with him and he said he would take it with him or disarm it...", nobody could be sure, so complying with his demand for no one to enter the cabin was the obvious choice. Even after the crew suspected he had jumped, there was still some chance that he was present. That—on top of the clearly dangerous situation of being unrestrained in an airborne jet transport with a door open—compelled the crew to sit tight in the cockpit and land with whatever configuration they could control from there. Indeed, third officer and right-seater on the flight Bill Rataczak stated that

...no member of the crew departed from the cockpit to check on the presence of the hijacker following the arrival in the compartment of hostess Mucklow, who had locked the door behind her.

How did the airstair remain partially deployed on its own?
The airstair is in contact with the tarmac when deployed on the ground. In fact, it's designed to essentially wedge itself against the ground and act as a tail stanchion to keep the airplane from tipping backward during loading and unloading. Early 727s such as N467US had mechanical locks for the airstair in both the extended and retracted positions to accomplish this function.
However, the crew had evidence that the airstair was not locked, as Mucklow "observed the red indicator light go on the [flight engineer's] panel indicating that the stairs had been lowered." On the 727-100, that light would be de-energized only if the airstair was locked either up or down. (On the -200, a green light was added to indicate a fully extended and locked position.) The ATC transcript indicates the captain's later belief that the airstair wasn't "all the way down", so it's reasonable to assume the warning light remained illuminated.
That the airstair didn't lock down when deployed indicates that it never fully extended. It is likely that the air loads simply prevented full extension. The airstair hydraulic actuators were not designed with the strength necessary to overcome a 170-knot airstream, especially on early 727s. The extension was limited by the airspeed and subject to fluctuations with changes in the airstream and the weight of Cooper upon the stair.
The inability to fully extend the airstair in flight was even known on the ground beforehand, as the transcript of communications between NW305 and the airline's base at MSP reveal (I cleaned these up):

18:38, MSP: DON'T KNOW OF ANY WAY TO LOCK STAIRS IN AN INTERMEDIATE POSITION.
18:40, NW305: ...STAIRS WILL OPEN ABOUT 20 DEGREES AT 120 KNOTS. IS THAT ENOUGH FOR AN INDIVIDUAL TO ESCAPE THE AIRCRAFT?
18:40, MSP: WITH HIM ON STAIRS WILL OPEN POSSIBLY ENOUGH FOR HIM TO GET OUT. REMAIN UNPRESSURIZED. BE IN LANDING CONFIGURATION WITH
FLAPS. SLOW TO [APPROACH] SPEED BEFORE TRYING TO EXTEND STAIRS.

As it turns out, the stair could not be opened much if at all at 170 knots during a climb, and the captain had to "have 'er about down to a hundred and sixty knots" and level off at 7,000 feet to get the resistance low enough. It makes sense that a higher angle of attack would cause a greater air load on the door due to the increased frontal area. It also makes sense that the airflow alone would be insufficient at any speed to completely re-close the door due to the geometry of the empennage, the weight of the stair, and some hydraulic damping. Once the door was open, the crew were able to climb again to 10,000 feet and keep the airspeed "in the vicinity of one seventy, one eighty [knots]".
Although the hydraulic actuators would have provided damping, the swirling wakes from the landing gear and flaps—not to mention the aircraft turbulence inherent when flying low and slow over mountains in a storm—undoubtedly wrenched the stairs up and down considerably. Cooper's exit has been romanticized as a high-dive into the unknown, but it was more like trying to exit a springboard during an earthquake, with his own weight just exacerbating the problem. We know as much from Richard McCoy, Jr., a copycat hijacker who survived his jump (at the same airspeed) and was later captured and interviewed:

...[McCoy] stood geared up in the open doorway for a very long time before
descending the aft stairs. It was almost midnight, the sky was black,
and the wind was freezing, yet his hands were sweating. Finally, he
was able to collect his wits, take a deep breath and step outside onto
the stairs.
As he stepped out, the entire stairway dropped two feet under his
weight. Knocked off balance with his 70-pound duffle bag between his
legs, he grabbed the right handrail and wrapped both arms around it,
desperately holding on. The stairs shook and vibrated. The noise from
the jet engines on either side of him was horrendous.

In fact, it was cabin-pressure fluctuations caused by Cooper descending and exiting the airstair that allowed for the determination of exactly when he jumped (8:11pm PST):

Crew reported oscillation of cabin rate-of-climb indicator. This probably due to [Cooper's] weight now on stairs, stairs extended further, resultant effect on cabin pressure.

The FBI's analysis was that "When [Cooper] jumped, the air stairs were forced closed (by outside air pressure) causing an increase in air pressure similar to shutting a car door with the windows up". Although we've established that the door was not forced completely closed and locked, it's clear that the airstair was able to hang somewhat freely in the airstream, its deflection affected by air loads, the weight of Cooper, its own weight, and any dampening provided by the actuators.
What was the risk of landing with the airstair deployed?
The crew knew from the cockpit indication that the airstair was neither down and locked nor up and locked. But they had prepared somewhat for the idea of landing with a deployed airstair before they even departed Seattle:

19:27, MSP: IT WOULD PREVENT ANY SUBSEQUENT TAKEOFF IF YOU LAND WITH [THE AIRSTAIR] DOWN.

Mucklow advised Cooper more than once of this fact, given that Cooper had stated intentions to get to Mexico and that Reno was just a necessary refueling stop along the way due to Cooper's wanting to be flown low and slow.
Landing with a deployed airstair could have a range of consequences that had never been investigated or analyzed, so most likely the airline was playing it safe. At the very least, a detailed inspection would need to be carried out before the airplane flew again. If the stair were downlocked, the results of a landing would depend on what failed first. If only the latch failed, you might get away with just dragging the stair, which would cause some exterior damage but overall that'd be a relatively minor fix. If nothing on the airstair failed, I suppose you could bend the entire fuselage. I'd also worry about bits and pieces of failed components being rocketed around the empennage or into the cabin.
Fortunately, at this point the crew was safe from the worst outcomes because the stair was not downlocked. In fact, as we've seen, the crew knew that even at 120 knots the airstair would not be deployed far enough to strike the ground upon touchdown. That speed is in the ballpark for an empty 727 on landing, but even at a lower speed it's entirely plausible that the airstair did not strike the ground on touchdown, and was only able to fully extend once the aircraft was at taxi speed.
What damage did the aircraft sustain?
Given everything we've covered so far, the damage was probably not extensive. Dragging the stairs along at taxi speed would mean not much more than some sheet-metal repair. Looks like some of the railing paneling sheared away, probably in the air:

There's also the placard found in the forest a few years later that got ripped away at some point during the flight.
In any case, the crew was able to easily deplane via the deployed aft stairs:

23:14, NW305: ...WE'LL GO DOWN THE BACK STEPS AND AH AH WE'LL BE TAKING LEAVE OF THE AICRAFT AND SHUTTING IT DOWN AT THIS TIME...

The fact is simple geometry would prevent landing a 727 with the aft airstairs in the extended position. These stairs are have almost no clearance from the ground when they are extended. Check the relation ship of the tail strike bumper to the profile of the Aft airstair. You simply couldn't complete an approach at a flat enough angle for a successful landing. So maybe the aft airstair were damaged during the landing? Not possible. The 727 being a T-Tail with 3 rear engines is extremely tail heavy. So much so that the rear airstair doubles as tail support structure for the aircraft when parked or loading. Just the weight of the demountable engines are roughly 4700 lbs each, so we're talking 14,000 lbs independent of the T-Tail structure. When powering back a 727 from the gate the most important rule is to never use the aircraft brakes to slow the rearward roll. The aircraft will sit on its tail everytime. All of this is to illustrate how strong the aft airstair structure is on the 727 as well as how critical weight and balance limitations are on this particular aircraft. The conclusion drawn from this information is reports of landing a 727 with the airstair extended cannot be true.


Is there a preferred wind direction for a helicopter in hover? When hovering, how does a pilot deal with wind direction? As when landing is it preferable to point the nose into the wind? Is this a primary consideration for the pilot considering that he may need to maintain visibility on something, such as during a rescue or a news operation?

