What is the fastest airplane? There are many airplanes that claim to be the fastest piston, private jet, airliner, but what is the all time fastest airplane? How fast does it travel?

This is a broad question. The Wikipedia page on vehicle speed records gives a nice breakdown by various categories. Some criteria are manned vs. unmanned, air-breathing vs. rocket, civilian vs. military.

The fastest manned, air-breathing aircraft was the Lockheed SR-71 Blackbird with an (unclassified) record of 2,193.2 mph on July 28, 1976.

However, some would consider the rocket-powered North American X-15 the fastest manned aircraft at 4,510 mph.

If you consider the Space Shuttle an "aircraft" during its re-entry phase, it passed Entry Interface at around 17,500 mph. This was unpowered flight though, and its speed dropped off as it entered the atmosphere.

I believe the rocket-boosted HTV-2 Falcon currently qualifies as the fastest unmanned aircraft at 13,201 mph.

The record for the fastest human-made craft of any kind is currently held by the Helios probes, at 157,078 mph. The fastest manned human-made craft was the Apollo 10 spacecraft at 24,790 mph. (Note that Apollo 10 holds the record not because it was any more or less capable than any other Apollo mission, but that its chosen moon fly-by trajectory resulted in a higher top speed relative to Earth. It could also have achieved a much higher top speed on a different trajectory had that been a goal for mission planners, but it wasn't.)

Finally, every single one of these is either military or NASA (not civilian). The fastest civilian, air-breathing aircraft were the Tupolev Tu-144 supersonic transport at 1,518 mph, and its Western counterpart, the legendary Aérospatiale-BAC Concorde, at 1,488 mph. Both are now retired. Several private organizations are developing civilian suborbital and orbital rocket-powered spacecraft; I'm not sure which is currently fastest.

And though these aren't crafts or vehicles, honorable mentions go to a 150,000 mph steel plate launched by a nuclear weapon, and to particle accelerators for propelling subatomic particles and "man-made" particle collision byproducts at ridiculously close to (99.99something percent of) the speed of light :-)


How does a CFI know what endorsements to give? I am trying to figure out how a CFI knows what endorsements to give. Obviously AC 61-65E lays them out but what if someone is coming from a unique situation? Let's say someone has a helicopter license and wants to get their private pilot? Do they have to take a knowledge test? What if someone is a sports pilot and wants to upgrade to a private pilot, what do they have to do? How do you figure it out?

In general, a flight instructor must demonstrate sufficient knowledge so as to be able to provide the proper endorsements for his students. This is covered both in AC 61-65 and in the Flight Instructor Practical Test Standards Task M:

  Task M: Logbook Entries and Certificate Endorsements

  References: 14 CFR part 61, AC 61-65.

  Objective: To determine that the applicant exhibits instructional
  knowledge of the elements related to logbook entries
  and certificate endorsements by describing:

  Required logbook entries for instruction given.
  Required student pilot certificate endorsements, including
  appropriate logbook entries.
  Preparation of a recommendation for a pilot practical test,
  including appropriate logbook entry for:
  a. Initial pilot certification.
  b. Additional pilot certification.
  c. Additional aircraft qualification.
  Required endorsement of a pilot logbook for the satisfactory
  completion of the required FAA flight review.
  Required flight instructor records.

Regarding the question:

  Let's say someone has a helicopter license and wants to get their private pilot? Do they have to take a knowledge test?

According to 61.63:

  § 61.63 Additional aircraft ratings (other than for ratings at the airline transport pilot certification level).

  (b) Additional aircraft category rating. A person who applies to add a category rating to a pilot certificate:

  (4) Need not take an additional knowledge test, provided the applicant holds an airplane, rotorcraft, powered-lift, weight-shift-control aircraft, powered parachute, or airship rating at that pilot certificate level.

So a private pilot looking to add an additional category rating at the same certificate level need not take the aeronautical test.

Regarding the question:

  What if someone is a sports pilot and wants to upgrade to a private pilot, what do they have to do?

you can find the answer in part 61.103:

  Subpart E—Private Pilots

  §61.103   Eligibility requirements: General.

  To be eligible for a private pilot certificate, a person must:

  (e) Pass the required knowledge test on the aeronautical knowledge areas listed in §61.105(b) of this part.

  (j) Hold a U.S. student pilot certificate, sport pilot certificate, or recreational pilot certificate.

So a sport pilot upgrading his certificate to private pilot must take the private pilot test.


What is the fundamental physics behind L/D decreasing as AoA increases beyond the optimal point? Why does lift over drag decrease with AoA past the optimum AoA?  Is it because the backwards vector for a given lift force on the wing is now larger for a given air particle compared to lower AoA?

For a single air particle interacting with the wing at higher vs lower AoA does the higher AoA cause a larger change in the velocity of the air particle?

Are there other factors involved?

The fundamental reason is that at high enough AoA, the lift becomes zero -- certainly no later than an AoA of 90°! At that point L/D is zero (there'll be lots of drag). So somewhere between 0° and 90° there will be an AoA with the highest L/D, and that is by definition the optimum AoA. Slightly beyond that angle there's nothing for the L/D to do except decrease, because if it didn't, the angle we're beyond wouldn't be the optimum.

Now if you were asking why that particular angle is optimal for a given airfoil, we would have to go into aerodynamics and boundary layers and whatnot. It's not merely about what happens to the molecules that (try to) hit the underside of the wing, but at least as much about how well the molecules above the wing can be convinced not to hit it.

Note that above the optimal AoA, until the critical (stall) angle, the lift generated still increases with increasing AoA -- it's just that in this range drag increases faster than the lift does.


Is there a Cockpit Video Recorder? Often we hear about Cockpit Voice Recorders, but are there video recorders?

They're presently not in use.

The accident investigators don't generally clamor for them, since there are very few questions that they can't answer with FDR and CVR readouts, where a CIR would provide useful information.  The voices proposing them as a great idea tend to come from elsewhere -- from those who think they'd be a cool idea, but who don't fully understand the capabilities investigators already have.

Pilots are, understandably, averse to the idea -- working where your every word is recorded every minute of every day isn't thrilling, but the protections for CVR recordings are pretty strong, since only transcripts (not the actual audio itself), and transcripts edited down to relevant portions only, are all that can be released, and those only in case of accidents (at least in the USA).

Video isn't nearly so easily transcribed as audio, and any such description of moving images opens up far more possibility of subjective or dramatic interpretation of what's shown, and ample opportunity for YouTube "experts" to craft alternate - if wildly implausible - narratives. The idea of a public outcry, or an aggressive lawyer, demanding the release of the full video of a crew's last minutes, or hours, opens up the unsettling possibility that families may see a loved one's final moments in far more detail than simply transcribed words on a page.

And let's be honest, in a full day at work, who doesn't have moments that, edited down to a few out-of-context three-second clips, wouldn't paint a poor - if utterly inaccurate - picture of who you are and how you work?

Until and unless actual accident investigators build a persuasive case for the need for such technology in our cockpits, such devices are likely to remain in the realm of the hypothetical.  There is simply no evidence that they would do anything to make aviation any safer.


How far ahead does an airline know which aircraft you will be flying on? My favorite features of the United Airlines app are:

you are able to see what specific aircraft will be operating your flight
you are able to trace that aircraft back indefinitely via the "Where is this aircraft coming from?" button

I noticed that each aircraft has a specific number aside from the aircraft model (e.g Boeing 737-900 #3815), that references which specific aircraft will be operating your flight.

My question is how far ahead does an airline plan which specific aircraft will be operating a flight?

I'm not asking if the airline knows that a B737 model will be operating a flight, but I'm asking more specifically how far ahead do they know which specific aircraft in the fleet will be operating a particular flight?

This question may be broad as I realize that it may differ between airlines. I'm just curious as I like to see where my flights have been and will go, I find this very interesting.

It depends on the airline and their planning capacity. The simple answer is that they can't be sure of the tail number "of record" for a flight until the plane pulls into the gate at its destination. It's rare for a plane that departs the gate for a flight to not run that flight (it's pretty bad business for it to be common for flights to depart the gate and then come right back, or to be diverted, or otherwise not finish the route they left the gate to fly); it indicates a mechanical issue exists that did not develop and/or was not discovered until taxi or takeoff, and at some point in the flight (probably when departure control hands them off the the ARTCC) the plane could be said to have "run" the flight even if it ended up diverted.

Most of the equipment schedules (which tail number will fly which route at exactly what departure and arrival times) are generated by computer and can be set up months in advance if they really wanted to. However, that's usually an exercise in futility along the lines of predicting the weather more than a few days ahead. Airline scheduling, like weather, is susceptible to "chaos theory", because small deviations from the initial plan tend to compound over time instead of factoring out.

Ticket sales, rebooks and cancellations will affect the schedule days and weeks in advance of the flight. It's technically illegal to cancel a flight less than a certain number of days before its scheduled departure if it has even a single paying customer on the roster, but if a route is underperforming, the scheduler can reduce the scheduled daily flights along that route which could bump people who bought a ticket far in advance. Also, an underbooked flight can legally be cancelled if the plane is needed for an equipment change on a fuller flight, as cancelling the underbooked flight would cause less overall disruption than cancelling the full flight because that plane can't make its next hop.

I just mentioned mechanicals; that's a big reality check for a computer-generated schedule. If a plane cannot continue because of a mechanical defect, it gets pulled for maintenance. Airlines typically have a few planes parked strategically on the tarmac of various airports for a day, which can be activated to run a route, but they don't have too many of these since a parked aircraft isn't making money, and there isn't always one of these standby aircraft readily available as a substitute (though if a defect is found in flight the replacement can be on the way before the defective one lands to reduce the delay). Meanwhile, mechanicals are typically such a localized problem that the schedulers can't get away with just delaying flights systemwide, like they can often do with severe weather. They have to run the rest of their fleet on time, and that means either getting a replacement plane to the gate, pronto, or else sending that replacement plane empty to the cancelled flight's next destination, so the new plane can get those passengers on to their destination.

