Do all single-engined aircraft experience torque that cause a turning tendency during the takeoff roll? I've been flying the Cirrus Vision SF-50 for quite some time on my X-plane 11.

Having a single turbofan engine mounted near the V-tail, I expected the requirement of at least a little right rudder. However, it seems to be perfectly aligned throughout the roll.

Why is a turbofan any different from a propeller aircraft in this regard?

There are four reasons why a propeller aircraft will exhibit a left-turning tendency: torque, spiraling slipstream, P-factor, and gyroscopic precession.

Torque is due to Newton's third law of motion. As the engine spins the propeller, the propeller spins the airplane in the opposite reaction. Since most propellers spin clockwise as viewed from the cockpit, this results in a tendency to roll (and therefore turn) to the left. For jet engines, the rotation of the blades is cancelled by the stator blades redirecting the airflow the other way.

The spiraling slipstream is caused by the fact that the propeller is rotating, causing the air moving through it to also rotate. This spiral flows around the plane, eventually hitting the rudder. Because, again, the engine is rotating clockwise, it will tend to push the rudder to the right, forcing the nose left. Jets don't suffer from this, because, again, the internal stators make sure the exhaust gasses are (mostly) linear.

The P-factor is caused by the fact that the airplane isn't perfectly level. It will usually have a slight nose-up angle. This means that the descending blade has a higher angle of attack, and thus produces more "lift" (a.k.a. "thrust") than the rising blade. Since most engines rotate clockwise as seen from the cockpit, this means that the blade on the right will be the one producing more thrust. Jet engines don't have this because the airflow in the engine is redirected to be parallel to the engine centerline, regardless of the plane's actual angle of attack.

Gyroscopic precession is kind of complicated, so I can't really explain why this happens without a digression into a bunch of complicated physics. Just know that, if you push on the edge of a rotating disk, it will create a force 90 degrees ahead of the point you're pushing on. For a tail-dragger aircraft, lifting the tail is the same as pushing on the top of the propeller disk, thus, precession creates a left-turning force. But then, when either kind of airplane pulls up to take off, this actually causes a right-turning force. Jet engines are no different from propellers in this regard, and will produce these forces in exactly the same way. It's just that the gyroscopic precession in a typical airplane is much, much smaller than the other forces, so the creators of X-plane probably didn't think it was worth programming such a tiny force into the game.


How does the Harrier avoid engine damage when operating from dirt fields? The Harrier V/STOVL jet was designed in order for its users to be able to retain a functional air force even with all conventional airports destroyed; to this end, it can take off from, and land in, essentially any space large enough for it to fit into, potentially including unpaved dirt pads.

Unlike most jets designed to be capable of rough-field operations, the Harrier has no mechanism for preventing engine dirt ingestion, and, indeed, ingests considerable quantities of dirt and dust when operating from dirt fields:

(Image by @KeithS here at AvSE.)

How does the Harrier avoid engine damage from dirt ingestion during rough-field operations?

How does the Harrier avoid engine damage from dirt ingestion during rough-field operations?

The short answer is that they don't. They avoid using these FOD-laden strips if possible, but doesn't have any kind of active method for reducing FOD damage from debris ingestion.

This is supported by an RFP that NAVAIR put out asking for proposals to reduce FOD for the AV-8B:

  The AV-8B currently has the highest FOD damage rate in the U.S. DoD inventory which incurs a cost of more than $100M per year in engine removal, rebuild, and reinstallation, as well as decreased readiness and safety.

The method here is to just deal with it when it happens. The engine is removed, repaired, and replaced when a FOD incident occurs.

The document also says:

  To date, NAVAIR has experienced more than eight Class 'A' mishaps in the AV-8B due to FOD

Where mishaps are defined:


Why do early airliners have "backward slope" windows Does anyone know why many 1930's airliners in the US have cockpit windows that slope down and rearward, the opposite of what you might expect?

Consider the Boeing 247:

https://www.flickr.com/photos/sdasmarchives/9085364593

Or the Lockheed Electra Model 10:

https://en.wikipedia.org/wiki/Lockheed_Model_10_Electra#/media/File:Kelly-Johnson_Electra.jpg

Or the Ford Trimotor:

https://wjon.com/around-the-town-taking-a-ride-on-a-1929-ford-tri-motor-video/

This seems to have disappeared shortly after, the DC-2 and on, for instance, lack this feature.

If it's a good idea here, why not in the cockpit of an aeroplane, right?

Image source

The forward slope was designed to avoid reflection of lighted instruments in the window panes, but that turned out to create other reflections. From this site:

  The cockpit windshield of the first 247s was angled "forward" instead of the conventional aft sweep. This was the design solution (similar to that adopted by other contemporary aircraft that used a forward raked windscreen) to the problem of lighted control panel instruments reflecting off the windshield at night, but it turned out that the forward-sloping windshield would reflect ground lights instead, especially during landings, and it also increased drag slightly.[12][13] By the introduction of the 247D, the windshield was sloped aft in the usual way, and the night-glare problem was resolved by installing an extension (the glarescreen) over the control panel.[14]

Also mentioned in this answer.


Do any countries besides the USA accept Basic Med? Are other countries accepting Basic Med for flights through their airspace, for example the European Union?

(I've made this a community wiki answer so that others can add new information if/when things change.)

These countries allow US pilots to fly with BasicMed:

The Bahamas
Mexico (from 10 Dec 2019)


Does the FAA consider flights that generate content for profitable YouTube channels displaying airborne video to be commercial operations? Is there any guidance from the FAA such as an Advisory Circular, Letter of Interpretation, or other document that directly clarifies the scenario below?
If a pilot creates aerial video content while acting or logging as pilot-in-command and profits from advertising revenue through a service such as YouTube on which that video content is hosted, would that cause the flights during which the videos were recorded to be considered commercial operations by the FAA?
Note: Videos made by costs-shared-pro-rata passengers are not within the scope of this question.

The answer here is, potentially yes, but it depends.  In the United States the Federal Aviation Administration casts a wide net out over all kinds of activity it sees a potentially commercial in nature.  Former FAA lawyer Kathy Yodice wrote an AOPA article on what the FAA considers compensation or hire activity.  Unfortunately, the answer is not always clear; the FAA sees compensation as virtually anything of value and often just “knows it when they see it”.  Yodice writes:

Certainly, compensation comes in the form of any payment of money, but it also includes those instances when no money is made on the flight or when the payment isn’t even enough to cover all of the expenses.  The simple exchange of money to reimburse all or some of the expenses like fuel, transportation, lodging, or meals is usually enough. Compensation can also take the form of accumulation of flight time. Compensation can be good will or the expectation of future business. It could be the effect of furthering one’s economic interest or the prospect of a return favor. Something of value paid or given to a third party could be considered compensation if it is conditioned on the operation of the aircraft. For now, the FAA’s policy is to draw the line at considering charitable deductions of costs as compensation:  “Since Congress has specifically provided for the tax deductibility of some costs of charitable acts, FAA will not treat charitable deductions of such costs, standing alone, as constituting ‘compensation or hire’ for purposes of the regulations.” But, that is about the only exception we’ve seen in practice.  Otherwise, if you get something for taking the flight, the FAA is likely to call it compensation; if, in fact, you get nothing, you won’t have run afoul of the regulations.

So could a private pilot run afoul for making money on YouTube for flying videos?  Possibly.  Essentially YouTube is brokering an arrangement between content creators and advertisers and videos are ‘something of value’ to advertisers.
But here’s the catch.  In the above scenario, you are not directly exchanging your ability to pilot an aircraft for something of value; you’re simply out flying an aircraft.  Recording the flight is just incidental to it.  Editing, publishing and then selling the footage for compensation is something you’re doing on your own time and not related to your flying.
Another caveat is that §61.113(b) states that a private pilot may act as PIC for compensation or hire if:

(1) The flight is only incidental to that business or employment; and
(2) The aircraft does not carry passengers or property for compensation or hire.

Now in the YouTube scenario, a professional content creator’s business is content creation, not flying and the flight was only incidental to the person’s primary business.  It’s similar to an FBO employee and private pilot asked any his supervisor to ferry an airplane from the main office to a satellite airport for use there by the business.  Here the employee, even though a private pilot, many fly for compensation or hire as the flight was only incidental to the business.
Now let’s take a scenario where, say a content creator and private pilot gets numerous requests from social media subscribers to shoot a particular location from the air or the performance of specific maneuvers or demonstrations of the aircraft.  In this case we begin to get into a gray area where the overlap of exchanging airmanship for something of value starts happening.  It becomes even more suspect if the persons making the request are authorized representatives of the firms which advertise on this pilot’s social media channel.  Potentially an overzealous FAA inspector could cite you for flying for compensation or hire.
Again it all depends.  For more information on this subject I would consult an attorney who operates specifically in aviation law.


What happens when autopilot and propulsion settings do not match? Autopilots used in piston GA usually do not have throttle control. They only manage the control surfaces. However to trim an aircraft one needs to play on both throttle setting (and more physically, thrust) and control surface deflections (aerodynamic forces). What happens if the autopilot cannot trim the aircraft due to the propulsion settings? Is there any alert from the autopilot for the pilot?

It all depends on the autopilot, but generally no. If for example, you tell the autopilot to climb at 300 fpm, it will keep adjusting pitch to do just that.   As you climb higher (without changing the power) the autopilot will keep increasing pitch to maintain the set vertical speed.  Eventually the airplane will get too slow because of the increased pitch and can even stall.  Some autopilots have pitch limits or monitor the stall inputs and automatically disconnect before it gets to this point, but others don't.  It is very important to know your autopilot and to monitor it at all times to make sure that it is doing what you want.


How can I find out the best time to practice within towered airspace? I would love to practice within towered airspace (approaches, touch and goes, ect.) However, I do not want to upset operations within the airspace.

What is the best way to determine when the best time to practice these maneuvers would be? Should I contact both the tower and TRACON?

Simplest answer: Call the tower. Or ask instructors/schools in the area if the controllers care when you arrive and want to practice. Usually if you arrive during the busiest time, you'll likely be accommodated as best as they can, but there's a chance you could be told to just do a full-stop taxi-back operation if that helps out or told to go fly around elsewhere for a bit.

