What is this air-scoop behind the cockpit of the Polikarpov I-153 and Stearman? (Source)

There is a Ferrari-looking air-scoop behind the cockpit of the I-153 and most of the Stearman planes too.

What is that?

(Source)

The F1 air-scoop / airbox is well clear of the driver's head to feed air into the engine (the airbox itself is shaped so that each cylinder gets equal share of air).

In your 3-view diagram, that's a streamlined headrest for drag reduction.

The I-153 has a top speed of 444 km/h (243 knots, 280 mph), whereas such streamlining is not needed for the leisurely paced Tiger Moth, for example.

Googling photographs makes it clear, unlike that line drawing.

(Source) Click to view.


Why was the experimental MiG 1.44 so similar to the experimental TKF-90? Why was the MiG 1.44 so similar to the MBB TKF-90? (for some information on the TKF-90 you have to scroll down this question, it is the only one source I knew about this particular plane)

Here is the MiG 1.44:

(source)

Here is the TKF-90

(source)

For me, these two aircraft are nearly unrecognizable. They were adversaries in those times, not partners. Has that similarity arised only because of the similar expectations from these airplanes?

I once led a group of Antonov engineers through the aircraft exhibition of the Deutsches Museum in Unterschleissheim near Munich. There are two halls connected by a walkway, and from that walkway you can see the restoration workshop which is located between those halls.

When the group had long left the walkway, one engineer still stood in the middle of it and gazed down at the Dornier Do-31 which at that time stood in the shop for cleaning and repairs after many years in the open. I walked back (with one of our interpreters) and asked him what fascinated him. He said to me that this was the first time he saw this aircraft in person. And he continued that he knows every rivet in it. He had studied it in the early Seventies for several years when Antonov was tasked with developing a VTOL transport aircraft. In the end, they abandoned the idea (like NATO did a few years earlier), but this airplane had been the center of a part of his life.

Don't think bad of this - it is just good engineering practice to study what others have done. If you want to develop something, look what others have done before you and try not to repeat their mistakes. You might as well marvel at the similarities between an F-15 and a Su-27, a Concorde and a Tu-144, or a Space Shuttle and a Buran. In the end, they were designs made for the same purpose, and it is no wonder that they turned out alike. It just means the engineers did their job properly.

In nature this is called convergent evolution.


What factors are involved in determining the spanwise pitching moment distribution? Assuming that I have a known $C_M$ (pitching moment coefficient), $C_L^{'}$ (lift per unit span) and wing geometry, how would I determine the spanwise pitching moment distribution?

Which point on the section of the aerofoil would I take moments about?

Would the weight of a propulsive produce a pitching moment and hence affect the pitching moment distribution?

In order to answer this question you need to know the detailed construction of the wing. In particular, the elastic center of each wing section is important. A simple way to find it would be to cut a cardboard into the cross section of the wing. Adjust local thickness according to skin panel thickness. Now find the center of gravity of this piece of cardboard, and you know where the elastic center is. Note that this only works for a closed torsion box; open sections tend to have their elastic center outside of their circumference.

The Free Dictionary has this definition for the elastic center:

  A point within a wing section at which application of a concentrated
  load will cause the wing to deflect without rotation. This is the
  point in the wing section at which rotation will occur when the wing
  is subjected to a twist.

Now you need to calculate the distance between the elastic center and the quarter point, around which the pitch moment coefficient is defined. This, multiplied by the local lift coefficient, will give you the offset moment which you need to add to the pitch moment in order to calculate the total moment twisting the wing.

  Which point on the section of the aerofoil would I take moments about?

That depends what moments you want to know. Aerodynamic moments are defined around the quarter point. If you want to calculate the aeroelastic twist of the wing, you need to use the elastic center.

  Would the weight of an engine produce a pitching moment and hence
  affect the pitching moment distribution?

Masses produce moments which depend on load factor while aerodynamic forces depend on dynamic pressure. Yes, you need to add masses and their moments around the elastic center, and you need to do this separately for each speed at which you do the calculation.


Are aircraft tyre sizes standardised? Are tyres custom designed for each new aircraft model or is there a lot of standardization & cross use across models? When a designer starts on a new model is there a list of standard tire sizes to choose from?

Is the situation similar for general aviation / military aircraft?

Aircraft tires are indeed standardized by size and specification and with applications across models.

There is certainly a long list of available sizes and variations, just as with automotive tires. When needed for a new aircraft type design, these existing tire models are available to be incorporated into that design.

There are certainly many aircraft types that have necessitated special tire specifications through the history of aviation development, especially with the more esoteric military aircraft. Of course, this is how that extensive list of available tires came to be.

Aircraft tires are dimensioned by several measurements (as depicted in the images below):

Outside Diameter (A),
Cross Sectional Width (B),
and Inner (Rim) Diameter (C).

These dimensions will be noted as AxB-C. In some cases the A is left out for a B-C notation (see examples in the table of "Type III Nylon Tube Type Tires" below).

Image Source

Image Source

Air Hawk tires are one brand that I handle frequently; their tire products give a good representation of the generic sizes and specifications available. Follow the above link for examples from their online catalog.

See also this excerpt from their Aircraft Tires Specifications sheet showing examples of common dimensions and plys:

Goodyear has an exhaustive databook covering technical specifications for their commercial and military aircraft tires.

See that here: The Aircraft Tire DataBook

  Specific data on the proper tire sizes for different aircraft main and
  auxiliary/nose gear, speed ratings, nominal inflation pressures,
  dimensions, and other data needed by users to obtain the maximum
  service from their aircraft tires are presented in this booklet.


What is lifting force of V-22 Osprey? Is any other than the two rotors? Picture is from here.

Is any other force to lift the V22 other than its rotors? Is any possibility that the power plants their self are not generating thrust? I was just wondered that such short propellers can lift (especially when VTOL) the aircraft even with additional heavy humvee.

The lift is provided by the rotors only. The rotors are powered by Rolls-Royce T406 engines, which are turboshafts: all useful generated turbine power is converted into shaft power for the rotors. Note that turboprops do convert some of the exhaust energy directly into propulsion thrust, turboshafts do not.

All helicopters can provide enough rotor thrust to lift their own weight plus that of (internal or external) payload. Wikipedia lists the max. VTOL weight as 23,859 kg, about the same as the CH-47 Chinook double rotor helicopter at 22,680 kg. The Chinook rotors are indeed longer and therefore require less power to generate the same amount of thrust: 4,590 kW for the V-22, 3,529 kW for the Chinook.


Could a plane land on specialized vehicles if its landing gear failed? This (fake) video has stirred up a lot of questions online about whether such a scenario would be possible in reality - and the answer to those questions appears to be a resounding "No, that's very implausible."

But most of those answers seem to focus on the specifics of the Nissan truck - it would exceed its rated weight tolerance, it probably wouldn't be able to match the plane's speed...

What if an airport had specialized vehicles for this sort of thing, Thunderbirds-style? Could such vehicles be built, or would the engineering challenges just be too great to overcome?

Smaller planes can pull it off, here is video from a weekend airshow somewhere.
http://digg.com/video/plane-lands-on-truck
Bigger planes, that's a lot weight. Even my Cessna Cardinal (4 passenger) could weigh close to 2500 lbs landing, basically a whole nother car on top of a truck.  Maybe a car carrier would be good, longer landing ramp, clear front to fly over if needed.

Jets, that's a lot more speed to match up with.


Cruise Mach Number less or more than Critical Mach Number Do commercial airplanes cruise at Mach number higher than the critical Mach number? And what is the critical Mach number of airplanes like B777 or A330?

The critical Mach number $M_{crit}$ is defined as the lowest Mach number at which the airflow over some point over the airfoil reaches supersonic speed, that is, Mach 1. Usually, flying greater than $M_{crit}$ will produce a normal shockwave perpendicular to the flow, at the point of minimum pressure on the airfoil. I must note that if flying slightly above $M_{crit}$, there is a possibility of the isentropic recompression of the fluid, which means that no shockwave will be formed and thus no losses in form of the entropy will occur. This is especially the case with supercritical airfoils flying slightly above $M_{crit}$.

Critical Mach number for a typical transonic airliner is not equal to divergence Mach number $M_{dd}$. In fact, many aircraft will exceed $M_{crit}$ during the cruise, which you can see on the following video:

            . I believe that the average value of $M_{crit}$ is around $0.78$ for today's airliners like A320 or B737.

Exceeding $M_{crit}$ does not mean the aircraft reached $M_{dd}$ or is about to lose control. Control difficulties may be possible if $M_{mo}$ is exceeded.

For A320 and B737, the maximum operating Mach number $M_{mo}$ is $0.82$. This is primarily due to the buffet (and ultimately high-speed stall/shock stall) and (or) flutter occurrence. Exceeding normal speed range may cause flutter to appear. It also may put the aircraft in grave danger if shock stall occurs. Shock stall will occur if the shockwave formed on the airfoil is too powerful and separates the boundary layer. In this case, the airfoil pressure distribution changes and introduces an intensive nose-down pitching moment. To avoid such scenarios, the aircraft are limited with Mach number as well. There might be some corrections on the $M_{mo}$ from the divergence Mach number standpoint, but $M_{dd}$ is not the primary reason why such aircraft are limited with respect to Mach number.


What are the roles of the co-pilot in commercial aviation? I am currently doing a project(in college) on the history and future of the role of a co-pilot and to start it off I wanted to just summarize what the roles of the co-pilot are.

Firstly, "co-pilot" is not a term that is really used anymore. When people say that they usually mean the First Officer. It's a bugbear of mine because "co-pilot" implies that there is one real pilot and a half pilot, when the reality is an airliner needs at least two fully qualified pilots to fly it safely!

When it comes to actually flying the plane, the two pilots have designated roles - Pilot Flying (PF) and Pilot Monitoring (PM - sometimes this is called Pilot Not Flying). Both the Captain and the First Officer share these roles - usually one of them is PF on the outbound leg and the other one is PM on the inbound leg. The PF manipulates the controls to actually fly the plane, whereas the PM handles communications and other required tasks that don't involve actually flying the plane.