Obviously, severe weather can cause major ripples through an airline's schedule for days to come. If ORD or DFW has a "ground stop" due to severe precipitation or high winds, that will delay not only the flights scheduled to arrive or depart in that time, but every flight those tail numbers were scheduled to run for the rest of the day, as well as various scheduled connectors (those connecting flights, if they're not also under severe weather, often have to depart with whatever passengers they have otherwise there will be even more delays; then the passengers who have missed that connectot will have to be rebooked, on other airlines if need be).

That delay time also counts as "active" time for a flight crew; if a flight is delayed beyond a crew's end of shift, they often must get off the plane to comply with FAA regs and union CBAs. The scheduled replacement crew, however, was supposed to get on at the next stop hundreds of miles away; so, it's not just the planes that have to be replaced on a route when a flight is cancelled. In cases of a severe delay extending beyond a normal shift change, the crew either flies the plane if it's legal and are paid overtime, or if it would be illegal for that crew to continue, an on-call crew is brought in, flies the plane to the scheduled changeover point, then rides a standby seat (or in the extreme an empty plane) back to their home terminal or somewhere else they'll be useful when their shift really starts.

All of these considerations and more are weighed by the sophisticated algorithms now used to generate flight schedules. American Airlines calls theirs the "cancellator", and when a major hub like DFW, ORD or ATL sees a weather shutdown that's pretty much exactly what it does, sacrificing flights to and from that hub and some of its connectors to try to save what it can of its passenger load for the day (and thus the airline's profitability for the quarter).


If both pilots are incapacitated, what happens? How do the airlines prepare for a situation where for some reason both PIC and SIC are incapacitated for the remainder of the flight?

How does Airbus prepare for a dual engine failure on the A320?

The short answer is this isn't something that's realistically planned for because the chance of a double-failure of the redundant systems in question (the two pilots) is pretty unlikely, and many of the conditions that could lead to it would result in a catastrophic loss of the aircraft anyway.

(The most notable exception to that would be a loss of pressurization at altitude, in which case hopefully at least one of the pilots can get their oxygen mask on to make the emergency descent.)

The ATC/Airline system as a whole can theoretically deal with this sort of a double failure in a few different ways. The most common is finding an off-duty employee of the airline who is riding non-revenue (dead-head, jumpseat, etc.) to fill the role of an incapacitated crew member.
This is of course predicated on whatever incapacitated the flight crew not affecting this other person.

If no qualified personnel are available it may be possible to get an experienced instructor on the radio to "talk the plane down", but that relies on having someone onboard who can (a) get access to the cockpit, and (b) at least figure out how to operate the radios to ask for help.
"Talk-Down Landings" have happened in small aircraft on several occasions, but as best I can determine this has never happened in a transport-category aircraft (airliner) outside of simulations and similar thought experiments.


What, exactly, happens when I call 1-800-WXBRIEF? In the USA, calling the above phone number gets a pilot in contact with a flight service station (FSS). After reading the AIM and the Leidos Flight Service website, I still have some questions:

Where exactly are flight service stations, and which one does the phone number connect me to?
Is the person on the phone a meteorologist?

If not, how do they provide weather briefings?

Will someone answer 24/7 or do different stations have different hours?

Does this also apply to the FSS frequencies listed on VFR charts?

There is a list of Flight Service Stations in the US Chart Supplement.
The person on the phone is not a meteorologist and does not need to be. Though, just like pilots, they have been trained to be proficient on weather and weather related knowledge.
They provide the weather the same way a pilot can self-brief the weather. They utilize distributed briefings, Area Forecast Discussions, Prog Charts, other tools supplied to them by the NOAA, WPC, NWS, and AWC. Primary though, they use METARs, TAFs, PIREPs, and Winds Aloft reports at your airports of planned use and along your route of flight.
Someone will answer 24/7. Though, the person answering may not be from the closest FSS. It will be routed to the first available representative.
The same goes for inflight contact over VHF radio frequencies,


What does the XFR button on the Challenger 300's autopilot panel do? I'm new to aircraft and currently I'm learning the autopilot system of the Bombardier Challenger 300. I saw the "xfr" button but don't understand what it is for. Can someone explain this to me?

You can find manuals for many aircraft including the Challenger 300 at Smartcockpit. The Automatic Flight Control System section includes the function of the XFR button.

There are two flight guidance computer cards that drive the autopilot, including the flight director and yaw damper. The XFR button switches how the computers are used.

For most of the flight, only one computer is use and provides output to both left and right cockpit displays. Pilots will get warnings if this computer fails, and they can push the XFR button to switch to the other one. Without a failure, pushing the XFR button switches so that each side of the cockpit gets input from a different computer.

Precision approach and go-around modes are the exception where by default each side of the cockpit is driven by a different computer.


Does landing in extreme weather conditions require any different or special training? Is there any special training, relating to land under extreme weather, such as snow storms, contaminated runways or ice conditions?

In some regards there is but this depends on what you consider extreme weather.

On one hand there are physical limits to which a plane can be landed when it comes to wind both head on and cross winds. Granted they are cases they may never or only rarely come up you may simply not be able to land the plane.

Assuming you have made it to the airport and are able to land...

There are some check lists and different procedures that me be executed for different weather. Snow and wet runways in general may see a longer landing distance and roll out however this is not "special" training as landing distance should always be calculated based on conditions.

Approaches are flown as published but changing winds and weather may cause the pilot to react differently or do different things to fly the approach. For example if you compare a calm wind approach to a dry runway with a wind sheared approach to a wet runway you may see some differences. The pilot may elect to come in a few knots over Vref and possibly with less flaps in a wind shear situation. Again this is not special training as much as it is standard.

On a contaminated runway the pilot may chose to preform something like a short field landing so as not to potentially collapse the nose gear. All pilots (even GA) are trained in this maneuver. There are so many possible situations here it would be hard to train for ever one but some are trained for or a checklist exits.

Side Story: I was talking to a commercial pilot recently who flies the 777 and he was telling me a story of a time during training in the sim where they gave them heavy rain and 40Kts of wind shear (no one could successfully land the plane that day in his group in the sim). So they do at least throw situations like that at pilots in the sim, if they do it all the time I cant say.


Can you flag down / contact an airplane with a handheld radio in case of emergency? A friend and I are going rim to rim to rim in the Grand Canyon this Wednesday.  It's a 46mi, 20+hr "hike" with some very physically challenging sections.  We are packing the minimal amount needed - meaning not too much extra in case of an emergency - it's especially risky given the below zero (fahrenheit) temperatures this time of year.  Normally for something like this, I would bring my Spot - to call for help if I needed to, but it's not working.

If I brought my VXA-220, would it be legal to use it to call for help?  From what I understand, most airliners are tuned into 121.5.  Could I tell them to send a helicopter for rescue?

Obviously, in a life or death situation it's not going to matter if I'm braking the law.  But it would be nice to know how such a situation would be handled.

Yes, this is legal. As far as I understand, it used to be common practice, and some hiker's beacons still squawk 121.5. Nowadays, more advanced beacons are suggested, but it sounds like yours isn't working. Some police and EMT stations still monitor 121.5, too.


Is King Khalid International Airport in Riyadh actually very big? Apologies in advance if this is in the wrong place, there isn't a geography StackExchange so this was the next best option I could find.

I've read multiple things about the huge size of King Khalid Internaional Airport (IATA: RUH, ICAO: OERK) in Riyadh, one source said it was bigger than Paris and others have said it's larger than the entire country of Bahrain.

Judging from Google Maps, it really isn't particularly big. What's the deal with that?

It depends how you define the airport. I don't think your Google Maps method is sound, however; it depicts built-up areas, not the airport boundary. You couldn't draw the same map around LAX, say.

The standard for measuring the area of an airport appears to be the total land owned by the airport. And jet age airports, with their expansive noise buffers and office park reservations, tend to take as much as they can get. DEN is reckoned the largest airport in the U.S., at 33,531 acres (~136 km²), though only a fraction of this is developed.

The numbers for total land are easy to find, the numbers for improved land less so, but I found an informative Globe and Mail article about Montreal-Mirabel. When originally created, the land seized for the airport was larger than the city of Montreal itself— around 97,000 acres (~392.5 km²). The article notes that the airport perimeter itself was only about 5,200 acres (~21 km²). Still, it's the former number that is commonly bandied about, and the measure by which Mirabel was considered the largest airport in the world.

According to Kable, a London-based business information firm, King Khaled International Airport covered an area of 225 km² when it opened in 1983.

In 1999 it was surpassed by King Fahd International Airport, which occupies 776 km². This is roughly the figure given by the 2013 Guinness Book of World Records.


Where does the final cooling take place in the air cycle machine of the air conditioning system? On aircraft with an ACM air conditioning, where does the final cooling take place? Is it in the ACM expansion turbine or in the ACM compressor?

The final cooling will be at the turbine of the ACM.

(Source)

Air passes through two heat exchangers, before finally passing through the turbine of the ACM.

Related:

How hot would pressurized air get if the air conditioning failed?
Why is air mixed with bypass air on the A/C of an aircraft?


Why were early aviators' trousers flared at the thigh? For example, these dapper outfits:

(Credit History Bunker)

What purpose does the extra volume down to the knee serve? Why don't modern pilots wear similar jodhpurs?

It's not too hard to figure out.  Wikipedia says Jodhpurs originated from India where they were part fashion and part practicality (the loose fit in the upper half for horse riding comfort) and evolved into the uniform of most western cavalry officers by the turn of the century.

And, in WWI, where did most, or at least a lot, of the pilots come from in the early days?  Cavalry.


What would cause a non-zero indicated airspeed reading on the ground? What kind of failure would cause an indicated airspeed of say 200 knots on the ground (stationary)?