It depends on what airport you're thinking about going to. If you want to go to ATL, well, you'll be vectored in a gap, and told go as fast as you can for as long as you can, and be told to land(or if you go around, expect a long delay to find a new gap). If it's just a general aviation airport, anytime is fine.


Is there any clear picture or drawing, of a Wright brothers' plane, published before August 12, 1908? Based on a video and two articles, one form May 1904, and the other from December 1951, both of them quoting people who personally knew the Wright brothers (see the explanations below), I have reached the conclusion that the oldest clear published photos of a Wright powered flying machine appeared in French newspapers on August 12, 1908, and the oldest unclear pictures in the Scientific American, on May 30, 1908. Another conclusion would be that the Wright brothers could not have taken any picture, at Kitty Hawk, North Carolina, of one of their airplanes in flight, before April-May 1908.
Question: Are there newspapers, magazines, etc., older than Aug, 12, 1908, that show a Wright airplane on the ground or flying? I am looking for them in archives but I can not find anything.

Video link: The Wright brothers and their imaginary 1903-1905 flights
The Wright brothers did not even finish the 1903 plane at Kitty Hawk, NC. Flyer 1 never flew as can be seen in the following 1904 article:
The Wilmington Messenger, Wilmington, North Carolina, May 26, 1904, col. 1, p. 6.

Elizabeth City Economist: A gentleman visiting this city whose home is
in Kitty Hawk, is responsible for the assertion that the Wright
brothers, of airship fame, will return to Kitty Hawk in the near
future and resume work on their aerial monster. According to this
gentleman the airship has never been removed from Kitty Hawk and
nearly all the interviews published in the papers of Norfolk have been
erroneous in this respect. This gentleman has assisted the Wrights in
all their work and has a general supervision of their property during
their absence. He says that they have not completed the ship and
that they will return some time within the next month and resume their
work. A story is current that they will complete the ship and make
the trip from here to St. Louis sometime this fall.

The text says that, according to a man that worked for the Wrights and took care of their things left behind at Kitty Hawk, the two inventors hadn't finished Flyer I as of May 26, 1904. In conclusion, this machine did not fly on December 17, 1903!

The true date of the above picture is May 1908 not December 17, 1903.
The fact that the photo was taken in May 1908 is also supported by the 1951 declaration of Alpheus W. Drinkwater, a man who knew the Wright brothers.

Wilbur and Orville Wright are credited with making their first powered
flight in a heavier-than-air machine on Dec. 17, 1903. But Alpheus W.
Drinkwater, 76 years old, who sent the telegraph message ushering in
the air age, said the brothers only “glided” off Kill Devil Hill that
day. Their ﬁrst real flight came on May 6, 1908, he said. (Source: New York Times, Dec. 17, 1951.)

As a note: The Wrights left Kitty Hawk, North Carolina, in December 1903 and only came back in April 1908.

I am not aware of any picture printed before August 1908 and showing a fully recognizable Wright plane, beyond any doubt.
As a remark, there exists a drawing, published in L'Auto, a French newspaper, on December 24, 1905, but it is just a rough sketch. However, this caricature is the closest drawing to what would become to be known as the Wright planes, much later, starting with August 1908.
As an explanation: Robert Coquelle, a French journalist, while in the United States for other purposes, visited the Wright brothers, did not see any plane and once back in France he made fun of them in L'Auto in an article titled: "The conquest of the air by two bicycle dealers". Coquelle does not clearly explain the origin of the drawing below that illustrates his article.

The true aeroplane of the Wright brothers.
Source: 1905-12-24, Robert Coquelle, “La Conquête de l’Air par deux Marchands de Cycles. Comment un ancien champion cycliste, Johanny S. Johnson, introduisit un rédacteur de « l’Auto » dans l’atelier des frères Wright.”, L’Auto, Paris, Saturday, December 24, 1905.


How hot do internal parts of jet engine get? How hot does a jet engine get? I'm interested in the temperature of the parts, not of the exhaust or combustion. If you took temperature of an engine after a flight across the Pacific Ocean what are temperatures of stationary and movable parts? A car engine block may be 250 degrees Fahrenheit (120°C). I'm thinking of how to modify the basic architecture.

This parameter is called Turbine Inlet Temperature (TIT)

  Turbine Inlet Temperature (TIT) is the temperature of the combustion
  chamber exhaust gases as they enter the turbine unit. The gas
  temperature is measured by a number of thermocouples mounted in the
  exhaust stream and is presented on a flight deck gauge in either
  degrees Fahrenheit or degrees Celcius.

Essentially it's the temperature going out of the combustion chamber, representing the highest temperature the turbine would face.

Here's a figure showing how we are doing recently. So we are at around 1800K now and may reach 2000K soon.

For the temperature of the actual part under cooling, here is the current status of materials: we are at around the 1350K mark and may approach 1400K soon.


Why is a model quadcopter 'better' than a helicopter? Why doesn't this scale up to the full-size versions? EDIT

  Soon after I posted this, it was pointed out that a similar question
  exists. That other question answers most of mine. I shall leave this here as a stub. That way it provides a pointer to the other question and, importantly, my title contains all the keywords 'model', 'quadcopter','helicopter' and 'scale up' whereas the other question's title (Why haven't quadcopters been scaled up yet?) is less comprehensive and therefore less searchable.

Model helicopters were on the market for many, many years before quadcopters.

Presumably most of the engineering bugs had been removed by then as well as control issues.

Suddenly along comes the new kid on the block and it's all change.

Related questions

Why are model quadcopters so popular in relation to model helicopters?
How come the same reasons don't apply to full-size helicopters and quadcopters? Why don't we see search and rescue quadcopters and personnel-carrying quadcopters?

Cheap MEMS gyroscopes have been on the market only since maybe 10 years. Before you needed more bulky and expensive gyros. Also, cheap and powerful micro controllers which can process the sensor data quickly enough and can control the speeds of the four motors to stabilize the quadcopter have only been available recently. The third recent innovation was more gradual, but also the storage density of batteries was not available maybe 20 years ago. With modern LiPo batteries you can have flying times of several minutes where NiCd batteries only gave you a fraction of that time for the same mass.

For your second question: The reason is similar to why birds have not been scaled up to carry humans, like horses do. This answer should give a good explanation.


Is my understanding of subsonic inlets correct? For subsonic aircraft like commercial jets, the inlet has the job of making sure the correct airflow is coming into the engine. Correct airflow is important for keeping the engine's compressor stage working. Too little or too much airflow will cause the compressors to stall and therefore no combustion happens. The inlet must keep airflow constant throughout the different stages of flight, including take-off, landing and banking.

The way an inlet ensures correct airflow into the engine is by slowing down the airflow and increasing the pressure. The inlet has a large volume which will decrease the speed and therefore will decrease the pressure. An inlet will work differently during low speed flight and high speed flight:

Low speed flight – During low speed flight including take-off and landing, the aircraft isn’t going fast enough for sufficient airflow to enter the engine. All engines have an operating design where they need certain airflow to work. To get enough airflow into the engine at low speeds, the engine's fan will suck in air. Air will be sucked in from a large area in front of the inlet. The streamlines of air will converge together as they get closer to the inlet. However, there is a location on the inlet where air does not move. At low speed flight, this stagnation point is on the outside of the inlet. This forces oncoming air to enter the inlet and not go around the engines nacelle. This provides the engine with enough air velocity at low speeds to operate efficiently.
High speed flight – During high speed flight the aircraft is going fast enough for sufficient airflow to enter the engine. However, allowing too much airflow will cause the compressors to stall. The inlet isn’t relying on the fan to suck in air from all directions. Air directly enters the inlet because the aircraft's velocity is fast enough. So to stop too much airflow entering the engines, the stagnation point moves further inside the inlet. This means that the desired airflow enters the engine, and the unwanted airflow flows around the nacelle.

Is this understanding of subsonic inlets correct?

Your understanding is correct.

However, you attribute too much activity to what is essentially a passive device. The inlet only guides the air such that it flows uniformly, without separation and at the desired angle towards the fan and the compressor. The pressure field resulting from this flow is doing the acceleration rsp. deceleration, and the pressure itself is a result of the compressor swallowing just as much air as it needs.

Converging streamlines indicate a pressure drop and acceleration, and diverging streamlines a pressure increase and deceleration. In the static condition, the engine creates suction inside the intake which causes air from all around to flow towards the intake. At high speed it cannot swallow more than a fraction of the air flowing towards it and partially blocks the flow through the nacelle. As a consequence, air gets pushed to the sides and the flow into the intake is decelerated.

It is really the engine, not the intake, that controls how much air is ingested. The intake only makes sure that this happens in an orderly fashion without separation and vorticity. Different flight speeds only mean that the pressure ahead of the compressor changes, while the speed of the air entering it is quite constant over flight speed.


How do I determine the diameter of my propeller at high altitudes? I'm designing a electrically propulsed HALE UAS and I need to find the diameter of my propeller to find my thrust. Is there an equation for propeller diameter that doesn't rely on knowing my thrust or velocity. In particular an equation that is concerned with relative air density as this is meant to be optimum at high altitude cruise conditions.

You have the process of propeller sizing backwards. This makes the question unanswerable.

I need to find the diameter of my propeller to find my thrust.

Normally, you start with a thrust demand at a given speed and work form there. After all, the propeller is needed to compensate for airframe drag at that speed plus any climb requirements. Without that, you have a glider.
Another route is to start with the torque the engine can supply. Now the propeller has to be able to absorb this torque at the given speed, producing thrust. But you still need to check this thrust against requirements in order to get engine size right.
So please do yourself a favor and find out what thrust you need. The rest should be easy. Use 85% for efficiency to arrive at a suitable $\Delta$v and assume that half of all losses are from friction.
This lets you arrive at $$\frac{\Delta v}{v_{\infty}} = 2\cdot\left(\frac{2}{1+\eta_{Prop}}-1\right)$$ which becomes 16.2% of flight speed for an overall efficiency of 85%.