And is wind direction more of a factor when hovering in or out of ground effect?

In most helicopters, the wind direction when hovering is of concern to the pilot, as is which way you turn when hovering.

The following applies to a single rotor helicopter with the tail rotor mounted on the left and the rotor turning counter-clockwise.  The opposite applies to clockwise rotating rotors and mounting the tail rotor on the left versus on the right would take more pages of text!

  Hover with no wind.

As the rotor rotates counter-clockwise, the torque reaction on the fuselage wants to turn the nose to the right.  The tail rotor "pushes" the tail to the right to balance this torque.  It is by varying the angle of attack of the tail rotor that we can change the amount of thrust from the tail rotor and therefore have yaw control.

The tail rotor is no different to the main rotor, it just operates in the Y axis rather than the Z axis and is subject to vortex ring state.

The vortex from the tail rotor is to the left.  If the helicopter is yawed right, the tail moves left and the tail rotor moves into it's own vortex causing a reduction in angle of attack and therefore thrust.  If the turn is too fast, this reduction can lead to a loss of tail rotor effectiveness.

Also in a no wind hover, the vortex from the main rotor is forced downwards.

All of what follows is for a counter-clockwise rotating rotor and applies to all single rotor helicopters.

  Hover with the nose into wind, but not with enough wind to generate
  effective translation lift.

This state is more or less the same as for a no wind hover and is the easiest (and therefore preferred) direction in which to hover.  Turning the aircraft has the same risk as in a no wind hover in that turning too quickly to the right can lead to loss of tail rotor effectiveness.

  Hover into wind with enough wind speed to generate translational lift
  (let's say about 15 kts)

Now things start to get interesting.  If you turn to the left, the vortex from the front edge of the main rotor is blown backwards by the wind across the tail rotor and causes a decrease in the angle of attack of the tail rotor blades since the wind from the vortex is blown on to the right hand side of the tail rotor.  Therefore, a lot more left pedal is required as the helicopter turns from 0 degrees (relative to the wind) to 270 degrees.  As 270 degrees is reached and passed, the vortex is no longer interfering with the tail rotor and the angle of attack for the same pedal position is increased.  If the same pedal input is maintained, the rate of turn will increase rapidly and if not corrected, can lead to an uncontrolled spin.

If you turn to the right, the opposite happens.  More right pedal (less thrust) is required in the first quadrant of the turn from 0 degrees to 90 degrees since the vortex is blown into the face of the tail rotor causing an increase in angle of attack and therefore greater thrust.  As the nose passes 90 degrees, the angle of attack decreases and left pedal must be added to prevent a sudden acceleration in yaw.

You should be able to see that the amount of pedal required changes as the turn continues and without constant adjustment, a steady turn cannot be maintained and with enough wind, and a pilot who is not quick enough on the pedals, control can be lost.

Now let's take the turn out of the equation and consider steady hovers in wind that is not "on the nose".

  Wind from the left quarter, i.e. 270 - 0 degrees. This is effectively the same condition as that first quarter of a left turn with wind from the front.

This is the difficult one.  Wind is never constant. It is always changing slightly and turbulent.  As the main rotor vortex is blowing into the tail rotor, the tail rotor is operating in a very turbulent and unpredictable environment.  Rapid and constant pedal inputs are required to maintain control.  Any deviation not caught immediately can lead to a loss of control.  It is very difficult to hover with the wind from the left quadrant and is therefore usually avoided.

  Wind generally from the left (a left crosswind)

As the wind is blowing into the face of the tail rotor, its angle of attack is reduced as the airspeed through the rotor increases.  This can lead to the loss of tail rotor effectiveness or even a stall of the blades as the angle of attack exceeds the critical angle.

  Wind from behind.

The primary effect here is the tendency of the fuselage and vertical stabiliser to "weather cock" the aircraft.  It naturally wants to face into wind.  If a yaw begins and is not immediately corrected, due to the effects above, the yaw can increase rapidly and suddenly.  Additionally, the wind is never constant and varies between passing to the left and to the right of the tail rotor.  Therefore, hovering downwind needs immediate and constant corrections to yaw.

  Summary

Hovering into wind is very much preferred and is always chosen unless operations require something different.  Hovering with the wind from the right is the next "most" preferred position with quartering winds from the left and hovering downwind to be avoided if possible.

All of this said, it's a standard part of training to learn how to hover in these conditions and how to maintain constant rate turns.  It does require a lot of learned skill and you must be quick and accurate on the pedals with constant corrections.

Incidentally, early models of the UH-1 were particularly difficult to handle in certain wind conditions and the tail rotor was moved from the right to the left on later models to improve handling.

In a light helicopter with little power reserve, e.g. the R22, hovering in strong gusty winds is an intense part of operations.  I had some close calls when learning how to do this including a loss of control which I only recovered by pulling in power and accelerating into forward flight.  Not good on an airfield with other aircraft operating since my "low hours brain" focussed only on regaining control.  I am ashamed to say that looking around took second place but I did learn an important lesson and with hindsight, the right thing to do would have been to land and discontinue the flight as the wind got more gusty.

The best situation when hovering is for there to be little or no wind. There is no "preferred" way for the wind to blow relative to the helicopter unless there is a certain place you want to see. However, because of their designs, helicopters will tend to "weather-cock" in the direction the wind is coming from due to the CP-CG relationship.

I found this FAA doc on helicopter handling with a bit more stuff: https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/helicopter_flying_handbook/media/hfh_ch09.pdf


Refuelling an airbus to maximum The airbus A350 aircraft when being refuelled seems to drop when the wings are filled.How  much is the drop from empty to full.Thankyou

That’s going to depend on a lot of things including how well serviced the struts are, what the existing payload on the aircraft is and whether the aircraft is parked on any sort of grade.

I don’t work the A350, but I work other heavy aircraft and I’ve had them “settle” quite a bit when putting on a full fuel load.


How can I create a map of all paths of flights incoming to an airport in a given day? Is there any where I could find a map overlaid with the paths of all flights that came into a given airport on a given day?

I've found a lot of maps that show the current location of all flights, or the path of a single flight, but I haven't been able to find any that have the paths of many flights at once.

I don't really want to scan through every flight manually, but if I could see all of their paths I could pick out the ones that have interesting tangents for further study.

Background: I recently moved in to an apartment near an airport. I enjoy watching the flights come in, but one of my new roommates is less thrilled. He remarks that some of the flights seem to be pointed directly at our building until their final turn, so if the pilots were somehow incapacitated, we'd be in trouble. I think that's geometrically incorrect, but would like to prove it.

Well you didn't state which airport you are interested in but obviously you only want data for a single airport.

You might want to look into a noise abatement reporting system. For instance, London Heathrow maintains the great website Webtrak (https://webtrak52.bksv.com/lhr4) to communicate with the pubic about changing SIDs, STARs and noise levels. (They already have much of the TMA over the heavily populated area, and they want to add another runway)

Start with the FAA on-time dataset:

https://www.transtats.bts.gov/DL_SelectFields.asp

This is only for domestic flights but a good start.


Are the current seat belts used in commercial airlines safe enough? I find myself thinking often, if the seatbelts in airlines are designed just to keep the passengers in seat or to really act as a safety belt like in cars, because in cars which go at 300kmph speed, you have the 5 point seat belt. Why isn't similar approach used for airlines, where the risk is too high.

Plus articles like these, suggest heavier / obese passengers are at more risk.

For a proper answer we first need to define what "safe enough" is. If you want a significant reduction in risk over current standards, improving the restraint will not be enough.

Your observation is absolutely correct: The lap belt is the minimum the airlines get away with, and you would be much better protected in some kinds of accident by a proper 5-point harness. But fitting the harness alone will not achieve much: To stay in place in a crash, all seats need to be reinforced, so they can tolerate the increased loads at the shoulder belt attachment points. This will add weight and cut into the profits of airlines, so it will only happen when it is mandated.

Please read this answer for more details. It concerns GA aircraft, but much applies to airliner seats as well. The better the restraints are, the more deceleration load can be survived. Note that the points in the Eiband diagrams shown in this answer are from tests with additional leg, chest and arm restraints. If all you have is a lap belt, you might probably be able to tolerate only half as many gs.

