How much thrust is required for a Boeing 747 to "keep flying" at 4 km altitude?

The QRH (Quick Reference Handbook) contains a few tables for flight with unreliable airspeed. The one for holding comes closest to the situation you asked about:

(Boeing 747-400 QRH 20.2 - Performance Inflight - CF6 Engines)
As you can see, holding at 10000 ft altitude requires between 59.7% and 77.4% N1 depending on weight. You asked about 4 km, which is about 13000 ft, so a little more will be required.
There is also a table for cruise speed at various altitudes:

(Boeing 747-400 QRH 20.1 - Performance Inflight - CF6 Engines)
You can extrapolate the values shown here between 10000 and 20000 ft altitude to get the required thrust at 4 km. Note however, that the speed flown here is higher (290 KIAS or Mach 0.84) than the one required for maintaining altitude.
If you combine the information from both tables, you should get a good idea of the required N1 in your situation. The number will however strongly depend on the weight of the aircraft.


First I'd just like to comment that "near miss" is a bad term (as falstro also noticed). It seems to say that the planes "nearly missed", implying they didn't miss. The FAA uses the terms "Near Midair Collision" (NMAC) for serious incidences, and "loss of separation" for less serious ones. As such, terms like "near miss", "close call", and "narrowly escaped disaster" are not well defined.

ATC does usually have radar. The data is recorded and can be analyzed later. Of course, not all areas have radar coverage. In these cases it is up to pilots to report if they feel safety was compromised. They can use the Aviation Safety Reporting System, which is part of the Aviation Safety Information Analysis and Sharing system.

Especially with commercial flights, Traffic Collision Avoidance System (TCAS) is also used. If TCAS issues a Resolution Advisory (RA), which commands pilots to take action to avoid a collision, the pilots are usually required to report the incident.

A "loss of separation" would be anything less than the required separation.

According the the FAA:

  A near midair collision is defined as an incident associated with the
  operation of an aircraft in which a possibility of collision occurs as
  a result of proximity of less than 500 feet to another aircraft, or a
  report is received from a pilot or a flight crew member stating that a
  collision hazard existed between two or more aircraft.

That and more information about reporting incidents can be found in Section 6 of the AIM.


What are RNP and ANP in area navigation?

RNP is a numerical value that refers to the level of performance required for a specific published procedure.  If the procedure has an RNP 10, then the on-board navigation equipment must be able to calculate its position to within 10 nautical miles. If the procedure has an RNP 0.3, than the equipment must be able to calculate its position to .3nm.

ANP is the "actual" level of performance being experienced real-time. The on-board navigation equipment estimates the quality of the reception and determines how "reliable" it thinks its own position is.  If the estimate of reliability is high, then the ANP is lower.  An ANP value of 0.6 indicates that the navigation equipment is confident of its own actual position to within .6nm.  Essentially, this means that if the equipment puts a point on the map of where it thinks it is, there is a circle around that point with a .6nm radius and the aircraft is somewhere within that circle.

If the RNP required value is lower than the ANP value, you cannot use that procedure.  If you're using a procedure, you must monitor the ANP value. If, at any time, the ANP goes above the RNP, you must exit the procedure.

Here is an image of a Boeing 737 FMC displaying the current ANP (.06) and the RNP (2.0).  Courtesy of http://www.b737.org.uk


Is/why isn't the Antonov 124 to 225 wing upgrade method common?

With straight wings the root extension method is very common. Airplanes that come to mind are

Me-109 H (high altitude version with increased span)
Beech Twin Bonanza and Model 65 Queen Air (used the Bonanza wing from the engines out)
SB-10 (uses SB-9 wings stuck to a new carbon-epoxy center wing).

This is impractical with swept wings because of the strong twist and airfoil changes which are needed at the wing root to keep the isobars straight on the swept wings. The only way to increase an existing wing's size was used for the A340-500/600 by inserting a triangular section at mid-chord into the A340-200/300 wing which also allowed to increase its wingspan.

Source: Evolvability and design reuse in civil jet transport aircraft


What are some examples of warning areas and restricted areas?

I'll provide information for the US airspace. However many countries, ICAO members, will have similar concepts and procedures.

Short answer

You are not required to follow any procedure for entering a warning area or an inactive restricted airspace. In the latter case, you need to ensure the area is actually inactive. A safe practice is to contact the controlling agency of the area prior to enter any warning or restricted one.

The longer answer below develops a bit around special use airspaces which encompass warning and restricted airspaces among other. You'll also find two examples of these areas.

Context

The airspace over the US is open to navigation, a part of this airspace benefit from services provided by air traffic control (ATC), e.g. safe separation and traffic information.

This controlled airspace includes airport areas and airways, and other areas of interest. It is is ruled by air regulations relative to airspace classes. In the US these regulations are found in document 94 CFR 91.

source)

Some limited areas, that may be permanent or temporary, can be prohibited or restricted. Together they constitute the special use airspaces (SUA)

Special use airspaces

SUA (Wikipedia):

  Special use airspace includes: restricted airspace, prohibited
  airspace, military operations areas (MOA), warning areas, alert areas,
  temporary flight restriction (TFR), national security areas, and
  controlled firing areas.

The SUA are repertoried by the FAA: SUA Web site.

You may search by name or scan the map. R denotes a restricted airspace, and W a warning area.

More on SUA: Course Notes, Dennis Seals, FAA

Your question is limited to warning areas and restricted airspace.

Restricted airspace

Wikipedia:

  Restricted areas denote the existence of unusual, often invisible,
  hazards to aircraft such as artillery firing, aerial gunnery, or
  guided missiles. Penetration of restricted areas without authorization
  from the using or controlling agency may be extremely hazardous to the
  aircraft and its occupants.

See also chapter 3−4−3. Restricted Areas of the FAA-AIM.

Entry: Forbidden when active, subject to ATC clearance on a case by case basis.

For areas that have a scheduled activity, times of activation are published in the AIP. When inactive, a R-area is just a like any other location of the surrounding airspace class. When active it is just forbidden to enter it (albeit FAA may deliver specific clearances if solicited).

For VFR flights, contacting ATC prior to entering an inactive restricted area is not mandatory per regulations, but is a good practice regarding safety. IFR flights under monitoring of the ATC, will not be authorized to enter an active restricted area.

Wikipedia:

  Restricted airspace zones may not be active at all times; in such
  cases there are typically schedules of local dates and times available
  to aviators specifying when the zone is active, and at other times,
  the airspace is subject to normal VFR/IFR operation for the applicable
  airspace class.

Activity time may happen unscheduled for some R-areas. A schedule cannot be published, in this case a NOTAM is used to inform airspace users.

Wikipedia:

  A few zones are activated by NOTAM; an example is R-2503D over Camp
  Pendleton in southern California, between San Diego and Los Angeles.
  This particular zone, beginning at 2000ft above sea level over most of
  southern Camp Pendleton, can only be active for a certain number of
  days per year, thus allowing small planes to fly a direct route over
  land between the two metro areas instead of being diverted offshore or
  into mountainous terrain further inland.

Example: Restricted areas R-2501 around the Twentynine Palms Marine Corps Air Ground Combat Center:

GlobalSecurity.org:

  The Twentynine Palms Complex is located in the Southern California
  desert approximately 115 NMI northeast of Los Angeles, CA. The
  Twentynine Palms Complex provides a vast land and restricted airspace
  (R-2501) area for live ordnance employment and combined arms training
  of infantry units, armored vehicles, artillery, and air support.

  The complex includes the following instrumented area: R-2501E

  The following are training, and Military Operating Areas (MOAs)
  associated with the Twentynine Palms complex:

  R-2501N
  R-2501W
  R-2501S
  Bristol MOA
  Sundance MOA
  Range Training Areas (RTA)

Description of R-2501N from Order JO 7400.8S:

R-2501N Bullion Mountains North, CA
Boundaries.
Beginning at lat. 34°30'00"N., lon g. 116°26'23"W.;
to lat. 34°36'00"N., long. 116°28'03"W.;
to lat. 34°40'30"N., long. 116°29'43"W.;
to lat. 34°43'00"N., [...]
Designated altitudes. Unlimited.
Time of designation. Continuous.
Controlling agency. FAA, Los Angeles ARTCC.
Using agency. Commanding General, Marine Corps Base, Twentynine Palms, CA.

This area around a large military complex is active (restricted) 24x7, at any altitude. A pilot who wants to enter this area for some reason needs to contact either the controlling agency (Los Angeles ARTCC) or the using agency (Marine Corps Base).

Warning area

Chapter 3−4−4. Warning Areas of the FAA-AIM.

  A warning area is airspace of defined dimensions, extending  from
  three nautical miles outward from the coast of the U.S., that contains
  activity that may be hazardous to nonparticipating aircraft. The
  purpose of such warning areas is to warn nonparticipating pilots  of
  the potential danger. A warning area may be located  over domestic or
  international waters or both.

Entry without specific clearance, but can be hazardous. Contacting ATC prior to entering a warning area is not mandatory per regulations, but is a good practice regarding safety.

Example: Pacific Missile Range Facility (PMRF) NS Barking Sands.

GlobalSecurity.org:

  The area surrounding Kauai is divided into warning areas with W-186
  and W-188 controlled by PMRF. The Fleet Area Control and Surveillance
  Facility (FACSFAC) controls W-187, 189, and 190. Space, air, and
  surface tracking are accomplished from PMRF precision-tracking radar
  sites at elevations of 75 ft., 1700 ft., and 3800 ft. These are
  supported by radar systems operated by agencies external to PMRF.

Description of W-188 from Order JO 7400.8S:

W-188 Hawaii, HI
Boundaries. Beginning at lat. 21°58'19"N., long. 159°48'45"W.;
to lat. 21°58'27"N., long. 159°59'50"W.; [...]
Altitudes. Surface to unlimited.
Times of use. Continuous.
Controlling agency. FAA, FAA, Honolulu Control Facility.
Using agency. Commander, Pacific Missile Range Facility, HI.

More:

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


Could you start both A320 engines with APU BLEED on?

