Did A320 NEO need an equivalent to 737 MAX MCAS because of its bigger engines?

The A320 and 737 have very different flight control architectures.

The 737 has physical cables that transmit pilot (or autopilot) input directly to the hydraulic actuators. This was common in the 1960's when the airplane was first designed. This means that the airplane handling comes down to the aerodynamics and the pilot input.

The 737 MAX presented an issue when it was found that certain situations approaching stall could cause the airplane to pitch up, exacerbating the stall, rather than naturally pitching down and recovering as expected. This was due to the larger engine nacelles, which are located ahead of the center of gravity. An aerodynamic change would have taken lots of time and money and had its own drawbacks. Instead, Boeing created MCAS. This applies trim to help to pitch the airplane down when it reaches high angles of attack.

The A320, on the other hand, was designed as a fly-by-wire aircraft. This means that a computer is using sensor inputs to control the airplane all the time, and pilot or autopilot inputs only provide a guide to that computer control.

Fly-by-wire allows some helpful safety features, such as not allowing the airplane to exceed the design envelope, including stall. This means that any A320 in normal conditions will allow the airplane to reach a maximum angle of attack and no higher. Any aerodynamic differences such as a different fuselage length, larger engines, etc, are countered by the flight computer. Other than some possible fine tuning of the control laws of the fly-by-wire system, the A320 neo would not need any special new system to control angle of attack.


Could an aircraft like a Boeing 777 take off with flaps fully deployed?

Given the right weather, and takeoff weight, yes it could leave the ground. Will it be able to attain the regulatory climb gradient? Probably not. Will it be safe in case an engine fails? Most definitely not.

Landing flaps add lots of drag. That's why they are retracted during an aborted landing for example.

On takeoff, too much flaps means you can stop easier if an engine fails. But it also means you need longer distance to accelerate if the decision is to continue. That means the go-speed will be slower than the stop-speed. See: How is minimum runway length related to V1?

There can't be two decision speeds. Limiting the flight to the slower go-speed will significantly limit how much fuel/payload the plane can carry. And of course if an engine fails during the initial climb, the remaining engine won't be able to keep the plane climbing at a safe rate.

Manufacturers test the different configurations in all conditions, such as weight, runway length, winds, etc. After the data is collected, and with some interpolation, the takeoff and climb performance tables are produced and approved by the regulatory bodies. Any configuration used that is not approved would fail the regulatory and safety requirements, and put everyone in great risk.


Can light aircrafts with no retractable landing gear make an emergency water landing?

Can they land on water? Yes.

  Most pilots contend that the ideal airplane for ditching is a low-wing aircraft with landing gear retracted. Statistics, however, do not substantiate this. Aircraft geometry and landing gear configuration do not appear to affect survivability appreciably. (Source.)

If you try this Google search, you'll find plenty of high-wing fixed-landing-gear water/sea/ocean landings. The outcomes for the occupants vary.

In Oct 2015:

  The [Cessna 152] was ditched in the [waters off Grand Bahama]  after experiencing a technical failure. Both trainer pilot and trainee remained unhurt.

In Dec 2013:

  The Makani Kai Air Cessna 208B Grand Caravan impacted ocean waters shortly after takeoff from Kalaupapa Airport (PHLU), on the island of Molokai in Hawaii. The airplane sustained substantial damage. The pilot and two passengers were seriously injured, one passenger was fatally injured, and five passengers received minor injuries.

Related: What are the risks in landing on a beach vs. shallow waters?


Does wind provide lift for hang gliders in the air?

Yes, it's called ridge lift. From Wikipedia:

Ridge lift (or 'slope lift') is created when a wind strikes an obstacle, usually a mountain ridge or cliff, that is large and steep enough to deflect the wind upward.
If the wind is strong enough, the ridge lift provides enough upward
force for gliders, hang gliders, paragliders and birds to stay
airborne for long periods or travel great distances by 'slope
soaring'.

https://en.wikipedia.org/wiki/Ridge_lift
If you happen to be in the San Diego area on a nice summer day. Go to the Torrey Pines glider port above Black's Beach in La Jolla and just north of the Scripps Institution of Oceanography. The onshore wind striking the bluff overlooking the beach is forced upwards and provides plenty of lift for hang gliders working their way back and forth.
You can see images of people doing that at the Torrey Pines Gliderport website or just Google "torrey pines gliding images" for additional images.


Why is vertical take-off restricted to lighter weight aircraft?

Essentially it comes down to supersonic rotor tips

With a plane, in theory you can make it pretty much as big as you like - as long as you have strong/light enough materials, and can keep adding power, an aeroplane design scales pretty well. Bigger wing = more lift. As long as you can make the wing bigger without it breaking, and as long as you can add enough power to overcome the extra drag, there aren't many fixed limits

With a helicopter, we're limited by the rotor tips: once they go supersonic, they cause a lot of problems.

So how does a helicopter produce lift? By using rotors to push air down within a kind of circle. To add more lift we can do (essentially) three things.

Make the rotor spin faster, so it pushes more air down in the circle it already uses. Obviously this makes the tips spin faster, so we can only do it to a certain extent. We've already hit this limit.
Make the rotor blades longer, so they push a bigger circle of air. Again, though, due to the nature of a circular blade, the outside of a blade is moving faster than the inside. For a certain rotor speed, there's a fixed limit to how large the blades can be. Again, we've already hit this limit
Add more blades, so there are more blades producing lift. This works to an extent (hence why smaller helicopters may have two rotor blades, but larger ones have 4, 5 or more. Again, though, this doesn't scale indefinitely - each rotor interferes with the next, you can't just keep adding more

There are other slight modifications we can make, such as the airfoil of the rotor, but they don't add significant gains

So, basically, we've hit the limit of what we can lift with a single rotor, The only real way to add more lift now is to add more rotors: doing that would be far less efficient than simply using an aeroplane.

Which brings me to the final point - helicopters are very inefficient and pretty slow... We simply don't need, except in a few niche circumstances, to carry more weight with them.


This is a very good idea and has already been done. It is called a slat and is positioned ahead of the wing where it will do a better job of turning the airflow and not causing the slat to stall, as shown on your diagram. Slats allow a 10-12 degree higher angle of attack before the wing stalls. Fixed versions in this more forward position have lower drag in cruise.

source

The reason a more forward placement is superior can be seen in the streamlines of the airfoil at high AoA. The inlet gap between the slat and wing is located right at the airstream stagnation point. This is where air pressure is greatest, enhancing the operation of the slat.

source


What are the most common uses of radio communication when flying?

It will be hard to list everything that is said, but I can try to start with some of the basic examples:

Pilot is ready to taxi to the Runway
P: Tower, N12345, has information Tango, at South Parking, ready to taxi.
T: N12345, taxi to runway 13 via Alpha, Delta.

Pilot is ready to take off
P: Tower, N12345, is ready to go at runway 13. Request SouthEast Departure
T: N12345, cleared for takeoff, SouthEast Departure approved.

Pilot wants to cross another airspace
P: Tower, N12345, is 10 miles to the East, 1,500, request transition east-to-west
T: N12345, transition approved as requested.

Pilot wants to approach an airport to land
P: Tower, N12345, is 10 miles to the South, 1,500. To Land
T: N12345, make Left-traffic for runway 17; report a 2 mile final


What is the spacing of obstacle lights on towers?

In theory you might be able to make an estimate, but practically speaking it's impossible and a lot easier to just look at a sectional chart.

The FAA has a detailed guide on obstacle lighting standards, which usually applies to structures over 200ft in height but there's a lot of possible variation:

  Recommendations on marking and/or lighting structures can vary
  depending on terrain features, weather patterns, geographic location,
  and in the case of wind turbines, number of structures and overall
  layout of design.

The actual number of lights and their placement depends on the type and size of the structure. Appendix 1 of the FAA guide has examples for water towers, radio masts, cooling stacks, bridges, chimneys etc. The vertical light spacing seems to vary from 250-375ft, depending on the structure type, but I didn't go through it systematically.

So if you have plenty of time you might be able to determine the approximate height of a structure by comparing its lighting layout to the guide and estimating based on that, but that's very unlikely to give you an accurate number. For a pilot in flight or planning a flight, that isn't safe or practical and the simple solution is to just look at the VFR sectional chart to get the height. For example, this tower is 1094ft high and the top is at 1994ft above sea level (so the ground level is 900ft above sea level at that location):


Yes, it should. In the end, p-factor is just a funny word for the out-of-center shift of the thrust vector, and if the vector is larger, the effect should be equally larger.


Can all helicopters hover, and how long does it take to "stop"?

As noted in another answer, all helicopters can hover, but a so-called "high hover" (out of ground effect or especially at operational altitude) is a more difficult maneuver, requiring more power than a ground hover, and being harder to maintain (because reference points are much further away).

Helicopters generate more lift for the same power when in forward flight, and transitioning from forward to hover requires a well-controlled combination of adding power, adjusting collective, and maneuvering cyclic (in both axes) and anti-rotation controls -- which is to say it's much harder than simply flying forward at low speed.  In general, once aloft and flying forward, it's much easier to continue forward flight (it's also safer, since in the case of a failure, autorotation works better if you already have some forward speed).

Hovering on instruments is even more difficult than a high hover -- so if visibility is a problem, it's generally far better to continue forward flight than to attempt a high hover.


What aspect ratio is best for Wind Tunnel Testing an aerofoil with Small Additives?

What is it you want to test?

Do you want to test the 2D characteristics of an airfoil? Then make it the width of the windtunnel. The wind tunnel walls act like mirrors, so you will have the behaviour of an infinite wing.

If you want to test a 3D wing on a model, you need to use coherent scale. Use the same scale for the fuselage/wing/empennage.


Is making faster military fighters even practical?