A mechanical blockage inside the airspeed gauge could prevent the needle from dropping all the way back to zero -- assuming the aircraft had exceeded 200 KIAS in the first place.
Whether this or the pitot-related failures in the @CamilleGoudeseune answer, the pitot-static unit, airspeed indicator, and altimeter (also connected to the static port) should be checked and repaired as needed by a qualified person.


How do aircraft brake when using skis? Planes use skis to land on ice/snow runaway.

How can the plane brake in such conditions?

Friction must be limited to allow takeoff and aerodynamic braking are not the main contributors to the deceleration on wheel landings.

Image source

You may find this manual of interest from the FAA. The short answer is that they don't have brakes like wheeled aircraft do. With sufficient runway you don't need brakes to stop a wheeled aircraft either. The airframe often provides enough drag to stop the airplane. You are generally correct that aerodynamics are not the primary method of braking, however they can in some cases be sufficient. On top of that ski operations are often flown from a frozen lake or similar area where there may be a great deal of unobstructed distance for takeoff and landing.

Some types of skis let the wheels poke through them for both snow and hard runways. In some cases the wheels may contact the ground beneath the snow and allow for traditional braking or they may be plowing through the snow providing drag.


Feasibility of converting long body carriers into stationary field hospitals Considering the current pandemic crisis, and the fact that and there are thousands of grounded planes that can be put to other uses, I come with a somewhat dumb question.

Is it possible to remove seats in a long-body passenger carrier to, instead of flying with two hundred cramped passengers, make it spacely enough to carry forty or fifty narrow beds and a small staff to take care of them, while stationary on the ground?

Is it feasible, from an economic viewpoint, to pay air companies for this, in comparison to actually building tents or renting buildings in a big town like New York or San Francisco?

EDIT

Yeah, I mean stationary planes, with external APU to power up the air conditioning and lights and rampies to take the waste away and constantly fill it with water.

This is a very opinion based question that will garner many opinion based answers. Not the type of type of fact based question that is the purpose of this site.

The pros of this concept would be:

Provide revenue for the airline.
Provide space for the ill.

The cons of this concept would be:

Aircraft get awfully hot or cold when not being powered.
There are no adequate facilities for long term waste and hygiene.
The air in an unpowered aircraft would be awfully stagnant. That is not good for the health of the recovering, nor that of the medical personnel.
If worse came to worse, there are a lot of unoccupied buildings that can be rented at the same or less cost than an airplane. They would already have the infrastructure for power and plumbing.
The Army and Army National Guard already have most of the tents and other housing facilities bought, paid for, and in storage for these types of emergencies.
Even for a pilot, timeframe for recovery, stuck in a fuselage, with that many other people would be claustrophobic. Think of how it feels if you are under a stay-at-home sequester order, now. Now, multiply that by ten.
Costly decontamination post-pandemic.
Running an engine or APU 24/7 would be cost prohibitive.
Having lived in a space with fifty other guys for an extended period of time, even with bunk beds, I can tell you that it would require more space than you might think. 1000 square feet (100 m^2) would be my estimate of the bare minimum without dining nor food preparation facilities, and minimal toileting facilities. That would be 20 square feet per person. That is less space than a king sized bed per couple for the entire living space.
Cruise ships and hotels would be a more feasible option.


How can I find our FAA airport designation number? Several years ago we were issued an airport designation number by the FAA. The information was lost when my father died. How do I find out what our designation number is?

What you're looking for is the FAA Airport/Facility Directory (A/FD). You can search it on the FAA A/FD Advanced search page. If your runway is registered as an airport with the FAA, its airport identifier will be in the A/FD. It will also include the runway numbers (there will be one for each end of the runway,) as well as other information about the runway (surface type, exact heading, altitude, etc.) See How are runways numbered? for more information on runway numbers. Another website available for searching A/FD information is airnav.com.

Another way to find information on the airport is to look at a Sectional Chart. For most private airports, an 'R' with a circle around it will appear where your runway is located and it will have the name of the airport beside it. You can then use that name to look it up in the A/FD. Skyvector.com is an easy way to look at sectional charts. It works a lot like Google Maps, except that it shows you the FAA sectional chart for your area rather than a normal map. You can just zoom in on your area to find the airport marker.

Your airport will look something like the one that I've circled in red on this sectional chart image:

If your runway has a hard surface (i.e. it's paved with asphalt or concrete) and is more than 1,500 feet long, it might look like the airport circled in the picture below rather than having the circled 'R'. In this picture, the purple circle indicates the airport and the white line within the circle indicates the location and orientation of the runway.


Why is Germany not able to read data from the Boeing 737 MAX black boxes? It is my understanding that Germany stated it does not have the capacity to read the new software, declining Ethiopia's request:

  "The French announcement resolved uncertainty over the fate of the two
  recorders after Germany’s BFU said it had declined a request to handle
  them because it could not process the new type of recorder used on the
  737 MAX jets, in service since 2017."

Does anyone know which requirements were missing?

This news article (in German) includes a mention that the black box was using newer software than the BFU has the capability to read out:

  Das Gerät habe eine neue Software, die an der BFU nicht ausgelesen
  werden könne.


Can the FAA allow a foreign training center to add a type rating to an FAA license? I have an ICAO license and an FAA one with the same type rating on both. I have done the initial training through the FAA in the US, but was able to validate the sim, training center and the DPE to get the type on my other ICAO license as well.

Now I wish to do the same, reversed - get an initial for a different type on my ICAO license and have the FAA validate it so I will have it on my FAA license as well.

Is that possible?

Training centers do not issue type ratings, examiners do. To validate foreign ratings in your FAA license you have to submit the request and supporting documentation to the FSDO closest to you. They will tell you if it is possible to add the rating to your license based on reciprocal agreements.


Are there known cases of an airline pilot's becoming incapacitated, while in command of the aircraft, during a critical flight phase? Are there any reported cases in which the Pilot Flying of an airliner has become incapacitated during a critical phase of flight, so that the Pilot Monitoring has had to intervene to prevent a disaster?

By critical phases of flight, I mean during takeoff, approach, or landing.

Here are a couple of examples from two studies that have a lot more detail and background information on pilot incapacitation in general.

From an ATSB study:

  After a normal touchdown, the first officer became unconscious at the
  flight controls and the aircraft began to veer to the right of the
  centreline. The captain took control of the aircraft to return to the
  centreline and completed the landing

From an FAA study:

  A 45-year-old B-737 first officer experiencing an alcohol withdrawal
  seizure suddenly screamed, extended his arms up rigidly, pushed full
  right rudder, and slumped over the yoke during an approach. The
  aircraft descended to 1,000 feet above ground level in an
  uncoordinated turn to 25 degrees angle of bank before flight
  attendants could pull the first officer off the controls, allowing the
  captain to recover the airplane


What do airliner manufacturers do with aircraft for which have no buyers? "White-tail airliners" refers to either airliners without any customer order (like the beginning of A300 production), or those where the order was cancelled after/during production and where no new purchaser has been found (like the Skymark A380 deal).

How do the manufacturers handle the white-tail airliners?

New airliners without a buyer will be handled on a case-by-case basis. Of course manufacturers prefer to not be in such a situation, and there is no standard system for handling this. However, there are some typical ways that this is handled.

One option it to store the aircraft at the manufacturing site. This is the same (and pretty much only) option that is used for aircraft without engines. This has the advantage of being easier to work in and deliver, but will of course take up valuable space.

To save space at the factory, the aircraft can be moved somewhere else. Storage areas already exist primarily for older aircraft being stored or scrapped, but new aircraft can go there as well. Boeing has done this with some 747-8 aircraft, as well as C-17's.

Of course the manufacturer has spent money assembling the aircraft, and it is costing money to have it sit somewhere, so they will be eager to cut their loss as much as possible. These aircraft will probably be offered at a significant discount compared to placing a new order. However, buyers may prefer to wait and receive an aircraft straight from the factory, rather than one that has been sitting in storage for a while. There may also be issues with customized options applied for an original buyer that would need to be refurbished or accepted by a new buyer. Looking for new buyers and rearranging deliveries is not unheard of and is part of the business of making aircraft.

It may be that no one is willing to buy an aircraft, or the aircraft would otherwise not be economical to put in service. The aircraft may in this case be sent to a museum, as with the RJX. In a similar case, the first three 787 aircraft were not deemed economical to put into commercial service after the test program, and were sent to museums.

The last resort would be to scrap the aircraft. This is certainly disappointing for a new aircraft, but in some cases it is the only option left to regain any value.


Are there any negative health indications from getting sea legs? I recently completed a long XC and upon completion I suffered a bit from sea legs. The XC was for the 250nm requirement for my instrument rating and was performed in a C172. It took about 3.5hrs
 to complete and there was a short ~30min pit stop a little before hr 3 of the flight. I was under the hood the entire time except for takeoff and landing. The air wasn't particularly smooth as
we were only @3-4k MSL and surface winds were in the teens.
I completed the flight in the early evening (~8pm) and feel like I suffered from sea legs, a small wobbly sensation of constantly moving, until I went to sleep (~11pm). I'm guessing the sensation would have lasted longer had I not gone to sleep. The sensation only occurred once on the ground and after completion of the XC. I don't recall having the sensation during the pit stop.

I'm curious how or if I should be concerned about this.  I do not suffer from in flight nausea, motion sickness or anything like that.

I have never had this happen on shorter, 1-2hr, training flights.  I've never had this happen when flying on a commercial jetliner.
I remember experiencing the same sea legs sensation on another long ~400+nm XC years ago. I flew a plane with an autopilot that rocked back and forth as it held the heading and I attributed the post flight sea legs to the oscillations of the autopilot.

Is this common for pilots to suffer from sea legs post flight? If it is common, how long does it last?
Is this an indication of a pending medical issue or an issue that might be of concern?
I'm curious if this is an indication of something of concern in my inner ear.
Are there any concerns with bringing this up with my AME? I have to get my medical renewed this year.

