Straight Wings VS Delta Wings, Variable wing with Forward swept capability What are the Pros and Cons (Advantages and Disadvantages) of a Delta wing and a Straight wing against each other, and if a Variable wing with a capability to become a Forward Swept wing is even possible to create.

At low speed, the key to reducing "induced drag" is to have a high aspect ratio, that is, you want wings that are long and skinny. Think gliders. Now of course, these are not easy to build, and for entirely practical reasons you might want something that's more square-ish than a glider. That's one of the many engineering trade-offs every aircraft design requires. Check out the svelt wings on this Q400:

Things become more interesting as speed increases.

First, as you enter the transonic area above around 450 mph, a new form of drag begins to form, the so-called "wave drag". The way to reduce this is to make the wing as thin as possible, or to be more specific, have as little curvature on the top and bottom edge. Ultimately you want an almost flat plate.

Now of course, lift is generated by that curvature, so that's a problem. And when you try to reduce that curvature to lower wave drag but still want the same lift, well then you have to make the wing larger front-to-back (think about it) and now your induced drag goes up, and skin friction too in most cases.

So then there's a trick. If you sweep the wing to the rear then the air flowing over it travels across a longer distance. So it thinks the wing is longer front-to-back and has less curvature, and that lowers wave drag. Yet at low speeds, the air smoothly flows over the curves and sees the original wing profile. So you get a thick wing that looks thin. Check out this F-86, notice that the wings are actually pretty thick:

Now as you go supersonic, things change yet again. In this case the drag is minimized by having the least width you can get away with. So for these sorts of designs you want short stubby wings with lots of chord (front-back) and you end up with the F-104.:

Now you have a wing that is absolutely terrible at low speeds, and for that reason, lots of F-104s crashed while the pilots tried to keep up with the plane while landing at redonkulous speeds needed to keep the thing in the air.

Deltas are mostly just swept wings with the inside filled in. If you want to see an example that really illustrates this, look at the English Electric Lightning:

If they filled in that little part, it would be a delta. But there is one trick that you get in a delta you don't get in a swept wing...

At very high angles of attack, with the nose high, the air along the leading edge of the wing can generate a vortex right along the fuselage. If there is a wing under it, this generates lift. Poorly, with lots of drag, but lift. So then you get this little one-trick-pony effect; this will works really well at high speed, but also works OK at really low speeds too. But it only works if the vortex is above actual wing, so the Lightning didn't get all the advantage here.

The problem with deltas are that they are big and heavy, but they also get more room inside for fuel. More trade offs. But then someone came up with a new idea: make a normal swept wing and then add a little bit of delta:

You can even see the vortexes in this image. In this case the little-bit-of-delta is called a "leading edge extension".

Variable wings are simply an attempt to put all of these on a single aircraft. Rotate them forward and you have a nice long skinny wing like the Q400. Rotate them back and you have a really swept wing or even a delta, and at the same time the width is being reduced. So now you can go fast or slow. Just weighs a lot.

Swept forward is basically identical to swept back. This isn't about lift in this case but an attempt to control something called spanwise flow. Check out this MiG-17's wing:

Do you see those metal plates? What happens on a swept wing is that the shape causes some of the air to move sideways. This is a Bad Thing. So these plates grab sideways moving air and redirect it over the wing again. The same thing happens on deltas, check out the notch on the CF-105, same idea:

Now the idea here is that the wind is following the wing's leading edge. So what happens if you sweep it the other way? Well then it follows the wing into the fuselage, and stops. Presto, problem solved and no plates or notches! The problem is that it's really hard to actually make one that doesn't snap apart, which is why it's not common.


How to match ATC requirements to work in EU? My Brazilian boyfriend is finally planning to move into the EU zone (he actually got an Italian passport). He would be glad to keep his work as an Air Traffic Controller but despite his 10 years working experience he told me he should start the training all over again.

Can someone point us out the shortest way to match the requirements for EU Standards and/or suggest us where to find this kind of information?

I would suggest to contact the IT ANSP and ask if they accept applications for ready entry ATCOS: https://www.enav.it/sites/public/en/LavoraConNoi/Traduzione-di-Contatti-n.html

In Germany we have plenty of so called „ready entries“ who applied for a job as ATC in Germany while holding a valid non-EU ATCO license.

After an assesment by our company and - hopefully - signing the contract they participate in some weeks of sim training to learn the procedures of the new sectors. After succesfully completing the sim phase the OJT (on the job training) begins. During something between 6 and 12 months they will train working in real world with a coach and finally take one examination per working position.
That‘s it!


Is there a way to find what types of aircraft have landed at an airport? When I was a child, I recall an aircraft landing at my local airport, CSG, I would like to know if airports keep records of what aircraft land there? If so how long do they keep these records, and are the available to the public?

Speaking for the US, airports only report total movements (landings/takeoffs) and this information is available to the public via the FAA. This information is in aggregate and does not contain the type of aircraft.

Flightaware tracks only the type of aircrafts that land and takeoff at an airport; it also tracks the identifier used. It has very good coverage globally, although some areas have better (more accurate) information than others.

For most GA flights, the identifier is sometimes also the tail number, which can then be used to narrow down on a specific airframe.

Just add the ICAO identifier for your aerodome at the end of this URL: http://flightaware.com/live/airport/ to see stats of a particular aiport; for your airport its http://flightaware.com/live/airport/KCSG


Has this Google Maps imagery of 4 planes on a runway been tampered with? The image below is of Google Maps (30 May 2018) of Amsterdam Schiphol's Aalsmeerbaan (36R).

It shows 4 planes on the runway and a fifth that's about to land. When you zoom in, all planes seem identical.

Has this image been tampered with or could there be an explanation for this?

Google Maps and Google Earth are made by stitching together many different images to create the illusion of a single massive picture of the globe.

The image you are seeing was almost certainly made by an aerial photography plane passing overhead of another plane landing.  In multiple snapshots, it captured the same plane on final, touching down, rolling out and stopping.

The images were assembled together to line up the ground and all static elements.  But items that are moving appear multiple times in different images.


What was the inflight entertainment in the early seventies? In her 1970 song "This Flight Tonight", Joni Mitchell sings

  I'm drinking sweet champagne
  Got the headphones up high
  Can't numb you out
  Can't drum you out of my mind
  They're playing Goodbye baby, Baby Goodbye
  Ooh ooh love is blind

The Sony Walkman first came out near the end of that decade. So what was Joni listening to on that fateful flight?

I will award a 100 point bonus to anyone who can identify the plane she was on in the song based on the lyrics.

During that time, the in-flight entertainment mostly available on flights was radio1 and/or TVs. Although it was not on all flights. Oops, that is true even today.

The radios may or may not have channels. If they had, there was a knob on the armrest, next to headset jacks, to switch channels. The headsets were pneumatic units like this:

The in-flight movies were shown using one or more common CRT TVs mounted on ceilings or walls and audio could be heard using the headsets. The first time a movie was shown on an international flight was in 1962 by PIA. It was more like the picture below but instead of LCD monitors, there were CRTs.

In mid-seventies, Braniff Airways was the first airline to offer video games in-flight.

By 1979, electronic headsets replaced their pneumatic counterparts, which improved audio quality.

Wikipedia has a detailed article about the history of in-flight entertainment:

  In 1971, TRANSCOM developed the 8mm film cassette. Flight attendants
  could now change movies in-flight and add short subject programming.

  In the late 1970s and early 1980s, CRT-based projectors began to
  appear on newer widebody aircraft, such as the Boeing 767.

This website has nice slideshow about the history.

1: Not actually a radio, but recorded audio


Do helicopter rotor blades speed up and down during the rotation? Does the inertia force change the angular velocity due to increase-decrease in the radius when the blade travels up? Does this cause an excessive bending moment?

A helicopter rotor usually has flapping hinges, which lifts the blade up when travelling forward and down when travelling backwards. The blade being at an angle indeed causes a change in effective moment of inertia: it would want to speed up when at an incline, and this would indeed cause a bending or warping moment were it not for..

..the Drag Hinge or lead/lag hinge. The image is from this site which contains an explanation on other rotor heads as well.


What causes aircraft to swerve during takeoff? I notice on some commercial flights that the aircraft can begin to swerve left-to-right during takeoff before we leave the ground. Sometimes this can become very exaggerated, very hard left-to-right swerving. This is typically from around mid-way through the takeoff run, becoming most severe immediately before takeoff.

My first thought was perhaps it is an inconsistency in the runway from the airport I frequent but have noticed it once or twice at other airports as well, and across different carriers. However, it feels more like when driving a car and you swerve, then overcompensate the other direction and it becomes a vicious cycle.

Other factors may include wind - but I've been in high-wind takeoffs before and it didn't have the same jerking motion.

Any explanation to this, or am I just paranoid?