The better alternative to a 5-point harness would be to turn around all seats. This would help most to reduce injuries and improve chances of survival in a crash landing.

Now I have to contradict @FreeMan: While the brace position will put all the load on a small strip around a person's hips and lets the arms flail forward, a properly secured torso can take 10g for a duration of more than a second and up to 40g momentarily without ripping the head off. See below the famous sequence of Dr. John Stapp in a ride on his rocket sled "Sonic wind":

Dr. John Stapp in a deceleration test (picture source)

He clearly had his head bobbing about, but even though he lost dental fillings and suffered hemorrhage in his eyes, the head stayed intact.

In the end, all what the lap belt is really good for is to keep you in your seat with negative acceleration due to gusts. This is by far the most common situation when a restraint is needed. The classical brace position (torso over legs, head down) is impossible anyway in economy class due to the ever reducing seat pitch.

Aircrafts' seatbelts are for security reason. And yes, security while flying is "just to keep the passengers in seat" in case of a void or, on ground, in case of a bump or the plane leaning.

Apart from that cases, there is no need for a complicate 2/5/10k point system in an impact against a mountain: you will be just plain dead anyway.


Is there a list of part 121 and/or 135 operators? While looking into this question, I found a list of certificated air carriers on the US Department of Transportation website (there's a list of commuter air carriers too). But, the list doesn't say if each one operates under part 121 or part 135, which the DoT seems to consider an FAA question anyway:

  As noted above, the economic authority issued to air carriers by the
  Department is separate from the safety authority (commonly referred to
  as Part 135 or Part 121 Operations Specifications) granted to them by
  the Federal Aviation Administration (FAA).  For safety authority
  application procedures and related questions, air carriers should
  contact the appropriate FAA flight standard district office based upon
  the geographical location of the air carrier

The FAA site has a lot of information about part 121 operations, but at least as far as I could see there's no list of 121 or 135 carriers anywhere on their site.

Is there a list somewhere of current part 121 and/or 135 operators?

I have not found a list, but you can search for an airline here.

There is a link on the page to definitions of the terms. Basically, "domestic" and "flag" are FAR 121 operations, and "commuter" is FAR 135 operations.

There is also an unofficial database here that will tell you which FAR an airline operates under.

Here is a list of every Part 135 aircraft registered and their operators.
https://www.faa.gov/about/office_org/headquarters_offices/.../135Aircraft.xlsx


Why are there no blended-wing passenger airplanes in operation? Blended wings are more beneficial when it comes to fuel efficiency increase and noise reduction. However, no manufacturer has decided to produce these airplanes for major airline operation so far. What are the inhibiting factors in the industry for not using this configuration?

From what I can guess:

It is a complete new configuration with low experience on it. High risk.
Aircraft will be in VLA sector (>500 passengers), a sector not very attractive nowadays.
The 90 seconds evacuation limit needs to be observed.

All studies which so far showed an advantage for blended-wing bodies (BWB) were flawed.

The trick mostly used is to compare an existing airliner with a hypothetical BWB which uses equally hypothetical engines of improved efficiency, like what could be expected 20 years into the future. This masks the inefficiency of the BWB concept and makes the combination come out ahead.

The BWB will always have more surface area than a comparable conventional design. This translates into more friction drag and more skin mass, which more than offsets any advantage given by the bigger wing root (which helps to reduce wing spar mass). If you like real data, use the Avro Vulcan as an early BWB and compare it to its contemporaries. Note that design attempts for an airliner based on the Vulcan (type 722 Atlantic) went nowhere.

Why are these BWB studies published? The author gets more attention when he/she claims a "revolutionary breakthrough" than when he/she is more honest and admits that the concept is a dud. Even Boeing or Airbus like to publish BWB studies, so the public gets the impression they are ahead of the competition. It is sickening to read such academically dishonest studies - you need to spend time to dig to the bottom of the thing and to unravel the plot; however, once you have done this a few times, they all become alike. But compared to studies made 60 or 80 years ago, where the author factually lists what he did and why it didn't work out (which is the only way you can learn something), those modern studies are a waste of time.

The first, in depth study of the Lifting Fuselage Configuration in 80 years from David Singg at the University of Toronto shows the LFC has twice the "fuel burn reduction" of the BWB/HWB compared to the tube and wing.  Vindication of the work done by Texas born Vincent Burnelli from 1921 to 1964.  Google Burnelli aircraft.

Report link...  http://oddjob.utias.utoronto.ca/~dwz/Miscellaneous/ReistZinggJofA2016.pdf

The BWB was a good step forward from the tube and wing configuration but now, the most efficient and useful design has emerged.  Even this will not guarantee production.  Just as the BWB has not been accepted because it's too radical a design, the Lifting Fuselage will take years to win acceptance.  More research to come.


What is this ring-shaped device behind this DC-8's jet engine? What is this ring-shaped device behind this Douglas DC-8's jet engine?

(YouTube)

(airliners.net) Ejector on the Rolls-Royce Conway of a DC-8.
It's called an ejector.
Introduced in c. 1958 by Douglas for their DC-8, it is extended during takeoff and landing, and stowed during the flight because it increases the drag at high-speed flight.
In the extended position it acts as a noise suppressor, and it also reclaims thrust that has been lost due to the corrugated exhaust nozzle. Doors within the ejector also close to provide thrust reversal.
(Flight—PDF)

Two views of the device developed by Douglas to suppress the sound and reverse the thrust of the DC-8. The corrugated exhaust nozzle is combined with a cylinder which extends beyond the nozzle during take-off. This "ejector" is claimed to reduce the sound level by 3-4 decibels and increase the thrust sufficient to offset the loss caused by the nozzle. The indentation near the forward lip of the ejector is one of the two doors which close to form a thrust brake. Noise level with the ejector ring and nozzle combined is said to be reduced by 9-12 decibels.

(Images from aamalebourget.fr and flightglobal.com)
The image on the right shows a similar installation on the BAC One-Eleven with the positioning screw-jack mechanism.
(YouTube) Factory testing of the ejector on the DC-8.

They appear to be thrust reversers, similar to what you can see described in this book, and also similar to what is shown in this video of an early Boeing 737.

From what I've seen discussed in various forums the Boeing 707 had two thrust reversers; one for the cold section of the engine (example) and one for the hot section. As far as I can tell the second one was only used on a few early aircraft, as the control mechanisms required quite a lot of maintenance due to the high temperatures from the exhaust, but haven't found good sources to confirm this.


Can weather groups contain multiple descriptors in a METAR? I understand that a weather group in a METAR is composed of qualifiers (intensity, descriptor) and the weather phenomenon: precipitation, obscuration and other phenomena.

My question is can weather phenomena have multiple descriptors? Eg: Are TSSH or TSSHRA valid in a METAR?

No, a METAR descriptor can only appear once in a METAR or line of a TAF. That is because METARs and TAFs report weather phenomena in the format of

[Intensity][Proximity][Descriptor][Precipitation][Obstructions to Visibility].

Thunderstorms, for example, are one descriptor; therefore, thunderstorms (TS) will only appear once.

Intensity

Applies only to the first type of precipitation reported. A “−” denotes light, no symbol denotes moderate, and a “+” denotes heavy.
Proximity

Applies to and reported only for weather occurring in the vicinity of the airport (between 5 and 10 miles of the point(s) of observation). It is denoted by the letters “VC.” (Intensity and “VC” will not appear together in the weather group.)
Descriptor

These eight descriptors apply to the precipitation or obstructions to visibility:

TS = Thunderstorm
DR = Low drifting
SH = Showers
MI = Shallow
FZ = Freezing
BC = Patches
BL = Blowing
PR = Partial

Precipitation

There are nine types of precipitation in the METAR code

RA = Rain
DZ = Drizzle
SN = Snow
GR = Hail (1/4" or greater)
GS = Small hail
PL = Ice pellets
SG = Snow grains
IC = Ice crystals
UP = Unknown precipitation

Obstructions to Visibility
There are eight types of obscuration phenomena in the METAR code

FG = Fog
HZ = Haze
FU = Smoke
PY = Spray
BR = Mist
SA = Sand
DU = Dust
VA = Volcanic ash

Your question brought to my mind the following question. Since TS and SH are both descriptors that indicate the intensity of precipitation, can they both exist simultaneously? Sort of like when does fast become slow? Or, in the case of the weather phenomenon RA, at what point does gray become black or white instead of both? A quick google search turned up the following article from a local meteorologist.

