Is the arrival segment of an IAP in PANS-OPS the equivalent of FAA's feeder route? In ICAO's manual 8168 ("Aircraft Operations"), the term "Feeder route" is never mentioned. Instead, it states:

  8168 Volume II, "Approach Procedures": 1.2.3. Segments of the approach procedure. An instrument approach procedure may have five separate segments. They are the arrival, initial,intermediate, final and missed approach segments.

My confusion concerns the difference between the arrival segment and a STAR. Does the arrival segment imply that it is also part of an arrival procedure, or is it just the equivalent of a feeder route, which is mentioned in FAA's TERPS?

Could someone help me clarify this?

An arrival segment can be part of both an arrival route and a designated STAR. Both are protected with the same design criteria.

The STAR chart consist of designated routes linking the approach procedure with ATS-routes or exit points in Free Route Airspace (FRA). An arrival route is simply a collection of arrival segments which are not part of a STAR when it is not operationally necessary to publish the route using the STAR criteria in ICAO DOC 8168 Vol. II Part I, Section 4, Chapter 2. The non-STAR arrival routes are published on the Instrument Approach Chart (IAC) as part of the Instrument Approach Procedure (IAP).

Here is an example from the Norwegian AIP:

The dotted lines from AND, SJA, FS and EVD to the IAFs are arrival routes containing arrival segments. These are the eqvivalent to feeder routes in TERPS, as they are defined equally.


In what circumstances do passengers or flight attendants have to take their shoes off? Three shoes-related facts:

A passenger and a flight attendant in this Аэрофлот/Aeroflot aircraft have their shoes off or are ready to take them off:

It's suggested that shoes are taken off for evacuation.

In United 93 film, an attendant can be seen seated in the jump seat without her shoes during the climb phase.

I'm wondering whether there are safety policies applied here. What are the regulations, policies or best practices about:

Crew taking off shoes in critical flight phases?
Passengers asked to take their shoes off?

In case regulations strongly vary by country, US/Russia/EU can be taken as examples.

Passengers are usually asked to remove their high-heeled shoes during an emergency evacuation as they may damage the slide. In other cases, it is better to leave the shoes on during emergency as once you are outside, you're worse off without them. The usual policy is to remove only the high-heeled shoes. For example, FAA says:

  FAA Policy. The FAA believes that the proper procedure regarding shoes during an aircraft evacuation is to leave them on. In the case of a forewarned evacuation it is desirable to remove high-heeled shoes and stow them in an approved stowage area such as an overhead bin. They should not be placed in the seat pocket.

This was the result of cases where the passengers sustained injuries while evacuating as they wore no shoes. For example, during the crash of Southern Airways Flight 242, the NTSB noted:

  The feet of a number of the survivors were cut and some were also burned because they had no shoes for protection. In accordance with standard evacuation procedures, the flight attendants had briefed the passengers to remove their shoes to prevent damage to evacuation slides.

  Had pillows and blankets been distributed and had shoes been worn, some of the passengers' injuries probably would have been less severe and more passengers probably would have been able to escape from the wreckage.

As for removing the shoes during flight, some regulatory authorities are against it, like the Australian Civil Aviation Safety Authority:

  The most common injuries to feet during accidents or emergencies can be prevented by wearing suitable footwear. ... Avoid sandals and high heeled dress shoes. Keep your footwear on during the flight.... High heeled dress shoes will have to be removed before using the escape slide.

As are some airlines, like the American Airlines:

  American may refuse to transport you, or may remove you from your flight at any point, for one or several reasons, including but not limited to:

  ...

  Are clothed in a manner that would cause discomfort or offense to other passengers or are barefoot.

I understand that there was an old rule to this effect, at least in US. Having the shoes on and taking them off both have their advantages and disadvantages. Except when challenged by a FA, I guess you can have/remove your shoes as you like (As long as the one sitting next isn't complaining). If the cabin crew asks though, its better to comply.

As far as the cabin crew is concerned, I'm not aware of any rule which says when they have to remove their shoes, so I guess its upto them, though it would be better for them to leave it on so as to take care of any sudden requirements. IATA recommends shoes which won't come off easily:

  Cabin Crew Uniforms

  ... The  following  is  intended  to  serve  as  a  guideline  for airlines
  when selecting new uniforms for their cabin crew:

  Shoes or boots should be flat or low-heeled and closed with laces or traps so that they will not be lost or thrown off;

Interestingly, this forum indicates that some airlines (including Aeroflot) require their FAs to wear high heels outside aircraft, which are changed to slip-ons (or other manageable ones) once in aircraft. From a news article:

  ... female flight attendants working for one of the world’s largest carriers, United Airlines, are required to wear shoes with a heel height of between one and three inches. Women crew members can only switch to a lower heel—it still has to be at least one-fourth of an inch high—during the service portion of the flight. ... Female attendants then have to switch back to the higher heels once the flight begins its initial descent.


How many active pilots are there in the US? How many are women? How many active pilots are there in the US?  Also, how many active flight instructors are there?  Out of all of active pilots and flight instructors how many are women?

According to the FAA, as of December 31, 2016, there are:

584,361 Active pilots (39,187 are Women pilots, or about 7%)

104,382 Flight Instructors (6,848 are Women Flight Instructors, or about 7%)

The ratio of female instructors to female active pilots is virtually the same as for males.


Where can I find examples of ADS-B surface (ground) position data? To check my decoding it would be helpful to have some correct reference data for checking input and output as follows:

Input: 19-bit Compact Position Reporting (CPR) even latitude and longitude / odd latitude and longitude (decimal values are OK)

Correct output: Latitude and longitude in degrees (decimal)

Where can I find sample data that I can use for testing?

The best source for that data would be EUROCAE Document ED-102A or RTCA Document DO-260B. These are the Minimal Operational Performance Specifications for ADS-B on 1090MHz. They include all the requirements on the ADS-B transmitter, including test data to demonstrate that the requirements are met.

However, if you don't have access to those documents, you can try and receive some ADS-B messages from aircraft on the ground using an ADS-B receiver and decode those. If the surface position messages indicate good position integrity (format type code 5, 6, 7 but not 8) and the decoded positions appear on airport paved surfaces consistently than you are sure that you've got it right.

Note that ADS-B surface decoding is not globally unambiguous; you need to know where approximately the receiver is (as in which N/S,E/W hemisphere) to unambiguously decode the surface position message.

The table below shows some encodings that can be used to verify wether your surface CPR decoder works.

The first four columns show latitude and longitude (in decimal and 32 bit angular weighted binary hexadecimal notation), the next 6 columns show the CPR data.
\begin{array}{|c|c|c|c|c|c|c|c|c|c|}
 \hline
 \text{Latitude}&&\text{Longitude}&&\text{Lat.}&\text{Lon.}&\text{NL}&\text{Lat.}&\text{Lon.}&\text{NL}\\
(Decimal)&(HEX)&(Decimal)&(HEX)&(HEX)&(HEX)&(Dec.)&(HEX)&(HEX)&(Dec.)\\
 \hline
-27.93897726&EC21DD4A&153.00998&6CCE9DE7&0BF7F&03636&53&15E70&0CFC1&53\\
\hline
27.938976&13DE22A7  &45.0000&20000000&14081&10000&53&0A190&00000&53\\
\hline
\end{array}
source: EUROCAE ED-102A , table 2-214 (truncated), page 699


What is pendulous suspension in magnetic compass? I am not able to understand what is pendulous suspension and how centre of gravity and centre of suspension are related in magnets and their errors. Can someone explain this in layman language or could share the link which gives good 3d animation of the same.

This video covers it pretty simply.  The compass magnets are attached to the bottom of an upside down cone, which is resting on a spike.  The weight of the compass magnets, and the center of gravity of the assembly as a result, is near the bottom of the cone and the "hang point" is up near the top at the tip of the spike.
It's a cone pendulum; basically a lady in a hoop skirt, out on the dance floor (put a couple of bar magnets alongside at at the bottom of the skirt, stick her in a vat of kerosene to dampen the skirt's movements, and there's your compass-lady).
The pendulum arrangement keeps the compass magnets more or less level to the earth even if the spike it's on is tilted (mostly to accommodate changes in pitch attitude with speed and stabilized climbs and descents), within the range of movement of the cone.  Compass units in ships (and very early aircraft compasses) achieve this by having the compass float on water (or some other fluid) within the housing so the compass can stay horizontal while the ship pitches and rolls.
The various turning errors relate to how the pendulum reacts to accelerations and apparent gravity (think of the lady's hoop skirt tilting off vertical as she starts to move, for example), the C of G of the cone being below the hang point, while at the same time having the magnetic alignment forces acting on the magnets. The result is readings that wander in specific directions (acceleration/deceleration and turning errors) if there are any lateral accelerations going on, and while the magnets are rotating, because of the "struggle" going on between the magnetic forces and the inertial forces.  The compass reading is only valid when the inertial forces have gone away, when there is a steady state condition of no turns and constant speed.


Why local(section) lift coefficient(CLL) is higher near the wing tips compared to the root on untwisted tapered wings and untwisted swept(aft) wings? Why local(section) lift coefficient(CLL) is higher near the wing tips compared to the root on untwisted tapered wings and untwisted swept(aft) wings?

I know that in an elliptical wing(untwisted) the absolute angle of attack is the same in all the wing span so, the reduction in lift is 'proportional' to the reduction in area/chord of the section and then the CLL is equal in all the wing span.
I also know that in a retangular wing(untwisted), the effective angle of attack(due to the tip vortex) causes a reduction in the CLL in the tips compared to the wing root.

Even that I understand the flow pattern over swept wings(Attachment line/Spanwise airflow and it's effects on lift and in the boundary layer, adverse pressure gradient and tip stall)I just can't figure out, intuitively, the relation between this flow pattern and the increase in the CLL in the direction of the wing tips.

[ CL = L / S.q ]  Seems to be too simplistic to analise this particular case.