Why do autogyros exist? This question has been intriguing me for some time. In Autogyro the rotary blades merely acts as what fixed wings act in normal aircrafts to generate lift. So why not simply have a fixed wing instead of rotary "wings"? What advantage do this rotary nature of wings provide compared to fixed wings? In both ordinary planes and autogyros the propulsion is generated by the front or aft engine.

Autogyro blades have a higher airspeed than the aircraft that is carrying them, so they can generate lift even when the aircraft speed is low. They fly as if they had a wing the size of the whole disk, not just the blade area - yet can be stored or transported easily.

They can land (but not take off) almost vertically, which is a useful safety feature in the event of an engine failure.

Having said that, they aren't common because they don't do anything useful significantly better than the other options, except perhaps being 'different and interesting'. Flying slowly isn't terribly useful.


Partial ownership: are there any pitfalls to owning the plane through a shell company? I'm currently saving money for a plane and training, and the expectations are that I won't have the money for full ownership of much else north of a Cessna 150.  I'm investigating partial ownership instead, and I've read that forming a company/partnership to own the plane is better than each member of the group just pitching in out of pocket.

Are there any drawbacks to using this method for plane ownership?

The main thing to do is to realize why you're creating the corporation.  We created a 501(c)7 (in the US) corporation which is a tax-exempt organization and falls under "social club."  We did this to limit our personal liability.  However, if you are creating the corporation to limit personal liability, you have to make sure to operate like a corporation - call each other "co-owners" instead of "partners" (there are legal ramifications to this, not just semantics).  People around the airport should know it's a co-owned plane by a corporation, not that it's "your plane."  Basically if you want the liability protection of a corporation, you must act like one.

Great book to read regarding the legal side of things is "Practical Aviation Law" by J. Scott Hamilton

Depending on how you set it up (we did a 501(c)7 tax exempt, and yes, you still have to file a tax return), how you use the airplane matters too.  For example, we can't earn money using the airplane (conducting flight instruction to non-co-owners, for example), due to the 501(c)7 status.  Under other corporate structures you can.

Finally, I guess to actually answer your questions: There are some pitfalls, but I think they can be avoided.  Most group ownership things fail because of lack of communication and documentation, forming a corporation kind of forces you to spell out things explicitly and then all involved have no excuse for not knowing "the rules." (You have to write up bylaws and have at least one annual meeting, which forces the communication aspect!)


What is the difference between the words "airlines" and "airways" semantically? I wonder what the difference between the words "airlines" and "airways" is. Do you have any information on this?

I am asking this question to find out why some air carriers use "airlines" while others use "airways" on their brand names.

This answer assumes that you are asking about the business name chosen by various air transport companies, such as "American Airlines" vs "British Airways".

Short answer:

There is no difference semantically. It's purely a marketing decision. The company decides which "sounds better", and uses that as their official business name. There are several other similar nouns used in business names as well:

"Air" (either before or after): Air France. Korean Air. Or even as part of the name: Ryanair.
"Aviation": Grant Aviation.
And then don't forget that Delta uses a space:  Delta Air Lines.
And then there are even some companies using several different nouns throughout their sub-divisions:  "Trans Executive Airlines of Hawaii" is the name of a single airline company, but their cargo services are performed under the name "Transair", and their passenger services are performed under the name "Interisland Airways"

Long answer:

There is some historical context, going back to the days when ocean travel was the only form of international travel between continents separated by oceans. A "line" was a route between two points. A "liner", then, was a ship that sailed that line. Since it was on the ocean, it was commonly called an Ocean Liner, and companies that popped up to provide a scheduled service on those lines used the term "line" or "liner" in their name: Black Ball Line, or American President Lines.

When Trains came into being, they took up the same vernacular from their ocean transport heritage. The system of rails between two points was usually built by a company for its own use, and was sometimes called a "railroad", or a "railway", with no discernible reason why some chose one term over the other. The term "line" was still used, interwoven into the industry: a "main line" was a company's main route between two cities, and a "spur line" would branch off to a smaller town.  Some companies named themselves with either the "roads" or the "ways" part: The Kansas Pacific Railway, or the Western Pacific Railroad.

The next major transformation in the transportation industry was air travel, which again borrowed terminology from both its ocean and rail heritage. An "air line" was a route between two points, and an aircraft providing service on that line was an "air liner", and company names went one of two directions: Air Lines (such as "Eastern Air Lines"), or Airways (such as "Western Canadian Airways")

The terms "air liner" (for an aircraft) and "air line" (for a company) eventually worked their way into the single-word terms as we know them, and they are officially defined, today.

But even in the early days, there were still many different nouns working their way into the company names: National Air Transport, Western Air Express, or Ford Air Transport Service. Following the Air Mail Scandal, (in which existing companies had to give up their air mail routes), many companies either merged or simply changed their names to re-gain air mail contracts. Several companies with names of XXX Air Lines (with the space) simply changed to XXX Airlines (without the space), and this is now why we see this term (Airlines) in company names today.  (with Delta Air Lines being a notable difference)


Has the FAA moved to change its use of gender-specific words like airman? Last year, the United States Navy was ordered to review all of its job titles related to gender reference, e.g. yeoman, fireman and seaman.  The Air Force has initiatives to fully integrate women in all jobs, and has also been pressured to review job names: Air Force Times Story, Jan 14, 2016

Has the FAA taken any action to review or change gender-specific titles like "airman"?  Is there a non-gender specific title like "airperson" coming into use?  Terms like stewardess and cockpit have been dropped from parlance.

Is there anything official or brewing at the FAA on this subject?

I'd be interested in your comments if using flight crewmember would be a valid substitute for the term airman.

This AC from 2009 lays out some regulations on it for part 21 regulations

  j. Replace the masculine pronouns “he” and “his” with gender-neutral
  terms. The new rule uses plain language.

It looks like they also made a lot of changes to the medical code in 1996 that covers it as well.

  Where appropriate, changes are made to eliminate gender-specific pronouns, to replace ‘‘applicant’’ with ‘‘person,’’ to use current
  position titles and addresses, to correct spelling and improve syntax,
  and to adjust section and paragraph references.


Why do passenger embark on the left side of an aircraft? I speak of passenger aircraft that can be found on large airports.
The left side is used by passengers (and the crew) to embark/disembark (see the position of jet bridges) and the other side to embark/disembark the rest (e.g. food).

Why do we always use the left side for passengers? What prevents an airport from deciding to use the other side?

If this is an historical decision (e.g. one day in the past an aircraft builder decided passenger should use the left side, then majors airports were built accordingly and thus new aircraft were built accordingly and thus new airports were built accordingly), is it possible and reasonnable to build a jet bridge made to operate on the right side of an aircraft and then use the right side for passengers and the left side for the rest?

Why do passenger embark on the left side of an aircraft?

Because the cavewoman who invented the log-canoe was right-handed?

Note: I arrived at this answer by looking at a kind of etymology of the terms starboard & port but that's incidental. The answer to this question happened to be contained in an answer to a rather different question. Some groups of aviators may have dropped the archaic terms while still being subject to a continuation of an archaic habit/convention.

People get on the left side of a jet airplane because Vikings (etc) steered their wooden boats with a steering board (hence starboard?) held in their dominant right-hand.

Since it was inconvenient to have your steering apparatus wedged against a quayside (or earthen bank) they docked at the port along their left side and therefore loaded and unloaded on the left.

Farhan's comment leads you to this answer in English.se which I reproduce here for convenience

Excerpt from trivia on the Navy website:

  Port and starboard Port and starboard are shipboard terms for left and
  right, respectively. Confusing those two could cause a ship wreck. In
  Old England, the starboard was the steering paddle or rudder, and
  ships were always steered from the right side on the back of the
  vessel. Larboard referred to the left side, the side on which the ship
  was loaded. So how did larboard become port? Shouted over the noise of
  the wind and the waves, larboard and starboard sounded too much alike.
  The word port means the opening in the "left" side of the ship from
  which cargo was unloaded. Sailors eventually started using the term to
  refer to that side of the ship. Use of the term "port" was officially
  adopted by the U.S. Navy by General Order, 18 February 1846.

So it's a historical convention, many arbitrary choices are of this sort. Pioneers of a new form of transport adopt the terms (port, startboard) and habits of more ancient forms of transport.

Ironically, since aircraft became able to carry substantial non-human cargo, the cargo entry has moved to the other side to reduce the chances of crushing the human cargo with the non-human cargo. Presumably also because having lots of large holes all in one side may be structurally disadvantageous.


What are typical insurance costs for airliners? What are typical insurance costs for airliners, and how are they arrived at?

Factors that might be relevant are hours flown, number of landings/takeoffs per year, total hours of airframe and engines, hours on type for the pilot in command, etc. - but are they considered, and how?

Also, are long-haul flights treated differently than short-haul?

Obviously, each specific contract is covered by commercial confidentiality, but some baseline estimates should be available somewhere.

for personal airplanes(like a Cessna),

  Expect to pay anywhere from $600 per year and up depending on the airplane, your time in type and total hours.

source (http://www.planeviz.com/cost-of-aircraft-ownership-ep-9/)

while there are no estimates (that i can find) about the really big commercial airplanes like the 747, there are estimates available for smaller airplanes like the G650 (  )

the estimate for this plane in insurance is 60,000 USD per year

source (https://www.quora.com/What-are-the-yearly-maintenance-and-total-overhead-charges-for-a-65-million-Gulfstream-G650)


Do FAA sectional charts show all power/transmission lines? The FAA's sectional aeronautical charts include some power/transmission lines. How complete is this?

I am specifically interested in using something like ForeFlight for aeronautical charts while hot air ballooning. Is this a fool's errand?

If it is an incomplete reference for power/transmission lines, does anyone know what criteria the FAA uses for inclusion in the charts?

From the FAA's Chart Users' Guide:

  AeroNav Products’ charts are prepared in accordance with
  specifications of the Interagency Air Cartographic Committee (IACC)
  and are approved by representatives of the Federal Aviation
  Administration (FAA) and the Department of Defense  (DoD).