I have been flying A320s for over two years now and this is the first time I am hearing this. Normally the engines are always started using the APU with its bleed providing air for the air starter motor. So, in normal operations, cross bleed is set at AUTO, APU bleed is turned on and both the engines are started with the help of the APU. Once the engines are started APU bleed is turned off and the APU is shut down. Below is the after start flow of the A320. The green shows the flow of the pilot who starts the engines. As you can see, once the engine mode selector is set to norm, APU is shut down.

The procedure you are talking of is called a cross bleed start which is used when the APU is inoperative for the flight. It is also used by airlines that enforces one engine taxi to save fuel. When APU is not operational, we start one of the engines using an external air source. Once the engine is started the external unit is removed and then to start the next engine we use the bleed from the already started engine. To do that we open the cross bleed and increase the thrust on the running engine until the bleed pressure is sufficient enough for the second engine start up. As soon as both the engines are running we set the cross bleed to AUTO and revert back to normal operation.
As I have told before, I have never heard of any concerns regarding harmful gases coming of the APU bleed. Back when I used to fly Dash 8s we had issues in some of our airplanes smelling of burning oil once engine bleeds are turned on after start up. The airline consulted with Bombardier and they sent a bulletin which said that sometimes oil drippings from engine bearings can fall onto the bleed ducts. Because the duct temperature tends to be quite high, the oil burns off and the smell goes into the cabin. According to them, the lubrication oil used in airplanes is not hazardous or poisonous to human beings. I would say, it applies to all transport category airplanes with gas turbine engines because nearly all of them uses the same type of oil.


Is it possible for a modern commercial airliner to stop being tracked without substantial mechanical failure?

The device you are talking about is called a transponder.  This is a device that listens for a signal (an interrogation) and responds with information about the airplane including an ATC assigned code, altitude information and additional aircraft info for certain equipment.

There are 2 ways ATC watches airplanes:

Primary Radar
Secondary Surveillance Radar

The transponder is interrogated by the Secondary radar and the response is listened for.  Even with no transponder, the aircraft can still be tracked by primary radar.  This is just a normal radar that is good at seeing airplane sized objects and not so great at seeing weather and can occasionally spot a large flock of birds.  The primary radar is what provides the "blip" on radar and tracks the airplane.  The datablock ATC has on the airplane comes from the secondary, so what ATC will see is a blip with no information.  Turning off the transponder is as simple as setting it to OFF or pulling a circuit breaker and yes, it can be selected OFF in flight, it is just a switch.

The problem with radar is that it only works so far from a radar transmitter and the further away you are the higher you must be to be seen by the radar.  Over the ocean away from land, you are going to be on the fringe of radar or out of radar contact completely and thus unable to be tracked directly by ATC (at this point, non-radar procedures such as position reporting and ETAs can be used to track positions).

The flight in question was apparently visible by a military radar before it disappeared from the scopes (it allegedly observed what appeared to be a turn back toward its origin).


What is the weather term for snow and dust mixture?

I lived and flew in North Dakota for about three years. While I was there, people talked about (and I experienced) the delightful mixture of snow and dirt called snirt. It can be the result of plowing sanded roads, and also can be caused by the high winds that come out of Canada blowing dirt from fields onto areas still covered in snow. Google image search has some good examples.

I have a feeling that's what was described by your friend. It appears in Wikipedia's list of types of snow, but as far as I am aware it is not an FAA or NOAA term.


Can a pilot change out of uniform during breaks on a long flight?

The answer depends a lot on the jurisdiction and airline, but Yes, pilots can change out of uniform during breaks on long flights.

A 15 hour flight would have 4 pilots who are all in the flightdeck for takeoff and landing but then divide roughly 14 hours of cruising time into equal rest breaks.

Typically 2 pilots will be paired together and take breaks at the same time. At some airlines they would have 2 pilots take a 7 hour break and then switch off. At other airlines they  take two 3 1/2 hour breaks.

Each 2 person crew would be off the flight deck for half of the 14 hours spent at cruising altitude (15 hour flight) I find most crews prefer two shorter breaks as opposed to one long break. With a 3 person crew they would have each pilot take 1/3 of the cruising time as a break.

Most airlines operate with one main crew who does both the takeoff and Landing. This is because the second crew is generally less qualified. In some cases the "augment" pilots are only licensed to operate during the cruise portion of flight. Some airlines will operate with two fully qualified Captains and two fully qualifed First Officers and they can divide the takeoff and Landing between the two Crews.

Most pilots change out of uniform during their breaks. Some airlines require the pilots to wear their hat and tie when they leave the flight deck.  Others are much more relaxed.

I have seen pilots in T-shirts enter and exit for breaks.


What are the disadvantages of having vortex generators?

Cost.  A set of Micro AeroDynamics VGs can run around $1500 plus installation cost.  On my plane they are installed on the top of the wing, the sides of the vertical stabilizer (fin), and the bottom of the stabilator.  I wasn't aware there were other suppliers of STC'd VGs for certificated planes. I installed mine in early 2000s, price may have gone up some since then.

They do work well, lowering stall speed while allowing the controls to be effective the same as at higher speeds. No noticeable loss of airspeed at higher power.


Why can a localiser be used without a glideslope, but not vice versa?

Adding to @J.Hougaard's practical reasons, there is one technical reason in the existing standards I can think of:

The identification signal (morse code) is provided by the localizer, not the G/S, so G/S-only approaches would be unidentifiable. (ICAO Annex 10 Vol 1 § 3.1.3.9)

Side note: I'm not sure if there can be a workaround for it using existing airborne equipment, since a G/S works on UHF (which is transparent to the pilot, i.e., the pilot only selects the LOC VHF frequency, and the G/S UHF frequency is simply paired).

The identification is likely one of the reasons behind the following:

  Inoperative localizer. When the localizer fails, an ILS approach is not authorized. (FAA AIM)

There is no mention of an operative G/S remaining. Whereas a failed G/S does not prohibit using the LOC for a LOC-only approach (after adjusting the minima).


Do pilots have their own in-flight entertainment?

I am not aware of any legal requirements, but rules may differ according to the country of jurisdiction.

Generally it is up to the company that a pilot works for to establish their own rules to cover "in-flight entertainment" in the flight deck. Most companies do not allow it. It has been my experience that the rules are generally ignored and common sense rules are used instead.

During non-critical phases of flight, pilots will often read newspapers, books, iPads etc. Many will do crossword puzzles or Sudoku. A few will even listen to music or watch a video, but it is pretty rare.

In 40 years of flying, I can't recall ever seeing a pilot play a video game or flight simulator.


It does not appear that MCAS was in any of the maintenance documents. This was part of the issue with the Lion Air crash. On the previous flight with the accident aircraft, MCAS acted on the faulty sensor data, but the pilots used the trim cutout and completed the flight. They had no reason to suspect that a trim issue could be related to a faulty AOA sensor, so just the warnings for IAS and ATL DISAGREE and FEEL DIFF PRESS were logged for maintenance. As you noted, if they had known the connection, they might have diagnosed the true cause and either replaced the AOA sensor or MMEL'ed it. Instead they focused on the Air Data Module and elevator feel computer. It wasn't until a couple weeks after this crash that Boeing sent a message to operators describing MCAS.

It's also unlikely that the MMEL would have allowed MCAS to be completely disabled. This would have required extra documentation and possibly training for the pilots on how the plane would handle differently without it. This additional training is what MCAS was designed to avoid, and would have defeated the purpose of having it in the first place. Also, if it were that simple, it seems like they would have taken this step rather than grounding the entire fleet.


What to look for when purchasing a headset

I've had problems in the past with headphones feeling cramped on my
  ears, which I don't want to be the case with my headset

Do your best to test them out before you buy. Some pilot shops will let you put them on your head and if you are nice to the people that lurk around the airport they may lend you one for a flight to try out. I find that the Zulu's have bigger ear cups than the Bose but I don't have any hard numbers on size this is personal experience wearing them.

  First of all, is noice-cancelling actually that important(in terms of
  health and comfort)

Yes, just ask any one that flew in the pre-headset days. I personally find that I can comfortably fly for longer times with an ANR headset. Another thing to note is that the ANR head sets tend to not squeeze your head quite like the passive headsets I find this to be the real gain in comfort.

One of the big functional differences is that some of the LightSpeed headsets do not cary a TSO, I belive all of the Bose do. This may impact your ability to use them for commercial purposes in the future. You can find a discussion on it here.


How do i find a supercritical airfoil for my preliminary design?

Answer to the implicit question: Yes, the more recent airliner airfoils are indeed secret. Look for reports like this to see what is out there.
Answer to question 1: Try the linked NASA Technical Paper 2969.
Answer to question 2: Your viscosity is for sea level. Try to use the value for the tropopause and it will be only ⅓ as large.


why do wings have high aspect ratios on commercial airliners?

Aerodynamically, you want the aspect ratio to be as high as it can be (for a given wing area). You want infinite wingspan, because that results in no induced drag. But that is not very practical at airports, and a bit heavy.

Structurally, you want short stubby wings because they have a very low bending moment. In fact structurally, you want zero wing span. But that is not very practical at take-off time.

As always, aerodynamic desirability implies structural objections, and vice versa. The aerodynamicists need to strike a deal with the structures engineers: a balance needs to be found. As long a wing span as possible, with as thick a profile as possible, using a material that is as light as possible. So a long wingspan is desirable and is only limited by structural constraints: as you say, at a certain point the longer wing span's increased weight will offset any aerodynamic advantages.

In aluminium, the optimum was reached over the course of a few decades. But now there is a new material with a better strength/weight ratio: composite carbon fibre. Carbon is much stronger than aluminium, and it is woven in a matrix of resin, with most wires running in the direction of highest stress. With carbon fibre, even the direction of material strength can be optimised. And the B787 and A350 have even higher aspect ratios than the B777.


How much thrust do you lose by putting chevrons on a engine?

The main purpose of the Chevrons is the reduction of engine noise. During research into this, NASA tested a number of configurations under simulated flying conditions and measured the nozzle thrust coefficient given by,

$C_{T_{r}} = \frac{F^{d}_{g}}{F^{i}_{g}}$

where,

$F^{d}_{g}$ is the measure gross thrust and

$F^{i}_{g}$ is the ideal gross thrust

We have,

$F^{i}_{g}$ = .{m}$_{c} v_{i,c}$ + .{m}$_{f} v_{i,f}$

where .{m}$_{c}$ is mass flow rate of core, .{m}$_{f}$ is mass flow rate of fan and $v_{i,c}$ and $v_{i,f}$ are core and fan ideally expanded jet velocities respectively.