In the 1960, faster fighters were seen as desirable as they could outrun 1960s technology missiles to an extent (see the reports of SR-71s being fired on but never hit by SAMs). Of course, missile manufacturers saw this and developed faster missiles and longer-range radars to negate this advantage. And as it is much easier to make a missile faster than it is to make a large aircraft faster, that's an arms race the airplane manufacturers always lose.

While high speed allows you to outrun missiles, it also reduces maneuverability: at Mach 3, a constant-G turn will be much larger than turning at the same G level at Mach 1.


Can I make an ILS-Approach when I am VFR?

Sure you can.  Just request to fly the approach using either radar vectors or initial approach fixes, if available.  The tower will usually comply and grant you the approach clearance, adding "maintain VFR" i.e. The approach should be flown under visual flight rules and you cannot use a view limiting device unless you have an appropriately rated safety pilot onboard with access to dual flight controls.

For non towered airports, you will need to listen for traffic in the area on the CTAF and provide position reports often for the benefit of other pilots in the pattern.

Flying practice instrument approaches in VFR is quite common and many pilots do this to maintain instrument proficiency.  It is also common for instrument rated pilots to file a local IFR flight plan to practice as well.


How are the compressor and turbine disks connected?

From The Jet Engine, Rolls Royce, issue 5: a compressor drum assembly. There are holes at the lower bit which attaches to the shaft, and another section of the book mentions hundreds of holes for bolts. These holes might be for fasteners.


Could someone use an axe to break through a locked cockpit door?

Axes are not carried in the cabin and the door is designed to resist attack using tools available in the cabin

  Fire/crash axe/crowbar. Fire axes were provided to obtain emergency access to areas and parts of the airplane which are not easily accessible (e.g. behind sidewall, electrical or ceiling panels). The handle is insulated to protect against electric shock. In the past, fire axes might be found in the flight deck and in the passenger cabin but on most carriers, in compliance with anti-terrorism regulations and procedures, axes are no longer carried and have been replaced by insulated crowbars in the passenger/cargo compartment.

From http://www.skybrary.aero/index.php/Cabin_Fire


What is this plane seen in the Falcon Crest TV series?

That's a Cessna 210 Centurion II
.
The Cessna 210 models K, L, M, N and R have the windows shaped like the one shown in the picture from Falcon Crest. If it has a two-bladed propeller, it is a model K, the others have three-bladed props.
The picture below is a Cessna 210M.

source: www.airhistory.net, photo copyright: Phil Vabre


What are the consequences of an airline pilot deviating from a flight plan to perform a random maneuver?

As long as the pilots clear it with ATC and it doesn't violate the general rule against careless or reckless actions, there is nothing illegal about it. Pilots frequently request minor route changes, and ATC generally grants them if conditions permit. For instance, aircraft departing SFO often request a scenic pass by the Golden Gate Bridge as a treat for themselves and/or their passengers.

As long as no laws are broken (see above), their employer won't know whether the deviation was initiated by ATC or by the pilot, nor would they probably care even if they did know.

OTOH, if a pilot deviates from ATC instructions, it could potentially get them killed, so few pilots would knowingly do that. Deviations are almost always unintentional, and unless the pilot has a history of such problems that calls his qualifications into question, he/she will most likely get a "counseling" session and perhaps some refresher training.


Why would Emirates fly over Iraq, avoiding Iran?

Since December 2017 the Iraqi airspace is used by Emirates again, after Iraq declared the victory over the Islamic State.

Now there are basically two routes to choose between when flying from Turkey to Dubai.

One route passes through Iran  and make it look like the flight is explicitly avoiding Iraq. The route crosses the Ankara FIR / Tehran FIR border just north of Iraq, before turning south towards Dubai, such that it just stays outside Iraqi airspace.

The other route (UM688) passes through Iraq and makes it look like the flight is explicitly avoiding Iran. The route structure in Iraq is such that the north-south routes follow the Iran border in order to avoid the military activities near the Syrian border.

The map below shows the route structure with two routes through Iraq highlighted (UM688, Southbound and UM860, Northbound).

source: Flight Service Bureau

It is likely that the choice of route is made based on financial reasons. From looking at recent flights, Emirates seems to have a preference for flying over Iraq, but occasionally flies over Iran.

The ATS overflight fees of Iraq are at \$3751 (approx. \$0.38 per km) considerably cheaper than those of Iran. Iran charges \$0.004061 per 1000 kg Maximum Take-off Mass (MTOM), per KM, with a 30% reduction for the MTOM in excess of 150 000 kg. For an A380, the cost of crossing Iran would be approximately \$2800 (approx. \$1.80 per km). The slightly longer flight over Iraq, Kuwait (~\$1351 ATS fees) and Bahrain (~\$2101 ATS fees) would consume more fuel but will still be cheaper than crossing Iran.

A reason for crossing Iran occasionally might be that Iraq's airspace is very congested since the re-opening of the airspace. To avoid delays, sub-optimal altitudes or adverse meteorological conditions it may be more attractive to cross over Iran in certain situations.

1sources of the ATS Fees: AIP's of the respective states, section GEN 4.2. As high volume users, Emirates may have negotiated better rates.


Why are the lights inside commercial airplanes turned off during take off and landing?

This is for safety reasons.

Take-off and landing are the two most critical phases of flight and thus, every additional step to ensure survivability, be it even just adjusting the light, is taken.

The interior lights or cabin lights are adjusted to match the exterior environment, so that in case of an emergency, especially if the interior lights fail, your eyes are already accustomed to the light setting and you do not require additional valuable seconds for adjustment to a possibly darker or brighter environment. The lights are usually adjusted at dusk, night or dawn to match the exterior environment.1

If the cabin lights do not fail during an emergency, the dimmed light also makes it easier to identify the "EXIT" signs which illuminate and make the guidance lighting on the floor easier to follow. The bright emergency lighting is more prominent to identify when the cabin light is dimmed, saving valuable seconds as the aircraft is evacuated.

This also ties in with having to raise the blinds on the windows. The blinds need to be raised during take-off and landing irrespective of the outside light situation, however, with a darker cabin, any outside light source, especially from fires or other hazards is easier to identify by the crew, making the decision process of whether one side could be inappropriate to use for evacuation faster, e.g. fire on port side --> no evacuation on that side.

The blinds are therefore raised to allow a better view for cabin crew of the outside area and external aircraft parts, such as engines, wings, etc.
See also this related question: Why open up the window shades before takeoff and landing?


How does the aircraft keeps propelling forward when airflow and thrust are not aligned?

Let us assume level flight. Then the forces acting on the aircraft are shown in the following sketch (not necessarily to scale):

The forces are :

the total aerodynamic force $ F_A $, which is split into two components: lift $L$ (perpendicular to direction of motion) and drag $D$ (parallel to direction of motion)
the weight $W$
the thrust $T$, here acting slightly upwards because of the angle of attack $\alpha$

For un-accelerated level flight, the sum of all forces must be zero. This is independent of the coordinate system you use to split the forces. In our example, this is given by these equations:
$$ L + T \sin \alpha = W $$
$$ T \cos \alpha = D $$
At a given angle of attack, these equations will only be true at one particular airspeed. At higher airspeed, the lift would increase resulting in a climb, which then changes the angle of attack. At lower airspeed, the lift would decrease resulting in a descent.


What would happen if the Emergency Locator Transmitter was activated wrongly?

It happens ALL the time. I have been on many airport hunts looking for the airplane with a triggered ELT. You tale a handheld radio and walk through the ramp until you find it.


How common and dangerous are fume events?

The AVHerald article you linked to pretty much as the answer to your question:

How common are they?Nearly 2,000 events a year in the US alone.

  [According] to the Kansas State University Research there have been 5.3 fume events per 24,000 daily flights in the USA or 1955 fume events a year. However, only 6 fume events per year get reported to the FAA.

How dangerous are they?In extreme cases, they can lead to death, but even mild cases diminish flight crew capabilities.


How and why do wake vortices come together to form two tip vortices?

The picture in your question is an oversimplification. Maybe this photo of an MD-11 on a moist day will help to illustrate the point:

I also think you should not call the wake vortices "tip vortices". The tip vortices are an insignificant part of the whole wake system and can be seen in the picture above on both the winglets and the horizontal tail as thin lines of condensation. The wake vortices are the result of the vorticity shed over the wingspan rolling up. With flaps set for landing, the MD-11 has a big change in circulation at the flap tips, so here the shedding is intensified and shows as a thick line of condensation. There is more going on left and right of that thick line, but it is not visible because the gradient of circulation over span is too shallow to cause condensation in the wake (it does over the wing itself, due to the low pressure on the top side).

Maybe it will be best for understanding wake rollup if you watch it happen in a video. It should also help to confirm your theory :-). A good one is at 3:20 and again at 5:40. Also, watch how the wake changes when ground effect kicks in at around 4:00.


Is it legal for a non-IFR rated pilot to fly a SID on a VFR flight?

It depends what you mean by 'flying a SID'. If it is just following the procedure without violation of VFR (i. e. you are above VFR weather minimums for a given airspace, you maintain your own separation from traffic, don't violate ATC clearances, don't enter controlled airspace without a clearance etc.) - yes, it's perfectly legal. You can fly any route you want, your choice (again, I assume that you do not violate ATC clearances).

If you mean by 'flying a SID' obtaining an ATC clearance to fly a SID - if it is an IFR clearance, than no, it is illegal. You cannot request IFR clearance if you or your aircraft is not IFR rated, except the cases when you are training for an IFR (and have a CFII next to you).


Can the cockpit windows on commercial airliners open during flight?

I'm sure that the cabin pressure difference prevents this at altitude when the cabin is pressurized, due that they often slide inwards and then to the side.

That being said, Boeing produced a video showing that it's no problem flying with an open window on the 737 if say it opens on takeoff. You can close it assuming it's not damaged or you can land with it. They also showed that the side window can be opened in flight in case for instance visibility is impaired through the main window, and while it hardly looks comfortable, it can be done. This assumes that the cabin is unpressurized.