Book 2 of the IACC Specifications covers Sectionals and VFR Terminal Charts and provides the following guidance for transmission lines:

  3.6.6.3 Telecommunication and Power Transmission Lines (T-Lines)

  3.6.6.3.1 Landmark Value

  T-Lines, if depicted on charts, are shown primarily for their landmark
  value. Determination of whether a T-line has landmark value or what
  constitutes chart congestion are matters of FAA Flight Edit judgment.
  Flight Edit shall either delete or add T-Lines on the Flight Edit
  Standard. T-lines with landmark value should be shown in open country
  and not in congested or built-up areas. Through open country, T-lines
  should be shown as continuous lines, interrupted only for reasons of
  cartographic practices. Location of the pylon symbol is dependent
  upon the length of the T-line; approximately at 1" intervals on a line
  3" or less in length, and approximately 2" apart on lines longer than
  3".

The transmission lines may also be charted under the rules of section 3.9.8.6 Obstructions.

So, no. T-Lines are not charted exhaustively. They are charted only when they have landmark value or are charted as an obstruction.


Cabin crew : how do they get Oxygen in the event of decompression? According to this answer, in the event of an explosive decompression it can take as little as 9 seconds to develop problems without an Oxygen supply.

How are cabin crew meant to get to an oxygen supply when they're a long way from their allocated seat ? There's not only distance to consider but if they're jammed between two carts in the middle of meal service they're not going anywhere too quickly !

There are usually extra oxygen masks in the cabin- it is a regulatory requirement. From 14 CFR 25.1447 - Equipment standards for oxygen dispensing units:

(c) If certification for operation above 25,000 feet is requested, there must be oxygen dispensing equipment meeting the following requirements:
(1) ... There must be ... at least two oxygen dispensing units connected to oxygen terminals in each lavatory. The total number of dispensing units and outlets in the cabin must exceed the number of seats by at least 10 percent. The extra units must be as uniformly distributed throughout the cabin as practicable.

So the cabin crew can use the nearest unused oxygen masks. Also, each flight attendant position has a portable oxygen system, which can be used in case of emergency (though it is intended usually for therapeutic purposes). in addition, there is also the Protective Breathing Equipment in the cabin. Though these two are not intended for normal use during decompression, I guess it can be used in case of an emergency.


Why does it take so much fuel to start a jet engine? I just watched an Abrams tank documentary and it said something like it takes "1 liter of fuel for every mile but 39 liters for a startup." Is it true of turbine engines in general that they need a lot of fuel to start? If so, why?

The first figure, 1 litre per mile, is very wrong. The second, 39 to start, is most probably the fuel required for a warm up from a cold start. The Abrams tank weighs 62 tonnes, so you won't get 1 mile on a litre. Its fuel consumption is quoted as 0.6 mpg, or 1.66 gallons per mile, which is 6.3 litres per mile. Quite a difference.

The engine is the Honeywell (previously Lycoming) AGT 1500. It has a two spool gas generator, with a two stage power turbine. It features a heat exchanger through which the HPC exit air flows, to preheat it from the exhaust gas, prior to combustion, to improve engine efficiency.

The engine has a tactical idle that keeps it running at 1500 rpm instead of 950 so that it can rapidly accelerate from a stationary position if needed to avoid or engage a hostile force. In tactical idle it consumes 30+ gallons per hour, instead of 10 at the non tactical idle setting.

It's stated that "in 1990, Project on Government Oversight in a report criticized the M1's high costs and low fuel efficiency in comparison with other tanks of similar power and effectiveness such as the Leopard 2. The report was based on data from U.S. Army sources and the Congressional record."

Some critics say the tank fuel consumption is so poor, that in combat, it has to often wait for the fuel supply logistics to catch up. Other reports deny this. (See paragraph at the very top of the page).

The M1 Abrams was chosen after a competition in June 1973, between the Chrysler Corporation and the Detroit Diesel Allison Division of the General Motors Corporation to build prototypes of a new tank designated M1, and later named the Abrams tank. In November 1976, it was announced Chrysler won the competition.

  The M1 was faster and more maneuverable than its predecessors in the M60 series, while offering a lower, smaller silhouette. Besides the substantial gains in performance, the Textron Lycoming AGT-1500 turbine engine was far more reliable than the diesel tank engines then in use with the Army. There was still another benefit. The engine change, despite a penalty in fuel consumption, also resulted in much quieter operation, so much so that soldiers encountering the tank in early maneuvers started calling it "Whispering Death".

The Abrams wikipedia page also states a figure of 6.3 liters per mile, and also states the value of 38 liters to start. As suggested by user3528438 (thank you), the 39 litres (10 US gallons) is quite probably the fuel required to complete a warm up from a cold start. At the tactical idle setting, this would be the fuel consumed in about 15 to 20 minutes.


Are there little seat belts or other restraints for the organ-containing coolers kept in cockpits? The NPR podcast A Surgeon Reflects On Death, Life And The 'Incredible Gift' Of Organ Transplant features Dr. Joshua Mezrich a surgeon who flies to other hospitals to retrieve organs for transplant discussing his book When Death Becomes Life.
In the beginning of the interview he says (my transcription effort):

There’s lots of different ways different centers do it. At our center we have some pilots who fly for the state who are on call for us, and typically we fly in a Pilatus, which is a single engine turboprop,
It is true that organs sometimes get sent on commercial planes; kidneys in particular, so if you ever see a cooler in between the pilots when you board it’s typically a kidney.

Are there little seat belts or other restraints for the organ-containing coolers kept in cockpits of commercial aircraft? Or are they just placed on the floor?

"between the pilots" depends on the aircraft. On larger commercial aircraft and even some fairly small planes the area between the seats is occupied by the FMS and throttle units and there really isn't anywhere to put a cooler as seen here:

(source)

A lot of aircraft (bigger than the PC-12 mentioned) have jump seats in the cockpit. If unoccupied these seats have a set of restraints that could theoretically hold a cooler depending on size.

You can find the legality of putting stuff on the floor in the cockpit in answer to this question.

For short distances organs move in helicopters and for longer distances they may move in a private jet presumable in the back with a courier. I would not jump to the conclusion that coolers in the cockpit are organs. Ive seen a few organs loaded into lear 35's at my local airfield.

For the record, if you ever see a cooler in my cockpit its more than likely a ham and cheese sandwich.


Simple explanation for static and dynamic pressure? From what I understand, static pressure is just the pressure of still air and acts perpendicular to the airflow and surface. An airplane will feel static pressure regardless of whether it is moving or not. If there was airflow moving through a pipe, then static pressure is the pressure exerted on the walls of the pipe.
On the other hand, dynamic pressure is the pressure that results from the motion of air, or its kinetic energy. It acts parallel to the flow of air. Would it be appropriate to say that dynamic pressure is the pressure exerted on the windward side of a flat plate in the pipe like this:

If this illustration is correct, then does that mean maximum dynamic pressure is felt by a surface when it is perpendicular to the flow?

Static pressure is a force per unit of area due to fluid molecular motion leading to some statistical collisions with its environment (a solid submerged or another fluid for instance). Pressure gives an information of the fluid state (in a thermodynamics sense) and is a « measure » of the force apply by molecules as a whole. Wikipedia could be helpful on that topic.
Dynamic pressure is a bit confusing term as it is the kinetic energy of a fluid parcel (a unit of volume). This parcel has different form of energy (internal, pressure, potential) and this one is energy due to its motion. But it is not a pressure at all and does not act on the solid. However, disturbance created by the body (the flat plate on the picture) will slow down the flow in front, increasing pressure near surfaces. But this is still that pressure difference between front and back which is « felt » by the plate.
In fact, I believe this is the reason why we call it dynamic pressure. It is an energy form (known as kinetic energy) which is easily changed into pressure (or inversely pressure changing to kinetic energy) during fluid dynamics process: drag and lift are created like this on a flow around a body, gas expanding inside jet engine nozzle for thrust generation, etc..


Is there a brightness switch for the AOA gauge on the F-16? Is there a brightness switch for the AOA gauge on the F-16? Please share a picture with the panel if you can.

The F-16's manual is declassified since it's in service in many countries.
AOA Indexer
The answer is yes, the switch (lever) is conveniently located on the gauge. From said manual:

AOA Indexer
(...)
A dimming lever, located on the left side of the indexer, controls the intensity of the lighted symbols.

And here's a photo from airliners.net (red arrow):

AOA Indicator
In case you mean the AOA indicator on the instrument panel (yellow arrow above), then no, it doesn't have its own separate lighting. It will be the instrument panel light switches aft of the flight stick.

Source: airman.dodlive.mil; click here for the switches schematic (first two rows)


What energy density is required for the batteries in order to make an all-electric analogue of the Cessna 150 or similar plane? I think I have some general understanding that at the present moment even with the best possible batteries, a 2 seater training aircraft (like the C-150) would be very impractical. I'm not even talking about electric analogs of the Piper Seneca, let alone airliners. At the same time, compared to piston engines, electric engines are less heavy for their output and far more efficient (I think around 90+ %). Pipistrel claims that Siemens has a 85kW engine which is only 14 kg. I also like the idea that electric engines offer us some flexibility in the energy distribution.

What sort of progress do we need in terms of energy density of current batteries, to make a 2-4 seater aircraft real and equivalent in terms of range and performance to its piston analogues? Also, will it be cheaper to charge as opposed to the cost of liquid fuel? (Assuming the electric engine is similar to a piston one in terms of power.)

Short Answer

Batteries would need to be somewhere around 16.7MJ/kg to give the same range and performance as liquid fuels, this is about 18.5 times the capacity of the best lithium-ion batteries. Price-wise it will cost about 30-35% to charge your airplane as opposed to fill it with liquid fuels at today's prices.

Long Answer

This is a good question which is hard to give an exact answer to, so this will be more of a Fermi Approximation. To answer this you need to look at the energy contained in the fuel and the efficiency of the engine used.

Looking at the energy of the fuel I will use Specific Energy, which is the energy stored in a material per unit of mass. Specific Energy is related to Energy Density, which is the amount of energy contained per unit of volume. Often the terms are interchanged.

The specific energy of avgas and jet fuel is about 43 MJ/kg. The best lithium-ion batteries top out at about 0.9 MJ/kg (the batteries in a Tesla are about 0.7 MJ/kg), so they have a fraction of the storage of liquid fuels. The best battery technology in theoretical development (Lithium-air) has a theoretical maximum of 41 MJ/kg, more realistically they'll get 1/4 to 1/3 of that from the technology, which is still vast.