For the swept wing, as you go out along the wing, each section of the wing is effectively flying in the upwash of the tip vortex of the section immediately next to, and inboard of it. So, each section has its angle of attack increased by all of the sections inboard of it. The root section, of course, does not have anything inboard of it, and the tip section is affected (to at least some extent) by all the sections inboard (and ahead) of it.

Birds fly in V-formations to take advantage of this effect. Each bird is flying in the upwash of the tip vortex of the bird ahead and toward the center of the V, and is thus "flying downhill" aerodynamically.

But, that upwash increases the angle of attack, and the effects add up as you move outboard, until they reach a peak effect near the tip.

You can really see this on hang glider wings: if you stand next to one as it's about to take off, you can see the tips appear to be at a negative incidence relative to the wind, and yet they are lifting, because the wing sweep increases their local AoA.


Does the Cessna POH state the fuel consumption in Imperial or US Gallons? I'm planning a trip in a Cessna 182T and was calculating fuel requirements and started wondering. I have always assumed that fuel consumption is in US Gallons (or 3.785 litres) but I can't find a section in the Pilot's Operating Handbook (POH) that really confirms this. The fuel tank capacity is expressed in USG so I reckon it's close to assume that this implies that GPH is US gallons per hour.

There is a Imp. Gallon to Liter and Imp Gallon to US Gallon conversion table in the POH, when do we need Imp. Gallons?

Any comments, did I miss something?

The plane was certified with US Gallons. Use those for fuel consumption.

The conversion tables are there in case your FBO's fuel pump is calibrated in L or Imp Gal.


Why aren't airliner windows aligned with their seats? On a recent airline flight, I noticed that the spacing of the plane's windows was different from that of the passenger seats: some of the rows had a window directly in line with them but for others, the windows were partially obscured by the seatbacks in front or behind.

Is there a reason that the windows aren't manufactured with a regular spacing to align with the seat rows? Does it have to do with the fact that different airlines may be using different seating configurations for the same model of aircraft?

Because the pitch of the frames is not related to the pitch of the seats. The windows placement have to cut through as few frames as possible.

You can see it in the following picture, noting that frames are "highlighted" by the vertical riveting

Image source

It is even more evident in the picture contained in this answer on UX.SE:

Because the aircraft is designed once, but "decorated" by several airlines in several different manners. For example, an A320 or a B757 will have the windows always in the same locations, but depending on the airline that is using it, it will most probably have the seats in slightly different locations.


How close can I fly to a bridge? I want to take some pictures of a bridge. How close can my pilot get me?

If operating under VFR rules, which your pilot probably is if he's attempting to stop you actually hitting the bridge in question and allow you good enough visibility to take a photograph in the first place, the rules vary slightly by location.

The FAA regulations will be as follows (Note: all emphasis mine - indicating what I believe is the interpretation of your bridge)
:

  An aircraft must maintain an altitude of 500 feet above the surface [and], the aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure.

and

  An aircraft must maintain an altitude of 1,000 feet above the highest obstacle within a horizontal radius of 2,000 feet of the aircraft over any congested area of a city, town, or settlement

Also note that helicopter rules differ slightly.

  Helicopters may be operated at less than the minimums prescribed in [the previous quoted sections] if the operation is conducted without hazard to persons or property on the surface.

source: 14 CFR 91.119 - Minimum safe altitudes: General.

And the UK CAA rules are similar

  An aircraft must not fly closer than 500 ft to any person, vessel, vehicle, building or structure.

and

  [...] it must not fly less than 1000 ft above the highest fixed object within 600m of the aircraft.

So, in summary your pilot can get you within 500ft if it is an uncongested area, 1000ft if its a congested area - closer if he's got a helicopter and can do it without causing a hazard.


Would an Aero L-159 Alca air frame be able to withstand a supersonic engine? Aero L-159 uses a  Honeywell F124-GA-100 turbofan engine.

First question is, can it be fitted with any modern supersonic jet engine?

If YES, why isn't Aerovodocody doing that?

If NO, why?

By 'supersonic jet engine', I presume you mean an engine which would make an L-159 capable of supersonic flight.  Could you mount such an engine on this aircraft?  Possibly, but why would you want to?

An L-159 isn't exactly engineered to be a top of the line high performance fighter; its design and intended use is as an advanced subsonic trainer aircraft based upon the earlier L-39 and L-59 airframes.  Its job is to prepare student pilots for more advanced tactical aircraft and has handling qualities similar to fighters while retaining forgiving flight characteristics for new students so they can more easily build time and experience in high performance jets.  In addition, the aircraft is designed to be affordable and easy to maintain for third world air forces.  Supersonic flight never was considered as a requirement for the role by Aero Vodochody.  Therefore a much more expensive and exotic engine is not needed here.


What does the small fan do that is visible on Boeing 787 Dreamliners on landing? When watching landing videos of 787's that are in service I've been noticing a fan that is located under the right rear section of the fuselage.  I've now seen it on 4 different 787's  from 4 different airlines.

Is this an emergency fan that's deploying, or is it just something that's designed to recharge some of the batteries on board?  Some auxiliary type of system, perhaps?

If you are speaking of the small fan behind the gear in the photo below (click to magnify)

Image from here.

you are speaking of a Ram Air Turbine, usually used in an emergency, not in normal operations.


Is "11/2SM" a typo in this TAF message? In a TAF-message downloaded from NOAA I came across "11/2SM" as the reported visibillity. I have previously seen "1 1/2SM" which I've been told to read as 1.5 SM.

is "11/2SM" a typo (should it have been "1 1/2SM") ?
Should it be read as a fraction "11/2" = "5.5" ?
Should it be read as "11+1/2" = 11.5" ?

Edit: Entire TAF (look 4th last line):

CYYZ 090839Z 0909/1012 31015G25KT P6SM FEW020 BKN050
TEMPO 0909/0913 P6SM -SHSN BKN020 BKN050
FM091300 29018G30KT P6SM -SHSN BKN025 OVC080
TEMPO 0913/0920 4SM -SHSN BKN020 OVC080
PROB30 0915/0920 11/2SM -SHSN
FM092000 31020G30KT P6SM -SHSN BKN025 BKN080
FM100100 33020G32KT 6SM -SN BKN020
FM101000 33018G28KT P6SM BKN020 RMK NXT FCST BY 091200Z

According to NOAA, there should be a space between the whole and fractional parts.  But they would never use a fractional part greater than 1, so your example must be a typo and should have read "1 1/2SM".


Why does flying IFR require a rating? It may seem like a silly question, but my analogy is, some countries issue automatic-transmission-only driving licenses. Automatic transmission in this case would be the powerful avionics now available for GA aircraft.

So I think it's a valid question a non-pilot might ask.

A non-instrument rated pilot already knows how to navigate, how to use the instruments, radio, and autopilot.

So why aren't they allowed—in a properly equipped plane especially nowadays—to deliberately (with permission) fly into IMC, or file an IFR flight plan?

(Image source)

The short and sweet answer to this question:  That kind of thinking is what kills a lot of pilots.

A non-instrument rated pilot may know how to fly and navigate but does not yet have the skill to do so in total reliance upon instruments.  A PPL does require you to have at least 3 hours of simulated instrument flying with an instructor.  That may keep you alive in straight and level flight if you enter instrument conditions inadvertently, but it's not going to be adequate for conducting an entire flight in IMC.

This quickly becomes clear to new students pursuing an instrument rating who go for their first filed IFR flight in hard IMC with an instructor.  Once you enter a cloud, you go into a world of brilliant white (day) or inky black (night) and there is absolutely no visual references to follow.  You must be able to stay on top of that airplane, manage all of its systems, communicate with ATC, fly departure and approach procedures correctly, and handle emergencies, all without the benefit of visual reference.  In addition instrument flight has a nasty habit of inducing sensory illusions and spatial disorientation due to vestibular sensations causing the pilot to incorrectly judge the aircraft's attitude, etc.  You will be surprised the first time that you fly in real IMC just how STRONG the urge is to trust your vestibular senses over cockpit instruments and you can start doing this unconsciously when you start getting saturated and overloaded with cockpit tasks like terminal environment workload, emergencies, and delays and holding.

A number of pilots - good ones too - are now dead because they did not take this seriously.  One notable high profile case was John F Kennedy Jr., who inadvertently entered instrument conditions during a flight from Essex County Airport in NJ to Vineyard Haven, MA.  Even though the entire flight was in VMC, dark night over water provides no visual references for the pilot.  Kennedy became spatially disoriented; his PA-32 Saratoga entered a tight spiral and crashed into the ocean.

When I was prepping for a solo CC with an instructor for my PPL (the flight was scrubbed due to weather that day) I watched a guy take off in a PA-32 Saratoga and kill himself by flying into inclement weather.  The weather for that day had 600 ft ceilings and poor visibility.  He attempted to scud run under the deck, became spatially disoriented and flew into an antenna park near the Arkansas river.  The plane was sliced in half by a guy wire and crashed.  The pilot was not instrument rated but filed an instrument flight plan, departed KRVS with a clearance, then deviated from the flight plan and attempted a scud run.  His desire to fly his family down to Dallas to see a college football game in bad weather without proper training for it killed himself, his wife, his two teenage daughters and a family friend.

It takes a lot of practice to successfully fly in IMC.  The FAA required instrument ratings for pilots to conduct instrument flight due to the high number of accidents associated with inadvertently entering IMC or worsening weather conditions without competence in instrument flight.  Over 80% of these kinds of accidents result in fatalities.

In addition to requirements to becoming rated for instrument flight, per 14 CFR §61.57, the FAA also has currency requirements to maintain instrument proficiency.  You are required to have executed at least 6 instrument approaches, holds and navigation by electronic nav systems within the preceding 6 calendar months.  This currency work must have been done in either real or simulated instrument conditions.  Once that expires, you do have an additional six calendar months to complete this currency work with safety pilot.  If after 12 calendar months you have not maintained this instrument proficiency, you must undergo an instrument proficiency check with a CFII.