The sort of thing you might be thinking about is a cooper vane, but I don't think any aircraft have those on the cockpit windows.


Does an airfoil in potential flow produce drag?

Short answer: D'Alembert's paradox always holds as stated:

  For incompressible and inviscid potential flow, the drag force is zero on a body moving with constant velocity relative to the fluid.

Longer answer: Pressure drag is a viscous phenomenon. Anderson section 3.18 has an extended discussion of experimental results stating that

  the real flow over a circular cylinder is dominated by friction effects, namely, the separation of the flow over the rearward face of the cylinder. In turn, a finite pressure drag is created on the cylinder, and d’Alembert’s paradox is resolved.

Anderson 3.15 and any number of online resources convincingly and rigorously prove that inviscid flow around a cylinder preserves d’Alembert’s paradox (even when the cylinder is spinning and producing lift) because there will always be cancellation of aerodynamic forces due to the symmetry of the flow field across the line concurrent with the lift vector. The easiest way to convince yourself that this is also true for airfoils is the conformal mapping technique explained in this answer.


Does the Airbus A320 or Boeing 737 have better resolution screens in the cockpit?

B737NG DUs (Display Unit) have a resolution of 1152x1152, as per the maintenance manual. The display size is 18x18cm, making it around 163 PPI.

I have found a source that claims A320 PFD has a resolution of 768x768 and the display size is 158mmx158mm, making it around 123.4 PPI.

I imagine B737 MAX is using the same 15.1" display as the B787. In this case, the resolution is 1400x1050, and the PPI would be around 116 PPI.


Why is the weather radar mounted on the left wing of the TBM?

After some detective work I have concluded:

In the TBM planes, the center portion of the right wing leading edge is occupied by the stall warning vane (or an optional AOA sensor in newer models). The two pitot tubes are located under each wing and landing lights are positioned at wingtips. This would leave the current location for the optional weather radar pretty much the only option available.

TBM 700C pilot information manual, stall warning vane description on page 7.15.1

Source for picture


Throughout aviation history, what airships were metal clad?

At least two all-metal airships are known to have existed, the first one invented by David Schwarz, and test-flown in Tempelhof, in 1897. It flew, but crashed when landing.

Another one, a really successful and better known aircraft, was an American airship, the ZMC-2, that first flew in 1929.

https://en.wikipedia.org/wiki/David_Schwarz_(aviation_inventor)

https://en.wikipedia.org/wiki/ZMC-2


What is a biplane propeller and how efficient is it?

It is essentially two propellers stack on top of each other. You can see it in this picture of a Lazair.

As for why they were chosen for the Lazair,

  Many have asked why Ultraflight opted for double propellers stacked in
  a biplane fashion. This is a very unique setup and draws lots of
  attention. Apparently when Ultraflight changed over to the Rotax 185
  they tried several different propellers. The problem was the 185’s had
  a woodruff key slot in the crankshaft and would snap the crank
  whenever the engine coughed or kicked back on start up. This was quite
  a serious problem. After much deliberation it was determined that the
  rotational inertia of the propellers was too much for the crank to
  handle.

  Dale could not locate a two bladed prop light enough to fit the need.
  However, since they had been producing a lot of the early lazairs with
  Pioneer engines fitted with a single plastic prop, he had a ton left
  over that fit the pioneers.  He found that these could be “doubled up”
  and help to produce the extra thrust that the Rotax 185 was capable of
  producing over the 5.5 hp Pioneer engines.

It appears to be a quick way to gain more thrust from the props without increasing prop mass too much.


What would happen if you turn on all air vents simultaneously?

@Casey is correct. Nothing will happen under normal operating conditions. The FAR §25.831 Ventilation requires,

  ... the ventilation system must be designed to provide each occupant with an airflow containing at least 0.55 pounds of fresh air per minute.

In general, the amount of air available is far greater than the requirement. On the ground, compressed air for the Environmental Control System, which supplies air to crew and passengers can be obtained from an APU, a GCU, airport high-pressure hydrants, or the aircraft engines. In flight, however, compressed air is obtained almost exclusively from the compressor stages of the aircraft engines.

The pressure would not be affected by this. According to FAR §25.843, Tests for pressurized cabins, the pressurized cabins are tested to show the performance of

  ... the pressure supply, pressure and flow regulators, indicators, and warning signals, in steady and stepped climbs and descents at rates corresponding to the maximum attainable within the operating limitations of the airplane, up to the maximum altitude for which certification is requested.

Note that in some aircraft the air conditioning system is switched off during climb- this is to do with the load on engine and not the air supply.


How can a pilot fly a distance of 594 NM connecting two VOR's?

You are correct that VOR's rarely have a range of more than 200 NM. However, Alta Floresta VOR (ATF) is colocated with an NDB (and DME). In spite of less accuracy, NDB's have a much greater range (partly because their signals can travel as ground waves). This makes it possible to have a very long segment on the G678 airway without other navigation aids. When leaving the coverage of Brasília VOR/DME (BSI), you should be able to pick up ATF NDB.


How do I choose the vertical tail's airfoil?

Normally, you would pick a symmetric airfoil. The thickness should be between 9% and 15% to find a good compromise between structural efficiency and maximum side force. Choose a thicker airfoil at the root, a thinner one at the tip and interpolate linearly between them.
Of course, for supersonic designs a thinner airfoil should be selected.
In some special cases a cambered vertical helped to improve flight characteristics, but this concerned mainly very powerful, single-engine propeller airplanes. I would expect your UAV is outside of this category.
Depending on the Reynolds number range of this vertical, a member of the Wortmann FX71-L series might be a good choice.


Is it legal to fly without a transponder?

Yes, you can in the US in Class D, E & G airspace according to 14 CFR 91.215. You will need to placard the transponder INOP, and make a note in the aircraft logbook. But, you must stay out of any Mode C Veils, and further than 30 miles from Class B airports. Also, stay below 10,000 feet MSL unless that means you are below 2,500 feet AGL. However, you can request a deviation to 91.215 from ATC in advance.


Has there been research into alternatives for the vertical stabilizer?

There have been various (and of varying degrees of success) some flying wing designs that have made it into production with no vertical stabilizer. However they had no turnable horizontal stabilizer either. The B-2 Spirit comes to mind,

(source)

The closest thing I can think of that has no proper vertical stabilizer but still does have an epenage is a V tail design, a variety of planes have been made with them over the years including the popular early Beech Bonanza models.

(source)

I am not sure of any planes that have ever been produced with such a tail nor any research projects on such a design but that does not preclude their existence.

A general note on aircraft research and design, the various flying wings and V tail planes built over the years have had issues and been met with hostility by some critics. This is not to imply that they are poor designs however the flying wing does have its share of instability inherent to the design. The V tail gained some negative reputation on the early Bo's because many of them crashed. However many people account this to low time pilots in overpowered (for the time) planes.


Is it possible to fly a B-24 under Bixby Bridge?

A Liberator has  wingspan of 34m, while the central span of the bridge is 110m wide, and 280ft high, so the aircraft will fit under the bridge.

Bixby creek approaches the bridge from the north-east, with a straight-ish approach of about 0.3miles. Approaching low from the north-east, and dropping down into the creek at the earliest opportunity might allow even a Liberator enough time to descend below the level of the bridge deck and recover over open sea, although the waves might be a little too close for comfort.

I wouldnt want to attempt it in a fully-laden B-24, but with a light fuel load and crew I'd say it's doable. Whether anyone ever did it is another story...


Where does upward momentum come from in leading edge vortex?

Does this vortex draw in air from above, pulling it downward and as a
  result lifting the plane up?

Yes, the bound vortex in combination with translational flow accelerates air downwards.

  Or is the vortex shed downward off the tail of the wing? How does this work?

A vortex has no beginning and no end. When the wing begins to move, the vortex starts out of nowhere and has four parts: The bound vortex which travels with the wing, one parallel starting vortex which stays in place and two free vortices which connect both, running from the wingtips to the point where the wingtips were when the wing started moving. To be precise, an infinite number of vortices of infinitely small strength is created, and some cover only the center of the wing while others run over most of the wingspan.

Idealized vortex structure (own work). The wing moves to the left with the speed v. The vortices are shown as discrete lines - to be precise, the bound vortices should be a sheet of infinitesimally small vortices which extend both over the chord and the span of the wing. Chordwise, they bunch together close to the leading edge, so their average streamwise position is at one quarter of the wing's chord.

And now let me give you my advice: If you do not want to operate or to write a potential flow code, do yourself a favor and forget all that. Read here why you must endure the vortex explanation of lift, and read here for a much more intuitive explanation of it all.

If by leading edge vortex you mean the swirling air coming off the leading edge of a highly swept wing, this is a result of flow separation. The inertia of the air molecules makes it impossible for them to flow around the leading edge, and they jump off the contour, leaving a volume of lower pressure behind. This pressure bends their flow path towards the wing and sucks the aircraft upwards. Since more air follows the same pattern downstream, the whole air above the wing starts to rotate while it flows downstream. This low pressure area sucks more air in from above, just like the regular low pressure region over a straight wing does.

Along and past the inner part of the wing this downward motion is prevalent and keeps the air spinning like the regular downwash from a straight wing.


Does weight affect the fuel burn calculations in a light GA airplane?

The engine doesn't care how heavy the airplane is (or how well it is flying), but you might.

As long as you are cruising around at a particular altitude and power setting, then the engine is going to consume fuel at the same rate.  A heavier airplane will require increased lift, which will induce greater drag, and will have a lower forward airspeed as a result of that same power (assuming it is not so heavy that it prevents you from maintaining altitude).

If on the other hand you have a particular airspeed you want to maintain, then the power needed for that speed will depend on weight.  Lower weight, less power necessary, less fuel flow required to supply the power.


Maximum Flaps extended speed Vfe for full or partial flaps?

Unless a different speed is explicitly noted for partial flap extension, Vfe pertains to extending the flaps any amount. (For example, the C-172RG has a Vfe of 130 KIAS to 10º flaps, 100 KIAS beyond 10º flaps. Not so for the PA28s.)