Internal combustion engines are about 35% efficient, the other 65% is wasted whereas electric engines are much closer to 90% efficient or more.

There are other factors to consider:

Weight: fuel tanks, piping and pumps take weight, and electric motors are much lighter than internal combustion engines. The batteries would need a storage structure but an electric system would probably be lighter overall
Battery inconsistencies: avgas supplies a consistent amount of energy in every single drop whereas batteries will sag as they discharge (this is regulated to give consistent power to the motor, however at some point levels will drop below what is regulatable, so not all the power in the batteries will be usable). Also, over time they lose capacity and become less efficient. Both these factors mean that you'd want to build in extra battery capacity to compensate

So I'm going to assume these two will compensate for each other, the weight savings from going electric will be offset by the need for extra capacity to ensure consistency. Assuming that all other factors are equal (propeller efficiency, etc) we can extrapolate the actual efficiency of the systems to get an approximate figure of an internal combustion on avgas: 35% of 43 MJ/kg = 15 MJ/kg of actual benefit. We can use that figure to determine what specific energy we would need from batteries to get the same amount by dividing by electric motor efficiency: 15 MJ/kg / 0.9 we get 16.7 MJ/kg.

So batteries would need to store 16.7 MJ/kg to give us the same energy as liquid fuels, but how does it compare to existing battery tech? Right now commercially available battery technology is about 0.9 MJ/kg, so it would need 18.56 times more storage capacity (16.7 / 0.9 = 18.56) to supply the same amount of energy.

As for energy costs this is going to vary a lot depending on fuel and electricity prices over time and place; we can use some of the same figures above to work the numbers. I'll assume an airplane that holds 40 US Gallons (150 liters) as the math is easy and it's about the capacity of a Cessna 172. I'm going to do separate calculations for the US and UK to see how they compare:

In the US: Avgas is about \$5.20 per US gallon at the moment, that's \$208 to fill up your airplane of 40 gals. Avgas has about 34.2 MJ/liter of energy, multiply that by 150 liters for 5130 MJ of energy. Internal combustion engines are 35% efficient and electric engines 90%, so we can calculate that an electric airplane would need 5130 * 0.35 / 0.9 =  1995 MJ of electrical power to fill up. 1995 MJ is about 554 kWh, at somewhere around \$0.135 per kWh it would cost you \$75 to charge an airplane with the same amount of energy.
In the UK: Avgas in the UK is about \$2.23 per liter (\$8.47 per US Gallon (ouch!)), so it would cost \$334.50 to fill up an airplane. 554 kWh of electricity costs about \$0.17 per kWh, so it would cost \$94 to charge the airplane

EDIT:
I did consider the efficiency gain from weight loss as fuel is burned, i.e. a variable mass system, I left it out of the answer as it isn't significant compared to the other factors in what is already an approximation. It has to do with the fuel fraction, which is the percentage of the aircraft weight that is fuel, which on a light piston single is comparatively low. A Cessna 172 carries about 40 gallons of fuel, 38 of which is usable, weighing about 228 pounds as opposed to a typical take-off weight of 2200-2300 lbs. In other words its fuel fraction is about 10%, even on a long range flight using every bit of fuel you will only lose 10% of your weight, and I would approximate that you'd get around 5% benefit from it. This was not enough of a factor compared to the other considerations, and it would probably be offset by regenerative descents where the electric motor actually generates power from the spinning prop.

For airplanes where a more significant portion of the weight is fuel, i.e. a higher fuel fraction, efficiency gains from variable mass is a much more significant factor, for example an A380's fuel fraction is 44%.


Can Ballistic Parachute Recovery Systems be safely deployed in a storm? Suppose the plane is in a thunder storm, and the pilot loses control of the airplane. Would deploying the ballistic parachute be a safe option? Meaning, is it likely that everyone would come out alive? Assume that as soon as the plane hits the ground at a reasonable speed the occupants are safe(as in, there's no ocean to drown in). Has this ever been done before?

Manufacturers are going to have different opinions of this scenario, but this answer follows the opinion of Cirrus Aircraft in their flight manuals and CCIP syllabi for the SR2X airplanes.

First off, your best bet is to obtain a proper weather briefing prior to departure and obtain in-flight weather updates enroute so you can stay out of a thunderstorm in the first place.  The CAPS has very specific guidelines for operations as well as a maximum demonstrated safe deployment speed, depending of the model of aircraft.  The flight manuals for the SR2X aircraft all state that:

"However because the CAPS is expected to result in structural damage to the airframe and, depending upon adverse external factors such as high deployment speeds, low altitude, rough terrain and high winds, the CAPS deployment may result in severe injury or death to the occupants and its use should not be taken lightly".

Barring that and you actually enter a thunderstorm which is so severe that it either causes departure from controlled flight or structural failure, there is a clause in the CAPS literature stating that if an accident is imminent, even if the acitivation of the CAPS is outside the demonstrated safe deployment range, it should be utilized and activated nonetheless.  The reason has to do with minimizing the amount of energy on impact and even a partially deployed or damaged CAPS is going to slow the aircraft considerably, increasing your chances of survival.

Bottom line is that you did something stupid vis a vis a serious lack of judgment where a safe recovery is no longer possible.  Whatever happens in the next few minutes is probably going to hurt really bad; the only thing we can do is make every effort to minimize how badly we are hurt and minimize the chances that we are going to be killed.  Even an unsafe CAPS deployment in this situation is better than riding down to impact without.


How does the Airbus auto takeoff system work? Can you explain in a easy way, how the auto take off system of Airbus works? What is needed on a modern aircraft to perform the take off without help by a pilot?

This is a quote from Airbus's press release:

  Rather than relying on an Instrument Landing System (ILS), the existing ground equipment technology currently used by in-service passenger aircraft in airports around the world where the technology is present, this automatic take-off was enabled by image recognition technology installed directly on the aircraft.

So it sounds like the plane is using the same technology used in autonomous cars, which are able to use computer vision and cameras to navigate traffic.  Except in this case the plane just had to keep center-line and rotate at the appropriate speed.

It is also shown in Airbus's video, ATTOL: Autonomous Taxiing, Take-Off and Landing test flight:


What kind of sunglasses are good for flying? I'm a beginner at aviation. I'm currently in training for gliders license.
Our instructors mentioned that sunglasses are very important if not mandatory.

What kind of properties do I need to look for in sunglasses to determine whether they are good for flying?

No polarizing glasses, they make reading anti-glare instruments difficult and sometimes even limit your outside view if the cockpit windows are polarized as well.
Good fit, you don't want to loose them in the slightest of turbulence. Consider fitting a strap so you can temporarily hang them around your neck. They also need to be comfortable if you wear a headset over them.
Neutral colour (grey, grey-green, brown) of the lenses, which does not distort the natural colours too much as that would make distinguishing navigation lights more difficult.

Actually the FAA have published a safety brochure on sunglasses which covers many aspects.


Why aren't there any single turbofan airliner? A configuration which looks like a DC-10, without engines mounted under the wings. Let's say 737 sized.

Let's forget about redundancy security advantages of twin or quad engines, since they're obvious and not my concern about this particular question.

One single engine is more efficient than two similar engines. Efficiency multiplies, two engines are less efficient, four even worse.

Center of gravity problem doesn't exist since wings can be moved backward.
(of course yaw stability will be corrected inherently)

Modern turbofans family can provide a single stock powerful enough version to fly a 737 class size.

In the event that debris is released from the engine, one canard configuration may be designed, in order to prevent hydraulic failure and loss of control.

To summarize, are there (except redundancy safety concerns) any reason why there are no single turbofan airliners?

Airliner designs must be certified in order to fly commercial services. In the US, this means compliance with the Code of Federal Regulations, Title 14, Subchapter C, Part 25. In §25.901(c) it says:

  For each powerplant and auxiliary power unit installation, it must
  be established that no single failure or malfunction or probable
  combination of failures will jeopardize the safe operation of the
  airplane except that the failure of structural elements need not be
  considered if the probability of such failure is extremely remote.

Engines do fail from time to time, so there must be a second unit which can take over if one fails. It's the same for fuel pumps, instruments or even wheels: Every one has a second unit which can take over if the first fails. For wheels, this is very easy to check: You will not find a single airliner landing gear leg which has only one wheel. All have two wheels or more.

Or pilots: The minimum number of pilots for safe operation is two. One can fly the plane (so she/he can land it if the other pilot is incapacitated), but two are needed to start any revenue flight.

I could continue that list, but I guess the concept has become clear: For every element on an airliner there needs to be a second, redundant one, except for structural elements with a very remote probability of failure.

This has been learned the hard way: Some of the first aircraft designed for passenger service (like the Junkers F-13 or the Fokker F.II) had a single engine. Some of the multi-engined ones even became dangerous death traps when one engine failed. Over time, the desire to increase safety made redundancy the supreme design principle for airliners.

Military operators have fewer qualms about single engine designs, because using fewer engines improves performance and lowers acquisition and operation cost.


What is a flameout and how does it occur? I often hear the word "flameout". What is this and how does it occur?

Flameout basically means that the flame in the combustion chamber has been extinguished. A jet engine compresses air, then adds fuel and ignites it. So, it needs three things to function correctly- fuel, air (oxygen), and the heat to make them burn. Removing any of the three can cause a flameout.

It can happen for a number of reasons:

fuel starvation- Air Canada Flight 143 suffered flameout (due to wrong amount of fuel being put) and had to be landed like a glider.
Compressor stall (or surge)- The disruption of airflow due to compressor stall can cause an engine flameout.
Ingestion of foreign objects - British Airways Flight 9 suffered flameouts in all four engines due to ingestion of volcanic ash
Firing of armament- Early in its service A-10 Warthog suffered flameouts due to the engines ingesting the gassed generated while firing the GAU-8 Avenger.

Early jet engines (like the Jumo 004B) had high rates of flameout; however, modern jet engine flame outs are very rare, at the rate of about one every 100,000 non military flights. In most cases of flameout, the engines are restarted for resumption of flight.

