What can cause my radio to transmit nothing but a terrible noise?

Being able to talk inside the airplane is not related to the radios function, the intercom (generally part of the audio panel these days) is what allows cross talk between headsets.
It sounds like you have checked all your connections which is always a good first step but after that:

Check your ammeter when the radio is in operation and make sure you have sufficient current to run the radio, if you are showing a heavy discharge on the system you may not have sufficient power to run the radio (the presence of 12V or 24V does not indicate you have enough power to run the radio)
Check your radio grounds (also lots of good info here) as they can be the source of a lot of static.
If both talk switches cause the issue (and they are wired properly) I would take a look at the radio unit its self. Perhaps have it pulled and bench tested with known good components to isolate any other factors from the aircraft. This may also assure you the radio was serviced properly when it was serviced.


Is there a relationship between turbojet engine rpm (N1 & N2) and fuel consumption rate?

Yes, these need to be roughly proportional for the engine to work, and will move towards an equilibrium if they are not.

The compressor provides the air for the combustion, and injecting more fuel will only generate a little extra power, which however increases the turbine speed, increasing air intake, which will allow more fuel to be burned, again increasing available power and so on.

In practice, if the air/fuel mixture is way off, compressor surges can happen, so in modern systems the engine computer will limit fuel flow.


Can you feel passing through the sound barrier in an F-16?

In an aircraft designed to go supersonic, it's an absolute non-event, and one is only aware of it by observing the instruments, and noting diminished control authority-- slower roll rate, etc. At least, that was my experience in the T-38, and according to every account I've read.

If the aircraft is NOT designed to go supersonic, then the experience can be quite different, although that mostly comes from loss of control at high Mach numbers (starting in the 0.9X range, as best I recall), rather than anything that occurs right at Mach 1.00.


How can I take off in a straight line if the runway isn't visible ahead?

Thats what the compass is for.   Continue to fly runway heading according to the compass & heading indicator.

While you may not be able to see the runway, you may have other markers.   Even a good cloud in front of the airplane can serve as a VFR reference point.

Or look out the side to the left-and-right of the plane.  You should be able to tell if you're going straight or turning by what you see going past the sides of your plane.


Is this paragraph about the dihedral effect in the FAA's Glider Flying Handbook correct?

No, the explanation is not correct.

Tanner, you are right when you say that lift does not depend on bank angle. Lift is caused by a pressure difference, and pressure can only act perpendicularly to a surface. Therefore, the lift on each wing and its lever arm to the center of gravity won't change with bank and no "correcting" rolling moment is created.

Instead, what does happen is a side force from the wing's bank angle which will accelerate the airplane sideways. This in turn will result in a sideslip condition, and only now will a dihedral effect show up: By changing the angle of attack on each side differently, the sideslip in combination with dihedral will create a correcting rolling moment.

As you correctly observe, a stabilising effect can only come from a difference in angle of attack between both wings, and that only occurs in a sideslip.


Pros and cons of a pull-push propeller configuration

Pusher-puller multi engine vs single or multi engine contra rotating propellers:

Pros:

Ideal configuration for a multi engine aircraft as it eliminates thrust asymmetry in the event of an engine failure.
As a consequence, improves safety during takeoff, landing and low speed, low altitude flight.
Can be a useful arrangement for multi engine flying boats.
Does not require oppositely geared engines nor heavy gearboxes.

Cons:

Engine crankshaft on the A/C centerline requires a more unorthodox airframe to accommodate which can present additional design challenges.
Does not fully eliminate propeller slipstream yaw depending on the aircraft layout.
Does not eliminate or reduce yaw from P-Factor.
Can be noisier inside the cabin than a twin with wing mounted engines.
Aft mounted Engine can be more difficult to cool due to indirect ram airflow.
Disrupted airflow from fwd propeller reduces the efficiency of the aft propeller.


What is the necessity of Obstacle Departure Procedure(ODP)?

Departure procedures are way to get IFR traffic from the airport to the en route system. There are four different procedures.

If an aircraft may turn in any direction from a runway within the limits of the assessment area and remain clear of obstacles that runway passes what is called a diverse departure assessment and no ODP is published.
There are a few in Kansas and Nebraska but  Florida, which is also pretty flat, only has a couple at military bases.

Obstacle Departure Procedures (ODP) are only used for obstruction clearance and do not include ATC related climb requirements. They often have higher visibility minimums and climb rates greater than 200 fpnm. Most are given as text, though occasionally there are graphical representations of them. They frequently have other restrictions, e.g. the tower must be open and monitoring a VOR, not available if local altimeter setting is not available. All but a few airports have an obstacle departure procedure.

A Standard Instrument Departure (SID) is an ATC-requested and developed departure route. Pilots must have at least the textual description of the procedure. SIDs always have a graphical depiction. Unlike Obstacle Departure Procedures, SIDs usually have portions where the altitude is restricted—either minimum or maximum. Most SIDs have multiple transitions to get you into the en route system. Small airports generally do not have SIDs and most airports that have scheduled air carrier service have at least one SID. While the primary purpose of a SID is to ease pilot and controller workload while getting the aircraft into the system, they also provide obstacle clearance.

A visual climb over airport (VCOA) is a departure option for an IFR aircraft, operating in VMC equal to or greater than the specified visibility and ceiling.

A radar departure is another option. They are established when ATC has a need to vector aircraft on departure to a particular ATS Route, NAVAID, or fix.

All departures (except VCOA) assume that the aircraft will cross the departure end of the runway at 35' or more, continue on the runway heading until reaching 400', and climb at a rate of 200 feet per nautical mile. Standard minimum visibility applies, 1 mile for 1 and 2 engines and ½ mile for 3+ engines.

You can read more about departure procedures in FAA-H-8083-16 Instrument Procedures Handbook, Chapter 1 Departures


Could future airplanes use rockets to recover plane and/or prevent crash landings?

They could but there really is no reason to do so. Most aircraft glide just fine if they lose all engine thrust and are perfectly controllable in such situations (provided they can actuate the control surfaces). As for the situation you propose there are a few issues with it,

First off, rocket fuel is not jet fuel and can't just be burned in the same way.

The JATO engines are a bit different than the rocket assist that Space-X is using (although the principal is similar). For takeoff the Jato engines help add to the totally available thrust and allow the plane to get off the ground in a shorter distance. The rockets are (I believe) single use and provide a very quick burst of thrust.

As for the loss of control this depends on what causes the loss of control and how the rockets are affixed to the airframe. In the case of the Alaska airlines flight you reference the jack screw forced the tail into a position and prevented it from moving, this put the plane in an unrecoverable dive that would only be exacerbated by rocket engines unless you could control the angle at which they were pointed. Again in the outlined case you would need to be able to counteract the full surface deflection of a control surface. In essence you would need the kind of thrust control that space ships have used over the years.

Now to answer the broad question of "could rocket thrusters be used to bring a disabled aircraft down softly" the short answer is yes. They could be added for such a task but the toll they take on the plane would make it a hard sell to the airlines. In short the use case is small and the added weight cuts into the profitability of the flight (you need a lot of jet fuel and heavy thrusters to pull this off). On top of all that the system would have to be built and certified for use, a task that should not be taken lightly. In the end you get a safety system that has a small use case and a big impact on the aircraft. Perhaps the best thing airplanes can learn from space craft landings is the use of parachutes.

The last and somewhat debatable point (common to all safety systems) is when do you actually turn it on? What is your definition of unrecoverable (yes this varies)? Cirrus teaches people to basically always pull the chute in an emergency. Are you going to teach pilots to to always trigger this rocket decent system even if the plane may be recoverable? What if you run out of fuel before getting to the ground and now you are to low to recover from the rocket assisted decent?


Why do wall-to-wall airfoils in wind tunnels produce no (or infinitesimal) downwash?

Who says that the flows only interact at the trailing edge?

The flow on each side of a wing creates (and is the creation of) a pressure field which influences what goes on on the opposite side in subsonic flow. Only in supersonic flow is that kind of interaction impossible because small pressure changes move only at the speed of sound.

First to the topic of flow turning. Half of that has already happened at the quarter point of the wing chord, so it is spread out over the whole wing. At the trailing edge the local flow direction is parallel to the trailing edge inclination if flow is not separated already. Past the trailing edge the flow readjusts to the downwash angle which is normally largest behind the center wing. In the case of an elliptic lift distribution, the downwash angle is constant over span, but it is almost never strongest near the wingtips. The experts at NASA certainly know that, too, but I wonder how often they are consulted by the marketing people who write those web pages.

Next to the tip vortex: It does not cause induced drag and is only a side effect of downwash. Please read this answer and try to follow all the links. There is not a single vortex but a vortex sheet leaving the wing, and to better understand what is happening it is best to forget all that.

Now to the conditions in a wind tunnel. The flow there is practically like one in ground effect, so no full downwash like in free flow is produced. In order to arrive at realistic results, wind tunnels use correction factors in order to make the results of their measurements close to those in free flow. If there is a gap between the trailing edge and the wind tunnel wall (and there certainly is), there is also some downwash, but less than in free flow. As explained in this answer, the part of the wake which flows down past the wing is smaller than the wingspan, so a crippled version of the wake behind a wing will also form in a wind tunnel, with air near the side walls moving up and air in the center moving down. Normally, this is all equalled out when the air flows through the next grating which is installed to remove turbulence or help the tunnel flow around the next corner.

  the explanations above describe downwash as the main (almost only) reason for induced drag and tip vortices as just a result of downwash.

Yes, tip vortices are indeed a result of downwash. You link already to two good explanations for that, so I need to go beyond those answers. The two vortex cores resulting from the rollup of the vortex sheet trailing behind the wing are not really the tip vortices you might see in humid air, like in the picture of an A340 below (picture source).