*Apologies for lack of knowledge re: terminology

I know you said that you don't think it's a crosswind, but honestly it most likely is.  As the plane speeds up and the wings start to generate more and more lift the plane is more easily affected by cross wind.  So, as you speed up, it gets harder and harder to keep the plane straight.  Throw in some gusts, and you're going to get some jerking motions as well.  Especially if that gust decreases the lift of the aircraft, the wheels suddenly catch the ground more and the craft is suddenly tugged harder than the pilot anticipated...

Here's a video of a Boeing 777 taking off in a heavy crosswind that should illustrate the point more.


Could a civilian aircraft in distress land in Area 51? Just curiosity, but in case of a real life-threatening emergency (where you can't fly to closest airport or strip), would they (Air Force, military or whoever) allow the plane to land on the Area 51 airstrip? Have there been any occurrences that we know of?

R-4808, the restricted area around Groom Lake, NV, is restricted at all altitudes.  It is also surrounded on multiple sides by other restricted spaces and MOAs.

No routes, low-altitude or high-altitude, go through the area.  No one has any business being near there to begin with, so no one will have any emergencies in the area.


How far away from the airport is the descent for approach and landing initiated? I am wondering if there is a rule-of-thumb formula for the speed, altitude and the distance from the airport that the descent for approach to land is initiated? I see airlines do it about 25 to 30 minutes before landing. When, say a King Air, TBM, etc.,...doing 275 Kts at 28,000 feet will start the decent for landing at a sea-level airport, barring unusual weather or traffic conditions?

As J. Hougaard said, 3 nautical miles per 1000 feet is the general rule. However, large aircraft that can vary greatly in weight may vary that figure. Also, best to factor in whether tailwinds or headwinds in the descent.

In 747-100/200 freighters in the 1990s, we used the 3 nautical miles per 1000 feet most of the time. However, if we were heavy, i.e. we would be landing right up against the max landing weight, we would use 3.5, and especially if we would be descending in a tailwind. If we were light, in other words no cargo, 2.5 was a good figure to use. And, of course, you didn't have to use exactly 3.5, 3.0 or 2.5. What I often did was figure the 3.0 distance and then just add or subtract 10 miles or so.

In one memorable instance, I used 2.0 and it worked, but just barely. I had heard that if you had an empty aircraft and used a maximum drag procedure it could be done. I only had a chance to try it once going into Hong Kong's old Kai Tak airport on a clear day with no traffic, straight in to rwy 31.


How should I read these abbreviations on the Airbus 320 MCDU? Often I have seen some abbreviations on the Airbus MCDU such as CI, CF, etc. They are explained in this question: What do the different types of approach abbreviations used on the A320 MCDU exactly mean?
How will I call them when forming my approach briefing? Is there any manual that trains pilots on these abbreviations? I need a quick guide to understand how to interpret these?

These are RNAV procedures as defined in ARINC 424 used for database coding. They define paths which an aircraft must follow during RNAV departures and approaches. Every standard departure and approach can be divided into distinct sections. Each possible path starts at a point and ends at a termination point. The file format is standardized so that each and every FMS system can read the same file format. You can get an overview at this link.
This document requires pilots to be trained in and familiar with the paths and terminators used in RNAV departure and arrival procedures.

Understanding this terminology gives the pilot a vocabulary and a framework to better understand how an RNAV computer navigates.

RNAV departure and arrival procedures are constructed using legs or segments defined by a path and a terminator.

The path is how you get the, i.e. heading or course
The terminator is the event that causes the start of the next leg, or the end of the procedure.

There are 23 path terminators combinations defined in ARINC 424

13 are used for RNV departure and approach procedures
Each procedure has a two-letter code.

Example:
RNAV procedures start at an Initial Fix (IF) which can be a fly-by or fly-over waypoint, followed by:
Track to a Fix (TF)

The primary straight route segment for RNAV
The segment starts at either an Initial Fix (IF), or the termination of a previous segment.

Direct to a Fix (DF)

Defines a route segment from an unspecified aircraft present position to a specified fix/waypoint.

Course to an Altitude (CA)

Defines an outbound route segment that terminates at an altitude, not at a specific location.

Heading to an Altitude (VA)

Defines an outbound route segment that terminates at an altitude, not at a specific location
Similar to Course to Altitude (CA), but fly an uncorrected heading without regard to wind or ground track.

Course to  a Fix (CF)

Defines a wind-corrected course to a specific fix
Frequently used as the final segment of an approach

Course from a Fix to an Altitude (FA)

Segment begins at a defined fix/waypoint
Requires a wind-corrected heading to maintain course
Terminates when the aircraft reaches the assigned altitude, not a specific location
Common in missed approach procedures.

Others:

Course from a Fix to a Manual Termination (FM)
Heading to a Manual Termination (VM)
Heading to an Intercept (VI)
Constant Radius arc to a Fix (RF)

Every RNAV departure and approach is made up of a combination of the these paths and terminators.
King Schools has an online course for P-RNAV.


Has the financial situation of an airline ever negatively impacted safety? Has a bad financial situation, or simply being greedy, impacted negatively the safety of an airline or even caused lethal accidents?

Notice that this is not necessarily a question about low-budget airlines like  Ryanair and EasyJet, JetBlue, or Spirit. Low ticket price does not imply the company is in a tight financial situation. No frills does not imply cutting costs at the wrong end.

Although regulations are the same for all, there are certain scenarios where this seems to matter. No airline will be allowed to skimp on safety issues, but wouldn't having less resources imply:

Hiring cheaper pilots, which fulfill minimal requirements, and not much else.
Flying routes that are open, but less safe, like Ukraine until recently.
Putting more pressure on pilots to fly against their judgment.

Pan American World Airways declared bankruptcy in January 1991. In the year previously they were doing everything they could to to avoid that. To help their cash flow, Pan Am sold five of their 747s for cash to Evergreen International Airlines. The deal was that EIA would immediately lease the five back to Pan Am, which they did. Unfortunately, Pan Am soon defaulted on the lease payments and EIA began repossessing the aircraft.

EIA gave Pan Am fair warning on the repossession of the first aircraft, at which time Pan Am swapped out good components for crap components before surrendering the aircraft. Not to be taken again, when EIA repossessed the second aircraft, they did so without warning at the gate when the aircraft arrived in JFK from Europe.

I was the f.o. on the crew that was sent to get the aircraft. We were in the cockpit setting up when one of our maintenance guys came in and said that they had just received orders to boroscope the engines, which they did while we waited in the cockpit.

After an hour or so, one of our JFK managers came into the cockpit and told us that we wouldn't be going anywhere, that the airplane was not flyable as three of the four engines were significantly below required tolerances.

So, if flying a plane load of passengers across the North Atlantic with three out of four engines below required minimum maintenance standards constitutes a negative impact on safety, then, yes, a bad financial situation did indeed, at least once, cause such.


Which aircraft feature stock exterior cameras? Watching a video on YouTube of an A340-600 takeoff, I noticed that it has at least two exterior cameras — one for lining up the nosewheel, and the other on the tailfin:

After the NTSB recommended the use of exterior cameras in 2012, I'm wondering how widespread these are? Which models of Airbus aircraft have them? Do any Boeings?

Do these record or are they realtime-only?

I fly the A320 and 321 which, at our company, had been equipped with nose cameras. The pictures, though, where just used for passenger entertainment during takeoff and landing and keep being disconnected by maintenance when failed due to high spare parts costs.


What is the three-light indicator on carrier-borne airplanes? (YouTube)

The above three-light forward facing indicator can be seen on most (all?) nose landing gears of carrier-borne aircraft.

What is it called? I suspect it relays the angle-of-attack / E-bracket position to the landing safety officers (LSOs).

If that's true, I still don't understand why since the planes are already tracked by radar (e.g., the SPN-42/46 radar) and deck cameras pointing down the glide slope. And the same information is shown to the pilots, which they already use to fly the correct AoA.

Do the LSOs keep it insight using their binoculars? Or does the same deck camera system image-process the lights?

Those are angle of attack indicator lights. The landing signal officer on the carrier can judge whether a pilot making an approach of the boat is on angle of attack using those. The center light will be amber and will indicate that the airplane is on angle of attack for the approach. The upper light is green and will indicate to the pilot is it too high of an angle of attack, that is going to slow. The lower light will be red and indicates that the pilot is it too low of an angle of attack i.e. is too shallow in approach angle and going to fast.  The lights correspond with those on the angle of attack indicator which is located to the left of the head up display in the cockpit.

Flying the proper approach speed is a key ingredient of any approach be it carrier or terrestrial.  Again due to the inherent tighter tolerances of a carrier landing, the AoA data is useful for the LSOs to spot deviations in the approach.  Second, since Vref varies for all aircraft approaching the ship based on type, gross weight, etc. a radar tack of the aircraft would require the LSOs compute the required Vref ahead of hand for every pass at the boat.  It’s much easier just to observe a simple light indicator on the jet from the LSO platform to gauge this by.