Key point --

  The sensation only occurred once on the ground and after completion of
  the XC.

  until I went to sleep (~11pm)

If you have no further symptoms or at least no more severe symptoms, then I see no reason to be too concerned about this, and certainly no reason to bring it up with an AME.  (But see added comment below re long-term career plans.)  Interestingly, after hours spent feeling certain repetitive sensations, whether due to to thermalling flight in a hang glider or sailplane, or bobbing up in down in a kayak, I have sometimes noticed a sense of the motion continuing later, but ONLY while laying down prior to falling asleep in the evening. These sensations may have been more related to the repetitive forces felt by the skeletal-musculature system (increased G-load, rhythmic variation in G-load), than to the vestibular-occular system, so perhaps they were fundamentally different from what you are describing.

Comment incorporated into answer--

  this is a medical condition called mal de debarquement syndrome or
  MdDS. Do a search on line, you will find literature on it. I developed
  a severe case after flying from Denmark to Los Angeles in a DC-7C in
  1960 which would flare up anytime I was in an enclosed space, like a
  clothes closet or stairwell. it did not subside until 10 years after
  that flight. – niels nielsen

A google search on that term produced other similar results of symptoms lasting many years-- remarkable.  Some rather interesting ideas may be found about just what is going on here, and how to treat it.  See for example https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5418223/

  We reasoned that if the notion of MdDS caused by maladaptation of the
  VOR holds true, a reversed VOR stimulus should mitigate or even cure
  the MdDS symptoms. Based on these findings, a treatment for MdDS was
  devised that consisted of rolling the head at the frequency of body
  rocking, while the subjects viewed a slowly moving visual surround.
  This postulate was tested in 24 MdDS patients employing cross-axis
  visual coupling (1). The results were promising: 75% of the MdDS
  patients had significant improvement in a 12-month observation, which
  was the first successful treatment of this debilitating illness.

(Front Neurol. 2017; 8: 175.
Published online 2017 May 5. doi: 10.3389/fneur.2017.00175
PMCID: PMC5418223
PMID: 28529496
Treatment of the Mal de Debarquement Syndrome: A 1-Year Follow-up
Mingjia Dai,1 Bernard Cohen,1 Catherine Cho,2,3 Susan Shin,1 and Sergei B. Yakushin1,*)

It would appear that there are enormous gradations in how severe this sort of thing can be.  If you are simply feeling some sensations on the ground, after a flight, and they are gone the next morning, it would seem both un-necessary and unwise to mention them to an AME.

I would say that occasionally-recurring symptoms at the level you've reported might be reason to think twice about a career as a professional pilot-- lest the symptoms get worse-- but still not something that would suddenly and significantly compromise your ability to fly safely on any given instance, and therefore not something that you should feel compelled to report to an AME.

Obviously I am speaking from the viewpoint of what is in your best interest as long as  it does not significantly conflict with safety.  An AME might well give a different opinion.


How do you determine the proper rate of descent for landing? I'm trying to use a simulator to learn to land properly.  One part that I'm finding really tricky is picking a proper rate of descent.  I know I'm supposed to do my best to keep it so I have two red lights and two white lights on the Precision Approach Path Indicator (PAPI), but at the moment I basically am just eyeballing it and adjusting my course whenever the lights aren't right.

I have to assume, though, that for any given airspeed there is a rate of descent I can maintain that will keep me right in the middle of the preferred glide slope for that airport.  I just have no idea how to figure it out.  Is there an application or formula that is preferred for this?  Or is it time to learn Vector Calculus?

PS- I did check this question to see if it related.  But that question is about starting the descent from cruise.  I'm talking about rate of descent for final. I did also check this answer, but it's about using the PAPI/VASI lights.  I'm looking for a formula to figure out the proper rate of descent during final for a given speed.

Assuming you want a 3 degree glide slope, just take 5 times your ground speed in knots as a starting point.

As an example, approaching at 90kt ground speed in a light aircraft, go for 450feet per minute. at 140kt in a jet, try 700fpm. If you're flying a jet outside of 4 miles, and the controller wants you to keep the speed up at 200kt then descend 1000fpm.

It's not perfect, but it works pretty well for a first guess, and you can adjust as necessary.

Of course, your ground speed is not the same as your air speed, and even for a constant IAS it will likely vary as you descend and the wind changes. Another way to think about this is that a 3 degree glideslope is almost exactly 300ft per nautical mile. If you're 2 miles out and 700 feet up, then you need to descend a bit faster, conversely, if you're at 500 feet, you need to descend slower.

A third related rule of thumb is that your final approach speed (in CAS, although IAS is good enough in most aircraft) is 1.3 times your stall speed in the landing configuration (Vso). So if you stall at 100 knots, you want to approach at 130KIAS.

IFR approaches are all about having an initial guess at these numbers in your head, trying them out, and then adjusting as the conditions require. If you're good at the guesses then the adjustments will be very small.


What is the expected time frame for FAA knowledge test results to show up in IACRA? I just passed my Part 107 Remote Pilot's knowledge test this morning, and I noticed that IACRA indicates it may take up to 48 hours for the test records to show up.  Does it always take 48 hours or is it sometimes faster than that?  What is the soonest that I might reasonably expect the test results to appear?

Bonus points if anyone knows why it takes so long, but I realize that may not be something anyone knows about (or can talk about).

I passed back in December 2016.  Took 3 days to get temp license and about 90 days to get my perm license.  Took me a week of study watching Youtube videos on weather and sectionals, in conjunction with UAS107 prep app (https://play.google.com/store/apps/details?id=uas107.openrobotix.labs&hl=en)


Can someone explain this glideslope question? The glideslope deviation bar is covering the second upper dot. The required action to meet glideslope beam is to:

What does this question mean?

If you are answering an FAA Knowledge Test question, the correct answer is to level off and intercept the glide slope.

While on the glide slope, pitch controls airspeed and power controls altitude, so you will need to add a bit of power. For small very small deviations caused by turbulence, just let the airspeed vary and use pitch for a short while. For larger deviations you won’t be able to capture the glide slope without adding power.

The amount of correction depends on how far away you are from the glide slope transmitter. Figure 139 from the Instrument Knowledge Test Supplement give you an idea of the amount of correction you need depending on how far away from the runway you are. So if you are near the outer marker, 2 dots would mean that you definitely need to add power, level off and intercept the glide slope. Near the runway 2 dots is less than 100' so a slight adjustment with pitch would be fine, presuming you were holding the glide slope until then.


Does Airbus provide pitch control correction symbols outside "normal law"? Do pitch control correction symbols exist in 'alternate law' and in 'direct law' mode (if planes angle of attack exceeds dangerously)?

You may be confusing the operation of the autopilot, the envelope protections and the flight director.

AIUI, the job of the flight director is to indicate the required roll angle and pitch to achieve a new compass heading and/or new altitude that the pilot has selected on the FD. If the AP is engaged, the FD will cause the AP to make the appropriate control movements, otherwise the pilot has to make the control inputs suggested on the FD display.

This has nothing to do with flight envelope protections AFAIK.

In Alternate Law the Flight Director can still be visible.

The BEA identified misuse of the FD as a possible factor in the loss of AF447

  as the flight control law switched from normal to alternate, the flight director’s crossbars disappeared. But they then reappeared several times. ... PF may have trusted the flight director so much that he was verbally agreeing to the other pilot’s pitch-down instructions, while still actually pitching up.

AIN online

  Disconnection of the flight director is normally part of the "unreliable airspeed" procedure. But after the A330 lost its airspeed information, and the autopilot and autothrust automatically disconnected, the crew left the flight directors engaged.

FlightGlobal


How are ADS-B surface position frames decoded? I am developing C# code that reads 1090ES Automatic Dependent Surveillance - Broadcast  (ADS-B).

The ADS-B position messages broadcast by the aircraft's ADS-B transmitter have a different encoding depending on whether the aircraft is airborne or on the ground.

When I decode Airborne Position frames as Compact Position Reporting (CPR) encoded positions, I get realistic results. However, when I decode the CPR for Surface Position frames, the positions I get are far (geographically) from what I should get.

How is the CPR in Surface position messages different from airborne position messages and how are they decoded properly?

The Compact Position Report (CPR) coding in Surface squiters is different from Airborne CPR coding. The resolution is 4 times better (~1.25 m instead of ~ 5 m), at the cost of losing the 2 most significant bits.

Due to this, global surface position decoding gives an ambiguous solution. IIRC the solution can be at 4 points on the globe, you have to select the nearest to you. And you should validate that it is within a realistic range, like you should do with Airborne CPR decoding. After you validated the position using global decoding on a couple of odd- even squiter pairs you can use the more efficient local decoding. Of course, as with Airborne CPR decoding, you need to protect against position jumps and time gaps in your decoding algorithm.


At what altitude does aerodynamic forces become negligible? If I sail on a boat from North to South the boat will be dragged by the oceans which it floats on, and the oceans are dragged by the Earth. Now when you go higher let say 10 km an airplane will also be dragged by the atmosphere, so the plane would "feel" an aerodynamic force against the atmosphere (rotating around Earth) if it is stationary.

But when you get higher and higher the atmosphere will get less dense and the force of the atmosphere will drop, till you probably reached satellite level where there is almost no drag of the rotation of the Earth at all.

What is the altitude an airplane can no longer "feel" aerodynamic forces because the atmosphere is so thin?

Basically, you are asking the altitude at which the atmospheric forces on the aircraft (lift and drag) become negligible i.e. the point where the density of the atmosphere is so low that the impact of air molecules on the aircraft (or spacecraft as it may be) has little effect.
Generally speaking, as the altitude increases, the density decreases, but there is no fixed altitude above which it disappears- rather it gradually disappears into irrelevance. Even spacecraft hundreds of kilometers above earth's surface in low earth orbits (LEO) have to fire their boosters periodically to overcome atmospheric drag.
The image below shows the height of International Space Station (ISS) over time, which shows the loss of height due to (among other things) atmospheric drag.