Thunderstorm, Thundershower...What's the Difference?
March 16, 2001 at 1:51 AM EST - Updated July 1 at 10:45 AM
What's the difference between a
thundershower and a thunderstorm?  That is
a question that has a technical and
psychological answer.  Technically, any
cloud producing lightning is considered a
thunderstorm, even if there is no rain
falling.  The National Weather Service
reports it as "TS" in their hourly
observations at the airport.  TSRA means a
Thunderstorm with a Rain Shower, which is
what most of us think of when we think of
thunderstorms...Thunder, Lightning and
Rain.  But, when meteorologists (Mainly on
TV and Radio) want to indicate that
thunderstorms with light rain are expected,
they will call them Thundershowers, even
though there is no technical abbreviation
for a thundershower.  It's just a good way
of taking the much stronger sounding word
"storm" out of the mix, and adding the
gentler sounding description of "shower".
Properly, thunderstorms have either no rain
(TS), light rain (TSRA-), moderate rain
(TSRA), or heavy rain (TSRA+).  But, for a
viewer, it's tough to explain all that, so
we generally talk about weaker
thunderstorms as thundershowers, even
though there is "technically" no such
thing.

With this type of argument, TS and SH remain completely separate (eg. TSRA vs. SHRA). The + or - would be added to indicate intensity.


How does turning a small plane by opening the doors work? I've just watched a video of a small Cessna turning not with ailerons or rudder but by opening its doors. They said that the door acts like a rudder, but in the video one of the guys opens the left door and the airplane rolls right. That doesn't  make too much sense to me...

I've been searching on the internet and I found a different explanation which  stated that the airflow stacks up below the wing because of the door and then an over-pressure is exerted making the airplane roll into the opposite direction, in this case to the right (which is what can be seen on the video). Can anyone confirm this second explanation?

And if I wanted to roll a Piper or any other low-wing aircraft by using the doors, what would the airflow's behaviour be?

The second explanation is right. The blocking effect of the door below the wing will force more air above it, so suction and lift above get higher. Of course, the blocking effect will also increase pressure locally on the lower side of the wing.

If you do the same on a low wing aircraft, it will roll to the opposite direction. Now the door acts like a spoiler and reduces lift.

Generally, such a one-sided creation of a disturbance will upset the aircraft and will make it roll and yaw in an uncoordinated manner. And the "rudder" explanation is wrong - a rudder creates a sideforce at a distance to the center of gravity, while the door is pretty much where the pilots and the center of gravity are. The better explanation would say that the door acts like a spoiler, and those are used routinely for roll control:

in airliners
in unmanned vehicles

An open door in flight on a high-wing aircraft will act like a flap. It will increase the drag on that side, both vertical and horizontal. The aircraft will slow down and the increase in surface area on the left will cause the right side to drop. It depends of course on the type of door and aircraft. On a low-wing craft, opening a door will just increase the drag since the vertical presentation will be unchanged.


How do pilots fight jet lag? Jet lag, medically referred to as desynchronosis and rarely as
  circadian dysrhythmia, is a physiological condition which results from
  alterations to the body's circadian rhythms resulting from rapid
  long-distance trans-meridian (east–west or west–east) travel on
  high-speed aircraft. For example, someone travelling from New York to
  California feels as if the time were three hours later than local
  time. (Source)

As pilots often have to travel between multiple time-zones, especially during long haul flights, with as much as 12 hours of difference between them, how do they fight jet lag?

Crew members each have their own approach to this but in general on the long haul routes, as a pilot you have at least 24h layover, so you can catchup on some sleep, walk outside for a bit (depending on the local time) and then sleep some more so you're fit for the next flight back home. At home you have a couple of days off to recover from the trip.

On the very long flights 13h+ the pilots are with at least 4 so you can do a quick nap on board as well.

As a passenger I cope with the jetlag by looking at the arrival time, do I arrive in the morning I will try to sleep on the plane, will I arrive in the afternoon the I will try to stay awake and go to bed early. By doing so I wake up easily next morning and do not feel jetlagged.

Usually, crew member should follow the local time (base/hub time) for their routines on ground, and if necessary, some of the take melatonin to synchronize the circadian rhythms.


Does the sterile cockpit rule mean flight attendants could not inform the pilots if a passenger is in the lavatory while on final? Context:
I've seen this interesting question just the other day, asking what would pilots do after receiving this information while on final:
either go around or continue with the landing.

However many others mentioned the Sterile cockpit rule under 10,000ft. Meaning that they could not discuss this issue.
So what would this mean exactly? The flight attendants could inform the pilots but they can’t respond?? Or the FA’s just can’t/won’t inform the pilots about the situation at all?

"Sterile Cockpit" refers to the concept that pilots should not discuss anything not related to the flight during certain phases of flight (often defined as below FL100).

A passenger occupying the lavatory while the flight is on approach and passengers are supposed to be in their seats definitely does have an impact on the flight, so it does not fall under the "sterile cockpit"rule.

You have got the answer before but I would like to add that some airlines have more restrictions on talks between cabin and flightdeck.
For example, in my airline after the call from flight deck to the cabin for cabin crew to be seated for landing, there should be no call from the cabin until landing, even if they spot a fire or something else.


Can ATC tell if aircraft is being flown manually? Was wondering if ATC can detect if aircraft is being flown manually vs. autopilot and if that affects their clearances given out for surrounding aircraft?

More specifically, can they tell through ADSB signal or just by observation (holding flight level, turn rate, correction for wind, etc)?

I would imagine that in high winds/bad weather non-AP operation would need to be better isolated from other aircraft?

No, the air traffic controller cannot see the whether the autopilot is used or not.

However, in the Mode S radar and ADS-B protocols there are messages defined that contain state of the autopilot. Currently there is no requirement that this data is provided by the aircraft, but some aircraft/transponders do provide the information nevertheless. The data is not displayed to the controller though.

In some control centres the aircraft's Mode Control Panel / Flight Control Unit Selected Altitude can be displayed to the air traffic controller. The information can be used to reduce Level Busts.

From observations of the radar track it is difficult to tell. A competent pilot will be able to maintain altitude and heading in such a way that it is difficult to see the difference from an autopilot at the resolution of the ATC display.

There are circumstances where the pilot is required to use the autopilot, especially to keep separation from other aircraft. In Reduced Vertical Separation Minima (RVSM) airspace the vertical separation is 1000 ft between Flight Level 290 and FL410. The aircraft must be flown using the autopilot in this airspace to ensure the flight levels are adhered to strictly.

The autoPILOT is not for ATC's convenience. They neither know nor care if it's on, off, or trailing behind the airplane on it's cables. All ATC cares about is that the transponder works, and even that isn't a requirement.

ATC may suspect something is amiss if the aircraft is not holding heading or altitude very well, but if ATC notices this we are well into a major problem. Either there's a major malfunction onboard or the plane is no longer under the control of a competent pilot. Any pilot who passed their commercial can hold heading and altitude just as well as the box - I have zero formal instruction and I can hold a Cessna on course to the point where no one will notice.

In cases where the plane is fine but the crew has a major malfunction (like dying, à la Payne Stewart) then ATC will consider what mode the autopilot is likely in, as that will tell them where the plane will probably be when it runs out of fuel. (If it's turned off, the discussion will never get to this point on account of the plane already turning into a lawn dart)


What are these lines on the fuselage of a 747? Have a look at this picture:

It's from Airliners.net (though I've modified it a lot) and shows some lines on the fuselage. What are they? Are they Lightning Diverter Strips like in this question ?

No, they are just the boundaries between skin panels. See below for a picture of the 747-8 fuselage during assembly.