The condensation at the wingtip is from the high suction caused by flow locally negotiating the small radius of the winglet tip. This is the tip vortex. The much stronger vortex pair forming behind the wing is what the NASA page refers to, but that only happens when the air is already long past the wing. That is the wake vortex. In the cores of the wake vortex pair the pressure is lowest because the radius of the helical motion is smallest - vortex strength is the same for every point in a plane perpendicular to the direction of motion of the wing. Therefore, the NASA page is at least misleading, if not outright wrong.

In the wind tunnel the same happens (minus the tip vortex), but boxed in by the wind tunnel walls. They slow the wake vortex by wall friction and stop the wake from continuing downwards, just like the ground does in ground effect. But there is still a pair of vortices close to the bottom wind tunnel wall (or the top, if the wing section is mounted upside down).


How is the crew rest area on the A350 accessed?

It looks like your image came from this article, since they have the exact same one.

According to Boeing, this is the most practical place, and Airbus has finally decided they agree.

  For the first time in Airbus aircraft –and after benchmarked[sic] Boeing´s configuration-, the A350 XWB’s crew rest compartments are in the aircraft crown.--All images and quotes from article linked above unless otherwise noted.

This image shows that the cabin crew's rest area is at the rear of the aircraft, while the flight crew's is up front. It also shows how they've shifted out of the basement and into the attic:

Image courteously, but unknowingly supplied by core77.com

Further down in that article they state why the crew rest areas are where they are:

  The A350 XWB crew rests, located overhead in the crown area, have no impact on revenues space – whether cargo or passenger – and contribute to the efficiency of the A350 XWB cabin.

It also explains how you get there:

  Entrances to these rest areas are located outside the passenger cabin, so they do not use up seat space. “This is the first time a crew rest area on an aircraft will have no revenue-generating impact,” A350 XWB Marketing Director Bausor said.

Unfortunately, I'm guessing that the crew rest areas do not actually have a skylight one might infer from this image:

I'm sure the day-shift crew would enjoy sleeping under the stars at night, though the night-shift crew probably wouldn't enjoy the bright sunlight while trying to sleep.


What is the origin of the term "military power"?

The etiology of military power is from War Emergency Power (WEP) which in the WWII era was a higher than normal rating power (i.e. >100% rated power) setting on an aircraft engine.  Such power settings were approved for short durations (typically 5 minutes or less) such as takeoff and battle maneuvers.

The term was quickly shortened to military power.

Sometimes military power is assumed to be simply full throttle, but that may not be accurate, particularly in blown engines, where turbochargers or superchargers may be set to permit higher than normal air delivery to the combustion chamber.

Finally, military power was used for more extended periods of times, when conditions dictated, but at a reduction in reliability and service life.  Sometimes in war, service life is not a pilot's greatest concern.


Is there a way to avoid fuel loss caused by vaporization from engine heat?

According to this image of the locations of the Concorde's fuel tanks:
Borrowed from: ConcordeSST.com
and this image of the location of the Concorde's engines:
Also from ConcordeSST.com
It doesn't appear that there is a lot of room for direct transfer of heat from the engines to the fuel tanks.
Also of note, the Concorde's designers intentionally used the fuel for other cooling purposes:

The fuel is also used as a heat sink for cooling purposes. Surplus heat from the air conditioning and hydraulic systems from the constant speed drive and generator and also from the engine lubricating oil is rejected through heat exchangers to the fuel.
--ConcordeSST.com

Based on this, I would say that the amount of fuel vaporized by engine heat was minimal at best, and, therefore, of no concern.


Does uncoordinated control affect stall speed?

First question, yes.  For two principle reasons: instrument error and a change in relative wind across the wing. The increase in indicated AS would be small.

Second question, not a factor.  During the flare, you are close to the ground, and the AOA is mostly controlled by feel, sink rate and all the other things that factor into that complex maneuver.  So if the speed were slightly higher, it probably wouldn't make a difference.

But let's talk practicality.  When landing a C172 in a direct crosswind of 20k or so, I would add 5k to my speeds, and if the winds were gusty I would add accordingly (like 1/2 the gust factor approximately).

It is better to focus on having a stable approach with good AS and pitch control, than it is to fret over a potential 2k indicated stall speed differential.  Besides, in ground effect the numbers change as well.


Can a passenger jet be towed to safety if it breaks down in midair?

Towing is quite feasible, and even landing while in tow is possible - I've done it myself in gliders. The hard part is catching up with the stricken plane.

To stay with Keegan's Boeing 777: It most likely will travel at Mach 0.8 and somewhere between 30.000 and 39.000 ft when disaster strikes. Let's further assume that power fails instantly, so the aircraft, traveling at 240 m/s, will develop a sink rate of 15 m/s just to continue flying. When it sinks, the increasing density allows it to slow down, so at sea level it will fly at 130 m/s, sinking with 8.125 m/s. For simplicity, assume a linearly decreasing sink rate, and the remaining time aloft will be less than 1000 sec or around a quarter of an hour.

Now the towplane has 15 min to scramble the crew, run up the engines, get take-off clearance and to actually fly an intercept to the stricken airliner. How realistic is that? How many airports are needed to have 777-sized towplanes ready, and how many otherwise unproductive 777s would this scheme need?

A car can stop and wait a couple of hours for the tow to reach it. An aircraft can not.


How is the 737 main landing gear protected from weather?

Aircraft icing is not caused by ice in clouds- it is formed by supercooled water droplets (Source). They freeze on impact with a surface that has some location with zero flow velocity, most often on the leading edge of the wing.

  Ice accumulates on every exposed frontal surface of the aeroplane – not just on the wings, propeller, and windshield, but also on the antennas, vents, intakes, and cowlings. It builds in flight where no heat or boots can reach it. It can cause antennas to vibrate so severely that they break. In moderate to severe conditions, a light aircraft can become so iced up that continued flight is impossible. The aeroplane may stall at much higher speeds and lower angles of attack than normal. It can roll or pitch uncontrollably, and recovery may be impossible. Source

The gear as such as is not worse off than normal landing gear. The B737 has wheel caps visible in your first photo to cover towards the outside, and is not allowed to fly without them. If icing had been a problem, the same concern would extend onto landing gear doors being frozen shut. Landing gears bays are unpressurised and very cold normally anyways.


How does a long inlet affect a jet engine's performance?

Long, winding intake ducts can increase the drag on the airflow moving through them, reducing the amount of air which the engine can ingest as opposed to a traditional diffuser design on a nacelle.  Aircraft like the Harrier as well as the F-22, F-35 and F-117 have solved this problem with the use of large, suck in doors along the length of the intake duct in order to provide additional air mass flow during low speed or ground operations, where ram pressure cannot provide the additional airflow through the fan or engine core.


What is this USAF transport aircraft from possibly the 50-60s?

It is indeed a C-130A. The large tail numbers indicate it's from the late 50's or early 60's. In the late 60's, the USAF went with smaller numbers forward of the passenger door. Here's a similar a/c image from C-130.net

Further searching of the C-130 Aircraft Database shows the only "014" to be be s/n 55-0014. The history shows it was assigned to the 40th TAS which was part of the 322nd AD.

In 1968 it was converted to an AC-130A gunship. It is currently on display at the Museum of Aviation at Robins AFB.


Where can I find flight plan records for a private flight in the 1970s?

Depends on the type of aircraft, but if any records have managed to not be destroyed after 48 years, I would suggest you start by talking to the owner/operator of the departure and arrival airfields. US Customs might have a record of a customs inspection if there was one, but you'd have to file a FOIA request and be prepared to wait for an answer which may not be the one you want to hear.


How hot would pressurized air get if the air conditioning failed?

The air conditioning is in a so called "air cycle machine" (ACM). If it fails, the air will not be compressed (done in the same machine).

Temperature goes up and down as the air passes through the machine's heat exchangers, compressors and turbines, reaching 250$^\circ$C at peak.

Wikipedia article

Image from ECS


It seem your graph of induced lift is not decreasing because you assume that the lift increases with velocity. This is generally not the case.

Typically, a drag vs velocity graph is made for unaccelerated level flight. Under these conditions the lift is equal to the weight of the aircraft.

$L = W =  \frac{1}{2}\rho V^2 c_L S$

From this we can obtain the lift coefficient as a function of velocity:

$c_L =  \frac{W }{\frac{1}{2} \rho V^2 S}$

The drag of the  aircraft is the sum of the parasite drag and the induced drag:

$D = D_p + D_i$

With the parasite drag:

$D_p = c_{D,0}\frac{1}{2} \rho V^2 S $

And the induced drag:

$D_i = \frac{1}{2}\rho V^2 S \frac{c_L^2}{\pi  AR \epsilon} =
\frac{W^2}{\frac{1}{2}\rho V^2 S \pi AR \epsilon}  = \frac{W^2}{\frac{1}{2}\rho V^2   \pi b^2 \epsilon}$

It is important to understand that this only holds when the lift is equal to the weight of the aircraft (e.g. straight & level flight)

Nomenclature:
    $L\:\:\:\:\:$ lift
    $W\:\:\:$ aircraft's weight
    $\rho\:\:\:\:\:$ air density
    $V\:\:\:\:$ velocity
    $S\:\:\:\:$ wing surface area
    $c_L \:\:\:$ lift coefficient
    $c_{D0} \:$  zero-lift drag coefficient
    $\pi \:\:\:\:\:$  3.14159$\dots$
    $AR \:\:$  aspect ratio of the wing
    $\epsilon \:\:\:\:\:\:$  the wing's Oswald factor
    $b \:\:\:\:\:\:$  wing span


Why does a sport certificate have no distance restriction while recreational does?

Because a sport pilot certificate requires the applicant to undergo at least three hours of cross country flight training whereas a recreational pilot certificate does not have that requirement.

I always got the impression that a recreational pilot certificate was essentially for people who had soloed and did not want to accomplish any other aviation goals save flying around their local airport.  Instruction is restricted to pre-solo aeronautical knowledge and skills.  It’s pretty limited in capability compared with a private pilot certificate, which explains why there are less than 600 recreational pilots registered by the FAA.