The reduction in nozzle thrust coefficient was compared with baseline (no modifications) configuration.

Source: NASA/TM—2000-209948

The configuration used in engine (Chevrons in the fan and nothing in the nozzle produced the lowest loss of thrust coefficient, 0.18.

However, the noise reduction was lesser in this configuration compared to the others. Further modifications have been carried out in the chevrons used in production engines (they are rounded, for one). So, the noise reduction has been obviously improved, though the minimal loss of thrust would've been maintained.

Note: All data from Acoustics and Thrust of Separate-Flow Exhaust Nozzles With Mixing Devices for High-Bypass-Ratio Engines, Naseem H. Saiyed, Kevin L. Mikkelsen and James E. Bridges, Prepared for Prepared for the
Sixth Aeroacoustics Conference and Exhibit, Lahaina, Hawaii, June 12–14, 2000


Why can the A-10’s engines flame out merely from ingesting smoke from its gun?

I found a 1955 NACA research memorandum entitled "STALL AND FLAME-OUT RESULTING FROM FIRING OF ARMAMENT", specifically looking at flameouts in the F-86, F-94, and other aircraft associated with the firing of guns or rockets (especially in the case of the F-94, which had a nose-mounted rocket pod).  While the analysis in the paper does concern itself with a high speed (Mach 0.9) and high altitude (45,000 ft) scenario, I think that we can reasonable interpret its results for the A-10.

The paper points to the following factors following, from the aircraft firing a weapon, which could lead to an engine flameout:

(1) Increased inlet temperature

(2) Changed inlet pressure

(3) Distorted inlet-pressure and temperature profiles

(4) Entry of combustibles into engine

(5) Reduced oxygen content in gases entering engine

Of all of these, the first item was noted as the most significant, and the first step in the chain of events that results in reduced oxygen in the combustor, or, if you'd like it stated another way, an increased fuel-air ratio.  Since the exhaust gas from the gun is much hotter than ambient (anecdotally, the gas block of an AR-15 can hit up to 600 deg F after firing 600+ rounds, so I'd imagine the barrels of the GAU-8 would be at least that) and does not cool completely before entering the engine, the engine has to deal with its effects -- and the first stage to see it (ignoring the fan) is the compressor.

The compressor of a jet engine is, essentially, a fan, but one that spins fast enough to compress the air coming into the engine such that you can burn fuel in the combustor and push the maximum amount of gas as quickly as possible out the back of the engine.  However, in order to operate, the combustor needs a low enough fuel-air ratio to allow combustion (i.e., enough air to burn the fuel it's dumping in).  Similarly, the combustor is a fan, made up of a series of airfoils -- if these airfoils stall, the combustor doesn't work anymore...again resulting in too little oxygen in the combustor to allow for combustion.

Considering inlet temperature first, we can think about it from a gas-law point of view.  If I heat a volume of air, its density will decrease.  Hence, if I'm taking the same volume of air into my engine and compressing it, I'm taking in significantly less oxygen on a per-molecule basis.  If I take the ideal gas law as a rough estimate and double the temperature, my density is cut in half -- so now my engine has access to half the air.  According to the NACA study (and your picture), gun gases typically spread out in front of the aircraft, leading to a greater heating effect in the surrounding air, even if that is more spread out.  Between this and a momentum exchange between the gun gas and the ambient air, as the gun exhaust is slowed by the still, ambient air, the NACA study found that firing four 20 mm cannon reduced the inlet pressure to their study aircraft (an F-94, I believe) by as much as 9%.

So, this is a lot of hand-waving, so let's look at the effect all this on the jet engine in the NACA study.  The temperature increase on the plot is an inlet temperature increase -- and it doesn't take much of a temperature rise to significant decrease the mass flow rate of air through the engine...and stall the compressor.

Compressor stalls can also occur due to distorted inlet air velocity profiles (a fan is typically designed for air to come in axially and uniformly), another side effect of exhaust gases non-uniformly mixing with the inlet air.  Similarly, if burning particulate matter is ingested, this could change the velocity profile inside of the compressor itself by artificially decreasing the pressure ratio across the compressor.  Naturally, if combustion is delayed until the combustor, these particles will have little effect.

You can also look at this from the perspective of the downstream effect of having less air moving through the engine, or the fuel-air ratio in the combustor.  This could also be affected by a decrease in the available oxygen in the gun gases as well.

As we can see, though, changes in inlet temperature in the compressor appears to be the more sensitive parameter for this particular engine.  As mentioned in the NACA report:

  The increase in compressor-inlet temperature during armament firing
  is probably the most important single factor affecting engine performance. This increase in temperature is sufficient by itself to account
  for the observed occurrences of compressor stall and flame-out.

Hence, according to this article, the final solution to the A-10's problem (while gun gas deflectors and the like were considered) was a reformulation of the propellant used in its shells and the addition of a link between the gun trigger and the engine ignition system.


How do you calculate total drag on a wing?

Typical values of e are between 0.7 and 0.98 in subsonic flow, and 0.3 to 0.5 in supersonic flow. Since it is in the denominator, e cannot become 0 or drag would be infinite. A square wing has an e anywhere between 1 (with aspect ratio close to zero) and 0.8 (with high aspect ratio and away from the design point for the twist distribution)

As a rough first-order assumption, the zero-lift drag coefficient is constant over the moderate AoA range when the flow is attached over the full chord. This drag is the sum of friction (shear forces tangential to the wing surface) and pressure drag (caused by pressure on the backwards-facing sections being lower than on the forward-facing sections of the airfoil, again due to viscosity).

Of course, once you have a full airfoil polar, your results will be more precise if you use the particular value of the drag coefficient at the specified angle of attack. However, sometimes you will need to calculate lift and drag without knowing the angle of attack, and then you fall back to the first-order approximation. For an example where this assumption is useful please read this answer.


Is a complex airplane endorsement required to act as PIC of a plane without all three elements of the "complex airplane" definition?

No, you do not need a complex airplane endorsement for this airplane because it doesn't have retractable gear, unless it is a seaplane.

All three elements are required for that endorsement to be necessary for landplanes.

A jet-engine is not a controllable-pitch propeller, therefore it would not require a complex endorsement even if it has retractable gear and flaps.

However, the above would require a type-rating because it is a jet.

An airplane with a controllable-pitch propeller and retractable landing gear that isn't equipped with flaps would also not fit the definition of complex, so you are absolutely right.

See §61.31(e) Additional training required for operating complex airplanes

The definition for complex is in the Airplane Flying Handbook Ch 11,

  “A complex airplane is defined as an airplane equipped with a
  retractable landing gear, wing flaps, and a controllable-pitch
  propeller. For a seaplane to be considered complex, it is required to
  have wing flaps and a controllable-pitch propeller.”

The definition for complex as shown in 14 CFR §61.1(b)(iii):

  "Complex airplane means an airplane that has a retractable landing
  gear, flaps, and a controllable pitch propeller, including airplanes
  equipped with an engine control system consisting of a digital
  computer and associated accessories for controlling the engine and
  propeller, such as a full authority digital engine control; or, in the
  case of a seaplane, flaps and a controllable pitch propeller,
  including seaplanes equipped with an engine control system consisting
  of a digital computer and associated accessories for controlling the
  engine and propeller, such as a full authority digital engine
  control."


What are FARs & where can I find them? What is FAR 23, 25, 135, etc?

In the US the "Federal Aviation Regulations" (FARs) is shorthand for referring to Title 14 of the Code of Federal Regulations.

You can browse all sections of FARs at ECFR.Gov.

FAR 23, for example, covers airworthiness standards. § 23.25 regulates weight limits.


Can turboprop blades break the sound barrier?

Can it happen: Yes

Does it happen: Generally no

As a matter of the pure physics propeller tips can go supersonic and some times do. There is at least one case of this being done by design on the XF-84H which was built to be one of the fastest propeller planes.

The main issue it faced was the noise generated by its supersonic prop. It is considered one of the loudest aircraft ever made as its prop was supersonic even at idle speeds. Due to the shock waves generated by breaking the sound barrier great care is often taken to ensure that propellers don't go supersonic.


Why is *vertical* autorotation in a helicopter not recommended?

When the engine fails in a single engine helicopter it can autorotate back to earth: it gives up potential energy from reducing height to keep the rotor turning, which then continues to provide lift. Autorotation can  take place straight downwards in vertical flight, but the general recommendation is to maintain forward speed, like a fixed wing gliding: the rate of descent is much lower if there is forward speed.

 Image source

We associate helicopters with hovering, but this is a strenuous effort. Even a bit of forward velocity generates translational lift, which makes it much easier for the rotor to generate lift:

The forward inflow tilts the lift vector forward, decreasing induced drag and blade torque, and increasing lift. Or stated in a different way: the airstream is flowing in already, and does not need to be accelerated from zero. The rotor now starts to work more like a fixed wing does.
The airstream through the rotor experiences less interference from the fuselage.

The effect of forward velocity on auto rotational rate of descent is depicted in a graph in this book:

Going back to vertical autorotation: the vertical upward airstream needs to go through the rotor fast enough to reach the windmilling state, so that lift is created by decelerating the air passing through it. If we compute the lift component per area of a vertically autorotating rotor, it is comparable to a $C_D$ value of 1.1 to 1.2 referenced to the rotor area. According to this source:

a flat plate has a $C_D$ of 1.28
a parachute has a $C_D$ of 1.4.

So in vertical descent, the auto-rotating rotor is almost as good as a parachute of the same area - it’s just that the parachute size is a bit small for the typical payload of a helicopter, resulting in vertical descent speeds of between 3,600 to 6,200 ft/min. By way of comparison:

Air France 447 fell to the ground with a vertical descent rate of 10,000 ft/min.
Captain Sullenberger's plane took four minutes to reach the Hudson in a proper glide, from 2,060 ft altitude = average of 500 ft/min.

Two factors make autorotation much more survivable though:

The descent rate can be “flared” by pulling the cyclic back (exchanging forward velocity for more rotor kinetic energy) and then collective up just before ground contact, slowing down the rotor and increasing lift. The pilot only has one shot at this.
The descent rate is a lot less if autorotation is done at a forward speed,   the best one being the optimum climb speed.