The biggest difference between a Captain and a First officer is responsibility. The Captain is the Pilot In Command (PIC), who has ultimate responsibility for everything that happens throughout the flight. There are some practical things that only Captains can do, like flying into some tricky airports, landing in strong crosswinds, and on many aircraft only the Captain can use the steering wheel (or Tiller) for taxiing.

Historically there was a strong heirarchy - the Captain was the boss and the co-pilot was, you could say, a servant. This posed big problems, because the Captain is not always right. The advent of Crew Resource Management (CRM) has brought this down to a much more desirable level - where there is still a heirarchy to ensure decisions are made, but not so much that they are unquestionable. The future of the First Officer role will be one of continuing to recognise that they play an important role in a functioning cockpit, rather than just there to serve the Captain. And hopefully people will stop calling them co-pilots!


Why do ATC instructions to change level include the words "climb" or "descend"? ATC instructions to change level include the words "climb" or "descend" depending on the direction of the vertical maneuver. For example, "Descend to 2500 feet" or "Climb to FL70".

For comparison, instructions to turn to a specific heading often, but not always, include the words "right" or "left". We can say "Turn right heading 120" or "Turn left heading 360", but in some situations we may simply say "Fly heading 180". When using "Fly heading", it is implied that the turn should made in the direction that requires the smallest change of direction. A pilot heading east instructed to "Fly heading 360" will always perform a left turn, even if the word "left" was not included in the original instruction.

Similarly, for speed control, we have phrases such as "Reduce speed to 220 knots" and "Increase speed to 280 knots", while we can also simply use "Maintain 240 knots", in which case the pilot will then speed up or slow down as appropriate.

Radio phraseology is designed to be as short as possible, and radio calls should include no excessive words. This makes me wonder, why do we always include "Climb" or "Descend" in level instructions? If a flight is at FL320 and we need to instruct it to get up to FL340, it is self-evident that the pilot must climb, not descend. Using this logic, a phrase such as "Maintain FL340" or even just "FL340" (Example: "[callsign], FL340") should suffice.

I can think of reasons who we do use climb and descend. It most likely improves situational awareness for both controllers and pilots (including other flights on the frequency). It could also enable pilots to identify situations where they mishear a level instruction (Example: for a flight on FL320, instructed to "Maintain FL240", the crew might mishear this and think they are cleared to FL340. If the phrase "Descend to FL240" is used, this is less likely to happen). Finally, "Climb to" and "Descend to" is not much longer than "Maintain".

However, this leaves the question of why we have such "neutral" phrases for heading and speed restrictions. Wouldn't enforcing the use of "Right", "Left", "Increase" and "Reduce" introduce the same benefits we get from using "Climb" and "Descend"?

Is there a historical reason the phraseology concerning level changes is designed the way it is - perhaps an incident or accident where another phraseology was used? Or is it a coincidence that level instructions are different compared to heading or speed restrictions?

I can come up with "qualified guesses" myself, so I am hoping someone with actual knowledge on the topic can provide a factual answer.

Adding the instruction "climb/descend" to the flight level is an example of linguistic redundancy offering a very rudimentary form of error detection for voice communication (which is inherently "unreliable", as it can be misheard by the receiver – on top of the sometimes poor ATC radio channel quality):

  In […] telecommunication, error detection [is a] technique that
  enables reliable delivery of […] data over unreliable communication
  channels. Many communication channels are subject to channel noise,
  and thus errors may be introduced during transmission from the source
  to a receiver. Error detection techniques allow detecting such errors.
  (source)

Therefore adding the instruction "climb/descend" offers an additional layer of security, because

the pilot would never descend when instructed to climb (and vice versa)
and the pilot is able to detect an instruction mismatching the flight level, i.e. "climb to FL240" when already at FL320 (taking the example in your question)

... but not perfect security (because the pilot at FL320 would not detect an error if ATC mistakenly instructs him to "climb to FL420" instead of "climb do FL400"). Therefore ATC instructions are repeated on the receiving end by the pilot.

(For a non-aviation analogy, the same technique is applied when dates are agreed upon on the phone as "Friday, 4 January 2019", although the day of the week is already implied by the date itself.)

In essence, your question "Why do ATC instructions to change level include the words 'climb' or 'descend'?" can be best answered by the (limited) added information transmission security these instructions provide. Therefore for me the real question is why instructions concerning speed and heading don't obligatorily require this sort of disambiguating instruction – especially so as this unspecificity can demonstrably lead to confusion. I hope someone else will be able to answer this part of your question, as I don't have specific knowledge about this aspect of it.


What is the rescue arrow decal on a military jet pointing to? I've noticed that a lot of military jets often have an arrow decal with the wording "RESCUE" pointing to a rectangle of some sort. I tried looking around for information about it but I could not find anything. What is the purpose of that rectangle the arrow points to?

The other decals seem to be much clearer: e.g. the red triangles are usually ejection seat warning labels and jet intake danger labels.

My own guess is that it is a button/switch device to trigger explosive bolts on the canopy or another mechanism. If so, what does it look like and how does it function? A close-up and a detailed example would be useful.

It's a small door leading to a compartment which contains a handle on a reeled lanyard.  When fully extended, the handle and lanyard activate the pyrotechnic charges which jettison the canopy or other enclosure over the flight crew stations, facilitating rescue.

The arrow may also just point towards the external canopy latch in order to expedite cockpit access and rescue.


Why aren't 3-surface aircraft more popular in general aviation? From everything I can gather, canards offer significant gains in performance characteristics, and most the drawbacks apply only if you remove the tail. Why not mix them together? What does Piaggio know that we don't?

Canards are not used in general aviation simply because they have complexe interaction with the main wing which can leeds to issues with stability and being at the front of the CG their effect on flight dynamics may be highly unintuitive in some situations. Therefore you need electronic control to adapt the pilot input to the control surface in order for the plane to fly as expected, and that's why in my opinion it was not suited to GA where electronic was expensive until the past few years. But they are plenty of jet fighter using them as they have the ability to greatly increase performance and maneuvrability.
In addition 3 surface aircraft means more wetted aera thus more drag, complex design and control, more mechanical moving parts which will often drive the price up.
You can find more information looking at the patent issued in 1988 by Piaggio here : https://worldwide.espacenet.com/publicationDetails/description?CC=US&NR=4746081A&KC=A&FT=D&ND=&date=19880524&DB=&locale=en_EP


What would happen if a pilot were to use the parking brakes after touchdown in order to slow down? The situation that I came up with is merely hypothetical. Say a pilot was unable to land right after the runway threshold, for whatever reason it may be - a crosswind, etc - but was determined to land the aircraft.

I understand that most pilots would abort the landing and go around but say this one decides to land. However, it is too close to the end of the runway to stop just by using brakes, spoilers, and the thrust reversers. Could this type of landing (in an emergency) be achieved and by using the parking brakes what would happen if a pilot actually used the parking brakes to slow down?

This question appears to have an implicit assumption: that the parking brake would provide more deceleration than is available from normal braking. This is not generally the case.

A much greater worry for pilots than insufficient braking is actually excessive braking - to the point that the wheel locks up and skids. A skidding tire provides much less braking than a rolling one, and also quickly acquires a flat spot. Even on dry pavement, maximum braking would require an anti-skid system to remain effective; consider a 757 and a Mig-29, each of which blew out their tires when their anti-skid systems failed.

Note also that in small planes without complex braking systems, the parking brake merely maintains the pressure that is in the brake lines at the time it's applied. The parking brake would have no effect if the pilot were not already on the brakes, and would not be able to add any additional braking than the pilot could otherwise apply.


Why is the takeoff decision point based only on speed and not time or distance? The go/no go decision on takeoff for airliners is calculated as a V1 speed. The question is, why is there no time or distance for V1 calculated. In other words, if we don't reach V1 in X seconds or by X point on the runway the takeoff is rejected.

An example of where this might have prevented disaster is Air Florida Flight 90. The engine inlet probes were frozen, resulting in an inaccurate EPR reading. This caused them to set thrust much lower than they should have. They reached V1 and VR but with degraded lift, due to icing, they were not able to climb over the bridge. The FO felt something was wrong, but the captain told him it was fine and called V1.

The chain of events leading to this accident was very long and full of bad decisions. But had there been a hard and fast rule that if V1 has not been reached by this point then reject takeoff, the chain could have been broken.

Another example of where degraded performance resulted in too long of a takeoff roll is the Lokomotiv YAK-42 crash, although it doesn't appear they even had a V1 speed calculated either. They weren't accelerating fast enough, but the captain carried on expecting it to lift off at any moment. They went right off the end of the runway before it did. The reduced acceleration was obviously not enough to make the captain reject right away and by the time it did become obvious he was out of options.

There may be an unknown number of runway excursions where there was degraded performance and the crew did reject takeoff, but too late to stop.

If an engine has a problem it may continue to function in a reduced capacity then finally failing after V1. The procedures call for continued takeoff after that point, but they may have used up too much runway already.

There are myriad things that can cause degraded performance on a takeoff roll. Anything from tires, brakes, engines to flap configuration, even runway condition can slow you down and it may not be obvious that it's occurring. Many of these things won't show up on an instrument scan or a checklist. It just seems like there's no specific guidance as to how long you wait for V1. How does a pilot know when it's time to call it off?

Manually checking:

My guess from a human factors perspective, focusing on 2+ things (e.g., speed and time) is harder than one.

Newer aircraft have installed automatic monitoring though. For example for the 787:

This message is inhibited 6 knots before V1.

Or the similar system (supposedly) on the A350. Airbus calls it ACUTE:

  The Airbus Cockpit Universal Thrust Emulator
  (ACUTE) converts the engine control parameter into a
  common Thrust parameter (THR) for all engine types.
  The thrust parameter varies between 0% and 100% in
  all flight conditions.

This would understand a faulty/blocked EPR probe for example.

For inadvertently holding down the brakes (extremely rare occurrence), the brake temp should rise considerably. And with today's glass cockpits, a warning will be easy to spot.