This plot shows the orbital height of the ISS over the last year. Clearly visible are the re-boosts which suddenly increase the height, and the gradual decay in between. The height is averaged over one orbit, and the gradual decrease is caused by atmospheric drag; Image from heavens-above.com
Even at that altitude, the drag can be significant for the fuel available and as NASA points out,

For most of the last decade, ... the International Space Station they were circling the globe at an altitude of approximately 220 statute miles, or about 350 kilometers.
... European Space Agency’s resupply ship Johannes Kepler... will bring the fuel needed to boost the station to its normal planned altitude of 248 miles, or 400 kilometers.
“As solar activity rises, the atmospheric density in our altitude range increases causing increased drag on the vehicle. This in turn causes us to have to raise the orbit more often.”
Even though the space station orbits in what most people on Earth would consider to be the “vacuum of space,” there still are enough atmospheric molecules ... that the cumulative effect of these tiny particles contacting its surfaces reduces its speed and causes a minute but continuous lowering of its altitude, or height above the Earth.

The question now becomes different- at what altitude does effects other than drag become much more important. Though we cant set a precise value as above, it is possible to set a theoretical altitude above which the drag can be neglected (not entirely) and other things become more important. This is called the Kármán line, which Von Kármán explains as:

... flew 2000 miles per hour (3,200 km/h) at 126,000 feet (38,500 m), or 24 miles up. At this altitude and speed aerodynamic lift still carries 98 per cent of the weight of the plane, and only two per cent is carried by centrifugal force, or Kepler Force, as the space scientists call it. But at 300,000 feet (91,440 m) or 57 miles up this relationship is reversed because there is no longer any air to contribute lift. Only centrifugal force prevails. This is certainly a physical boundary ...

(Quote from Von Kármán's autobiography, from Wikipedia)
As the drag force is similar to lift (both are proportional to the square of speed and directly proportional to density), it only makes sense to consider that the drag loses its effect on the air/space craft, at least for ease of definition.
From Fédération Aéronautique Internationale:

Astronautics needed the lack of atmosphere to be viable; Aeronautics needed the presence of atmosphere. And atmosphere existed near the Earth’s ground, but did not exist far above the ground. In Astronautics, speeds impossible to maintain in atmospheric drag could be kept for very long periods without power applied to the vehicle.
In Aeronautics, level flying higher and higher meant to deal with less and less dense atmosphere, thus to the need of greater and greater speeds to have the flying machine controllable by aerodynamic forces. A speed so big in fact, that, above a certain altitude, could be close or even bigger than the circular orbital speed at that altitude ...
A lot of calculations were made, and finally it was reached the conclusion, accepted by all scientist involved, that around an altitude of 100 Km. the boundary could be set.
The 100-Km altitude, ever since named the “Karman Line”, came thus into existence as the boundary separating Aeronautics and Astronautics.

Basically, for the purposes of your question, we can take the Kármán line as the point where the atmospheric drag loses its effect on the aircraft, which becomes a spacecraft.


Why do English-speaking pilots and ATC say "Niner" instead of "Nine"? Besides the fact that it's now a standard, why do American-English-speaking pilots and ATC say "Niner" instead of "Nine"?  None of the other numerals are pronounced in an atypical fashion.

For what was "Nine" being mistaken that resulted in the "Niner" standard being adopted?

According to Wikipedia:

  The pronunciation of the digits 3, 4, 5, and 9 differs from standard English – being pronounced tree, fower, fife, and niner. The digit 3 is specified as tree so that it is not pronounced sri; the long pronunciation of 4 (still found in some English dialects) keeps it somewhat distinct from for; 5 is pronounced with a second "f" because the normal pronunciation with a "v" is easily confused with "fire" (a command to shoot); and 9 has an extra syllable to keep it distinct from German nein 'no'.

The phonetic alphabet is not a random selection of words. It was created very carefully taking dialects into account, so as not to confuse any of the letter with possible mispronunciations. Although they are "English" words, the choices were made with the world in mind.

As mentioned on the same article:

  The final choice of code words for the letters of the alphabet and for the digits was made after hundreds of thousands of comprehension tests involving 31 nationalities.


Listening to KSEA, what does orange, green, or blue line mean? I'm listening to an LiveATC stream for the Seattle Tacoma airport.

I keep hearing things like "push approved on the blue line".

I'm pretty sure I've heard orange, blue, and green as colors.

What does this mean?

If Seattle works anything like a number of major German airports, these instructions refer to literal coloured lines on the ground.

Taxiway markings are usually yellow, but some large airports have started to use different colours for marking taxilanes on the apron ("ramp"). This is a way of maximizing use of available space in areas used by many differently sized aircraft.

One example is Munich, Germany (EDDM) where yellow, orange and blue taxi lines are used.

(snippet from APDC EDDM, from DFS)

Two medium sized aircraft can pass eachother when following the blue and orange lines, whereas a larger aircraft will have to follow the central yellow line, thus taking up the entire width of the taxiway.

As @ymb1 pointed out in a comment, the system in KSEA appears to be similar. The colour of the taxilines are varied, and signs (or markings on the ground) describe the colour code for certain taxi lines:


Where can a civilian obtain centrifuge training/testing? Where can a civilian get high g-force training/testing in a centrifuge?  (Likely by paying.)  Preferably with and without a g-suit.  Preferably based in the US, maybe Canada.

I'm betting the US Air Force centrifuge in San Antonio, Texas, and Canada's military centrifuge in Toronto would laugh and/or hang up the phone if asked.

Crossing my fingers there's a private or educational facility that would be an option.

This is a tough one. I don't know of any civilian facilities (but it does not mean they don't exist). This is a bit of a shot in the dark but in my opinion you may want to contact NASA about the Ames Research Center 20-G centrifuge. If for no other reason than this is the only non military one that seems to exist. For what its worth high speed centrifuges are not that simple despite just being something that spins in a circle. The speeds that the unit spin at are extremely high to say the least, to do this with out ripping the whole thing apart requires careful balancing and construction so they are not exactly something you can build at home. Here is at least one company that is building them and installing them elsewhere in the world. They list a bunch of installs for other militaries that might be more open to a civilian coming in but who knows.


How is a 14 CFR 101 sUAS NOTAM filed for an unregistered aircraft? FAA promotes the utilization of NOTAMs to announce sUAS operations, and requires it in 333 exemptions and some 107 waivers. However, sUAS (drones / model aircraft) under 14 CFR 101 have been determined to not require registration.

Drone NOTAM entries are not possible without a registration number.

How, without registering a 101 model aircraft, may one file a Drone NOTAM?

EDIT 15 June 2020:  Regulations have changed, and now Exception for Recreational Flyers requires that aircraft 250g or greater be registerd.  This addresses this question, as the question was relevant to former part 101 recreational flyers, which has been changed to now require registration.

However, aircraft below 250g do not require registration, and a pseudo identifier, created by the owner may be used as a registration identifier.

I will create an answer for this question reflecting the current regulatory environment.

All part 107 aircraft must be registered, regardless of weight.  The question addresses the case of Part 101 flyers, who were exempt from registration.

Regulations have changed, and the Exception for Recreational Flyers now requires aircraft above 250g, used for recreational flights, to be registered.  Hence a registration number would be available for drone NOTAM filing.

In the case of aircraft below 250g, which are not required to be registered under the Exception for Recreational Flyers, an identifier may be offered by the filer of the NOTAM.  (eg: MONGO2025551212, which might be a name and phone number)


What is the most overlooked item during preflight inspection? Have there been any studies that gathered statistics on overlooked items on preflight inspections, or even statistics on how many pilots actually perform a good preflight (following a checklist, etc.)?

If such a study exists, did it uncover anything that proved to be something that was often overlooked?

Is there an industry "best practices" document for preflight inspections (beyond just following the manufacturer's checklist found in the POH)?

This FAA article is about using electronic checklists for airline flights (it concludes that they're better than paper ones) and includes this quote:

  They found the crews averaged 3.2 checklist errors per flight (one of
  the observed flights had 14.) The most-common checklist error involved
  the omission or deferral of an item, which was later forgotten.

NASA commissioned a general study into checklists in 1990, but it doesn't identify specific items that are commonly overlooked. It does say that as the number of items on a checklist increases, the chances of overlooking any individual one does too:

  Swain and Guttman (1983), in their study of nuclear power plant
  operations “recognized the fact that as the list of items grows, there
  may be a higher probability of overlooking any given item” (chap. 15,
  p. 13)

The final section of the paper has recommendations for checklist design, which could be considered the "best practices" you mentioned, but of course it's a very general list, e.g.

  The most critical items on the task-checklist should be listed as
  close as possible to the beginning of the task-checklist, in order to
  increase the likelihood of completing the item before interruptions may occur

AOPA's Flight Training magazine has an article on "frequently forgotten" checks that is more specific and most of the checks seem to apply to most (light) aircraft, but it doesn't provide any authoritative sources. They also have a "how to preflight" article that gives more information and includes this interesting observation:

  As an experiment, I held a preflight contest with a "bugged" trainer.
  I reversed the rigging on the ailerons so their movement was contrary
  to control inputs. Every one of the contestants checked control
  movement and freedom, but no one caught the problem.

Putting all that together suggests - only to me, and I'm not an expert - that it's less important to think about specific items that you might forget, and more important to ensure that you complete the checklist fully and really verify the results of each check. If you consider some checklist items to be 'more important' than others then it could also lead to mistakes because you overlook the 'less important' ones.


How fixed air, gas and fixed weights in rigid airships is computed in this book? I hope I am posting this in the right forum. My current problem is part aviation, part maths.
I have been struggling with the following computation ( Burgess, Charles Paine. Airship Design. Honolulu, Hawaii: University Press of the Pacific, 2004. page 14. The pdf is available at http://www.xlta.org/library/burgess.pdf, note that the first edition of this book was written in 1927. The present snippet uses the typographical conventions from the pdf.)