UPDATE - in regards to advanced, modern avionics in the cockpit, back 18 years or so ago when I was a young engineering student and the industry was beginning a transition from traditional structural analysis calculations done by hand to using computer aided finite element analysis programs, a college professor of mine once made a comment that always struck me as very applicable to advanced integrated flight decks.  He said that these new FEA programs had the capability to make a good engineer better and a poor engineer dangerous.  I’ve always viewed modern glass cockpits in the same fashion and accident statistics on this seem to bear it out as well.  Glass cockpits and modern avionics can improve your ability to fly an aircraft, reduce pilot workload and fatigue during critical times but they can get you into a lot of trouble as well.  There have been many cases where pilots have run out of fuel and crashed or had a fatal CFIT simply because they did whatever the screen told them without being able to critically think about what information they were receiving and cross checking it to see if it made sense for a given situation.  Autopilots and autothrottles, too, are useful for relieving the routine grunt work of flying, but can result in emaciated stick and rudder skills, which will be needed in critical moments should an AFCS fail.

An instrument rating is nothing more than a journeyman's license to practice instrument flight.  One should always be aware of this and approach the process of planning an instrument flight accordingly.  All it takes is one harrowing incident to really scare you up and make you aware of you own human limits and mortality.  Set personal minimums for flight conditions and approaches well above published minimums and periodically evaluate these as you continue to build experience.  Never fly an approach into an unfamiliar airport or one surrounded by mountains or other hazardous terrain until you have done so in visual conditions and practiced the approach on a day VFR flight.  Be wary of the differences between flying IMC in day or in nighttime.  Be cautious of instrument flight in busy airspace eg the SoCal Class B areas, etc.  These are just a few of the additional challenges and hazards you need to consider before you venture into darkened skies...


For a plane with a pusher propeller, how does a root-stalled wing affect its performance? My understanding is that it is desirable for the inboard part of the wing to stall first to maintain aileron effectiveness.

For the configuration shown below, if the inboard part of the wing stalls first, what would the effect be on the propeller performance? Is there an equation that estimates the effects?

Source: https://en.wikipedia.org/wiki/IAI_Heron

Interesting question. Its far easier to find studies which focus on effect of propeller on the wind aerodynamics. I highly doubt there would be any analytical equation that can give effect of stalled wing on a pusher prop. For one thing, stalled airflow goes out of the realm of what analytical aerodynamics can handle. Even for having an empirical equation, since the stall is highly irregular phenomenon, it would be very difficult to arrive at any empirical equation which can give reasonable correlation for wide enough envelop of wing-pusher configuration. The impact would be highly sensitive to geometric configuration parameters such as location of propeller with respect to centreline, distance from trailing edge and so on. For a specific configuration, one perhaps could come up with a correlation but that would need a good amount of experimental data and it would be of limited utility.

In my opinion, the impact of the stalled wing on the propeller performance is far less than the impact of the propeller on the wing stall. Definitely there would be some impact on the performance on the propeller due to "dirty" incoming airflow on the pusher propeller, but the impact should be small. I base my expectation on the fact that the streamwise velocity would be still much higher than the cross-stream velocity components in the stalled airflow behind the wing, thus giving marginal changes in AoA that the propeller blade aerofoils see. This particular research paper say this in the conclusion:

  The prop-wash effect mainly increased the aerodynamic performance of the wing, but the wing–wash effect was just a small part of this interaction. However, the wing-wash effect cannot be ignored as also mentioned in previous study.

Note that this is valid only for lower Re regime for the particular configuration studies. But I would expect results not too different in other cases.


Are the functions of ailerons and rudder similar? The ailerons help the plane to bank left/right by increasing lift to one wing and decreasing in another. Likewise, the rudder also helps in turning the plane by yawing and deflecting the nose right/left. So their performances sound quite similar(i.e. to make a turn)? Then, why should we keep both of them?Like in a ship or motorboat there is a rudder only and no ailerons.Are ailerons present for quicker operation and rudder for extra support and stabilization only?

Short answer:
Rudder and ailerons have different purposes and control rotation about two different axis. However a rotation about one axis induces a usually unwanted rotation on the other one. In order to rotate exclusively about the desired axis, the other control must be used to cancel the secondary rotation. This is called coordination of controls.
Rudder and ailerons are not the only controls requiring coordination, elevators and throttle actions must be coordinated too, to prevent a change in altitude to result in a change in speed and vice-versa.
The rudder is mostly used to:

Limit yaw movements for safety (Dutch roll) and comfort.
To force the aircraft in a crab (heading not aligned with course), while the weather vaning effect tends to orient the aircraft with the airflow (e.g. for a cross-wind landing).
To force the aircraft to face the airflow when performing a turn. We'll talk about this below.

See Understanding the use of rudder for a more comprehensive explanation.
Ailerons are used to turn, but for a non-small turn an unwanted adverse yaw, opposite to the turn, develops and moves the aircraft away from the airflow (crab), the rudder is used to cancel this crab angle and make the aileron-initiated turn effective.
The availability of a yaw damper relieves the pilot from the duty of coordinating rudder with ailerons in a turn. The yaw damper controls the rudder for stability purposes, and at the same time it maintains the aircraft longitudinal axis into the relative wind without pilot action.

Detailed answer
While it is intuitive to think a turn is triggered by yawing the aircraft and keeping the wing horizontal (like a car), this method is actually ineffective with a rudder of the normal size. The rudder forces the aircraft to change its heading (yaw) but the flight continues more or less in the same direction, the aircraft now moving crabbed. This is specially true as speed and altitude increase and rudder aerodynamic force becomes smaller compared to other factors like inertia.
Banking turns the aircraft
An aircraft is turned by rolling (banking) the wing. When the aircraft spins about the roll axis, the direction of the lift is changed (A/B below). Like any force, the lift vector can be broken down into components (B):

The horizontal component of the lift moves the aircraft away from its original path and the aircraft turns around some point. (Note the vertical component, which still opposes the weight, is now smaller, and a non-small turn also requires adding engine power to maintain altitude.)
However something quite undesirable happens (C): To roll the wing, the upper aileron has to create more lift than the lower one. Lift is created by deflecting the airflow, and this action has a cost: The disturbed airflow creates 'induced' drag. This drag is different from the other drags, it's not due to the friction or the shape of the aileron, but to the deflection of the airflow by the aileron, and increases with the amount of lift created.
Like aileron lift, aileron induced drag is larger on the upper wing, that is on the outer side of the turn. As there is a drag differential, the wing is no more balanced and wants to yaw on the right, opposite to what we want. This force is known as the "adverse yaw".
A part of the adverse yaw is balanced by the weather vaning tendency of the aircraft, due to the action of the fuselage and the rudder. However this only compensates partially for the yaw. All these forces makes the aircraft turn a bit, but crabbed, as seen in picture D. This situation where the aircraft is not aligned with the airflow is an "uncoordinated turn", it is very inefficient, slows the aircraft and stresses the airframe.
This is were some action on the rudder is required: The pilot adds some left rudder to completely cancel the adverse yaw created by the ailerons and align the fuselage with the airflow (E). Doing this any slip and skid motion is also minimized. This is known as performing a coordinated turn.
As visible on the figure E, the horizontal component of the lift, the one pulling the aircraft towards the center of the turn, is constantly reoriented in the direction of the center, contrary to the case of the uncoordinated turn (D).
Rolling the wing is a very effective way of turning the aircraft, but needs some rudder correction to account for the induced drag moving the aircraft longitudinal axis away from the airflow direction.
Ailerons deflection reduced in the turn
Note that when the desired bank angle is reached, the pilot reduces the ailerons deflection. The excess of lift and drag on the upper wing decreases too, as does the adverse yaw. The rudder deflection can be reduced too.
Normally the aircraft should maintain its bank and continue to turn with ailerons in neutral position, due to the upper wing flying faster and generating more lift.
However the aircraft in a rolled attitude actually slips into the turn and the dihedral effect tends to decrease the roll angle of the slipping aircraft (roll stability). So some degree of aileron deflection will be maintained.
The ailerons (and the rudder) are used to return the wings to their horizontal position and stop the turn more accurately.

Ailerons-rudder coordination
Coordinating turns is part of the basic training for a student pilot as uncoordinated turns are not only ineffective, they are also unsafe:

Some part of the wing or the controls can be in the shadow of the airflow, meaning they have no useful effect to control the aircraft.
Lateral accelerations develop, the aircraft either slips or skids.

The amount of rudder to apply can be determined using (human senses and) different instruments, including the turn coordinator, aka needle and ball Indicator, which is a sort of level (the ball) usually associated with a bank or rate of turn indicator (the needle). The respective position of the ball and the needle according to different uncoordinated/coordinated situations are like this:

(source)

(source)
When executing a coordinated level turn without wind, at sea level, etc, the radius of the turn and the turn rate depend only on the airspeed and the bank angle:

TAS 150kt, bank 20°: Radius 1,676m, 360° in 2:16.
TAS 300kt, bank 30°: Radius 4,227m, 360° in 3:51.

See this question for additional information.
Yaw damper
In commercial airliners, the yaw control is assisted by one or two yaw damper(s) which function is to increase the yaw stability and prevent the development of the dangerous Dutch roll. Thanks to the yaw dampers, the pilot does not need to use the rudder pedals for coordinated turns.

(source)

Other means of controlling roll/lift
A mean of banking wings directly is required, including when Dutch roll and spin start developing and when flying or rolling with crosswind. But bank control can be obtained by other means than ailerons. While ailerons add lift by changing the camber of the wing,

spoilerons combine spoilers and ailerons, and break lift by disturbing the laminar airflow (B-52),

rudderons combine rudder and ailerons on flying wings (B-2A),

and now bleed air and Coandă effect can bank the aircraft without moving surface (Flaviir project).