Automatic accurate monitoring of acceleration:

A warning system built to use the accelerometers on board will need to measure the acceleration against flight test data. But not just acceleration, a plane's acceleration on takeoff varies, due to increasing drag and decreasing friction (landing gear decompression).

See this PDF, and this post: Does acceleration increase linearly on a takeoff roll?

An average positive runway slope value used in real life can be down to a runway sloping down, then sloping up at the end of the runway. Some dispatchers note that, others do not need to. But this false value can trip the system.

My point is the variables are immense—even nose heavy acceleration will be different—and would require lots of money to test, verify, test again, then have a system that can monitor all that. I'll bet there will be many false positives.

Add to that when to start measuring it, a pilot pushing TO/GA at 10 knots (ground speed) versus 40. IAS is useless here due to wind.

If the system will allow for big tolerances, then properly trained pilots can notice it much easier. To borrow what Carlo said here, using TLAR (That Looks About Right) is enough.

Let's not forget that there is a speed trend arrow on the airspeed indicator on most of today's airliners:

Green arrow shows what the speed will be in 10 seconds on a Boeing 787.

Coming soon:

For the generic very slow acceleration (as far as I can tell), Honeywell is developing that system as part of their SmartRunway package. (Thanks to fooot for mentioning that.)

  He advanced the throttle to a setting too low for the weight of the aircraft and started the takeoff roll, with distance remaining ticking down on the display. At 80 knots, a yellow box framed the runway and “ACCEL LOW” appeared at the top of the screen. “Caution: acceleration, acceleration,” said a female voice from the simulator setup.

Regarding the method used by the USAF (explained here): it does not work for the big civilian airliners due to the disparity between an empty plane and a fully loaded one (compounded by the environmental variables). A 777-300ER can carry anywhere between say 20 tonnes (fuel for a short hop), and 183 tonnes (payload and fuel).


What do the different dates in a TCDS mean? I have been trying to interpret Type Certificate Data Sheets and am coming up short on how to understand some of the dates listed. For example, here is the TCDS for the new Citation Longitude:

How is one to interpret these dates? Did the type certificate get issued in 2020 or 2019? The Textron Aviation website has a news release in September that claims certification occurred in 2019; so is the 2020 date specific to the TCDS being released, even though FAA approval occurred in 2019?
Also, how does this related to the Revision numbers? Does the 2020 date refer to Revision 4 and the 2019 date refer to a different revision? I can't seem to find the earlier revisions on the FAA website either, so I am not sure whether they even exist as official/released FAA documents.

The Type Certificate document is just a kind of diploma so to speak, or, as it says in its name, a Certificate.  The real meat is in the TCDS, which describes the technical details, limitations etc., of the aircraft that are the basis of its Type Certificate and which set out the parameters that must be met to be in compliance.
When these details change or need to be corrected, they don't reissue the Type Certificate, they just revise and reissue the data sheet that is linked to the TC by its number, T00015W1.
In your example, Feb 5 is the date of issue of the revised Data Sheet at Rev 4, so there would be three other revisions, plus the original issue (which should have the same date as the TC itself), prior (Page 6 is still at Rev 3, and Rev 4 is Page 1-5, and revision bars show what was changed in Rev 4 on those pages).  That's why it's in the document identification block at the top right.  It's the issue date of that Data Sheet revision.
The TC approval date is just a reference to the original TC issue in Sept 2019, which doesn't normally change, being the fancy sheet of paper you frame and stick on the wall when you're the engineering VP who led the program.


Getting data from Existing ADSB Receivers Is there any way to get data from existing ADSB receivers installed around the world?

ADSB Exchange and OpenSky Network both provide access to the data they receive from their contributors.  Terms (and payment) may vary depending on whether your use is research or commercial.


If Floyd Bennett Field failed due to its remoteness and isolation, how has JFK been so successful? Floyd Bennett Field was built at the end of the 1920s in order to give New York City its own airport and avoid having to rely on Newark; however, despite its superb airport facilities, Floyd Bennett Field was never a commercial success, being cursed by the relative remoteness and isolation (compared to Newark) of its location in far southeastern Brooklyn.  As a result, when the airlines and the airmail stayed at Newark, LaGuardia Airport was built in northern Queens, quickly becoming much more successful than Floyd Bennett ever was, and remaining New York’s primary airport until 1948, when Idlewild Airport (JFK from 1963) opened in far southeastern Queens.  Idlewild/JFK, in turn, quickly came to overshadow both LaGuardia and Newark, and has been the primary airport of the New York metropolis ever since.

But JFK is even more remote than Floyd Bennett!

If remoteness killed Floyd Bennett, why hasn’t it killed JFK?

If remoteness killed Floyd Bennett, why hasn’t it killed JFK?

Because remoteness did not kill Bennett.

The opening of LaGuardia airport in 1939 absorbed all the traffic, then in 1941 the Navy took over Bennett and banned all commercial and GA flights. After WWII it was meant to return to commercial service to handle the excess traffic from LaGuardia.

(Idlewild was still being built – bigger land area, longer-runways potential, hints of the jet-age in the air, etc.)

But the Port Authority and the Navy could not agree on the cost of moving the Navy's facilities.

  The controversy between the Port Authority and the Navy that has kept commercial traffic out of Floyd Bennett Field in Brooklyn narrowed down yesterday to a \$450,000 question of price. The Navy is asking \$1,200,000 to transfer its facilities and the Port Authority is standing by its statement that it could not spend more than \$750,000 for that purpose. (nytimes.com, 1947)

Further reading: https://en.wikipedia.org/wiki/Floyd_Bennett_Field#History


Why don't air-cooled radial engines use fuel to cool the oil? Having read up on WWII air-cooled radials, one thing that struck me is how frequent is the mentioning of external oil cooler overheating, or the need for armored boxes around it, and some even venture to say the so-called air-cooled radials are in reality oil-cooled radials.

This got me thinking. Since the oil in turbofans is cooled by fuel flow, why isn't this the case for radials? Is this because the fuel flow is insufficient, or the oil too thick, or some other reasons?

The Fuel/Oil heat exchanger serves two purposes. It helps to dissipate some of the heat from the oil and warm the fuel up for combustion

  The fuel-cooled oil cooler acts as a fuel oil heat exchanger in that
  the fuel cools the hot oil and the oil heats the fuel for combustion.
  Fuel flowing to the engine must pass through the heat exchanger;
  however, there is a thermostatic valve that controls the oil flow, and
  the oil may bypass the cooler if no cooling is needed.

In piston radials you generally dont need this fuel pre-heat. Since Avgas is vaporous at a fairly low temperature you dont really need to pre heat it. On top of that preheating it may vaporize it in the lines which is also a fairly big issue in and of itself.

There are always concerns of cross leaking, and this applies in both cases. A leaky exchanger can add fuel to your oil or oil to your fuel. A potential issue in either direction.


What happens when an airplane stalls and why do pilots practice it? When a non-pilot hears the word stall, it brings to mind what happens when a car stalls -  the engine quits. It seems like that would be a dangerous scenario in an airplane.

From a non-pilot perspective, what happens when an airplane stalls and why is it important for pilots to practice it?

Stall was an unfortunate choice of words for an engine that suddenly quits since the aerodynamic stall in aviation means something very different and isn't related to the aircraft engine at all1.

To a non-pilot, an aerodynamic stall can best be described as the situation where there is not enough air flowing over the wings to create the amount of lift needed to hold up the airplane.

The main reason that student pilots practice stalls is to learn the telltale signs that occur just before it happens and to make the recovery procedure automatic.  If pilots can recognize an impending stall, they can take corrective action to either avoid the stall altogether or to recover as quickly as possible.

Outside of training, inadvertent stalls typically only occur shortly before landing and after takeoff, when the pilot gets distracted while already at a slow speed.  In both of these situations the airplane is very close to the ground, immediately requiring the correct action from the pilot in order to avoid a crash.  This needs to be instinctive and corrected using muscle memory so that it is accomplished as rapidly as possible.

The next logical question is usually:  How does a pilot fix an airplane that has stalled?

Fortunately, airplanes are designed so that even during a stall the tail is still effective2 and the pilot is able to use it to force the nose down.  This makes the airplane go faster, since it is pointed down towards the ground, and gets more air moving over the wing which allows it to create enough lift for the airplane to start flying again.  During practice it is usually pretty uneventful, but when it happens at a low altitude there may not be enough time to regain flying speed before the airplane crashes.

For more information, AOPA has a great Safety Publication targeting flight instructors called Why we teach slow flight and stalls which is available on their website.

1 However, the sail on a sailboat can also "stall" when there isn't enough wind and since they have been around since 3,000 BC I guess that technically this usage of the word applies to both situations.

2 There are some stalls in particular airplane designs known as deep stalls that can be unrecoverable.  I don't think that this is important when describing it to a layperson though.


Why are there GPS MOCAs? The Pilot Controller Glossary (and other places) define MOCAs as:

  MINIMUM OBSTRUCTION CLEARANCE ALTITUDE (MOCA)− The lowest published
  altitude in effect between radio fixes on VOR airways, off-airway
  routes, or route segments which meets obstacle clearance requirements
  for the entire route segment and which assures acceptable navigational
  signal coverage only within 25 statute (22 nautical) miles of a VOR.

VORs aren’t used in GPS navigation so I don’t understand why there would be a GPS MOCA on a T-Route or Victor Airway.

Even the example given in the Aeronautical Chart Users Guide (p56) has a GPS MOCA below the MEA.

Here’s a segment of a Victor Airway in Florida with a MOCA of 1300 but the MEA for GPS is 3000.

I would think the GPS MEA would be the MOCA or even lower, since VOR reception isn’t required in the first 22 miles. If you fly at the MEA it guarantees that a normal climb will keep you above obstacles when entering the next segment with a higher MEA. But I would think that the MOCA would do the same thing unless there was an MCA. So that doesn’t seem to be a reason.

There are even T-Routes in Florida with a GPS altitude and a lower GPS MOCA. That makes even less sense to me.

Does the GPS MOCA also take into account communication reception—but in that case why isn’t that mentioned in the regular MOCA definition?

If anyone could shed some light on how they come up the GPS MOCAs it would be appreciated.