And one can expand a recreational pilot certificate to permit PIC on cross country flights over 50 nm, but this will require additional training and logbook endorsements by an instructor


Most likely it’s a compressed air line which connects into the jet’s bleed air system.  This can be used to crank the engines as opposed to using bleed APU air to do it.

Another use (if you’re talking about the line under the jetway) is to provide cool air for cabin air conditioning without needing to run the APU to do so.


How to interpret BECMG and TEMPO in TAF?

The BECMG group in a TAF describes a gradual change which will take place over a prolonged period of time, but will be the prevailing weather once that change is complete. The time period described in the TAF is the beginning and ending hour during which the gradual change is forecast to be in progress. At the end of the described time the change is expected to be complete and the forecast weather should be the prevailing weather thereafter.

See the description of BECMG from the US Aviation Weather site's TAF decoder page:

  The BECMG group is used when a gradual change in conditions is expected over a longer time period, usually two hours. The time period when the change is expected is a four-digit group with the beginning hour and ending hour of the change period which follows the BECMG indicator. The gradual change will occur at an unspecified time within this time period. Only the conditions are carried over from the previous time group.

Conversely, with the TEMPO group, the described time period is a beginning and ending period after which the weather is forecast revert to the previously prevailing weather.

See the description of TEMPO from the US Aviation Weather site's TAF decoder page:

  The TEMPO group is used for any conditions in wind, visibility, weather, or sky condition which are expected to last for generally less than an hour at a time (occasional), and are expected to occur during less than half the time period. The TEMPO indicator is followed by a four-digit group giving the beginning hour and ending hour of the time period during which the temporary conditions are expected. Only the changing forecast meteorological conditions are included in TEMPO groups. The omitted conditions are carried over from the previous time group.


How can I calculate which runway to use for landing, based on the wind?

The name of a runway is a number indicating its direction in tens of degrees.1 For example, to land west-to-east, use runway 09.

Generally, each runway paving may be used in either direction, and the physical paving actually contains two logical runways, running in opposite directions. Only one of these logical runways is allowed to be in use an any time.2

The two logical runways on a paving have names that differ by 18. Thus a paving aligned due east-west will contain logical runway 09 and logical runway 27.

The information you will need about each airport is simply a list of the available runways and their lengths. You will also need the minimum runway length required for your aircraft to land.

To determine the best runway to land on, divide by the wind direction by ten and use the runway that is long enough whose name is closest to the result.

Example: An airport has runways 04 (1200'), 09 (5000'), 15 (5000'), 22 (1200'), 27 (5000'), and 33 (5000').3 Your airplane needs 3500' to land. The wind direction is from 232 deg.4

So, 232 divided by ten is 23. Runways that are long enough for your aircraft are 09, 15, 27, and 33. Of these, the one closest to 23 is 27. You would request and expect landing runway 27.5

This is a rough outline of the steps a math project would take to guess the landing runway. Most pilots have no trouble hearing the weather advisory, glancing at the Jepp chart, and just knowing which runway should be in use.

Often two digits are used, i.e. runway 9 is called 09.
If a tower controller is present, he will identify and grant access to the runway in use. Your project will calculate the most likely expected runway. With no controller, the pilot should co-ordinate with any present traffic before using your project result.
Notice that reciprocal runways occupy the same paving and perforce have the same length.
Your project must be told whether the reported wind direction is from or toward. When the reported wind direction is toward, as it might be from a non-navigational source such as a local news broadcast, you must calculate the reciprocal from direction.
If you had a plane that could stop in 1200' you would use runway 22.


Bright exhaust in afterburner vs no visible (bright) exhaust when not in afterburner?

It's because on a jet engine the flame in the burner can is carefully controlled and contained by airflow that is guided in from the sides to keep the flame in the center of the burner can so it doesn't touch metal (only maybe a 3rd to half of the airflow out of the compressor gets burned; the rest is for temperature control - which is why there is enough oxygen in the air leaving the turbine to support reheat).  The flame is supposed to be out before the gasses have left the burner can or else the turbine will overheat. The turbine itself is getting burned air that has been mixed with un-burned air to cool it off.

On most engines, if you see a light in the tailpipe of an engine not in reheat, it means there is a flame aft of the burner can in the turbine zone, which is very very bad, except when initially starting and some is briefly visible after lightup.

On some engines, if there is a direct visual path up the tail pipe, through the turbine and stator blades, into the center of the burner can, you may be able to make out a bit of bluish light (should be bluish; yellow light means too rich and the yellow is un-burned carbon fluorescing, like any yellow flame).


Could an aircraft 'hide' in the aircraft shadow of another aircraft without being detected or noticed?

Radar resolution is defined in terms of degrees of arc (or alternatively in steradians/solid angles) and as such, the further away from the radar, the larger volume is being sampled.  At altitude and some distance from the radar you should have a bit of leeway on how loose of a formation you can fly and show up as one contact on the radar display.  I'm not giving credence to the theory presented, but I am saying it is plausible that one aircraft could fly a formation with another and be detected as one airplane by a radar.

If the transponder is off, the aircraft you are following will not see you on TCAS  and if you are behind them you will be visually undetectable by the crew or passengers.  If you fly above them you will be clear of their wake, so I would put behind and above the best position to shadow.  A lateral offset might be safer, but if you stray too much, you might wander into the FOV of the cabin.
I can't see any way the following airplane would cause nav or com interference in the followed airplane.

The biggest threat to being detected in this scenario are being seen by other airplane.  If ATC calls traffic and you see two planes in formation instead, you would probably say something.  In the case of the airplane you refer to however, it was night and if you turn all of your position lights, beacons, strobes, tail lights and if there is no moon out you might escape visual detection by a third party.


Is there an FMC not connected to the AP/FD?

By definition an FMC / FMCS is linked to the auto flight system.

The closest thing to a standalone device is an EFB, but when it comes to fuel burn, and air data parameters, it's unable to compute the complex parameters since it's not connected to the air data computer and engines.

I've checked the history. From a 1985 Sperry ad:

  Since the mid-1970s, when Sperry began developing the first true Flight Management Computer System, the term "FMCS" has been misrepresented almost as frequently as it has been misunderstood. True flight management, defined by the Sperry FMCS, integrates navigation, flight guidance and aircraft performance functions through a sophisticated computer. And in today's marketplace, the "fully-compliant system" which performs exactly as specified by its user in all modes is defined only by the Sperry FMCS.

But yes, that's an ad, so I checked further back, from 1981:

  Arma boasts the first certificated airliner FMS, which is in service with the TriStars of British Airways, Delta, Gulf Air, Pan Am and Saudia. Racal-Decca Navigator is involved on the software side, and also in the support of units outside the USA. The navigation component of the FMS was derived from the earlier Mona TriStar navigation system.

That FMS was connected to the engines and autopilot, so let's check the mentioned Mona TriStar navigation system from c. 1973:

  Mona is not actually a navigation system, in the sense that it does not contain any sensor equipment. Described by its designers as an automated navigation-management package, it can readily be installed in an aircraft to serve as a direct, executive link. It is capable of processing information from the existing airborne navigation system and translating the results into the autopilot and flight director signals needed to maintain en route track, height and speed.

Even that sent AP/FD commands.

Pilot's-eye view of Mona, showing the two control and display units flanking the central electronic chart display.


What is the viability of stacking passengers in an airplane cabin?

I see several challenges with this design, both technological and not:

Making that design safe enough will be difficult, the structure you add in the cabin would need to be strong enough to maintain rigidity in a crash. That much rigidity would add weight, and would add loads to the structure
The pod walls will make it hard to get by people in the single narrow aisle. In an open design you can squeeze by people in the aisle, in a walled design you'd have no place to go
This design would greatly limit carry-on storage to only what could fit under the seat in front of you
Parents with small children and families traveling together would have a hard time with this design as there's no more than 2 seats together, and limited space for sky cots
Access to a sick passenger would be restricted
Passengers with limited mobility would have a hard time getting into and out of these pods
Comfort is the biggest problem I see with this design. Anyone in one of those pods is spam in a can with limited visibility and movement. Personally I think it looks awful and I would go out of my way to avoid flying with an airline using it


What is a rule of thumb for when to begin a descent?

Descent planning for jets can get a little tricky at times, and you have pointed out some of the things to look at when deciding when to start down (assuming that ATC gives you the option to choose your own top of descent).

The descent point is dependant on your aircraft and how much drag there is at your descent speed.  Anything that adds more drag allows you to come down faster, but also makes the flight less efficient since you would have burned less fuel had you just started down earlier without the drag.

A typical jet will descend with the engines at flight idle and the speed at the recommended descent speed, which is usually close to the maximum speed for the airplane.  A good rule of thumb for most jets would be:

  3 miles for each 1,000 ft. of altitude to lose + 1 mile for every 10 KIAS of airspeed that you need to lose before landing.

Example:

We are cruising along at 38 thousand feet and landing at an airport with an elevation of 2 thousand feet which means that we need to lose 36,000 ft.  Let's say that we will be descending at 350 KIAS and need to slow to 150 KIAS for landing:

  Thousands of feet to lose: $38-2=36$ thousand feet
  Tens of KIAS of airspeed to lose: $35-15=20$ tens of KIAS

  Distance = $36\times3+20=128NM$ from your destination

So in this case, we will start down 128 miles out.

There are various factors that can cause this to be a little off, the biggest being the wind.  As the descent progresses, you should mentally double check your progress.  In this case, maybe check when we have 20,000 ft to go (should be 80 NM out now) and when we have 10,000 ft to go (should be 50 NM out now).

If one of your checks indicates that you are a little off, you can adjust your descent rate (adding a little power or using spoilers to descend more quickly) to get back on track.