What steps do I need to follow to use my PPL for income?

This depends on your jurisdiction a bit since the nuances vary from country to country but in general to get paid to fly (or get paid enough to break even) you need to have at least a commercial pilots license. This would allow you to get paid to fly. With a CPL you can do lots of things like:

Tow banners
Fly charters
Fly cargo
Fly sight seeing flights
Tow gliders (can be done for compensation with a PPL and proper endorsements as well see Rons comment)

What many pilots go on to do if they are only looking for weekend break even fun, is to get their Certified Flight Instructor ticket and teach others to fly. This is a nice way to make some money, fly some beat up planes, and pass along the hobby to others.

The speed to any licenses is hard to predict. It varies based on your time, money and aircraft availability as well as how good of a study you are. You also need to accumulate the hours required for a CPL which can take time. With good weather and a consistently working and free plane you can get through it in months. If you are a weekend warrior and only have access to busy rental planes and live in an area with weather it can take a few years to get everything done.


Wikipedia:

  The B-1 [variant] was also fitted with "Jericho trumpets", essentially propeller-driven sirens with a diameter of 0.7 m (2.3 ft) mounted on the wing's leading edge directly forward of the landing gear, or on the front edge of the fixed main gear fairing. This was used to weaken enemy morale and enhance the intimidation of dive-bombing. After the enemy became used to it, however, they were withdrawn. The devices caused a loss of some 20–25 km/h (10-20 mph) through drag. Instead, some bombs were fitted with whistles on the fin to produce the noise after release.

So, yes, it was purely psychological and actually hindered the pilot by reducing air speed in ordinary flight and they were removed when they stopped having the psychological effect.


Light Plane: Transition to Right-Seat Flying: How to Prepare, What are Common Errors?

First, congratulations!  Earning a CFI certificate is a real undertaking.

For a literal textbook answer to your question I suggest opening this PTS pdf (assuming FAA CFI) and searching for "common errors" until you find yourself in relevant (to you) sections.  There are many examples.

On a personal note, I found that talking through every action made maneuvers go smoothly and let the instructor/examiner know that what I was doing is intentional.  It also forced me to follow my own directions so, since I knew what was supposed to happen, I just said it aloud and then did it.  It sounds silly but it worked well.

The transition to right seat flying is simple.  You'll have it down in an hour or two.  Nothing to it.  It's actually kind of anticlimactic.  Which plane are you using?


Why do some non-towered airports have class E airspace from the surface up?

This answer is specific to the United States (heck, I don't know if this is an even an issue elsewhere in the world).

The airspace classification actually has nothing to do with whether or not a particular airport has a precision approach. It is based on two factors: communications capability and weather observations.

For a non-towered airport to have Class E (surface) airspace, ATC must have communications capability with aircraft down to the runway surface. Second, weather observations must be provided by a Federally certificated observer and/or Federally commissioned weather observing system. Reference: FAA JO 7400.2K, paragraphs 18-1-1 and 18-1-2.

If one (or both) of these conditions are not satisfied, the surface airspace will be class G with a class E floor of 700 ft. AGL if there is an instrument approach into the airport and 1200 ft. AGL if not.

Now, here's a twist: if the airport has a part-time control tower, the airspace may become Class G when the tower is closed, even if both communication and weather reporting requirements are satisfied. Be sure to check the Chart Supplement (fka A/FD).


What is the cable connected to a plane for?

This is a ground power unit (GPU) which supplies the aircraft with electricity while the generators or the auxiliary power unit (APU) are not running. This is important especially during boarding, when the cabin lighting needs to remain on for passengers to embark or disembark. The GPU is also used to start the APU, which in turn provides electricity to start the engines and the generators.

  A ground power unit (GPU) is a vehicle capable of supplying power to aircraft parked on the ground. Ground power units may also be built into the jetway, making it even easier to supply electrical power to aircraft. Many aircraft require 28 V of direct current and 115 V 400 Hz of alternating current. The electric energy is carried from a generator to a connection on the aircraft via 3 phase 4-wire insulated cable capable of handling 261 amps (90 kVA). These connectors are standard for all aircraft, as defined in ISO 6858.
  Source: Wikipedia

Related Questions:

Can large airliners be operated without ground support?

How are turbine engines started?


FAA/NACO charts aren't masters, either

The master form of a FAA instrument approach procedure isn't the FAA/NACO approach plate for that procedure -- that plate is a derived document, just like the Jeppesen plate for that approach is.

The master, instead, is kept by the FAA in textual form as a set of Form 8260s. These provide a precise, formulaic description of any FAA approach procedure -- they're simply not in a form that's at all usable in the cockpit.

An example set of 8260s for the (rather special) KASE LOC/DME 15 approach can be found here.  Note that this contains exact records of fixes, governing obstacles, holds, and other procedure parts, as well as documentation about standards waivers and notes of changes.


Can manoeuvres like overbanking and high G braking be used in a single propeller aircraft?

Can you explain how it works and how to use it and what is the advantage compared with regular steep turns?

He needs to turn and start to descent. Note, that the two moments he's overbanking he's flying over ridges and wants to descent to the valley behind.

Now when you want to lower the nose in a turn you need to bank more so you still have the desired lateral lift, but less vertical.

But he's so fast that he needs negative vertical lift component, and since the wings are producing positive lift to make the turn, he needs to bank more than 90° to get it.

  I have CPL but I was never thought such maneuvering. Can it be used in SEP aircraft or glider with just a couple of G?

It is a positive G manoeuvre and you can do the same with, say, 2G, so technically yes. However:

You have no use for it. He's flying 420–480 knots. At 420 knots, a 1G (meaning 1G lateral, so 1.41G total at 45° bank) turn will have rate 2.6°/s and radius 4759 m. But in a SEP you might be flying, say, 120 knots and then 1G turn will have rate 9.1°/s and radius 388 m. That, of course, applies to vertical turns as well. So where he needs to push -1G, and thus overbank, you would do with reducing to, say, 0.5G, and thus still normal side up.
You would probably loose spatial awareness rather quickly if you are not trained in aerobatics. The fighter pilots train a lot to be able to handle the plane at these high Gs and unusual attitudes. Without training, it will get confusing pretty quickly.
Your attitude indicator will likely tumble. The fighters have attitude indicators carefully designed not to, but your average mechanical one in something like C172 almost surely will. That is not a problem in itself—aerobatic pilots just cage it and fly purely on external references—but you need to be aware of it.
The fighter has a G-meter, but in a typical SEP plane you don't. But if you fly below $V_A$, the wing will stall before exceeding the structural limit, so you can do without.

During aerobatics, such, or similar manoeuvres may be performed. For example in Red Bull Air Race turns are usually executed at 90° bank (to use all the lift for the change of direction). The plane climbs a bit to store some speed in height, since turns are tighter at slower speed, then makes the hard turn, during which it has 0G vertical and the vertical speed decays and it changes from climb to descent and then it levels from the descent in the gate height and with all its speed back.

  At the end of the movie looks like 5G is used for slowing airplane for landing. 5G is pulled and jet instantly slows from 300 to 260.

The induced drag is proportional to coefficient of lift. So when the wings are requested to generate a lot of lift, they also generate a lot of drag. Especially since this might have been enough to pull the delta wings of the Typhoon to the vortex lift regime, where it generates even more drag.

I believe part of the reason to fly such sharp turn here is to fly the pattern at modest size despite the high speed and the deceleration is just a nice side-effect. The speed brake would be enough to slow down, and still needs to be used as 260 knots is still about twice the landing speed.


What are stick position stability and stick force stability?

Stick position stability.

In its broadest definition, stick position stability means: a larger aft stick deflection is required to maintain a lower constant airspeed. Or in an equation: $d\delta_e/dV > 0$, with $\delta_e$ being the elevator deflection, + = Trailing Edge Up

An aeroplane with stick position stability is easy and safe to control. If the pilot wishes to fly at a lower velocity, they only need to deflect the stick further aft in order to reach the larger Angle of Attack required to maintain lift. An aeroplane with stick position instability will react with an ever increasing nose-up deflection, requiring corrective opposite stick action.

Stick force stability.

An aircraft has stick force stability if deflecting the stick further away from trimmed position, requires a larger force: the stick feels as if it is loaded by a spring. Easy to achieve with irreversible flight controls, which are loaded by a mechanical spring. More difficult with reversible flight controls, where the airforces are directly fed back to the stick: at lower airspeeds the force gradient must be high enough to result in clear stick trim conditions (friction in the control loop plays a role here), at higher airspeeds the aircraft must still be controllable.

Stick position stability is a necessary condition for stick force stability, and stick force stability is an additional requirement for safe and easy control. And it is this stick force stability in a turn that required the implementation of MCAS in the B737MAX: stick force stability must be demonstrated in all flight states in order to obtain certification.


Is (or was) it acceptable to throttle up for takeoff before being aligned with the runway center line?

Pilots in any size aircraft may sometimes be given an instruction from ATC such as "... Cleared for immediate takeoff ..." which means that the pilot is expected to execute the takeoff as quickly as he/she can safely do so.  That may involve applying noticeably more power than normal for the roll from the taxiway out to turn and line up with the centerline of the runway, to keep the speed up and get off the ground as soon as possible.  For example, there may have been an aircraft on final approach for the same runway and the air traffic controller wanted to be sure to maintain ample separation from the departing aircraft.  So unless you were in the cockpit hearing the radio communications and seeing what the pilot may have seen in the approach corridor, it's difficult to say for sure whether the pilot was hot-dogging or was just wasting no time getting out of the way of arriving traffic as soon as he could.

But on the other hand ... announcing to passengers "Nos vamos" while hitting the throttle in the taxi turn out to the runway centerline ... at best, that doesn't exactly sound like what a cautious and conscientious airline pilot would choose to be doing in that moment!