[

Boeing 747-8 front from side (picture source)

And this is how the panels for the cylindrical section look like before they are joined:

Boeing 747-8 fuselage panels. The original picture (source) is named "wing panel skins", but these are really fuselage parts.

These lines are skin laps. The vertical ones do not overlap, the horizontal laps overlap by three rows of fasteners.


Which part of aircraft is contributing the most weight of airplane? Which part of the aircraft contributes the highest portion of weight?

Note: we had argument that, wires connecting the avionics systems are the major contributors of aircraft weight. Due to some issues with optical fibre technology this is not been used in aviation yet. So my question arises as mentioned above.

Aerospace Engineering e-Mega Reference shows the following table for two aircraft (the large commercial jet, the B747-100, and the military jet, the C-5A). You can see that it differs quite a lot between the B747 and the C-5 already, so it's hard to give a definitive answer for all aircraft in general.

Also, it depends a lot on how you break down the components, for example, here the Nacelle and Propulsion system are shown separately, but if you combine the two (and some others as is done in the dry engine weight, I think) things could change.
The Aerospace Engineering e-Mega Reference points to Beltramo as the source for the numbers. Perhaps you could find some information there about what belongs to which group.

However for both aircraft, it can be seen that the Wing and the Airframe are significant contributors (and for the B747 furnishing is also a large part of the weight)

I think they included all the wiring in the Avionics part (that would make sense to me), but still it is a relatively small part of the total weight.

If you mean by part of aircraft it will be the landing gear.

But if you mean what other stuff add weight you have the electronic entertainment system that adds alot of wires and cables which add weight to the airplane but with no operational use for the airline its only to entertain passengers.


Why does flight training usually start with (unsafe?) propeller planes and not with (safer?) jets? I live in the UK and would like to learn flying jets, but most courses seem to start with propeller planes.
Not sure if this might be a misconception about the safety of different aircraft types, but I remember having read or heard somewhere that small propeller planes are, well, less safe than jets; maybe because they are more fragile and less powerful than jets when it comes to bad weather and are also difficult to recover from dangerous situations... not sure and cannot find the reference for now.

But also doing a quick search for popular aircraft types, the propellers like Cessna seem to have huge numbers of crashes/incidents compared to jet engine aircraft.

So the question is - why are propeller planes favored in training e.g. for the Private Pilot License? Is it simply because they are cheaper and wouldn't be such a huge loss of they crash?

Are there any alternatives where I could start with a jet engine?

Light Propeller Aircraft, if flown within their design limits, are just as safe as jets. If you do a proper and thorough daily inspection, you are far less likely to suffer any form of mechanical failure in the air. In saying this, the majority of all crashes, be it in a Jet Powered Airliner or a Propeller Driven Light Aircraft are caused due to pilot error.

You start out learning in a light single as:

They are lighter, and slower and can usually take the beating handed out by inexperienced pilots, this being:

Hard landings
Slipping onto the runway
Just hammering the day lights out of the engine.

Jet Aircraft are extremely expensive, and generally fairly heavy. Inexperienced pilots generally pay AU$80,000 for a Commercial Pilot License (In Australia) which qualifies you to fly single engine aircraft not over 5,700kg under the VFR by day. This is an absolute, level entry qualification looking for a job (most people will find that they at least also need a night VFR rating or a MECIR), so to add the cost of doing training in a jet on top of that, even if it is just for PPL, will be massive.
Jet Aircraft will be insured to be flown by pilots who have an amount of total experience and experience on aircraft/engine type. So, again, unless you're willing to pay the massive excess and premiums to be put on the insurance, you're going to have to fly a prop.

Now, you have identified that a lot of crashes are light singles (i.e. Cessna). This is because generally, these aircraft are not flown with the same discipline as a Jet Aircraft. Also, the pilots flying them are generally lower hour pilots who do not have as much experience (again, this is a generalisation, not an exact figure of the total community).

As for starting in a Jet, I honestly doubt that there is any flight school on the planet that will allow you to start training in a Jet (Even Fighter Jet pilots start out flying tiny little single engine aircraft).

Prop planes have a longer glide ratio. (they fly farther when the engine quits. ) My father would have said jets have the glide path of a rock, the slower they go, the faster they come down!  Jets are also much more complex and sometimes simple is safer to maintain as well as fly.


How can I correctly calculate fuel for a Cessna 152? I'm learning to fly in a C152 and I've found the fuel calculation to be a little ambiguous. Based on information from my instructor, Internet and the Cessna 152 Information Manual (1980), I've home cooked the following formula and wanted to run it by the community for some verification.

I hope this is an appropriate use of this forum and please excuse my newb-ness. Here's my formula:

Fuel Required =
    5.6L unusable +
    5L run-up and taxi +
    24L/hour flight (rich) +
    18L (45 minute) reserve

Based on this formula, a one hour lesson conducted in the training area and below 3,000 feet AMSL requires a minimum of 52.6 litres in the tanks, calculated as follows:

5.6L unusable + 5L run-up & taxi + 24L flight + 18L reserve = 52.6L total

Or 26.3L in each tank. Since we're measuring fuel by the surprising method of dipping a stick in the tank, I'm realistically looking for around 25L per tank, and maybe topping it up to 30 per tank to be on the safe side.

Is this correct and reasonable?

The short answer is: Yes, your calculation is reasonable.

Fuel consumption values are not an exact science, they are average values and rounded in many cases or based on pilot experience. Using 24L/hr in your example for traffic patterns is the right assumption, as you will most likely remain in rich configuration. Even if you lean a bit within the pattern, you would not gain enough fuel efficiency to offset these 24L/hr.

Your 5L run-up and taxi obviously depends on the airport you are based at or use the formula at. If this value was your calculation for a smaller airfield, you might need to adapt your formula when flying to larger regional airports or airports with high-traffic, where your taxi time could be significantly longer.

Be reasonable however with topping up your values. Going from 52.6L to 60L is the equivalent of 5.3KG, which you will need to consider in your weight and balance calculation.

Normally, the practice in my experience is to fill the tanks in all cases to minimize the situations in which fuel starvation would be possible. For this reason, in the United States most trainers are rented wet. Exact fuel calculations usually are only relevant when flying cross country, and even then using generous reserves is a wise practice. During a lesson there are usually lots of unplanned activities, like the ole 30 minute run-up, waiting on the taxiway to take off behind 3 other aircraft that have some kind of problem, and in-flight distractions, so cutting it close on fuel is a bad idea.

A second issue is that if you fill the tanks only for what you need, any additional rentals will each have to fill the tanks, too, which can cause delays and throw off the rental schedule. For example, let's say the C152 is rented 4 times that day. If each pilot only filled the tanks for what he/she needed, then the fuel truck would have to come 4 times. Sometimes it takes a while for the fuel truck to arrive. If you need to taxi to a pump, that is another delay.

For all of these reasons, the normal practice for a student is to fill the tanks. If you are the owner/operator of the aircraft, you may choose to parsimoniously load the fuel you absolutely require, and save some money, but it does not sound from your post as though this is the case.

IMPORTANT CAVEAT: Overweight

If the aircraft would be overweight if you were to fill the tanks, then the above advice obviously cannot be followed. In that case, assuming it is a rental, the logical thing to do is two computations: your estimated need (which are already doing), and the maximum possible. If the need is greater than the maximum possible, you will need to change your flight plan. If the maximum is significantly greater than the need (enough for two or more lessons), then you should fill to the maximum, so that the next student does not have fill the tank, too. If the maximum is only moderately over the need, and the next student will have to fill it anyway, then you may as well fill it just to your calculated need.

As far as your calculations themselves are concerned, they seem right, aside from the use of the evil French units of measure.


What is it called when an airplane has to circle because it can't land? Sometimes, a plane is required to circle around an airport repeatedly because for whatever reason, it is not able or permitted to land just yet.

This state in which a plane is stuck in the air in this way has a name, what is it?

That’s a VFR traffic pattern.  It’s a type of pattern which allows a fixed wing aircraft to transition from an arrival to sequencing for an approach to landing under visual flight rules.  Airplanes practicing takeoffs and landings will enter and exit the pattern from the runway using the departure and final approach legs.  Aircraft can also continue to hold over the airport in the traffic pattern for traffic separation, right of way, etc.