MOCAs provide minimum obstacle clearance, as you note; MEAs also provide this—and more.

MOCAs are determined essentially the same across the board. The question that I think you should ask is why is the MEA higher than the MOCA in some cases where you might not expect it, namely in the case of some GNSS MEAs.

Firstly, all MEAs take into account multiple factors, including those described in the following. Note the mention of airspace buffers and communications requirements.

From the FAA's Instrument Procedures Handbook, on p. 2-35:

  The MEA is the lowest published altitude between radio
  fixes that assures acceptable navigational signal coverage
  and meets obstacle clearance requirements between those
  fixes. The MEA prescribed for a Federal airway or segment,
  RNAV low or high route, or other direct route applies to the
  entire width of the airway, segment, or route between the
  radio fixes defining the airway, segment, or route. MEAs
  for routes wholly contained within controlled airspace
  normally provide a buffer above the floor of controlled
  airspace consisting of at least 300 feet within transition
  areas and 500 feet within control areas. MEAs are established
  based upon obstacle clearance over terrain and manmade
  objects, adequacy of navigation facility performance, and
  communications requirements.

Earlier, on p. 2-16, the requirement for communications reception in the case of GNSS MEAs (at least those on RNAV T-routes) is explicitly stated. This makes sense given that these two factors are the primary factors needed in flight guided by GNSS.

  A GNSS MEA for each segment is established to ensure obstacle
  clearance and communications reception.

I'm not sure that this answers your stated questions, but I do think it should ultimately answer what you are wondering.


Strut braced or wire braced airplane wings? For an ultralight (or other airplane designed for slow flight), would a strut-braced or wire-braced wing be more efficient aerodynamically?

Depends on the shape.  A round 1/8" wire would have way less drag than, say, a 1" round lift strut, obviously.  And the same for a streamlined wire vs a streamlined lift strut. So looked at that way, the wires win aerodynamically even with 4 wires per wing vs 2 struts.

However, streamlined wires are crazy expensive and have to be custom made, so they aren't really a practical option and you are stuck with round cable, whereas a streamlined strut is not so hard to do.

So the practical comparison is round wire vs streamline strut.  A teardrop shape has 1/12th the drag of a round shape, so a round shape of 1/8" diameter has the same drag as a 1.5" thick teardrop shape.

In view of that, a streamlined lift strut of say, 1" thickness (frontal area) would still have less drag than a 1/8" cable of the same length, and you only have 2 per wing vs 4 cables per wing, so overall you are ahead with streamlined struts.  Add the benefits of rigidity, ease of assembly, looks, etc, and streamlined lift struts are a no brainer, which is why 99.9% of non-cantilever monoplanes use struts (wire bracing may be somewhat lighter however - or maybe not).

Now, a streamlined aluminum extrusion for an ultralight might also be somewhat expensive to source, though nowhere near as bad as streamlined cables.  So for an ultralight, unless teardrop extrusion is available cheap, the most efficient all round choice would be to design a lift strut made from round aluminum tubing and apply over that a light fairing of .016" aluminum, or formable plastic, or fiberglass, or whatever, to get the teardrop shape.


What’s service does ATC service include? As I’ve studied on ATC service and airspace class by referring to ICAO Annex, I have some doubts on ATC service.

According to ICAO Annex 11, Class D airspace is defined as “IFR and VFR flights are permitted and all flights are provided with air traffic control service, IFR flights are separated from other IFR flights and receive traffic information in respect of VFR flights, VFR flights receive traffic information in respect of all other flights.”

When referring to other definition such as ATS service, It is divided into ATC service, flight information service and alerting service. And I think separation and traffic information service are included to ATC service of ATS service.

So, when I read the definition of Class D airspace that IFR and VFR aircraft are provided with ATC service, I think separation and traffic information service are also provided because these are the ATC service. However, as you guys know, although ATC service is provided to all VFR and IFR in controlled airspace, separation and traffic information are selectively applied depending on airspace class.

To sum up, I want to know what ATC service includes and whether traffic information and separation are one of ATC service or not.

Air traffic control service is a service provided for the purpose of:

  preventing collisions:

  between aircraft, and
  on the manoeuvring area between aircraft and obstructions; and

  expediting and maintaining an orderly flow of air traffic.

  (ICAO Annex 11)

When saying a flight is provided with ATC service, it is just another way of saying that it is a controlled flight. That is, a flight where the pilot can't just do what they want, because the flight is subject to an ATC clearance; the ATCO will clear the flight to follow a certain route and fly at a certain level.

Importantly, all controlled flights are coordinated as long as they remain in controlled airspace. This ensures alerting service throughout the controlled portion of the flight. This coordination also extends to military units (so we don't have a repeat of Korean Air 007). Controlled flights are also provided with flight information service (traffic info, weather info, info on nav-aids etc.)

As stated in the quote above, ATC service is provided for the purpose of preventing collisions. However, actual separation is not necessarily guaranteed to be provided by the ATCO. The class D airspace you mention is a great example. Separation is only guaranteed to be provided by ATC for IFR-IFR conflicts. In other cases, it is ultimately the responsibility of the pilot* to prevent collisions, which they are able to do based on the flight information service provided.

*: the controller can still decide to provide separation, but is not required to do so.

Note that separation on the manoeuvring area (which includes the runway) is provided regardless of airspace class.


How does an airplane move itself in the runway? Basically do they move themselves using their powerful jet/propeller engines to propel themselves forward or do they just use an engine that powers the wheels used for landing?

I'm not really asking about planes that are readying for takeoffs just the ones that move on the ground like a car would.

The power to move an aircraft from point A to point B on an airport is provided by the same engines that power it in flight unless you hook up a tug, in which case the tug provides the power. There have been experimental developments that provide power to the main landing gear wheels, but there have never been any real implementations of these systems. Small single-engine aircraft can be moved by hand.


As a student pilot can I fly solo hours from any airport? I am researching flight school because I am very interested in getting my PPL. I live in DFW I just graduated from college and money is tight. So I am saving money to get the PPL. I know the bulk of the cost is paying someone to train me. My question in regarding the privileges you have as a student pilot.

No, the airports you can fly from/to must be specifically endorsed by your instructor. Once you have your PPL, you can fly to any airport.


Landing currency day and night on same ride? Assume you know when sunset was on a particular day you decided to fly (e.g. 8:30 local time). If you took off at 8pm, repeated 3+ landings in the pattern, then left the pattern for about half an hour, returned into the pattern at home airfield, did 3+ more landings to full stop at night...did you achieve the objective of landing currency for both day and night, and if so how do you normally log the landings?

As pilots we often talk about night flying and daytime flying meaning when it is dark or light, but for logging time and for currency in the US there are specific definitions that we must pay attention to.

  FAR 1.1 General Definitions

  Night means the time between the end of evening civil twilight and the
  beginning of morning civil twilight, as published by the American Air
  Almanac, converted to local time.

Day is not defined in the FARs but the definition of night implies that it is the time between the beginning of morning civil twilight and the end of evening civil twilight.

The Air Almanac is published annually on CD-ROM but you can find sunset, sunrise, and civil twilight times for specific locations at the US Naval Observatory website or in ForeFlight.

The time between sunrise/sunset and twilight is 26-30 minutes depending on the time of year. Since you can easily find sunrise/sunset information in newspapers, the weather channel, etc. you can estimate twilight fairly easily.

Currency

  §61.57 (b) (1) … no person may act as pilot in command of an aircraft
  carrying passengers during the period beginning 1 hour after sunset
  and ending 1 hour before sunrise, unless within the preceding 90 days
  that person has made at least three takeoffs and three landings to a
  full stop during the period beginning 1 hour after sunset and ending 1
  hour before sunrise, and…

VFR Weather Minimums
Only Class G airspace has different minimums depending on night and day and they use the standard night definition—end of evening twilight to the beginning of morning twilight.

Aircraft Lights
Aircraft lighting is required between sunset and sunrise.

  §91.209 During the period between sunset and sunrise no person may 1.
  operate an aircraft unless it has lighted position lights, 2. park or
  move an aircraft in an area of an airport where night operations are
  being conducted unless it is clearly illuminated, has position lights,
  or is in an area marked by obstruction lights.

Aeronautical Experience Requirement
In order to obtain a private pilot certificate night training is required. The commercial pilot certificate required solo night flights. In these cases the standard night definition—end of evening twilight to the beginning of morning twilight—applies.

Special VFR
AIM 4-4-6 g. Special VFR operations are prohibited between sunset and sunrise unless the pilot is instrument rated and the aircraft equipped for IFR flight.

Logging Night Flying Time
Logging of night flight should be made in accordance with Part 1 definitions, which is from the end of evening civil twilight to the start of morning civil twilight. This differs from the definition used for night currency.

Summary

• Position lights – sunset to sunrise

• Special VFR – except sunset to sunrise unless instrument rated

• Carry Passengers – 1 hour after sunset to 1 hour before sunrise

• Everything else – evening twilight to morning twilight

The answer to your question.

Now that we have that out of the way, we can look at the requirements for carrying passengers.

  §61.57   Recent flight experience: Pilot in command. (a) General
  experience. (1) Except as provided in paragraph (e) of this section,
  no person may act as a pilot in command of an aircraft carrying
  passengers or of an aircraft certificated for more than one pilot
  flight crewmember unless that person has made at least three takeoffs
  and three landings within the preceding 90 days, and—

  (i) The person acted as the sole manipulator of the flight controls;
  and

  (ii) The required takeoffs and landings were performed in an aircraft
  of the same category, class, and type (if a type rating is required),
  and, if the aircraft to be flown is an airplane with a tailwheel, the
  takeoffs and landings must have been made to a full stop in an
  airplane with a tailwheel.

  (2) For the purpose of meeting the requirements of paragraph (a)(1) of
  this section, a person may act as a pilot in command of an aircraft
  under day VFR or day IFR, provided no persons or property are carried
  on board the aircraft, other than those necessary for the conduct of
  the flight.

You can remain current for carrying passengers in the daytime by making three takeofffs and landins either with or without passengers. If you are not current, you may regain currency as long as you don’t have passengers.

