What does it take from the airlines to be ETOPS certified? I have been told that the airlines to be certified for ETOPS apart from the aircraft certification, engineering wise it should have some conditions met in order to get the certification and to maintain it too.

The requirements for ETOPS certification by the FAA are outlined in the following Advisory Circular:

  ETOPS QUALIFICATIONS. The unique nature of ETOPS necessitates an evaluation of
  these operations to ensure that the certificate holder's proposed programs are effective. The FAA
  will review the certificate holder's documentation and training programs to validate that they are
  appropriate for ETOPS. To receive approval to conduct ETOPS the certificate holder must
  satisfy the following conditions:

  a. Airplane. The specified airplane-engine combination listed in the certificate holder's
  application must have been certificated to the airworthiness standards of transport category
  airplanes and must be approved for ETOPS. Guidance for airplane ETOPS type design can be
  found in AC 25.1535-1 and § 121.162.

  [...]

  b. Flight Operations and Maintenance Requirements. The certificate holder must show
  compliance with the flight operations requirements discussed in paragraph 303 and the
  maintenance requirements discussed in paragraph 301.

  c. Training Requirements. The certificate holder should show that it has trained its
  personnel to achieve competency in ETOPS and must show compliance with the flight
  operations and maintenance training requirements discussed in paragraphs 302 and 304.

  d. Requirements For ETOPS Approval. Before the FAA grants ETOPS operational
  approval to an applicant for two-engine ETOPS, the certificate holder must be able to
  demonstrate the ability to achieve and maintain the level of propulsion system reliability that is
  required for the ETOPS-approved airplane-engine combination to be used (appendix P to
  part 121, section I, paragraph (a)). The certificate holder must also demonstrate that it can
  operate the particular airframe and other airplane systems at levels of reliability appropriate for
  the intended operation. This can be achieved directly by a successful in-service operational
  history or by successfully validating all the required ETOPS processes according to the
  Accelerated ETOPS Application Method in Appendix 3 of this AC.

  e. Accelerated ETOPS Application. An applicant for an initial operating certificate who
  is applying for ETOPS authority at entry into service under the Accelerated ETOPS Application
  method must comply with the same requirements for certificate holders outlined in this AC. It
  should be understood that validation of an applicant with no previous operational experience
  should be more robust than would be necessary for a certificate holder with operational experience. As is the case for all Accelerated ETOPS approvals, the Director, Flight Standards
  Service must be satisfied that the applicant can operate to the standards expected of an
  experienced ETOPS operator from the first day of service.

(FAA AC-120-42B)

The referenced paragraphs 301 to 304 can be found in the same document and provide detailed requirements for operations, maintenance and training.

The details may vary around the world, but other aviation authorities will have similar requirements for certification.


Between a helicopter and an airplane, which requires more power to fly, for a given TOW? For the given same mass (say it 400kgs), which one requires more power (in HP) between helicopter and airplane? Say that both are designed maximum (the required material are considered during design) to minimize the required power.

Edit: Question should be like this: Which one is requires more power to lift a helicopter (to make it hover) and to make a fixed wing airplane fly? Not to make them move at the same speed.

Airplanes fly by creating lift from their wings. This causes some drag, but good wings have lift/drag ratio's in the range 15-20. That means the lift-dependent drag is only 5% of the lift. Helicopters on the other hand generate lift directly from trust; there is no multiplier involved.

E.g. a 4000 kg plane will have a weight of 40.000 Newton, so the drag incurred will be 2000-3000 Newton. A 4000 kg helicopter will need to produce 40.000 Newton of lift just to hover.

Of course, planes and helicopters both have additional drag from forwards airspeed, and for planes this is obviously unavoidable to prevent stalls.


How can speed and power be made independent in an airplane? I heard a piece of information many years ago, and the more I think about it, the less it makes sense. It was like:

When airplanes what to raise altitude, they do not increase speed, but they increase power. It is like when going up a hill, you do not walk faster, you just push harder.

Now, I understand the statement at an intuitive level. I understand what it means for me to go up a hill, because I know what I feel.
But things are quite different with motorized vehicle in general, and maybe with airplanes in special.
My understanding is that the following equation is (relatively) true (at least as a principle):

power = rpm * torque

and my understanding is that

speed = rpm * coef

so in the end

power = f(speed)

or

speed = f-1(power)

where f is mostly (?!) multiplicative, or at least linear(-ish).
Now, how can be power increased, without increasing speed?
This statement comes to confirm that I miss some information, since the general knowledge defies my formulas :)

There are two parameters that an A/T can maintain, or try to attain: speed and thrust.
(I understand that thrust is power).

The only way I can explain it is like this (and I need some confirmation):
The (pilot) "asks" to increase the rpm (as a base parameter, speed and power being derived parameters). In vacuum, all the energy is used or increase RPM, so power and speed remain proportional. But in the real world, and especially during flight, a lot of the energy is used or lost in many places. So speed and power no longer remain proportional, the difference being lost (e,g, to friction).
Additionally, please provide a better explanation of what I just wrote. I am really interested to understand the basics of this topic.
Basic formulas are OK. (Complicated) Integrals and derivatives should be avoided please :)

Notes:

I am not (by far) a mechanical engineer whatsoever. As a hobby, I practice "mental" mechanical engineering - trying to understand how some things can be designed; or trying to understand how some things are implemented. My background is more related to electric / electronics, software, management.

In the example with a man climbing a hill, my explanation makes some sense (to me): I prepare to increase the speed by using more power, then I make a short break to rest the leg, and to move to the other leg, and then again use higher power and so on. It is mostly like a human-implemented PWM. This is how the speed can remain constant, while the power increases. But how does this work for the engines / airplanes?

I am quite sure that ultimately everything is related to how much fuel is burned in the unit of time. Unless I am wrong.

My knowledge about airplanes and flight are limited at best, even though I understand some principles.

The problem is your assumption of

speed = rpm * coef

This is only true as long as there is a rigid connection between the RPM and the medium against which the speed is measured.
Let us consider a car for a moment. In a fixed gear, there is a fixed relationship between the engine RPM and the RPM at which the tires rotate. As long as the tires are not skidding, this will directly translate to a motion w.r.t. the road (against which speed is typically measured for a car). This results in the linear equation you show.
This is however not true for an airplane, where the propeller RPM does not directly translate to a speed w.r.t. the air because air is not a solid (otherwise it would be true and you can think of the propeller as a a screw that drives into the solid). Air can flow through the propeller without moving the plane. Consider e.g. a plane that is tied down on the ground and therefore cannot move w.r.t. the ground. You can still start the engine and run the propeller, which creates an airflow behind the propeller, but does not cause any movement. The same could not work with a car, as long as the tires are not allowed to skid.
In flight, the accelerated airflow behind the propeller creates thrust, which is a force that can accelerate the aircraft forwards. The actual motion will also depend on the aerodynamic forces (lift and drag) as well as gravity of course. A higher propeller RPM (at the same blade angle) will give you more thrust, but there is no rigid connection to speed.


Does this Lear 35 have missiles on it? Janes aircraft recognition guide has a picture of this plane on the Lear 35 page. Does it have missiles on it or is this some special modification?

No, it's not a missile, it's a towed target:

Towed targets are used for electronic warfare and gunnery training. The can serve as a radar target or visual target during military exercises.

The 'missile' is on a long cord and can be reeled from the aircraft. The pod that you see here is a MTR-101 reeling system with the capability to drag the target up to 30,000 ft behind the aircraft.

If you are interested in flying these kind of missions, it seems  L3 is looking for a new First Officer for their Learjets.


What are the pros and cons of having a side-stick versus a centered control stick in a fighter aircraft? The Eurofighter Typhoon features a centered control stick:

While for example in the F-16 the stick is on the right side panel:

I find the latter configuration much more natural/ergonomical. Especially since the concept of HOTAS (Hands On Throttle-And-Stick) implies that the pilot has his hands on the same control element most of the time.

I've heard of one reasone for having a center stick is to allow for ambidextrous operation (operations with both hands, alternatively).
But this seems to be counter-intuitive with HOTAS, especially since the throttle controls are still on the left side only.

I find it difficult to image an ergonomical position for the pilot while holding a center-stick and a left hand throttle control.

So what are the reasons for a center stick in the Typhoon?
Any experiences of pilots having flown both types of configurations?

Center mounted sticks are useful for maintaining positive control of the aircraft while operation some cockpit system on the right consoles and flying with your left hand.  It’s also useful in an emergency, say if your right arm was injured by shrapnel, etc and cannot actuate the stick effectively, requiring you to fly with your left hand.

Side sticks do have the advantage of less cockpit clutter.  The stick is mounted off to the right and doesn't directly block critical instruments from the pilot's view or have its range of motion restricted by flight gear, kneeboards, etc.

As far as size and weight are concerned, both center mounted and side sticks are pretty much the same in a fly-by-wire aircraft - just a 4-way transducer LRU with a handgrip attached to it.  In a/c with conventional control systems the center stock was a necessity as it acted as a lever arm allowing the pilot to overcome aerodynamic forces on the control surfaces with muscle power alone and one could force a maneuver using both hands.  In the age of hydraulic flight controls and fly-by-wire, this is irrelevant.

As to ergonomics, it's fairly comfortable to fly a center stick as your wrists will naturally rest on your thighs when seated and your hands naturally float to that position.  Side sticks are also comfortable but require an armrest to operate effectively, particularly when pulling Gs.


How can I build the 40 hours instrument time required for an instrument rating? 14 CFR 61.65(d)(2) says:

(2) Forty hours of actual or simulated instrument time in the areas of operation listed in paragraph (c) of this section, of which 15 hours must have been received from an authorized instructor who holds an instrument-airplane rating, and the instrument time includes:

So 15 hours must be with an instructor.  What about the other 25?  Can I fly in instrument meteorological conditions (IMC) "solo" (not the hood) like I did for my private pilot license (PPL) after an instructor sign off?  Or does this just mean that I need another instrument rated (IR) pilot with me, but it doesn't necessarily have to be a certified flight instructor (CFI)?  If that is the case, and I use the hood rather than actual IMC, does the other pilot need an IR or just a PPL?
Basically, how do you fulfill the other 25 hours?