Other possibilities could be holding patterns, though these are generally not flown directly over an airfield, marshaling patterns or simply an aircraft practicing ground maneuvers over a non-towered airport, though this practice is frowned upon for safety reasons.


Can the A380 ferry an extra engine, like the 747? A useful little quirk about the 747 is that it can ferry a fifth engine on the wing, for when another aircraft is stranded somewhere in the world.

Does the A380 have the same capability? If not, how would an airline manage an aircraft needing a new engine whilst away from a maintenance base?

One of the main reasons the 747 was given the ability to ferry an engine was due to the lack of large cargo aircraft available at the time.

Don't forget the 747 was a major game changer when it came out, it was designed to replace the 707/DC-8, and was almost twice the size of these aircraft. As a result, there just wasn't anything available to transport a 747 engine by air if needed.

This was a major problem that had the potential to affect sales of the aircraft, and so they had to find a solution to this. It wasn't until the 747 began to be introduced as a cargo carrier that it was possible to transport these engines by air, in the hold of an aircraft.

With the introduction of the A380, there was no need to add engine ferry capabilities, as large cargo aircraft were common enough to transport them.

747 aircraft can still have the 5th engine hardpoint installed as an option, even on the 747-8. Many foreign carriers that use the 747 still use this option if they don't have a huge spares network. Imagine the issues trying to get a GEnx engine from main MX base in Australia to London or LAX. It just makes sense to bolt the spare on another passenger flight and fly it there. The A380 doesn't have this ability.


What is this very distinct humming noise coming from the IAE-V2500 engines of the A320 during taxi? So I am a huge fan of the A320, and in a less broader sense, the A320 with IAE-V2500 engines. Arguably the greatest engines in the industry with the greatest sound. However though, I've had a question that I just can't seem to have answered so I'll ask here. If you're sitting inside an A320 with IAE-V2500's and you're taxing out to the runway, you here a very distinct humming noise coming from the engines. What I find confusing about this noise is that it sounds very different on the outside as I have spotted the A320 with V2500's in person, and the idle/taxi sound outside of the aircraft sounds very different from the inside. You can find the sound I'm talking about at timeframe 7:42 until takeoff (taxi) in this provided YouTube video:

Thank you all so much! -Niko

I don't think there's anything particularly special causing that sound, it's just how the engines sound.

Inside the airplane you're heavily insulated from exterior sounds, so you're not going to hear much of the airflow and fan sounds from the engine.  You're mostly hearing engine sound that travels through the airframe itself, the turbines primarily.

Outside, the engine sound is dominated by the airflow and fan noise.

I think this is the sound of combustion, as for example it is always the first sound that gets higher in frequency when fuel flow is increased (or engine spools up). Furthermore, the sound is more audible when sitting just above the wing, as this part is quite close to the combustion chamber, so combustion can be heard. It also makes sense as combustion to me should have a sound that is closer to humming than the sound of a mechanical whine such as when the fan spools up.  Additionally, when an engine starts up, it first spools up using the bleed air until a certain rpm where a rumbling sound starts to be produced and gets higher in frequency until it becomes like the hum we are concerned with here. Apparently thats the sound of combustion being introduced.
Not sure though. I’m just trying to make a case here, so don’t take my word.
On a side note, I also like listening to that humming sound, especially when sitting in front of an iae v2500. The cfm56 also has a similar humming sound on both a320 and b737.


How high do they cut the grass on airports? I've read that they try to keep it short. But on other sites and documentaries, it is said that they have to keep it long so that the birds don't look for food. Which is correct: short or long?

It depends on the type of bird and mammal species in native to the area and also the type of grass used in turfing; some of them may not survive if mowed very closely. FAA's Wildlife Hazard Management Manual concedes:

  Species-specific responses may be expected.  ...  Airport managers
  need to work with airport wildlife biologists to determine what species of concern in regards to aircraft safety are in their area and what the habitat needs are for those species.

For most airports, FAA recommends a height of 5-8" of grass.

  Considering bird, mammal and vegetation limitations, mowing at least monthly at a target of 5 - 8 inches may work in many airport environments as
  part of a wildlife hazard management program. ... Mowing at 5 - 8 inches should also reduce
  small mammal abundance.

It is very important to authorities keep the grass cut, as we can see at Cork Airport (courtesy of youtube).
Doing this, the airport signs can be seen clearly by the pilots, avoinding mainly runway incursions, and also keeping far, as much as it can, the birds and their nests. This previous measure sometimes does not work as we wanted, but it might help a lot decreasing the bird hazardous airside.
After cutting the grass, the ground personnel will perform a runway inspection to clean it from debris.


Are children safe when seated in lap during a flight? We would never consider putting an infant or toddler into a car without a carseat, but we don't hesitate to do exactly this when getting onto a large airplane.

If you aren't aware of the concept of a lap child, this is a child, typically under 2 years of age, who can board an airplane without an assigned seat and must be held by a parent/guardian for the duration of the flight (including the takeoff and landing). The only safety consideration is that the lap child must be seated in a row with adequate O2 masks in case of depressurization (some rows have more masks than seats).

I have always considered this to be an unsafe practice, but have never had data to back that up. It seems to me that holding on to a 20 lbs child when subject to strong turbulence or unexpected maneuvering would be difficult. While not common, adults are occasionally severely injured in these events but I've never noted a lap child being hurt.

Does anyone know of instances where a lap child was injured during a flight? I'm not interested in instances where everyone is hurt but rather instances that having been secured in a car seat would reasonably have prevented the injury.

Your instincts are correct, or at least the NTSB agrees with you - they don't like the idea of "Lap Children" on aircraft, and they've come out and said as much in this Safety Alert.

They reiterated that position again in a 2010 letter to the FAA which includes a number of incidents from NTSB investiations, including:

  … on July 19, 1989, United Airlines flight 232 crashed during an attempted emergency landing at Sioux City, Iowa, after the fragmentation and separation of an engine fan disk. Of the 296 airplane occupants, 111 were killed, 47 received serious injuries, 125 received minor injuries, and 13 were not injured. Four children, ages 11 to 26 months,17 were aboard the airplane and were being held by adults. A 23-month-old child was killed, and the other three children received minor injuries. The parents of the four lap-held children were instructed to place their children on the cabin floor and hold them in that position while the adults assumed the protective brace position. After the accident, three of the parents reported that they were unable to hold onto their children during the accident sequence.

and

  … USAir flight 1016 in Charlotte, North Carolina. The flight crew decided to continue an approach into severe convective activity and was executing a missed approach when the airplane collided with trees and a private residence near the airport. Of the 57 airplane occupants, 37 were killed, 16 received serious injuries, and 4 received minor injuries. Among those occupants who were killed was a 9-month-old child who was held by her mother on her lap. The child’s mother survived the accident but was unable to hold onto her child during the impact sequence, and the child struck several seats. The NTSB believed that the child might not have sustained fatal injuries if she had been properly restrained in a child restraint system.

Granted both of these were pretty severe accidents, but the NTSB investigators found that the lack of restraints was potentially a major contributing factor to the injuries of children on these flights.

In that same letter the NTSB also notes that unrestrained children are not just a hazard to themselves in a crash:

  Passengers are required to securely stow all carry-on baggage during takeoff and landing because of the potential risk of injury to other passengers in the event of an unexpected hazardous encounter. However, passengers are permitted to hold a child of equal size and weight in their lap. When children under 2 years of age are not required to be restrained for their own safety, the safety of their fellow passengers also becomes an issue.

See here for more NTSB pronouncements on the subject of child safety in transportation.
They even have some excellent videos and simulations showing restrained versus unrestrained children.

We would never consider putting an infant or toddler into a car without a carseat, but we don't hesitate to do exactly this when getting onto a large airplane.

Car travel is far more dangerous than airline travel, so flying through turbulence while twirling your infant over your head blind-folded is safer than driving (sans blind-fold) with your baby in a fancy car seat.