A separate regulation governs night currency—where night is 1 hour after sunset until 1 hour before sunrise.

  §61.57   Recent flight experience: Pilot in command.** b) Night
  takeoff and landing experience. (1) Except as provided in paragraph
  (e) of this section, no person may act as pilot in command of an
  aircraft carrying passengers during the period beginning 1 hour after
  sunset and ending 1 hour before sunrise, unless within the preceding
  90 days that person has made at least three takeoffs and three
  landings to a full stop during the period beginning 1 hour after
  sunset and ending 1 hour before sunrise, and—

If you are night current then you have satisfied §61.57 (1) and so you are also day current.


Does aeronautical experience ever expire? Do the hours of flying with instructor or solo ever expire? I have my 50 (yes, 50) year old pilot's Flight Log with CFI entries for 20 hours dual and 1 solo. Do I have to start over, or would some of them count for PPL license?

As far as the FAA is concerned, they do not expire.

As far as any (reputable) flight school goes, they will probably require a full, recent minimum 40 hours of training before they sign you off for the practical exam.

The good news is that your old training, no matter how rusty, probably means you'll pick up the basics quite quickly, and probably solo (again) faster than the average, and may very well be ready for your checkride close to 40 hours.  (The national average is a checkride around 50 to 60 hours.)


What Electronic Flight Display is this? I just watched this video in which the avionics surprised me. It looks like a half Garmin G600, attached on his yoke.

What is that and is it permanently attached to the yoke or is it portable?
Could it be for aircraft that can not be retrofitted? Because there is also something to see what looks like a ADS-B-receiver to me:

At first this reminded me of the Garmin G3X. However, it is mounted on the yoke and must be a GPSMAP 695 or 696

https://buy.garmin.com/en-US/US/p/14860


How much fuel does an A380 hold and where? How much fuel does an A380 usually carry (in litres) and what is the maximum? How much is in each wing? How much is in other fuel tanks and where are they?

The total capacity of fuel tanks of Airbus A380 is 320000 liters.

The fuel tanks in Airbus A380 are shown in this image.

Image Source

The capacities of different tanks are1 (in liters):

Tail tank: 23,698
Inner tanks: 90,600
Mid tanks: 72,000
Feed tank 2 and 3: 28,130 each
Feed tank 1 and 4: 26,974 each
Outer tanks: 9,524 each

1 The only place I found this information is in the book Airbus A380: Superjumbo of the 21st Century. Luckily, it is on Google books. This excerpt from the book about the relevant information says:

  The horizontal stabilizer runs through section 19 and includes an integral fuel tank between ribs 8 left and right. The fuel level in the tail tank, which can take up to 23,698 liters, is adjustable in flight for trimming purposes. Overall, the hard-line A380-800 fuel-tank capacity is 315,292 liters, most of which is contained in two inner tanks with more than 90,600 liters. Two other mid-tanks hold about 72,000 liters between them, with inner engine 2 and 3 feed tanks containing 28,130 liters each. The outer engine 1 and 4 feed tanks each hold 26,974 liters, while the two outer tanks each hold 9,524 liters.


Why were the speed records set by seaplanes in the early thirties? For nearly all of the 1930'ies, the fastest aeroplanes were all of the seaplane category (as opposed to landplanes, to use the terminology of FAI).

Presumably, the designers of the two categories had access to more or less the same technology (engines, materials, aerodynamics, etc.) given the large interest in the subject and funding available.

If we for a second rely on Wikipedia for the record listing, we see that the speed record for a seaplane set in 1931 is 655.8 km/h (Supermarine S.6B), while the record for a landplane set in 1935 (4 years later) is "only" 567.1 km/h (Hughes H-1 Racer).

Seeing how fast aviation technology developed in that period, it is remarkable that four years after the Supermarine record, the fastest landplane was still significantly slower than the fastest seaplane.

I would expect the large pontoons on the seaplanes to provide more drag compared to a simple landing gear, and hence by logic the seaplane should be penalised and achieve lower maximum speeds. All things being equal.

However, since the speed differences are so pronounced, all things obviously are not equal. So what are the differences between the two categories (or their designers and manufacturers) that can explain the gap in maximum speed?

The answer: Fixed-pitch propellers.

Until the 1930s propellers were fixed pitch only. From Wikipedia:

  The first practical controllable-pitch propeller for aircraft was
  introduced in 1932. French firm Ratier pioneered variable-pitch
  propellers of various designs from 1928 onwards, relying on a special
  ball bearing helicoïdal ramp at the root of the blades for easy
  operation.

This means all speed records were flown with fixed-pitch propellers, which needed to be optimised to the top design speed to coax as much thrust from the engines as possible. In turn, this means that most of the propeller blade was stalled at low speed, so take-off thrust was low. To achieve high speed, a high wing loading was needed and, in combination with low thrust, the take-off length of such an aircraft was beyond of the length of airfields back then.

On water, however, the maximum field length is close to infinity. Yes, drag with floats is especially high when transitioning from buoyancy to dynamic lift (the "hump"), but that can be overcome when that hump occurs at high enough speed so the propeller delivers enough thrust.


Is there a specific procedure for grounding a pilot? When a pilot gets grounded by the FAA, is there a specific procedure that happens?

I have heard of situations where the pilot is recommended or told to ground themselves. Is this the same as if the FAA were to do it or does the pilot just say "I'm not going to fly today"?

It depends on how/why you are grounded and who does the grounding.

The FAA can legally ground you if your license gets suspended (or in rare cases completely revoked) there are formal proceedings the FAA has in place. You can find the AC that covers it here.

AME's can can deny you a medical certificate which can prevent you from flying. In this case you are also legally grounded as you may no longer comply with FAA regulations.

AME's may also make grounding recommendations. Say you start taking a new medication that is legal on the FAA's list. The general advisory is to "see how the medication effects you" prior to getting back to flying. Often this is subjective and there is not really any hard guidance on time limits for every medication. These groundings should be self imposed by the pilot.

You can be practically grounded by say a flight school or insurance company. This falls more into the "not fit to fly" category. Technically you are legal to fly but other practical limitations may prevent you from flying. Lets say you show up to rent a plane and you are clearly sick. You say you "feel fine" but the flight school is under no obligation to rent to you and may chose not to if they feel you are not fit to fly.

Every pilot is responsible for a self assessment prior to making any flight to ensure they are fit to fly. Ultimately an infraction could fall under 91.13 Careless or Reckless Operation. In this case you may or may not be legal to fly but its up to you to make that self assessment and not fly.


Why autogyros use pusher-, whereas, piston-engined planes use puller-configuration? I found that most modern gyrocopters use a pusher-configuration, whereas, most piston-engined planes use puller-configuration.

Since the pusher-configuration has major disadvantages, are there specific advantages for autogyros?

Visibility is a positive effect of pushers, but this would also count for normal planes.

Pitcairn PCA-2 - By NASA/NACA, LARC [Public domain], via Wikimedia Commons

The original autogyros were tractor (google Cierva/Pitcairn).

The big thing with autogyros is thrust line relative to the vertical C.G.   The pusher craze was started by Igor Bensen with his homebuilt autogyro, which was done that way to keep everything compact and minimalist, and give the pilot a nice view.  The issue with Benson machines and variants is the thrust line is above the center of mass, and if you unload the rotor disc by doing a bunt, or hit major turbulence that makes you go zero G, they have a tendency to pitch over and tumble as the prop wants to spin the machine about its vertical CG in the absence of any resisting force.  It's called Power Push Over or PPO and is always fatal.  You must NEVER go zero G in a Benson or any machine with a high thrust line.  It's actually quite similar to the mast bumping problem with teetering rotor helicopters, although that happens on the roll axis.

A lot of gyros move the engine down as much as possible to lower the trust line to the vertical C.G. or close to it, and have that awkward spindly look as a result because it means making the gear a lot longer.  The other thing that helps is a large horizontal stabilizer to resist large pitching movements and most gyros have them now.

Tractor engine gyros have a better thrust line relationship (generally naturally lower, close to the CG) and also have a long tail with good moment arm and are generally immune to PPO (the fact that the engine is out front or behind is irrelevant in itself).  There are a couple of homebuilt gyros that use the engine out front.  You can tell however that the tractor machines just have way more structure to them so it's easy to see why the pusher setup is so much simpler and lighter.


Why is a urine test performed during pilot medical examinations? I've wondered this for a long time (every six months while getting my latest first class medical), but what are the doctors checking for when they perform the urine test?

Maybe Drugs?  Medical conditions (which ones)?  Both?  Other things?

It's for diabetes and kidney disease. You can read the AME guidance here:

  Item 57. Urine Test
  Glycosuria or proteinuria is cause for deferral of medical
  certificate issuance until additional studies determine the status of
  the endocrine and/or urinary systems. If the glycosuria has been
  determined not to be due to carbohydrate intolerance, the Examiner may
  issue the certificate. Trace or 1+ proteinuria in the absence of a
  history of renal disease is not cause for denial.

Glycosuria is an indication of diabetes, and proteinuria is an indication of kidney disease (among dozens of other things, if Wikipedia is to be believed). And the AME can do other tests too, if he thinks they're necessary:

  The Examiner may request additional urinary tests when they are
  indicated by history or examination.

The regulatory reference (per the AME guide) is 14 CFR 67.113 for a first-class medical, but exactly the same regulation is there for second- and third-class too.


Can excessive G-force break or dislocate bones during pilot maneuvers? Was wondering if the pilot would faint, could g-force be enough to maybe break the neck bone with the head and weight of a helmet being pulled downwards. Another relay to this is the effects on the inside of the body, more specifically, the brain. Like a boxer, after taking a few too many knockouts. Is there a limit, or an event horizon to permanent brain damage and bone structure deterioration concerning g-force and pilots in aircraft maneuvers?

Can excessive G-force break or dislocate bones during pilot maneuvers?

Yes.

Even if the pilot remains conscious.

For example see http://medind.nic.in/iab/t00/i2/iabt00i2p1o.pdf which describes compression fractures suffered by pilots.