A slight variation of this uses the same calculations, but instead of using the airport as the "target" altitude and speed, they use a point 30 miles from the airport at 10,000 ft above the airport at 250 KIAS.

The above method is enough to get someone started, and just "works" most of the time.  As a pilot becomes more comfortable with the math, they can start to make adjustments for other factors like:

The effect of the winds at the various altitudes during the descent

Headwinds mean that you can wait a little longer to descend
Tailwinds mean that you should start down a little sooner

Weight of the aircraft

The lighter the aircraft, the later you can start your descent.  (If this seems backwards, consider that when you are heavy it will push the airspeed higher faster as you lower the nose and you will have to raise it to keep from overspeeding.  When light, you can keep the nose further down and will therefore have a higher descent rate.)

The direction that you are approaching the airport from

If you are landing straight in you should start sooner
If you are going to fly a downwind, base, and final, you can start a little later

ATC speed restrictions can prevent you from descending at your normal rate, so you may need to start down earlier.
Inoperative equipment (i.e. spoilers, etc.) may keep you from descending as fast so you may need to start down earlier.

As far as the configuration of the aircraft, in order to get the most fuel efficient profile, I would keep it clean as long as possible and start the descent at a point where I could glide for the majority of the descent and configure on speed for a stabilized landing in the normal landing configuration for the aircraft.  If this is your goal, then the use of spoilers is an indication of poor planning!  ;-)


How common are cancelled landing attempts?

I could see the airport as clearly as one can see an airport in thick fog...

If you saw the runway by looking down from your passenger seat as the airplane passed over the airport on the missed approach, you were looking only through an amount of fog approximately equal to the altitude of the aircraft above the ground. For purposes of discussion, let's say that was 50 meters. The pilot, however, is looking through the front windshield trying to see the runway ahead to position himself for the landing. If he was on a standard 3 degree approach slope, that would mean he is having to look through nearly a kilometer (beware of old man doing math in his head) of fog.

Years ago when I flew for a commuter, I often had to make multiple missed approaches at Pullman, WA, USA in snow storms. My rule was that I would try 3 times before diverting. When we diverted we would often get complaints from passengers about not landing because they could see the airport as we passed over it. I could, too, but only through the cockpit side window, and with featureless snow covered rolling hills, there was no way to position for the landing without losing sight of the airport.

  What might have caused the pilot to actually land the second time but not the first?

The thickness of fog or how hard it's snowing or raining is constantly changing. Try again and you may be able to see what you couldn't before. If you can't, maybe try a third time and get lucky. Trying more that that would mean eating into your fuel reserve to get to your alternate, and, just as importantly in my view, pilot fatigue becomes a problem. Plus, you're beginning to seriously blow your schedule.


Do helicopters fly the same instrument approaches as fixed-wing aircraft?

Helicopters can fly the same standard IAPS.  The visibility minimum is the greater of

a) one half the Category A visibility minima,

b) 1/4 statute mile visibility, or

c) 1200 RVR

We use Category A's MDA/DH. See the AIM 10-1-2 for more information.

Also there are Copter IAPs (example here), and the viz/altitude minimums are stated on those plates.


Where are the seaport conventions for VFR charts explained?

"00 - 50" means a landing surface at 00 feet MSL, unlighted, and 5000 feet (nominal, 4970-5069 actual) long.
At aerodromes with both land and water surfaces, it is customary to suffix the water ones with "W" (pronounced Water, not Whiskey) to avoid confusion.


Does TSR (Time Since Repair) Need A Reset After A Clean/Inspect/Test Workscope?

In an MSG-3 based maintenance program there's no such thing as "overhauled" as in "put back in new condition and reset to zero".  Line Replaceable Units will be qualified operationally and structurally under an endurance/fatigue test program and will normally have a structural life limit where a unit carries structural loads of some kind.  If there is no applied life limit the part can be theoretically run forever (or at least the certified life of the airframe), because under MSG-3, components can be run indefinitely until some form of inspection or test in the field detects a degradation beyond a limit.  Think functional test, leak test, NDT, visual inspection etc.

What happens with LRUs is they may fail or some internal parts may fail during endurance testing. The part was designed to run 80000 cycles, was tested to 120000 cycles (1.5 scatter factor margin for mechanical parts), and say a bearing and thrust washer failed during the testing at 60000 cycles of testing. Those parts will be replaced and the endurance test continued to the end.

But now when it's certified, there will be a need to send the unit in at 40000 cycles (1.5 scatter factor applied to 60k) to "restore" it to its pre-test failure condition.  The unit has to go in, be disassembled and reassembled and any parts that are out of serviceable specs replaced, but the parts mentioned in the restoration task must be replaced, serviceable or not.

Sometimes, a part with a grease charged gearbox will have a restoration applied because the grease was found to be breaking down during endurance testing, and the grease is the only component that must be replaced.  The restoration task in the maintenance program will say specifically what has to be done, as in "replacement of the grease" or "replacement of the Main Ballscrew Thrust Bearing and Washers, PNxxxx and xxxx" (Operators get mighty mad when they send some part in for replacement of grease or 40 dollars worth of needle bearings because the Maintenance Program requires it, expecting a 2000 dollar bill, and the unit comes back with half the guts replaced and a 15000 dollar repair bill because other parts were damaged or worn out prematurely).

When an LRU goes in for repair not related to the maintenance program (like a random breakdown), whatever parts are replaced will be those that are out of service limits or are considered needed for the unit to pass an outgoing Acceptance Test Procedure (functional test in a test rig).  When it comes in for repair, it will get an incoming Acceptance Test done (the same rig test), and if it passes, it may go right back out No Fault Found unless the operator specifically demands it be torn down anyway. In any case, a repaired part does not come with any reset to a Life Limit, but it MAY reset the restoration interval if the restoration requirements were met during the repair.

The Life Limit applies to the root housing (the structural part with the serial number) and when a unit gets to the life limit in total hours/cycles it is scrap even if it was fully "rebuilt" 5000 cycles ago when it was sent in for a repair (so you generally try to avoid doing that).

Anyway, under this type of maintenance program, what needs to be tracked are total hours/cycles since manufacture to which the LRU's Life Limit applies, and hours/cycles since Restoration, (and hours/cycles since functional test, or some inspection obviously) where the maintenance program has a Restoration task applicable to an LRU (like a screw jack that has to go in every 30000 cycles to get a set of bearings changed).

So.. if you had a part with a tag that has "time since repair" on it, that information is not sufficient, and has no real effect on anything, because the only mandatory removal interval under MSG-3 is the Restoration task and the Life Limit.  If a screwjack's tag says it was repaired at 20000 cycles, and there is a 30000 cycle Restoration in the maintenance program, you're going to have to send it back in in 10000 cycles (when it gets to 30k) unless there is language in the shop paperwork that states that parts mentioned in the  Restoration were replaced, or there is a statement something to that effect.  If that's the case, you can now run it to 50k, the next 30k interval.

Then when it gets to the life limit, it is trash even if it just went in and had a complete and total "overhaul" done where everything but the gearbox was replaced, following a random breakdown in the field. An LRU that breaks down a few thousand cycles short of its life limit will normally go in the trash.


That's pretty much how landings turn out on Super Guppy. The aim is to make a three point landing (main and nose wheels touch down simultaneously), but the Super Guppy is a tricky plane to land. Earlier versions were tricky on takeoff too: during takeoff roll their main gear tended to lift off before the nose wheel, this, ofcourse is far from optimal...

This article will give you a nice briefing on this beautifully weird plane (see page three for stuff about landing).

The ones still flying are fitted with Boeing 707 nose gear, which is shorter, sturdier and placed further behing than the original one. Despite this modification, the aerodynamics of the plane are such that it just wants to plant the nose wheel down first. Searching "Super Guppy landing" on Youtube will yield allmost only nosewheel landings.


Why Do Airlines Still Use Tractor-feed Printers?

Probably note directly related to aviation, maybe more to airports than airlines:
Well, dot-matrix printers are expensive, but durable and print at very low cost and finally carbon copies (two, three or even four) of forms could be created. And replacing them will require a lot of software adaptions.
I‘ve seen airports using text-user-interfaces (TUI via terminals), which are often working a lot of better (fast and efficient to use) then usual GUI applications. New stuff, is not automatically good.


Why there is such a strong correlation between the range of an airliner and its passenger capacity?

A big part of the difference in range between small and large aircraft is simply mathematical. When you make a 3D object larger, area increases with the square of length while volume increases with the cube. The A320 has a wingspan of 35.8m, carries 150 (2-class), and carries 24,210L of fuel (standard). The A380 has a wingspan of 79.75m, about twice the dimensions of the A320. However, the passenger capacity increases by a factor of 4 to 644 (2-class), and the fuel capacity increases by over a factor of 10 to 320,000L. There is simply more room for fuel in a larger aircraft. Smaller aircraft may have options to carry additional fuel talks to increase range. Note that this trend also applies to business jets despite their market having less of a correlation between range and passenger demand.

In addition to the geometrical constraints, airlines have other reasons for not operating large planes on short routes, or vice versa, more often. Using small planes allows for more frequent service and more flexibility even if there is enough demand to use a smaller number of larger aircraft.


Is there a way for pilots to report difficulties and challenges experienced during a flight, to the next flight crew?

"Difficulties" are hard to quantify. And it's questionable whether a difficulty experienced by one flight is even relevant to the next. Many difficulties are transient in nature (eg: weather, crew, cargo loading).

However, there is what is known as an Acceptable Defered Defect:

  An identified aircraft defect which has been assessed as being within the requirements of the Minimum Equipment List (MEL) or Configuration Deviation List and has had rectification deferred within a specified limit. Also referred to as a CFD (Carried Forward Defect)

This is used to notify future aircrew of a specific aircraft of any defects which, although does not require the aircraft to be removed from service, may be relevant to its operation.