Regardless LSOs do also have access to the raw AoA information from an aircraft making a pass and it is displayed on the PLAT camera at the LSO’s platform.  Whether that data is based on a direct telemetry from the jet on approach or some other source is unknown.  One possible reason for retaining the lights is for Emission Control (EMCON). Radio signals known to be used for recovery procedures would be valuable to an enemy since a carrier is most vulnerable to attack during startup and recovery operations and a simple set of lights visible only in the immediate vicinity of the ship would be advantageous here.


How could MH370 fly west when satellite pings went east? I have a question perhaps best demonstrated with this image:

Malaysia published two maps with the preliminary accident report which allege MH370 flew west from Penang to MEKAR (above Aceh Province) and then between 18:25 UTC and 19:41 UTC flew west into the Indian Ocean.

The problem is the Burst Offset Frequency chart published 24 March shows a frequency drop after 18:25 UTC signifying flight away from the satellite.

After MH370 allegedly emerged from the Straits and turned south the track which Malaysia's Preliminary Accident Report claims MH370 flew (based on their analysis of the BOF chart data) the track makes even less sense because the distances away from the satellite continue to increase.

And this image shows the distance relationship with the satellite:

There are also other (non satellite) reasons to question the validity of the alleged track through the Straits of Malacca. First is the claim MH370 was seen flying west by radar at Surat Thani in Thailand. That radar has a published maximum range of 200nm. Kota Bharu is 240nm away from Surat Thani.

This is not the only reason to doubt the alleged MH370 flight though the Straits. Malaysia presented this image to Chinese relatives at the Lido hotel in Beijing on 21 March and told them it was a military radar image from Butterworth of MH370 in the Straits of Malacca. They said it crossed the island of Pelau Perak at 18:02 UTC and disappeared at 18:22 UTC.

The image however omits other aircraft known to be present at the same time:

Worst inconsistency of all however is this, the radar image does not even come from the Butterworth radar. The real military radar used by Butterworth is a Thales Raytheon GM400 which has a screen display like this:

I don't understand how so many supposedly intelligent "experts" and journalists have managed to be deceived for so long except to say people believe only what they want to believe and shut their eyes to the truth.

Australian, Malaysian, Japanese, New Zealand and Chinese taxpayers collectively forked out $90m wasted taxpayer dollars for a search at the end of this projected BOF track in April which turned up no result.

My question is how does this mutually incompatible information prove MH370 flew west through the Straits at all?

You have an error in one of your major premises.

You say "satellite pings went east".

That can't be derived from the data you have shown. The chart is showing Doppler shift. A westbound aircraft that is decelerating, or simply decreasing its component of velocity toward the satellite (by, for example, turning slightly southbound) will result in a change in the Doppler shift.

Deviations up and down on that chart don't correspond to the velocity being east or westbound, but accelerations towards or away from the satellite.


Do all aircraft need to have horizontal and vertical stabilizers? Are (or were) there any operational aircraft that don't have horizontal and vertical stabilizers or canards? If so, what's the effect on how they fly?

Depending on how you classify the control surfaces, the B-2 Spirit does not have a horizontal stab, since it is a "flying wing" design.  As you have changed the question, the other part of the answer is that the flying wings have been able to get by without vertical stabilizers as well, at least in the case of the B-2. It uses both spoilers ("split brake rudders") and thrust differential to accommodate the lack of a vertical stabilizer.

  Northrop had investigated several means of applying directional
  control that would least infringe on the aircraft's radar profile,
  eventually settling on a combination of split brake-rudders and
  differential thrust ~  Sweetman, Bill. "Lockheed Stealth" (2005) ISBN 0-7603-1940-5., p. 73

(And as with flight controls in general on the on B-2, that's helped a lot by its fly by wire flight control system).

As the Germans discovered in their flying wing aircraft (Ho229), and the USAF in the YB-35 and YB-49 programs, flying wings have inherent instability, even though some early biplane "flying wing designs" were stable enough to fly. (Dunne).

The B-2 has a fly by wire system to retain stability and handling qualities so that it does not have to make tradeoffs (loss) in performance that earlier flying wing designs did in order to make the design "stable enough."

What the elevator/horizontal stab do for conventional aircraft is allow for longitudinal control (pitch control).  If you don't choose to use that conventional method, the "effect" is that your design must find another way to establish longitudinal control and stability or the aircraft risks being unstable in that axis.

Likewise with vertical stabilizers, your design has to address stability in the yaw axis if you want to make it without a control surface acting in that axis.


Can having too small of a roll or yaw stiffness destabilize the dutch roll mode? For a dutch roll mode, can having too small of a roll or yaw stiffness destabilize it?

I would think not because you want a lower value to maintain it?

To estimate whether the dutch-roll mode goes unstable, we can assess the real-part of the dutch-roll eigenvalue: negative is stable and positive is unstable. From Etkins, Dynamics of Flight, one illustrative estimate (although not necessarily numerically accurate) is as follows:

$$n_{DR}\approx\frac{1}{2} \left[ \frac{Y_v}{m} + \frac{N_r}{I'_z} + \frac{I'_zL_v}{I'_xN_v}\left(\frac{N_p}{I'_z} - \frac{g}{u_0} \right) \right] $$

where $n_{DR}$ is the real-part of the eigenvalue, $Y_v$ is the dimensional side force sideslip derivative, $N_r$ is the dimensional yaw moment damping, $L_v$ is the dimensional negative roll stiffness (dimensionless form: $C_{l_{\beta}}$), $N_v$ is the dimensional yaw stiffness (dimensionless form: $C_{n_{\beta}}$), $N_p$ is the yaw-roll cross-coupling moment, $u_0$ is the trim airspeed, $g$ is gravitational acceleration, $m$ is aircraft mass, all the $I'$ are inertia terms about the respective axes. Note that all the inertia terms are about the principle axes for simplicity.

The first term ($Y_v$) is always negative, and so is the second term ($N_r$). Ignoring $N_p$ for now, positive roll stiffness requires $L_v$ to be negative, and positive yaw stiffness requires $Y_v$ to be positive; this means that the third term is net positive. Therefore, we can draw the following conclusions:

Dutch-roll damping worsens at lower airspeed
Roll stiffness worsens the dutch-roll damping
Yaw stiffness improves the dutch-roll damping

To answer your question: yes, it's entirely possible for dutch-roll to be unstable due to sufficiently low yaw stiffness.


"What's our vector, Victor?": What does this mean? In Airplane there is a famous sequence:

Roger Murdock: Flight 2-0-9'er, you are cleared for take-off.
Captain Oveur: Roger!
Roger Murdock: Huh?
Tower voice: L.A. departure frequency, 123 point 9'er.
Captain Oveur: Roger!
Roger Murdock: Huh?
Victor Basta: Request vector, over.
Captain Oveur: What?
Tower voice: Flight 2-0-9'er cleared for vector 324.
Roger Murdock: We have clearance, Clarence.
Captain Oveur: Roger, Roger. What's our vector, Victor?
Tower voice: Tower's radio clearance, over!
Captain Oveur: That's Clarence Oveur. Over.

Regardless of the silly dialogue, when the captain asks "What's our vector, Victor?" what is he referring to? Does the scene refer to actual issues that one might discuss with air traffic control?

A vector is defined by a direction and magnitude.  In aviation these represent your heading (the direction) and your speed (the magnitude).  However, in normal aviation usage "vector" only refers to the heading and other nomenclature is used to assign/report speeds.

Example:

"Jetlink 1234, Cleveland Center, turn left heading 250 for traffic"

In which case the vector assigned by ATC is 250 degrees, or 20 degrees south of magnetic west.

To answer the question "What is our vector, Victor?", Victor should state the heading they have been assigned to fly from ATC.

An alternative question would be "What is your heading?" and then you would answer with the direction you are currently flying.


Are student pilots required to have spin entry and recovery training? Do trainee pilots learn to enter into spins and recover from them in any basic trainer aircraft? Does any regulation mandate this?

US used to, I recall doing spin & recovery 3 times in a Cessna 150 Aerobat (in 1994), and feeling queasy for quite a while after that. I think now those maneuvers just need to be demonstrated. See AC 61-67C, excerpt follows

  CHAPTER 3. FLIGHT TRAINING: SPINS
  300. SPIN TRAINING. Spin training is required for flight instructor-airplane and flight instructor-glider applicants only. Upon completion of the training, the applicant’s logbook or training record should be endorsed by the flight instructor who provided the training. A sample endorsement of spin training for flight instructor applicants is available in the current edition of
  AC 61-65, Certification: Pilots and Flight and Ground Instructors.

  a. Spin training must be accomplished in an aircraft that is approved for spins. Before practicing intentional spins, the AFM or POH should be consulted for the proper entry and recovery techniques.

  b. The training should begin by practicing both power-on and power-off stalls to
  familiarize the applicant with the aircraft's stall characteristics. Spin avoidance, incipient spins, actual spin entry, spin, and spin recovery techniques should be practiced from an altitude above 3,500 feet AGL.

  c. Spin avoidance training should consist of stalls and maneuvering during slow flight using realistic distractions such as those listed in Chapter 2. Performance is considered unsatisfactory if it becomes necessary for the instructor to take control of the aircraft to avoid a fully developed spin.

  d. Incipient spins should be practiced to train the instructor applicant to recover from a student's poorly performed stall or unusual attitude that could lead to a spin. Configure the aircraft for a power-on or power-off stall, and continue to apply back elevator pressure. As the stall occurs, apply right or left rudder and allow the nose to yaw toward the stalled wing. Release the spin inducing controls and recover as the spin begins by applying opposite rudder and forward elevator pressure. The instructor should discuss control application in the recovery.

  e. Spin entry, spin, and spin recovery should be demonstrated by the instructor and repeated in both directions by the applicant.