What is the size of toilet or septic tanks in various planes? This question, led me to wonder, how big are the tanks that hold poo. I had seen a BBC video, showing how they empty the tank on an A380 at Heathrow, can't remember the capacity.

Also, what about planes like Cessna etc, do they have toilets?

In an emergency can the tank be emptied, in case it overweight, i.e. above the Maximum Landing Weight?

The A380 has a total waste tank capacity of 2096L or 554 US gal, according to Airbus.

  B. Capacity
  There are four waste tanks, two upper deck tanks and two main deck tanks, see FIGURE
  5-4-10-991-003-A.
  (1) Upper Deck Waste-Tanks
  - 373 l (99 US gal).
  Each tank is precharged with 35 l (9 US gal) of chemical fluid.
  (2) Main Deck Waste-Tanks
  - 675 l (178 US gal).
  Each tank is precharged with 35 l (9 US gal) of chemical fluid.
  (3) Total Waste Tank Capacity
  - 2096 l (554 US gal).

The size will vary for each aircraft type, the Boeing 747 had a capacity of only 1000L.

Smaller General Aviation aircraft do not have lavatories, this depends on aircraft size and purpose. The average Cessna will not have lavatories either, pilots have to plan their stops properly or rely on accessory such as the TravelJohn. Larger General Aviation aircraft such as smaller jets and aircraft designed for more than 4 passengers are more likely to have lavatories on board.

(Image Source: Siebert Aero)

There is no dumping system for waste tanks, mostly for hygienic and environmental reasons, as the waste tanks are not only filled with fecal and thus biological matter, but also with chemicals.


When taking passengers, what should I do to prepare them? What kinds of stuff should I think about in terms of taking other passengers flying in a small airplane?  Many potential passengers have never been in a small airplane.

I go through the SAFETY checklist with all my passengers.  The FAA recommends this as well.

Seat Belts - This is where they are and how to use them.
Air Vents - Here are the air vents and how to use them
Fire - In case of a fire here is the location of the fire extinguisher and this is how you use it. PASS method.
Exits, Emergencies and Equipment - Here are the exits on the airplane and here is how to open the door.  Know that you are in good hands and that I have been well trained to land safely under most situations.  If for some reason an emergency occurs in flight follow my directions.  If we need to land off the airport, I will ask you to pop open the door just before landing to ensure we can exit the airplane safely.  Here is any safety equipment that you may want to use on this flight. i.e. supplemental oxygen.
Traffic and talking - Please point out an traffic that you see and I will do the same.  Please no talking while I am on the radio.  Once we start taxiing to the runway please remain quiet til we are far enough away from the airport.  I will let you know when it is safe to talk again.  When we come in to land, I will ask that you remain quiet, unless an emergency situation occurs, till after the landing is complete and we are taxiing back to parking.
Your questions - Do you have any questions?  Alright, lets go have some fun!


What is block hour in ACMI lease? What is difference between Block hour and Flight Hour?

In ACMI Lease of aircraft, prices are calculated based on block hours. What is a block hour and how are they calculated?

Can any one show me an example for a flight like this...

Delay at Runway (takeoff): 20 Minutes
Flight Time: 1 Hour and 40 Minutes

Then what could be block hours? 2 Hours or 1 Hour and 40 Minutes?

Block time starts when the aircraft is pushed back from the gate, and ends when it arrives at the corresponding gate.

It is the total time the aircraft is in use, typically only calculated for revenue movements.

Imagine a flight:

Pushback 1000
Taxi 1030
Takeoff 1035
Touchdown at destination airport 1445
Taxi to gate 1500

Total block time is 5 hours


Does operation under ETOPS rules require additional procedures in flight during the ETOPS segment? During Extended-range Twin-engine Operations (ETOPS), are there any special procedures pilots have to follow? I am asking for specific procedures / tasks during the ETOPS segment of a flight, not what happens before entering the ETOPS segment (check ETOPS items on MEL, calculating Equal Time Points, check communications, ...). Maybe additional checks (engine, fuel, oil) during cruise flight that are not done when not operating under ETOPS rules?

Most of the action for ETOPS flights takes place during planning and dispatch stages- the planning for alternate airports, gathering of weather reports for diversion cases etc. Before ETOPS entry point, the weather reports are updated and checks are made; after that there are no 'special' procedures to be followed during a (normal ETOPS) flight.

From Airbus ETOPS Guide:

  3- IN-FLIGHT ETOPS PROCEDURES

  b) Weather update

  − after ETOPS Entry Point:

  The crew should continue to update the weather forecasts and reports
  for en-route alternates.

  As for a normal flight, the crew must make every effort to keep
  themselves informed on the weather at the destination and the
  destination alternate.

  c) Fuel monitoring

  The procedures normally used as per airline policy is also applicable for
  ETOPS.

  This is true even for flights where ETOPS fuel planning is the limiting factor.

In case of diversion (say due to an engine failure), the PIC will take a decision like any other flight, though he/she cannot fly beyond the nearest suitable airport.

One way of looking at this is that the main purpose of ETOPS certification is to improve the robustness and reliability of the design and operator to a level that the ETOPS flight could be conducted like any other normal flight in the ETOPS segment.


How would I calculate CG in this practice problem? As I'm studying PPL theories, I've encountered with this kind of a question below and it would be great to understand the principle behind the calculation of the 'CG'

Calculated take-off mass = 2300 lbs, calculated CG = 95.75 in, fuel burn = 170 lbs on station 87.00 in.
Where is the CG situated after the landing?

Not too much theory, just simple math.  You find the spot where the sum of all torques
(mass x distance) = zero.  Where you would balance the plane on a see-saw. That is
your CG

If you start out with 2300 lbs at 95.75 inches and remove 170 lbs at 87.00 inches, the torque
of 170 x 8.75 = 1487.5 inch pounds has been removed.  The new weight is 2130 lbs.

The new CG is 1487.5 inch pounds/2130 pounds = 0.70 in the OTHER direction.
So new CG is at 96.45 inches.


What is the current state of research on Autonomous Air Traffic Control? I am trying to get informed about Autonomous Air Traffic Control. Communication is crucial in this field. I am aware that different possibilities exist to realize it, for example:

an ad-hoc network for aircraft-to-aircraft communication
an infrastructure-based communication system

of course infrastructure-based communication systems (meaning a geostationary satellite) include a high propagation delay.

Anyways, I am thinking about a good solution for this problem and am currently looking for research papers in this field. I figured, maybe someone here knows some good sources already?

Do you mean air to air? Or were you thinking of a ground system? What sort of traffic density?

If the former there are a number of concepts within the big medernisation programs like US NextGen, EU SESAR, Australian OneSky or Japan's CARATS programs.

ICAO has a global roadmap running to 2040.

VHF datalink mode 2 is up and running now, higher bandwidth satcom comming (Inmarsat SB-S/ Iris). VOIP likely to have some interesting latency effects in airspaces eith high R/T loads.

Significant global safety spectrum, ITU, regulatory, standardisation and other institutional and political challenges stand before a cool tech idea.

For spectrum look within current band allocations.

Aviation is generally incremental. Bear in mind thst your tech needs to be robust, globally portable.

If you can develop a regulstir accepted method to assure AI or ML apps then this would be a fertlle and lucrative area.


How do I determine which radial intercept angle to use? I'm studying for the (EASA) Instrument Rating exam and I found several questions about radial intercept angles in sample exams but nothing in the books I've studied and my flight instructor doesn't know of any specific rules either.

Based on the answers, it appears that, depending on the current and desired positions and headings, the intercept angle can be 30°, 45°, a third of the heading difference or a combination of a 90° then 45° turns.

What is the rule to determine which intercept angle to use and where is it documented?

  Sample questions:

  current QDM 330, HDG 060, desired QDM 350, what should be the new heading? (answer: 305 for a 45° intercept)
  current QDM 120, HDG 120, desired QDR 060 after flying over VOR, what should be the heading after flying over? (answer: 040 for a 20° intercept angle, a third of the 60° heading difference between 120 and 060)

Note: I've found this document online that mentions the 45° and 90-45 techniques page 20 but it doesn't cover the other cases.
QDM: magnetic bearing to station
QDR: magnetic bearing from station

There is no definite answer to this question.

If you are far away from the beacon radials are far away from each other and thus small intercept angle would be insufficient to reach desired track in feasible time. Also, if you are, say, five miles away from the beacon intercept angle of thirty degrees would be acceptable for C172 but an overkill for transport category jet traveling at 450kts of ground speed. Then again, the mentioned jet would assume the same 30 degree intercept angle to join final track for an approach.

The question has also to do with current aircraft track in relation to the desired track. If you are for example tracking radial 150 inbound towards a beacon and you want to change to radial 180 an intercept angle of 30 degrees would keep you on radial 150 and you will not intercept the desired track until you are overhead the beacon.

The only rule seems to be that when vectoring for approach ATC gives a maximum intercept angle of 30 degrees.


How to measure thrust produced from combustion chamber of Gas Turbine Engine? I'm conduction a scale model experiment of thrust production in combustion chamber by using different types of fuel source.

Comparing the thrust produced by using hydrogen gas, kerosene and petrol.

Specific energy:

Hydrogen gas = 142 MJ/kg

Kerosene = 42.8 MJ/kg

Petrol = 46.4 MJ/kg

What are the instrument to be use for measuring thrust output of the combustion chamber through combustion of the fuels?

What values do we measure? (eg. airspeed at output of combustion chamber/ temperature/ thrust)

Option 1: Thrust is a force, and Force = mass * acceleration, and acceleration is change in velocity.  So you need to measure the mass flow, the velocity upstream and the velocity downstream.  It is probably sufficient to just measure the air mass flow upstream, and measure the fuel flow, and not measure the air mass flow downstream.

Option 2: instead of measuring the air, measure the reaction force.  i.e. at some point, you have to support your combustion chamber.  It will be bolted down to the floor somewhere.  Where ever that is, get a load cell. That is a thing that directly measures force.

But again, with either of these two options, I would expect that your measurement thrust measurement will be pretty close to zero.  A combustion chamber will not generate a large thrust on its own.  You need a nozzle in order to generate a significant amount of thrust.