The remainder of the 25 hours can be completed with a Safety Pilot, a CFI, or a CFII.

A safety pilot must be able to act as PIC of the aircraft you are flying. Also, if the safety pilot is acting/desinated as PIC, both you and the safety pilot can log PIC time for when you are flying under the hood. If you are acting as PIC, the safety pilot can log SIC time for being a required flight crew member (FAR61.51(f)).

You cannot file an IFR flight plan or fly in IMC unless a current Instrumented Rated pilot is on board and acts as PIC.


Is it safe to fly with a B737-800? Is it different from a B737 Max 8? I'm flying from Costa Rica to Chile in November with a B737-800 plane. I'm wondering if this is a different aircraft than the B737 Max 8 or if it's the same?

All B737 Max, as of today 19-Sept-2019, are still grounded and will be for the foreseeable future. So if you are flying in an aircraft, you are guaranteed that it will not be one of those.

As for the underlying question "is it safe to fly in airplane model "X"?" the answer always is that if authorities are allowing it to fly, it is safe to the best of our knowledge.


Can you disengage A320 autopilot with stick pressure? I was recently reading that in most military jets, auto-pilot can disengaged without hitting the button, by applying 5lbs of pressure to sticks.

Does this work in commercial airliners such as the A320?

Yes. I’m not sure of the amount of force, but from the A320 FCOM:

  AP DISENGAGEMENT

  AP1 or 2 disengages when:

  The pilot presses the takeover pushbutton on the sidestick.
  The pilot presses the corresponding AP pushbutton on the FCU.
  The pilot pushes on the sidestick harder than a certain threshold or moves on the rudder pedals above a threshold.
  The pilot moves the pitch trim wheel beyond a certain threshold.
  The other AP is engaged, except when localizer/glideslope modes are armed or engaged, or when the rollout or go-around mode is engaged.
  Both thrust levers are set above the MCT detent and the aircraft is on the ground.
  The aircraft reaches the MDA-50 feet (MDH-50 feet), or 400 feet AGL if no MDA/MDH, with APPR mode engaged and a non-lLS approach is
  selected.
  One of the engagement conditions is lost.

  Furthermore, in normal law with all protections available, the AP will disconnect if:

  High speed protection is active;
  Angle-of-attack protection is active (α prot + 1° is reached);
  Pitch attitude exceeds 25° up, or 13° down, or bank angle exceeds 45°;
  A rudder pedal deflection is more than 10° out of trim.

  The standard way for the flight crew to disengage the AP is to press
  the takeover pushbutton on the sidestick. When the AP is OFF, the
  associated FCU pushbutton goes off. and "APl" (or AP2) disappears from
  the PFD’s FMA.

  *emphasis mine


Is the ATR empennage configuration considered a T-tail or a cruciform tail? How is the ATR 42/72 empennage considered? Is it a T-Tail or a cruciform tail?
From the image the elevators are placed quite high on the tail that they can be considered as a T-Tail but is it so?

Looking at the tail of a 727 the elevators are placed at the top of the tail but just leaving the space for the mechanism to move them, whereas on the ATR they are placed in a slightly lower position.

Are there any technical specifications and measurements that clearly define the difference between the two mentioned configurations?

I understand that cruciform means "similar to a cross" but it would be interesting to know, as previously mentioned, if there are specifics about this definition making it clear for everyone from a technical point of view. (briefly, when does a T-Tail become cruciform?)

As far as technical specifications are concerned, some explanation is:

Excerpt from Wikipedia (formatting is mine):

  T-tail

  DESIGN: The horizontal stabilizer is mounted on top of the fin,
  creating a "T" shape when viewed from the front.

  PURPOSE:

  T-tails keep the stabilizers out of the engine wake, and give better pitch control.
  T-tails have a good glide ratio, and are more efficient on low speed aircraft.
  However, T-tails are more likely to enter a deep stall, and are more difficult to recover from a spin.

  T-tails must be stronger, and therefore heavier than conventional
  tails. T-tails also have a larger radar cross section.

  Cruciform tail

  DESIGN: The horizontal stabilizers are placed midway up the vertical
  stabilizer, giving the appearance of a cross when viewed from the
  front.

  PURPOSE: Cruciform tails are often used to keep the horizontal
  stabilizers out of the engine wake, while avoiding many of the
  disadvantages of a T-tail.

In reference to your comparison between ATR 42/72 with Boeing 727, if we take out the difference in tail heights (ATR 42: 24' 11"; ATR 72: 25' 1"; B727: 34' 0"), the position of horizontal stabilizer on vertical stabilizer is almost the same on these three airplanes. So they all match closely to a T-Tail configuration rather than a cruciform.


Is there any engine that doesn't use a propellant to produce thrust? As far as I know, all engines used in aircraft produce thrust by means of some propellant: kerosene, hydrogen peroxide etc. Maybe I've missed something, but could you tell me, are there any engines that can produce thrust without using exhaust gases expelled from the nozzles? Is it even possible?

Yes there are. Although they are not for commercial aviation. One example are solar powered engines:

Source Wikipedia

Alternatively, there are other means of storing energy - rubber bands, but this one is just for model aitplanes.

Source: Pinterest

But in either case, you need store energy somewhere, and best way is to use oil-based fuels.


Why is the first turbine in a turboprop (or turboshaft) connected to the compressor? Typically the first turbine after the combustion chamber drives the compressor as shown in this picture.

(wikimedia.org)

This first turbine spins the fastest and harvests the most energy from the gas flow. This seems inefficient when you want to maximize power output from the power turbine. So why not have the power turbine the first to take advantage of the gas flow and then the compressor/gas producer turbine second?

You can only use for shaft horse power what is available after the energy to drive the compressor is subtracted. This subtraction is done by the high pressure turbine. Any energy left in the exit flow after that can be extracted to drive a propeller, a fan or a generator.

What happens in your arrangement if the power turbine extracts too much energy to keep the core engine running? No, clearly the priority has to go to keeping the core engine alive and to only use what is left.


Will a Secondary Surveillance Radar be affected by a 300m high wind turbine? 60 wind turbines are located at a distance of about 30 km away from a Secondary Surveillance Radar installation; what will be the impact of this?

My less than stellar knowledge of radar systems tells me that there shouldn't be an issue, since its a secondary radar and not a primary radar (the blades are big enough to be mistaken for an aircraft) which relies on reflection.

But the 30 km distances makes me doubt if this will actually be the case, might a 300m high obstacle in a radar's direct line of sight might cause problems?

No they won't, since secondary surveillance radar (SSR), as you point out, does not rely on reflecting electronic pulses, but rather on digital communication with an aircraft transponder.

Transponder signals do still travel in a straight line (line of sight), so obviously putting a very large obstacle (such as a mountain) close to an SSR will limit the radar coverage in the area behind the obstacle.


Is there any mechanism in engine mount to prevent shock loads on engine while landing? How engine is mounted in wing is restricting motion in any direction but is it still resistant to shock loads, or is there any mechanism inside engine associated to bearings that will absorb shock loads that occur in spools?

"Shock" loads on landing can be transmitted to engine components.  The original poster appears to be asking about turbine engines specifically.  The significance of a hard landing on the engine spools themselves will be shaft flex and case flex, and the possibility of blade rubbing (and erosion).  This is a concern with a hard landing, and something that must be considered.  There are not "shock absorbing" features or capabilities built into bearings in engine spools; these are intended to have minimal friction in rotation, but no concentric movement about their axis.  It is possible in severe turbulence, and in a hard landing, to experience case or blade damage or wear, and there are inspections prescribed for certain components in certain engines to address this.


Do fighters have black boxes? Or is it just commercial aircraft? I was watching an episode of Scorpion where an "F-120 Firehawk" crashed and they looked at its black box. So, do normal, non-imaginary fighters have them?

Yes, most military aircraft, including fighter aircraft, are equipped with a "black box" called flight data recorder (FDR) / crash survivable memory unit (CSMU) / integrated monitoring and recording system (IMRS) / deployable flight incident recorder set (DFIRS).

Sources 1, ( B-1B, F-22, T-45, B-2, F-4, F-15, F-16, C-5 Galaxy, NATO AWACS, and the Space Shuttle)
2. (F-18, floating black box)


What should a pilot do when facing a sudden tail, cross, or head wind? Consider a pilot is flying a conventional fixed wing airplane with a ground speed of 60km/h with no wind. Then suddenly the wind starts blowing at 20km/h in either of the following directions:

from back to front (tail wind).
from front to back (head wind).
from left to right (cross wind).

What should the pilot do to maintain speed and altitude in each of the possible situations above?

Many people stress energy and airspeed management, this is a good example.

Sometimes a strong gust can reduce airspeed faster than your engine can increase it.
The sudden tail wind gust is very dangerous near the ground. Increase throttle and pitch down. Use your potential energy plus the engine thrust to maintain airspeed.  Wind conditions found in microbursts can create this effect.  Constantly check airspeed.

A strong headwind gust has the opposite effect, causing a momentary increase in airspeed, and increase in altitude.  Rarely a problem, keep an eye on airspeed as the gust passes, continue to use pitch and power to control airspeed and altitude as needed.

Side gust effect will affect your heading much more than speed and altitude, as it's velocity change does not add or subtract from airspeed.  Effects here could include a sharp roll initially away from the gust, and the nose being pushed into the wind from side force on the empennage. A stable plane should mostly self-recover without significant loss of altitude.

The mantra "the plane just moves with the air mass" does not apply to gusts.  This is why pilots generally approach at slightly higher airspeed under those conditions.


What is the ratio of Commercial + ATP pilots with employment as pilots in the US? Of all certificated commercial/ATP pilots in the US under the age of 65, how many are employed in full-time pilot roles vs commercial/ATP pilots with some other profession than a pilot?

You can find the full database of FAA information at this link but more useful they offer some statistics here.

As of 2018 there are 162,145 individuals that carry an ATP level ticket and 99,880 Commercial tickets out there.