Note that in a vertical descend there is no pullback of the cyclic, only increase of collective - plus the rate of descent is higher. A higher speed and fewer means to brake, that is not recommended!

A side note

The windmilling rotor does not turn the other way! The incoming air from underneath tilts the lift vector forward, like in a glider. Part of the rotor disk is driven by the aeroforces into the same direction as it was when still under power.

 Image source


When to reduce power on takeoff (Cessna 182 or similar)?

The "official procedure" is the one dictated in your aircraft's POH/AFM.
Within the leeway that document gives you (and many of them give you a lot of leeway) this is definitely one of those "endless debate" subjects.

Personally in a single-engine piston aircraft unless the POH directs otherwise or operational considerations (like an altitude restriction from ATC) require something different I would maintain full power (and all other takeoff settings - fuel pumps, etc.) until reaching 1000-1500 feet AGL (depending on what the terrain and obstacles in the area are like), then configure the aircraft for a reduced-power cruise climb if appropriate.
Whether or not the first power reduction is a time of increased failure is irrelevant to me - I operate on the assumption that the engine can fail at any time, and should the engine fail (for whatever reason) I want adequate distance between myself and the ground to make some decisions, confirm my landing spot, and prepare myself, my passengers, and the aircraft for whatever is going to happen next.

1000 feet AGL is my minimum threshold for that sort of activity. It's possible (maybe even likely) that I'm imposing additional wear on the engine in requiring full power for this long, but if the engine decides to fail on climb-out it's not going to matter how "nice" I was being to it on all my previous flights - the only things that are going to matter are my altitude, airspeed, and landing options, and I'm going to want as much altitude and airspeed as I can get to help maximize my landing options!

There are some conditions where I would reduce power sooner than 1000 feet AGL if necessary - for example, if I can't maintain oil or cylinder head temperatures "in the green" in a full power climb a power reduction (or pitch reduction) to keep those engine parameters happy would be in order.

There are also some aircraft/engines which have a continuous power restriction (Full throttle operation limited to 3 minutes,  maximum continuous power 2400 RPM, or similar admonitions you'd find in your POH). In those cases the restrictions should obviously be observed (the engineers who set the limitations had a good reason for doing so), and observing those requirements may necessitate a power reduction or other configuration changes prior to reaching 1000 feet AGL.

Finally, I'm not sure what kind of engine is in your hypothetical Cessna but as an additional point of reference Lycoming has this to say about takeoff operations:

  Operating Your Lycoming Engines At Takeoff And Climb

  Because there are
  a wide variety of Lycoming engines in operation, the paragraphs below
  may be helpful in understanding the different modes of operation
  required when operating each type at takeoff and climb power settings.
  The Pilots Operating Handbook for the aircraft in which the engines
  are installed should be the final authority as to how the engine
  should be operated.

  DIRECT DRIVE ENGINES

  Most normally aspirated
  engines are rated at full power for takeoff and climb indefinitely,
  provided engine temperatures and pressures are within the green arc
  area of the engine instruments. Extra fuel, sensible airspeed, and
  cowl flaps, if available, are all helpful in keeping cylinder head
  temperatures within desired limits during takeoff or climb.
  Climb
  requirements may vary; as an example, on a warm day with the airplane
  close to gross weight, and a direct drive engine with a fixed pitch
  prop, the pilot will need full throttle all the way to cruise
  altitude. The same airplane on a cold day and lightly loaded may not
  require full power for climb. After full throttle at takeoff, the
  pilot may want to reduce power 100 or 200 RPM and still not see
  performance suffer. Those direct drive normally aspirated engines with
  a prop governor are also rated indefinitely at full power, and the
  manuals all recommend full power for takeoff, but specify a small
  reduction in power, generally to 85% power climb. Study the specific
  airplane Pilot's Operating Handbook for detailed power settings.

(They go on to talk about geared engines and turbocharged/supercharged engines, but your question was about normally-aspirated engines. This is from Lycoming Flyer "Key Reprints" - I grabbed it here but you can Google it up pretty easily, and I imagine Continental has analogous guidance somewhere.)


The original 757 cockpit was considered “glass.” It consisted of six screens: Pilot’s PFD and ND, Co-pilots PFD and ND, and an upper and lower EICAS screen.

Behind the scenes, there is a triple autopilot system (left, center and right), two flight management computers, three flight control computers, three display control units (think SGU or symbol generator), two to three air data computers depending on customer option, and two EICAS (Engine Indicating and Caution and Advisory System) computers. There are also a large number of card files that process various system discretes to provide aural warnings.

A more modern upgrade to this, called “IS&S” keeps the same “boxes” in the shelves, but changes the PFD/ND displays to 4 LCD displays. This also got rid of the standalone airspeed indicators and altimeters (save the standby) as well as VSI’s. It makes the aircraft “NextGen” compliant.


What are the contributors of lift-dependent drag?

If someone wants to plot the drag polar of an aircraft, we have
$CD=CD_o+CD_i$
form/skin drag plus the induced.

Something to note here is that there are more than one mathematical "model" to describe the relationship between lift and drag. What you have described is known as "Parabolic Drag Model", where we consider a parabolic relationship between lift and drag.

Does that increment in parasite drag considered in the induced drag term because it's lift-dependent?

Imagine an airfoil drag polar (2D polar so there is no induced drag taken into account). If this polar can be closely modelled as a skewed parabola (skewed due to camber) then $e$ in the induced drag term $\frac{CL^2}{\pi*e*AR}$ takes care of this drag rise up to some extent. This kind of a 2D airfoil drag model is usually applicable for mostly turbulent airfoils such as NACA 4 series in high Reynolds number flows.

Where should we add this contribution of drag in terms of the drag polar formula? in the lift-independent part or in the lift-dependent part?

Above said, mostly laminar airfoils such as FX163 or NLF series airfoils which operate in relatively low Reynolds numbers does not fit the above model fairly well. These airfoils exhibit a linear relationship between lift and drag at-least for the operating range which is not affected by massive separation. So in this kind a scenario its best to modify the above equation with a linear term as well.

$CD=CD_o + k CL + \frac{CL^2}{\pi e AR}$


A monitored approach is a special kind of instrument approach involving added verbal call outs and increased monitoring of the airplane and is typically conducted when weather is below a certain threshold. For example, a crew may be required to fly a monitored approach if the weather is below 3/4 mile vis and the captain has less than 100 hours in type, or in any case with the weather below ILS Category I minimums. It is also specific to multi-crew aircraft and requires at least 2 pilots and in many cases an autopilot.

In a crew environment, the pilots are typically designated as Pilot Flying (PF) and Pilot Not Flying (PNF).  In general the PF is flying and making commands of the PNF, and the PNF mans the radios and operates gear and flaps the command of the PF.  More detail of this setup probably deserves its own question.

To illustrate a monitored approach, I'll describe on based on my companies procedures.  The specific requirements can vary between operators based on crew training, aircraft equipment and approved opspecs.

The monitored approach briefing

We have identified the arrival airport current weather is 1200 RVR and obscured ceilings and we plan to fly the ILS to category II minimums.  Myself and my first officer have both have current category 2 training, neither of us are high-minimums, and the aircraft has no MEL items effecting category 2 operations.  We are legal to fly the approach, but company operations require we fly it as a monitored approach.

Regardless of who has been PF and PNF up to this point, the first officer becomes the PF and the captain the PNF.  The PF briefs the approach as normal except for:

CAT II radar altitude minimums
Low vis taxi routes if applicable
The approach will be flown by the autopilot (company specific)
Special autopilot considerations
Required verbal call outs (see below)

The monitored approach

For my company, the autopilot had to be engaged in "CAT 2" mode before glideslope intercept.  This will vary by aircraft and company.  For the approach, as noted earlier, the first officer is PF, captain is PNF.

The PF duties are to monitor the autopilot and to execute the missed approach if the autopilot has problems.  The PNF also monitors the autopilot.  The pilots are monitoring the autopilot for performance and for indications it cannot meet required tolerances for the approach.

PF will call for gear and flaps as normal, except a non standard flap setting may be used for the approach (e.g. we flew flaps 22 instead of 45).

Once configured for landing, the PF will call for "Landing checklist - to the line" (company specific), this for us was the normal landing checklist with the caveat that the checklist is complete when the captain announces "Landing, I have the airplane" (more on this in a moment).

Nearing the Cat II decision height (typically 100 ft RA), the PNF will announce "Going heads up", discontinue monitoring the autopilot and look for the approach lighting system and the runway lights.

The PF will continue to monitor the autopilot.

The airplane will announce "Minimums" at the radar altitude DH and when the airplane reaches this height, the PNF will fly the missed approach.

If the captain sees the required lighting to continue the approach, they will announce "Landing, I have the airplane", and the FO will reply "you have the airplane, landing checklist complete.

The Captain must disconnect the autopilot (by 50 feet, no autoland for us), and would fly any aborted landing executed after taking control.

Caveats

Rules on autopilot usage, disconnect heights and autolanding will vary based on aircraft and company policies.  My example assumes an Embraer-145 certified for Cat 2 approaches and no autothrottles or autoland capability.  Checklist verbiage and flap configurations mentioned also would vary by aircraft and company.  And finally, the specific callouts will vary by company.

While it seems like there was a lot of Category II specific things in my example, the two concepts of reduced visibility ILS approaches and monitored approaches are intertwined, and you will almost always be flying a monitored approach because it is required to conduct the low weather approach by company policy.


Is it normal practice to refuel commerical planes whilst boarding is taking place?

Refueling with passengers onboard is quite normal and is done according to the recommendations of regulatory bodies/manufacturers and operators. Refueling with some fuel types are not permitted, while others are. From Airbus Flight Operations Briefing notes:

Refueling  with  wide  cut  gasoline  type  fuel (JET  B,  JP4  or  equivalent)  or  when  a  mixture  with  these  types  of  fuel  might  occur,  is  not  permitted  with  passengers  boarding, on board or disembarking.
Refueling with Kerosene (JET A, JET A1 JP8, TS1, RT, TH or equivalent, as approved by  the  approved  Aircraft  Flight  Manual),  is  allowed  when  passengers  are  boarding,  on board, or disembarking.