Airspace magazine mentions a case where flameout happened because a F-100 ingested fuel (during aerial refueling); however, such occurrences are quite rare.


How much does the horizontal stabilizer on a 737 move for one unit of trim? Inspired by this question, what exactly is the meaning of a stab trim unit? Is it exactly one degree of stabilizer movement?

The 737 NG FCOMv2 (9.20.9 Flight Controls - System Description) only lists the ranges of the units:

  Stabilizer Position Indication and Green Band

  Stabilizer position is displayed in units on two STAB TRIM indicators located
  inboard of each stabilizer trim wheel. The STAB TRIM indicators also display the
  TAKEOFF green band indication.

  The trim authority for each mode of trim is limited to:

  Main Electric Trim

  flaps extended 0.05 to 14.5 units
  [737-600] flaps retracted 4.10 to 14.5 units
  [737-700] flaps retracted 4.30 to 14.5 units
  [737-800] flaps retracted 3.95 to 14.5 units
  [737-900] flaps retracted 3.90 to 14.5 units

  Autopilot Trim 0.05 to 14.5 units
  Manual Trim -0.20 to 16.9 units.

  The green band range of the STAB TRIM indicator shows the takeoff trim range.
  An intermittent horn sounds if takeoff is attempted with the stabilizer trim outside
  the takeoff trim range.

The full range of travel can be seen as a black arc in the following image (taken from this answer), which could be 17°, but it is hard to say from the image:

The stab trim unit is an offset to the actual horizontal tailplane angle. It is added by Boeing to make the trim value positive.

1STU = 1 degree


What does it mean to "lock on" to a DME ground station? I was just reading about the working of the DME the other day and then I read a para which said:

  The aircraft interrogator "locks on" to the DME ground station once it
  recognizes a particular pulse sequence having the same spacing as the
  original interrogation sequence

Can anybody please elaborate on the above statement? I just want to know what is "lock on" and how does an aircraft interrogator lock on to a DME ground station?

"Lock-on" just refers to a unit receiving multiple different response signals in response to its interrogation broadcasts, scanning for the signal it's looking for, and when it finds the signal who's encoding matches its channel selection, it starts to process that signal and ignores all others.  It's locked on to that signal.


Is the Falling Leaf maneuver used for UAV recovery? The Falling Leaf maneuver is a way to lose altitude by descending like a tree leaf. Is this maneuver used in the recovery of UAVs?

Source.

The maneuver as described is not a particularly efficient way of losing altitude: You're alternately stalling & recovering from the stall.
More efficient descent procedures exist.

The technique of holding the aircraft in a wings-level stall (or putting it into a spin) was used in the early days of aviation to get back below a cloud deck if you were trapped "on top": when you broke out below the clouds you would recover from the maneuver & proceed to your destination / landing (if you were lucky enough to have sufficient altitude to recover when you came out of the bottom of the clouds).

Needless to say neither of these maneuvers makes much sense for an unmanned aircraft: If your goal is a rapid descent you will execute a maneuver that gives you the best possible descent rate (such as the emergency descent procedure in the POH, or the one in the Airplane Flying Handbook); If your goal is to get back below the clouds you've already busted the regs (you need to maintain visual line-of-sight with your UAS), but if and when the regulations change you should also be able to recover using more modern techniques (like descending on an instrument approach or using a synthetic vision system) to ensure you don't hit anything, like another aircraft.


How does increasing the size of a jet engine make it more fuel efficient? The design trend is there: 8, 4, 3, 2 jet engines on powering the large cargo or passenger aircraft.  Is it mostly to accommodate the larger, more efficient fans, or are there also benefits in the combustion cycle?

Jets seem more immune to the issues of excess heat removal that their piston engine predecessors suffered when scaled to greater size.  Is there a limit to how large an axial jet engine can be?  Are we approaching that limit today with engines such as the GE9X at over $130 \, 000 \, \text{lbs}$ of thrust, or is there more to go?

The efficiency issues are as follows.

For a fixed amount of mass flow rate through a work-extracting thermodynamic process, one large engine is more efficient than two smaller ones because the pair of smaller engines present more interior surface area relative to the mass flow through them than the single larger engine. The more wetted area inside the engine relative to the mass flow, the greater will be the frictional losses. This drives the designer toward fewer and larger engines and away from more numerous and smaller engines.

In addition, there are aerodynamic losses associated with each engine nacelle/pylon assembly on the wing which are minimized by reducing the number of engines installed per wing.


What am I doing wrong in this RBI exercise? The GYRO indicates the flight direction of the aircraft.

The RBI indicates where the non-directional beacon(a location on ground that’s sending the plane signals) is located.

Top of the RBI is always North. The yellow arrow point towards the beacon, however this is relative to the flight direction of the aircraft.

I always seem to mix it up. Can someone explain what exactly am I doing wrong here?
I seem to be selecting the correct symbol but when it comes to the grid then I mix it up.

You've got the heading right.
Now rotate the whole view of both instruments to the aircraft orientation, and you see the direction in which the Relative Bearing Indicator (RBI) points. Now it's easy to place it onto the correct position on the card.
The RBI points towards the beacon, but does so relative to the aircraft The dial with the compass in the background is not rotating automatically with the gyro compass, so unless it is manually alligned to the gyro, the top is always north.


Why are tugs the least priority when talking to ground? I was listening to this ATC conversation (3:10) and wondering:

Why are tugs the least priority when talking to ground? I am thinking that some tugs might be towing aircraft that need to depart.
Why are tugs even talking to ground? Whenever I am on a plane at some airports, I see roads next to taxiways with cars, buses, and other vehicles that stop when airplanes are about to cross their paths (such as the roads with the dashed white lines in the picture). Do tugs travel on roadways or on taxiways? Do tugs communicate with ground while they are on a roadway?

1) The video you are specifically referencing is JFK (as you probably know). JFK has a very complex airport layout and generally is very busy. There are a variety of reasons "tugs are last priority."

While it's not a specific rule to always allow airplanes under their own power to move first - Air Traffic Control exists to expedite the flow of traffic, which includes ground traffic, and often times tugs are just slower and because they are often relocating to different gates, pads, or hangars, they tend to get in the way of the normal flow of traffic.

Often times departing airplanes need a specific sequence (order) at the departure runway which cannot be delayed by lower-priority things such as airplanes being tugged around the airport.

Airplanes that are being tugged around are not under their own power and not burning nearly the amount of fuel that a taxiing aircraft is. Again, specifically with JFK, there are so many airplanes the ground controller must keep things moving to have an even somewhat organized and expedited flow. Often times, tugs are moving airplanes that are not filled with passengers, so the theory being "they can wait" (needs of many outweighs the needs of the few).

Even more often, and specifically with JFK, the airlines schedule causes those "tugged" airplanes to want to come into a one-way "alleyway" in the ramp when many revenue passenger filled planes are trying to exit. The tug with the airplane gets to wait, because they physically can't get into the alleyway anyways until all the airplanes taxiing move.

2) In the US, airports have what are called movement areas and non-movement areas. Movement areas are generally controlled areas, by either ATC "ground control" or by a "ramp control." Non-movement areas, contrary to its name, are areas that are not controlled by ATC or a ramp control and up to the user to maneuver without control instructions. Tugs only communicate with ground when they are on movement areas (taxiways and runways). Roads are generally non-movement areas. At some airports (JFK being one of them) when a road intersects a movement area, a vehicle on the non-movement area must always give way to traffic on the movement area. So, a tug driving around without an airplane attached would be on the road most likely, and only talk to ground control if that specific airport required a clearance to "Cross" the taxiway at the road. This is commonly referred to as a "look and go" operation. Look and go is specifically authorized only for roads that intersect taxiways at certain airports, and never allowed for runway crossings. Busses almost never operate on taxiways, except to cross them as described above. In general, unless a vehicle has a specific purpose to use the movement area, they'll use a road, because it's easier.


What aircraft can make these sharp 90-degree turns? I took this photo when I saw a plane make a crazy 90 degree turn. What kind of aircraft could do this? I have a plane finder app for commercial aircraft and this plane did not show, which is the first time that's happened.

It looks like a 90 degree turn, but it isn't. You're not looking vertically up at it; you're looking at a fairly shallow inclination, maybe only 20 degrees elevation at the corner of the turn. It means that the actual course change is probably only about 20 or 30 degrees, and just looks like more because of the optical effect of foreshortening. As for the aircraft, pretty much anything capable of flight at high altitude - probably 30,000 to 40,000 feet - any jet airliner or many business jets.


What is the equation for calculating static thrust? I'm building a quadcopter as my bachelor's degree thesis. I'm having trouble finding a reliable equation for calculating the static thrust for a quadcopter. The equations I have found give me ridiculous results. I know that it's difficult to derive such an equation and I know that there are online calculators (like this). But how do these calculators calculate static thrust? There has to be an approximate equation somewhere. This is what I'm asking. I don't mind the equation(s) that lead me to there, I would just like to know them.

Edit: More information

The following snapshot is taken from Mathcad software. It's various equations i have gathered from supposed trustworthy websites. These equations lead me to the calculation of static thrust. I think the equations are pretty self explanatory. Thank you.

Components of the quadcopter: Battery, ESC's, Motors, Propellers, frame

Various useful websites that i've found most equations: 1, 2, 3, 4

By now you should have found this answer on static thrust. It explains how to arrive at this equation for static thrust $T_0$:
 $$T_0 = \sqrt[3]{P^2\cdot\eta_{Prop}^2\cdot\eta_{el}^2\cdot\pi\cdot \frac{d_P^2}{2}\cdot\rho}$$
Your P is at most 11.1 V × 4.5 A = 49.95 W. Your prop efficiency $\eta_{Prop}$ must be guessed; let's take 60%. The electric efficiency should be higher; let's use 95% for now. The prop diameter $d_P$ is 3 or 5 inches (depends if your comments or the picture in your question is more reliable), so I use 0.127 m for now. Air density is given with 1.18 kg/m³.