What would be the best fan duct design to achieve maximum thrust? I have a few brushless motors and I am trying to get the best thrust out of each motor. I am busy doing some research but can't get a clear answer. What would be the best fan duct design to achieve maximum thrust?

Project: mini hover bike prototype with 2 or 3 motors. Duct size doesn't matter at this point.

It's not easy to find research on small ducted fans. I did come across this interesting masters thesis from 2009, which does show some relevant results - at low propeller speeds.

Duct design

The document describes three duct designs, one with a variable bypass inlet and two simpler ones. The simplest one is made from PVC tuning and a foam inlet lip:

Geometric information is given as:

Inner diameter = 14.5"
Duct Chord = 4"
Duct Length (C/D) = 0.28

Maximum Thrust

One of the results of the project is that a ducted propeller delivers more thrust than an un-ducted one. Here is one of the results, listing $C_T$ as a function of tip Mach numbers - which are really low and therefore hard to generalise into practical rotor and fan configurations.

Tip Clearance

Best results were obtained with a propeller with square tips with the smallest gap between propeller and duct that could be achieved. This was a 3-blade propeller, but the research project was severely limited by the small motor used, and therefore low maximum torque that could be exerted on the propellers.


Why is *vertical* autorotation in a helicopter not recommended? Helicopters can autorotate back to earth in case of emergency. The FAA recommends a flight profile similar to the following procedure:

Notice that in section (2) there is forward speed: vertical autorotation is not recommended. Why is that?

When the engine fails in a single engine helicopter it can autorotate back to earth: it gives up potential energy from reducing height to keep the rotor turning, which then continues to provide lift. Autorotation can  take place straight downwards in vertical flight, but the general recommendation is to maintain forward speed, like a fixed wing gliding: the rate of descent is much lower if there is forward speed.

 Image source

We associate helicopters with hovering, but this is a strenuous effort. Even a bit of forward velocity generates translational lift, which makes it much easier for the rotor to generate lift:

The forward inflow tilts the lift vector forward, decreasing induced drag and blade torque, and increasing lift. Or stated in a different way: the airstream is flowing in already, and does not need to be accelerated from zero. The rotor now starts to work more like a fixed wing does.
The airstream through the rotor experiences less interference from the fuselage.

The effect of forward velocity on auto rotational rate of descent is depicted in a graph in this book:

Going back to vertical autorotation: the vertical upward airstream needs to go through the rotor fast enough to reach the windmilling state, so that lift is created by decelerating the air passing through it. If we compute the lift component per area of a vertically autorotating rotor, it is comparable to a $C_D$ value of 1.1 to 1.2 referenced to the rotor area. According to this source:

a flat plate has a $C_D$ of 1.28
a parachute has a $C_D$ of 1.4.

So in vertical descent, the auto-rotating rotor is almost as good as a parachute of the same area - it’s just that the parachute size is a bit small for the typical payload of a helicopter, resulting in vertical descent speeds of between 3,600 to 6,200 ft/min. By way of comparison:

Air France 447 fell to the ground with a vertical descent rate of 10,000 ft/min.
Captain Sullenberger's plane took four minutes to reach the Hudson in a proper glide, from 2,060 ft altitude = average of 500 ft/min.

Two factors make autorotation much more survivable though:

The descent rate can be “flared” by pulling the cyclic back (exchanging forward velocity for more rotor kinetic energy) and then collective up just before ground contact, slowing down the rotor and increasing lift. The pilot only has one shot at this.
The descent rate is a lot less if autorotation is done at a forward speed,   the best one being the optimum climb speed.

Note that in a vertical descend there is no pullback of the cyclic, only increase of collective - plus the rate of descent is higher. A higher speed and fewer means to brake, that is not recommended!

A side note

The windmilling rotor does not turn the other way! The incoming air from underneath tilts the lift vector forward, like in a glider. Part of the rotor disk is driven by the aeroforces into the same direction as it was when still under power.

 Image source


How do small unmanned fixed wing aircraft protect themselves against lightning strikes? I'm asking this question after doing a small research project to see if a small UAS can fly through thunderstorm and trigger lightning strikes. I've googled a bit, and all I've seen are large aircraft getting hardened against strikes.

From what I've read and looked at, all the aircraft use metallic mesh or metal skin to dissipate the heat and voltage. I'm thinking something similar could be done for for a UAS, but don't know how to analyze the system to make sure it can handle the strike.

How does one go about analyzing a structure to see if it can handle lightning strikes? Has anyone flown a fixed wing UAS through a thunderstorm to trigger lightning strikes?

You design your structure, as in larger aircraft, considering where the strike could potentially hit first, and where it would leave.

The rest is electrically bonding everything together, and creating a continuous electrical route from each entry point throughout the structure to the potential exit zones.

Calculating or measuring the electrical resistance throughout the paths is the way to quantify the effectiveness of the design. If it’s zero, the lightning would not hit this aircraft (or would pass through it without causing any harm). However, this conflicts with the scenario of triggering lightning strikes.

To attract lightning, you can simply put a sharp, massive metallic pole, in electrically isolated from the rest of the fuselage.


How are you supposed to get the East/West variation on this question in the FAA PPL written exam? While taking a practice test, I needed to calculate the magnetic heading between two airports. Most of the time I run into a problem, the map will provide me with isogonic lines with the East/West variation visible. But in at least one or more questions, the isogonic line is either not shown, or the numbers are not visible.

Using the protractor to calculate the angle on the isogonic line using the latitude/longitude lines doesn't seem to give me the correct number either.

Does anyone know what I am doing wrong or how I can come to a correct answer?

Problem

(Refer to figure 23.) What is the estimated time en route for a flight from Claxton-Evans County Airport (area 2) to Hampton Varnville Airport (area 1)? The wind is from 290° at 18 knots and the true airspeed is 85 knots. Add 2 minutes for climb-out.

Valid Answers:

44
39
35

Update: I added an actual sample problem. Assuming the only information I am able to work with is the map, the question and my E6B (manual or electronic).

Update
I found the original question that got this thread started:

(Refer to figure 24.) Determine the magnetic heading for a flight from Allendale County Airport (area 1) to Claxton-Evans County Airport (area 2). The wing is from 090° at 16 knots, and the true airspeed is 90 knots.

The correct answer: 209°

The solution given in study mode: With a plotter, measure the true course from Allendale to Claxton-Evans as 212°. Use a flight computer to find the true heading of 203°. Add variation of 6°W. 203°+6°=209°.

Real answer: The FAA screwed up in preparation of that exam question (this sometimes happens; they aren't perfect) and cropped the sectional to where the isogonal lines and or isogonal values are not visible.  As it happens I know that area of the country pretty well.

It works out that Claxton has about a 6.5 deg W magnetic variation (get the full VFR sectionals for that area) and Varnville is just shy of 7deg  W variation; I'd use 6.75 deg W as your number for mag variation over the duration of the flight.  That works out to a course of 051 deg magnetic, 56.5 NM along the route.  With winds at 290 at 18 kts cruising at a true airspeed of 85 kts, this gives an aircraft heading of 041 magnetic in cruise with a ground speed of 93 kts.

Now here's the thing: what is your groundspeed during climb out?  That's going to also be necessary to calculate how much ground you cover during your 2 min climb to cruise. And critical to answering the question correctly.

Now, IF WE ASSUME a constant groundspeed of 93 kts, from point to point, that gives a flight time of 36.5 minutes.  If we further assume the two minutes of climb are not enroute and just maneuvering from takeoff to on course right over the Claxton airport and we descent into Varnville at 93 kts as well, we get a figure of 38.5 minutes total flight time.  Therefore, I'd select 'B' as my answer.

As a side note, I landed an LSA out at Varnville only once and that place is virtually abandoned; it was difficult to identify as an airport from the air, the runway is anemic and derelict, there are virtually no buildings there and all I could find for traffic there was a decrepit C-150 rusting in the sun.  I took off again - and very glad my engine didn't quit, leaving me stranded there.


How does a Mach Meter determine the speed of sound at a given altitude? By my understanding, the Mach Number at a given altitude is calculated by dividing IAS by the speed of sound at that altitude. So how is this speed of sound calculated to display the Mach Number on the Mach Meter? Does the Mach Meter share the same pitot tube used to calculate airspeed?

An (analog) machmeter looks something like this:

So it's more like an more complex version of the airspeed indicator, in this case correcting for the altitude in the process. That being said, I found this extract apparently from an FAA publication:

  Some older mechanical Machmeters not driven from an air data computer use an altitude aneroid inside the instrument that converts pitot-static pressure into Mach number. These systems assume that the temperature at any altitude is standard; therefore, the indicated Mach number is inaccurate whenever the temperature deviates from standard. These systems are called indicated Machmeters. Modern electronic Machmeters use information from an air data computer system to correct for temperature errors. These systems display true Mach number.

Most systems today use more detailed data from sensors to give a correct value through a variety of (complex) calculations.

A little more discussion is available on PPruNe.

Side note: Speed of sound ($a$) itself is solely determined by temperature (that being said, you are able to determine it from pressure, as pressure is a function of temperature) hence the problem with the analog system above.

For air:

$$a=\sqrt{R{\gamma}T}~m/s$$

Where:

$R=287$  Specific Gas constant [dimensionless]

$\gamma=1.4$  Specific heat ratio [dimensionless]

$T=$ Absolute temperature [K]

Remember that you're reading off indicated airspeed [IAS] in knots in the cockpit, which is not the same as True airspeed [TAS] converted to m/s, in case you're trying to work out your mach speed manually ($M=\frac{TAS}{a}$)

For use without knowledge of airspeed & temperature, Wikipedia gives the following formula for subsonic flows:

$$M=\sqrt{5((\frac{P_T}{P}+1)^\frac27-1)}$$

Where:

$P_T=$ Total Pressure

$P=$ Static Pressure


How many four-engine commercial passenger jetliner types are currently in use? Just heard following somewhere:

It is easy to distinguish four-engine passenger jetliner type, because there are only three of them:

if it has "hump" upper deck then it is Boeing 747,
if it has two decks then it is Airbus A380,
otherwise it is Airbus A340.