Some precautions are required to be followed in case refueling is done with passengers on board. The announcement you heard is simply following that. From Appendix 1 to JAR-OPS 1.305 Refuelling/defuelling with passengers
embarking, on board or disembarking:

(a)   An  operator  must  establish  operational procedures   for   e/defuelling   with   passengers embarking,  on  board  or  disembarking  o  ensure  the following precautions are taken:
(1)   One qualified person must remain at a specified location during fuelling operations with passengers  n  board.  This  qualified  person  must be  capable  of  handling  emergency  procedures concerning  fire  protection  and  fire-fighting, handling  communications  and  initiating  and directing an evacuation;
(2) A  two-way  communication  shall  be established  and  shall  remain  available  by  the aeroplane’s  inter-communication  system  or  other suitable   means   between   the   ground   crew supervising  the  refuelling  and  the  qualified personnel on board the aeroplane;
(3)  Crew,  staff  and  passengers  must  be warned that re/defuelling will take place;
(4)  Fasten eat Belts’ signs must be off;
(5)  ‘NO  SMOKING’  signs  must  be  on, together   with   interior   lighting   to   enable emergency exits to be identified;
(6)  Passengers  must  be  instructed  to unfasten  their  seat  belts  and  refrain  from smoking;
(7)  Sufficient qualified personnel must e on  board  and  be  prepared  for  an  immediate emergency evacuation;
(8)  If  the  presence  of  fuel  vapour  is detected inside the aeroplane, or any other hazard arises  during  re/defuelling,  fuelling  must  be stopped immediately;
(9)  The  ground  area  beneath  the  exits intended  or  emergency  evacuation  and  slide deployment areas must be kept clear; and
(10) Provision is made for a safe and rapid evacuation.

You're right about the announcement and leaving seat belt open- it is to help in quick evacuation. The flight crew is just following the procedure.


How can one approximately guesstimate wave drag?

Usually wave drag $c_{d_w}$ starts becoming relevant at the drag divergence Mach number $M_{DD}$, which is defined as

$$\frac{\partial c_{d_w}}{ \partial M}_{M=M_{DD}}=0.1 \tag{1}$$

Or in words, the Mach number at which the wave drag coefficient versus M has a gradient of 0.1

Lock$^1$ has derived an empirical formula that shows the development of $c_{d_w}$ after the critical Mach number, $M_{cr}$, which is the number at which the flow becomes locally supersonic on the wing:

$$c_{d_w} = 20(M-M_{cr})^4 \tag{2}$$

If we apply the definition of $(1)$ to $(2)$ we obtain:

$$M_{cr} = M_{DD} - \left(\frac{0.1}{80}\right)^{1/3} \tag{3}$$

As you can see, the value of $M_{DD}$, is a little bit higher than the value of $M_{cr}$. First you get local super sonic flow, but the drag does not increase rapidly, as you further increase the Mach number, the drag starts to increase significantly, and you reach $M_{DD}$. See this image, where $M_{DD}$ is denoted by $M_{CDR}$.

Source

The value of $M_{DD}$ can be estimated using:

$$ M_{DD} = \frac{K_A}{cos \Lambda} + \frac{t/c}{cos^2 \Lambda} +\frac{c_l}{cos ^3\Lambda} \tag{4}$$

With $\Lambda$ is the sweep angle, $t/c$ the relative thickness, $c_l$ the lift coefficient, and $K_A$ the airfoil technology factor (a correction factor denoting the quality of the airfoil).

So the workflow is as follows:

Estimate $M_{DD}$ using $(4)$
Derive $M_{cr}$ using $(3)$
Determine the development of $c_{d_w}$ using $(2)$.

For more info, see this link and this link

$^1$ Hilton, W.F., High Speed Aerodynamics, Longmans, Green & Co., London, 1952, pp. 47-49

Note, this method is only for estimating the wave drag coefficient around the drag divergence Mach number, I'm not sure to what Mach number it provides an accurate estimate


What scientific evidence is there about the effectiveness of pre-flight walk-arounds?

First off you are required by the FAR's to preform a preflight check,

  Sec. 91.7

  Civil aircraft airworthiness.

  (a) No person may operate a civil aircraft unless it is in an airworthy condition.

  (b) The pilot in command of a civil aircraft is responsible for
  determining whether that aircraft is in condition for safe flight. The
  pilot in command shall discontinue the flight when unairworthy
  mechanical, electrical, or structural conditions occur.

Don't forget the Preflight is also about making sure the aircraft is legally airworthy (VFR or IFR minimum equipment) as well as being physically airworthy.

Here is a brief from the FAA on the matter. It has at least one example of an accident that occurred as a result of a bad preflight. According to this Flying Magazine Article 15 accidents have been the result of a bad preflight in the past 10 years (from the publish date of that article). Here is another example as well. Clearly it has lead to accidents in the past but you may have an issue finding any data on times that it has found things and potentially saved lives (as that is often not reported to anyone but the mechanic).

Nasa conducted a study on checklist usage (preflight included) which is along the lines of what you may be looking for.

Here is another FAA article on preflights and has some more specific stats on what you are looking for.

  Consider this: NTSB aviation accident data show that in the last 10
  years, poor preflight inspections caused or contributed to 156 general
  aviation accidents and resulted in 41 fatalities.

You can compare that to the total number of other GA accidents for an approximation of how important it is in causing a crash. of When it comes to the FAA a great deal of analysis is carried out on accident data not necessarily preemptively. One of the other analysis issues here as mentioned in the comments is much of the reasons that planes get grounded does not get reported to any official authority (aside from the mechanic) so the data may not be public or easily accessible.

If we include preflight checklists and walk arounds in the same category. Following the Northwest 255 accident that was the result of misunderstanding/misusing pre-flight checklists the NTSB did do a study on preflight (and all checklist) procedures. You can find the study and results report here which includes some stats.

  This idea seems more plausible when I speak to more experienced pilots
  of the same type, and each of them warns me about checking one thing
  in particular that's not on the checklist, because they once saw an
  accident that was caused by a failure there - and crucially, each of
  them warns me of a different thing.

This may be more a case of correlation over causation. If you are involved in aviation long enough (especially the older generation that has flown when laws and planes were much different) you see lots of things. Some of the issues they talk about may have been covered by AD's since they encountered them (if you are flying a common airframe like a 172 or PA-28).

As for not finding stuff this will come with how well you know your plane. As you start to fly the plane more and more (you should be training in one plane or at least only one type of plane). Eventually you will begin to know whats where, the POH can help with that, and you will be able to recognize if something is out of place.

I can speak from personal experience that I have delayed many flights due to things I have found on the preflight. I had a cracked cowling bracket, countless low gear struts that needed air, many fuel calls in the rental planes, a fuel vent issue, and one breaks issue.

Of course you will always have human factors present in manned flight.


For what program was this Cessna 182 fitted with canards?

It's a King Katmai STOL mod for a Cessna 182. From https://www.avweb.com/ownership/king-katmai-mod-safe-stol/

The full King Katmai modification consists of the canard, 300-HP IO-550, choice of 82- or 86-inch, three-blade prop, speed mods/drag reduction fairings, wing extension, increased gross weight, heavy-duty landing gear, which includes Cleveland brakes, stainless steel leading edges on the gear legs, brake lines faired in behind the main gear legs and routed so they are unlikely to be snagged during rough field operations, heavy-duty Airglas nose strut and oversize tires.

It brings the stall speed down to 31 knots. 3100 lb gross weight takeoff distance of 290 feet from a hard surface runway.


Which of these is true for a glider flying with constant angle of attack?

Two things are important here:

It is about a glider, so no fuel is consumed, and the mass is constant over time.
The angle of attack is constant. This means also that the lift and drag coefficients are constant.

If the mass and the lift coefficient are constant, and we assume a constant load factor (implied by the gliding along its path description), the dynamic pressure is also constant, and the airspeed changes with the square root of air density. Gliding implies that the altitude decreases, so the indicated speed will be constant, but the true speed will decrease. Unfortunately, the condition e) is not precise enough to make this distinction. e) could be correct or not, depending on the definition of V.

I would suggest that also c) could be a correct answer: If the angle of attack and the mass are constant, so should be the drag coefficient. However, gliding down also implies that the Reynolds number changes because true speed decreases and temperature increases over the glide. Strictly speaking, this would also mean a very slowly changing drag coefficient.

Answers b) and d) are false and I agree with your reasoning.


Are there two types of runway holding position sign?

I’ve never seen the critical area hold bars referred to as a type of runway hold bars, but they serve the same general purpose when the critical area needs to be protected, so I can understand the point of describing them together.


Do modern Terrain awareness and warning system (TAWS) have blind spots?

This answer is only applicable to civil airline type operations. Military systems do have significantly different requirements which I cannot address.

Quick Answer:

No, they don't have "blind spots" in the sense of areas with no data available.

A TAWS system works differently:

In the airline I've worked for, I was "exposed" to Honeywell Mark V EGPWS systems, but I assume that other systems are similar. These systems have a world-wide terrain database. That database and the algorithms take a normal terrain clearance into account as well as the performance of the aircraft.

"Holes" or "Corridors" are "cut" into this "terrain clearance carpet" to avoid nuisance warnings when an aircraft needs to descent below the normal margins. I.e. during landing and takeoff.

So, these aircraft can safely operate world-wide unless there are new mountains growing (which actually happens with volcanos) or large man-made obstacles are built.

As with all databases on board of an aircraft, they are updated on a regular basis.

Except for this link, I was not able to find an awful lot of information from manufacturers.


What is the cause of tire marks at the extreme ends of runways?

The marks are left by the tires of landing planes when they touch down -- that is, ordinary routine landings.

The wheels of a landing aircraft do not start rotating before they hit the runway -- so right at the moment of touchdown, the wheels will at first skid along the runway surface until the friction between tires and runway has delivered enough angular momentum to the tire to spin it up so it matches the ground speed of the landing plane. Once that happens, the wheel will roll normally.

This skidding causes the skid marks you have observed.

Even if the runway is usually used in the east-to-west direction, there are still enough days where landings are from the west that both ends of the runway will collect tire marks. How many days that are doesn't really influence how black the runway gets, only how long it can go between having the rubber buildup cleaned off.