When I plug in the numbers, I get 2.894 N. One propeller can lift approximately 295 g of quadcopter, and all four will produce thrust equivalent to the weight of 1.18 kg in Earth's gravitation. Looks about right for a quadcopter of 500 g.

Don't assume that the motor delivers all the power the propeller can absorb. Also, don't assume that the RPM of the isolated motor can be maintained when it is driving a propeller.


Why are APU engine generators rated in kVA and not kW? Auxiliary Power Unit (APU) generators seem to be rated in kilo-volts-amperes (kVA) and not kilo-watts (kW). Are kVA not the same as kW? Is there a reason why the generator is rated in terms of kVA instead of kW?

Current and voltage don't always vary at the same time, one usually lags, this lag is the root of evils found in electrical engineering.

Any device is a mix of resistive load (no lag), inductive load (current lags) and capacitive load (voltage lags).

The lag (phase shift angle) is denoted with Greek letter φ, and usually expressed as cos φ, or power factor. Power factor $=100 \cos φ$. Each device has its own individual φ, which may vary with conditions.

Lag effect is only visible when voltage or current changes. This happens transiently in DC when the circuit is closed or opened (effect used to create high DC voltage from low DC voltage in a contact breaker), but constantly in AC  (not mentioning other induced variations, e.g. changes in mechanical demand on an electric engine will change the impedance of the coil, so the current). The effect of the phase angle increases with circuit frequency, and is significant in aircraft circuitry, with major loads working at 400 Hz.

With this lag, the voltage and current mean (RMS) values are not sufficient to size electrical circuits. A phase shift introduces additional power in the circuit. This reactive component is not described by the RMS values, it's only visible when looking at instantaneous values, for example on this animation of the addition of two phasors, where the fixed circle radii indicate the mean values, and the moving dots show the instantaneous values. In simple cases one can determine the power required using the triangle of powers:

(Triangle of powers, source)

The apparent power is the sum of the real part of the power (resistive load in W) and the imaginary part (reactive load in VAr).

Work (Joule) is only produced by active power (the reactive power produces no actual work) and the active power rating of the generator must be higher or equal to the active power rating of the load. However the reactive power produces a reaction on the generator (by phase shifting the current) and must be accounted for when sizing the generator. The generator must have an apparent power rating higher or equal to the apparent power rating of the load, at the working phase angle.

A higher apparent power, regardless of the active power, requires a more robust generator and wiring to prevent overload.

One way to simplify the required power calculation is to just add the apparent power value of all devices (in VA). The result in VA or a multiple like kVA is conservative. This allows to select the generator required, provided we know its VA rating too. This is why generator manufacturers provide this value.

Notes:

All units, VA, VAr, W, are of the same kind (dimension of power, W). VA and VAr denote the fact that voltage, current and power are not varying in-phase in AC circuits. These units describe the kind of "power" we are taking about.
When the apparent power rating (VA) is the only rating known for a device, the active power rating (W) can be assumed to be no more than 60%, however the actual value depends on multiple factors and this is only a quick approximation. A generator must be provided with a chart showing the relationship between VA and W under different conditions of use.
A generator cannot work under any power factor, and cannot maintain the same efficiency across the valid power factor range. It is provided with a table or graph showing the acceptable conditions. For example, for this generator, the power factor must be kept in the green area (inductive load, between 80 and 100%), and will start being unreliable at some power factor, depending on the active power delivered and the type of reactance (red area).

(Source)
The explanations above are really simplifications, because in AC, the phase difference is only one side of the problem of reactive power. The other side is the presence of harmonics which are per definition out of phase.

The general principle in electricity is that voltage is set by the generator, and current is set by the load. The load can set a current which has the same frequency than the voltage, this is what we assumed for the answer. However most of the time the load sets a current variation which doesn't coincide with the voltage frequency and/or shape.

This non-linearity between current and voltage creates 'harmonics' and unbalances phases (so a current start flowing in the neutral, which is not something we want).

A little story about that relates to first datacenters in years 1990. Standby generators (diesel) not well sized were unable to sustain computers loads, due to a capacitive reactive power created by computer switching power supplies (non linearity and a cos φ as low as 0.6) Fires ensued, it was time to understand how to deal with apparent power.
The $φ$ angle just comes from the general definition of a sine wave current. Current at time $t$ is defined by $a = a _{peak} \space sin \space (\omega t \space + \varphi)$ where $a _{peak}$ is the maximum current, $ω$ the angular frequency (314 rd/s for the EU grid) and $φ$ the phase shift angle.


What is the content of a Letter of Agreement between the Collaborative Decision Making participants? Can you give a sample of a Letter of Agreement?
How to calculate average taxi time at airport?

First, a little bit about CDM and the participants that make up the team.  The FAA's CDM Website provides the following overview:

  Collaborative Decision Making (CDM) is a joint government/industry initiative aimed at improving air traffic flow management through increased information exchange among aviation community stakeholders. CDM is comprised of representatives from government, general aviation, airlines, private industry and academia who work together to create technological and procedural solutions to the Air Traffic Flow Management (ATFM) challenges faced by the National Airspace System (NAS).

This "team" of government/industry representatives is called the CDM Stakeholder's Group (CSG). There is a "Membership Agreement" that all parties of the CSG sign. This agreement outlines the roles and responsibilities of the FAA and each CSG member. It provides "rules" and processes for exchanging data and resolving disputes should any arise. It outlines the methods by which to modify the agreement, and how long the agreement should last.

A sample of the agreement letter that the FAA provides to each stakeholder member of the CSG is available to view here: http://cdm.fly.faa.gov/wp-content/list_yo_files_user_folders/cdm_editor/cdm_doc/CDM%20MOA.docx


Low hour Pilot wants to move up to Piper Malibu Mirage but having trouble finding insurance I am a 350 hour instrument rated pilot and current. I own and fly a Piper Saratoga II TC and I am rated for complex, high performance, retractable wheel airplanes. I have approximately 150 hours in the PA 32. Current age 59.
I want to move up to a FIKI factory installed airplane and have been mentored that perhaps the PA 46 Piper Malibu Mirage would be a great next step.
Having issues with companies willing to insure me even though my Saratoga has similar systems just not quite as fast. Any suggestions from anyone on what I can do except fly more hours to get insurance?

You won't be able to get around the time-in-type requirement for insurance. That's pretty much a set-in-stone requirement, especially for a high performance aircraft like the Mirage. I suggest that while you build the hours you fly with someone who meets the requirements for insurance.


What is this quad-jet plane at El Paso Airport? If you look at El Paso International Airport on Google Maps, on the south side apron and across from a hangar that is labeled "Sierra West Airlines" (west of the NASA facilities) there is a small quad-jet plane:

The aircraft is about 20 m long and has a wing span of about 18 m:

Any idea on what this is?

It's the McDonnell 220, registration N4AZ.

(Source)

Wiki says

  The McDonnell 119/220 was an attempt at making a business jet by McDonnell Aircraft in the late-1950s. It had a configuration that was unique by bizjet standards, with four jet engines mounted in individual pods underneath a low wing; it could accommodate ten passengers in a luxury executive configuration but could carry as many as 26.

  ...

  The McDonnell Corporation used the airplane as a VIP transport for a few years before donating it to the Flight Safety Foundation's research facility in Phoenix, Arizona. As of 2020 the single prototype is still extant, registered as N4AZ and stored at El Paso International Airport.

Only one such plane exists. Its first flight was in 1959.

Here are some pictures.


Why don't single-engine jets suffer severe gyroscopic effects? I was reading up on World War I fighter aircraft, and saw that rotary piston engines, which powered many of those planes, produced extreme gyroscopic effects due to the large, heavy chunk of metal spinning at several hundred RPM; as a result, single-engine aircraft using these engines had extreme difficulty turning to one side but could make exceptionally sharp and quick turns to the other side.

Why don't modern single-engine fighter jets experience even worse gyroscopic precession than their World War I counterparts, seeing how the compressor/shaft/turbine assembly in a turbojet engine is far heavier than a WWI rotary engine and spins far faster?

Well, jet engines do have gyroscopic effects.  It is a major concern in the design of the turbomachinery.  When the plane pitches/yaws, the resulting gyroscopic moment causes the compressor and turbine blades to move closer to the case.  If excessive, this can cause the blades to rub into the case, causing loss of performance.

As to why the plane is not affected by the gyroscopic moment of the engines, let's compare a few numbers.

Take a typical WWI era plane such as the Vickers FB19 powered by a Le Rhone 9J.  The engine has a mass of 146 kg, the majority of which is rotating and produces 110 HP. The plane has a maximum takeoff mass of 675 kg, which includes the engine.  The rotating mass is a fairly sizable fraction (~20%) of the mass of the plane.  Therefore the gyroscopic effect of the engine has a big impact on manueverability.

Now compare that with an F16 powered by an  GE F110 engine.  The high pressure spool of the engine has a mass on the order of 200 kg (the whole engine is about 2000 kg and the high speed rotating spool is about 10% of that... sorry I don't have a specific reference).  The max takeoff mass of the plane is about 19,200 kg.  The rotating mass is only 1% of the total mass of the plane.  So the gyroscopic effect is not so important. i.e. compared to the moment required just to turn the plane itself, the gyroscopic moment is not large.

Further, to be more precise, the gyroscopic moment is not actually proportional to the mass, but to the mass moment of inertia, which is proportional to radius squared.  A lot of the rotating mass of an older rotary engine was at a fairly high radius, whereas a lot of the rotating mass of a jet engine rotor is at a fairly low radius.  Although I have not done the calculations, my guess is that a modern fighter jet engine spool probably has a lower moment of inertia than a WWI rotary engine, despite the higher mass.

Edit:

In response to the comment by J Walters, let me try to make this a little more precise.  The moment required to perform an angular acceleration is $M=I\alpha$, where $I$ is the moment of inertia.  Let's assume that the plane is a rod (length >> width or height).  That's not totally correct, but it's good for an order of magnitude approximation. Then from this formula, $I=(1/12)mL^2$.  So for the FB19, the moment of inertia is $(1/12)(675)(5.54^2)=1726 kg-m^2$.  For the F16, $(1/12)(19200)(15.06^2)=362885 kg-m^2$.  So, comparing these two, the moment that the control surface have to apply to turn the plane (at a given angular acceleration) is 200x higher for the F16.