Also, I live overseas and rarely see children in car seats here (they're usually on their parent's lap on a motorbike). While this is probably more dangerous than using a car seat, the safety practices Westerners take for granted are rare and not considered in most of the rest of the world. Similarly, American school buses usually lack seat belts. There are risks many families are willing to take that may be anathema to others.

  It seems to me that holding on to a 20 lbs child when subject to strong turbulence or unexpected maneuvering would be difficult.

In my experience, this is not difficult. My love for my 20-pounder is far stronger than any turbulence. I do think people should self-assess when making their flight preparations; if they cannot handle turbulence+20 lbs, then they should buy a separate ticket and bring the appropriate "carseat" for the flight.

Hope this helps!


Why are the lights inside commercial airplanes turned off during take off and landing? Before landing and taking off, I notice the lights inside commercial aircraft are greatly reduced. I don't buy the explanation of power saving in case full thrust is needed as nowaday lights don't need a lot of energy and the crew says we can use the smaller reading lamp to continue reading. I suppose this is something to do with security but I don't understand what.

This is for safety reasons.

Take-off and landing are the two most critical phases of flight and thus, every additional step to ensure survivability, be it even just adjusting the light, is taken.

The interior lights or cabin lights are adjusted to match the exterior environment, so that in case of an emergency, especially if the interior lights fail, your eyes are already accustomed to the light setting and you do not require additional valuable seconds for adjustment to a possibly darker or brighter environment. The lights are usually adjusted at dusk, night or dawn to match the exterior environment.1

If the cabin lights do not fail during an emergency, the dimmed light also makes it easier to identify the "EXIT" signs which illuminate and make the guidance lighting on the floor easier to follow. The bright emergency lighting is more prominent to identify when the cabin light is dimmed, saving valuable seconds as the aircraft is evacuated.

This also ties in with having to raise the blinds on the windows. The blinds need to be raised during take-off and landing irrespective of the outside light situation, however, with a darker cabin, any outside light source, especially from fires or other hazards is easier to identify by the crew, making the decision process of whether one side could be inappropriate to use for evacuation faster, e.g. fire on port side --> no evacuation on that side.

The blinds are therefore raised to allow a better view for cabin crew of the outside area and external aircraft parts, such as engines, wings, etc.
See also this related question: Why open up the window shades before takeoff and landing?

You better start believing in the explanation of power saving.

I couldn't find the reference, but there was an accident over 5 years ago in which a plane was taking off with many non-essential loads at or near maximum: air conditioning, galleys heating food, cabin lights.

One generator failed, and the system supposed to shed non-essential loads also failed. The remaining generator wasn't designed to stand so much load, so it failed too. Loss of power to essential loads.

Since then, airliners take off almost simulating an electrical emergency. Reading lamps are a reasonable compromise because very few people actualy use them.


What is a good plane for aerial photography? I'm a bit of a photographer and I keep thinking it would be fun to try and do some shots aloft.  Only trick is, I'm not sure what kind of plane I would want to use to get those pictures done.  I'd have to rent the plane and the pilot and I'd like to keep the price down as best as possible...  So a purpose built plane isn't such a big deal.

Other considerations

Good view of the ground, though it doesn't have to be straight down (I'm not doing surveying
Stable while banking so I can more easily track shots when the plane is at an angle.
Ability to be held stably at a bank without actually turning the craft, again to help me track my shots.
Low vibration, for the same reason as stated over the last two.
Big windows
Can fly low and slow for if I want to get close to things (within reason.)

Also, a high wing is probably preferred.  Though, if it's exceptionally good at holding a bank, it may not matter.

If you think of anything else that I should consider to keep my camera from being jangled about, and to allow me to have a good view so I can get some shots...  Please feel free to leave them in the comments.

So, what plane would work best for this mission?

I used to work at a sport parachuting center - we occasionally had photographers rent one of our Cessna 182 airplanes for the same purpose. An advantage of jump planes is the pilots are quite used to odd attitudes (and even odder requests) so a 60 degree bank angle with the door open and you leaning out of it will get a reply of "no problem".

Our conditions were the photographer wears a parachute, a seatbelt, and if the camera goes for a jump that's just too bad for your wallet. 30 minute lecture on what to do if you fall out. Short form: drop camera, grab this handle, pull. And the trip's over if you do anything silly.

You would sit on the floor where the co-pilot's seat would normally be, the pilot will open the door as needed, and you have a clear view out the right rear quarter of the plane. Obstacles are the wheel (front half of the door looking down) and wing strut (forward) - the tail is well out of the way. It's very noisy, but unless your camera is actually outside the fuselage the wind blast is not an issue. Don't change lenses though, and your clip-on lens hood will probably disappear rather quickly.

You can sit on the door ledge with your feet outside and have an excellent, stable field of view with both hands free to operate your camera. I've sat there hundreds of times without a seatbelt, it's no problem even in steep turns. Just a bit odd seeing the ground above the wingtip. Difference is, I don't care if I fall out.

How about the AirCam?  It was pretty much designed for the type of aerial photography you describe - low and slow with great visibility.


Why are the modulation depths of the localiser and glideslope different? Why do we use a modulation depth of 20% (for 90Hz and 150Hz each) in the case of the localiser and 40% (for 90Hz and 150Hz each) in the case of the glideslope? Why not use 20% for both?

From the book "Principles of Avionics" By Albert Helfrick:

  The amount of modulation is twice that found in the localizer. Because the glide slope does not have ident or speech audio, the percentage modulation for 90 and 150 Hz tones is increased.

Appendix B of this document  https://www.faa.gov/documentlibrary/media/order/6750.24e.pdf
appears to refer to ICAO Annex 10,  http://cockpitdata.com/Software/ICAO%20Annex%2010%20Volume%201  .
See 3.1.3.5.3.3 and 3.1.5.3.3.4 for the Localizer, and 3.1.5.5.3 for the Glideslope.  That's why they use what is used currently; the International Standard says to.

As to the why of the particular modulations, I don't have the history of how the particulars were developed over time.  A google search of "ils approach history" yields quite a few hits tho.
This one seems quite detailed.
http://instrument.landingsystem.com/


What are the V-Speeds used during a normal takeoff in a multi-engine airplane? This is what I know:

$V_1$ is the takeoff airspeed after which the aircraft must take off, no matter what happens after $V_1$ has been reached. That's the easy part (I think).
$V_R$ is the rotation airspeed

Are there any other $V$-speeds?

What I'm specifically curious about:

Is $V_1$ related to runway length?
Is there an absolute maximum $V_1$ for each aircraft type? If so, can it vary based on conditions (takeoff weight, density altitude, etc.)
Are there circumstances where $V_1$ is higher than $V_R$? If so, does that mean that $V_1$ is never called on a normal takeoff? (this is the case for most light aircraft, but I guess the whole concept is not applicable in that case)
What exactly is $V_2$?
Is there a $V_3$? (and so on)

Anything else worth knowing about $V$-speeds?

$V_1$ is takeoff decision speed.  It is based upon:

Runway length
Temperature
Reduced thrust takeoff
Takeoff weight
Takeoff flap setting

If $V_1$ is higher than $V_R$, then (as far as I am aware), $V_1$ will be adjusted to be the same as $V_R$.  You have to make the decision to takeoff by the time you rotate, so it does not make much sense to have $V_1$ higher than $V_R$.

$V_2$ is takeoff safety speed.  During a one engine inop takeoff we would accelerate to and climb at this airspeed to our acceleration height (a height we could level off at and be safe from obstacles while we further accelerate).  We also referenced certain flap transitions on takeoff to $V_2$ (e.g. $V_2+15$ - flaps 0)

To address the rest of the question, $V_1$ and $V_2$ are primarily used in large aircraft.  In light twins you also need to be aware of $V_{MC}$.  $V_{MC}$ is the minimum controllable airspeed with an engine inop.  In particular you do not want to be slower than this airspeed during climbout in case of engine failure.

VMO and VMC are both important

VMO = Maximum Operating Speed, a structurally safe maximum speed which varies with altitude. For example with an emergency descent in a B777 the VMO is 310kt IAS, but in level flight it is 330 KIAS. As you climb the air thins so the true airspeed increases.