Pilots absolutely check this before every flight.


Why do Western aircraft manufacturers use FPS system while Russian aircraft manufacturers use MKS system for flight instruments?

The short version is that "Western" countries (nearly all countries, in fact) use knots and such because that's what we started with and, once that became entrenched, the cost of retraining every pilot and reequipping every plane--and the inevitable confusion and crashes during that transition period--greatly exceeds the benefits.

The USSR, PRC and a few others were able to use metric units because they didn't need to care about compatibility with the rest of the world--or perhaps saw the lack of compatibility as a good thing, helping to keep them isolated.


Why do helicopters and airplanes use different headset plugs?

It's a holdover from the old days when microphone technology wasn't as advanced.  The military adopted "dynamic microphones" as the standard, which were less noisy than the alternative "carbon microphones."  Carbon microphones required a DC bias voltage to operate, and the dynamic ones did not.

Fast forward to current airplane microphones, which are electric, and still use a bias voltage, so if you plug a military dynamic microphone into a civilian airplane jack, the microphone would burn out from the voltage.

So what?  Well, helicopters were originally very military oriented, so they all were wired for dynamic microphones.  They used a different jack to avoid accidentally plugging the wrong type of microphone into the wrong type of jack.  Even though helicopters are widely used outside of the military now, the standard remains, and many emergency radio equipment (fire, medical, police, etc) still uses the dynamic standard.


Why is rain above freezing level (altitude) not always "freezing rain"?

The freezing altitude or $0\,^{\circ}\mathrm{C}$ isotherm is the altitude at which the temperature is $0\,^{\circ}\mathrm{C}$ in free atmosphere. This altitude varies and is usually only temporary as it depends on a number of factors.

"Iso0". Licensed under CC BY-SA 2.0 via Commons.

Freezing rain is a condition in which the water droplets become super-cooled (i.e. in liquid condition while below the freezing point of water) and freeze on coming to contact with cold surfaces. This condition happens when snow formed at altitude completely melts and supercools into large droplets.

Source: www.srh.noaa.gov

It can be seen that, to form freezing rain, both warm and cold layers are required. One reason for not encountering freezing rain above the freezing line is that the temperature does not rise above the freezing point of water. In this case, we get snow or sleet.

"Ice Storm Chart" by RicHard-59 based on image by J.R. Carmichael - Own work. Licensed under CC BY-SA 3.0 via Commons.

Thought the above figure is for ground level, it applies for other altitudes also. The phenomenon of freezing rain is dangerous for airliners as the water droplets freeze on coming into contact with aircraft surfaces and can cause loss of lift among other problems.

Post-flight image shows ice contamination as a result of encountering Supercooled Large Droplet (SLD) conditions near Parkersburg, WV. Source: icebox.grc.nasa.gov


Why didn’t the Me 163 experience the serious handling problems suffered by other similarly-designed semitailless aircraft?

Firstly, the Me 163 is classed as tailless, not semi-tailless. The fin does not count.
Secondly, its characteristics were not wholly benign but they were acceptable by the standards of the moment for a high-speed fighter. Its lateral stability was marginal and it could behave unpleasantly in the stall. When Junkers developed it further, they found it necessary to make the leading-edge slots automatically variable and to increase the area of the landing flaps. But on the whole, yes, it was better than most tailless types.
So, why was this particular plane adequate? You will have to bear with me. A long trail of aerodynamic refinement begins with JW Dunne's tailless swept monoplanes and biplanes of the pioneer era. His D.10 biplane became the first aircraft ever to be officially certified as stable. The finless monoplanes could at least be stalled, but simply pancaked down rather than dropping a wing. Around thirty Dunne machines were flown in the UK and US and none ever had a fatal accident, a staggering safety record for that era. Dunne's secrets were many and subtle, expounded to the Aeronautical Society of Great Britain in 1913.
In the 1920s an ex RAF Captain, GTR Hill, took up the unstallable challenge once more and refined Dunne's aerodynamics, developing among other things the mathematics of the constant centre of pressure via reflex camber. A German visitor whose name I forget took it back to Germany where it was further enhanced and there Alexander Lippisch discovered it. He had the luxury of ten years' single-minded research and experimentation on one prototype after another, from glider to propeller to rocket, until the Me 163 emerged. But neither Hill nor Lippisch could get rid of the fin.
Meanwhile the detailed technical work of Dunne received only voice plaudits from others, while that of Prandtl in the early 1930s went unnoticed. Reimar Horten trod the path for himself to arrive at the finless Horten/Gotha flying-wing fighter which also handled well but came too late for wartime production.
What Dunne intuited and tested in hundreds of models, Lippisch half-grasped and Horten rediscovered and calculated, never made it over to Northrop or General Aircraft or any of the others. When Dunne's trademark conical leading-edge droop was rediscovered and used on the Convair deltas to make them flyable at low speeds, the path to it lay through quite another labyrinth. Back in the UK, Dunne and de Havilland renewed their old friendship, for DH had been Dunne's successor at Farnborough and both had trod the corridors of the RAeS together. DH wrote to Dunne that during the development of the DH.108 he would tease his staff that Dunne had got it right all those years ago, so they better had too. But like Lippisch, even he had to keep the fin. And despite also being informed by both Lippisch and the Hortens, his DH 108 was described by one test pilot as "malignant".
The real questions must be; why did so many designers turn a blind eye to the tailoring of span loading and sideways flow to eliminate adverse yaw and the need for a tail fin? and how did they manage to introduce appalling stall characteristics when Dunne's original breakthrough was to tame the stall? The key lessons had been in print since 1913, for those who had eyes to see, and Horten at least had proved capable of finding them for himself. Simple ignorance, preoccupation with conventional design issues and "not invented here" are my best guess. Prandtl's and Horten's contributions are only now beginning to receive wider acknowledgement. The epilogue must go to General Aircraft, whose GAL.56 was described by the ubiquitous Winkle Brown as the most badly-behaved aircraft he had ever flown, before it went on to kill the most experienced tailless aircraft test pilot in the world and who had consequently flown many Lippisch creations, Robert Kronfeld.
For those who want provenance and more detail I fear that you will have to wait until I can get quite a backlog of stuff past our Covid-coma'ed publishing industry. Or you may tread the Science Museum Archive's Dunne Collection for yourself, all 30,000 documents and boxfuls of artefacts of it.


How is a prevailing wind/average temperature study conducted to determine the runway direction and length for an airport?

FAA AC 150/5300-13A ("Airport Design") talks a little about this (you want Appendix 2, "Wind Analysis").

Basically you start by figuring out what kind of aircraft you want to operate at the airport, and establishing some basic wind limits (specifically, the maximum crosswind and tailwind components you want to deal with).

Then you call up NOAA's "National Climate Data Center", tell them where you're looking to build your airport, and see if they can have wind data for the location you're looking to build on.

  If NOAA doesn't have data you have a couple of other options -- another nearby airport's wind analysis can be used (if the topography doesn't vary that much and the wind analysis is "recent"), or you may have to perform a wind survey which basically means placing a anemometers on the site to record the wind speed and direction for a year.

Armed with collected wind data you tally up the number of observations in given wind speed ranges and mark them down on a "wind rose".
You then place your runway(s) on the wind rose so that they're aligned with the prevailing winds and determine your "wind coverage" - the amount of time the winds at your site are within your crosswind and tailwind limits.

The advisory circular I linked to shows you how to do this by hand, but there's also software to do this which is how most folks do it. The FAA even has a handy web form which will generate the wind rose and runway/crosswind limit bars for you.

Note that this is just the wind part. As you've alluded to there are a number of other considerations, like terrain: If the prevailing winds favor runway 36, but runway 36 points right at a mountain a mile from the field you might have to align the runway 33 or 03 and sacrifice a perfect headwind for not having pilots fly into the mountain.
Also as ratchet mentioned the airspace around your proposed site may influence your runway layout and types of operations. There's a separate FAA office that deals with "Obstruction Evaluation and Airspace analysis" and a process to go through to ensure that your airport is not deemed "Objectionable".

Also as you alluded to in your question there are other considerations like density altitude (local temperature and humidity trends) which will influence design factors like runway length - there's another advisory circular (AC 150/5325-4B) that talks about runway design criteria, including length considerations.

For even more than you ever wanted to know about airport design you can check out the full 150-series of Advisory Circulars, which all deal with airports in some way (there are ACs on design, construction, markings, lighting, ARFF, and even how to qualify for and obtain federal aid).


Fuel price actually used in the industry

Jet Fuel is not listed on the commodities exchange, at least not according to this list. For what its worth small boats use regular car gas or diesel fuel and some larger ships are powered by fuel oil but they use boilers as opposed to a reciprocating engine like on smaller boats. Small boat gas tends to command a higher price because it can not because its any different than car gas. This is largely because you cant pull a big boat and take it to the gas station to fill it up every time you need fuel. AvGas for piston pounders is 110 or 100 octane low led. This is every similar to car gas (but higher octane and leaded). It is more expensive since it is taxed differently. Jet Fuel is effectively kerosene.

In the end of the day these are all crude oil byproducts so if you are looking for a commodity price the price of crude oil will effect the price of aviation fuels the same way it effects the price of car and boat fuels. Crude oil prices are about as close as you are going to get.


How often are drop tanks actually dropped?

In general, unless it's an emergency or needed for certain flight operations, the tanks are retained and flown back to base.

There are maneuvering limitations for carriage of certain stores on some aircraft.  The F-16C/D for example limited maneuvering to +6.5/-3 Gs with stores on the inboard two pylons and/or centerline drop tank installed.  If the aircraft was attacked by an offensive flight of enemy fighters, one of the first items prior to commencing ACM with the threat was to jettison stores on these stations.  This allowed the aircraft to maneuver up to a maximum of +9 Gs as the fight commences.


Did Boeing really use ferrets to run wires through aircraft during construction?