With two pilots in the cockpit it is not unusual for one to do the radio communications while the other manipulates the controls to fly the airplane.  Those words could have been quite fine for one pilot to say to another in the cockpit intercom as emphasis.  Maybe the pilot only meant to do that but mistakenly transmitted it to the passenger cabin instead; in which case that would have been an unfortunate and unsettling error although not an especially dangerous one.

Although I haven't done such a report myself (because thankfully I don't recall being involved in such an incident), if you observe an airline pilot doing something you consider very dangerous or inappropriate I'm pretty sure the airline would want to hear directly from you about it with details such as flight number, date and time of the incident, so they can investigate.  We can each do our part to keep flying safe!


Is there a global map of aviation waypoints?

I think what you are searching for is SkyVector

Its a web-map where you can see waypoints, NDBS, DMES, FREQUENCIES, ETC


What is the bag for on a passenger oxygen mask?

Oxygen in passenger masks is either generated by oxygen generator or released from pressurized container via reduction valve. In either case it is released at fixed rate. But human breath is discontinous. So the bag acts as a buffer. You inhale the oxygen accumulated in it and then it slowly refills while you are exhaling.


If you file a flightplan with "NO SID", can you still get assigned a graphical ODP in your clearance?

ATC can indeed include an ODP in a clearance; this is from the ATC orders section 4-3-2:

  Where an obstacle departure procedure (ODP) has been published for a
  location and pilot compliance is necessary to ensure separation,
  include the procedure as part of the ATC clearance.

  EXAMPLE−
  “Depart via the (airport name)(runway number) departure procedure.”
   Or
  “Depart via the (graphic ODP name) obstacle departure
  procedure.”

The "NO SID" note is exactly what it says, i.e. it applies to SIDs only. This is from the orders 4-3-3:

  If a pilot does not wish to accept an ATC clearance to fly a SID,
  he/she is expected to advise ATC or state “NO SID” in his/her flight
  plan remarks.

Note that SIDs and ODPs exist for slightly different reasons: SIDs are primarily to simplify communication and automation; ODPs are specifically designed to help ensure obstacle clearance and you can fly one without an ATC clearance (unless ATC assigned some other departure procedure). That means it's usually in your interest to fly an ODP if possible.

Having said all that, a pilot can always decline some or all of a clearance that he isn't capable of flying or is just uncomfortable with. But if you reject both SIDs and ODPs, then ATC has to vector you and that could easily cause delays, especially at a busy airport.


Why do turbine engines take so long to spool up?

I'm not an engineer (which might be better suited to answer this) so this is from simplified things they feed pilots:

Jet engines take much longer to spool up (i.e. increase RPM) than piston engines, especially at low RPM because of the pressure ratio/increased airflow necessary to keep the compressor from stalling/surging/blowing up every time when changing power settings.

The (simplified) jet engine cycle contains a compressor that pushes air into a combustion chamber, where it burns, and then blows out the rear end rotating a turbine that moves the compressor from back where we started at.

If you "add more power" (i.e. put more fuel in) it takes a while for that extra fuel to produce more thrust, which in turn takes a while to accelerate the turbine, which will make the compressor spin faster, which will finally bring more compressed air into the combustion chamber to utilize all that extra fuel you poured in at step 1.

Adding power all of a sudden will increase the pressure in the combustion chamber, so much that air that is "upstream" (i.e still in the compressor) does not want to advance. The extra pressure in the combustion chamber did not have enough time to spool up the turbine, so now the compressor is underpowered to keep "pushing" compressed air into the combustion chamber. Air starts flowing backwards (i.e. from combustion chamber to compressor), engine surges, all hell breaks loose.

So there is a lag (electronically these days, the pilots can floor the trust levers as fast as they like) when the engines are at low RPM, the FADEC only adds a little bit of extra fuel, waits for the airflow to stabilize, then adds a little more, and so on.

I think the graph below might explain this. Every time you change RPM, you will increase Pressure Ratio (i.e. move up the graph), then you wait a little bit for Air Mass Flow to increase (i.e. move right). If you increase the Pressure Ratio too much, without the accompanying mass flow (which take a while because of inertia) you will enter the surge line.

A similar thing happens on spool down, albeit a gentler one.

Compare this with the piston engine where you put more air/gas mixture into the cylinder, it makes for a bigger bang, accelerates the piston faster, and the very next piston cycle you can theoretically get max power.


How to correctly interpret the taxi procedures in ICAO Doc 4444?

Below are my answers to your specific numbered questions.

I believe there are 4 variations of taxi clearance you might expect to receive in your scenario:

a.  Taxi to RW 09

b.  Taxi to RW 09, hold short RW 30

c.  Taxi to RW 30

d.  Taxi to RW 30, hold short RW 09
This is incorrect.  You will never receive taxi clearance to an undefined “holding point”.
Basically correct, but there are no traffic lights or stop bars on any taxiways I have ever seen.

Regarding #1, those are the four possible combinations of a basic clearance, i.e. you are either allowed to cross the off-duty runway or you are not, and there are but two runways.  However, that doesn't mean that you might not hear variations to this.  While pilots and controllers strive for standardization there is some variety.  For example, while not required to do so, it isn't unheard of for a controller to say "taxi to RW 09, cleared to cross RW 30."

To provide some additional context, clearance to taxi to an active runway clears the pilot to cross any off-duty runways that may intersect the taxiway.  If the pilot is cleared to taxi but told to hold short of an intersecting runway, further clearance to cross and continue taxiing will be made on the radio.

The actual words “holding point” (in my experience) are never used.  Clearance to taxi to a runway presumes the pilot will taxi right up to the painted hold-short line and stop there before switching frequencies and requesting takeoff clearance from the tower controller.  The tower controller will then clear the pilot to either take off, line up and wait, or continue holding short.

At most airfields serving general aviation aircraft there is widened section of the taxiway in the hold short area for performing engine run-ups and final takeoff checks.  However, the ground controller will never clear you to this “holding point”, but will instead clear you to the runway in use.  It is up to the pilot to use this area as needed, and then taxi up to the hold short and switch to tower frequency when ready for take off.


Is the Reynolds number the same for both the airfoil and wing? If not, why/how does it change?

From the equation that defines it, you can see that its value depends on some properties of the fluid (air), the speed that an object moves through the fluid, and the length of the object.  Nothing else.

For an airplane wing, the length, aka "characteristic linear dimension," is conventionally chosen to be the chord of the wing.  The wingspan doesn't affect the Reynolds number.  Neither does the choice of airfoil.

In other words, given an airfoil (say, a segment in a wind tunnel at a particular chord, airspeed, and air density), and given a wing on an airplane built from the same airfoil with a different chord, airspeed, and air density, the Reynolds numbers for these two situations are likely to be different.


Which international routes might save fuel and time by using a potential newly "deemed safe" North Korean air space?

I think the biggest one would be Tokyo - Beijing, and more broadly, anything in Japan north of Osaka to Beijing.

The current airway turns does a dogleg up to right above Incheon airport, (you can literally see the airport and Seoul).

You can play with http://www.gcmap.com to see great circle maps, which are a good approximation of the most efficient route.


What are mechanical requirements for flying over water?

Private operations - no requirements. Single-engine is legal, you can argue as to the safety.

Commercial operations...
Single-engine: within gliding distance of the land.
Twin-engines: always within 60 minutes of the land... unless specially approved airplane and operator, and airplane maintained according to much higher specs - this is ETOPS.
More-than-two engines: no problem.


Does international mail go in passenger planes?

So I'm assuming mail does not go in civilian aircraft.

Like many thing in aviation it depends. For shipping it will depend on where you are shipping to and from, how big the item is and the chose method of shipment. Both FedEx and UPS (who are private shipping carriers) operate large fleets of cargo airplanes. In many cases a shipment may end up on one of their own cargo planes. However their planes, like passenger planes run routes that may be pre-decided. As such passenger airlines sell the leftover cargo space to anyone willing to buy it. You can find a nice blog post on how it works here. UPS/FedEx may pre-broker a deal to buy a certain amount of cargo space per year from an airline to obtain a better rate or they may buy it on demand as needed.

Now Air Mail is a bit different as its offered (here in the US) by the government postal service. Technically the USPS no longer offer airmail service as it was once called but does still offer domestic and foreign guaranteed time shipping. All of these items are moved in cargo space on Commercial Passenger Planes or by under contract by FedEx as the USPS no longer operates any aircraft.

  Am I right, and if so, what's the reason for that? It seems it would
  be extremely more efficient at least for small shipments.

Like most things in aviation low cost will always beat out marginal efficiency. If FedEx can ship a package at a significantly reduced rate but in turn it will take an extra day or two to arrive than many customers will see a value add in that. In the same vein it would be very efficient to fly every passenger in a small plane to an airport closer to their final destination and have the plane depart when the passenger needs to, however the cost of that simply would never work out.


How should I attach an aircraft model in a wind tunnel when testing wind gust/yaw stability?

In order to measure yaw derivatives, the airplane has to yaw when in the tunnel. If you mount it at the center of gravity, which should be reasonably close to the geometric center, it will stay in the center of the tunnel section.
In the old times, windtunnel models were mounted on strings. I expect that your model sits on a long sting. This sting sits on a rotating scale which rotates such that the mounting point does not move around when the scale is rotated. Alternatively, the scale is inside the model (see picture below). If your arrangement is different, please point this out in an edit of the question!

Internal force balance and sting (picture source)


Feasibility of converting long body carriers into stationary field hospitals

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

The pros of this concept would be:

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

The cons of this concept would be:

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


How do airlines pay for aviation fuel and services at an airport they don't normally use?

In the United States most places take credit cards.

Large carriers generally get billed, or for smaller airports they use a company credit card. There are even specialized credit cards that are designed specifically for this use.

There is also what is called "contract fuel". Basically there is a company that is a middleman, a fuel supplier who pays the airport fuel company and then rebills the airline. The pilot has a card that identifies them as a client of the fuel contractor.