Why shouldn't you use HF radio while refueling? FCOM limitations for many aircraft state:

  DO NOT USE HF RADIO WHILE REFUELING

Why is this? I have heard from people that it's because most of the big airliners have a 'notch' antenna for HF; it's a small notch cut at the base of the vertical stabiliser. HF transmission power is fed to this notch and the whole fuselage acts as an antenna,
radiating the power.

Can someone explain in detail and in simple terms?

The safest way to refuel an aircraft is with everything turned off and the airframe grounded (or bonded) to the fueling system.  This is often not practical (particularly for airliners), so a number of other rules exist to make refueling as safe as possible -- not using HF radio while refueling is one of them.

So why is the HF radio singled out? Power, combined with the antenna design factors you mentioned.

With small radios you can easily light a fluorescent lightbulb (incidentally this is why radio geeks are such great fun at parties). HF radios can put out several hundred watts of power - this makes them more likely to generate a spark that can jump the gap between say a refueling nozzle and the refueling port/tank, igniting fuel vapors and ruining everyone's day.
HF antenna designs which use the aircraft itself to radiate part of the energy can further increase the chance of a spark.


Why do TACANs not have a symbol for compulsory reporting on IFR Enroute Low Altitude charts? I am studying the IFR Enroute Low Altitude legend, and I noticed that all NAV Aids other than TACAN have a compulsory reporting point icon.

They do appear on the STAR/DP legend.

Why do TACANs not have a compulsory reporting point icon on the STAR/DP, but not IFR Enroute Low Altitude?

TACANs are for military use. VOR or VORTAC are the civilian equivalent.  Civilians can't generally tune in TACAN.

This wikipedia article has more details.  https://en.wikipedia.org/wiki/Tactical_air_navigation_system


How are altimeter settings estimated? So, I spotted another weird METAR from the same place that spawned the first one I asked about (it's a USAF base if you're wondering what kind of 'drome it is):

  K... 060846Z 00000KT 10SM OVC002 18/18 A2995 RMK AO2A SLPNO ALSTG ESTMD $

While I can reckon that the barometric pressure sensor there's on the fritz (again) from the SLPNO and the $, they also have the "ALSTG ESTMD" remark on there.  While the estimate looks to be not too far out, or at least more reasonable than the completely bogus figure from last time, it raises a question: how are they estimating an altimeter setting in the absence of the AWOS's barometer?  Or does it just mean that their backup barometer isn't as good as the one on the AWOS, so the altimeter setting might be a few ULPs out?

The instrument they are using is not certified, hence the ESTMD.  When they get a certified one, the ESTMD will drop off the METAR.

Technically, the primary certified instruments are inop or unavailable, so backup equipment, believed to be reliable, but not certified, is being used.


Which atmospheric factors that can affect the performance of an aircraft while flying a circuit? Which atmospheric factors that can affect the performance of an aircraft while flying a circuit?  Apart from the general wind shift.

In short, all of them. Environmental factors that affect aircraft performance do so whenever that aircraft is flying, regardless of whether you're flying a circuit, a straight line, or anything in between. The most important environmental factors include:

wind speed
wind direction
air temperature
air density
air pressure


Could flight MH370 have suffered decompression due to a high altitude bird strike? MH370 was flying at 11 km altitude at a speed of 872 km/h. It is known that some birds can fly at this altitude, e.g. the Rüppell's vulture. So, could such a bird hitting the windscreen at roughly 900 km/h cause cracks that would lead to decompression? And would such a scenario fit the known facts about MH370?

would such a scenario fit the known facts about MH370?

The evidence presented by the team searching for the aircraft includes

No voice communications using any of multiple radio systems available to cockpit crew.
Transponder ceased responding to secondary radar.
ADS-B transmissions ceased.
ACARS transmission ceased.
Aircraft made a change of course back across Malaysia
Malaysian military tracked an aircraft believed to be MH370 apparently following waypoints in the Malacca straights (suggesting another change of course)
Satellite data appears to show MH370 then flying to the south for many hours on autopilot until it ran out of fuel.

It isn't clear how a bird strike could disable the pilots and also cause the failure of all automated communication systems whilst allowing the autopilot (presumably) to make several turns and then fly the aircraft into the southern Indian ocean.

People have advanced many ideas about MH370. It isn't immediately obvious that this idea fits what is known any better than many of the other ideas.


How (and when) to use the BFO button on an ADF? BFO (Beat Frequency Oscillator) is a function of the ADF, I know that it has something to do with different types of NDB, but I do not know which type. And how and when do I use it?

I heard that depends on the type of emission of the NDB in use. For what I know there are N0NA1A or N0NA2A but I do not understand how this imply the use of the BFO push button or even the differences (from operational point of view) between the two!

Let me try to explain this from the radio perspective.

In a regular AM transmission (A3E emission type), you have a carrier and two side-bands. The usual receivers use the carrier to demodulate the audio information in the sidebands. The spectrum looks something like this:

Note: Horizontal axis is frequency, vertical axis is amplitude.

In real-life, it would look something like this:

Note: Vertical axis is time, with present being a the bottom, horizontal axis is frequency, increasing from left towards right and amplitude is encoded in color, with dark blue/black being low amplitude and white being high amplitude.

The two sidebands are the wavy-looking structures to the left and right and they carry the audio information. The carrier is in the middle and can be seen as the bright white line, especially visible during moments of silence.

When we want to send let's say Morse Code telegraphy over AM, we get the A2A emission type: Carrier and two sidebands, each carrying Morse code data.

Or in real-life something like this:

Here, we can also see the bright white carrier and the Morse code in the sidebands, with lower being a bit weaker than the upper.
Now, our AM receiver doesn't really know what's in the sidebands, the audio just goes to the speaker. So no special adjustments are needed to use a AM receiver for A2A emissions.

OK, so what does this have to do with BFO? Well, BFO is needed when we want to receive carrier-less data using regular AM receiver.

Let's now take a look at the spectrum of a A1A signal:

Or in real-life something like this:

There isn't much to see, only the "carrier". However, if we take a look at a real-life recording of the spectrum, we'll see that the carrier is being turned on and off, with no sidebands.

Now, when we input that to our AM receiver, we won't hear the Morse code. Depending on the receiver type, there might be an audible lack of noise when the carrier is on, but the expected tone is not there, since the sidebands are empty.

The BFO (Beat-Frequency Oscillator) helps us there. It artificially re-inserts the carrier, so combination of the re-inserted carrier and the A1A signal reach the receiver. The receiver thinks it's hearing a regular A2A or A3E signal and just outputs the received Morse Code tone. On the spectrum, we see something like this:

So the answer would be to use the BFO with A1A NDBs and not to use it with the A2A NDBs.

Possibly useful extras:

Why the name BFO?
When two sinusoidal signals, with frequencies A and B are mixed together, the result is a pair of new signals with frequencies A+B and A-B. This phenomenon is called Beating. In case of radio, if the signals are close together, the difference can drop down into the audio spectrum. For example, beating of 353 kHz signal with 352 kHz signal will result (among other things), in a 1 kHz signal, which we can output to a speaker.

A3E/A2A power and spectrum efficiency:
The carrier and one sideband do not participate in the actual transmission of information and are therefore wasted power. Newer systems try to avoid using them, when possible, also saving space in the spectrum. However, the carrier simplifies receiver design.

A2A variants:
Depending on the region, the A2A beacons might have the carrier on all the time, as shown above, or might key the carrier as well as the sidebands. Furthermore, some might only have one sideband, and save some power through that. Regular AM receivers can receive signal with a carrier and only one sideband. This is called Compatible Sideband.

J3E and BFO:
J3E, aka Single Side Band is a refinement of AM which is mostly used on high-frequency bands. It eliminates the power wasted in the transmission of the AM carrier and the other sideband and also uses less spectrum space, which is in shortage on the high-frequency band. On the other hand  the receiver and transmitter are more complicated. In aviation, the upper sideband is currently used. An AM receiver with BFO can be also used to receive J3E transmissions. Here's a spectrum of that:

A2A and BFO:
Not  coming from the aviation field, I don't know how the exact settings on the instruments work, so some of these might not apply due to precise offsets and audio filtering, but in general, if you re-insert the carrier on an A2A system, one of the following will happen:
The reinserted carrier frequency matches the original carrier. In this case, you won't hear any difference.
The reinserted carrier has a slight offset from the original carrier. In this case, beating will occur. You should hear the Morse code identification properly, but you might also hear a low-frequency sound in the background, if the system is capable of reproducing it.
The reinserted carrier has significant offset from the original carrier. In this case, you'll be able to hear both the original carrier and the Morse code identification. Note that the audio frequencies might be shifted in unusual ways, depending on where exactly the reinserted carrier was actually reinserted.


How much power is used by cabin lighting systems during flight? How much power is used by cabin lighting systems during flight when all the lights are ON?

Almost all lighting systems installed today use Light Emitting Diodes for weight savings, reduced power use and less maintenance. Compared to other aircraft systems, their power use is pretty insignificant. For the reading lights, I found the following quote:

  Passenger reading lights in halogen technology use 11 watts, while the
  latest LED products use only one watt. Source

The actual ceiling ceiling lighting power consumption seems more difficult to find. SAAB in a brochure for converting fluorescent to LED lights for their SAAB 340 & 2000 models states:

  Power consumption is reduced from 8 watts per 12 inch tube to just 5,1
  watts.

Emteq suggests savings of around 15% for LED compared to fluorescent lights, so SAAB's suggestion would be a bit more. This manufacturer quotes 10W for a 16-inch (40cm) LED strip running off the 28V aircraft DC system. Needless to say, power consumption depends on the wattage of light installed.