No, Boeing didn't do that.
I asked their assembly plant tour
to confirm or deny this, when I found
a report that around 2010 some visitors heard this from a tour guide.  On 2020 Nov 3 they replied:

Hello,
Thank you for contacting us with your inquiry. This is a popular urban myth, there are no records or any other evidence that this was done at Boeing.
Thank you again for your interest.


Airframe parachute on commercial airlines

Cirrus builds very small planes that fly at a very low altitude and at very small speeds, hence the parachutes (CAPS) can be used.
General aviation aircraft are HUGE, BULKY and designed to fly at very high mach numbers. They are not designed to "withhold spin" as required by the CAPS.

Moreover, if this was possible, this would already be in action, because an Automobile accident is not much of a Headache for auto companies, but an Aviation disaster is for sure a PR nightmare for an Aviation Company.


How much compensation does an unruly passenger have to pay to an airline if the flight has to be diverted to remove them?

Unruly passengers can face the following:

Monetary fines
Prison sentences
A ban from that airline

Excerpt from Wikipedia:

  In the United States, passengers who disrupt the duties of a flight
  crew member can face fines up to $25,000 and sometimes lengthy prison
  sentences.

IATA has a policy for these passengers mentioned here, and more information is here.

ICAO has a detailed document on unruly passenger prevention and management. They have adopted a new protocol to amend the Tokyo Convention.


Short answer? The Wright Brothers. The term was coined to describe the Santos-Dumont 14-bis, as its design with a box-like array of forward control surfaces looked like a duck in flight, but the very first successful powered aircraft was a similar canard biplane with a pusher engine.

As planes developed after the Wrights' first flight, this design fell out of favor for a number of reasons. To save weight, the horizontal and vertical stabilizers were grouped together so a single set of braces could support them, and when this arrangement was forward of the wings in the most logical pusher configurations of the day, the planes had a general tendency to nose away from the relative wind, which caused issues with takeoff and landing as well as unrecoverable deep stalls as the plane kept its nose high or even swapped ends in a stall.

These behaviors led to the concept that's familiar to us today, of a central barrel fuselage with the engine and prop in front, the pilot behind that and an "empennage" of horizontal and vertical surfaces in the rear. This arrangement allows for better stability and easier recovery from stalls by having the empennage point the nose into the relative wind, much like a weathervane. The downwash of air over the horizontal stabilizers also allowed that stabilizer to have a reduced pitch angle, reducing drag. These and other advantages led to the arrangement becoming dominant in aircraft design as of WWI (with a couple notable derivations in the early war, like the D.H.2 "pusher" which allowed a machine gun to be mounted along the pilot's line of sight before the invention of the synchronization gear) and continued into the second and third generations of the jet era.

The return to a "pusher"-style powerplant with the modern turbojet led to a revisit of the idea of a forward horizontal control surface. The design has a few advantages, especially in combination with a delta wing which became common on the second-generation supersonic jet fighters. Canards provide a lift force in the direction the pilot wishes the nose to go, instead of opposite that direction, so when pulling up, the canard adds to total lift. Canards also allow the primary pitch surfaces to encounter relatively undisturbed air, as opposed to a tail-mounted stabilizer, which increases the effectiveness of the surface. The larger rearward delta wing acts as the "empennage" of a traditional plane would, helping keep its nose in the wind, and the vertical stabilizer remains at the rear of the plane, avoiding the shortcomings of early canard designs.

Several experimental designs were tried as early as the war years, but the Saab Model 37 "Viggen" was the first aircraft of the modern era to use a canard-delta planform configuration, in 1967. This design has since become a favorite of European designers, with the Gripen, Typhoon and Rafale all following this basic configuration. The Russians have incorporated canards into a few of their fighters like the Su-30 to augment a traditional all-moving tail elevator, and the PAK FA has a similar concept with movable "leading edge root extensions". American designers have played with it, in programs like the F-15 ACTIVE tech demonstrator and the XB-70 prototype hypersonic bomber, but the sole production U.S. aircraft to use canards does so mainly for stability; the B-1B Lancer has a small pair of canards linked to the FBW system which dampens oscillations in the forward fuselage.


What (if any) endorsement do I need to give a student who scored 100% on his knowledge test?

If we're talking about FAA regs I'm not aware of any endorsement required if your student passes the test with a perfect score (they need an endorsement to take the test - I have given the instruction required by..., and they need an endorsement like the one in your question if they fail or don't manage a perfect score).

The endorsement above is intended for use when you need to endorse someone who failed to re-take the exam (similar to what's done if they fail a checkride), or when there's stuff to review from the knowledge test (My instructor combined it in my Checkride endorsement - And has demonstrated satisfactory knowledge of the areas found deficient on the knowledge test.

That said, it is probably a good idea to cover anything the student missed on the exam or doesn't feel 100% confident on, and to log that training - in this case if you do additional ground work you would just log it as you normally do...


What are the FAA regulations on grass airstrips?

I went poking around the FAA Regulatory and Guidance Library until I found FAR 139.307, which states:

  Sec. 139.307

  Unpaved areas.

  (a) In a manner authorized by the Administrator, each certificate
  holder [must] maintain and promptly repair the surface of each gravel,
  turf, or other unpaved runway, taxiway, or loading ramp and parking
  area on the airport that is available for air carrier use as follows:

  ...

  (b) FAA Advisory Circulars contain methods and procedures for the maintenance and configuration of unpaved areas that are acceptable to the Administrator.

So I went looking for those advisory circulars.  There are probably more that I haven't found, but AC 150/5300-13A - Airport Design beginning at page 82 seems to have the sort of thing you're looking for.


How long does it take for a propeller engine to spool-up?

In my Cessna Cardinal, with 360 cubic inch (~5.9L) carburated engine, I push the throttle in and the response is immediate.  Just like stepping on the pedal in a car with a standard transmission because propeller RPM = engine RPM. I have a constant speed prop, with controllable pitch angle, so it sort of acts like a standard transmission, I can dial it to any 'gear' I want to. For take off and landing, the pitch is flattest, and most responsive. Just like in a car, I can dial the prop pitch flatter and add more throttle for a climb from level cruise, then when at altitude I can dial the prop pitch up and throttle back down for efficient cruising. In planes we generally don't go to full thrust instantaneously, that's rough on the engine, but smoothly push the throttle in, maybe 2-3 seconds from idle to full throttle.  During landing, sometimes a bit of throttle is added to arrest an increasing descent rate, and even that is applied smoothly, and rarely full throttle unless a go-around is needed.

This link shows how the oil pressure, springs, governor, and other bits are used to control the propeller pitch when the RPM has been selected.

http://www.boldmethod.com/learn-to-fly/aircraft-systems/how-a-constant-speed-prop-works/


How would a hole in the side of a plane affect its flight?

Most planes fly best without any extra holes, of course! The specific effect of a hole is modifying local airflow, increasing turbulence, and increasing the aircraft's wetted area on the side of the breach.

As long as there isn't a matching hole in the back, however, the airflow inside separates (similar to a pickup truck), so most of the airflow is still normal around the fuselage. The turbulence will also disturb flow over the wing root, if the hole is located forward of the wing, slightly reducing lift on that side. All in all, range will be reduced and more control inputs will be required.

Other than that, a hole in the side does not prevent a plane from operating normally. One can think of a conventional aircraft as the wing, pushed forward by the engine, and stabilized by the tail. The fuselage just connects them together and houses the payload (and controls, but we're not thinking about that at the moment).

Most fuselages are streamlined for minimum drag, but a plane can fly with a non-streamlined fuselage as well, just not as fast and not as far. Fixed-wing gunships, for instance, fly operationally with large holes in their side for the armament.


Why was "taxi into position and hold" changed to "line up and wait" in the USA?

To ensure international consistency. Line up and wait is the standard phraseology used almost everywhere in the world, as defined by the ICAO, so it was confusing for pilots that another phrase was used to mean the same thing when flying to the USA.


Best way of learning the aviation alphabet?

Presuming you're referring to the ICAO Alphabet* , (alpha, bravo, charlie, delta, echo, etc.) the easiest way (in my experience, from learning it as a disambiguator for phone work) is repetition, same way you learned the alphabet as a child, or the same way you'd memorize a poem.  Get a written list of the letter names, read them through several times a day, and over time, start reciting without reading.
Do this several times a day for a week, you'll be close if not there.  A second week and you should start to think in phonetic alphabet.  A third week and you'll wonder why everyone doesn't think in phonetic alphabet.
*corrected from comments, originally International Phonetic Alphabet, which is a whole different thing.


How does PF or "pilot flying" and PNF or "pilot not flying" affect logging?

While the question is fairly broad, looking at 61.51 is a good place to start, as well as 61.57 for some of the currency stuff.
But let's try and work out some of your examples:
How should actual instrument be logged? Should a PNF be able to log actual time if they are monitoring during instrument conditions?
61.51(g) is what dictates the logging of instrument time:

(1) A person may log instrument time only for that flight time when the person operates the aircraft solely by reference to instruments under actual or simulated instrument flight conditions.
(2) An authorized instructor may log instrument time when conducting instrument flight instruction in actual instrument flight conditions.

So barring any legal interpretations out there or regulations I'm missing (note, I'm not an instrument rated pilot nor attorney), a strict reading of the reg would indicate that only an authorized instructor, conducting instrument flight instruction, can log instrument time when not operating the aircraft.
How should landings be logged? Should a PNF be able to log landings they were not at the controls for?
The short answer is no. Assuming the landings are being logged for currency reasons, 61.57(a)(1)(i) states that the person had to be the sole manipulator of the flight controls. 61.57(b)(1)(i) says the same thing, but for night currency.
How should approaches be logged?
Again, I'm guessing this would be for instrument currency, at which point 61.57(c)(1) would be in play.