At the few airports that are really only used in one direction (such as the famous Princess Juliana Intl Airport at St. Maarten, which does not even have charted approaches from the east due to terrain obstacles) you will find the tire marks only at the touchdown end of the runway.


If the map (reading) light bulb is burned out in my own Cessna 210, what are my options if I want to fly FAR Part 91 under night-time VFR?

As the owner, you (likely) may replace the bulb yourself
It comes down to the complexity of the work.
Owners can now do far more preventive maintenance than the 32 listed items
For many years, the FAA treated the 32-item list in 14 CFR Appendix A to Part 43 as exhaustive. The interpretation was that if an item or procedure did not appear in section (c), then it was not preventive maintenance. Case closed
However, in 2009 the Coleal Legal Interpretation, produced by the FAA's Office of Chief Counsel, superseded the prior rules. It specifically calls out and contradicts the understanding that the 32-item list is exhaustive.

Even though the introductory text of subparagraph (c) states that “[p]reventive maintenance is limited to the following work ....” (emphasis added), in view of the broader definition of preventive maintenance in section 1.1, we believe that such limitation is not controlling. Similarly, for the same reason, we also believe that the following sentence in Advisory Circular 43-12A … is overly restrictive. That sentence, found in Paragraph 3(b)(1), states: “If a task or maintenance function does not appear in the list, it is not preventive maintenance.” As with the other paragraphs of Appendix A (i.e., on major repairs and major alterations), the lists are better viewed as examples of the tasks in each category – they cannot be considered all-inclusive. There are, no doubt, many “simple or minor preservation operations [tasks]” and many “replacement[s] of small standard parts not involving complex assembly operations” performed daily, especially on small general aviation aircraft that the agency would consider to be preventive maintenance, though they are not included in the 32 listed items. It is our understanding that Flight Standards' Aircraft Maintenance Division is planning to clarify this issue in a future revision to the AC.

In short, the list of 32 items is not exhaustive.
Is the map light preventive maintenance?
So we know that there is preventive maintenance which can be done which does not fall on the list. However, this does not imply that all maintenance is preventive. The specific question has to do with the map light.
Looking through 14 CFR Appendix A to Part 43, we find:

(c)(17) Replacing bulbs, reflectors, and lenses of position and landing lights.

So it is clearly within the domain to replace exterior bulbs. The question becomes whether accessing the interior map light bulb in a Cessna 210 is low complexity or high complexity.
Your A&P might be able to give you some guidance, although IMHO a good yardstick is that any part designed to be IRAN'ed with nothing more than a Swiss-army knife is pretty clearly "low complexity" and should fall under owner preventive maintenance.


Where can I learn more about pilots' dreams during G-LOC?

I'm not sure if you've come across this or not, but the paper Recovery from
Gz-lnduced Loss of Consciousness:Psychophysiologic Considerations has some details on this phenomenon. It describes the tests carried out on eight volunteers.

This does not appear to be very common- five 'dreams' were recalled out of 21 acceleration runs. The subjects seem to have indicated that these were definitely 'dreams' as opposed to 'thoughts'. Also, the report notes:

  ... it is difficult objectively to determine exactly what the subjects experienced during their individual G-LOC episodes (dream or thought) or even state that G-LOC can be equated to a normal sleep mental state (in relation to dream activity)

Another paper Further Support for the  Concept of a  G-LOC Syndrome: A Survey of Military High-Performance Aviators shows that the dream-like state occurs in about 15% of the cases.

The 'dream' state appears to be restricted to <13s and vary from person to person (in some cases, they were not aware that they've lost conciousness).


Are there any airports whose budgets are in the public domain?

This varies heavily by country but I can answer this for the United States operating under the FAA/General US legislation (which varies by city).

Here in the US some airports are owned by the local government (there are also privately owned/publicly used and fully privately owned airports). Publicly owned airports (owned by cities/towns/localities etc.) generally either publish their budgets or you can obtain them if you request it. For example if you want to see the information for KPNE or KPHL (owned by the city of Philadelphia) you can submit a form to the city and request the information. Every city is a bit different and there may be small processing fees/long wait times but generally the records can be obtained.

The FAA also published a lengthy brief on the cost-benifit analysis of having an airport in your area. It sheds light on some common costs and such.

Keep in mind that the airport while owned by the city and operated by the city, often has many private companies on its premises that simply lease a building or plot of land. The budgets to operate these FBO's, service centers and the such are more than likely private information.


The blades are loose in their "Fir Tree" blade mounts so that they can self balance. They are called "fir tree" because they are v shaped.

As the rotation speed and centrifugal force increases, they move in the mounts and establish individual lead/lag positions to achieve a balanced disc.

  It will be understood that turbine wheels rotate at very high speeds
  of rotation, thereby generating large centirfugal forces tending to
  throw the blades outwardly from the wheel. By providing contact
  surfaces of equal and opposite slope with respect to the longitudinal
  axis of the root on opposite sides of root, the force components of
  the centrifugal force balance each other out. Periodic and other
  vibrations which might otherwise be generated are damped out and
  greatly minimized

Source: Fir tree blade mount Patent


What is the maximum Mach number for a titanium aircraft?

To give an answer, I first need to get answers to a few more questions:

First question: Which titanium alloy would you consider? The choice of alloy will impact the answer much more than the base metal of the selected alloy. Since strength at elevated temperature is the figure of merit here, consider the spread of values:

Strength of various Ti alloys over temperature (picture source)

Second question: Which cooling is available? Is the aircraft propelled by liquid hydrogen which has a massive heat capacity per kilogram of mass and needs to be heated before it is injected into the combustion chamber. Or do you run it on kerosene, which allows to dump much less heat into it? The answer will tell you how much cooler the structure can be than the air flowing around it is.

Third question: What wing loading is possible? This is driven by the range and payload requirements of the aircraft, and your question doesn't give any details on this. A higher wing loading will translate into a higher heat flow since the air density needs to be higher, so the cooling can be less effective.

Fourth question: Do you insist on an attached shock which produces much higher peak temperatures in parts of the structure, but less thermal load overall, or is a separated shock possible which increases drag and thermal load, but reduces peak loads considerably?

Depending on the answers to those questions, the possible flight Mach number can be anywhere between Mach 2 and Mach 5. If you allow for specialty materials for highest thermal loads and make only the inner structure from titanium, the Mach number can reach into double digits.


Thats a Bede BD-5 a microjet famously flown by James Bond. Based on the tail that may be the propeller variant.

(source)


Navigate to the final approach course after radio failure under IFR

First, squawk 7600 to let ATC know you have lost two way radio communications and to clear traffic out of your way.

Then, from the AIM, Section 4. Two-way Radio Communication Failure

Section 6-4-1.c. includes:

  1. General. Unless otherwise authorized by ATC, each pilot who has two-way radio communications failure when operating under IFR must comply with the rules of this section.

and

  2. VFR conditions. If the failure occurs in VFR conditions, or if VFR conditions are encountered after the failure, each pilot must continue the flight under VFR and land as soon as practicable.

This is the preferable solution, but the question said to assume the conditions are IFR. Which leads to (displaying only applicable sections):

  3. IFR conditions. If the failure occurs in IFR conditions, or if subparagraph 2 above cannot be complied with, each pilot must continue the flight according to the following:

  (a) Route.
   ...
  (2) If being radar vectored, by the direct route from the point
  of radio failure to the fix, route, or airway specified in the vector
  clearance;

  (c) Leave clearance limit.

  (1) When the clearance limit is a fix from which an approach begins,
  commence descent or descent and approach as close as possible to the
  expect further clearance time if one has been received, or if one has
  not been received, as close as possible to the Estimated Time of
  Arrival (ETA) as calculated from the filed or amended (with ATC)
  Estimated Time En Route (ETE).

So the expectation of ATC would be that the crew would fly outbound, make a right turn and intercept the localizer and fly the approach.

It would be a challenge to fly it without DME, but not impossible from the starting point. Radar or DME (or GPS) is needed to get to the IAF. If the pilot had a good estimate of his location when comm was lost, it would be to fly outbound for about 1 minute and then a right 180 deg turn to intercept the localizer. Once the glideslope is intercepted, being on GS plus altitude allows to to estimate passage of TIMSE and FUMBL. The rest of the approach can be timed.


What does 'intercept final' exactly mean?

You are correct. The verb intercept, as used by ATC and pilots means to track to and then turn onto a given course. In your given example, "vector to intercept the final approach course", a vector to intercept is a vector which will cross the final approach course and from which the pilot will be able to commence a turn to become established on the final approach course. To intercept the final approach course means to accomplish that turn onto the final approach course.

See this additional example from an excerpt from Section 4 of the Aeronautical Information Manual (AIM)

  5-4-3. b. 1.

  (c) The pilot is not expected to turn inbound on the final approach
  course unless an approach clearance has been issued. This clearance
  will normally be issued with the final vector for interception of
  the final approach course, and the vector will be such as to enable
  the pilot to establish the aircraft on the final approach course prior
  to reaching the final approach fix.


How is the drift corrected in INS-driven attitude/heading indicators?

Inertial navigation systems do not need to correct for drift.

Modern optical gyroscopes drift about 0.001°/h and even the mechanical ones used aboard the apollo spacecraft back in 1969 achieved 0.03°/h (see Apollo 8 Mission Report, page 119). After a 20h-flight with those mechanical gyros, accumulated drift would be 0.6° and therefore less than the error of a self-erecting, ordinary attitude indicator during a turn.

The reason ordinary attitude indicators need an erection mechanism is not that they are imprecise, it is because earth turns and the aircraft moves.

Earth turns at a rate of 15°/h at the equator and 0°/h at the poles. The attitude indicator must adapt to the unknown drift unless it knows its latitude, in which case the drift is also known.
Aircraft travel considerable distances. The local horizon in Cape Town (34°S) differs from the local horizon in Berlin (52°N) by 86°. An attitude indicator must correct for these changes as well, unless it knows it just travelled from Cape Town to Berlin.

Inertial navigation systems do not suffer from these issues. They know their position, the route they travelled and how long they've been flying. They just leave the gyroscopes as is and apply corrections to the display only.