For example, check out AEG Fuels, a typical fuel contractor. (Please click on that link. I get 25 cents every time you do. Just kidding.)


What does the "T" on sectional charts mean in reference to airspace altitude?

T is used to signify that the top of Class C airspace that lies under Class B is the bottom surface of that airspace. This is important when the Class C segment lies under multiple layers of Class B, where no single top altitude applies.


How can I plan a VFR flight through controlled airspace, without knowing what instructions ATC will give me?

Short answer: make your flight plan as usual but if something changes then just deal with it. After all, as a private (?) pilot you've been trained to handle that situation.

Even an IFR flight plan is only 'plan A' and on any flight you may have to deal with changes because of ATC, weather or other issues. That's one reason why the private ACS includes a diversion task to test whether you can re-plan in the air. Note the wording of that task (emphasis mine):

  Make a reasonable estimate of heading, groundspeed, arrival time, and fuel consumption to the divert airport.

It's helpful to think about general options in advance (e.g. "I'll go west around the KPHL class B if I don't get a clearance"), but you can't predict every possible situation. Always having that "reasonable estimate" for where you're going is more important than trying to anticipate and plan for every eventuality.

The good news is that as part of your original flight planning you should already have reviewed all the information you need to make decisions in the air: winds aloft, fronts, airspace, TFRs etc. So if you do have to re-plan you already have a good overview of the big picture and what your options are. "Plans are useless, but planning is essential", as someone once said.

And if you don't already have a flight app like Foreflight or Garmin Pilot then you should look into it. They make planning, diversions and replanning much simpler, which removes a lot of stress from the situation. They're also much easier to work with than paper and pencil, especially if you're single-pilot without an autopilot.

Finally, don't forget the magic word "unable". ATC can't see what you see, and they might drop you in an awkward situation, e.g. you're VFR between cloud layers and the only way to stay in VMC is to enter class B. If that happens, don't hesitate to tell them that you need a clearance, or vectors, or whatever. If they don't cooperate, you can always declare an emergency if the situation is becoming unsafe (but don't abuse the system for your own convenience).


Where can I find info or techniques on calculating the influence of a duct on the thrust and efficiency of a propeller?

There is info on power computations for ducted propellers in J. Gordon Leishman, Principles of Helicopter Aerodynamics. The beneficial contribution of the duct can be found in section 6.10.1 Fan-in-fin Design, and in section 3.3.10 Prandtl's Tip-Loss Function. In short:

If the duct is designed to prevent wake contraction, extra thrust is generated and less power is required to drive the propeller. The effects are computed with momentum theory, which is a simplification. For thrust T and power P, with $T_D$ and $P_D$ = ducted, $T_U$ and $P_U$ = unducted, $a_w$ = ratio of outlet/propeller area.:

$$\frac{T_D}{T_U} = \frac{1}{2a_w} \tag{1}$$
$$\frac{P_D}{P_U} = \frac{1}{\sqrt{2a_w}} \tag{2}$$

Tip loss. The duct prevents circulation loss at the tip if the clearance between tip and duct is small enough. Prandtl has been working on this in 1919 using momentum theory, an example for an untwisted blade is depicted below.

There is also this masters thesis, with measurements of small ducted rotors with low tip speeds.


Difference between general, airframe and power plant concentration courses

The US Mechanic certification has two components, Airframe and Powerplant. The license is generally known as an "A&P" license because most candidates choose both. There are, however, three exams. The third is the General knowledge exam. You have three choices for licensing:

Airframe only
Powerplant only
Airframe & Powerplant

For all three options, you must take the General exam as well. Taking a general course will only prepare you for that exam, which does not lead to any license or certification.


Do seaplanes need to get clearance for takeoff?

If the seaplane is operating from a land airport with a control tower AND a water runway, yes.  Or, if the seaplane is operating from a Tower controlled  water-only aerodrome, such as the one along the waterfront in Vancouver BC in Canada, yes also.  Same radio procedures as any other airplane.

Otherwise, no.


Does the Predator drone's design make a tail strike more likely on takeoff and landing?

The tail arrangement was initially chosen to protect the propeller from touching the ground first. The configuration of what later became the Predator was initially designed to be launched from a submarine, so it needed to fit into a torpedo tube when folded. When this configuration was scaled up, the general arrangement was kept. Now the tail surfaces are much larger relative to the propeller, so the initial reason for their location is not easily discernible.

The high aspect ratio $AR$ of the Predator's unswept wing gives it a much higher lift curve slope than that of the swept wing of an airliner, so less rotation is needed to increase lift for take-off. Also, the highly cambered airfoil has a very low, negative zero-lift angle of attack, so at level attitude the wing already produces substantial lift. This was chosen to fly at optimum endurance speed with a horizontal fuselage attitude. The lift coefficient $c_L$ for optimum endurance is $$c_L = \sqrt{3\cdot\pi\cdot AR\cdot\epsilon\cdot c_{D0}}$$
At that lift coefficient, induced drag $c_{Di} = \frac{c_L^2}{\pi\cdot AR\cdot\epsilon}$ is three times bigger than zero-lift drag $c_{D0}$, which means endurance is longest when the aircraft flies at a high lift coefficient and low speed. Basically, the Predator is a point design, flying almost always at the same attitude and lift coefficient. Ground attitude equals flight attitude, and a rotation beyond a few degrees will make it stall.


Are Final Tests always required for LRUs?

I'm assuming by Pre-Testing procedure you are referring to a physical inspection and downloading the fault history.

If there are no logged faults in the fault history, it means that the built-in test (BIT) of the LRU did not detect any faults. BIT is not capable of 100% test coverage. It is also possible that BIT results are inaccurate. A lack of recorded faults is not sufficient to declare a unit airworthy.

Once an LRU is tagged and sent to the service center/shop, it can only be returned to service (RTS) after it has passed the RTS tests specified in the component maintenance manual. After passing the RTS tests, a 'maintenance release document' can be prepared and the unit returned to the spares pool.

In the US, the maintenance release document may be an FAA Form 8130-3, Form 337, or other document containing the information required by 14 CFR Part 43, sections 43.9 and 43.11. The maintenance release document must be signed by an authorized person who is certificated under 14 CFR Part 65. Though not legally required many shops will affix a "yellow tag" to the unit to indicate it's serviceable status.

EASA has similar rules, the primary difference being the required content of the documentation.


Where to download NATs (North Atlantic Tracks) information?

Your question

  I cannot find information from [Shanwick Oceanic Control and Gander
  Oceanic Control] What are their websites?

Direct answer

ATC centers have no public websites in general. Aeronautical information is distributed by a fixed dedicated network, the aeronautical fixed service (AFS) and its data network AFTN.

From ICAO North Atlantic Operations and Airspace Manual (NAT Doc 007):

  The agreed OTS is promulgated by means of the NAT Track Message
  via the AFTN to all interested addressees. A typical time of
  publication of the day-time OTS is 2200 UTC and of the night-time OTS
  is 1400 UTC.

FAA, other agencies and aviation blogs relay the NAT-OTS notam on the web.

You can read below if you are interested in jet streams and how the track system is rebuilt twice a day to take advantage of current winds.

Polar jet stream

The jet streams are extremely strong west winds blowing at cruise (tropopause) altitude. The polar jet streams blow at about 50/60° latitude, and the northern polar jet stream is the one blowing over the North Atlantic ocean, the busy route between North America and Europe.

According to the theory, still in discussion, the prevalent wind in altitude in this area is due to the interaction between interleaved Ferrel cells (high pressure) and polar cells (low pressure):

Atmospheric circulation (source)

(Note the tropopause is lower at the pole than at the equator.)

This results in a wind blowing from a south cell to the closest north cell, speed is often between 50 and 150 kt, but 200 kt has been seen. However, for an observer on the ground, due to Earth rotation (Coriolis force) the flow is meandering eastwards from Canada to northern Europe at an altitude of about 8-10 km, as visible on this image of today's polar jet at 250 hPa isobar:

Source: NullSchool

Colored curves are isotachs, areas of equal air speed. Blue is 0 and purple is more than 200 km/h.

The thickness of the polar jet streams is usually less than 5 km and their width a few hundreds of km. To take advantage of jet streams when flying to Europe, aircraft must be packed into this area.

Daily updated organized track system

Aircraft fuel consumption and ground speed can be significantly improved by using tailwinds when flying eastwards, and minimizing headwinds when flying westwards, rather than just following the shortest path (great circle) between two locations. The North Atlantic Organized Track System (NAT-OTS) is a set of eastbound and westbound routes over North Atlantic, computed twice a day to this effect.

Tracks to North America are named starting at letter A, tracks to Europe are named starting at letter Z. Routes for Europe are in the middle of the polar jet, routes to North America are the northernmost, where the jet is the weakest.

Today's polar jet stream and corresponding NAT-OTS (look at eastwards tracks S/T/U tightly packed in the channel where the wind is most beneficial):

NAT-OTS vs. polar jet stream at 250 hPa isobar on 17 Feb 2020. On top, blue is 0 and purple is more than 200 km/h.
Sources: NullSchool (top), SkyVector (bottom)

North Atlantic track system

ICAO guidance for planning and using this airspace between FL285 and FL420, where almost all commercial traffic occurs, is described in NAT Doc 007.

Crossing the ocean is currently done without radar surveillance and coordinated by five oceanic area control centers (OAC): Gander, Shanwick, Reykjavik, Santa-Maria and New York East. The tracks use a set of fixed entry and exist points at their extremities:

Overall structure, with entry and exist points (source)

Those points change over time when the NAT airspace is reorganized, e.g. with the adoption of HLA in replacement of MNPS.

Track system construction

The process is collaborative between airlines and ATC.