Within the 6 calendar months preceding the month of the flight, that person performed and logged at least the following tasks and iterations in an airplane, powered-lift, helicopter, or airship, as appropriate, for the instrument rating privileges to be maintained in actual weather conditions, or under simulated conditions using a view-limiting device that involves having performed the following -
(i) Six instrument approaches.
(ii) Holding procedures and tasks.
(iii) Intercepting and tracking courses through the use of navigational electronic systems.

Again, I'm not an instrument pilot, but despite "sole manipulator of the controls" verbiage being absent in this particular paragraph, I'm guessing the FAA would construe it to be the same.
Of course, I'm more than happy to be corrected should I be wrong.


Blunt noses subsonic drag - why a complete ellipse?

What you are missing is suction on that round nose which adds some thrust.

Granted, around that stagnation point there is a pressure region which also acts on a forward-facing surface, thus creating drag. But that region is small. Thanks to the curvature of the elliptic nose shape, air accelerates quickly out of this high pressure region. In order to follow the curved surface, the pressure has to fall below ambient on a still somewhat forward-facing area so the air is actively pulling the nose forward. No such suction can be expected on the straight contour of a pointed, cone-shaped nose.

The plot below only shows an airfoil, but flow around an elliptic nose is quite similar.

CPV plot from XFOIL, showing local pressure as arrows. Suction is pointing out, pressure into the contour. Length denotes difference to ambient pressure.


What does the flashing green-light signal (return for landing) actually mean to NORDO aircraft?

What I was taught that this meant was ...

... because they could not communicate with you, but they wanted you to not land on this pass (interval a mess, crossing traffic, winds maybe wrong, a dozen other things that might crop up) it was more or less "the runway will be ready for you if you take another lap in the pattern." This also gives them a bit of time to get all of the other aircraft in the pattern out of the way of the aircraft in distress. (And the steady green ought to confirm that on the next pass, if all things go well).

Tower operators would rather get that aircraft who can't talk to them onto the ground.  What they want to avoid in this case (again, this is what I was taught by a salty old Navy controller when I was in flight school) is that they wanted to avoid the aircraft attempting to land being "spooked" by a red light and thinking they can't land at this field.  And then waving off and flying off in search of another field while still NORDO.

The green light is the 'friendly' light between choices of red and green. Put in the chief's colloquial jargon: "Flashing green lets the pilot know "the runway will be there for you when you come back for your next approach."

The Canadian Aeronautical Information Manual, which has all of the signals to include the two that are relevant to this question, can be found here.

The teaching that I got may no longer be current, but the lights shown to a NORDO airborne aircraft still mean the same thing as they did when I was taught.

  Steady Green:  cleared to land
  Flashing Green: return to land (to be followed at the proper time by steady green)


What is the total EXTRA lift produced using an 80 deg flap and distributed propulsion?

A 30° flap is a typical landing setting. Increasing that to 80° is only adding more drag. Your 25 hp thrust will only add a mild breeze and will not help to reach that 30° AoA unstalled. Better use 8° or 10° of flaps (depends on flap chord) and do not rotate to more than 10° AoA.


Yes you can log time as safety pilot where you are taking legal responsibility for maintaining VFR separation during hood practice.  Otherwise it has to be a multi-crew situation by operating rules or due to the aircraft type.  This covers it pretty good.  https://www.aopa.org/training-and-safety/learn-to-fly/logging-cross-country-time/logbooks-and-logging-time


14 CFR 105 covers parachute operations in the USA.

There is not a requirement for a NOTAM, but since this happened at an uncontrolled airport the nearest ATC facility must be notified at least 1 hour in advance but not more than 24 hours in advance and, they must have approval from airport management.

Then for the actual jump, ATC must be notified at least 5 minutes prior to jump via radio from the aircraft.

  §105.23   Parachute operations over or onto airports.

  No person may conduct a parachute operation, and no pilot in command
  of an aircraft may allow a parachute operation to be conducted from
  that aircraft, over or onto any airport unless—

  (a) For airports with an operating control tower:

  (1) Prior approval has been obtained from the management of the
  airport to conduct parachute operations over or on that airport.

  (2) Approval has been obtained from the control tower to conduct
  parachute operations over or onto that airport.

  (3) Two-way radio communications are maintained between the pilot of
  the aircraft involved in the parachute operation and the control tower
  of the airport over or onto which the parachute operation is being
  conducted.

  (b) For airports without an operating control tower, prior approval
  has been obtained from the management of the airport to conduct
  parachute operations over or on that airport.

  (c) A parachutist may drift over that airport with a fully deployed
  and properly functioning parachute if the parachutist is at least
  2,000 feet above that airport's traffic pattern, and avoids creating a
  hazard to air traffic or to persons and property on the ground.

  §105.25   Parachute operations in designated airspace.

  (a) No person may conduct a parachute operation, and no pilot in
  command of an aircraft may allow a parachute operation to be conducted
  from that aircraft—

  (1) Over or within a restricted area or prohibited area unless the
  controlling agency of the area concerned has authorized that parachute
  operation;

  (2) Within or into a Class A, B, C, D airspace area without, or in
  violation of the requirements of, an air traffic control authorization
  issued under this section;

  (3) Except as provided in paragraph (c) and (d) of this section,
  within or into Class E or G airspace area unless the air traffic
  control facility having jurisdiction over the airspace at the first
  intended exit altitude is notified of the parachute operation no
  earlier than 24 hours before or no later than 1 hour before the
  parachute operation begins.

  (b) Each request for a parachute operation authorization or
  notification required under this section must be submitted to the air
  traffic control facility having jurisdiction over the airspace at the
  first intended exit altitude and must include the information
  prescribed by §105.15(a) of this part.

  (c) For the purposes of paragraph (a)(3) of this section, air traffic
  control facilities may accept a written notification from an
  organization that conducts parachute operations and lists the
  scheduled series of parachute operations to be conducted over a stated
  period of time not longer than 12 calendar months. The notification
  must contain the information prescribed by §105.15(a) of this part,
  identify the responsible persons associated with that parachute
  operation, and be submitted at least 15 days, but not more than 30
  days, before the parachute operation begins. The FAA may revoke the
  acceptance of the notification for any failure of the organization
  conducting the parachute operations to comply with its requirements.

  (d) Paragraph (a)(3) of this section does not apply to a parachute
  operation conducted by a member of an Armed Force within a restricted
  area that extends upward from the surface when that area is under the
  control of an Armed Force.

Even more information is available in AC 105-2E.


What does AO2 in the remarks of an ASOS/AWOS mean?

The AO2 notation means the station is automated and has a precipitation
discriminator. AO1 means automated but no precipitation discriminator. The precipitation discriminator will be able to sense the difference between rain and snow.

The METAR format is documented in the Federal Meterological Handbook No. 1 in Chapter 12. This particular notation is:

  12.7.1 c.
  Type of Automated Station (AO1 or AO2).
  AO1
   or
  AO2
   shall be coded in all METAR/SPECI
  from automated stations.  Automated stations without a precipitation discriminator shall be identified
  as
  AO1
  ; automated station with a precipitation discriminator shall be identified as
  AO2
  .


Why Consumer Drones don't use multi-blade (more than 2) propellers?

There are a number of related questions on the site for more information about this. I'll link them below.

The short answer is that two blades will be the most efficient use of energy. If the drone needs a better climb rate then adding extra blades is an option, since you can't make them any longer. The downside is that it will reduce efficiency and thus your battery time.

I can't find the question at the moment, but Peter Kämpf mentioned in an answer that theoretically one blade would actually be most efficient except that you would have to provide counterweight to balance it. The counterweight with no excess thrust would negate the advantage, but that's just an illustration of how the fewer blades the more efficiency.

Here are the links for more reading:

What's the difference between a two-blade prop and three-blade?

Is a propeller with two long blades more efficient than one with three shorter blades?

How does blade solidity ratio relate to thrust/power/torque of a propeller?

Why are three-bladed helicopters relatively rare?


Who should handle an emergency when there's both a certificated pilot and a CFI on board?

From a safety perspective both pilots should be handling any emergency that arises, each working to their individual strengths and expertise to ensure a safe outcome.
This is exactly what you did in the scenario you describe.

In terms of who calls the shots (acts as PIC for the emergency), generally the most qualified pilot onboard should be the one giving the orders. Deciding who that is falls to the pilots onboard (because they're the ones who will arrive at the scene of any resulting accident first).

So in my mind the question really is "How do I determine who is most qualified?" -- Any opinion we can give here comes dangerously close to second-guessing your emergency actions which is something I personally try to avoid, but I'm going to embellish your scenario above for illustrative purposes:

The Instructor
Former air force pilot ATP, CFI/CFII, MEI.
10,000 hours in various jets, 10 hours in an Arrow (doing this instructing gig.) and for the sake of argument no other time in PA-28s.
You
PPL + Instrument Rating, working on your Commercial.
300 hours, 200 in fixed-gear PA-28s and let's say 20 in Arrows.

I'll further assume you both kept your cool and didn't panic (because if either of you turned into a quivering blob that would automatically disqualify them from taking control of the aircraft).

If we go by the certificates, your instructor is certainly "more qualified" - and in 10,000 hours they've probably dealt with more real-world emergencies than you have.

If we go by "time in type" and experience flying PA-28 variants you're clearly more familiar with the general type, and possibly this specific aircraft & systems (like the emergency gear extension system).

Given the above, having you handle the controls seems to be the most logical course of action. The CFI can do "everything else" - communication, traffic scan, calling out checklists & altitudes, etc. - to ensure that you can concentrate on flying the plane and landing as safely as possible.


Is flying during the day safer than flying at night?

First, I should reiterate that commercial flights at any time of day are extremely safe.  Saying flights at night are more dangerous is like saying going to buy groceries at night is more dangerous.  It may be true, but it shouldn't be something a traveler worries about.