Where is the F-4 Phantom II's flap lever?

(flickr.com)

On a real F-4 it's the flap-shaped switch on the left console aft and left of the thrust levers. Also here is the cockpit items poster (see item no. 5 on the left).


Why would a cylinder not work below a certain RPM?

Well, if it is cold and cht and egt are zero then I you're either not getting spark or fuel or air.

It's possible that the spark plugs are not firing.  Clean and bench test them.  Also check that the mags are timed correctly.   Maybe they work but they just fire at the wrong time.

Make sure the valve train is assembled correctly.  When you installed the cylinder, did the lifters and rods get put back correctly.  Also, are the rockers installed correctly.  I know this sounds like a stupid thing, but sometimes people make errors.

Maybe you have a stuck or broken valve.  You typically notice when this happens though!  Also, if it works at some RPM and not others, this is probably not the issue.

Finally, have your A&P follow Lycoming's fuel system calibration procedure to the letter (you'll need to look this up; TCM's is SID 97-3).  I had a TCM IO-520 on a V35B for a few years and when we calibrated the system we saw a noticable improvement in engine performance.

Of course, check the compressions!  If you're 0/80 then you may have your answer right there.

These are just a few thoughts and it's by no means a comprehensive list of possible causes.


All these clouds signal an approaching warm front and potentially a storm.  Warmer, moisture laden air rides over the top of cooler air, forming visible clouds while the ground level front is still many miles away.

Cirrus clouds are composed of ice crystals and form at very high altitudes.  They are the first of the approaching clouds.  Cirrostratus form as more moisture arrives and the front gets closer, followed by status.

Cirrus clouds, being the highest and first to arrive, are stratiform.
Cirrostratus are observed as broken cirrus/blue sky becomes overcast.

Cirrocumulus clouds are the result of high altitude convection and contain supercooled water.  They can transform into status clouds, and are also associated with approaching weather.  The vertical motion that creates cirrocumulus seems to be more of a transient local phenomena, such as turbulence.


Is it possible to calculating sea-level pressure with an unknown base station altitude?

Calculating sea level pressure depends on knowing your altitude.  A function that does this is the hypsometric equation $$\Delta z = \dfrac{R \overline{T}}{g}\ln\dfrac{p_1}{p_2}.$$  This function gives the depth ($\Delta z$) of an atomspheric layer with average temperature $\overline{T}$ between pressure levels $p_1$ and $p_2$.  In your case, the station pressure is known and the height of mean sea level is known; in order to calculate your height or to calculate sea level pressure, you must know the other quantity.  The average temperature is also an unknown, but you can approximate this or use a value based on the lapse rate of the standard atmosphere.


Are there more accidents in winter months, and if so, why?

I'd argue fall and spring bring more unpredictable weather, and slippery runways are year-round in the tropics.

That being said, for all jet (commercial) accidents, the weather-related contributing threats are:

Meteorology (e.g., failure to identify threats before a flight) 30%

Windy conditions 16%
Poor visibility 10%
Thunderstorms 9%
Icing 1%

Poor braking action (e.g., slippery runways) 10% (falls under airport facilities, not meteorology)

All figures are from PDF page 172 of the IATA 2017 Safety Report.

Given the opening statement, [near ground] icing is more attributable to cold winters than the rest. The rest are not limited to Dec–Mar in the Northern Hemisphere. The report does not attribute the seasons to the accidents.


What is the difference between the various automated airport weather observing systems?

ASOS is basically a replacement for AWOS with more reporting parameters, and the first units were installed in 1991.  According to the Automated airport weather station Wikipedia page, each different type has the following parameters:

AWOS

  AWOS A: barometric pressure and altimeter setting (in inches of    Mercury).
  AWOS I: wind speed and wind gusts (in knots), wind    direction (from which the wind is blowing) and variable wind    direction (in
  degrees of the compass), temperature and dew point (in    degrees
  Celsius), altimeter setting and density altitude.
  AWOS II:    all AWOS I parameters, plus visibility and variable visibility (in    miles).
  AWOS III: all AWOS II parameters, plus sky condition (in    oktas), cloud ceiling height (in feet), and liquid precipitation
  accumulation (in inches).
  AWOS III P: all AWOS III parameters, plus    precipitation type (rain, snow and sometimes drizzle) identification.
  AWOS III T: all AWOS III parameters, plus thunderstorm detection (via    a cloud-to-ground lightning detector).
  AWOS III P/T: all AWOS III    parameters, plus precipitation type identification and thunderstorm    detection.
  AWOS IV Z: all AWOS III P/T parameters, plus freezing rain    detection via a freezing rain sensor (Note: this configuration used
  to be called AWOS III PTZ).
  AWOS IV R: all AWOS III P/T parameters,    plus runway surface condition.
  AWOS IV Z/R: all AWOS III P/T    parameters, plus freezing rain detection and runway surface    condition.

ASOS

  They generally report all the parameters of the AWOS-III, while also
  having the additional capabilities of reporting temperature and dew
  point in degrees Fahrenheit, present weather, icing, lightning, sea
  level pressure and precipitation accumulation.


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


Do landing strips suffer from potholes or rutting?

Yes, they do, and it can indeed pose significant problems for aircraft.

Asphalt runways are susceptible to ruts (because asphalt isn't really solid - it's solid aggregate suspended in an extremely viscous liquid). The friction (heat) from landings partially melts the asphalt, and the weight of the aircraft slowly pushes it outward away from the landing gear, creating ruts. (There are also other ways you can cause ruts on asphalt runways, such as landing overweight aircraft on them on extremely hot days).
Concrete runways are theoretically less susceptible to rutting, but have their own maintenance challenges.

Runways can also develop potholes, cracks, and spalling - just like a road surface.
Because a pothole can cause loss of control on landing (if the landing gear falls into it and blows a tire or yanks the plane to one side), or serious damage to aircraft engines (if some of the material ejected from the pothole gets pulled into a jet engine's intake or kicked up by a propeller) airports take a lot of effort to prevent (and where necessary, repair) this kind of damage, and routinely inspect their runways.

Airports also do a lot of preventative maintenance on their runways, sealing open cracks and joints in the pavement material to prevent water from infiltrating under the runway and causing potholes (see the image below - click to enlarge).

The FAA has a lot of information on runway pavement design, which I will affectionately call "More than anyone ever wanted to know about runway design, and never asked!"


What API can I use to get FAA NOTAMS or will this one I found work?

As @GdD mentioned in the comments, there is an API for NOTAMs here: https://www.icao.int/safety/iStars/Pages/notams.aspx

You also asked for metars, which you can get from here:
http://tgftp.nws.noaa.gov/data/observations/metar/cycles/${TIME}Z.TXT where ${TIME} is the hour of the Zulu time you are interest in, wrapped between 0 and 23 (eg. 16)


Has a jet "engine" ever been made that only uses the thrust from the bypass air and doesn't have a combustion chamber?

Well what you are describing is a ducted fan.  They are common on RC aircraft with the fan driven by either a gasoline engine or electric motor.

On large scale applications like an airliner, you have to find a source of power for the fan that is 1) compact 2) light weight 3) delivers a very high specific power and 4) draws energy from a reservoir with a high energy density, all while remaining 5) extremely reliable and 6) safe.  For these kinds of applications, you really can’t currently do better for this than use a kerosene fueled gas turbine engine to drive the fan.  And that's all a high bypass turbofan really is - just a gas turbine powered ducted fan.


Do quadcopter propellers break the sound barrier?

Almost certainly not. Given the comments specifying a $0.5$ inch radius (blade length,) that means the circumference of the path of the blade tips would then be

$$2 \pi \cdot 0.5 \, \text{inches} \approx 3.1415 \, \text{inches} \approx 0.2618 \,\text{feet}$$

To get to the speed of sound (which is approximately $1,126 \,\frac{\text{ft}}{\text{s}}$ at sea level,) that means you'd need to have the fan spinning at

$$\frac{1,126}{0.2618} \approx 4,301 \,\text{Hz} \approx 258,060 \,\text{rpm}$$

Needless to say, that's not happening unless you have one seriously expensive quadcopter.

The buzzing you hear is probably either the frequency at which the motor is spinning or, perhaps, the frequency of some oscillation of the fan blades. Most likely, though, it's just the frequency of the motor/fan.


Missing shear pin for tow-bar / front landing gear

The Capt would have just repeated or paraphrased whatever Maintenance Control told him.  If a push back is done with the nose wheel scissors connected, it is critical for the tug driver to respect the steering angle limits of the nosewheel to avoid bottoming the steering actuators and stressing the parts.

Although the shear pin protects (hopefully) from major damage it still puts significant loads on the scissors and nosewheel steering system, beyond what those components would normally see.   If they find the towbar shear pin damaged or loose or sheared completely (although that should have been obvious while connected) after a push back, Maintenance will have to assume there was a steering angle exceedence event and there is likely to be a maintenance requirement to inspect the steering system, hence the return to gate.

My guess is that when the tug got back to the gate, someone noticed the pin was deformed, or some other abnormality, and they brought the airplane back for the inspection to play it safe.


What is the explanation of this airfoil phenomenon? Why the air from below the leading edge's tip deflected up?

The short answer is: because not all of the incoming air can fit under the airfoil, so some of it gets pushed up and above the leading edge. This air could also fit under the airfoil by other means like becoming denser (compressing), but that requires more energy, so it mostly flows around.

In your image, the effect is exaggerated by the closeness of the ground, which places the entire airfoil in ground effect. In normal flight conditions, without the ground blocking it, more air would be able to flow underneath the airfoil.

The longer answer has to do with the speed of sound, which is the speed at which pressure waves propagate through a fluid. If the free stream is subsonic, pressure waves generated by an object can flow upstream and alter the flow ahead of any disturbance.

This is exactly what is happening here: the airfoil is affecting the pressure field, specifically by creating an area of high pressure underneath. This affects the incoming flow, deflecting it upwards ahead of the airfoil.

If this experiment were performed in supersonic conditions, you would not see any disturbance in the incoming airflow until it hit the bow shock wave of the object, after which it would become locally subsonic and be abruptly deflected to flow around the airfoil.


Is there any part of a flight where the pilot would pitch down?