From Wikipedia:

  The day prior to the tracks being published, airlines that fly the
  North Atlantic regularly send a preferred route message (PRM) to
  Gander and Shanwick. This allows the ATC agency to know what the route
  preferences are of the bulk of the North Atlantic traffic

From SKYbrary:

  The night-time OTS (eastbound) is produced by Gander OAC and the
  daytime OTS (westbound) by Shanwick OAC, each incorporating any
  requirement for tracks within the New York, Reykjavik, Bodø and Santa
  Maria Oceanic Control Areas (OCAs). The OTS planners co-ordinate with
  adjacent OACs and with domestic ATC agencies to ensure that the
  proposed system is viable. They also take into account the
  requirements of opposite direction traffic and ensure that sufficient
  track/flight level profiles are provided to satisfy anticipated
  traffic demand.

and:

  Following the initial construction of the NAT tracks by the
  appropriate OCA, the proposed tracks are published on an NAV Canada
  operated internet site for review and discussion by interested
  parties. One hour is allocated for this process during which any
  comments will be considered by the publishing agency and any agreed
  changes are then incorporated into the final track design.

OTS Changeover Period

From SKYbrary:

  To provide a smooth transition between the night-time and the daytime
  OTS, a period of several hours is allocated between the termination of
  one system and the commencement of the next. These periods are from
  0801 to 1129 UTC and from 1901 to 0059 UTC.

  During the changeover periods, some restrictions to flight planned
  routes and levels are imposed and opposite direction traffic must
  remain clear of the inbound (terminating) OTS.

Suggested (good) reading

Flying the North Atlantic Tracks, from AeroSavvy.
North Atlantic MNPS Airspace, from Airline Pilots Forum and Resource


What is the need for twist along a wing?

Washout or twist is a method to tailor the local incidence to achieve the ideal lift distribution over span independently of the wing's planform.

For example, if you desire to have a wing with minimum induced drag, you choose an elliptic planform. However, when stalling, this kind of wing will show a nasty roll instability because the lift coefficient is constant over span, causing one of the tips to lose lift first. To improve handling, designers learned to add chord near the tips. This by itself would create more lift at those tips than ideal and increase induced drag. So they added twist such that the local incidence decreases toward the tips. Now the wing has again the desired elliptical distribution, but has some margin at the tips to ensure that stall happens there last.

Note that washout will result in the desired lift distribution only at one angle of attack.

Washout is also necessary to adjust the lengthwise lift distribution in flying wings. Here the elevons will adjust local lift in order to trim the aircraft, and in order to avoid excessive trim deflections, washout is added so that deflections can be kept small.


How does aircraft weight affect landing distance?

If you discount aerodynamic effects, and assume the same landing speed, on a theoretical level mass makes no difference. The additional kinetic energy to be dissipated is exactly cancelled by the additional normal force. The kinetic energy is given by the formula:

E = 1/2 mv², where

E is the kinetic energy
m is the vehicle's mass
v is the speed at the start of braking

The work done by braking is given by:

W = μmgd, where

W is work done
μ is the coefficient of friction between the road surface and the tires
g is the gravity of Earth
d is the distance travelled

The braking distance given an initial speed v is then found by putting W = E, from which it follows that

d = v²/2μg

d = minimum stopping distance
v = velocity when brakes were applied
μ = coeff. of friction between wheels and road
g = gravitational constant

Mass is removed from the equation. The kinetic energy is tranferred into heat, so the larger the mass the more heat is generated. But theoretically the stopping distance is unaffected.

In reality, though, the coefficient of friction of tires does not remain constant with changing normal force. As normal force increases the coefficient of friction (μ) of tires decreases.

Since the μ does not remain linear with mass a heavier plane will have an increase in kinetic energy which is higher than the corresponding increase in friction of the tires, thus a longer stopping distance.

All of this assumes that “maximum braking” means you have as much brake power available as the maximum friction force of the tires. Above a certain weight/speed this will not be the case for an airliner. They are designed for a particular amount of deceleration force at MTOW and that will be less than the amount of friction tires can provide on a dry runway. (See this question for more details on that.) That will also cause a heavier plane to roll farther.


Does object mass have a significant bearing on wind interference?

Scaling laws are your friend here.

While the area which can be attacked by a gust grows with the square of the length increase, the mass of the drone will grow with the cube of length. This translates into higher disc loading of the props, which in turn requires them to operate at a higher dynamic pressure. The same wind gust will change forces relatively less on a bigger drone. It is the same with aircraft: Light indoor models have the same problems outside that you experienced with the small drone.

It gets even better when you look at the capability to resist rotation: Here the moment of inertia is the deciding factor which grows with the product of mass and length squared. This means the bigger drone will better resist attitude changes by the length increase to the fifth power. To be fair, gust moments will increase with the cube of length increase (area times lever arm), leaving you still with an advantage of length squared. This also means that all changes will happen more slowly, which improves the chances that the control system (the MEMS sensors onboard as well as your control inputs) will keep the situation under control.


What qualifications are required to become chief instructor at a 141 flight school (FAA)?

The requirements are in 14 CFR 141.35, Chief instructor qualifications. They're too long to quote here in full and the exact requirements depend on the type of instruction, but in summary:

Hold a commercial or ATP certificate
Hold a CFI certificate
Pass knowledge and proficiency tests
Meet minimum flight time requirements (depending on the type of instruction, e.g. 1000 hrs PIC time is required for private pilot instruction)
Meet minimum flight training time requirements

For training pilots for an instrument rating, the chief instructor also needs an instrument rating, instrument flight time and instrument training experience.


Where to find approach plates for European aerodromes?

Eurocontrol has the charts for all participating countries. You'll need to register for a free account.

https://eadbasic.ead-it.com/cms-eadbasic/opencms/en/login/ead-basic/

"The EAD Basic solution is specifically targeted at:

private pilots and general aviation;
members of the public searching for aeronautical information;
training schools;
everyone who has an interest in aviation and aeronautical information."


Helicopters do not avoid IFR. They will, however, try to avoid IMC for safety reasons. The same is true for airplanes in the same weight class. Just because the pilot is IFR rated and the aircraft is IFR certified, it does not mean they will always fly IFR, whether they are fixed or rotary wing. Light aircraft in general don’t do well in extreme IMC, whether they are fixed or rotary wing. And, many of the same FARs in Parts 61, 91, 119, 135, 136 and 137 that would require an instrument rating apply almost the same to rotary-wing as they do to fixed-wing.
The main difference between fixed and rotary wing would be their environments of operation. Altitude would be a major factor. The majority of airspace below 1200-1500 feet AGL is uncontrolled airspace. You can not get an IFR clearance unless you are in controlled airspace. Since Part 91.119(d) allows helicopters to operate at reduced altitudes and distances from persons or property, they will specifically be used in applications not conducive to IFR flight.
If a helicopter were to fly IFR,they would be restricted to at least an altitude of 1,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown by Part 91.177. This would greatly reduce the usability of helicopters. The increased restrictions of IFR flight means that there is much more opportunity to make money in VFR flight with a reduction of risk.

§91.119 Minimum safe altitudes: General.
(d) Helicopters, powered parachutes, and weight-shift-control aircraft. If the operation is conducted without hazard to persons or property on the surface—
(1) A helicopter may be operated at less than the minimums prescribed in paragraph (b) or (c) of this section, provided each person operating the helicopter complies with any routes or altitudes specifically prescribed for helicopters by the FAA; and
(2) A powered parachute or weight-shift-control aircraft may be operated at less than the minimums prescribed in paragraph (c) of this section.

As far as your assertion that commercial fixed wing operations are almost exclusively IFR, that is not a completely true statement. While I will agree with you that may apply to Part 121 operations. That is not necessarily the case for all other operations. Many commercial operations depend exclusively on flying VFR.


What to do when you accidentally land on a runway thats borderline long enough to land on?

In terms of safety, the key mistake was made as soon as the pilot made the decision to land on that runway. The corrective emphasis should be on determining why this mistake was made and taking whatever steps are necessary to prevent that mistake in the future. Especially in transport category airplanes, the crew should always calculate the required landing/rollout distance for the current landing weight, wind, atmospheric (temperature/pressure) and runway surface conditions, and this should be compared against the approach plate / airport diagram / A/FD. In most transport category airplanes this can all be computed by the FMS and it is standard procedure to do this on every single flight.

The question of what to do after the key mistake is still valid, though. I would say it depends on when the pilot recognizes that the runway is too short.

If recognized on approach, a simple go around is clearly called for and perfectly safe.
Once the wheels touch the ground, the decision gets a lot more complicated. The pilot must choose whether to reject the landing or commit to it. If you recognize it as soon as you touch down, you would probably be able to apply takeoff power and get airborne again safely. Once you've started to brake and decelerate, there will quickly come a point-of-no-return. Since you're starting at high speed, you're using up a lot of runway early in the landing rollout. Also note that in many airplanes it can take a significant amount of time to retract spoilers, stow thrust reversers, and spool the engines back up to takeoff thrust. You'll be consuming a lot of runway during this time. (At a constant 120 knots, you'll use up 2,000 feet of runway in just 10 seconds.)

In my opinion it's far better to commit to a landing. If I'm going to overrun the runway, I'd rather it happen at low speed. If you try to take off again and don't make it, your overrun will be at much higher speed, and destructive energy in a crash is proportional to the square of your ground speed.

So there's a gray area... you could attempt to take off again if you were dead certain you were going to make it. Otherwise, it's most likely best to "cut your losses" and get the airplane as slow as possible when you run out of runway, in order to minimize damage & injury. If you can get it down to, say, 30 or 40 knots, you're likely to escape without any serious injuries (the plane may take a bit of a beating, though, depending on what's beyond the end of the runway). If you do it at 120 knots, all bets are off. And you did mention a specific runway with a cliff at the end; obviously that would have to factor into the decision-making process. It may be that you simply realized your mistake too late and there is nothing you can do about it.

This leads me back to the original point, which is that the key mistake was made as soon as the pilot decided to set up an approach to that runway. The best bet is to make sure that never happens.