It seems from the available data that accidents are at least more dangerous at night, even though I can't tell if accidents are more likely. Certain kinds of accidents, like weather-related accidents or disorientation, are also more common at night than during the day.

A great source for this is an incident database that you can download from the NTSB database of aviation incidents (there's a link on the page for downloadable datasets).   Opening the downloadable dataset in Access lets you find statistics for whatever criteria you want. I filtered for records with aircraft operating commercially (not general aviation or commuter) with light conditions (like day vs. night) available.

In this dataset, 1562 incidents occurred during daylight, dawn, or dusk, and 635 occurred at night, or about 29% of all incidents (Incidents include procedural violations and near-misses as well as accidents that cause damage or injury).  To figure out how likely an accident is at night versus the day, we would need to get data on traffic volume that matches the dataset I'm using.  Unfortunately, I don't have that information, but we can look at other statistics to see whether these night incidents are more serious.

Of those incidents, 5.6% of incidents during the day had at least 1 fatality and 8.9% of night incidents had at least 1 fatality.  Also, only 1.6% of incidents during the day had at least ten fatalities compared to 2.5% at night. This confirms that night incidents are slightly more likely to be fatal.  It's also worth noting that among accidents reported as "dark night," 9.7% were fatal, showing only a slight increase from other night conditions.  The percentage of total fatalities that happened at night is a bad statistic because a large amount of those fatalities come from a few large crashes.

In a closely related statistic, 49% of the incidents during the day were not classified as "accidents," compared to 41% at night.  This means the margin between an incident and a full-scale accident is narrower at night.

Some kinds of incidents are also far more common at night than during the day. 27.4% of incidents were marked as involving a weather condition at day versus 38.7% at night (which is surprising considering that thunderstorms and turbulence are less common at night).  Other incident codes that represent a larger share of the incidents at night include "became lost or disoriented," "minimum descent altitude," "crew/group coordination," "airport facilities," "object," and, unsurprisingly, "light condition."  Surprisingly, the following were not unusually common codes for night incidents: "terrain," "anti-ice," and "taxiway lighting" (wait what?).  Some of these codes (like for taxiway lighting related incidents) are so rare that the statistics for them are unreliable.

I looked at the set of flights recorded by the NTSB since 1982 with light condition recorded and FAR part listed as 121, 125, 129, or "NUSC" (I make no guarantees that this dataset is an unbiased representation of all incidents since many crashes are excluded from these criteria).  Dawn and dusk were considered during the day when counting.  I'm counting by plane technically, not by incident.


Are there any footwear regulations for private pilots?

There is no policy on the books that I can find in regards to this. Loosely if flip-flops make it hard for you to operate the rudder it would fall under the catch all:

  § 91.13 Careless or reckless operation.

  (a)Aircraft operations for the
  purpose of air navigation. No person may operate an aircraft in a
  careless or reckless manner so as to endanger the life or property of
  another.

However I was at an FAA WINGS lecture not all to long ago on preparing for accidents. My local FSDO's advice was to "dress for the crash" i.e. if you plan to fly over snowy terrain consider wearing boots etc. With this in mind flip-flops are more than likely not a great choice. The need to walk considerable distances over terrain is not unheard of after an accident.


Why does the takeoff N1 limit start to decrease below 30°C OAT?

There are basically 3 limits that the engine faces, temperature (maximum turbine entry temperature or maximum compressor exit temperature), pressure (maximum compressor exit pressure) and stress (maximum stress in the blades as a result of spool speed).
Varying the OAT for a specific engine design will hit one of these limits. When the OAT increases, the amount of fuel you can add to the system reduces as you get over-temperature, when the OAT decreases you could add more fuel, but that will increase spool speed which is also limited. From this figure you see the effects on SOT (turbine Stator Outlet Temperature, equivalent to Turbine Inlet Temperature, TIT):

But why does the takeoff N1 limit start to decrease with a decrease in the OAT below 30 degrees Celsius?

The limit on the left is the decrease in spool speed, note that the corrected spool speed is constant (N / √(T)) so for a lower temperature, the N also decreases.

It's easy to understand why the takeoff N1 limit decreases with an increase in the OAT in the chart above

Yes it is, this is limited by the turbine inlet temperature (or a maximum exhaust compressor temperature as used in the image above). The maximum turbine inlet temperature is fixed, the higher the inlet combustor temperature (exit high pressure compressor temperature), the less fuel can be added to heat to the air in the combustor, the less energy is available to expand in the turbines.
The constraining of the power is called flat rating.

This effect can be simulated with an engine model. If we would vary OAT for a certain power setting, e.g. constant (corrected) spool speed for a large bypass turbofan engine with imposed compressor exit pressure and turbine inlet temperature limit a model would look like:

After the variation of OAT you will yield the blue performance curves for a non-limited engine, and the black dashed curves for a limited engine:

Note that the compressor outlet pressure is the limiting factor in the graph on the left, but spool speed and compressor pressure are linked. The question is which of the 2 is reached first, this depends on the input and the design constraints.


Why is rotating engines in opposite directions more important for a propeller-driven plane than a jet?

This is sort of explained in the linked question already. Specifically this answer (which I consider better than the accepted one above it) says:

  Today, high power propeller aircraft tend to use identical engines but left- and right-handed gearboxes so the propellers run in both directions. This is less due to gyro effects and mostly to produce benign stall characteristics. The prop wash of a propeller increases the local angle of attack on the wing on one side and decreases it on the other side, so the wing will stall first on the side with bigger angle of attack. If this side is always to the right of the propellers, the aircraft will roll right in a stall.

In a turbofan the nozzle directs the flow below the wing aft of the leading edge, focuses it more and uses guide vanes to stop its rotation, so this effect does not occur. This eliminates the most important factor for deciding to use counter-rotating propellers.

Combine with the fact that most turbofans are not geared, so the whole engine would have to be mirrored, which would complicate maintenance a lot more than just having mirrored gearboxes and propellers does for turboprops.


Can a pilot fly through a restricted area while flying on a Victor Airway?

Short answer: yes, with permission. Whether or not you're on an airway isn't really relevant.

The basic regulations on restricted airspace are in 14 CFR 91.133 and they apply to all aircraft on all flights:

  (a) No person may operate an aircraft within a restricted area
  (designated in part 73) contrary to the restrictions imposed, or
  within a prohibited area, unless that person has the permission of the
  using or controlling agency, as appropriate

The AIM 3-4-3 also makes it clear that you can enter restricted airspace (my emphasis):

  Restricted areas contain airspace identified by an area on the surface
  of the earth within which the flight of aircraft, while not wholly
  prohibited, is subject to restrictions.

And it has details of how ATC handles IFR traffic:

  1. If the restricted area is not active and has been released to the controlling agency (FAA), the ATC facility will allow the aircraft to
  operate in the restricted airspace without issuing specific clearance
  for it to do so.

  2. If the restricted area is active and has not been released to the controlling agency (FAA), the ATC facility will issue a clearance
  which will ensure the aircraft avoids the restricted airspace unless
  it is on an approved altitude reservation mission or has obtained its
  own permission to operate in the airspace and so informs the
  controlling facility.

In other words, you can fly through restricted airspace if the controlling agency gives you permission, either directly or via ATC. In the specific case of the Camp Pendleton restricted areas, the Los Angeles sectional says that you should contact LA Center or SoCal TRACON (for R-2503D), and shows that the areas are not active 24 hours per day:

So in theory you can fly through at 3am without asking anyone, but if you're planning a flight that goes through a restricted area you should make sure you get a flight briefing and ask the briefer about that point specifically. And it wouldn't hurt to confirm again in the air before entering, in case the areas 'go hot' suddenly.


Is there a software to calculate parameters from certain inputs on a flying wing?

Yeah you could start with X-plane, which claims that it can figure out the flight characteristics from geometry parameters. It is based on laminar flow theory and on classic aeroplane shapes and configurations, but it is a start. They have something called Plane Maker which could serve your application.

FlightGear is a similar program, open source so you can study the code to see how it works, then try to find relevant lift and drag data on the interwebs, NASA servers for instance.

Good luck with the modelling effort.


How could I find  lift coefficient slope?


With an EASA PPL, can I invoice my mother's company for airplane rental to fly her to a convention, with no other renumeration?

In the UK, at least, the rules specifically state:

  Privileges and limitations:
    A holder of a PPL may, for compensation or hire, act as a crewmember of an aircraft in connection with any business or
  employment if—

  a. the flight is only incidental to that business or employment; and

  b. the aircraft does not carry passengers or property for compensation or hire.

Despite what this may sound like, this means you are not allowed to be paid for flying unless you happen to be an employee and flying for work -- e.g. an archaeologist (with a salary from University X) flying yourself and a colleague to a dig site (while employed at the University of X -- thus flying for compensation [because you are paid, indirectly, to do this] but incidental to the employment [the University of X is not an airline, and the colleague you are with is not a co-pilot or paying passenger]).

I have always been taught that the safest thing to think is this: As a PPL, you cannot fly for compensation, and each of your passengers at most has to contribute not more than their "fare" share of the cost of the flight.

By invoicing your mother for the cost of the plane rental you would not be contributing that value in kind, and thus would be in violation of this rule (with rather unpleasant consequences, should you be caught -- ranging from losing your license to a minor criminal conviction). Moreover, the fact that you mentioned the word invoice makes me think that your mother's company would be expecting you to provide a service -- all of these are commercial terms, and alarm bells would be ringing in the mind of any examiner looking at this from the outside, as it starts to really sound like you're providing a service for hire.

Ignoring for the moment that many organisations have rules about doing just the following with family members, I suggest instead keeping all of the receipts of your legitimate expense for aircraft hire -- Hobbs hour fees, fuel, landing, whatever -- and then getting your mother to claim exactly half their value as a business expense. That at least makes it very explicitly clear that you are paying your fair share of the cost of the actual flight, and highlights the nature of the compensation as covering an expense, not a fare.