The Bureau of Labor Statistics provides some employment stats however their stuff only goes up to 2016. As of then they claim there are 124,800 jobs for the title "Airline and Commercial Pilots" If we look back at the FAA's 2016 data we will see that in 2016 there were 157,894 ATP tickets out there and 96,081 Commercial level tickets. Assuming that BLS rolls up quite a bit under "Airline and Commercial Pilots" including 135 ops, flight instructor and full on 121 jobs there are 124,800 jobs for 253,975 possibly qualified people.

So there are roughly 129,175 people with ATP or Commercial level tickets not working in ATP/Commercial Aviation jobs.

Note: This does not account for people over 65 (data that it does not appear is released) as well as people who may have lost their medical or otherwise cant fly. However the FAA uses the phrase "ESTIMATED ACTIVE"  which could mean they account for all the above noted things.


How hard is it to fly with night vision goggles? I was talking to a Sheriff's Department helicopter pilot and he was saying they fly around at night with night vision goggles.  I know the military does too.

What are some of the considerations that pilots flying with night vision goggles have to deal with when learning to fly with them?

How long does it take for someone to be certified/trained to fly with night vision goggles?

What is the most difficult part about it? Could civilians do it if they owned the gear?

All those answers are pretty wrong.  One eye..Can't read the instruments.. Aviation ANVS like the ANVS 9's are dual tube.  You focus them to your liking,individually for each eye!  I personally get 20/20 with them and you mount them high and simply look under them to read the instruments! I have over 7,000 hours of single pilot NVG.  They make things safer, easier, and it's just like flying during the day, only everything is green.  Things like towers and wires (powerlines) are actually MORE visible under NVG's.  It usually takes established pilots with zero NVG time only a few hours to adjust.  Nothing to it.


What should I study to understand basics of aircraft construction? I'm trying to undestand principles of construction of fixed-wing subsonic aircraft.

I have already read explanation on things such as Neutral Point, Static Margin, etc, but I'd like to know how they are linked together, what are typical values they have and why, what are pros and cons of different schemes, and so on. Some of this can be found here, but I think it would be more sound to learn basics first, and start looking for details afterwards.

A good example of literature (or Internet resource) I seek can be "The Jet Engine" book by Rolls Royce. It explains nature of processes while don't digging too much in formulas.

Thank you!

I have seen many universities that they suggest Anderson's Introduction to Flight for the first course in aerospace engineering. This book contains fundamental aspects of the aeronautics.

Regarding construction principles, a good knowledge of aerodynamic, propulsion, structure and flight dynamics is required before getting into aircraft design. Meanwhile, as the first step you can familiarize yourself with the anatomy of the airplane with Stinton's Anatomy of the Aeroplane, and then going to aircraft design books such as Roskam's Airplane Design Books or Torenbeek's Design book.


Can a paying passenger ride in one of the cabin jumpseats? Is there any regulation that prohibits passengers from using a cabin jumpseat (normally used by cabin crew) if there is no passenger seat available? Like the two shown below.

In other words, can any of the cabin jumpseats be sold? (Given that cabin members are fewer than the available jumpseats of course.)

(Source)

If you're talking about one of the jumpseats in the flight deck (as opposed to the ones FAs use in the passenger cabin,) then, no, it's definitely not allowed during flight, at least not in the U.S. or E.U. It may be allowed elsewhere, though.
The United States
Relevant regulations for the U.S.: 14 CFR 121.547 for domestic air carriers and 14 CFR 129.28 for foreign ones.
The regs are a bit too long to quote here, but, to summarize: You're not getting into the flight deck during flight unless you have a valid, FAA-approved reason to be there. The mentioned exceptions were mostly FAA, NTSB, airline, or manufacturer employees and, even then, only ones with legitimate safety or operational reasons to be there. It is also mentioned that the PIC retains the emergency authority to deny access to even the FAA/NTSB/etc. personnel in the interest of safety.
Apart from all of the aforementioned categories of people allowed "a crewmember" is listed separately as being allowed, of course.
Also, there's 14 CFR 121.557(a) which says:

In an emergency situation that requires immediate decision and action the pilot in command may take any action that he considers necessary under the circumstances. In such a case he may deviate from prescribed operations procedures and methods, weather minimums, and this chapter, to the extent required in the interests of safety.

This exception allows the pilot of a Part 121 operation to deviate from any Federal Aviation Regulation when it is required in the interest of safety. So, the Pilot-in-Command may allow you to sit in the flight deck if he deems it's necessary for safe operation of the aircraft. As such, this exception allows other pilots to access the flight deck in the very rare instances where one of the pilots falls ill and the pilot-in-command decides to get another (non-airline) pilot who happens to be on board to sit in the right seat to help out for the remainder of the flight.
See Pondlife's excellent answer here for more information regarding emergency authority of the pilot-in-command.
The European Union (EASA)
This answer over at travel.SE also mentions that CAT.GEN.MPA.135 is the relevant EASA (E.U.) regulation preventing passenger access to the flight deck during flight.
Exceptions
As a notable exception, this answer here at aviation.SE does mention that South Africa allows licensed pilots to visit the flight deck during flight and that you might even get to ride in the jump seat.
Conclusion: I need to visit South Africa. :)
Other Related SE Questions

Can a passenger request to visit the cockpit during a flight? (Aviation)
Can I get a photo with the pilots? (Aviation)
Can a child still visit the cockpit during flight? (Travel)
Can passengers visit the flight attendants' sleeping quarters? (Travel)


What was the normal flight path for a passenger aircraft from New York to Miami in 1955? What was the normal flight path a passenger aircraft would have flown from New York to Miami in 1955? Like Pan American, flight 914.

Probably not a whole lot different than today. You likely won't get a very exact answer to a general question like that unless you can narrow down specifically what kind of detail you seek.

Obviously GPS waypoints wouldn't have been used, but any NDBs in use at the time probably would be. My advice would be to search for a vintage chart from that era and plot the most direct route using depicted navaids.


How do ADS-B and ADS-C get used on transoceanic flights? I have three questions regarding ADS-B and ADS-C. (Hopefully you don't feel my questions are not related.)

(1) What's the scope of availability of ADS-B? Let's say an airliner equipped with all the necessary equipment for ADS-B in the US flies over to Tokyo. When or where does ADS-B stop working?

(2) I read from this post that ADS-C is used in some oceanic environments including the Pacific between certain flight levels. Roughly what percentage of transoceanic flights currently take advantage of the ADS-C system?

(3) I assume ADS-C is not a common transoceanic surveillance system, if it's true ADS-C is only used above certain flight levels. If so, what are alternatives to ADS-C? What other (surveillance) systems are being used to follow transoceanic flights? Self-reporting? GNSS? Or what?

1) ADS-B will stop working when the transponder is switched off at the gate after arrival in Tokyo. Airliners use the 1090 MHz Extended Squitter variety of ADS-B which is the worldwide standard.

2) I don't have hard numbers but I guess it is approximately 90 percent of the flights. At most economical cruise flight levels, ADS-C is mandatory.

3) ADS-C is a common system. For aircraft not equipped, position reporting of HF is the alternative. And soon space based ADS-B will be available as well.


What are the benefits of mounting an engine above the fuselage? I'm wondering what advantage/disadvantage, if any, does mounting an engine above the fuselage give? This question comes up after seeing the Macchi M.33 below:

The engine mounted in such a way does look interesting, but I'm wondering if it might make the plane want to dip down slightly. Any help would be appreciated.

It's strictly to stay clear of spray in seaplanes, or because the engine was tacked on as an afterthought for some reason (like a motorglider conversion) and that was the only place to put it.
There aren't any aerodynamic benefits, or you would see the configuration on landplanes.
You've increased the frontal area by having a big pod sticking out.  The high thrust line wants to pitch the airplane over, increasing tail trimming forces required to compensate, and hence drag. There there are the undesirable handling qualities, mainly a strong pitch down tendency when you add power quickly, and worse, a pitch up tendency when you remove power quickly, which can get the unawares into quite a lot of trouble.
So to summarize, sticking an engine there is only done when there's nowhere else to put it.


Why are the angle-of-attack sensors on most airplanes mounted on the forward fuselage rather than at the wing roots? A source of reliable angle-of-attack information is important for airplanes, as flight at an excessively-high angle of attack can cause the airplane to stall, which is generally considered to be an undesirable occurrence.  To this end, airplanes generally have several redundant angle-of-attack sensors (usually consisting of vanes that stick out into, and align themselves with, the airflow, but sometimes using complicated pressure-sensing mechanisms instead) to provide warning of a dangerously-high angle of attack.

These sensors, however, are generally mounted on the forward fuselage, below the cockpit, which is not, for most airplanes, where high angles of attack actually cause problems.  Where AoA matters is on the wings, which produce the lion’s share of the airplane’s lift and which need to be kept from stalling, and where the direction of the local airflow is not necessarily the same as that experienced by the AoA sensors on the forward fuselage.  Exactly how not-same it is depends (as do quite a lot of an airplane’s aerodynamic properties) on the airplane’s airspeed, which is why readings from nose-mounted attack-angle sensors need to be adjusted to correct for the effects of airspeed, which is why (for instance) high-attack-angle protection on fly-by-wire Airbusses is inoperative in the absence of valid airspeed data.

Mounting the angle-of-attack sensors at the airplane’s wing roots, rather than beneath the cockpit, would allow the AoA to be measured directly right where it counts, eliminating the need to correct their readings for airspeed and allowing accurate attack-angle measurement even without any airspeed information at all, so why do most airplanes still have their attack-angle sensors on the forward fuselage instead of the wing roots?

Would installing the AOA vane (or, in general, sensor) at the wing root be more accurate than installing it near the nose? No, it wouldn't. In fact, it may be slightly worse due to the larger upwash at the wing leading edge and the vane protrusion may even negatively interfere with the wing aerodynamics.

Traditionally, AOA measurements are used for stall warning and, if required, stick pusher. During flight tests, the thresholds for stall warning activation (and stick pusher activation) were calibrated to the local AOA measurements from the vanes to satisfy the certification requirements, while minimizing $V_S$/$V_{SR}$ to maximize performance.