EDIT: After reading about the specific incident you referred to, it seems that the pilots simply mistook the airport itself for a different one with a longer runway. So it's not necessarily that they failed to calculate their required landing distance; rather they just landed at the wrong place. This is a different, but equally bad (or worse) mistake, discussed to some extent in the comments below.


Why do pilots disable the air-conditioning 'packs' during takeoff?

The "packs" (or A/C on the aircraft) are powered by engine bleed air. When bleed air is extracted from the engines, less thrust can be produced. This may be a problem if the airplane is taking off at a high elevation airport or the departure path requires a certain climb gradient to clear obstacles. This action does create some discomfort in the cabin so it's usually not preferred unless required for safety.

Some newer airplanes are manufactured with an "APU to pack" configuration - i.e. the pilots leave the APU running during takeoff, which provides bleed air to power the packs. The workload on the engines are now reduced.


Why does the angle of descent increase in a constant headwind while decreases in a sudden encounter with a headwind, in a descend?

Consider descending in zero wind, trimmed to an airspeed of 80m/s (288km/h) and a sink rate of 2m/s. You won't touch stick, trim tabs or throttles during the descent, but you will encounter a headwind at a later time. For now, ground speed is equal to airspeed and the angle of descent is 1:40.

You suddenly encounter a headwind of 20m/s. Ground speed remains at 80m/s due to inertia; Airspeed rises to 100m/s. The rise in airspeed increases lift and reduces sink rate to 1m/s. The angle of descent is now much shallower, at 1:80.

After a couple of seconds, airspeed bleeds off and the aircraft resumes its trimmed state at an airspeed of 80m/s and a sink rate of 2m/s. This time, the ground speed is only 60m/s due to the headwind and the angle of descent is now 1:30.


What happens when you break the rules while flying?

When you break the rules while flying, it falls into one of two categories:

Only you know about it
The FAA knows about it

In either case, the very first thing you do is file a NASA ASRS form.  You might ask, why does NASA care about airplanes?  They are acting as an uninterested 3rd party to your actions, and collate statistics from this information.  If the FAA becomes aware of your actions, the presence of an ASRS form in many cases limits the action the FAA can take against you.  It is always worth filling out and I have filled out a few myself.

In the case the FAA knows about it, how do they know about it?  This typically happens when you are in radar control and do something wrong or are on the ground and do something wrong.

Some examples of this are:

Flight plan in the FMS is incorrect and you make a turn off of your cleared course.  The controller will see this.
You taxi incorrectly
Runway incursion
Climb / descend through your cleared altitude

In most of these cases, the controller will just correct you.  In cases that result in a loss of separation or a runway incursion, you may get a phone number from the controller to call when you land.

Less commonly, something you do may be witnessed by an FAA inspector -- you buzzed the tower when he was on the ramp watching you.  Or perhaps he watched you get into a plane and fly off without performing a pre-flight inspection.  Perhaps you were ramp checked and something wasn't right with you or the airplane.

In all of the above cases, if you are able to file an ASRS form, do it.  If you do something that may be severe and are a member of AOPA, call their legal team and discuss the situation.

If the FAA responds to something they know about, it can range from a controller talking to you over the phone up to certificate action (suspension, revoked) to the infamous "709 ride", in which the FSDO administers a checkride and decides which, if any, ratings you keep and which you lose.


The controller wants the base to have two distinct 90° turns, from downwind to base, and base to final. And not one continuous turn from downwind to final. And no shortcuts to be taken to shorten the downwind.

It means the base will be slightly longer, and the downwind more parallel to the runway.

The controller is buying time (delaying the arrival) to accommodate someone else.

Top image is square-the-base, as opposed to the tight circular pattern—which experienced pilots tend to prefer1. (Images above are a mere representation.)

Note: exact answer will depend on the plane's exact location in the pattern.

It's one of those terms you won't find in a manual, like "hold our code".

It's a shorter time extension than "extend downwind leg":

Further reading: studentpilot.com, AOPA, 1 humorous AVweb video.


Why is the input power of an ADS-B Transponder much lower than its rated transmission output power?

The rated TX power is the maximum power emitted while transmitting. The electrical input power is much lower, because the design of the transponder is such that it accumulates energy from the input at relative lower power, to burst that out in one go on the output at high power.
The transmission of a ADS-B extended squitter has a duration of 120 microseconds. Since the modulation is pulse-position modulation, the transmitter actually only transmits for 58 microseconds per message. If the TX power is 250W, a single ADS-B message costs about 0.015 J (assuming 100% efficiency). The maximum squitter rate for ADS-B is 6.2 messages per second, equating to an average of approximately 0.1 Watt of transmitted energy. Other systems hosted by the transponder (Mode S and TCAS) are able to produce easily ten times more messages each. Mode A/C uses much fewer pulses but can have very high reply rates. This brings the average total transmitted power to over 2 W for congested airspace.
Internally in the transponder you will find big capacitor(s) that get charged by the aircraft's electical system, and discharged by the transmitter. They act as a buffer, preventing peak power surges in the aircraft system.


Which aircraft had such a luxurious-looking navigator's station?

It's a Boeing 314 flying boat. From the late 30s (look at the two rectangular windows behind the cockpit).

The last dedicated navigators on long range flights had started to disappear by the late 60s in the airline business.


Case Study: Did I need to declare an emergency?

Before we delve into this one.  Let's be clear that it is much easier for us to sit at a computer with books in hand and review decisions made under urgent circumstances.

Technically, the airport manager was correct here because per 14 CFR §91.126(b)(1):

  "Each pilot of an airplane must make all turns of that airplane to the
  left unless the airport displays approved light signals or visual
  markings indicating that turns should be made to the right..."

There do not appear to be any caveats to that rule.

To un-bind a flight from this rule, one would need to take advantage of §91.3(b)

  "In an in-flight emergency requiring immediate action, the pilot in
  command may deviate from any rule of this part to the extent required
  to meet that emergency."

In my personal experience, I have seen plenty of pilots fly around the pattern in whichever manner is convenient to them; entering on right or left bases for final, approaching for VFR straight-in landings from 15 miles out, etc.  So far, I haven't seen any repercussions for these actions, which is probably why your instructor did not agree with the airport manager.

Another thing that shouldn't go without being said is that this situation was none of the airport manager's darn business.

By verbally acknowledging that there was not an emergency, your instructor placed a liability on himself.  §91.3(b) allows the pilot to deviate from a part 91 rule, but to my knowledge, there is no statute that actually requires recognition of an emergency to be verbally declared or announced under non-ATC-controlled VFR flight.

By leaving the question, "is there an emergency?", unanswered, there is a chance to retrospectively say, "yes, we had an emergency and that's why we deviated from the rule."  However, since he told the airport manager that it was only an urgency he kind of shot himself in the foot if someone were to decide to raise the right turn as a legal issue, but I would be very surprised if anyone does.

To summarize and give you a more direct answer.

You had a valid emergency
You had no responsibility to verbally declare it
You did deviate from a legal regulation to meet the needs of that emergency

Sounds to me like you've got a very competent instructor.

Edit: I came across this Letter of Interpretation, which is sort of related to your situation.


How often are heavy aircraft brake pads changed?

The 747-800 uses carbon brakes made by the Goodrich company and according to this article,

  The entire industry is leaning towards carbon brakes, Honeywell
  executives assert. Lufthansa Technik also sees a trend towards carbon
  brakes, as the mean time between repairs (MTBR) for carbon brakes is
  1,500-2,000 cycles, compared with some 1,100 cycles for steel brakes.

Also of note, take a look at this video on the testing of the brakes.


What alternatives to pitot static systems are available or in development?

A number of systems are under development- most are optical systems- determining airspeed using LiDAR. NLR, for example has developed an Optical Air Data System for this purpose:

  The  developed  system  applies  the  LiDAR technique to measure air speed in four different directions. The aircraft’s TAS (True Air Speed),  AOA  (Angle  Of  Attack)  and  SSA  (Side  Slip  Angle)  are  calculated  from  these  speed  measurements.

Other systems are in prototype stage- including a photonic system that is based on back scattering of light, but none of them are yet operational.


Are there multiple reasons for the decrease in pressure over a wing?

The laws of physics don't work in isolation. They always apply all at the same time¹.

Most of them don't describe causality, but relations that are known to be always satisfied². If you know the speed increased, you can conclude the pressure decreased, but if you know pressure decreased, you can similarly conclude the speed increased. Neither is the reason for the other, rather the properties of fluids are reason both always happen together.

And last but not least the laws of physics as we normally use them are not fundamental, but are various perspectives on the underlying properties of the universe and as such have a lot of overlap. Therefore you can usually arrive at the same conclusions in many different ways (provided you properly account for approximations involved).

In this case, the air following the surface of the wing, pressure dropping, the flow accelerating and the streamlines squeezing are all aspects of the one behaviour of fluids—for which there is no simpler way to quantify than calculating the full set of Navier–Stokes equations (there are some simpler models like Kutta–Joukowski theorem, but can't start from the wing shape, but need some experimentally-determined characteristic values of it).

On the low level, pressure is the total momentum imparted by the collisions per unit time and area. So obviously if lower pressure is seen, the collisions must be fewer or weaker. In practice they are both³. However, there is no simple explanation for it on the molecular level either. It is a result of the complex dynamics that averages out to the Navier–Stokes equation on the macroscopic level.

¹ School lessons often fail to teach this by discussing each in isolation and never synthesizing. However, lift is surprisingly complex phenomenon, which requires applying many of them to model.

² Well, at least not observed not to be satisfied, because positive proofs are not possible.

³ The enthalpy decreases, which means the particles move slower and that means they hit both less often, and with less force. The density also decreases a bit, so there is a bit fewer of them per unit volume too. However, this is all easiest to derive from the macroscopic thermodynamic laws. We do have microscopic explanations for them now, but trying to compute anything directly at the low level is futile due to the vast numbers of particles involved.