Problem 1:
Find the volume and horsepower of a rigid airship to carry a military load of 15,000 lbs.at 60 knots (101.3 ft. / sec.). for 60 hours, 85% of the total volume being filled with helium lifting .064 lb./ft.**3 (94 % pure) in the standard atmosphere.
Since the hull is specified in the condition of the problem to be 85% full of gas,
the weight of the gas is 85% D multiplied by the difference between the weight of air and
the lift of gas per unit volume, and divided by the weight of air per unit volume. The total
weight of air and gas is therefore given:

$$
Air\; and\; gas = [ .15 + .85 ( .07635 - .064 ) / .07635 ] \times D = .288 D
$$
While this formula is not an issue, the subsequent formula has been giving me headaches.

From existing data, the fixed weights exclusive of power plant, power cars, and fuel system
equal -3D, and the crew, stores and ballast amount to .055 D. There remains for power plant, fuel, and military load

$$
( 1 - .288 - .30 - .055) D = .357 D
$$
Question is how did the author arrive at this result? Not matter how I approach solving the equation,
I am unable to get the same result. Problem is that the result of this equation is used at a later
stage. I also considered that 1 might be an i, but there was no mention of any constant i in the chapter this formula was taken from. I have no clue what I am missing here.

$D$ is the total displacement (the weight of the air displaced by the airship)
$0.288 \cdot D$ is the weight of helium and air inside the air ship
$0.055 \cdot D$ is the weight of crew, storage, and ballast
$x \cdot D$ is the unknown weight of power plants, power cars, and the fuel system
$0.3 \cdot D$ is anything else (fixed weights)

The total must be one:
$$.288 + .055 + .3 + x = 1$$
or equivalent, the total must be the displacement:
$$D \cdot (.288 + .055 + .3 + x) = 1 \cdot D$$
solve for x and you get:
$$x \cdot D = (1 - .288 - .055 - .3) \cdot D$$
or just
$$x = 1 - .288 - .055 - .3 = .357$$


How can an aircraft not fall into the sea after the arresting cable snaps during a carrier landing? After watching that video, I can't fathom how in the world could the crew save the day. Can someone give the intuition on how did that happen?

Unfortunately, I am not in the aviation, but I recall from Flight Simulator that on landing, the aircraft has such a small value of velocity. Maybe the aircraft carrier was tall enough and/or wind was helping that day?

The truth of the matter:  That E-2C pilot escaped crashing by a hair's breadth.  He was just very, very fortunate that the combination of holding full power, the position on the flight deck where the arrester pendant failed allowing for a small takeoff roll to accelerate, plus the 40+ ft drop off the deck of the ship to the waves combined with the ship steaming into the wind was enough to gain him the end airspeed he needed to fly again.  The flight crew received the Air Medal for their heroism in the face of that situation.  As an E-2 does not have crew stations equipped with ejection seats, there was no other option available to the flight crew than to attempt to gain airspeed and hope for the best.  That cross deck pendant failure could have easily resulted in disaster and most pilots in that situation don't live to tell the tale.

Although it is rare, cross deck pendant failures can and do happen and are extremely dangerous, both to the aircrew of the recovering aircraft and to nearby flight deck personnel; there have been cases where a failed cable has literally sliced a man in half.  As a precaution, each cross deck pendant has as pre-set service life of 100 traps, then it is removed from the purchase cables on the arresting gear and destroyed.

This video was shot by an sailor aboard the USS Ronald Reagan during sea trials in 2003.  The arresting gear failed, sending the aircraft over the edge of the deck.  The F-18 pilot ejected and survived.  Note the amount of damage which the end of the cross deck pendant does to equipment and personnel as it whips across the flight deck.


Can a U.S. President have a non-government owned aircraft that would routinely be given the call sign AF1? Can a US president use a personally owned jet with the call sign AF1? Would the Air Force be obligated to add security and defense measure to this aircraft if the president refused to fly in the VC-25?

Air Force One is the call sign of whatever USAF aircraft (see @slookabill's comment below) the US President travels in. Once he boards another aircraft, the call sign AF1 is transferred to that aircraft (for a dramatic example of this, see the climax of Air Force One movie).

If a president were to fly in their own aircraft (or commercially) the appropriate ATC call sign would be Executive One.

As far as fitting out a personal aircraft, the VC-25s are USAF assets (operated by 89 AW) and are highly customised and specifically configured for the job of transporting the president (and support staff), costing over $300 million. I doubt any president is going to get the option of flying their favorite aircraft on a regular basis instead of the state aircraft.

It is not likely that the government would pay to configure another (non-USAF) aircraft for the president to the same specifications as the VC-25s serving as Air Force One. After all no US President's personal car has been configured as the Presidential State Car so far.


How long can a commercial airliner fly at 90deg roll? For how long can a commercial airliner fly at a 90deg roll angle ? Or can it at all ?

What you're talking about is called "knife edge" flight, where all of the lift is coming from the sideways fuselage, making it a lifting body aircraft with big fins (the wings) sticking up and down that aren't doing anything (rolling sideways during a ballistic arc doesn't count).   The rudder is doing the job of the elevator, and the elevator is doing the job of the rudder.

To do this is requires a fairly deep fuselage profile, preferably reasonably flat sided so it makes a decent lifting body, with a really powerful rudder to effectively function as the elevator for this lifting body, and it's helpful to have a high power propeller engine on the nose helping with the lift generation.

Just about the only airplanes that meet those characteristics are purpose built aerobatic machines that can sustain knife edge flight indefinitely or some military jets.  Certainly no airliner could ever do that.


Who is the woman that famously survived a light-plane crash in the arctic in the 1950s? As a kid I read a book by a woman who crashed in the Canadian arctic and, along with the pilot, walked their way out of the bush. She lost some toes (and fingers?) to frostbite, but was otherwise OK.

I believe the action took place in the 1950s, but it might have been the very early 1960s. I seem to recall it being in the Yukon, and it was a light plane, not something like a DC-3.

She was a major celebrity for a while; I recall her getting a mail that was addressed simply "to that girl that crashed in the arctic".

Does anyone recall who this was?

I'm guessing that this is "Hey, I'm Alive" by Helen Klaben (the female survivor).

From one of the reviews:

  [...] Flores's Howard five-seater crashed in a heavily wooded region, which no doubt saved their lives. The treetops softened the crash landing yet left the plane listing at an angle, making an uncomfortable shelter for either of them to lie down. Both Klaben and Flores were injured with various broken bones, and each had limited mobility. They were not prepared for an emergency and thus had no winter supplies or extra food. Their scant supply of food ran out after being stretched to siege-of-Leningrad proportions over ten days. I recall a dramatic scene from the movie where Sally Struthers, who played Klaben, discovers a tube of toothpaste which she shows Flores, played by Ed Asner. The two treat the toothpaste as a precious meal, which is exactly how Klaben described it.
  [...]
  Once all food ran out, including the toothpaste, the pair took to re-chewing their gum and by drinking melted snow. I am amazed that they could have survived on only water for five weeks. Flores, hearing a mysterious buzzing in the distance, was determined to find out what it was. I won't spoil the story by revealing if he found out the source of the buzzing or not, but when he returned to the crash site he and Klaben moved camp to a clearing, miles away from the trees. Klaben, who could not walk because her gangrenous toes were decaying, with bone pushing through the skin, was towed along on a toboggan made from the fuselage.

National Post Article on her story

People article

Quote from People:

  When Ralph Flores and Helen Klaben were found alive on March 25, 1963 near the wreckage of his single-engine plane in the Yukon, their names became synonymous with “miracle.” For seven weeks the 42-year-old electrician and the 21-year-old Brooklyn girl had endured pain from crash injuries and temperatures 42° below zero while subsisting on little more than melted snow and a few biscuits.

  Flores was flying home to California from Fairbanks and Klaben had accepted his offer of an inexpensive ride to San Francisco. During their ordeal he lost 51 pounds. She dropped 45 and after their rescue had the toes of her right foot amputated because of frostbite. Still, they survived on guts and ingenuity.

They didn't actually "walk-out", they moved the camp to a clearing and were found. Klaben couldn't walk (due to the condition of her toes/feet).


Airplane data for thriller novel I've written a legal thriller. One scene involves the antagonist lawyers hiring someone at O'Hare to sabotage some other lawyers' private jet so that it crashes. But I don't know enough about aviation to write a plausible scene, as in what could someone on the ground do to down a plane that the pilots wouldn't see. So far, I've heard about someone deliberately installing the wrong size screws in the windshield because the pilot could miss them in pre-flight checks. This could cause the windshield to fail at altitude, either crashing the plane or ending in an emergency landing at the closest field. But are the screws are visible from the cockpit? And if so, would the pilot detect a problem before takeoff? Any guidance would be great. Thanks!

I would suggest to look into Wikipedia overview on Category:Airliner accidents and incidents caused by maintenance errors, immediately focusing on the "Investigation" sections. Some errors could be reproduced deliberately.


Why do gases in the combustion chamber only flow one direction to the gas turbine in a jet engine? As far as I know from the working principle of jets engines, compressed air in the combustion chamber (or combustion canister) is mixed with fuel. The ignited mixture expands backwards to turn the turbine rotors and perpetuates the work cycle. Eventually, the left over hot gas creates the thrust.

Although heated gas expands in every direction in space, why does the combustion-gas only expand in one direction, towards the turbine?

It is actually not that simple to ensure the proper gas speed in a gas turbine. In the compressor you want to limit the flow speed over the compressor vanes to the high subsonic range, so the inlet has to decelerate the flow down to approx. Mach 0.4 - 0.5. Less would mean less throughput and consequently less thrust.