In FBW aircraft, if the control laws have AOA dependency, the control law would typically be designed with aircraft AOA (a.k.a free-stream AOA) as specified in wind tunnel and/or CFD. Therefore, the local AOA measurements would need to be corrected to the aircraft AOA before being consumed by the control laws. Answer to this question outlines the methods for such correction during flight test.

Addendum:

There are a number of other AOA measurement devices besides vane and Smart Probe (used on A220 and E170, E190). The most common ones are leading edge orifices or tabs used on GA aircraft (thanks @JanHudec for pointing out). These operate by sensing the movement of the stagnation point as AOA increases. The downside, of course, is that the stagnation point associated with the required margin to stall is different at varying Mach numbers and across high lift configurations.

This NACA report contains a number of wing-mounted stall warning devices tested in the last century.


Why have cargo hybrid airships not succeeded in the market? Using a Lighter Than Air (LTA) Hybrid Airship to efficiently transport cargo to remote areas seems like an idea that should flourish.  It allows access to remote places in the world that have no airports, harbors, or roads leading to them by providing a point-to-point delivery system with vertical take-off and landing, all while providing a greener solution.  I see at least three players all trying to enter this market which seems perpetually stuck as coming about in the next 4-5 years and all seem to have benefited from the U.S. Army's Long Endurance Multi-intelligence Vehicle (LEMV) project that was canceled in January 2013.

Hybrid Air Vehicles in the U.K. has partnered with Northrop Grumman owns a prototype that came out of the LEMV project and plans to build a 50-ton capacity airship in about five years.
Aeroscraft in the U.S. has a prototype and plans to build an airship that carries a 66-ton load as shown on the History channel.
Lockheed Martin has a P-791 / SkyTug prototype derived from the LEMV program and hopes to build a SkyFreighter to lift a 70-ton cargo.

It appears none of these companies has any current orders and are all looking for funding to build their proposed cargo airships.  Apparently an investment of on the order of 50 to 250 million USD would allow one of these to be built for commercial use.  While this is a lot of money, it is small compared to other aviation investments. For example, the Boeing 787 Dreamliner required 32 billion USD as of 2011.

Today, all such airships use noble gas helium instead of the very flammable hydrogen used in the Hindenburg accident, so the historical fear of using such ships should not apply to the new technologies.  These proposed ships are planned to travel at between 70 and 115 MPH, so while not as fast as airplanes, they do compete with trucking and shipping speeds.

So the question is, given the relatively small cost to develop one of these cargo lift systems, why hasn't a company like Boeing with deep pockets wanted to invest in such systems and these companies continue to search for funding?  Is there some kind of flaw in the proposal that such a new cargo shipping approach would save money?  Is it that the market is too small to interest big companies? The hangar space required to store and maintain these ships is huge and little such infrastructure currently exists, perhaps that is their downfall?  Alternatively, maybe their maintenance requirements are their Achilles heel?

First of all, there is the question of demand. There aren't enough cases where a very heavy load needs to be moved to a remote location by air. There are probably even fewer where there are funds to actually pay for this option. The An-225 is currently the largest aircraft in operation, and it was only constructed under special circumstances. Although has certainly found use, they still haven't even found the funds to finish a second one which is partially built.

When this option is needed today, helicopters are deployed on cargo aircraft to the area. The helicopters may have to make multiple trips but can do the job. So the subset of cases is even smaller; where heavy cargo needs to be delivered to a remote area and also cannot be split into shipments that helicopters can handle. Deploying a large airship in this manner is also much harder. Either the airship would have to fly itself there, which could take a long time, or it would have to be reduced to a transportable size.

The airship would also need to be protected from the weather somehow. This could require either a very large (and expensive) hangar. Without a hangar, the airship must be tethered, and restraining such a large surface area in the wind would be difficult.

Wind would also affect operation of the airship. Helicopters are of course limited by weather conditions, but wind would have a much greater effect on a large and slow airship.

If the airship could be fairly easily collapsible, it would solve the issues of storage and transportation. However, this is not a simple problem to solve. This would require a large development budget. If you are comparing this to the cost of the 787 development, where are you going to find buyers for 1000 of these airships in order to break even and make them affordable?

The issue is that there needs to be a market for this kind of transportation, which currently competes at least partially with existing helicopters. Why invest in a new type of vehicle when the current option works fine for most cases?


Which type of jet leaves black trail at cruising altitude? I was recently travelling to Morocco, and as I was sitting by the window, at some point mid-flight I noticed another jet travelling in opposite direction at our altitude. The reason I noticed it easily, was that it was leaving very dark, solid, nearly close to black colour trail. It definitely was at cruising altitude, as after that we were still flying for about 1.5 hours before landing. I just can guess that it was small-ish jet, as height of its body appeared nearly the same as diameter of the trail. I couldn't see much details any way, as it was about a mile from us.

Does the black trail indicates fuel inefficiency of an engine, and that could be on of the old military jets?

That could easily be a military jet, or it could be an older type passenger jet. The old jet engines had inefficient fuel injectors and simply used a lot of them, creating a higher fuel-to-air ratio which results in black smoke from carbonised fuel. There is only a short time to mix the fuel with the air under pressure in the combustion chamber, and modern day engines pre-mix the fuel with air before injecting.

Olden days jet engines also used water injection in times of high demanded thrust, creating more black smoke due to a cooler combustion chamber, but since the aircraft you saw was in cruise it would not be in a water injection flight phase.

So any older type of jet engine could have caused the black smoke you saw. Could have been an old DC-9 or even a B-52 :)


What is this on the starboard engine of the Dash 8? On the inside of the starboard engine of the Bombardier Dash 8 Q400 there is a small aerofoil shaped object* protruding from the casing. There also appears to be pipes protruding from the end of it.

Can anyone identify what this is and explain its function?

** Probably not an aerofoil just looks vaguely like one.

It is the engine drain mast. From the Dash 8 Series 400 airport planning document - Chapter 2, Page 40:

Dash 8 engine drain; image from Dash 8 Series 400 airport planning document

Basically, the drain mast houses the drains that allow for the removal of the fluids (oil and fuel) that come out of the engine, due to seepage, leaks etc. For example, this incident report is a case where it was,

  ... observed ... fuel dripping from RH engine drain mast.


What is the CPIOM in the IMA? What is the CPIOM in the IMA architecture. Which is the difference between the CPIOM in the A380 and the CPIOM in the B777?

In the IMA architecture, processing modules are hosted in a cabinet and are interconnected via a high speed bus. B777 uses "SAFEBUS" which is ARINC 659 on the backplane and ARINC 629 externally (same protocol, different physical layer). Airbus uses ARINC 664 internally and externally for the bus. Legacy bus interfaces go through an I/O module or other bus conversion interface.

The Airbus IMA contains 7 CPIOM (Core Processing & I/O Modules) that support both processing capability and I/O interfaces on a single module. It also includes one I/O Module (IOM) connected to the ARINC 664 bus for additional I/O.

The B777 AIMS cabinet contains Core Processing Modules (CPM) and separate I/O Modules (IOM).

The same functions exist in both, it's just that the Airbus CPIOM is a single module where B777 has two modules for the equivalent functionality.

And in a similar vein, the B787 IMA contains "GPMs" or General Processing Modules. It also contains two ARINC 664 network switches (network I/O for the cabinet). There are no direct legacy connections to the GPMs. Legacy (ARINC 429, CAN, discrete, analog) buses are connected to the external ARINC 664 network using Remote Data Concentrators (RDC).


Why manufacturers does not producing variable sweep wing in our current scenario? I read about many types of aircraft wing configurations like rectangular, swept forward, swept backword, and Delta wing. These configurations have their own advantages and disadvantages. But why we don't have variable sweep wing so that we can gain the advantages and better efficiency.

This was, as you are likely aware, the swing-wing was a major design element in the 1960s. Everything from the F-111 to the B-1 to the 2707 used them.

The design does have the advantages claimed for it, notably the better performance over a wider performance envelope. But the weight was a killer - not directly (although that may be the case in the 2707) but in relative terms.

Invariably what happened was that other parts of the system were improving too, engines, avionics, etc. At some point the performance improvement of the swing-wing required more weight than the same improvement from a new engine.

So it's not simply that it was too heavy, but too heavy compared to other moving goalposts.


Can a nonresident American citizen get a Canadian helicopter license? Is there anything preventing a non-resident American citizen from taking and obtaining a Canadian helicopter pilot license which could be converted to an American PPL helicopter certificate?

The reason I'm considering this is the current exchange rate is essentially a 25% discount off the listed Canadian price. Sure I have to drive a bit farther, but auto gas is cheap.

In the US it is a license as well, that's why they abbreviate it PPL and CPL.

Canada appears to have no restrictions on flight training of non-Canadians other than proving your own with something like a passport, because your citizenship is shown on your license. See this Transport Canada page as a starting point.

If you need to reside in Canada during your training and you expect to take longer than 6 months, you will need to obtain a Student Visa to remain in the country legally.  You could also use a Tourist Visa, neither of which would all you to work.

If you are planning on returning to the US when you are not training, then the Visa would not be required.

Converting a Canadian pilot license to a US pilot license is governed by AC 61.135a.. It doesn't look very complicated, but it will take time and you must take one or more knowledge tests as well as schedule an appointment at your local FSDO for the final approval.

Note also that while you don't have to surrender your Canadian license when you convert to a US license, if you do not that means that you must stay current based on both the US and Canadian rules.

I suggest you very carefully study the requirements and do the full math. Once you get started on one path it won't be easy to switch to the other if you then realize it was a mistake.

Interesting question, BTW. It was fun researching the answer. :)


Why is the aircraft boneyard in Tucson, Arizona still active? I understand that an aircraft boneyard is an amazing tourist attraction for aviation enthusiasts.

However, the number of planes that the boneyard in Tucson has accumulated today is mind-boggling. I know that, initially, the purpose of the boneyard was to salvage materials from old and obsolete aircraft. However, the pace at which most aircraft are being scrapped is very low. Though it serves as a spectacular sight, why is the boneyard still active?