  (1) Apply the entry procedure for a power-off stall. As the airplane approaches a stall,
  smoothly apply full rudder in the direction of desired spin rotation and continue to apply back elevator to the limit of travel. The ailerons should be neutral.

  (2) Allow the spin to develop, and be fully recovered no later than one full turn.
  Observe the airspeed indicator during the spin and subsequent recovery to ensure that it does not reach the red line (VNE).

  (3) Follow the recovery procedures recommended by the manufacturer in the AFM or
  POH. In most aircraft, spin recovery techniques consist of retarding power (if in a powered aircraft), applying opposite rudder to slow the rotation, neutralizing the ailerons, applying positive forward elevator movement to break the stall, neutralizing the rudder as the spinning stops, and returning to level flight.

  f. During spin training if a spin is not fully developed, the aircraft may instead go into a spiral. A spiral may be recognized by a rapidly increasing airspeed after the attempted spin entry. In an actual spin, the airspeed normally stabilizes below stall speed). The pilot must recognize a spiral and initiate immediate recovery to prevent exceeding structural limits of the airplane.

  SPIN TRAINING AND PARACHUTES. Title 14 CFR part 91, § 91.307(c) prohibits the
  pilot of a civil aircraft from executing any intentional maneuver that exceeds 60° of bank relative to the horizon, or exceeds 30° nose-up or nose-down attitude relative to the horizon, unless an approved parachute is worn by each occupant (other than a crewmember). Section 91.307(d) states, in part, that § 91.307(c) does not apply to flight tests for a Pilot Certificate or rating, or spins and other flight maneuvers required by the regulations, for any certificate or rating when
  given by a certificated flight instructor (CFI) or an airline transport pilot (ATP) instructing in accordance with part 61, § 61.167.

  a. Section 61.183(i) requires an applicant for a Flight Instructor Certificate airplane or glider rating to receive flight training in stall awareness, spin entry, spins, and spin recovery procedures. The applicant must also possess and demonstrate instructional proficiency in these areas to receive the certificate or rating.

  b. Because spin entry, spins, and spin recovery are required for a Flight Instructor Certificate airplane or glider rating, a person receiving instruction from an authorized instructor need not wear an approved parachute while instruction is being provided in these maneuvers.

  The instructor providing the training is also not required to wear an approved parachute while providing this flight training.


Can a taildragger land tail first? Inspired by this question...

How does a taildragger take off? Does it rotate?

I imagine if a taildragger has to land front wheels first it has a very limited range of Angle of Attack (if the pilot wants to avoid a prop strike) during landing.

So do they land tail first by default?
If not would a tail first landing be an issue?

It's possible to land by touching the tail first, but this is undesirable as it puts a lot of stress on the tail, so it's not trained for and there are no circumstances where you would do this deliberately. There are two common methods of landing a tail-dragger: a three-point landing (where the tail and mainwheels touch together) and a wheel landing (where the mainwheels touch first).

Aircraft design

First, be aware that the aircraft is not level when it's on the ground, like a tricycle aircraft is. The tail position is set so that the aircraft is quite nose-up on the ground - in fact, the angle is about the same as the stalling angle, and the reason for this will become apparent. If your nose is on the horizon, the tail is off the ground (about five feet up in a Tiger Moth). Also, the prop is mounted higher up on a tail-dragger than on a tricycle, for exactly the reason you say. In the Tiger Moth, there is two or three feet of clearance between the ground and the prop if the nose is on the horizon.

The clearance itself isn't the direct problem. If you do go nose-down on the ground, the airplane is not stable. If you're moving forwards, the chief component of drag is acting through the mainwheels, so the engine thrust will tend to tip you further nose-forward (especially if you run over a hump or rabbit hole). In addition, the CG of the aircraft is closer to the mainwheels, and eventually goes in front of the mainwheels. If this happens, a prop strike is inevitable.

Three-point landings

Three-point landings are the default because the aircraft is fully controllable as soon as it touches down. The approach to the runway is done at low or idle power, and set you up to be flying level at rooftop height above the runway. As you lose speed (because you have idle power), you progressively pitch up to maintain height, which in turn causes you to lose more speed. This is called the flare Soon enough you are pitched up at the three-point attitude, and you can no longer maintain height - if you pitch up any further the wings will stall. At this point, you will drop down onto the ground and all three points will touch at once.

Wheel landings

Wheel landings are also used, as they offer more control in windy conditions, but they typically have a longer landing roll because you have more speed when you touch down. The approach is flown with some power on, but less than cruise power. It's a gradual descent towards the runway, and there's no flare, so you touch down in the level attitude. You then close the throttle to idle, and let the speed decay on the ground. As your speed decays and less lift is produced, you need to progressively push the stick forward to keep the tail from dropping, keeping the aircraft level as long as possible. Once the tail starts to drop, pull the stick back to drop the tail firmly onto the ground.

When do tail-first landings happen?

To reiterate, you never land tail-first deliberately. It offers very little control; the aircraft would stall at a higher speed (and therefore the landing roll is harder and longer); it puts undesirable load on the tail. They do sometimes happen by accident, if a student pilot has pitched up too aggressively when trying to do a three-point landing. Typically, too much nose-up input results in "ballooning" as the aircraft gains a little more height, but this results in the speed decreasing rapidly. If left uncorrected, the aircraft stalls, resulting in the tail touching down hard.


What controls the brightness of the MCDU display and keys? What brightness does the brt and dim on the right side of the MCDU MENU button change?
The brightness of the display, the keys or of both?
And if only one of them, what controls the other?

EDIT: As shown in this video, the brigghtness knob turns just the display on/regulates it's brightness.
What changes the brightness of the keys (They seem to be lit befor the MCDU is turned on)?

These buttons are to increase and decrease brightness of MCDU. Also, they are used to turn on and off the unit.

As explained here:

  BRT AND DIM KEYS
  Control the light intensity of the entire MCDU. MCDU power up is performed
  with the BRT key and MCDU shut down is performed with the DIM key.

And here:

  Repeatedly clicking on the "BRT" (the top of the paddle switch) will
  switch the unit on and increase the brightness. The reverse is also
  true. Repeatedly clicking on the "DIM" (the bottom of the paddle
  switch) will decrease the brightness and switch the unit off.


What is this hatch above the cockpit of a 747? There is a little door on the upper deck above the cockpit:

Source: Airliners.net, (modified to indicate location of hatch).

What is that door? What is its purpose?

It's an emergency escape hatch. There are inertial reels in the cockpit ceiling adjacent to the hatch to allow the cockpit crew to exit the airplane. See this link for an account of their use escaping the aircraft during a hijacking.

There were five reels in the 747-100/200 aircraft. The cockpit had five seats: pilot, co-pilot, flight engineer, and two observer seats.

It's also sometimes used in third world countries to send a guy out to clean the cockpit windshield. In Mumbai I once made the mistake of asking the windshield to be cleaned, thinking, of course, they'd do it with a cherry picker. Much to my surprise, bare feet appeared at the top of the windshield followed by this poor fellow who was maneuvering into place to clean the windshield. He had a rope tied around his waist, but had he fallen it would have been bad because the rope was anchored through the hatch, which meant he would have swung badly had he fallen.


Is there a cockpit which can recognize the voice of the pilot and help him/her to fly? Is there any new cockpit that uses voice commands (think for example Siri from the new iphones) that can identify the voice of the pilot and help him/her to fly?

No, voice recognition is currently not used in aircraft as it would have to be built into the aircraft to pass certification for the aircraft and with rotating crews on aircraft, the voice recognition would need to be able to work with too many different voice types: high pitch, low pitch, male, female, accents, dialects and many more factors.

Voice recognition works because it learns from the user over time, something that is not possible in a cockpit environment with crew resource management.

There is a prototype in development by Honeywell at the moment, but it's in early stages of development.

Related reading:
The benefits of a Speech Recognition enabled cockpit by AdacelPDF


How does the "pendulum effect" affect biplanes? A high wing airplane will correct itself (lateral stability) when disturbed because its c.g. is below the c.p. (looking at the plane from it's side), according to this forum post and the book below.

So my question is, how does this "pendulum effect" affect a biplane with two centres of pressure?

It will affect a biplane just as much as a monoplane.