How does air conditioning work on a commercial airliner? I know a lot about airplanes, but I've always wondered the vents deal with air pressure in the sky

Came across this diagram that sums it up pretty nicely:

You get 'bleed' air from the engine compressor stage. On 'bleedless' aircraft, such as the B787, this is done by electric compressors instead.
Air temperature and pressure is adjusted as necessary in the conditioning packs since it heated up a lot when it was compressed.
Air is then distributed to the different 'zones'. A bit of the cabin air is recirculated.
Some areas, such as the cockpit, generally receive air directly from the packs without recirculating at a slightly higher pressure, to blow possible smoke away from the interior and to prevent smoke being recirculated into the cockpit. For the same reason, you try create a flow out through the baggage hold.

Here is a more complicated diagram from avsoft's website for a CRJ200:


What are the main components of the Airbus fly-by-wire system? Is ECAM related to FBW? I'm assuming that all commercial Airbus planes use a similar, if not identical, system. Can someone give me an overview of the parts of the Airbus fly-by-wire system?

I've also heard of ECAM. Is ECAM related to fly-by-wire?

ECAM and FBW are not directly related, but information and alerts regarding the flight control computers and actuators are displayed on the ECAM screens, like any other information not visible on the primary flight display or the navigation display.

Fly-by-wire

The fly-by-wire concept is actually simple:

In traditional aircraft, the control surfaces like ailerons or elevators are linked to the control inputs used by the pilot, e.g. the column. This link can be direct (cable) and/or amplified (hydraulic or electric actuator commanded by the pilot).

In "FBW" aircraft, the control inputs are instead sent to calculators which deliver actual orders to actuators. Each FWB system, in addition to introducing calculators into the pilot-control surface chains, also gets information from sensors to measure the aircraft response to orders (feedback).

This design has two advantages:

There is an actuator (e.g. an hydraulic jack), so the pilot (or the autopilot) has to exert on the control inputs only a fraction of the actual force that needs to be exerted by the actuators on the control surfaces.
More important for the concept, the calculator can supervise the pilot commands, so that the aircraft is never put in unwanted or dangerous configuration, e.g. stalled. This system is similar to the full authority digital engine control (FADEC) used for the engines.

The main calculators for Airbus A320 family are:

ELAC: elevator and aileron computer
SEC: spoiler and elevator computer
FAC:  flight augmentation computer
SFCC: secondary flight control computer

They are redundant and some functions dedicated to one computer can also be executed on other computers.

Source: Fly By Wire Systems Explained

Actuators are moved using a transfer function from pilot input. In simple words, some correspondence links the actuator deflection to the pilot input. These correspondences are usually named "flight control laws". Airbus uses 3 laws:

Normal: When everything needed by the calculators is available. Maximum protection is available. Sidestick inputs by the pilot are converted into vertical G-load demand and lateral roll rate demand.
Alternate: When some calculators required data are not available. Some protections may be lost and sidestick lateral inputs are converted into a direct equivalence in control surface deflection angle.
Direct: When no protection can be provided by the calculators, due to calculator failure, missing input, actuator or control surface failure. Vertical and lateral sidestick inputs are directly converted into a proportional surface control deflection. Basically the aircraft is a non-FBW aircraft.

ECAM

In parallel instruments in general have evolved from gauges to electronic displays. The elimination of the third crew member (the flight engineer supervising engines, fuel and other parameters) has led to automatic supervision of aircraft parameters and filtering of displayed information.

By default, only a few parameters are shown to the crew, other are replaced by alerts when something is unusual or requires attention. The crew has also the possibility to display parameters/status on demand, e.g. the status of the cabin doors or the fuel tanks. The electronic centralised aircraft monitor (ECAM) is just such system which monitors and displays alerts and important parameters.

A319 ECAM after an actual electrical failure, source

The ECAM system includes two displays that can be configured by the crew:

Source

Relation between FBW and ECAM

Airbus FBW reconfigures laws when one of the flight control computers has failed. Because knowing this reconfiguration is vital for the crew and it follows some failures, this leads to alerts, information and suggestions being displayed on the ECAM screen. However this use of ECAM is not particular to flight control computers.

ECAM indication of autopilot being off, and laws being changed, source

For more technical information about this topic, see question: Is a Control Law Degradation in Airbus Planes displayed on the ECAM?


Could airline tires be deflated in mid-flight to reduce weight? As a means of weight reduction to reduce fuel consumption, could the tires on an aircraft’s landing gear be deflated once airborne then re-inflated just prior to landing?  Is that feasible and safe?

You want to reduce weight by removing a few kilos of air, and adding an equal, if not greater, amount of kilos of pumps needed to reflate the tires (see David Richerby's answer for details), not to speak the additional costs incurred for periodically checking the correct functionality of said pumps, that would be marked a "safety critical" (because a landing with deflated tires would have really bad consequences) and require being checked quite often.
So, feasible maybe. Safe not really. Meaningful I don't see how, particularly when there is the risk of tire burst, as shown in this video linked by March Ho.
A lighter alternative would be to use bleed air from the high pressure section of the engine, but it would still probably(*) be heavier than the air you are pushing out (you need heavy duty pipes to transport high pressure air from the engines to the wheels), and not a good solution safety-wise: what would happen if you have to land without engine power?
(*): as user3528438 mentions in their comment, it would depend on the wheel size.
Additionally, this Goodyear manual provides insight in some other problems: (emphasis mine)

ALLOW 12-HOUR STRETCH AFTER MOUNTING

All tires, particularly bias tires, will stretch (or grow) after initial mounting.
This increased volume of the tire results in a pressure drop.
Consequently , tires should not be placed in service until they have been inflated a minimum of 12 hours, pressure rechecked, and tires re-inflated if necessary.

It means that the tire needs adjusting after being inflated, possibly removing the possibility of inflating and deflating it continuously (or, alternatively, you have to reinflate it at least 12 hours before landing). Note that this manual is written for current operations, that call for a replacement/inspection of the tire if pressure drops below 80% of nominal value. Procedures should be rewritten for inflation/deflation cycles, and this could be a factor.


Are there planes that can fly without wings? How would a plane be able to fly without wings? Are there any planes that can fly without wings? How do they produce lift? How do they control the attitude?

There is a certain class of aircraft that are lifting bodies, which do not have wings but instead rely on airflow over a peculiarly-shaped fuselage to generate lift. However, this method is very inefficient and requires high airspeeds to make enough lift to support the plane. This means that the plane would have to carry an enormous engine to propel it, and its takeoff and landing speeds would be very high.

Several experimental lifting-body planes were built and flown as gliders ~50 years ago for research purposes, and a search on lifting body will furnish you with more information on them.


Moment Coefficient Variation with Angle of Attack looking at the moment coefficient for certain NACA profiles, I noticed that their graph changes with AoA and is not a constant horizontal line as I would expect (pure moment independent of the AoA). This seems to imply that the moment and the associated moment coefficient is measured relative to a point $P$ (maybe the leading edge $LE$?) that is not the aerodynamic center $AC$ (otherwise the moment would be independent of Aoa) but I am not sure what that reference point may be. The figure below illustrates what I discussing...

Its most likely from the AC. When it is said the moment does not change with AoA in AC it does not imply a completely straight line, it can vary a bit but is somewhat straight as yours also is around 0.1. And that 'rule' only goes for low speeds btw. Once AoA is increased above a certain point when separations effects come into play, it will no longer be 'straight' as your graph also shows around 8 degs.

If you think the line is not straight enough, maybe your AC is not calculated exactly (maybe it just uses the rule of thumb of 1/4 chord).


What is this cutout in the Spitfire cockpit glass? This is a still from the film Dunkirk. I realise this is not a historical document, but I have also found a similar feature in photos of real Spitfires. What is the purpose of this?

According to flight manuals, this allows the pilot to maintain a view on the outside if the windscreen becomes obscured:

Source: Aircraft manual

This manual locates the panel on the right side. Online forums see this as a typographer mistake, but @TomMcW has found some aircraft had it indeed on the right side:

Source

On the reason for mist apparition:

  Note the punch-out panel on the canopy cover, an early solution to the
  new problem of canopy misting caused by the rapid altitude changes
  possible in the Spitfire.

Source: Flight Journal (pg 28)


Do ETOPS requirements vary between passenger, cargo, and non-revenue flights? Are there different ETOPS requirements for aircraft depending on usage?  For example, does a FedEx cargo flight need the same ETOPS ratings for over ocean flights as a passenger flight?  Also, how about ferry or repositioning flights which are not revenue flights?

The ETOPS requirement is pretty much the same for all aircraft irrespective of usage as long as its under parts 121 or 135, as noted in the FAA InFO 07004, New ETOPS Regulations:

  The new ETOPS rules are now applicable to:

  Part 121

  • All two-engine airplanes more than 60 minutes flying time from an adequate airport (at a one-engine-inoperative cruise speed under standard conditions in still air).

  • All passenger-carrying airplanes with more than two engines and more than
  180 minutes flying time from an adequate airport (at a one-engine-inoperative
  cruise speed under standard conditions in still air).

  Part 135

  • All multi-engine turbine-engine powered airplanes (other than all-cargo
  operations with airplanes having more than two engines) more than 180
  minutes flying time (limited to 240 minutes flying time) from an airport
  meeting the requirements of part 135, §§ 135.385 or 135.393 and 135.219 at
  an approved one-engine-inoperative cruise speed under standard conditions in
  still air.

As far as differences are concerned, ETOPS is waived only in one case:

  The FAA ... however agree that for airplanes with more than two engines, passenger carrying operations may be excluded from the ETOPS maintenance program requirements and that all-cargo operations may be excluded from all ETOPS requirements.

The definition of ETOPS in the same document covers all aircraft except four engined all-cargo aircraft:

  Extended Operations (ETOPS) means an airplane flight operation other than an all-cargo operation in an airplane with more than two engines during which a portion of the flight is conducted beyond a time threshold identified in part 121 or part 135 of this chapter that is determined using an approved one-engine-inoperative cruise speed under standard atmospheric conditions in still air.

As far as non-revenue flights are considered, they are usually operated under Part 91, so the ETOPS rules don't apply. However, it is better to plan an ETOPS route for safety considerations (and to keep insurers happy).