If the number of planes waiting on getting gutted isn't decreasing even though scrapping activities are happening that means there is a steady influx of end-of-life planes arriving to get scrapped.

As long as there are planes and new planes being built (most have a lifespan of a few decades) there will be planes that need to get scrapped.

You can't just dump the plane on a landfill or you will get nature activists on your case about the hazardous materials (hydraulic fluid, remnant fuel, ...) and recycle potential. Plus most components (instruments, engines, the espresso machine in the galley, etc) will still be usable and airliners will want to buy them as spares.


Is it legal to make emergency landing on roads? Recently I've seen many videos of planes landing on car road. Is this legal? Does this only apply to only USA or even other countries?

In the USA, when an airplane is in the air, it is governed by Title 14 of the Code of Federal Regulations, also known as the Federal Aviation Regulations (FARs). FAR 91.3(b) gives the pilot in command authorization to deviate from any flight rule necessary to meet an emergency: if that pilot needs to land on a road to meet an emergency, it is certainly legal as far as the FAA is concerned.

In fact, for private flights in small airplanes, the FAA doesn't bother much at all about specifying where you choose to land. There are no regulations about it at all.

The FAA's authority to regulate stops when the gear touches the ground, though. The road, or field, or waterway, or whatever you might be landing on usually belongs to someone or some government entity. Government entities often have laws against landing aircraft in certain places like roads or waterways, but just as often, they don't. It depends on which government. But in all cases I have ever seen, if such a regulation exists, so does an exception that starts, "except in cases of emergency...."


How to calculate angular velocity and radius of a turn? How can I calculate with known tangents of different angles and by rules of thumb?

Which formulae should I use for fps and NM?

Your terminology is a little confusing, but I'm going to assume you're asking how to calculate turn radius and rate of turn based on airspeed and bank angle. These formulas can all be found in the FAA's Pilot's Handbook of Aeronautical Knowledge which is available for free online.
The Handbook gives the formulas for rate of turn and turning radius on page 4-34:
$$R=\frac{V^2}{11.26\tan\theta}$$
$$\omega=\frac{1,091\tan\theta}{V}$$
The variables used are:

$V$ = true airspeed in knots
$R$ = turning radius in feet
$\theta$ = bank angle in degrees
$\omega$ = rate of turn in degrees per second

For example, at 120 knots and a 30° bank angle, the turn radius and rate of turn are:
$$R=\frac{120^2}{11.26\tan30}=\frac{14,400}{11.26\times0.5773}=2,215 feet\approx\frac13nautical~mile$$
$$\omega=\frac{1,091\tan30}{120}=\frac{1,091\times0.5773}{120}=5.25°/sec$$
The "magic constants" in these formulas ($11.26$ and $1,091$) are conversion factors for the units involved (knots, feet, and degrees). Physicists would use unitless formulas involving $g$, acceleration due to gravity (roughly $9.8m/sec^2$).
You can also rearrange the formulas above using simple algebra to figure out the required bank angle given a desired rate of turn or turn radius.
Finally, note that things get a lot more complicated if you factor in winds aloft. Rate of turn will always be the same regardless of wind, but turning radius no longer applies because the aircraft will trace a spiral path along the ground, not a circle. The turn will be "sharper" on the upwind portion of the turn and "wider" on the downwind portion. This is why turns around a point is a complex maneuver taught in basic flight training: in order to fly a circular ground track, the pilot must constantly vary the aircraft's bank angle according to wind: lower bank angle upwind, higher bank angle downwind. The pilot must also use the rudder correctly to keep the turn coordinated at all times.
Other useful links:

Pilot's Handbook of Aeronautical Knowledge (quoted above)
Aviation Formulary has a section on turns
Standard rate turn article on Wikipedia
Banked turn article on Wikipedia

There are also some "Related Questions" over on the right-hand side of this page that might be useful.


When can a tower's callsign differ from the airfield name, and how do I find the proper callsign? It seems like a lot of air traffic control towers use callsigns that are much different from the name of the airfield.  For example, Lehigh Valley International (ABE) has "Allentown Tower."

"Allentown Tower" doesn't appear anywhere I can see on the sectional chart.  (The control frequencies tab even lists it as "Lehigh Valley Intl.")  You might be able to figure it out through other hints, such as the presence of the "Allentown Class C," but that doesn't seem like something that can be relied upon in general.

I doubt pilots are expected to have airport diagrams handy for every airfield in the vicinity just for this.

If, say, I had to divert to an unfamiliar airfield, how would I find the proper callsign for its tower?

I doubt pilots are expected to have airport diagrams handy for every airfield in the vicinity just for this.

And you're wrong to doubt that.

  If, say, I had to divert to an unfamiliar airfield, how would I find the proper callsign for its tower?

From the chart. Same place you'd get the tower frequency...


Why do pilots sample the fuel before a flight? I was reading this checkup writeup and it says the pilot took fuel samples before the flight. So I Googled and found out, there are several fuel samplers/testers available.

Now I am wondering: Why is this necessary? Is it a mandatory procedure or do you just do this if you don't trust the supplier?

I can also imagine, that you check for water or contamination. However, we never do that with our cars.

Or am I completely off track?

On the first flight of the day, after every refueling, and if you have flown through precipitation or the plane is left in the rain, you check the fuel for water and to make sure you have the right kind of fuel. Since water is heavier than fuel, if there is just a little bit of water in the fuel it could cause the engine to stop. You can’t pull over to the side of the road like you can in a car, so you need to immediately deal with the problem. The most likely place for this to occur is on takeoff. If you think fast and switch tanks, you might get lucky and only have water in one tank so you can continue your takeoff. If not, you may need to find a place to land.

In 17 years of flying, I have only found water in the fuel once, and it wasn’t even my airplane. But since it was on Catalina Island, a stopped engine would not have been pretty.

The other reason to check the fuel is that airplanes designed for 100LL do not burn Jet Fuel. Jet fuel is denser than 100LL so it will sink to the bottom of the tank. It is straw colored and somewhat greasy, so you can tell if your plane has accidentally been filled with it, but you really have to be paying attention. It would be easy to miss if you just topped off. There have been incidents when twin-engine planes have mistakenly been filled with Jet A and have either crashed or required expensive fuel system cleaning. Mike Busch's article describes his experiences. After the misfueling of a Cessna 421s, someone did a test to see how easy it is to identify a combination of Jet A and Avgas. It’s fairly hard using standard pre-flight practices. That’s why many people recommend watching the fuel truck if you have a twin-engine plane or one that prominently says “Turbo” on the side.

Many aircraft have rubber bladders to hold the fuel. Most older Cessnas  have them. Water can get trapped in the folds of the bladder and get into the engine later when the fuel is sloshed around.

Even if the fuel source is free of water, a tank that is not full can have water condense in it.

Most autogas has some ethanol in it. Water will dissolve in a gas-ethanol mixture and so a slug of water won’t get into the engine like it will in an aircraft engine.

Contamination is less of an issue and is one that is really hard for a GA pilot to determine. You really can’t tell if the fuel is contaminated with other petroleum products just by looking at it.


What if a aerobatic fighter pilot sneezes in middle of a maneuver? No offense to any pilots, I am a student, curious.

I just watched Spy (2015) and I was just wondering what happens if one of the pilot accidentally sneezes during a difficult maneuver.

Jude Law misfires during a critical stand-off.

I mean what are the preventive measures taken to avoid this - the jet is obviously primed to be in best of its agility & stick-sensitiveness so can the pilots selectively decrease sensitivity of stick when needed?

Evolution has created this wonderful thing called stress. We tend to think of stress as something negative that is to be avoided, and that is certainly true: prolonged periods of stress will do all sorts of damage to your body and mind.

However, for short periods of time, stress is a wonderful invention that lets us survive situations we otherwise wouldn't: when we come under stress, when that sabre-tooth tiger pops out from behind the bushes, our autonomous systems produce anti-inflammatory agents, dampen our pain reception, flood our system with performance enhancing drugs, improve our perception, shorten our reflexes, increase our energy levels … and, yes, also repress our sneeze and cough reflexes.

Have you ever had the experience that, after a long period of stress, just when you were finally looking forward to some well-deserved vacation, you get sick at the most inopportune time, right at the beginning of your vacation? Well, actually, you didn't get sick, you were sick all along, but during the stress period, your body suppressed the symptoms, and as soon as the stress goes away, the illness, wich may have been brewing for days or even weeks, breaks out in full.

So, to answer your question:

  What if a aerobatic fighter pilot sneezes in middle of a maneuver?

He doesn't. Stress will prevent him from doing so.


What special airspace exemptions are granted for civilian fighter jets? How do civilian fighter jet operations arrange airspace usage for conducting flight tours? Do they use military operation areas? If they fly into class A can they perform maneuvers, or do they need to stay below class A? One such operation is migflug.
When flying in airliners cross country I look out the window and think what it would be like to experience flying around and between cumulonimbus clouds in a jet fighter, but doubt ATC would allow it. It got me to wondering how the civilian jet tours handle airspace and speed restrictions.

The same regulations apply to civilian ex-military aircraft as they apply to any other aircraft. Whether flying IFR or VFR, you will need to comply with the same rules, e.g. speed restrictions, airspace restrictions when under VFR, meteorological conditions, etc.

An exception can be speed restrictions, where a speed restriction would be in contradiction with the parameters of the aircraft to perform safe flight, e.g. the minimum clean speed being above 250kts or similar.


Do Cargo flights carry anyone other than the crew? This question talks a bit about the crews that are involved in a commercial cargo flight, but I'm wondering if Cargo flights every carry other sorts of people on their flights?  Say, a photographer to take pictures of operations for advertising or something.  Or maybe one of the crews kids who want's to see what Mom does or something like that.  Or, perhaps there's even another person who's normally there?

If they do, here's a couple bonus questions:

Do they have jump seats?  And are they in the cockpit, or in the cargo hold?  (Just in general, I assume different planes have different setups).
Are there any regulations regarding this?