Not at all.

The pendulum effect does not exist in airplanes. It does in airships, but not in heavier than air craft.

For a proper discussion, we should first define what a pendulum is. Only then can be established if such an effect can exist in airplanes.

Let's base the definition on Wikipedia. It says that

  A pendulum is a weight suspended from a pivot so that it can swing freely.

Maybe it is also worth to look closer what a pivot is: A thing on which something turns.

So the pendulum is fixed to a fulcrum which keeps it suspended and allows it to swing freely. The ideal pendulum has all its mass in its massive bob and, therefore, pivot and center of gravity are not in the same place. If the center of gravity and the pivot would fall together, a pendulum could only rotate but not swing. And that swinging motion is what the pendulum is all about.

Now for airplanes: Here we have no pivot. All rotation can only happen around the center of gravity. This is equivalent to the pendulum with no length which is no pendulum any more.

Lift is the sum of all pressure acting perpendicular to the direction of movement. Lift on a banked wing will also bank with it. The lift vector will still be in the plane of symmetry of the banked aircraft and will have no lever arm with the center of gravity, thus causing no uprighting rolling moment. The Figure 34 of your copied book page is simply wrong. The author did not know what he was talking about.

Edit especially for @JohnK:

I added an answer here about the rolling maneuver of paragliders. The description should make obvious that no pendulum effect is involved. Rather, the whole is quite similar to roll control in hang gliders where the lift is shifted sideways in order to create an imbalance, but then again different in wonderful ways. The discussion below would not allow me to explain my thoughts in such detail.


What exactly is a compressor stall? I hear the term "compressor stall" when talking about turbine engine difficulties.

What exactly does this mean? And how does a pilot diagnose and fix it - specifically, would there be any changes in the engine instruments compared to normal operation?

The spinning blades in the compressor stage of a jet engine or turbo fan are themselves airfoils, like the aircraft's wings. The operation of the engine depends on the smooth flow of air over the blades.

Just like a wing, an individual blade, or a small component of one, can experience an airfoil "stall", where the air flow over the blade separates into a cell of "stuck", highly turbulent air behind the blade, and the air flows around the cell instead of smoothly around the blade.

When a flow separation occurs, the airfoil's ability to push the air in proper direction at the right flow rate—and thereby contribute to the compression of air behind the fan assembly—is inhibited.

Since these blades are rotating, the blade quickly moves away from the packet of stagnant air. Of course the stalled air packet has some momentum from the intake air, and it will experience a drift along with the rotating blade, but it is not moving with the average flow of the air through the engine anymore.

Thus the next blade spinning round tends to encounter the stalled air packet. If the stalled air cell is not particularly large, it may be absorbed by the air flow at this stage and dissipated. Alternatively, it might be large enough to stall the subsequent blade as well. At this point, it is called a "rotational stall".

If the stall continues to propagate, the ability of the fan stage to deliver air to the subsequent compression stage is impeded, and it will lead to an abrupt drop in pressure inside the combustion chamber. This causes a reduction in available oxygen for combustion. The engine's performance, measured by the thrust delivered, is strongly impaired, and there is likely to be a lot of unburnt fuel remaining after the oxygen in the compressor is exhausted. That unburnt fuel may ignite in a bright exterior flame as it escapes out the back of the combustion chamber and mixes with the oxygen-rich bypass flow, or in the case of a jet engine, after it exits the engine altogether.

The drop in back pressure in the compressor will, under normal conditions, enable the compressor fan blades to begin operating as proper air foils again.

An alternative type of stall is a compressor surge. In this case, the problem is caused by unexpectedly high pressure in the combustion chamber (or in the compressor), which forces its way forward as well as backwards, against the incoming flow rate. Again, this disrupts the operation of the compressor blades as airfoils.

See Advanced Control of Turbofan Engines by Hanz Richte


How do wings generate lift? Just the basic question that every aviation enthusiast must be curious about: exactly how does a wing generate lift?

To get to the bottom of it, it might help to look at lift at a molecular level:
Every air molecule is in a dynamic equilibrium between inertial, pressure and viscous effects:

Inertial means that the mass of the particle wants to travel on as before and needs force to be convinced otherwise.
Pressure means that air particles oscillate all the time and bounce into other air particles. The more bouncing, the more force they exert on their surroundings.
Viscosity means that air molecules, because of this oscillation, tend to assume the speed and direction of their neighbors.

Flow over the upper side of the wing
Now to the airflow: When a wing approaches at subsonic speed, the low pressure area over its upper surface will suck in air ahead of it. See it this way: Above and downstream of a packet of air we have less bouncing of molecules (= less pressure), and now the undiminished bouncing of the air below and upstream of that packet will push its air molecules upwards and towards that wing. The packet of air will rise and accelerate towards the wing and be sucked into that low pressure area. Due to the acceleration, the packet will be stretched lengthwise and its pressure drops in sync with it picking up speed. Spreading happens in flow direction - the packet is distorted and stretched lengthwise, but contracts in the direction orthogonally to the flow. This contraction is needed to make space for that wing; in supersonic flow it will decelerate for the same purpose. Once there, it will "see" that the wing below it curves away from its path of travel, and if that path would remain unchanged, a vacuum between the wing and our packet of air would form. Reluctantly, the packet will change course and follow the wing's contour. This requires even lower pressure, to make the molecules change their direction. This fast-flowing, low-pressure air will in turn suck in new air ahead and below of it, will go on to decelerate and regain its old pressure over the rear half of the wing, and will flow off with its new flow direction.
Note that lift can only happen if the upper contour of the wing will slope downwards and away from the initial path of the air flowing around the wing's leading edge. This could either be camber or angle of attack - both will have the same effect. Since camber allows for a gradual change of the contour, it is more efficient than angle of attack.
Flow over the lower side of the wing
A packet of air which ends up below the wing will experience less uplift and acceleration, and in the convex part of highly cambered airfoils it will experience a compression. It also has to change its flow path, because the cambered and/or inclined wing will push the air below it downwards, creating more pressure and more bouncing from above for our packet below the wing. When both packets arrive at the trailing edge, they will have picked up some downward speed.

Behind the wing, both packets will continue along their downward path for a while due to inertia and push other air below them down and sideways. Above them, this air, having been pushed sideways before, will now fill the space above our two packets. Macroscopically, this looks like two big vortices. But the air in these vortices cannot act on the wing anymore, so it will not affect drag or lift. See here for more on that effect, including pretty pictures.
Lift can be explained in several, equivalent ways
Following the picture of a pressure field outlined above, lift is the difference of pressure between upper and lower surface of the wing. The molecules will bounce against the wing skin more at the lower side than at the upper side, and the difference is lift.
Or you look at the macroscopic picture: A certain mass of air has been accelerated downwards by the wing, and this required a force to act on that air. This force is what keeps the aircraft up in the air: Lift.
If you look at the wing as a black box and only pay attention to the impulse of the inflowing and outflowing air, the wing will change the impulse by adding a downward component. The reaction force of this impulse change is lift.
Either way, you will arrive at the same result. By the way: Most of the directional change happens in the forward part of the airfoil, not at the trailing edge!

Lift is a matter of definition
Lift and induced drag are both part of the pressures acting on the wing. If you add up all the pressure forces acting on a wing, their resulting vector will point slightly backwards. The streamwise component is drag, and the component orthogonal to the direction of movement is lift. This is just a defininion, made for simplicity.


Can I log time in an RV-12 towards a commercial certificate, and is it a TAA? Can I legally log hours flying RV-12 towards commercial airplane rating?

Does RV-12 qualify as a TAA?

Assuming that you are asking about the US, there are two parts to your question-total time and Complex/Turbine/TAA time.
As to whether the RV meets the requirements for a TAA that depends on what instrumentation/avionics it has. If it meets the definition, then you can use if for the training part of the aeronautical experience.

§61.129   Aeronautical experience.
(ii) 10 hours of training in a complex airplane, a turbine-powered
airplane, or a technically advanced airplane (TAA) that meets the
requirements of paragraph (j) of this section, or any combination
thereof. The airplane must be appropriate to land or sea for the
rating sought;

Further down in the reg it tells you what a TAA airplane is:

(j) Technically advanced airplane. Unless otherwise authorized by the
Administrator, a technically advanced airplane must be equipped with
an electronically advanced avionics system that includes the following
installed components:
(1) An electronic Primary Flight Display (PFD) that includes, at a
minimum, an airspeed indicator, turn coordinator, attitude indicator,
heading indicator, altimeter, and vertical speed indicator;
(2) An electronic Multifunction Display (MFD) that includes, at a
minimum, a moving map using Global Positioning System (GPS) navigation
with the aircraft position displayed;
(3) A two axis autopilot integrated with the navigation and heading
guidance system; and
(4) The display elements described in paragraphs (j)(1) and (2) of
this section must be continuously visible.

As for total time, read the regulation. An RV is an airplane so as long as you have at least 50 hours of the 250 in an airplane then you are good. You could do all 250 in the RV if you wanted.