What effect would there be if the brakes were locked at touchdown? I'm imagining if you had a panicky passenger sitting in the right seat who had both feet firmly on the brakes while landing. Unless you had a crosswind and needed rudder as you touched down it's possible you wouldn't be aware of it. Or if there was a malfunction causing them to be locked. How likely is it that could cause you to have a bad day?

What if only one side was locked up (which seems worse to me)?

I'm mainly asking about small aircraft. Would it be any different for an airliner?

What if you were aware of it? What action would you take?

I've seen it happen many times (ask any rental place about this). You get a big bald spot cut into the tread. Sometimes it goes all the way through the tire.

If it happened on one side, you'd likely get a ground loop.


Why is a right pattern the standard for a hold? Why are right turns the standard hold turning direction?  Why not left?  Is there a reason or is it arbitrary?

This is a total shot in the dark. And, I have no citations for this. I always assumed that the a left-hand traffic pattern and a right-hand hold for a missed approach put the aircraft on the same side of the extended runway centerline. Presumably, this would be a more “protected” side of the airspace. Since standard traffic patterns for fixed wing aircraft are left, that would make the holds to the right.

Although, AOPA says the following...

  “Many holding patterns are executed in VFR conditions, which means that those in a holding pattern could encounter opposite direction VFR traffic that might be climbing or descending through the holding altitude. Veering to the right (as required by right-of-way regulations) to avoid opposite-direction traffic keeps the holding aircraft in its pattern. This would not be true when executing a left-hand hold, which is why left patterns are the exception, established only when necessary (because of terrain, for example).”
  https://www.aopa.org/news-and-media/all-news/2017/may/01/ifr-fix-what-were-they-thinking


How to calculate Night Flight time for a given flight? I am currently working on a project (web app) at university to be able to calculate the amount of time spent during night flying. Currently, I have,  Departure Lat and Long and Departure Time in UTC  Arrival Lat and Long and Arrival Time in UTC Sunset and  Sunrise Times (Based on dates) for both Arrival and Departure airfields in UTC
An example:  Depart UK Edingburgh airport on the 23 April 2019 at 11:10 UTC  Arrive Riyadh Airport at 18:10 UTC Total Time 7hr  day flight = ?  night flight = ?
I know many places online do this type of calculation for you, so I am wondering if there is a formula or method available that allows me to do this calculation (Which I can then convert to code)?
Thanks

This answer will address your question according to US FAA guidelines. Make sure to verify with your country’s aviation agency.
Civil Twlight
The time that you can log as “night” is based on the start or end of “civil twilight.” Civil twilight is defined as the time when the geometric center of the Sun’s disk is at most 6 degrees below the horizon. Civil twilight, as a general rule, is usually the 30 minutes before sunrise or after sunset. However, that can vary quite a bit with your location on the Earth’s surface.
Logged Time
Before (morning) or after (evening) civil twilight and between the two is when you can log night flight. You can take your total time (ie 2.3 Hobbs) and subtract any time that would not count as night and the result is what you are legally allowed to log as night time (at least here in the US).
Application for Development
I understand you're problem as a developer - you will have to use a website like timeanddate.com to grab an API that can find a local civil twlight using a city as an input. You will have to write a function that takes the departure time and determines whether it counts as night time, and then subtract any flight time that is ineligible.
I hope this addressed the mathematical request of your question and let me know if I can clarify at all.


What is the difference between a go-around and a missed approach? What is the difference between a go-around and a missed approach? What are the steps involved in each of the procedures?

Approach, missed approach, departure & holding
Approach, missed approach, departure and holding are published instrument procedures. They are characterised by waypoints, alitudes, headings, climb-, and descend profiles.
An approach procedure tells you how to get from cruise to short final, from a holding to short final, or from cruise into a holding.
A missed approach procedure tells you how to get from climb out into a holding or to another point from where you can commence a new approach.
A departure procedure tells you how to get from climb out to cruise flight.
Takeoff, landing, go around & touch and go
Landing is the process of getting an aircraft from short final to a full stop on the runway.
Takeoff is the process of getting an aircraft from a full stop to climb out.
A go around takes an aircraft from short final to climb out directly, not touching the runway.
A touch and go takes the aircraft from short final to climb out, touching the runway in the process.
Relationships
The procedures listed above can be combined arbitrarily. Even though a missed approach is often flown after a go around, they are not synonymous. Missed approaches can also be (and are) flown after a touch and go, or, for training purposes, after a takeoff. Also, a missed approach is not the only thing you can follow after a go around: Sometimes, you want to perform a departure and continue toward your alternate destination.


Are there countries where commercial flying can be conducted with a Mexican DGAC private pilot license? I have a Mexican DGAC licence. Can I work in other countries, or do I need to get another licence? (for example an FAA one if I want to work in the US)

No. If you want to make commercial activities, you need a commercial license.

I remind you the definition of commercial flight


Can a few random interaction with cockpit controls result in a crash? Lets say a monkey / snake interacts with 3 random controls inside the cockpit within less than 3 seconds until the PIC / SIC can take control of the aircraft again. Could such interactions result in a configuration leading to a crash that could not be reversed in time?

Assume the following:

small commercial aircraft (e.g. A319, CRJ900)
short distance flight (e.g. LEJ -> FRA)
appropriate cruising altitude for this distance

Edit: (for clarification)

It was mentioned I mixed the technical terms controls and instruments. I mean anything that does something when its pressed. So any buttons, switches, flight controls, etc.
This question is aiming at quick interactions with controls, no prolonged input.
Assume the pilots make no errors after the incident.

Background:
I was recently telling a post-9/11 flyer that I was generally allowed to visit the cockpit during the flight (as a child, pre-2000s). That person was surprised that this was allowed and asked what would've happened if a kid managed to interact with the cockpit.
Neglecting the fact that the pilots would probably intervene before any controls were touched it got me thinking if it would even be possible to doom a plane with a few quick interactions.

There's a real-life example that seems very similar: Aeroflot 593. The pilots let two children sit in the cockpit while the aircraft was on autopilot. One of the children pushed the control column for 30 seconds, which disengaged the autopilot and started a steep turn. The pilots tried to recover but the aircraft stalled and crashed, killing everyone on board.


What exactly is a "drone"? I was under the impression that things like this:

and soon this

and even this

Are drones.

When and how did the media and the general public get the idea that these:

Are also drones?

I'm not going to argue with the fact that the label has been given.  But remote controlled quad coppers are just another type of remote controlled aircraft, what makes them different from RC planes and RC helos?  (Nothing.)  So why are they being deliberately group with full sized military aircraft that are used for killing terrorist and patrolling dangerous regions?

So, while RC quad copters have been labeled by the public and the media as "drones" are they really?  What makes "a drone" really a drone?

General usage
According to Etymology Online The term drone, meaning "pilotless aircraft" dates from 1946.
It evidently encompasses all types of aircraft where no onboard human pilot is needed, either because the human pilot operates the aircraft remotely (still true for most types of military "drone" aircraft I believe) or because the aircraft systems are capable of full autonomy during some of all of a flight.
The earliest uses were probably "target drones". Which is what Wikipedia suggests.
The term does seem to have supplanted "RC aircraft" for modern small RC aircraft, especially those which carry a camera and/or from which their operators derive some value other than simply from mastering the skill of flying the vehicle.
English language is defined by usage, not by edict. So this isn't subject to rulings or appeal.
Lawmakers or other bodies might define the term more narrowly but this doesn't affect other uses of the same word.
FAA definition
The FAA talks mainly about "model aircraft" and "unmanned model aircraft" (ref.) and about Unmanned Aircraft(UA)  or Unmanned Aerial Systems (UAS). (ref.)
They usually don't use the term drone or define it, but from their FAQ it seems they consider the terms drone and UAS to be equivalent

Myth #7:The FAA is lagging behind other countries in approving commercial drones.
Fact– This comparison is flawed.  The United States has the busiest, most complex airspace in the world, including many general aviation aircraft that we must consider when planning UAS integration, because those same airplanes and small UAS may occupy the same airspace.


How to fly IFR to an airport without any instrument approaches? Would I just file an IFR flight plan to the airport in question, and expect to be cleared for the visual approach if there are no instrument approaches at the destination airport?

Yes.  If the airport in question has no operating control tower you need to cancel your ifr flight plan after landing if you choose to not do it in flight.  Once you land you can cancel with air traffic contol, if you are able to establish radio communication, or cancel with a flight service station.  It is usually going to be easiest to cancel with the local approach controller in flight, if there is no operating tower.  Remember all ifr traffic, landing and departing, will not be able to receive their approach clearance or ifr release until you cancel.


May airlines cancel unprofitable flights? If a given flight is unprofitable for an airline (occupancy ratio or – more precisely – revenue from ticket fares and cargo below the break even point) and if operating this flight incurred a bigger loss than cancelling it ...

May the airline cancel the flight ? (If no, why not?)
Will they ? (If they may but won't, why not?)
May/will they state the true reason or seize a pretext (e.g. technical defect) ?

Please distinguish between scheduled flights and charter flights.

Yes, airlines may cancel any flight. There is no obligation to execute a specific flight.

Their obligations towards the passengers depend on the local legislation. For instance:

International Flights: Airlines may cancel international flights, but passengers on flights between countries that honor the Montreal Convention are entitled to damage compensation if a cancellation cannot be justified.
European Union: According to Flight Compensation Regulation 261/2004,
 airlines are obliged to transport their passengers within a certain time frame. They will have to compensate passengers after a certain amount of delay is exceeded.
USA: There are no federal laws requiring airlines to provide passengers with money or other compensation when their flights are delayed. Airlines may book passengers on a flight of a later day. (Source)

Yes, airlines will cancel a flight if it is not profitable, but they will take into account all operational and commercial implications, and not just the profit on this particular flight. For instance the plane and/or the crew might be needed at the destination, or the plane has to park in a different place.