Yes, cargo aircraft are like other aircraft in that there is generally at least a jump seat available. Especially larger aircraft will also have additional jump seats, a lavatory, and a galley. This area can be used for relief crew, or other crew that are just deadheading.

There are exceptions though. The upper deck of the 747 is larger than just the cockpit, even on the cargo versions. There is more room in the back for additional crew. The An-124 and An-225 also have additional space for crew behind the cockpit. The extra crew can be loadmasters, navigators, mechanics, or other functions that can make it easier to operate in and out of airports with less services available.

Here is the upper deck of a 747-400F:


Is it possible for one runway to have a different TORA in each direction? Is it possible that TORA is not the same for both directions on a single runway?

Yes.  If you look at the information for London Gatwick as an example, 08R has a TORA of 3159 meters, whereas 26L has a TORA of 3255 meters.

http://www.ead.eurocontrol.int/eadbasic/pamslight-7B4054FA19E6240FA6A62C9356F52804/7FE5QZZF3FXUS/EN/AIP/AD/EG_AD_2_EGKK_en_2018-12-06.pdf


What are these "portholes & panels" on the fuselage of the Omega Tanker DC-10? If you take a look at the photo (source: still from this YouTube video), you'll notice a pair of "panels" on the fuselage of this Omega Tanker DC-10 (reg: N974VV), circled with green.

There is also a pair of "portholes" (circled red).

What are all those? Any relation to this being a tanker?

Note: Here's a photo that shows the "panels" closed on the ground.

The things circled in red are static ports. They are used to measure static air pressure. You can see a close up (from a different aircraft) here:

(taken from this answer)
What you circled in green is an outflow valve used for controlling the pressurization. See also:

What is this device below the door of a 737 (and other aircraft)?
How does the outflow valve work on a cabin pressurization system?
How does a DC-10 flight engineer manually raise the cabin altitude?

It is technically called a Thrust Recovery Outflow Valve:

The actual nomenclature is the "Thrust Recovery Outflow Valve"
[...]
The thrust recovery outflow valve is essentially the valve that controls cabin altitude throughout the isobaric selection range. It can be controlled electrically through 2 electric motors receiving input from the automatic and semi-automatic cabin pressure controller/computer. On the -10's with Flight Engineers, the clutches could be disengaged via a handle at the FE station, and the valve was then controlled through a manual wheel.

(Airliners.net)
Both items are unrelated to the fact that this is a tanker. The following image shows the same items on a Northwest Airlines DC-10-40:

(Airliners.net)


How long does it take to refuel a Cessna Citation X+? Does anyone have any sources that can tell the the number of fueling nozzles and the fueling rate for a Cessna Citation X+ or a Cessna Citation X?

Basically fuelling time depends on how fast the hydrant or fuel truck can deliver fuel.
This comes from SmartCockpit:

The  Citation  X  fuel  system  is  comprised  of  the  storage,
distribution,  refueling/defueling,and  indicating  systems.    The
storage  system  is  made  up  of  a  set  of  integral  tanks  in
each wing,  and  a  center  wing  tank  which  includes  a  forward
fairing  fuel  tank.    Each  wing  tank  has  a hopper  tank  which
is  integral  to  it.    The  two  wing  tanks  incorporate  check
valves  and  baffles allowing  each  wing  tank  complex  to  function
as  a  single  tank.    Other  integral  components  of the  storage
system  are  the  gravity  fuel  fillers,  drain  valves,  flapper
check  valves,  vent  system                      components,
positive/negative   pressure   relief   valves   and   all   of   the
associated   system plumbing.    Transfer  capability  is
incorporated  enabling  all  usable  fuel  to  be  available  to
either engine.Each  wing  tank  holds  a  total  of  521  gallons
(3518  Lbs.)  of  fuel,  which  includes  the  hopper tank.    The
center  wing  tank  holds  888  gallons  (5594  Lbs.),  207  (1397
Lbs.)  of  which  are contained  in  the  forward  fairing  tank.
Total  fuel  capacity  of  the  airplane  fuel  system  is
1927 gallons; at 6.75 pounds per gallon the available fuel weight is
13,031 pounds.
SINGLE-POINT REFUELING DEFUELING SYSTEM
The  single-point  refueling  system  is  provided  to  enable  the
airplane  to  be  refueled  or    de-fueled  more  safely  and
conveniently  by  connecting  to  one  port,  which  is  not  open  to
the atmosphere.      Advantages   of   a   single-point   refueling
and   defueling   include   minimized refuel/defuel   time,   reduced
possibilities   of   fuel   contamination,   reduced   static
electricity hazard, less airplane skin damage, and there is no
personnel contact with the fuel.The  refueling/defueling  system  is
independent  of  the  airplane  system.    It  is  designed  for
refueling  with  a  truck  or  refueling  hydrant  (pit)  having
single  point  provisions.    The  major components  of  the  system
include  the  refueling/defueling  adapter  (receptacle),  the
precheck control  panel,  refuel  shutoff  valves,  the  pilot
(precheck)  valves,  defuel  valves,  a  sequencing valve,   manual
defuel   select   shutoff   valves,   internal   drain   valves   and
associated   system plumbing.Single-point  refueling  is  accomplished
by  connecting  the  refueling  truck  or  refueling  pit equipment
to  the  airplane  at  the  single-point  refuel/defuel  adapter  on
the  right  side  of  the fuselage just forward of the wing leading
edge.


Ground Turning Radius Regardless of any legal regulations, is there a standard technique for designing the ground turning radius of an aircraft, or is that typically just a fallout parameter?

Some things to consider:

Don't make it a potential weak point on the aircraft. This was/is a big problem with some of the Mooneys out there where the nose gear can be damaged if a very tight turn is made while towing:

  One other caution: Many Mooneys suffer damage to the nose gear trunion
  when towing turn limits are exceeded via power towing. Owners learn to
  watch the ramp rats carefully.

Make sure you can maneuver the aircraft around the desired airfields. If you are building an aircraft that is intended to operate out of small GA fields with tight taxiways and short runways, keeping turning ability tight is key. If you are designing an airliner, make sure you can get around major airports (taxi diagrams are readily available). You don't want turning radius to be a limiting factor when buying/selling an aircraft.
To caster or not to caster, there are plenty of aircraft out there with castering nose wheels steered with differential breaking only this might have an impact on radius but a benefit in simplicity of design that is for you to decide.


Are there any hypersonic planes in service today? Are there any hypersonic (Mach 5+) planes in service or officially being built? Or all the talk I here about the SR-72 rumor. Thanks!

As far as supersonic commercial flight goes, Nope. The Concorde and the Tupolev Tu-144 are both long retired.
As pointed out in the comments, hypersonic commercial flight has never existed.
The SR-72 you speak of is supposed to be flying by 2025.
This article points out that

Only a few experimental planes have ever reached hypersonic speed, and the last time a hypersonic plane flew with a person on board was in 1967. That plane, the North American X-15, was powered by rocket engines, which are impractical for commercial air travel.

The same article mentions a potential 'in-development' aircraft:

The Stratofly consortium plans to begin wind tunnel tests of the engine components. But it will take many years to bring Stratofly to life. The key technologies might not be ready until 2035, Viola says, with another decade needed before flight tests are completed and the plane is ready to carry passengers.


Why was this commercial jet accompanied by small plane near Seattle? From the South Beach Campground on the western shore of the Olympic Peninsula in Washington State we observed this unusual formation:

I only had a Sony RX100 at hand but perhaps the image quality is sufficient to recognize the airplanes.

The picture was taken on July 23rd, at 20.20h PDT (the image timestamp is 6 minutes off), looking roughly NNW. I don't dare guess the altitude, but to the bare eye the small airplane was a mere dot. The two planes flew in formation in a circular counter-clockwise pattern around the north-eastern part of the Olympic Peninsula. They re-appeared two or three (I think three) times. They appeared to fly at low speed.

We realized that we were only approximately 150 km west of Seattle, the Boeing headquarters. Was this a test flight? Which planes are involved? What is the function of the small accompanying jet?

It's a Fedex 777F N894FD in (probably) pre-delivery aerial photography/test flight accompanied by one of Boeing's chase aircraft.

After some maneuvers (shown below), the plane headed to MEM, Fedex's "SuperHub".

(Source)

The flight on flightradar24: https://www.flightradar24.com/2019-07-24/03:16/12x/FDX9032/2168b4b1 and flightaware: https://flightaware.com/live/flight/FDX9032/history/20190724/0215Z/KPAE/KMEM


Why are some aircraft's life limited by both cycles and flight hours? For instance the Pilatus PC-12 life is either 27,000 cycles or 30,000 flight hours, whichever comes first.

I understand that the limit life in cycles is mainly due to fatigue in terms of pressurization/depressurization, but what about the maximum flight hours?

Imagine a world where the aircraft would fly only one flight of 30,000 flight hours, then there would be only one pressurization cycle, and one takeoff, so what limits the aircraft to fly more than 30,000 FH?

Some fatigue related issues that are not directly tied to departures and arrivals, like wing bending from gust loads, but may be randomly continuous throughout the flight, need an hour limit.  Taking it to a comical extreme, if the airplane flew for 3 years straight without ever landing because it had a new pixie dust powered engine, it would have close to 26000+ hours of bending fatigue time on the wings and tail, engine mounts etc., but only one flight cycle.

Also, there will be an analysis that establishes the average amount of time per flight cycle, overall across the fleet, and this may be applied in some cases to give an hours life limit that is roughly equivalent to the target number of cycles, when applied in the aggregate.  That ratio of hours/cycles suggests that the average flight time per cycle for the PC-12 is somewhere around 1.1 hours.  In the Regional Jet world, the average flight cycle is about 1.3 hours.  The 30000 hour limit prevents a PC-12 operator who does a lot of long range flying with 2 hour+ trips from running his airframe up to 50000 hours before it gets to 27000 cycles.

30000 does't sound like a lot, but corporate aircraft generally live fairly pampered low-utilization lives and take quite a long time to get those hours, perhaps 30 to 40 years.  A regional jet gets to 30k in only 10 years.