(a) For an airplane single-engine rating. Except as provided in
paragraph (i) of this section, a person who applies for a commercial
pilot certificate with an airplane category and single-engine class
rating must log at least 250 hours of flight time as a pilot that
consists of at least:
(1) 100 hours in powered aircraft, of which 50 hours must be in
airplanes.…

You are no longer required to take the practical test in a complex or TAA airplane, so no matter what instrumentation/avionics it has you can use it for your practical.


What do the pointers on a Kollsman altimeter indicate? In this thread: What type of altimeter is this?

there are 3 images of altimeters that have a pointer that moves around the outside diameter of the scale markings and they have another pointer that moves around the inside diameter of the scale markings, e.g 4 and 5 on this picture.

(Source)

What is the purpose of the triangles (4 and 5)?
What are the units or multiples used?

If possible, please give an example of what one of these is indicating. I mean like: so many feet of some kind of altitude.

I found some sources of definite information, so I will answer this to confirm the suggestion made in a comment that Federico referred to in his answer. Also to fill in the details of what the OP asks.

Triangles 4 and 5 indicate the altitude difference between ISA pressure at sea level and the pressure set in the Kollsman window.

TM 1-205 Air Navigation 1940, Chapter 1, Section VII, Paragraph 52, Altimeter, beginning on page 66, at https://archive.org/details/TM1-205 has an explanation about these triangles, or as they were called "reference markers".

This post at https://www.pilotsofamerica.com/community/threads/blue-and-yellow-does-anyone-remember.79471/ beginning at post #11 discusses altimeters with these markers. Post #25 has a link to an article in the January 1948 issue of Flying Magazine that has a very good explanation of altimeters and these reference markers.

Triangle 5 shows if an altitude difference is higher or lower by which side of the 0 it is on. A higher difference is to the right of the 0 and a lower difference is to the left of the 0. This is in thousands of feet.

Triangle 4 reads in hundreds of feet. Which way you read it depends on which side of the 0 triangle 5 is on.

In the image in this thread, the altimeter setting is 30.1. To see what the difference should be, I used TM 55-6610-247-40 Table 3-1. Altitude Pressure Table, Feet VS Inches of Mercury. I got this TM from http://www.liberatedmanuals.com it says that the altitude difference would be -165 feet.

Triangle 5 is to the left of the 0, between it and -200 feet on the thousands scale. Since triangle 5 is on the left side of the 0, triangle 4 is read from that side and shows -160 feet.

A couple more examples from the thread referenced in the OP What type of altimeter is this?

In the top image the Kollsman window is blanked out. According to TM 1-205 page 68, (3), this is because the limit of the pressure range has been reached. In this case, at the upper limit. The triangles indicate approximately -2380 feet, which would be in excess of 32 inHg.

The bottom altimeter is set to 29.16. According to the table mentioned above, the difference is 711 feet. The triangles are showing this value. Triangle 4 is read from the right side of the zero, because triangle 5 is to the right of the 0.


Why didn't Boeing or Douglas make a jet airliner before the British DH Comet? I was looking at the history of commercial aircraft and was wondering why UK-based De Havilland was the first to produce a jet powered airliner (the DH 106 Comet) when the US had a much bigger civil aviation industry at the time, such as Boeing and Douglas? They only produced their Boeing 707 and DC-8 after the Comet was introduced.

So did Canada with the Avro  Canada Jetliner, at exactly the same time pretty much.  The Jetliner was complementary to the Comet, being a shorter range intercity airplane.  It made a sales tour of the US in 1950 and was a huge sensation.  Avro Canada was ordered to set the project aside for the  CF-100 All Weather Interceptor program during the early 50s so Avro Canada had to decline US airline interest resulting from its sales tour (and a bizarre Howard Hughes/TWA subplot) and the program never really got traction after that as the company went on to put all its resources into the Arrow supersonic interceptor program by the mid 50s.  Odd that the Jetliner had its legs cut out from under it by government politics (the Jetliner was initially designed to a state-owned Trans Canada Airlines specification, who later back out) and the Comet by a fatal design flaw, so in the end Boeing prevailed anyway.

The main reason for the US lag was that jet engines were considered by private US airlines to be too immature as a technology to be used for commercial travel in the late 40s, so there was little market interest in the US until an actual aircraft was demonstrated (one factor: first generation commercial turbojets with crude fuel controllers, like the Jetliner's RR Derwents, were very difficult to manage).  On the other hand, both the Comet and Jetliner were developed as products for state owned airlines (BOAC and Trans Canada Airlines) wanting to be bold, so they were ostensibly private ventures but with a "guaranteed" state buyer for at least initial production, providing a huge leg up.

There was no US equivalent in the private airline sector in the late 40s/early 50s, only the US military, where the 707 actually got its start.


Why are there no Mach 4+ fighter planes? Why are there no Mach 4+ fighter aircraft?  It seems that such aircraft would have massive advantages when it comes to being able to fire longer range missiles and evade return fire.

Today's fighter are designed with a max speed around mach 2 (max speed is generally calculated with no emport and 50% fuel, the operational top speed is way lower). They keep this ability to pass Mach 1 only to be able to respond fast enough to intercept / air policing missions.

Countries do not design very fast fighters (and planes in general) because :

It's extremely hard to achieve.
It does not give any advantage.
It has no use anymore.

Back in the cold war period, radars and SAMs where not very sophisticated yet, they did not see very far and Ground to Air missiles were not able to get very high. So to protect their airspace from potential intruders / enemy bombers, countries were relying on interceptor aircraft, a fast jet able to catch up the target before it gets to its objective.
At this time, going very fast, very high was an advantage : SAMs where not threatening. The US made a very successful reconnaissance plane exploiting that: the SR-71 Blackbird (max speed : mach 3.3). Many missiles were fired towards the SR-71, none reached its target.

Speed was used for intercept and reconnaissance / intel.

But radars and SAMs improved, getting more range, becoming able to threaten very fast planes. Also satellite images got better and better. The need for very fast interceptors decreased as radar range increased, and the need for very fast recon aircraft decreased as satellite images got better.

Now why does going very very fast not give any advantage to a fighter? Because you cannot turn.
The thing to keep in mind is G force: force the same turn rate, the faster you go, the more g you have to take. And a human can sustain a very limited amount of g. This means a plane going at Mach 4 will barely be able to turn without blacking out its pilot. And if you can't turn, you won't evade enemy missiles, making useless the bit more range gained on the missiles.

And then there is the technical challenge, dealing with a little drag as possible (that means no missile / bomb / fuel under the wings), heat, airframe deformation and wear ... for an advantage which isn't there anymore.

Despite all that, the US are suspected to work on a Mach 6+ aircraft, probably unpiloted.

(Please keep in mind that I simplified a lot of things to not make this post too complex)


Is training and pay different for cargo and airline pilots? Do cargo pilots receive different training than airline pilots? Are there notable differences in salary or other benefits?

My assumption is that since cargo pilots do not have to deal with passengers, passenger emergencies, or bear the responsibility of passenger lives, they may have less training and/or earn less than their airline counterparts.

Do cargo pilots receive different training than airline pilots?

First, cargo carriers are airlines just as passenger carriers are airlines, and cargo pilots are airline pilots. In the U.S. there is no difference in the training and certification of pilots dependent on whether they fly passengers or cargo. Also, be aware that airlines you generally think of as passenger carriers can also be operating freighters as well as carrying cargo on pax flights.

Whether there are passengers or cargo in the back, the airplane is having to operate in the same airspace, and a given aircraft model, whether in pax or cargo configuration, is essentially the same insofar as flying the aircraft. Indeed, at each of the two 747 carriers I flew for, we had both pax and all-cargo aircraft, and which we were flying made no difference in our pay rate. Pay rate is typically dependent on equipment flown, union contracts, and other considerations, but not on whether there are boxes or people in the back.

There are a few differences in flying pax versus flying cargo. Some that I can think of offhand are:

With pax and within 4000 feet of the ground we limited our bank to 20 degrees unless in cloud.
With pax we tried to avoid turbulence in general. With cargo not so much. Boxes don't complain.
With pax you are less likely to be concerned about weight and balance. Pax weight and balance is relatively simple, cargo weight and balance can be more of a problem.
With pax, you of course can have passenger problems, but those are almost always handled by the cabin crew. Only once did I feel that I really had to go back to the cabin, and that was because we had an inexperienced purser. Even then I could have sent the flight engineer or first officer, but I was bored.
With cargo, you don't have to worry about passenger announcements.
With cargo, you don't have to worry about dinging the flight attendants going through 10,000 feet.

Cargo is more fun, in my opinion, insofar as flying the airplane; you feel free to do things that you might not do with pax.

Pax is more fun on layovers, and you don't have to get your own meals, drinks, etc in flight, although I flew 3-man cockpits and the flight engineer often took care of getting those things on cargo flights.