This speed, however, is far too high for ignition. The fuel needs some time to mix with the compressed air, and if flow speed is high, your combustion chamber becomes very long and the engine becomes heavier than necessary. Therefore, the cross section leading from the compressor to the combustion chamber is carefully widened to slow down the airflow without separation (see the section below named "diffusor"). Around the fuel injectors you will find the lowest gas speed in the whole engine. Now the combustion heats the gas up, and makes it expand. The highest pressure in the whole engine is right at the last compressor stage - from there on pressure only drops the farther you progress. This ensures that no backflow into the compressor is possible. However, when the compressor stalls (this is quite like a wing stalling - the compressor vanes are little wings and have the same limitations), it cannot maintain the high pressure and you get reverse flow. This is called a surge.

The graph below shows typical values of flow speed, temperature and pressure in a jet engine. Getting these right is the task of the engine designer.

Plot of engine flow parameters over the length of a turbojet (picture taken from this publication)

The rear part of the engine must block the flow of the expanding gas less than the forward part to make sure it continues to flow in the right direction. By keeping the cross section of the combustor constant, the engine designer ensures that the expanding gas will accelerate, converting thermal energy to kinetic energy, without losing its pressure (the small pressure drop in the combustor is caused by friction and the Rayleigh effect). Now the accelerated flow hits the turbine, and the pressure of the gas drops in each of its stages, which again makes sure that no backflow occurs. The turbine has to take as much energy from the flow as needed to run the compressor and the attached pumps and generators without blocking the flow too much.

The remaining pressure is again converted to speed in the nozzle. Now the gas is still much hotter than ambient air, and even though the flow at the end of the nozzle is still subsonic in modern airliner engines, the actual flow speed is much higher than the flight speed. The speed difference between flight speed and the exit speed of the gas in the nozzle is what produces thrust.

Fighter engines usually have supersonic flow at the end of the nozzle, which requires careful shaping and adjustment of the nozzle contour. Read all about it here.


How do gull wings help? I know that gull wings are shaped how they are for maximum help with a decrease in induced drag and increase in lift, but how do they do it? This is my homework!!!

Aside from the ground clearance thing Crossroads mentioned, the main aerodynamic benefit of gullwings is to achieve a clean 90 degree intersection with the fuselage, which eliminates the need for a big wing root fillet fairing.


Is there an easy way to determine where a part goes on an airplane? In order to classify parts for export I need to determine where our parts go on the plane.  (Engine or structural/body)  Specifically looking at the canister, heat shield assy and lock support for the Boeing 767/777.

What you need is a parts catalog/diagram.

Here is one for the 767 that shows parts and where they go. Interestingly all the pictures seem to be of the BBJ (business jet) version of the 767, the other parts should remain the same.


Why might an instructor in a small aircraft choose to descend with a substantial yaw on a first lesson? Many years ago I took an introductory free (+fuel) flying lesson in a dual-control small aircraft (instructor in right seat) at a small city's municipal airport. There was a third passenger in the back. Near the end there was a report of a helicopter near the airport but there was some confusion as to the location.

When the instructor took us back down they did so in an unusual and exciting way, possibly to impress the third passenger, possibly trying to get back to the ground as quickly as possible because of the situation with the helicopter.

We were descending pitched substantially down, looking at the ground in the distance and with a startling amount of yaw with the right wing advanced by (estimate from memory) 20 degrees!

Is there a name for a descent like this? Are there standard reasons for it?

Sounds like a Forward Slip. It is not an unusual maneuver. It is very useful in order to descend faster than normal (Vertical Speed) without increasing your airspeed. The maneuver reduces the amount of lift generated while at the same time creating a large amount of drag by presenting the broad side of the fuselage to the relative wind.

Did the instructor happen to reduce the throttle to idle right before the maneuver?

It is also a great maneuver to practice in case a no-flap landing is needed due to flap failure.


Does the EPU on the F-16 need to be manually extinguished after an emergency landing? After having watched

I noticed at the end that one of his colleagues mention he has a "running EPU with hydrazine, you're gonna need fire response".

Is this just a precaution, or does this fire response actually do anything with the EPU?

The Aviationist has an entire article on this: Hydrazine: A Significant Hazard Each Time An F-16 Crashes (Or Fires Up The Emergency Power Unit). It says:

  the impact site of a crashed F-16 can be extremely dangerous and one
  of the main hazards is Hydrazine [...] When activated, the unit
  provides emergency power for the aircraft’s systems in the case of an
  electrical failure: in case of flame-out, emergency power generated by
  the EPU is designed to give pilots the time they need to land the
  aircraft safely. And, the EPU is fired up by Hydrazine.

And (emphasis in the original):

  the toxicity of H-70 is such that special procedures must be used to
  manage crashes as well as in-flight emergencies that involved the EPU
  or hydrazine leaks.

The whole thing is too long to quote, but the emergency response team certainly takes some very specific actions to deal with the hydrazine. They isolate the aircraft, give the crew breathing masks to get them away from it, check for leaks and then clean up if needed:

  As soon as the first assessment has been completed, the first team is
  replaced by a “response team hydrazine” composed by 2 Italian and 1
  American operator, equipped with special overalls (Level A, since risk
  of contact with the liquid is higher), that clear the leak along the
  track followed by the aircraft from the runway to the parking area.


What is the maximum take off climb angle of a Boeing 737 MAX? This video is making its rounds on social media claiming to show a 90 degree vertical take off:

One can not tell from the video alone what the angle is.

Does anyone have a third party reference for the actual angle for this video?
What is the maximum angle for a Boeing 737 MAX with typical passenger load?
What is the maximum angle for a Boeing 737 MAX especially configured to maximize the angle?

That’s a wild demonstration but it’s also not a very realistic  barometer performance for typical 737 operations. The video you see there is a high-performance demonstration flown in an air show or a trade show just for the purposes of entertainment. It involves an airplane that has literally been stripped down of any unnecessary parts, no other personnel or cargo on board except for the minimum required flight crew and barely enough gas to get the performance done and maintain day VFR reserve minimums to get them back to the airport.   The climb there was done in about an angle of 50 to 55° from the horizontal.    Even in these conditions a Boeing 737 does not have a thrust to weight ratio exceeding one and as such the aircraft is in fact slowing down. Still it gives an impressive climb to around 2000 to 3000 feet above the airport for the spectators below.


What is this display on the 737 Classic? Source: YouTube

I noticed that display (yellow circle) between the two CDUs. What is it for? It is not a default installation on the 737-3/4/500.

It looks like a Navigation Display/MFD, but why have it when the 737-Classic EHSI (white circle) under each EADI already overlays weather and traffic?

The display you mentioned is the Universal Avionics MFD-890R. Page 15 of this document shows the screen in question. I suppose it comes with the new CDUs for a new FMS, as mentioned by Ralph J.

  Incorporating EFI-890R hardware in a single stand-alone Multi-Function Display configuration, the MFD-890R meets the needs of operators who want to incorporate additional capabilities in the aircraft like moving maps or charts, but have limited time or budget for an entire flight deck retrofit. The MFD-890R is fully compatible with the EFI-890R and can be used as part of a complete flight deck retrofit at a later time.


When does a turbine need to go to maintenance? I'm wondering what the limiting maintenance factors for engines, for example of an A320, are. Of course this is something that is different from one engine manufacturer to another and especially from engine type to another.

But what rules are there for regular, operation driven, maintenance?
Please consider engines of any type, used for a mid-sized plane like the A320 on commercial passenger flights.

This is a very broad question, but if we limit ourselves to just high bypass turbofans, such as the CFM56 or LEAP-1A used on the A320, and limit "maintenance" to mean major maintenance that requires the engine to be removed from the wing, then the primary driver is typically the total number of flights.  Depending on the engine, it would be removed from the wing for a complete teardown, inspection, and rebuild perhaps every 5,000 - 10,000 flights (typical lifetime of the engine could be between 30,000 and 50,000 flights). Many major components are limited by low cycle fatigue (LCF) driven by thermal stress, so the cold-hot-cold cycle of a flight is what drives the maintence interval, more so than the total flight hours.  i.e. a 1 hour flight and a 12 hour flight are pretty similar in how much they wear out the components.


Can heat from the engine inlet be used to produce thrust? As the engine inlet temperature increases, Is more heat energy provided by air?
if yes then can we utilize that heat energy to produce more thrust?

I guess the heat you ask about is the temperature increase that goes with the precompression of air ahead of and in the intake. This heat is further increased in the compressor, according to the ideal gas law. If there were no temperature increase during compression, the engine could burn a lot more fuel and produce a lot more thrust.

To use the precompression heat would mean that first the air flows through a heat exchanger in order to transfer that heat to something that can produce thrust from it. That something would have to heat the air in the combustion chamber or after the last turbine stage in order to increase thrust. At both stations the gas temperature is a lot higher than the heat that can be harvested from the intake air. Now you first have to run that heat through a heat pump to make it useable (or, if you turn this around, you need a heat pump to produce a medium cold enough to harvest heat from the intake air in the first place!).

I hope you start to see how much more complicated and heavy this kind of engine will become. There have been attempts to recuperate the heat of the exhaust flow in turboprops, but so far nothing of that kind has ever entered production.


Are solid-state attitude indicators subject to gimbal lock? With all the shiny new glass cockpits it would seem that the days of the spinning mechanical gyro (and associated tumbling due to gimbal lock) should be over: Sparing everyone the boring math it should suffice to say that solid-state gyros can be engineered and built in such a way that gimbal lock is impossible, but I'm not certain that's how they're actually designed.

Do modern AHRS systems with solid-state gyros (or replacement electronic horizons like the RC Allen 2600 series) still suffer from gimbal lock, or do they provide true 3-dimensional freedom?

I'm interested primarily in answers from a light General Aviation standpoint, but answers about electronic gyros on commuter and transport category aircraft would be interesting too.