It depends on the airline if they will use a pretext. It is fraud if they use a pretext and avoid paying compensations to their customers.

I am convinced that most airlines are honest, but many
   are not.

In a charter flight all seats are booked through a travel company. The legal obligations of the airline should be the same.


Avoiding leaded gasoline in aviation I would like to get into aviation, but I have concern about the leaded gasoline used in most small engine planes.  How difficult will it be to avoid avgas while learning to fly?  And how should I go about doing this?  In particular, is it typical for flight schools to have diesel planes available for flight instruction, and is it reasonable for me to insist on this?

You could fly gliders. They don't use leaded fuel. In fact, they don't use fuel at all.


Is the low air pressure on top of the wing the major contributor to lift? I am kind of old time flyer. Started to fly with those primitive hang-glides with titanium frame and the yoke control, around 1966 and then after a few close calls and getting older I switched to small airplanes like Cessna 172 and Cherokee Warrior.

But from my decade of flying those hang-gliders I remember times when my wing fabric had collapsed because I must have been hit by a swift downdraft. I had to push it back up and hold it there a few seconds to stop stall. I needed to apply considerable upward force to push the fabric back up to airfoil shape. So I know how powerful the down-flow stream is.

If we consider the total pressure on top of the wing
 $ P_{wing} = P_{atm} - \frac{1}{2}\cdot\frac{dm}{dt}\cdot v_z^2$
and vertical speed $v_z = sin(\alpha)$, so by multiplying $v_z$ by the Wing surface we get the vertical down-flow and plugging it into the above equation we get a rough estimate of lift caused by low pressure on top.

I have checked many references on how lift is created and have not found any that refer to this major component of lift which I have personally experienced. Am I missing something?

I am adding a nice sketch of me rowing a boat. Using this setting as a poor man's wind-tunnel.
If you delay lifting your row at the end of its stroke it will glide back by the force of momentum of your boat. If you keep the row steady as shown on sketch and force it to drag behind you,what happens?
It creates a small swell, with water washing the outside face of the row a bit higher, shown on the sketch on red, and on the inside face of the row it creates a vortex at front and water washes the row a bit lower than lake level, shown in green.

My question is this: after reviewing many researches by labs and NASA and many other interested parties even prestigious universities, one finds less weight given to this significant part of the dynamics of lift: low pressure on top of the wing causing air to spill down to fill in by converting part of atmospheric pressure to kinetic energy, while relieving the wing top of full force of ambient atmospheric pressure?
I did a very rough estimate assuming the 176 square feet wing of Cessna  172 made of flat balsa and came up with approximately 850 lbs at 55 kn which is the rotation speed.

I am familiar with accepted theories like Newton's change of momentum of stream of air and NACA airfoils.

You must have read the wrong sources. Low pressure on the upper surface of the wing is really the major source of lift. The surrounding air sucks the wing up as much as it pushes it up from below.

On a flat plate, the contribution of suction and pressure is about equal. On a wing with a thick airfoil, some additional suction is added on both sides due to the displacement effect of the wing, so the resulting negative pressure change on the upper surface becomes bigger than the positive pressure change on the bottom. At low angles of attack, you even get suction on both sides.

Your pressure calculation is maybe helpful for the mean pressure difference between both sides of the wing, but it will not give a correct value for absolute pressure. It is better to calculate lift from the momentum change imparted on the air by the wing, as shown in this answer.

Your example with the row is well chosen: The local height difference of the water to the undisturbed sea level is equivalent to the local pressure difference to the static pressure (a higher water level signifies higher pressure) and shows the approximate conditions on a section of the wing. The row is like an inclined flat plate. You can even change the angle of the row and see the additional trailing vortex as it floats away from the row.

Now for the hang gliders: They are peculiar in that the airfoil shape depends on local pressure, and early models did not use lengthwise stiffeners so the pressure over the fabric could invert when the wing caught a negative angle of attack for a moment. You are lucky that you could press the fabric up again: Several early hang glider pilots could not recover and fell to their death. This happened when designers tried to increase the aspect ratio of the initial Rogallo shape of their gliders. I only know a German word for this phenomenon: Flattersturz.


Is this a famous aviator / airplane? This may be a little off topic but I could not find a better community or website.

I have two photo postcards with a man in front of a plane. Pretty sure it's Charles Lindbergh but an exhaustive Google search for anything related visually has only turned up another picture of CL with a similar jacket on. So is this who I think it is? Can anyone come up with a "verifiable" narrative to accompany these photos? Perhaps the type of plane in the background?

Thanks to the research of the other two answers, I finally found the context for these two photos. They are indeed of Clarence Chamberlin (a contemporary of Lindbergh) and were taken on June 15, 1927 at the Stuttgart-Boeblingen Airfield in Germany. The following page describes the events leading up to the photos, although the original is in German:

https://www.boeblingen.de/,Lde/start/WirtschaftEntwicklung/Chamberlin.html

Long story short, he was attempting to beat Charles Lindbergh on the transatlantic record, but Lindbergh won due to numerous delays. Chamberlin decided to go a little further, to Berlin, and beat the distance record instead. There were numerous technical problems with his plane, however (the Miss Columbia), and he ended up having to land in Eisleben, about 90 miles west of his goal on June 6, 1927. After a day spent repairing the plane, he then proceeded to Berlin. The event seen in the photos is a parade/celebration thrown in his honor as he leaves on the 15th.

By comparison, here's a photo from the same event showing Chamberlin in the same clothes:

I was unable to identify the specific plane behind him in the photos, but it was NOT the Miss Columbia. Due to the many technical problems experienced during the race, Chamberlin elected to return by sea. What we see in the photos is him about to board a passenger plane that will take him to the ship. As far as I can tell, the Miss Columbia was shipped back separately, although his co-pilot (and the plane's owner) Charles Levine wanted to fly it back despite the problems.

What About the Plane Type?

The plane that Chamberlin is boarding in the photos looks to be a Dornier Mercury, which was a common passenger plane in Germany at the time. The door size/shape and top of the plane (what we can see, at least) match up quite nicely. Here's a shot of one from a similar angle:

Thanks to @TomMcW for finding that.


Is a turboprop or a turbofan more eco-friendly? If we compare them, which one wins? Why? And, what about CO2 emissions?

To compare them we need to compare the same mission (we can't compare an A380 against a regional turboprop).
For 82-86 passengers on a 1,100 km (600 NM) trip, the turboprop comes out on top (for this mission).
2.79 L/100 km/seat (Bombardier Dash 8 Q400)
3.44 L/100 km/seat (Embraer E-Jet E2-175)

Note: a Boeing 787-9 flies 304 passengers over 9,208 km at 2.31 L/100 km/seat.

From slowest to fastest, the economical choice would be turboprop, turbofan, and turbojet. Above ~700 km/h, the turboprop starts to lose.
The why:

Turboprop: The core runs at near full power, and with a reduction gear, the propeller runs at a slow speed suited for slow flight. If the blade tips reach Mach 1, efficiency starts to go down (at a fixed RPM, blades fly faster the faster the plane).
Turbofan: Same principle, but instead of a reduction gear, a low-pressure spool is used. And with the nacelle/shroud, the fan can run faster and move more air.
Turbojet: The core provides the propulsive power directly, this solves the slow exhaust of the turbofan in supersonic flight.

The common theme: gas turbine cores run best near their full power. That makes a turbojet bad at slow speed / low power.

Fuel mileage and image source: Wikipedia article 'Fuel economy in aircraft' (well sourced).
Also see: Why are propeller engines uncommon on airliners?


Difference between Mach buffet and shock stall What is the difference between Mach buffet and shock stall?

Transonic buffet is caused by the separated turbulent boundary layer striking the airframe (horizontal stabilizer, wings, fuselage) with considerable force causing a high amplitude vibration, which physically shakes the whole aircraft. It's highly destructive and all commercial aircrafts should avoid entering a buffet boundary zone. That's why commercial transonic aircrafts are limited, not only by IAS, but also with Mach number as well. The reason for separated boundary layer is a shockwave formation on the airfoil which causes a great adverse pressure gradient and separates the airflow from the wing. The transonic aerodynamic buffet is an imminent warning to the shock stall. As the shockwave strengthens and separation becomes even more severe there will be a great change in coefficients of lift, drag and pressure. These changes will induce more drag, and due to the Cp changes on the airfoil it will cause mach tuck to occur. Mach tuck is a phenomenon which causes a nose down tendency of an aircraft and it is very difficult to compensate it only with the elevators. When all that occurs then we are talking about a shock stall. Shock stall is associated with an aircraft dive while transonic buffet is a warning sign to the shock stall and physically shakes the whole aircraft with a quite destructive force.


What privileges do off-duty pilots have in their own airline? I was recently in a Delta flight where there were two off-duty, but in-uniform pilots flying along with the passengers. One of the pilots sat in the First Class section of the airplane and the other sat in the Economy section. After the seatbelt sign came off, the pilot in the Economy section moved up to the First Class where there was apparently an empty seat.

This led me to wonder: what privileges do off-duty pilots have in-flight?

I am limiting this to only US to keep it from being "Too Broad".

This is airline specific, so there's no single true answer: but I'll give an overview of what's "normal practice" for many airlines:

Airline staff will typically be bumped to First/Business class when there are available seats, although they're not usually top of the list.

In a typical airline, frequent flyers will be bumped first (particularly those with a lot of business class miles but who happen to be travelling economy right now): it's a way of rewarding loyal/frequent customers.

Once the frequent flyers are all moved up, though, the seats will often be filled with staff or contractors. Typically deadheading/on duty staff first (ie those who are flying home from a previous flight that they were working on), followed by off duty staff and their families.