Now, let's look at the moments due to the gyroscopic effect. The gyroscopic moment is $M=J \Phi \times \Omega$, where $\Phi$ is the angular velocity of the aircraft maneuver and $\Omega$ is the spin angular velocity of the engine, and $J$ is the polar moment of inertia.  I said before that I expected $J$ for the F16 to actually be lower due to lower radius, but let's just assume they are the same.  The Le Rhone spins at 1,350 RPM.  I don't know exactly, but I know the F110 high pressure spool top speed is between 15,000 - 20,000 rpm.  So the gyroscopic moment is about 10 - 15x higher for the F16.

And as Peter Kampf pointed out, the aerodynamic forces go up too. The FB19 had a top speed of about 100 mph whereas the F16 can hit 900 mph at sea level.  From NASA's excellent series, both lift and drag scale with velocity squared.  So the aerodynamic forces are 81x higher for the F16.

So, in summary, yes, the gyroscopic moment is one order of magnitude larger on the F16. But everything else that the plane has to deal with during maneuvers (the moment of inertia of the plane itself, aerodynamic forces), are two orders of magnitude higher.  So the gyroscopic forces are less relevant in comparison.


Why choose to ditch in the sea over bailing out? I recently watched the film Dunkirk (I highly recommend watching it).

Without wanting to give away too much information about the film, a Spitfire pilot is flying over part of The Channel. They lose their engine and state the sea looks calm and opt to ditch over bailing out.

Why would a Spitfire pilot choose to do this? Is ditching in the sea really safer than parachuting out?

Bailing out the cockpit during that era was neither an easy nor always a successful task. The pilot had to either roll the plane, open the canopy, and release themselves to the void, or if rolling wasn't possible, walk on the wing and jump.

That's inherently unsafe. Don't forget that you are not exiting a healthy plane. There might be smoke, debris, fire, propellers spinning, the tail that might cross your way out.

Read what happened to Hans-Joachim Marseille when he tried to bail out. Quote from Wikipedia:

  the left side of his chest striking the vertical stabiliser of his fighter, either killing him instantly or rendering him unconscious to the point that he could not deploy his parachute.

Now, regarding ditching versus bailing out, I don't have any source to substantiate the chances of survival, because in the end, what matters is to get out of there alive. But I guess it depends on many factors, one of them being the sea state as they mention in the film.

Another one is the type of damage the airframe has sustained. It might be better to risk a "gentle" contact with the water if there is no "urgent reason" to leave the plane and you can ditch reasonably soon, than to exit the cockpit and increase the chance of being injured by anything that I've mentioned in the first paragraph.

Finally, it turns out that the choice heavily depends on the situation. I haven't seen the movie so besides the "sea state" I don't know the details. So provided that you are above a water mass capable of supporting the ditching idea, the factors mostly influencing the decision are:

Airframe condition
Altitude below you as Pete pointed out and Philip Johnson mentioned in his answer. Too low and you might not have time to deploy parachute.
Sea state
Time of day. You might want to touch water at a lower speed if you can't see it.
Position of allied forces and/or shore. Surviving the crash is one thing; being rescued a whole other.


Why doesn't the A320 pack flow indicate HI as it should? When on ground with APU bleed on and both engines off I have noticed a number of times that the pack flow isn't at the HIGH setting why?

As per the FCOM it states that when APU bleed is on the PACK FLOW automatically goes to the HIGH position regardless of the PACK FLOW selector position. But a number of times I have noticed on the BLEED SD it doesn't indicate HI even though both PACKS are on why? Is there any reason for this or some system particularly I don't understand?

From FCOM §Air Conditioning - Controls and Indicators:

  The pack flow indication can be up to 30% below the actual flow rate.

That's why the needle may not be at the HI position. LO to HI is 80-120%, with normal being 100%.

The aforementioned needle (YouTube).

The sensor responsible for sending this data is the delta P (differential pressure) sensor at the inlet of the FCV (flow control valve). My guess is that it is not designed for a precise reading, but only an indicative reading.


Which channels to listen to on liveatc concerning arriving flights? For fun, I decided to watch arriving aircraft to airports on flightradar24.
Now, what I'd like to do also is simultaneously listen to ATC traffic concerning these incoming flights.
I've found Liveatc.net and, for example, there're plenty of choices of channels for JFK airport.
Which channel should i listen to if I'm interested in the radio exchanges concerning holding patterns and final descents? Is this handled from the tower?

(If JFK isn't a good example, feel free to recommend any other airport, European airports preferred. I tried LHR, FRA and CDG but it seems they aren't covered by liveatc.)

So, the more general question is: how are the channels labeled on liveatc that are about holding patterns and approaches?

If you want arrivals the relevant feeds on live ATC are:

NY app (CAMRN)
NY app (ROBER)
NY app (FINAL)
KJFK Tower
KJFK Tower #2
KJFK Tower 119.1
KJFK Tower 123.9

CAMRN will receive approaches from the south and ROBER will receive approaches from the east. They will then pass planes to final to be lined up to the runways. Final will then pass planes to the appropriate tower frequencies, depending on which runway they are assigned. There are two separate tower frequencies of which there are two separate feeds. Items 4 and 5 are both frequencies combined (usually one in the left ear and one in the right) from the two different frequencies. The feeds are done by volunteers so there's no way to know their location. I haven't listened to KJFK so one feed might be better to hear planes from different directions. Feed #1 includes the TCA. I find it daunting to hear two feeds at once so I would recommend using either 6 or 7.

To be honest, unless there's something unusual going on, tower feeds are pretty boring. By the time they get to tower freq they are done maneuvering and are established on final. All tower does is clears them to land and and gives them exit instructions. If you are watching FR24 the approach feeds are more interesting.

Another interesting approach to watch, at least for me, is KMEM between about 2230 and 2330 Central time when all the FedEx flights are coming in to the hub. Gives you a good idea of the flow of ATC.

As Dave mentioned in comments, none of the UK airports will be on LiveATC for legal reasons.


Is the climb rate different for short-haul flight and long-haul flight? A short-haul flight does not spend much time in its cruise level (let's say less than two hours). Thus, it is important to rapidly reach the optimal flight level and I think this kind of aircraft should be optimised to climb. On the opposite, on long-haul flights there the climb and descent reprsent a tiny portion of the whole flight. The aircraft should then be optimised to consume as little fuel as possible during cruise, even if climb rate is less important. That's why I wonder if my thinking is right and if there are significant differences in climb rate between short and long-haul aircraft.

Related thinking: On average, does a short-haul flight descent more rapidly than a long-haul? I think not as this diving has no reason to be related to climb/cruise performance and all commercial aircraft are made to use the same airports with the same approach pattern; but that's only an assumption.

EDIT: OK, the quantity of fuel is quite important. I suppose an aircraft designed to be heavier (long-haul, carrying lots of fuel and payload) is equipped with more powerful engines and thus if it is lighter than designed for (lets say a B777 or a A330 used on short-haul flights), it climbs faster than the same aircraft in a long-haul flight. But the long-haul aircraft is designed to make long-haul flights. Maybe I should have asked if there is a significant difference in climb rate between short and long-haul aircraft at their maximum operating take-off weight.

Different climb performance is indeed indirectly linked to the length of the trip, but this has to do with the number of engines. All airliner's engines are sized to support flying with an engine failure right after take-off. Twin-engined aircraft enjoy slightly less stringent rules, but will basically carry twice the thrust that they need to stay aloft, so more excess power is available than in four-engined aircraft, which have only 33% excess thrust.

Generally, the best performance is achieved when running the engines at their maximum continuous thrust setting and when climbing as fast as possible. That is the reason why an A-320 or a Boeing 737 will climb faster than an Airbus A-340 or a Boeing 747. On descent, the number of engines is less relevant, so the descent speeds of all types are similar.

The link between engine numbers and range was strongest in the early jet age; now it is less clear-cut with long-range airplanes like the Boeing 777-200 LR or short-range airplanes like the BAe 146.


Do airliners or business jets have brake temperature sensors? Reading the question found here: Do some aircraft lower the landing gear mid-flight

Some of the replies got me curious... Do heavy jets or even business jets have brake temp sensors or indicators?

In the fast-movers we don't have this luxury and I've never even heard of it until now.  If we suspect hot brakes we just taxi to the hot brakes area and either wait or ground egress if a fire may occur.  We do have wheel speed sensors with anti-skid brakes that use different channels, but nothing that reports to the pilot the brake temperature.

If you guys do have this feature, do you have a indicator that shows brake temperature?  Or is there a light that illuminates or even a PFL (pilot fault list) that appears on one of the MFDs?

Brake temperature sensors are quite common on airliners. Turnaround times of large aircraft are often impacted by the required cooling time. This is because during take-off the brakes must be cool enough to absorb the heat of a possible rejected take-off.

Brake temperature and tire pressure indication on the Airbus A330 (note the deflated tire & high temperatures)
Source: Karlene Petitt blogspot


Can hours logged training to be a Sport Pilot apply toward the Private Pilot Certificate? Can my training in a Sport aircraft with a Sport instructor be used to fulfill the requirements to become a Private Pilot?

As an example, assume I've started my training to be a Sport Pilot, but decided I'd rather be a Private Pilot.

Absolutely, you can log just about any flight time in an aircraft!

The definition of flight time is in 14 CFR 1.1 and says:

  Flight time means:

  (1) Pilot time that commences when an aircraft moves under its own
  power for the purpose of flight and ends when the aircraft comes to
  rest after landing; or

  (2) For a glider without self-launch capability, pilot time that
  commences when the glider is towed for the purpose of flight and ends
  when the glider comes to rest after landing.

However, the instruction logged towards a sport pilot rating by a flight instructor certificate with a sport pilot rating (61.413) may not be used toward the requirements of the private pilot certificate.

If the instructor is a CFI certified under 61.181 then the instruction may also be used towards your private pilot certificate but you will need to be proficient to the higher standards, which may require additional training.

For those who already have their Sport Pilot Certificate, take a look at this question: What does a sport pilot have to do to get a private pilot certificate?