Is this statement true?
I'm asking about commercial passenger jetliners only. So no cargo, no military etc.

Well, the 3 points you make are easily demonstrable to be true, and also a fairly unique feature of all three if looked at side-by-side.

The 747 is the only one with an obvious hump towards the front of the aircraft. This upper row of windows is unlike either of the other two

Photo Aldo Bidini:: source: http://www.airliners.net/photo/Alitalia/Boeing-747-243B/1200648/L?sid=f499b3169d12a0d4f410846e6512443a

The A380 has an entire upper row of windows - it does indeed have 2 full decks.

   Richard Vandervord source: http://www.airliners.net/photo/Etihad-Airways/Airbus-A380-861/2574151/L

If it has 4 engines, but neither a half upper deck and hump or a full upper deck (and it's an airbus!) then yes it is an A340

Aero Icarus source: https://www.flickr.com/photos/46423105@N03/5445375360/

However, that is not all the 4 engine passenger aircraft.

The BAe 146 is a 4 engine regional airliner, and you could add to your distinguishing features "has a T-tail, must be a 146". It is also the only one of the bunch with a high wing.

   Adrian Pingstone source: https://commons.wikimedia.org/wiki/File:Lufthansa.rj85.arp.jpg

And then we're into the Ilyushins. The Il-96, is easily distinguishable from the similar(ish) A340 as it is considerably smaller - hard to tell from a close-in photo, but in real life if one were parked next to the other the IL-96 is smaller.

Anna Zvereva source:https://www.flickr.com/photos/130961247@N06/31268448486/

The Il-86 has 4 engines but does not fit your criteria, as it only remains in service with the Russian Military, but the Il-62 is still in commercial service. It's very easy to distinguish by having its 4 engines mounted on the tail

Tim Rees source: http://www.airliners.net/photo/LOT---Polish/Ilyushin-Il-62M/1033235/L


How is drag created from wingtip vortices? What is the reason for the drag due to wingtip vortices?

This question is about (general) performance, but doesn't answer the drag aspect.

Wingtip vortices don't create drag, just as wet streets don't cause rain.

Lift creation and viscosity create drag. Drag is composed of pressure drag and viscous drag, and induced drag is one part of pressure drag. Unfortunately, the Internet is full of memes which attribute induced drag to those wingtip vortices, but some swirling air behind a wing can hardly cause any drag, can it?

See it another way: If the wing were not creating any lift, the air would not flow around the tip and curl up. So why don't we read that the tip vortex is the source of lift? This uses the exact same logic as saying that the tip vortex creates drag, and is equally wrong.

Wingtip vortices are just the tip of a full vortex sheet which leaves the wing. This vortex sheet is the consequence of the wing accelerating air downwards. Now instead of repeating myself all over again, please allow me to point you to the many other answers which explain what is going on:

This answer explains in detail how lift is created and how the downward acceleration of air is accomplished.
This answer goes into the formation of the wake and the wingtip vortices.
This answer shows why more wingspan reduces induced drag. It matters little whether the wingtips are turned up, down or continue straight: A larger wingspan reduces induced drag.

Winglets increase the amount of air involved in lift creation and reduce induced drag for the same lift. In most cases they are used to create more lift with the same geometric wingspan without incurring a disproportionate drag penalty.


Would an aviation engineering background be helpful for a Flight Data Monitoring Analyst? I am working now in the aviation sector and I am technical administrator for planning aircraft maintenance events. Recently I search for new opportunities and found "Flight Data Monitoring Analyst"? Could someone tell me should I have an aviation engineering background to qualify this job?

In their job description, candidates need to have bachelor degree and experience working in the aviation sector.

Skybrary's page on Flight Data Monitoring defines Flight Data Analysis:

  Flight Data Analysis is founded on Operational Flight Data Monitoring (OFDM) which in North America has become known as Flight Operations Quality Assurance (FOQA). It is a process which routinely captures and analyses recorder data in order to improve the safety of flight operations.

  Flight Data Analysis. A process of analysing recorded flight data in order to improve the safety of flight operations. (ICAO Annex 6 - Operation of aircraft)

  Operational Flight Data Monitoring (OFDM) is the pro-active use of recorded flight data from routine operations to improve aviation safety.

So, this position would be focused on analyzing data from the flight data recorders to make sure the aircraft are being flown in safe and efficient manner.

Engineering (both in aviation and in general) is concerned with design. While an aviation engineering background would probably provide some useful insights, it normally isn't necessary for a position that is not concerned with designing aircraft or aircraft systems.

It would seem that piloting knowledge would be more necessary here than engineering knowledge. In order to analyze whether flight operations are being conducted safely and efficiently, you first need to know what constitutes safe and efficient flight. Technical knowledge of aircraft systems would certainly be needed, but probably more on a pilot level than an engineer level. Additionally, statistical analysis experience will almost certainly be needed.

As an example, here are the qualifications listed for a Flight Data Management Analyst position that I found in a search:

  Essential skills and qualifications:

  Experience in statistical analysis and preparation of graphical representation of data
  Hold accreditation as an aircraft accident/incident investigator or equivalent
  Hold accreditation as quality auditor or equivalent

  Desirable skills and qualifications:

  Experience as a pilot
  Sound aviation technical knowledge in Flying Operations, or equivalent
  Experience in analysis of flight data, using flight data analysis systems (e.g. ADI, Aerobytes, AirFase)
  Experience in utilisation of flight simulator software to recreate flight events
  Familiarity with current EASA regulatory legislation
  Experience in undertaking investigations


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.


How can I find a deregistered airplane? I'm trying to find a 1959 C172 tail number N7393T.
It was my grandfather's and the last registered record of it was near Glendale AZ.  It was deregistered in 2015 and I found out that since it cannot be reregistered for 5 years it may have a new tail number. Any tips on tracking and finding this plane would be helpful.

Sorry to be the bearer of bad news. But, you have already asked this question on www.airport-data.com. A quick search in the FAA search database with the tail number or serial number (which can be found using the tail number) shows that it has not legally flown in the US in almost a decade. So, it is either sitting somewhere as a ramp queen, registered overseas, or not in existence any longer.
Try contacting the last person to register it. Otherwise, it would be like trying to find a salvaged car after it has been junked. It will only pop up if it is reregistered. However, you can pay a private firm like a law firm to research the aircraft’s certificate of title (or simply title). It would be like searching a deed.


Why are all-moving horizontal stabilizers common but all-moving rudders rare on fighters? According to Wikipedia

  Stabilators were developed to achieve adequate pitch control in supersonic flight, and are almost universal on modern military combat aircraft. All non-delta-winged supersonic aircraft use stabilators because with conventional control surfaces, shock waves can form past the elevator hinge, causing severe Mach tuck.

If this is the case with supersonic pitch control, why use an all-moving elevator but a conventional rudder? Doesn't yaw control have the same issue? Or is it because rudders are rarely used?

Basically, in fighter aircraft you need a lot more of elevator than rudder.

For most aircraft, the required size of the elevator is determined by one of the two corner cases:

Sufficient control and balance at low speed, particularly on landing;
Sufficient control for high-G manoeuvres.

For fighters and aerobatic aircraft, the latter is usually the main factor; for others, the former.

In contrast, rudder is usually sized for crosswind landing and, if applicable, for the asymmetric thrust (one engine out) case. It's easy to see that due to closely packed engines on most fighters and higher speeds, both these factors are relatively smaller compared to other aircraft (e.g. airliners).(1) Whereas the elevator demand gets worse. This is why.

There are two main problems that arise at supersonic speeds.

The centre of pressure of the wing (and the neutral point) moves back significantly. This obviously creates a strong nose-down moment (and makes the aircraft statically very stable in pitch for the same CG), requiring a lot of control to re-trim the aircraft and execute any manoeuvre. This is the reason for 'Mach tuck' (in fact, this is the Mach tuck), and not the rubbish from the quoted Wikipedia passage.
Efficiency of the elevator fades. At lower subsonic speeds, the elevator effects the air not only above/below it, but also ahead of it. The approximate efficiency of the conventional elevator at such speeds can be expressed as

$$k_{\mathrm{elev}} = \sqrt{\frac{ S_{\mathrm{elev}}}{S_{\mathrm{stab}}}}$$

Therefore if the elevator $S_{\mathrm{elev}}$ occupies half of the stabiliser area $S_{\mathrm{stab}}$, its effect will be not $0.5$ but rather $\sqrt{0.5} \approx 0.7$ (compared to the all-moving surface). But at supersonic speeds such propagation upstream cannot happen, and the efficiency falls to the area ratio, i.e. $0.5$ in this example. This favous all-moving surfaces.

The second point affects the rudder just the same, of course. But the static directional stability (point 1) doesn't increase like it happens with pitch (in fact, it can fall), and the overall demand is lower, so conventional rudder is still acceptable. Nevertheless, there are a few aircraft with all-moving vertical tail, for example, Tu-160.

In other circumstances, conventional control surfaces are better (i.e. lighter), so they are used whenever possible.

(1) This should not be confused with the whole vertical tail sizing. This one is often determined by the stability dynamics, and directional stability of supersonic aircraft can be rather bad, demanding big tail - but not necessarily big rudder.


Are the student solo endorsements a “package deal” with that one specific instructor? If someone receives a student who’s completed his old instructor’s pre written solo exam and received an endorsement, do I need to give him my solo test and endorsement?
Or go ahead and complete the flight training/proficiency and 90 day endorsement?
My understanding is that it’s a "package deal", one instructor must do it all. Except the XC pre-flight planning preparation endorsement, and this one can be given by any instructor.
Can someone confirm this? With possible quotes from FAR, ACs or interpretations.

The FAR's don't talk about whether or not a CFI can accept another instructor's solo endorsement. If the student has the endorsement, the 90 day period has not expired, and the make and model of the aircraft in the endorsement matches, then the student is technically good to go.

That said, a good CFI would carefully review the student's log book and, if necessary, require additional instruction/review before the allows the flight school to rent the student an aircraft. The relevant FAR is 61.87.