This is airline specific, however - some airlines will bump everyone on the frequent flyer program  until Business is full, leaving no space for staff. Others will not move any passengers up (to discourage business class flyers deliberately trying to "game" the system by booking economy on quiet flights knowing that they'll likely be moved up), leaving more space for staff. Some airlines will not bump staff at all, or will only do so for deadheading staff (those who are flying because of work, not for their own holiday etc).

There's a lot of variation on things like whether your family will be bumped with you, or whether only higher-level contractors will be moved up. I used to work for a company which worked with airlines, and typically our directors would be moved up to Business while the lackeys were left in Economy


How should a flight review be logged? 14 CFR 61.56 (c) requires pilots to perform a Flight Review every 24 calendar months unless another applicable action has been taken in order to be eligible to act as pilot in command of an airplane.

The requirements of a flight review state that a minimum of 1 hour of flight instruction and 1 hour of ground instruction are required to complete that review.

My question concerns the logging of that activity. In the past my instructors have given me an signed logbook entry for the flight time, a description of the training received and materials reviewed a logbook endorsement stating that the flight review was performed. Most logbooks have a section for ground instruction, but I've never logged specific ground time there during a flight review. For a flight review to be valid does the ground instruction actually need to be logged separately from the flight instruction? Or is the ground instruction implied by the endorsement?

Short answer: log it however you like as long as you log it.

According to the FAA:

  When the applicant has successfully  completed the review, the CFI
  should endorse the pilot’s logbook to certify that the pilot has
  satisfactorily accomplished the flight review.  The CFI should make
  the endorsement for a  satisfactory review in accordance with AC 61-
  65. The flight and ground time must also be  logged in the pilot’s logbook in  accordance with § 61.51(a)(1)

61.51(a)(1) simply says that "Training and aeronautical experience used to meet the requirements for a certificate, rating, or flight review of this part" must be logged.

So you do have to log both ground and flight time, but exactly how you do that is really up to you. The FAA doesn't require any specific logging format as long as the information is correct and CFIs, DPEs and others can see what they need to see.

Personally, I would note the ground time beside the CFI's endorsement and then log the flight time as I would for any other training flight. I've never met anyone who logged their 'ground instruction' time precisely (simulator time is a different story), but if you want to then you can do it any way that works for you. The FAA just wants you to log something that shows you did receive the necessary ground training.


Why do some helicopters have wheels instead of skids? I have noticed that Black Hawk helicopters have tires, but I have not seen one take off like a plane.

When would a helicopter need to use a running take off or landing?
When is it determined whether a helicopter gets skids or wheels?

AOPA has a nice little blog post on the matter

  Skid landing gear is simple and lighter weight, so it is the best
  choice for small helicopters as weight is always a consideration.
  Also, skid landing gear needs very little maintenance, but the
  drawback is that ground handling is more difficult.

And for wheels

  On larger more powerful twin-engine helicopters weight is not as big
  of a concern and retractable wheels make sense. Wheels are nice
  because a helicopter can ground taxi (as opposed to hover taxi) around
  other aircraft and people without worrying about producing a high
  downwash. Retracting the gear also reduces drag, allowing for a higher
  cruise speed.

So skids are light and simple and wheels are convenient when you have the useful load and space.

This article also notes thats skids are preferred when parking on an non-level surface
to prevent accidental rolling around and or sliding off the deck of a carrier.

This article offers more info from the pilots perspective but comes to basically the same conclusions.

The answer seems to be that they are chosen based on the mission profile of the helicopter as well as the size to some extent.


What are some of the largest propellers post-WWII? (Source)

The propeller on the Linke-Hofmann R.II (1919) holds the record at 6.9 m (22 ft 6 in).

What are some of the largest propellers post-WWII? Top 5 or so.

From Google, here are some of the largest post WWII propeller diameters:

Antonov AN-22: 20'4" (6.2 m)
Convair B-36: 19' (5.8 m)
Douglas C-133: 18' (5.5 m)
Hughes H-4 "Spruce Goose": 17'2" (5.2 m)
Boeing B-29 and B-50: 16'7" (5.1 m)
Martin Mars: 15'2" (4.6 m)
Vought Corsair: 13'4" (4.1 m)


Can the pitch be very different from the angle of attack? How much the pitch (horizontal orientation) can differ from the angle of attack? I am trying to understand the claim that "angle of attack indicator was unfortunately not available", contributing to problems during Air France Flight 447. Attitude indicator most likely was available?

The angle of attack is the angle between the wing (wing chord to be precise) and the direction of travel (undisturbed airflow). The angle of pitch is the angle between the main body axis and the horizon. The difference can theoretically be any angle, but during normal flight it will be limited to about 15 degrees.

The reason that the angle of attack sensor was inoperative was due to low airspeed. Below 60 knot IAS the indication is unreliable and therefore the indicator is inhibited. This also inhibits the stall warning. This lead to the confusing situation that lowering the nose to correct the stall increased the airspeed beyond 60 knots, thereby reactivating the stall warning.


What kind of ADS-B identification code is FFxxxx, where xxxx are numbers i.e. FF0024? I live near an airbase and use an ADS-B receiver that picks up aircraft using regular ICAO assignments. They do not include flight path details or position info, but can be identified by the ICAO number which is a civilian aircraft identifier. Sometimes, it captures aircraft SSR returns with what appear to be invalid numbers, beginning with FF followed by 4 digits, such as FF0024 FF7777.

Are these drones? cruise missiles? Aurora? Or some other military aircraft identity?

I am going to assume you use Flightaware's variety of dump1090 as a decoder.
When that receives a Mode A code, it publishes it as if it were a 24 bit address. The first two hexadecimal digits are filled with 'FF'. I have no idea why this may be a good plan.

In mode_ac.c, lines 368-370:

// Fudge an ICAO address based on Mode A (remove the Ident bit)
// Use an upper address byte of FF, since this is ICAO unallocated
mm->addr = 0x00FF0000 | (ModeA & 0x0000FF7F);

These may be drones but most likely they are just simple aircraft replying to Mode A/C interrogations.

If you are in the USA, FF7777 is a field test transponder (Range & Azimuth Beacon Monitor, RABM) , usually located not far from a radar to verify the correct working of the radar.


Is the time pilots are commuting considered rest time? Pilots operating under FAR Part 121 assigned to domestic routes are required to have a certain amount of "rest" time before beginning a flight.  Further, the maximum  "flight time," (where the pilot is not resting or on duty) is constrained within specific periods such as monthly, yearly, etc.

If a pilot lives in Florida, but is based in and originates flights from California, is the time spent commuting (from Florida to California) to begin a flight considered part of the FAR required "rest" time?

Within the new fatigue regulations in Part 117 and the older Part 121.471, the word commuting is not defined. Deadheading is defined as follows (Part 117):

  Deadhead transportation means transportation of a flightcrew member as a passenger or non-operating flightcrew member, by any mode of transportation, as required by a certificate holder, excluding transportation to or from a suitable accommodation. All time spent in deadhead transportation is duty and is not rest. For purposes of determining the maximum flight duty period in Table B of this part, deadhead transportation is not considered a flight

Time spent deadheading must be included in the flight duty period calculation (Part 117.25):

  (g) If a flightcrew member engaged in deadhead transportation exceeds the applicable flight duty period in Table B of this part, the flightcrew member must be given a rest period equal to the length of the deadhead transportation but not less than the required rest in paragraph (e) of this section before beginning a flight duty period.

Deadheading and commuting are not the same. In section 11 of Advisory Circular 117-3, the FAA provides clarification. It defines deadheading as used to reposition flight crewmembers while commuting is considered an "individual initiated function".

To address the scenario, it would depend on if the time traveling from Florida to California was scheduled deadhead transportation. If so then the flight time is considered part of the duty period. If such a flight was individually initiated, then the time is commuting and is not part of the duty period.

Despite the potential legality of the situation, the FAA considers fatigue a joint responsibility between the flight crewmember and the certificate holder. This situation would put the flight crewmember at risk for fatigue. Individual airlines may place additional policy restrictions on commuting since Part 117 does not.


What is Class F airspace, and why is it not used in the US? I've read that ICAO defines Class F airspace but the FAA has chosen not to use the airspace class in the US. What is the ICAO definition of Class F airspace and how does it differ from other airspace classes? What countries use Class F airspace? Why does the FAA only use A-E and G?

ICAO Class F airspace is a bit of an odd duck (and the US FAA is apparently not the only agency that thinks so - from a quick check on Wikipedia it seems more jurisdictions ignore class F than implement it. They only mention Class F as being in use in Germany and the UK).

From a functional/regulatory standpoint Class F is a sort of hybrid between "Class E" controlled airspace and "Class G" (fully) uncontrolled airspace:
Class F airspace is designated as "uncontrolled", but you can get ATC clearances in Class F airspace just like in controlled airspace. The catch is they're "advisory only" (so you don't have to comply with them, and all the weight is on the pilot's shoulders ). Similarly ATC will provide separation services to IFR flights in Class F airspace, but they do so "where possible", which means they might tell you they can't provide that service and you're on your own with see-and-avoid.

The general use case for Class F airspace seems to be allowing IFR flights to operate in "uncontrolled airspace".

As a US pilot (and thus having no experience with Class F Airspace), it sounds like the services provided in Class F airspace are effectively the equivalent of VFR Traffic Advisories ("Flight Following"): Controllers can give you advisories and make suggestions, but all responsibility is ultimately still on the pilot's shoulders, and you can politely tell the controller to get stuffed if you don't like their suggestions (without needing to declare an emergency to vest yourself with that authority).

In the US we already have the Flight Following system and culture set up for VFR folks (and generally speaking it's available nationwide, irrespective of airspace class, as long as the controller can get you on radar and isn't overworked). We also have a pretty robust Class E airspace nationwide.
Because of this the FAA probably sees no need to designate specific "Class F" regions where IFR flights can get the equivalent of "Flight Following": If you're VFR you can usually get flight following if you want it, and if you're IFR you should have no trouble staying in controlled airspace (Class A, B, C, D, or E) for your entire route of flight.