Pax can be a problem on layovers where they're depending on the full crew being available the next day, because flight attendants increase the number of required crew members, and thus the greater the chance that somebody will get sick, get beat up, get in trouble with the law, get hit by a car, or run out of money and hit up the captain for an emergency loan. I had all of those happen .

Finally, arguably the life that the pilot is most interested in preserving is her/his own. Get yourself to the destination safely. What's in the back of the airplane will follow.


Flying in a helicopter with open doors: why don't people fall out? This has been puzzling for quite a long time.

Every action movie or military documentary features helicopters with no door or with open doors and yet people inside look like they couldn't care less. Apparently they're not falling out...

Why is it so?

Aircraft, fixed-wing or rotorcraft, have limited capability to produce a sideways force, so they simply can't throw you out.

It is a matter of physics. Inertial forces (gravity and centrifugal force) act on you and the aircraft the same, so they won't make you move relative to the aircraft. The only force between you and the seat is caused by the aerodynamic forces. And the wing or rotor can only produce significant force vertically, and some torque with help of control surfaces. But for lateral force there is only drag of the fuselage and the vertical stabilizer and, in most helicopters, anti-torque rotor, which don't produce that much force unless there is really bad turbulence or in some cases if the handling is really bad.

When aircraft turns, it banks to be able to produce the necessary side force, so the resulting force is still mostly straight to the floor.

Of course the other reason is that all aircraft and helicopters have seat-belts and the people sitting by open door usually have them on—except for skydivers, who have the parachute on already, and rescue divers who are tied to the winch instead.


Other aircraft doesn't apply right of way rules I was flying VFR a couple of days ago and was warned by ATC that another aircraft was coming from my left to my right.

At some point I saw it and we were clearly converging and getting pretty close.
According to the right of way rules I had priority, but the other aircraft didn't change its heading (maybe the other pilot didn't see me - he/she didn't seem to be in contact with ATC).

According to the rules I was supposed to keep flying the same heading and altitude but I decided to turn left to avoid her and it worked fine - however I can see how it could have been dangerous had the other aircraft changed its heading at the same time.

So I'm now wondering:

What is the "right thing" to do when another aircraft doesn't follow the right of way rules?

See and avoid is the backbone of VFR flight. The right thing to do when there is a potential collision is to take positive action, which is exactly what you did. There's no one-size-fits-all solution as to whether to turn one way or the other, climb or descend - it all depends on the position and course of the aircraft in question.

Often which way to turn in these situations is the lesser of two evils, if you turn left you clear sooner but if the other airplane turns right there's a potential conflict, if you turn right then you are in potential conflict longer. You have to choose one and hope the other person takes the right action.

One way to avoid conflict is a change of altitude, if you are slightly higher than the other airplane then climbing quickly takes you out of conflict, if you are lower then a descent does the same thing. If you are the same altitude then I favor descending as most people's default reaction is to climb - if the other pilot sees you they're more likely to pull up, giving you better separation. Even if you are under ATC direction changing altitude is the right action as it's necessary for the safety of the flight. You change altitude, avoid the collision, then go back to your assigned altitude before radioing ATC and explaining the deviation. I doubt they'd have a problem with that and even if they did regulations are on your side.


How much weight does removing a vacuum system really save? For a small GA aircraft (e.g. Piper, Cessna, Mooney), does anyone have a before and after weight savings example from removing a vacuum system?  E.g. calculated weight of component removal during W&B?

The context is replacing a standby attitude indicator with an electronic standby (e.g. MidContinent, Sandia SAI 340, etc)..

This question specifically refers to the vacuum system only, not the instruments themselves.  E.g. vacuum pump, hoses, fittings, etc.  Thanks!!

I removed the vacuum system in my VariEze a couple of years ago and saved 12 lb including the artificial horizon and heading indicator.  Probably about half of that was the instruments, the rest being in the pump/hose/regulator/filter/fittings.


Why is this missile positioned in this odd position? How can it be launched correctly? How this missile is positioned here in this odd position? How this can be launched right from this jet?

You're seeing the Sidewinder on the folded up wingtip of the F-18 that is in the foreground out of frame except for its wing tip and missile sticking up at the bottom.  The airplane is between the camera and the adjacent F-18 who's canopy is visible.  The long lens being used foreshortens and compresses everything distance wise so it looks like the missile is 6 inches from the canopy when it's actually probably 20-30 ft closer to the camera.


Why do airline pilots have shoulder harnesses? On airliners, passenger seatbelts are simple lap belts. However, flight crews seem to have at least shoulder straps, and often five-point harnesses. Why do flight crew have more restraints?

pilots need to be able to do work during turbulence.
passengers don't really like to be fully restrained.


What are the prerequisites to join a flight School ? Is it different for each country? (I didn't finish Highschool, failed French and math fml)

I've finished my 3 year diploma in Architecture.
I'm 23. Nobody has ever supported me and my dream to be a pilot. Not even my parents, heck they even found it funny, that I could even dream that.

But I'm not gonna stop till I drop.
I just wanna know if flight schools need a student to be a highschool graduate. Cause I've only got GCSEs no A levels.
  I have 6 GCSEs with physics chemistry and math being 3 of them, and C grade on most. Does that help?

What makes you think you can manage the exams for flight school if you can't even pass a high school exam?

They're at at least the same level of complexity...

But no, in general you don't need a minimum education level to start flight training. That said, if you want to get hired as a commercial pilot at some point, many employers WILL have education requirements without which they won't give you a job.

This is for EASA requirements, which are in use in the UK where you seem to be located. And of course individual flight schools may well decide to not take on people they expect to not have the capability to pass the exams, as having a high rate of failure on exams may reflect poorly on them. But that's not a legal requirement and would be a policy of the specific company in question.


How is propeller thrust vector accurately expressed for airplanes and multirotors? For propellers, as the airspeed increases thrust decreases. Is the airspeed component taken as a vector quantity perpendicular to the propeller? If that's true, then it's quite easy to visualize in the case of airplanes.

However, for quadcopters can the forward component of the thrust vector of a quadcopter type rotor be expressed as:

$$
V_q\cdot{sin}\theta_t
$$

Where:

$V_q$ is the forward airspeed of the quadcopter, and
$\theta_t$ is the angle of rotor tilt

Is this an accurate expression of the thrust vector?

The term
$$V_q\cdot{sin}\theta_t$$
is a speed, not a force, so it cannot be an accurate expression of the thrust vector.

Propellers accelerate the air flowing through the propeller disc in the direction of the propeller axis (or perpendicular to the propeller disc), so the force is only parallel to the propeller axis when the airspeed is aligned with the propeller axis. If the airspeed is at an angle to the propeller axis, the thrust vector is tilted towards the airspeed vector. The magnitude of this tilt depends on the speed increase of the propeller stream relative to airspeed.


Which evacuation incidents were followed by a large fire? Are there statistics about how many Aircraft emergency evacuation incidents (land-based) in the recent past (say, last 10 years) actually were followed by significant fires?

By "significant" I mean fires large enough to spread to the passenger cabins in spite of fire fighting attempts & which may conceivably have led to fatalities had passengers still been on board.

The context of what I am asking is: Are we doing a good job balancing the upside & downside risks of an Evac? Keeping in mind that most some Evacs can come with serious injuries to passengers.

I doubt there is a worldwide statistics.

The accidents, where actual fire broke and did cause significant damage will be well known and listed on the aviation safety network. However the precautionary evacuations that turned out to be false alarms and when nobody was seriously injured may fall through the cracks and not get reported anywhere. They should be reported to the overseeing safety board and that usually publishes at least summary list, but the system works better in some countries and less in other [1]. And there is no central store for these reports in either case, so you could try to collect the numbers for one country (according to [1], the reports are probably most complete for Canada), but that will be too few cases for decent statistics and worldwide data will be incomplete to the point of being useless.

However, I am pretty sure the balancing is right. Not only do fires happen, but when they do, they are fast. The China Airlines flight 120 at Okinawa on Aug. 20th 2007 burnt down in about 5 minutes. The first explosion occurred just few seconds after the last passenger left the plane and while the flight crew was evacuating. So if they waited any longer, it is quite likely someone would have died.

In contrast most evacuations don't result in injuries and the few cases are mostly bruises, some sprained ankles and if someone has really bad luck, some broken leg or hand.

The broken bones (and not sure, but I think even the sprained ankles) count as serious injuries. So that's the options the captain is comparing. If they command evacuation, somebody might break a leg, but if they don't and the fire is real, somebody will die. And they must decide in couple of seconds for the evacuation to be successful. So they would obviously err on the side of caution and command the evacuation if they have a good reason to think there might be a fire.


How many aircraft types can a 135 pilot be assigned to? Is there a limit to how many aircraft types a §135 operator may assign a pilot to fly? In other words, could a pilot type rated to fly—for example—a Learjet 75, Citation X, and Challenger 300 be assigned by the §135 certificate holder to fly all three of these types in §135 operations at any given time? Would that pilot be limited—for example—to only two types at a time for the purposes of §135 flight operations? I am not considering flight assignments that are to be conducted under §91. Is there a difference if the pilot is assigned as PIC or SIC?