The most common case to pitch down is to speed up, not to reduce altitude, for example when transitioning from a climb (at climb speed) to level flight (accelerating to cruise speed). You can transition to level flight by reducing thrust, but that'll leave you level at climb speed, and is usually not what you want.

Changing configuration will usually require pitching changes to maintain stable flight. In particular during the approach-to-landing, extending the flaps will substantially increase the drag, and in order to maintain airspeed, you'll need to pitch the nose down. If you don't, you'll bleed off airspeed and potentially eventually stall unless you overpower the drag with thrust.

There are of course unusual circumstances that will require a pitch-down as well, obstacle avoidance for example (e.g. airplanes). As mentioned in the comments, to make a speedy descent you'll probably also want to pitch down (such as in case of pressurization problems or fire on board).


How to maximize your practical lift/weight ratio in a multirotor?

To maximize lift, use the most powerful motors and let them turn the propellers at the highest possible speed. To minimize weight, make the structure as light as possible (use round carbon fiber/epoxy tubes instead of square aluminium ones, for example) and use only as much batteries as needed to achieve lift-off.

I would expect that there should be some more rules to ensure that the winning entry is actually useable. You did not mention any of this. Now efficiency comes into play, and the number of parameters to watch goes up. A lot.

Make sure that your propellers act on as much air volume as possible. Let them run at a reduced speed for better efficiency. You need to test your particular engine-propeller combination where the sweet point is - there is no general number for best efficiency.
Put as little drag in the way of the airstream as possible. This requires careful study of all shapes and cross sections. See on the right side of the picture below for a general overview of the drag coefficient of different 2D shapes.

Figure 33 from Sighard Hoerner's Fluid Dynamic Drag, Chapter 3.

As you can see, round is better than square. However, depending on the local Reynold number, it can help to add turbulators or local roughness to trip the boundary layer.

Also, adding motors to one arm will reduce the efficiency and thrust of the second propeller. Your 8 motors / 4 arm design will end in a disappointment - you cannot simply add the thrust of an individual motor-propeller combination once they interfere with another unit.

Without detailed knowledge of the rules of your competition, it is hard to give more detailed advice. I expect that a lot of educated trial and error will produce the best outcome.


Does ground clutter exist over the ocean?

Yes, ground clutter does exist over the ocean. It depends on the smoothness of the water surface, radio frequency, antenna characteristics and atmospheric properties whether the radar will actually receive reflections from the sea surface.

A perfectly smooth sea surface will not generate clutter, but the combination of small waves and a strong inversion layer (temperature getting higher with altitude) will cause ground reflections, even for surface based radars looking above the horizon. The inversion layer will cause super refraction - the radio wave bends towards the ground / sea - and will cause a reflection off the waves which is received by the radar.

In an extreme inversion layer a so called atmospheric duct may form in which the radio signal makes multiple bounces of the sea. At each bounce part of the energy is reflected, resulting in multiple ground clutters at regular distance intervals.

Ground clutter is not always perceived as a problem. In some cases its absence may help to identify objects of interest. For example, in weather radar the absence of ground clutter behind a cloud indicates that the cloud has absorbed all the radio energy which is an indication of its severity.

source: Airbus Flight Operations Briefing Notes, Adverse Weather Operations (PDF)


Do airline pilots get to go home often to see their family and have a break from flying planes. If so, how many days?

All in the contract, routes, and choices of the pilot within that contract. Some fly trips of up to two weeks, others are back home every night if they have a home near their base airport and work regional. Some choose to take all available work offered while others stay near the minimum.

Labor law limits total flying time per day and per week depending on crew size and time of the day.


Can I simply use multiple turbojet engines to fly supersonic?

is it possible to use just two FJ33 jet engines, so that I would just double the maximum thrust ?

Yes, you will double the maximum thrust on the ground and at rest. You will also double thrust at altitude and flight speed, but that thrust will be much lower than your sea level static thrust. Below is a thrust diagram over speed and for several altitudes for a small turbofan engine with a bypass ratio of 3. It is not the Williams, for which I don't have this kind of diagram, but very similar.

The kink in the low level thrust line is from internal engine pressure limits. At low altitude and high speed the pressure inside the compressor and burners must be limited so they will not be overstressed.
Below 10,000 ft it is not legal to fly faster than 250 kts and supersonic flight is illegal over a lot of areas. In order to achieve legal supersonic flight you need to be high and over unpopulated land. The higher the better, but as you can see from the diagram, thrust drops with altitude. For turbofans it also drops with airspeed. Now it would be interesting to know at what altitude and speed those 9 kN of thrust are required - maybe that number is for a lower altitude and the two FJ33 are indeed sufficient. At the moment that question is unanswerable with the information given.

So I would need a diffusor to bring the supersonic flow down to an optimal flow velocity for the FJ33.

Yes, but that is simpler than it seems. Every engine intake will slow down and pre-compress the incoming air stream at high subsonic flight speed simply because the engine will not be able to swallow all the air that could flow through the intake at high speed. Instead, some air will spill over the intake lips so only the core of the streamtube that flows toward the intake will be ingested. At supersonic speed the intake will do this precompression by means of a shock, the strength of which is again influenced by the swallowing capacity of the engine. Still, the intake cross section needs to widen between the intake face and the engine face and must be carefully shaped to avoid flow separation or speed variations at the engine face (that is actually the tricky part) or you will not be able to achieve the full performance of the engine. A simple pitot intake should be sufficient but it will need some length to do its work properly. Therefore, it is advisable to not put the engine in gondolas (B-58 style, also called nacelles) but to integrate them into the fuselage.
Thrust is the difference between intake an exit impulse, so you need high exit speed in order to have useable thrust at supersonic speed. While a simple convergent nozzle can be used to achieve supersonic flight, the best results are obtained with a convergent-divergent nozzle. Due to the high temperature of the exit flow, even a subsonic exhaust stream will bring you to supersonic speed, but only just. Given the relatively high bypass ratio of the FJ33, if supersonic flight is achieved, the maximum Mach number in level flight will not be much above 1 (if the drag characteristics of the airframe allow even this).


Have any commercial airline passengers ever been injured from hypoxia due to a depressurization event?

The passengers on Helios 522 were incapacitated or died due to hypoxia. Those masks in the aircraft only have enough oxygen to sustain the passengers while the plane descends to a safer altitude, or about 12 minutes. Helios 522 was on autopilot at 34,000 feet for 2 and a half hours. The autopsy showed that the passengers were alive at the time of the crash, but it could not determine if they were conscious. The aircraft was unpressurised at an altitude as high as the peak of Everest, the crew were incapacitated, so it follows that the passengers would have been as well, despite the fact that the autopsy showed that they were still alive at the time of the crash.

Now, let's suppose that they had survived the crash. They were hypoxic for 2 hours, which means they would have suffered brain damage and would be suffering with the long term effects of that (Insomnia, amnesia, etc) as well as injuries sustained from the crash itself.


There are several factors to consider, and depending on your preferences there is not one ideal size and place for a canard. For a first rough concept look at similar designs and use the same canard volume. That is the product of canard area and the distance between its and the wing's neutral points, relative to the aircraft's reference parameters.

$$V_{Canard} = \frac{S_{Canard}}{S_{ref}}\cdot\frac{X_{NP, wing}-X_{NP, Canard}}{l_{ref}}$$

Collect as many canard volumes as you can from different but similar designs and use that for a first draft.

Next, decide on your priorities. Do you want good pitch damping for a pleasant ride even in rough air, use a smaller canard area on a longer lever arm. Damping grows with the square of the canard lever arm while its stabilising effect is only linear. Do the opposite if you prefer more agility.

Next, what center of gravity range do you desire? If, for example, you plan a tandem two seater where due to engine weight and pilot position the second seat is at some distance from the center of pressure, increase canard area accordingly.

So far we looked only at area and lengthwise position. But the vertical position must also be considered. Ideally, the wake of the canard will be above the wing for all practical angles of attack (from cruise to stall), which can be achieved by placing the canard wing high on the fuselage and the wing low. In that position, however, the canard wing might obstruct the pilot's view, so maybe you want to strike a compromise where the wake is below the wing in cruise but above near stall. This can only be achieved with a short lever arm, however.

Regarding the shape: A straight, high-aspect-ratio wing will be best. After all, the canard will fly at the highest lift coefficient of all surfaces so it should have the highest aspect ratio. Use a trapezoidal planform with a ratio of tip chord to root chord of 0.6 - 0.7, or, for simplicity, a rectangular planform which needs only one rig/mold for both sides.

But if what you really want is a good airplane and aren't determined on making it a canard: Place that smaller surface behind the main wing.


How can I calculate the minimum thrust to weight ratio required for a given takeoff distance?

Assuming you know the mass $m$ of the aircraft,  the speed $v_0$ required to take off and the lift and drag associated.
Using basic dynamic and newton's second law you can calculate the average acceleration $a$ required to reach take off speed before the end of your runway:
$$a=\frac{v_0^2}{100\text{ft}}$$
Then using your drag generated at takeoff to be on the safe side
$$\text{Thrust} = m * a + \text{Drag}$$
Implying,
$$\frac{\text{Thrust}}{m}=a+\frac{\text{Drag}}{m}$$


Why do planes above FL290 need more vertical spacing?

The atmospheric pressure changes more rapidly with altitude near the ground than it does higher up.  Assuming an instrument has some error based on determining the difference between two pressures, this error increases with altitude.

Using a standard atmosphere, the pressure difference between 3000 and 4000 feet is 3.3 kPa.  The difference between FL290 and FL300 is 1.4 kPa, less than half.


Why is the maximum endurance for a piston aircraft at sea level?

Try working it from the other end. A propeller needs to generate a certain amount of thrust to maintain a given indicated airspeed to fly.
In thinner air, it must turn faster to do so.
Turning faster is higher RPMs.  Higher RPMs mean more engine friction.
More fuel must be burned per unit time to overcome engine friction at higher RPMs.
RPMs to generate a given amount of thrust are lowest at sea level
(maybe lower in Death Valley (on a colder day)).
Because the horsepower requirement for maximum endurance speed is much lower than the maximum rated output, the horsepower loss due to thinner air is not an issue until one is higher up.  This is why "leaning" is required at higher altitudes.
But "air density" is the correct answer.