VMC = Minimum Controllable Speed with one engine inoperative, gear retracted with CG at most rearward limit, bad engine at idle but not feathered (if propellor)


Why does the angle of descent increase in a constant headwind while decreases in a sudden encounter with a headwind, in a descend? I'm currently studying aerodynamics.
I have realized that a sudden encounter with a headwind during descent
will result in the aircraft generating more lift, thus angle of descent decreases.
I haven't studied the descent in a constant headwind, but through research I've come across that a constant headwind during descent will increase the angle of descent.
This does not make sense. Shouldn't the angle of descent decrease in both situations? Will appreciate it if someone could explain this.

Consider descending in zero wind, trimmed to an airspeed of 80m/s (288km/h) and a sink rate of 2m/s. You won't touch stick, trim tabs or throttles during the descent, but you will encounter a headwind at a later time. For now, ground speed is equal to airspeed and the angle of descent is 1:40.

You suddenly encounter a headwind of 20m/s. Ground speed remains at 80m/s due to inertia; Airspeed rises to 100m/s. The rise in airspeed increases lift and reduces sink rate to 1m/s. The angle of descent is now much shallower, at 1:80.

After a couple of seconds, airspeed bleeds off and the aircraft resumes its trimmed state at an airspeed of 80m/s and a sink rate of 2m/s. This time, the ground speed is only 60m/s due to the headwind and the angle of descent is now 1:30.

Apart from transient effects, that are short-lived as such, for example in that 'sudden encounter' that you mention, the angle of descent of a gliding aircraft is not affected by the wind...


What is an accurate expression to calculate IAS as a function of TAS? Does anyone know a good source for an expression of IAS as a funtion of TAS? I was hoping to find an accurate IAS equation that is only dependent upon TAS, static pressure and static temperature.

You might look at Ed William's aviation formulary.

http://www.edwilliams.org/avform.htm#Mach

From there:

> The airspeed indicator measures the differential pressure, DP, between
> the pitot tube and the static port, the resulting indicated airspeed
> (IAS), when corrected for calibration and installation error is called
> "calibrated airspeed" (CAS).
>
> For low-speed (M<0.3) airplanes the true airspeed can be obtained from
> CAS and the density altitude, DA.
>
>   TAS = CAS*(rho_0/rho)^0.5=CAS/(1-6.8755856*10^-6 * DA)^2.127940
> (DA<36,089.24ft)  Roughly, TAS increases by 1.5% per 1000ft.

Note that you can go from TAS to CAS, but you will need help getting to IAS, specifically the instrument error for that AS indicator in that aircraft.

TAS : True Air Speeda

IAS : Indicated Air Speed

CAS:  Calibrated Air Speed (reference airspeed based on  an idealized Pitot tube)

IAS = CAS + Ki, where Ki is an error component specific of your instrument

The conversion between TAS and CAS (and IAS) needs also to take into account the variation of air density (i.e. altitude).
So the conversion requires a bit more parameters.

A good answer is provided here:
How do you convert true airspeed to indicated airspeed?


Why does An-225 (Mriya) perform a low-pass on its landings? Today was a big event for aviation fans where I live (Warsaw, Poland, EPWA). We have had a visit of Antonov 225 (Mriya).

Today, but also as I saw in other videos, it often (always?) performs a low-pass first and only then lands. Why is that? I bet this is about safety, but...

is it mandated by some official rules?
or by some internal rules of the operating airline?

What kind of information does the pilot need which they wouldn't get by reading the maps, diagrams or by talking to ATC?

As of the time of writing this answer, this only appears to have happened in one out of the last 6 flights of the AN-225 (the same flight into Warsaw you mentioned, https://www.flightradar24.com/data/aircraft/ur-82060#245b19c0) so I can't say that this is an official "rule", a standard of any kind or any procedure regarding the AN-225.

There are 2 other videos of that particular landing on YouTube:

It is clear in both videos that the first approach is done with the landing gears up, most likely on purpose "for the show", of course with coordination with ATC.

If someone is fluent in Ukrainian they can confirm it quite easily since the communication between the pilots can be clearly heard in the video you provided.

There are many possibilities. It might have been a landing gear check, or maybe the crew noticed something wrong last minute and performed a go-around at last second. There aren't much regulations on low-passes, but usually pilots do low passes because they either have not been in that airport and are not experienced, or they are flying an uneasy plane, for example, the AN-225. They do this because they want to get a feel for the approach, that way, it's harder to make a mistake, and you'll feel more comfortable on landing.


Is there a minimum distance between a runway and a public road? Does the FAA require a minimum distance the between the TDZ of a runway and a public road?

The reason I ask is because an aircraft landing at a small GA airport (Garnett Municipal, K68) came across the roadway I was driving on low enough that if I'd been 200 yards up the road he'd have hit my truck. Or at least he'd have had to go around.

From the satellite pic you can see that the end of the runway is about 30 feet from the road. The TDZ is about 150 feet. A 3° approach would put you just short of 8' AGL at the road, which is just about exactly how high he was. My truck has a clearance of 10', so it's quite possible to strike vehicles on the road if one is too focused on the runway.

Although it's not a highway (that's about 1000' from the runway), it's the only paved road going east/west for several miles so it gets a bit of traffic

Is it common to put a runway so close to a road?

Yes, there is a minimum area that must be free of obstructions and closed to vehicles, but only for airports that have air carrier operations (see 14 CFR 139.309) or that receive FAA grants. AC 150/5300-13A - Airport Design has all the technical details; the actual distances are calculated from formulas, so there's no single answer. If you're really curious, you can read all the gory details in Chapter 3 and this FAA FAQ has a (very) simplified explanation:

  What is the size of the RSA [Runway Safety Area]?

  The RSA is a rectangular box surrounding
  the runway and is based on the runway design code. The dimensions
  range from 120 feet to 500 feet in width and 240 feet to 1000 feet in
  length beyond the departure end of the runway. (see FAA Advisory
  Circular 150/5300-13, Airport Design) Generally, on airports that
  serve air carrier aircraft, the RSA extends 250 feet either side of
  the runway centerline and 1000 feet beyond each end of the runway.

You didn't mention which airport you're asking about, but presumably it's either privately owned and/or doesn't receive FAA grant money.

The FAA regulates aviation and aircraft, not road layout or runway locations.

The standard glideslope is three degrees, pretty shallow, so aircraft often travel long distances low above the ground prior to landing. Trees are a big issue. On the island of St. Maarten 747's fly as low as 10-15 feet right over a heavily populated resort beach and pathway.

Credit: Blick, William E. Princess Juliana International Airport

Often there are signs warning of low-flying aircraft so that motorists are not startled.

Don't worry about it too much, planes are way more flimsy than a truck, so as long as the 50 gallons of aviation fuel does not catch on fire or explode, your vehicle will come off much better in the rare event of a collision.


How bad is the efficiency of jet engines under low loads? VTOL operations need 4-5 times more thrust than a conventional take-off of an aircraft.

If you don't want to install additional lift-engines into a hypothetical aircraft and use thrust vectoring to turn the thrust towards the ground, you naturally end up with largely oversized engines for the cruise flight.

But how bad does the fuel efficiency (thrust per amount of burned fuel) get, when the engines run at their minimal self-sustaining throttle setting during cruise?

Current jet engines are actually not built for efficiency rather than performance.

If you consider efficiency, you don't build a VTOL aircraft. This is why the F35 has multiple versions with and without VTOL capabilities.

Also, jet engines even during flight have to be able to sustain fast speed change, fast altitude increase and high load factors, all combined with lightweight designs. Therefore, I wouldn't consider takeoff as the most demanding phase of flight for such engines, but I may be mistaken on that point.

All these conditions make it difficult to reach the efficiency of say turbofan or turboprop engines.

https://en.wikipedia.org/wiki/Harrier_Jump_Jet

https://en.wikipedia.org/wiki/McDonnell_Douglas_F-15_Eagle

Both are twin engine fighters and have similar thrust - one appears to be a litte more aerodynamic than the other.  So I would think that fuel efficiency when
minimal self-sustaining throttle setting during cruise is used could be similar too.