I ask because my understanding has been that a §135 operator may assign a pilot to a maximum of two aircraft types at a time. However, I cannot find any documentation or discussion to support this.

Edit: To be clear, I am not asking about how many type ratings an FAA certified pilot is allowed to acquire in total (the answer to that question is: no limit). I am asking about what §135 operators are authorized to do, as far as assigning flight crew to various aircraft types.

There is no FAA regulation limit for the number of types a Part 135 pilot can be assigned to, providing all training programs are followed.  Insurance and safety auditing companies usually have guidelines requiring no more than 2 types to be assigned at a time so the 2 aircraft limit has become something of an industry standard.

There may be non-US regulations that address this issue.


What Boeing 747 rejected takeoff and runway excursion accident is detailed in this video? This video details with an example why not to reject takeoff after $V_1$.

It contains an example of a 747 running off the end of the runway, due to a rejected takeoff past $V_1$ prompted by an engine fire warning. It would appear to be a -200 combi variant with rear cargo door. Faint 'Air France' titles are visible.

What aircraft and flight was this?

The copilot rejected the takeoff above V1 in response to the engine fire warning.

The aircraft in question:

Air France plane operating as flight 187
Boeing 747-200 SCD (side cargo door) registration N4506H
Aircraft had company number 22794 and manufacturer serial number 558.

The incident occurred on the 24 of July 1988 at Delhi airport. An overview can be found here.


What's the formula to calculate static air temperature? What's the formula to calculate external temperature (static temperature) of an aircraft, given that I have Mach, TAS and altitude?

Since I don't know the formula, I tried to search on Google. But I found that I need total air temperature, which must be know by a sensor (and I don't know). So, is there any other formular/way to calculate static air temperature using only mach/tas/altitude, or is not possible with only these data?

is there any other formular/way to calculate static air temperature using only mach/tas/altitude ?

No.

Mach (or TAS) can only give you the ratio between total and static air temperature, as seen also on Wikipedia:

$$ \frac{T_\mathrm{total}}{T_{s}}={1+\frac{\gamma -1}{2}M_a^2} $$

Knowing the Mach number will give you the quantity on the right hand side of the equation ($\gamma$ is constant and is about 1.4 for dry air). If you cannot measure one of the two quantities on the left hand side, you cannot derive the other.

You could in theory derive the temperature from a measurement of the static pressure, if somehow you could also measure the air density, but that's not using only "mach/tas/altitude" as you requested.

A final option is to derive the temperature from the standard atmosphere model using the altitude, but that might not be a number reliable enough for your purposes.


For purposes of the FAA instrument written, which system becomes primary for pitch following an AHRS failure? Sheppard Air claims to have questions exactly from the FAA test. I'm wondering what folks think of the Q&A for this one. It asks

In the event of an AHRS failure, what becomes your primary pitch instrument?

The given answers are

PFD altimeter
Standby altimeter
Standby attitude indicator

I thought (2) was correct, but they give (1).
What I find puzzling about this choice is that the AHRS is a measurement system that displays its output on the PFD. So if the AHRS has failed, the PFD will too. The section of the FAA handbook in their explanation refers to using the PFD altimeter for partial panel attitude reference, but says nothing about the context being failure of the AHRS. I'm wondering if I misunderstand what's meant by "PFD" and "AHRS", or is this just stupid FAA word games? (Or a Sheppard Air mistake?)

The AHRS is the Attitude and Heading Reference System. It is synonymous to the Gyroscopic systems of a steam gauge aircraft.
The ADC or Air Data Computer is synonymous to the pitot-static system in a steam gauge aircraft. Just like a steam gauge aircraft, the AHRS and the ADC are two separate systems. And, for good reason. They compliment each other while at the same time providing a redundant backup when needing to fly partial panel.
The PFD is the Primary Flight Display. It is synonymous to your PC computer monitor. If your PC is not working, it does not mean that your monitor won’t work. And if your PFD does not work, a TAA will have an MFD (Multi-Function Display) that can display the same info.
That being said, the AHRS is not as important in VFR flight as the ADC. Ask yourself the question of which parts of the AHRS are required by subsections b & c of Title 14 Code of Federal Regulations Part 91.205. No gyroscopic instrument is required by 91.205 for VFR flight. As long as the magnetometers are working and displaying properly, you are still capable of flying relatively safely. Even if the magnetometers are inoperative, you should still have your magnetic compass to meet the requirements of sub-section b.


Can the cockpit windows on commercial airliners open during flight? I  observed that the cockpit windows on the commercial airliners actually open - good for a hot day while waiting on the airfield, I suppose. Is there a mechanism which prevents the window from being opened when airborne?

I'm sure that the cabin pressure difference prevents this at altitude when the cabin is pressurized, due that they often slide inwards and then to the side.

That being said, Boeing produced a video showing that it's no problem flying with an open window on the 737 if say it opens on takeoff. You can close it assuming it's not damaged or you can land with it. They also showed that the side window can be opened in flight in case for instance visibility is impaired through the main window, and while it hardly looks comfortable, it can be done. This assumes that the cabin is unpressurized.

The sort of thing you might be thinking about is a cooper vane, but I don't think any aircraft have those on the cockpit windows.


Experiences with LiFePO4 starter batteries in light aircraft or motorized gliders? I am interested in real-life experiences to do with using LiFePO4 batteries in light aircraft and motorized gliders compared to standard PbA ones. LiFePO4 seem to be a very attractive alternative to the good ole lead ballast with regard to weight/size and useable capacity.

Points of interest include amongst others:

Operation safety
Handling (e.g. with regard to charging)
Robustness (electric, mechanical)
Compatibility (electric, fittings etc.)
Cost vs. Benefit assessment
Temperature influence
Life expectancy
Technical / legal admission (e.g. insurance-related)
...

Well, I'll start by saying that (at least to my knowledge, in the USA) there are no certificated/PMA'd/TSO'd LiFePO4 batteries currently available on the market for use in certificated airframes.
That means if you're using a type-certificated aircraft (or an LSA that didn't ship with one originally and for which there is no manufacturer-approved procedure to install one) you're basically out of luck unless you can convince your local FSDO to approve it as a one-off modification to your airframe.

That said, there are some people using them in homebuilts. This guy, for example has used one on his SQ2000 to replace the starter/cranking battery, and there's a company called AeroLithium that sells aviation lithium batteries (albeit uncertified) which some folks seem to be using in (experimental) Carbon Cubs with a good deal of success.

As to the batteries themselves, my aircraft is certificated, I've got no desire to take it experimental, and my relationship with the local FSDO is not one where I could just walk in and say "I want to stick one of these in my plane. Sign off on the 337 form KTHXBYE!" so this is all just theoretical:

Operationally, LiFePO4 is a relatively safe chemistry.
Unlike conventional lead-acid batteries it's not going to spit sulfuric acid on your plane during charging or hard maneuvering.  Unlike other Lithium-based chemistries (say Lithium-Cobalt of Dreamliner fire fame) it's not as prone to blowing up or catching fire if short-circuited or otherwise abused (though puncturing it is still a Bad Thing).
Note however that as LiFePO4 is a lithium based chemistry water may not be the best extinguishing agent for a ruptured/burning battery. One of the potential decomposition products of a burning or ruptured LiFePO4 battery in the presence of water is Hydrogen Fluoride (HF), which is rather nasty stuff.
Handling and Charging is generally normal - as in you can connect it to your aircraft charging system with appropriately-rated breakers/fuses.
Checking cell balance is recommended periodically, but without adequate information on the use of these batteries in aircraft we can't say what "periodically" means -- Every 10 hours? Every 50? Annually? (If installing one of these in a homebuilt I'd start with every 10 hours and work from there).
Robustness should be superior to lead-acid batteries in all respects (mechanical and electrical).
For use in an aircraft a sturdy housing around the cells would be a Must Have to prevent the battery from being ruptured in the event of an incident, but that could be produced reasonably.
Electrically LiFePO4 has a lower self-discharge rate, better tolerance for overcharging, and better (flatter) discharge curves - all Good Things.  It is also stable over a wide range of temperatures, and at least theoretically will outlast lead-acid batteries on a charge/discharge cycle and calendar-year basis (though again, without real-world utilization data we can't really say anything for sure here).
Cost-Benefit is hard to qualify.
LiFePO4 batteries can be had cheaper than "aircraft batteries", largely owing to the fact that they're not approved for use in certificated aircraft.
Because of their higher energy density they're also substantially lighter for the same amp-hour capacity, which is always attractive when we're talking about aircraft applications.
All of those benefits aren't worth a warm bucket of spit to me because I can't install one in my airplane (though I'd certainly consider it seriously if it were a viable option).  If you can install one in your airplane as a replacement for your main battery it may well be worth considering.