Yes and no.  Gimbal lock is a physical AND mathematical phenomenon.  Physically, gimbals sharing the same axis can cause a lock, and mathematically, a representation of a multi-axis rotation can be in a condition which is singular, depending on how it is represented and calculated internally.

Normally, we discuss and think about aircraft attitude intuitively as set of angles: roll, pitch and heading.  In mathematical circles, this is known as a set or 3-2-1 Euler angles.  If you look into the boring (or exciting, if you are that kind of person) math, you can see a vector-matrix equation relating the change in Euler angles given a set of angular rates given in the frame of the aircraft, by common convention these are referred to as p, q and r for roll rate, pitch rate, and yaw rate respectively.  The way these rates affect the change in the angles depends on the current state of the the angles, e.g. when the aircraft is pitched, a body-frame yaw rate will alter the pitch angle.  Mathematically, this means that the "state matrix" is state-dependent and must be constantly updated using the freshest set of states available.  Any set of Euler angles will have a set of states which causes the state matrix to become poorly conditioned, resulting in numerical instability at those conditions.  For the roll-pitch-heading set of angles, this happens when pitch is + or - 90 degrees.

The way that we escape the singularities when writing the software for an AHRS is by representing the attitude in a non-singular form.  This done by using more numbers to create the representation, then adding constraints which preserve uniqueness.  A 3x3 direction cosine matrix (DCM) can do this,  It has constraints which cause it's eigenvalues to lie on a unit circle in the complex plane.  My favourite representation, however, is a quaternion constrained to have unit length.  The quaternion can be thought of in terms of Euler's rotation theorem.  There's that Euler guy again, he must have been some kind of genius.  Anyhow, the idea is that you can define an axis of rotation with three numbers, and use a fourth to represent an angle about that axis to rotate.  This gives you a system free of "mathematical gimbal lock"  The state matrix remains adequately conditioned under all states.  All you need to do to keep things friendly is to normalize the quaternion from time to time, and you always have a "background" state that you can translate into aviator-friendly Euler angles.


Which country started the tradition of naming aircraft? I'm doing a project on the Enola Gay and I wondered which country started the tradition of naming aircraft?

I think the answer has to be that it has always been a tradition.

Since time immemorial - in the most ancient of mythologies and legends, across a very wide range of cultures (in fact I'm not aware of a culture that didn't name water-going vessels - boats of all sizes have been given names.

I don't think it's possible to say which country, or even which culture, started the practice of naming boats.

Many if not most of the traditions, names, roles and structures in aviation were inherited from navigation (including the term navigation of course).

Aviation, in many senses, is simply navigation translated to the sky.
Given this, it would be pretty remarkable if it hadn't always been a tradition to bestow names upon vessels in aviation too.

The Wright brothers' first powered aircraft was named (Flyer, I guess they were too busy pioneering to expend much energy on naming), but really,  it goes back longer than that, to navigation.

What I think is interesting is that now not all aircraft are named, whereas just about every boat that can be painted on still has a name painted on it.


As you make a symmetrical airfoil thicker, in which direction does the lift force increase? I am working on a project and just need to understand one concept that I cannot find an answer to anywhere and hoping you could answer for me.

The project I'm working on is with airfoils and the main on NACA 63-021. In short, from what I have read as the foil get taller/thicker it creates more lift and can handle higher angles of attack as well.

My question to you is: if a foil like this which is symmetrical top and bottom foil shape, what direction of lift is increasing as the foil shape gets thicker? is the lift seen as forward motion lift/thurst?

You help on this would be greatly appreciated!

Lift is defined as the vector component of the total aerodynamic force perpendicular to the freestream velocity vector. Wikipedia about lift

By definition lift can not contribute to thrust or drag, so the direction is fixed.

The sense of the lift vector is opposite to the flow deflection caused by the angle of attack, so the lift increases in that sense.

For your project you might be interested in looking at the lift/drag profile, rather than just at lift.


How does take off mass impact induced drag? In this answer to another question, it was stated that:

  Take-off mass: If you take no payload, the aircraft will produce less induced drag and reach a slightly higher range

How does a change of weight inside the same shaped container increase induced drag, since the air doesn't come in contact with the cargo?

Induced drag is caused by lift. (historically, Induced Drag was named "lift induced drag").

If weight(mass) of the aircraft decreases, the lift required to fly the aircraft decreases. And the drag associated to that lift also decreases.

The quoted statement is true, but "slightly" can be discussed. Because the increase in range depends a lot on how much payload the aircraft could carry. (If it's %50 of the max takeoff weight, the range could increase a lot).


Why are heading in PFD and map off by exactly 10 degrees? I was flying on my X-plane 11 flight simulator today and noticed something quite unsettling.

This was a VFR flight between KIAD and KDCA. I pulled up my map for reference and noticed I was flying orthogonal to the map's north direction, even though I was flying a heading of 100.

The image shows the map and the PFD for your reference.

What is going on? Did I mess with some heading calibration setup? 100 degrees and 90 degrees are perfectly 10 degrees off, so I don't think this has to do with magnetic north issues.

P.S. Strangely, I got to my destination simply following the headings from ATC.

KIAD has a magnetic variation of 10 degrees west, and KDCA has a magnetic variation of 11 degrees west, so true vs. magnetic north actually makes sense.


What happens when an airline pilot decides not to fly at the last minute? What happens when a commercial airline pilot wants to remove himself from a flight a short time before takeoff (say an hour or less)? He obviously can't be forced to fly, and there may be very good reasons he shouldn't.

What is the penalty for the pilot?
What are the passengers told if it is something embarrassing, like a drunk pilot?
How long does it take to get a replacement pilot?

Surely the exact answers depend on the airline, but in general what happens? What regulations govern this situation?

There would be a great deal of variability on what happens depending on the airline, whether or not it was unionized, what country it was in, who the pilot was, and the specific situation of the flight involved.

The scenario of an hour or less is a truly rare occurrence. The system is set up to prevent such happenings. The last two carriers I worked for had a 2-hour showtime. If a pilot hadn't checked in or been picked up by that time, the search immediately started for a replacement.

The only occurrence of an approximate one hour replacement need that I'm personally aware of was when a captain failed a breathalyzer test at his 2-hour show time. Given the confusion of the moment, it was well less than 2 hours when they started the search for a replacement. There was no ready reserve, and no management pilots available that were current, so they had to start stealing captains from flights due to depart later. I was due to operate JFK to AMS around 2 hours after the JFK to TLV flight they needed a captain for, so they stole me off my flight, which meant they had to get someone else for that, etc.

There is good reason for a 2-hour showtime other than just making sure a pilot is there. There is work to be done, and that work has to be done by someone. In this case, a non-current management pilot did that work, including my cockpit flow. I went directly into cockpit, sat down, and called for the before start checklist.

There was in this instance a good reason to do what could be done to avoid taking a delay. Numbers of flights leave JFK for Europe and the Middle East in the evening. If you take a delay, you may well get a lower altitude than planned because someone ahead of you has grabbed it; everybody's going over the North Atlantic track system. If that happens, you need more fuel, which is more cost, etc.

What would happen to a pilot causing a one-hour replacement depends on so many things I won't even try to address that other than to say that it could range from no penalty whatsoever to immediate termination. In the case above, the captain was terminated, and since he was in his late 50s back when the age 60 retirement rule was in effect, it was the end of his airline career insofar as U.S. airlines were concerned.


For general aviation small aircraft flying VFR under 10,000 feet, can I use my phone GPS for navigation in the US? For general aviation small aircraft flying VFR under 10,000 feet, can I use my phone GPS for navigation in the US?  So no onboard GPS (which are expensive), no VOR/DME, of course there is always dead reckoning and pilotage.

Can you do it? Sure. It is recommendable? That depends.

If you are planning to use it as your primary source of navigation, then I would say definitely no. Aviation GPS units are designed to be used on aircraft, they are reliable and have airspace maps. There's a reason they are expensive. The same cannot be said for your phone GPS.

But, if you remain aware of your position by other means (visually recognising landmarks and cross referencing them with aeronautical charts) then sure, you can use your phone GPS as an additional source of navigational information.

Just keep in mind that if the GPS suddenly fails, you should be able to continue the flight normally. If you can't, then it means you are trusting the GPS more than you should.


What is the procedure to turn an airplane when it flying? As far as I know, there are two part devices that involved when turning an airplane when it flying: aileron and rudder. How they work? Which one is first over another when turning/banking? In this case, the airplane is the common commercial airplane which is has ailerons, horizontal and vertical stabilizers, elevators, and rudder. Not the V or /-shape empennage like mostly used in drone.

Ailerons are but one type of primary flight control surface, which are used to roll the airplane about the longitudinal axis, thereby directing the lift vector generated by the wings from the vertical to the direction of a desired turn, thereby providing the required force to cause the airplane to change direction.  Ailerons aren’t the only primary flight control surfaces which can do this; other types can include flaperons, differential elevator inputs and differential spoilers.

Rudders are used to counter adverse yaw caused by the difference in induced drag created as a byproduct of aileron inputs, which cause the nose to swing toward the outside of the turn, resulting in uncoordinated sideslip and inefficient turning of the aircraft.  In the case of a V or Swallow tail, ruddervators fulfill the function of both rudders and elevators and would be used to counter adverse yaw as well.


What are the benefits of a 'cranked arrow' delta wing? What are the benefits of the 'cranked arrow' delta wing that was used on the variant of the F-16, the F-16XL?

Sourceenter link description here

The main benefits are:

High root thickness, so the wing can be made stiffer and stronger where the loads are highest.
Better pitch stability in the post-stall region, so no AoA limit needs to be observed. The X-31 could maneuver with thrust vectoring only because its cranked arrow delta wing was more or less neutral in pitch over the full AoA range. A simple delta wing produces strong pitch-up moments in the post-stall region wich would quickly overpower the moments possible with thrust vectoring.