What's that component between the engine and wing? It's on most commercial aircraft and large aircraft with turbofan engines... Is there a specific name for it? Does it serve any other functions apart from attaching to the wing and feeding the engine the essentials? Has there been any aviation incidents that involved something malfunctioning or breaking inside of it? Or some other interesting things about it? Just out of curiosity! Thanks! :)

It's a hard-point called an "engine pylon".

And yes, some designs use specific points designed to fail if there is excessive force, allowing the engine to separate from the aircraft without ripping the entire wing apart which would obviously be a catastrophic event. It has happened on a few occasions.

The above image is from the Wikipedia page on the American Airlines 191 accident, where, due to a faulty maintenance practice of using forklifts for removing and reattaching the engine/pylon assembly, the aft bolts were damaged. The pylon eventually failed, allowing the engine and pylon to push up and over, separating from the wing.

Other examples include China Airlines 258 and El Al 1862.


Why are there non-standard altitude callouts? I just saw a YouTube video with an A340 landing. There were the regular altitude callouts (1000, 500, etc.) until the callout "110". I was quite puzzled by this.

What are the conditions that the automatic callout would call "one hundred and ten" instead of one hundred?

Parenthetically, I'm almost certain - though I can't recall the details right now - that I've also heard a callout "seventy" in some other video, possibly with another plane type.

From the same channel and also an A340 at 4:26 in this video the standard '100' can be heard.

The reason is a built-in timeout, if a certain time elapses between callouts—say due to non-standard [shallower] descent rate, perhaps due to high headwind for example—the current height is called out. In other words, you get to hear a callout at regular intervals.

From an A340 manual, here is the bit about the intermediate callouts:

Just a bit of history: one of the early TAWS systems (Mk II I believe) had a rising tone instead of the 100, 50, etc., you can watch it here.

Note on terminology: those callouts are heights (radio), not altitudes (barometric).


Is starting a jet engine without ground support possible? We have had more... than... one question about jet aircraft taxiing about the airport without their jet engines running. Those address several issues such as cost vs savings and regulatory approval.

My question assumes that an in-wheel electric motor, tug or even pull-chain based solution has been developed, certified, deemed cost-effective and installed.

Let's say that I am now sitting on the taxi-way and am 5th in line for take off. It's time to fire up those jets so they can warm up and we can get the beast into the air. According to this question about how turbine engines are started, it appears that I'm going to need some sort of ground-based support to get the N2 stage spinning. That question indicates that a couple of early, WWII era, jet engines had a built in motor that could get the turbines spinning fast enough for a start, but it seems to me that any modern commercial air-carrier grade engine will need some sort of external help to fire up. I suppose if there was a tug that had pulled me to this point, it could have the support infrastructure built in to get the turbines spinning, but any sort of self- (or ground-) propelled system would seem to lack that.

Now that we're nowhere near the terminal, how the heck are we going to start the engines?

I realize that this question is somewhat speculative in nature, but I believe it could be answered based on some existing or in-development ability (that I'm not aware of) to start an engine without ground support. It could also be my misunderstanding that ground support is not required to start a modern commercial aircraft engine (GE90, RR Trent series, LEAP etc.)

Modern jet transport category aircraft have APUs and they will be running if no engines are.  Batteries on jets do not work very long with all electrical buses energized and the first thing you do after turning the batteries on is seeing that they are working correctly and then starting the APU (assuming no GPU is hooked up, if there is a GPU then starting the APU will be deferred until just before the GPU is disconnected).

Thus, any aircraft on a theoretical no-engine taxi to the runway will have a running APU providing electricity to run the airplane and bleed air for an attempt at air conditioning (some aircraft are better at this then others).  When it is time to start the engines they can be started using the APU as the bleed air source and this is a normal method of starting and no different than the method used currently when the plane leaves the gate (and for some airplanes they only start one engine and taxi on that as long as possible before starting the other engine).

As long as the plane has a running APU, it can complete a normal engine start with no ground assistance.  The only limitation will be turbine warm up time, which just means you'll need to make sure the engines are started a few minutes before takeoff thrust is applied.

Just an aside, but currently the only ground support strictly required is a tug to push the airplane away from the gate and someone to operate the jetbridge.  Aircraft and engine startup is self-contained unless the APU is inoperative.


Do flight schools typically have dress codes or expectations? I attend a local flight school for lessons once or twice a month. I normally wear a hoody and some tracksuit bottoms as they are comfortable for me and I like to be comfortable whilst doing something that I need to apply focus to (I dress similarly for my job as a developer).

Most people that are there for lessons are dressed very smartly, usually in a shirt and tie. I presume this is because they want to impress people, as they are attending the airport they hope to work at in the future (it's a big airport). I am just doing this for a hobby, but the fellow students often look me up and down, usually looking confused and/or disapproving.

Do flight schools typically or traditionally have more formal dress codes or expectations than this? Are there substantive reasons for why certain clothing choices would be required or expected?

If you are learning to fly as a hobby and are paying the school your painfully earned money, you can dress however the hell you want, within reason.  Formal attire in that circumstance is ridiculous.  If you are in a professional school in some airline related program, or a government subsidized school with a formal dress code, that's another story, and you follow the rules as they are.

Anyway, the problem with hoodies and track pants is really loose clothing and hoods can be a problem in a cramped cockpit and especially if trying to get out in a hurry on the ground.

A cotton or wool shirt without a hood and good pockets, and cotton or wool cargo pants (cargo pant pockets are really handy) is my favourite dress for flying.  Avoid "plastic" synthetic fabrics.  Having fibres made from plastic, your clothes will melt into your skin if things get "hot".

Same with shoes.  Wear shoes that will let you walk at least some distance on a rough surface.  You may find yourself walking a mile over rough terrain after a forced landing.

Dress for comfort and contingencies, without getting carried away (like buying a nomex flight suit) in other words.


How many stripes does a student pilot have? When a student is finishing a Bachelor in Sc. Aviation, how many stripes does a student have? Can a student have stripes during his bachelor graduation or do they have to go through other PPL courses?

Stripes don't have any standardized meaning in between companies. If a company wanted, it could give one stripe to its most senior captains and four stripes to the office dog.

If your employer or your school has issued you a uniform, then the number of stripes that you have is the number of stripes that they decided to put on that uniform. If you haven't been issued a uniform, then you don't have any stripes.


What is the relationship between the design lift coefficient and the section lift coefficient of a NACA5 airfoil? I would like to know the relationship between the design lift coefficient Cli, of a 5-digit NACA airfoil, with the expression Cli = 0.15*L according to Wikipedia. And the section lift coefficient of an airfoil.
I was doing a CFD project and was planning to compute the section lift coefficient of different airfoils, and comparing them to the L (1st digit of a 5-digit NACA airfoil) of the specific airfoil, but I don't know which is the relationship between the 2 values.

The design lift coefficient determines the camber line of the airfoil. It is chosen such that the flow hits the airfoil exactly parallel to the start of the camber line when at the design lift coefficient. For a NACA 23015 this would be a lift coefficient of 0.15 x 2 = 0.3. The index i only denotes that this was held to be the ideal lift coefficient.
At this ideal lift coefficient the highest local curvature of the airfoil contour is right at the stagnation point and the pressure distribution downstream from there is smooth without the suction peaks which occur when the high curvature of the leading edge has to be negotiated by the upper (higher lift coefficient) or lower (smaller lift coefficient) side flow.


Are Dreamliner windscreens periodically replaced irrespective of damage? Does Boeing have a statute that commands that the windscreens are changed for new irrespective of no signs of damage or fatigue, and if so, what are the intervals, for safety reasons?

First, Boeing does not provide any statues for when maintenance is performed. They provide guidelines and recommendations through the Maintenance Planning Data (MPD) manual that most airlines follow. Some of these recommendations are required to be performed by the FAA with the certification of the aircraft or later AD action.

That said, there are no recommended maintenance tasks for the 787 windshields. The reasons is windshields are certified to be able to to hold cabin pressurization even with every pane shattered. Although there is no recommended or required task to replace the windshields at a set interval, some airlines may choose to do so for operational reasons.

Mandatory part replacements based on flight hours or cycles is almost exclusively reserved for a special classification of hardware known as "Safe Life Parts" these are generally just the Landing Gear and Engine Rotors. These are required to be scraped at specific intervals due their failure mechanisms and because they can be single point catastrophic failures.

I have specifically reviewed whether or not hard time replacement of 737/757/767 and 777 windshields made sense at a very large airline. The data showed that windshield failure rates when plotted against either cycles or hours had very large standard deviations. This means it is very hard to set an appropriate hard time interval, if you set it too early you would have few failures in the field but you replaced a lot of windows that had a ton of life left on them, if you set it too late you still had many field failures and were still throwing away good windows. When doing a Wiebull analysis I was able to identify at least 8 different failure mechanisms that all had very different rates and only affected a small population of windshields. To highlight the point, we had multiple windshields that failed after less than 100 flight hours while we had many that lasted more than 60,000 flight hours (and a few that were up to 80,000 that had never been replaced).


What is this airport video? I was in a car dealership waiting room and saw this video of an airport that was slowly scrolling down the screen (like River Raid).

The video is in motion - the cars on the street are moving and the 2 planes on the left were taxiing. The scrolling is very smooth - as if it's a satellite or maybe blimp.

Is this real video or just CGI? What airport is it?

How did they get the video while it was obviously in use? Wouldn't the airspace above the airport be restricted?

Specifically, the video is one of the Apple TV's screensaver images, taken at LAX (this one in particular [WARNING: high-def video link, ~267MB] [alternate YouTube version, thanks to Mark]).

It's not CGI. Apple used a variety of drones and helicopters to shoot the footage.

While the airspace around the airport is generally controlled (not restricted), there are a number of VFR flight routes that cross the airport. These can be seen on the Los Angeles Terminal Area Chart. In the case of this specific video, permission was presumably coordinated with ATC. As the video was taken down the middle of the airport, between the sets of runways, it's likely that taking it didn't interfere with air traffic; traffic arriving/departing LAX won't be flying there.

This tweet (with photos) just crossed my feed. @ethanklapper: Today was special. Chartered a helicopter and flew above LAX at 2,500 feet. Took 500 pictures in an hour. Can’t wait to share more!

I imagine a similar process was used for this video.


Why wasn't Avro Arrow program revived ever? When Canadians realized that it was a mistake to abandon their jet fighter program, why didn't they revive it?

Why wasn't Avro Arrow program revived ever?

Since I'm not and was never a member of the Canadian Parliament or Canadian military top brass, this is pure speculation as you are likely to get from practically anyone else on this site with the possible exception of Rhino Driver (who is AFAICT a serving U.S. naval aviator).
My guess is that the Canadians looked to their south, saw one of their nation's staunchest allies who also happened to be one of the two remaining superpowers after World War II, and concluded that they couldn't afford to compete in the Cold War arms race but could definitely afford to profit from our R&D. Canada and the U.S. formed NORAD in 1958 as a joint venture to defend North American airspace, so Canada knew the U.S. had its back. Canada, for its part, spent its defense dollars outfitting defensive SAM and ICBM-intercept fortifications along probable Soviet nuclear bomber routes, effectively forming the northern part of the North American nuclear shield.
As far as not reviving Avro Canada now, the biggest answer is that Canada is so far behind the major powers in domestic aerospace technology that it would essentially have to recruit in the U.S. military-industrial complex anyway. In addition, compared to the USAF, the RCAF is tiny, composed mainly of transports to move the Army around, with just 70-odd CF-18 fighters making up the total fixed-wing combat complement, and a handful of ASW helicopters seeing service at naval stations and on the Canadian Navy's dozen Halifax-class frigates. In short, Canada has no real need for a domestic military aerospace program, as demand is very low and it can get all it wants from its southern neighbor at preferential prices. They're in line, IIRC, for a shipment of F-35s once Lockheed gets the bugs worked out.
EDIT FROM COMMENT: The comment says that Canada could build planes primarily for export. Such an effort would be doomed to fail for three reasons:

The RCAF itself, given its small size and its outstanding relations with the U.S., would be unlikely to buy the planes. When looking for export buyers, your best marketing is the success of your design in your home country's military, so not having your military use the design at all is a big black mark (the F-5 is the only fighter I can think of that managed decent export success despite the U.S. never widely adopting it; even then, the USAF did have some test deployments of F-5 squadrons in Vietnam for the primary purpose of giving Northrop their backing to market the plane for export).
This presents a Catch-22 for financing and R&D efforts; you're unlikely to get the funds to start working on a plane without any acknowledged demand for it, and with the Canadian aerospace industry being dormant for over almost 60 years, you're unlikely to generate demand for an as-yet nonexistent fighter from an unproven design team. So you have to get the money to build the fighter, and you have to build the fighter to get the money.

Again, the Canadian aerospace industry is dormant, and therefore way behind the times. A joint venture with U.S. or European firms to provide a knowledge transfer to home-grown aerospace engineers seems like the only option to develop something new, when those same firms would then have to openly compete with the resulting firm and its designs. A new Canadian aerospace company would be reduced, as I said, to sniping U.S. talent to jump-start design work.

Some countries that formerly imported jets are starting to look toward domestic production, making a primary export strategy that much more unappealing. Pakistan is the foremost example; their political relationship with practically all the major exporting countries is pretty shaky, and designs still in production for export are getting really expensive, so they're designing the J-17 jointly with China to have an inexpensive, capable fighter they can build in-house without relying long-term on imports. The resulting fighter (an interesting combination of design features from the F-16, F-18, and European designs like the Gripen and Rafale), on paper, is about 40 years behind the times, comparable to Gen-4 and 4.5 fighters like the F-15, F-16, MiG-29, Su-27, Typhoon and Rafale. But, the J-17 is projected to have a flyaway cost of only about \$15 milion a plane, which is a bargain compared to the aforementioned export choices, which start at about \$40 mil per plane and go up to \$110 mil.


What are the differences between the MiG 31 and MiG 25 (if any)? What are the differences between the MiG 31 and MiG 25, they look exactly the same, their overall performance the same. Is it the roles they were built for are different?

The MiG-31 is an all new design with higher strength for low-level flight and new engines. The reason it looks just like the MiG-25 has to do with the structure of the Soviet aviation industry. The basic shape is first defined by the Central Aerodynamic and Hydrodynamic Institute (TsAGI is the abbreviation of its Russian name) and then given to the design bureaus which do the mechanical design. Production is then relegated to dedicated manufacturers which build the designs of different bureaus in parallel.

Both aircraft were designed as interceptors. The main difference is the advanced radar, digital data links and the more powerful engines of the MiG-31 which made a longer fuselage necessary. The MiG-25 radar, a development from the 1960s, could only detect high-flying targets, while the Zaslon radar of the MiG-31 can also detect and track low flying aircraft (look-down/shoot-down capability); a necessity after NATO changed its strategy to nap-of-the-earth flying to avoid detection.

If you need to tell both apart on pictures, look for these features:

While the main landing gear of the MiG-25 has a large, single wheel, the main gear of the MiG-31 uses two smaller wheels in a staggered arrangement.

MiG-31 main landing gear (picture by Burkhard Domke source)

While most MiG-25 were single seaters, the MiG-31 has two occupants, a pilot and a weapon systems officer behind him. Two-seater versions of the MiG-25 can be easily distinguished because the two cockpits are separate units, the front cockpit replacing the radar.

MiG-31 on the ground with canopies open (picture source)

The wing root of the MiG-31 has a small strake added while the wing of the MiG-25 is a pure trapeze with a straight leading edge. The picture below shows the MiG-25 in black lines and the MiG-31 overlaid in red.


Does my PPL need to be checked again when I move to another country? If I acquire my PPL in one country and move to another one, is there any procedure to evaluate that PPL and get it in another country?

Did anyone have an experience with that? I'm interested in general rules, if any, and to know what would happen when moving from EU to USA or USA to EU, in particular.

Also, what about renting an airplane in another country? Would someone need to reevaluate my license?

You have to take your logbook and your license to civil aviation of that country and then they will request a confirmation from the country that you have got your license from to be sure that if your license is still valid. After confirmation you have to join any ATO and undergo flight and ground training on the plane category that you have your licensee on (You might not need it but they must are the one who ask for an examiner for you and you can't apply by yourself) and then you must do the oral exam and also a flight test on your single engine type.Remember for converting any license, only your flight hours will be accepted and some of your exams and not your ppl flight test.In some countries you must also do 4 exams which mostly are Nav,Met,Hp,and Law but in some other countries can be only Law . It is depend to the rules of the country that you are willing to get you license new from .For us to EU you must only do the ppl law exam. All this Rules applied for a valid ppl license .Good Luck


Did B-17 gunners beat on the wings of other planes in their formation? I am certain my father, a B-17 pilot, told stories about his gunner having to beat on the wing of another plane in the formation with the tip of his gun to get the pilot to pull away and avoid a mid-air collision. Anyone have a similar story? Do you know which gunner?

That'd be a roughly 1 meter stick you've got to beat that other aircraft with, at most. Not a long stick at all.

By the time the other aircraft got that close a collision would be unavoidable. Not only would momentum carry them closer, but the banging would likely not even be heard by the crew of the other aircraft.

Remember they'd be wearing headphones, not just for the intercom but even more important for hearing protection. A B-17 is a LOUD aircraft when you're flying it.

Also, by the time you'd get that close the crews of both aircraft would have been screaming at their respective pilots for some time to ask them what the hell they're thinking getting that close to another aircraft.


Could the Cruise-Efficient STOL configuration be as efficient as a conventional airliner? The Cruise-Efficient Short Take Off and Landing (CESTOL) is a NASA project.  There is a video here:

The configuration is a conventional fuselage at the very front of the aircraft with enormous thick section leading edge extensions.  The wings outside the LEX appear to have similar aspect ratio to a 737 or A320.  The aft fuselage is flattened and there is a v-tail.  The engines are buried in the wings in a fashion similar to the Gloster Meteor aircraft.

How much less or more efficient would this configuration be compared to a conventional tube and wing configuration for a 737/A320 size aircraft given similar engines and materials?

Without data, it is not possible to tell if one design will be better than another. This is because it is one thing to make a concept (which this is) and entirely another thing to manufacture and operate the aircraft (like A320/737).

Actually, the design in the video is not entirely new, It is similiar to the Boeing YC 14

developed for UASF AMST program. It is instructive to note what happened in that program.

The AMST program was initiated for developing a tactical STOL aircraft, requirements similar to the CESTOL. Even though YC 14 met the requirements, the program was scrapped for other reasons and the C17 was developed from another contender in AMST program, the YC15.

Even during development fo the YC14, the drag was more than expected and Boeing struggled to bring it under control.

However, I doubt the design as shown is ever going to be made into an actual aircraft. There are too many problems at first glance

The wing seems to pass right through the fuselage. This is not going to work in a transport aircraft.
The location of the engines suggest that the main spar will pass right through it. This will have strength implications.
In case the aircraft is used for STOL operations, the rear fuselage design should be redesigned for preventing tail strike as the landing gear in all probability will be shorter.
Putting the engine inside wing is not a great idea as it increases complexity and chances of catastrophic wing failure.

There are a number of similar programs for developing efficient STOL aircraft, none of which have come into fruition. It is going to to be the economics of the operation from small airports, rather than the aircraft itself, which will decide if these designs will ever see the light of day, let alone operate in commercial routes.


Why is the IRST not centered on the Eurofighter Typhoon? Following links included in this answer, I noticed the IRST is located on the left side of the Eurofighter Typhoon. It seems that this asymmetrical location is common (Dassault Rafale, MIG 29,...).

Why is the location of this device chosen so that on side seems privileged? I see no reason to prefer one side over the other, there should be the same chance for a target to be located on one side or on the other.

The Thales UK PIRATE IRST system is located here in order to allocate space on the starboard nose for the retractable in flight refueling probe.  The port space was the only available real estate for this avionics to fit.  Other aircraft like the MiG-29 have similar restrictions in space availability.

The asymmetric location does not affect functionality; the IRST seeker head does maintain full field of view without blockage from the nose or fuselage.