Is there a good online source on rotating detonating pulse engine?

The idea seems fairly simple. Here's a [icture from one article and an explanation from another.

From Ars Technica

Micro-injectors squirt a pressurized mixture of fuel and air into a combustion chamber the shape of a long ring (annular cylinder). Then, this gas mixture explodes, with the explosion spinning around the circumference at supersonic speeds. The high pressure produced by the detonation forces exhaust gases upwards (in this diagram) and out of the chamber, where they expand through a nozzle and produce thrust that can be used to push a turbine or aircraft.
Unlike a PDE, which requires repeatedly initiating detonations, an RDE only requires one detonation that spins around and around the chamber, continuously producing thrust.

So there's no conventional turbomachinery. The detonation wave moves in a circle round the chamber, jumping from injector to injector. The only moving parts are the fuel injector pumps. I'm not sure how you throttle it, though.


How to disable GPWS in a 737NG just like how the Airbus can?

There is no way to totally inhibit GPWS on the B737 except by pulling the circuit breaker.

What you can do is inhibit specific modes of the GPWS. This is done via the following switches:

Source: Boeing Co.

The Below G/S switch (1) inhibits the below glide slope alerting.
Flap and Gear inhibit switches (4 and 5) allow inhibiting the "Too Low Flaps" and "Too Low Gear" alerts.
The TERR inhibit switch (6) inhibits the look-ahead terrain alerts and the terrain display on the ND.


How does passenger unloading order prevent plane tipping?

Apparently, there have been a number of incidents with 'tail tipping' in case of Boeing 737-900s and 900ERs. In these situations, the plane 'tipping' on its tail can be prevented by two methods:

Unloading the passengers starting from rear to front.
Unloading the (baggage from) aft cargo hold before passengers were allowed off the aircraft.

There is also some indication that the 737-900s are loaded in the front rows (1-17) first followed by aft rows, while the unloading takes place in the opposite way.


Is it normal for instantaneous GLOC to occur at 5 G's?

That sounds really unlikely to be a G-LOC.  That usually happens at much higher loadings after 3-4 seconds of straining.  The counscious and cognitive centers of the brain take a few seconds to shut down once the systolic and diastolic pressures hit zero in the brain.  It may be an indication of another underlying medical issue.


Is there a relationship between transonic buffet magnitude and altitude?

Transonic buffet, or Mach induced buffet, or high speed buffet, is a flow separation due to the combined presence of shockwave and "high" angle of attack. The boundary layer separation results in random high frequency vibrations. As the AOA increases, the separation and the associated vibrations worsen, up to the point where the crew can no longer read the instrumentation and perform normal flight duties; this point is called deterrent buffet.

For a single Mach number, the AOA (or $C_{L}$) associated with buffet onset is generally constant; there will be some differences due to CG position, the associated trim and Reynolds number effects. During aircraft design and flight testing, the buffet onset boundary similar to the one below is mapped out. As you can see, the general trend is a decrease in buffet onset boundary with Mach (though the trend can reverse depending on the airplane).

(Image modified from https://www.researchgate.net/figure/Typical-buffet-onset-curve-and-separation-mechanisms-defining-the-boundaries_fig2_270086469.)

Flying at the same Mach number at a higher altitude means that it will have smaller dynamic pressure than flying at a lower altitude. This translates to a higher AOA at the higher altitude, which means that the buffet intensity will be higher. In other words, for the same Mach and weight, the maneuver margin is decreased the higher it flies, independent of its climb capability.


When does fuel indicator indicate red index? C172

As always, the answer to this question is in the POH. You should always check the specific POH for the aircraft in question but you can usually find one for common aircraft (such as a 172) online. One such example is here.

Under the section on instruments, and specifically "fuel systems"

  Fuel quantity is measured by two float-type fuel quantity transmitters
  (one in each tank) and indicated by two electrically-operated fuel quantity
  indicators on the left side of the instrument panel. An empty tank is
  indicated by a red line and the letter E. When an indicator shows an empty
  tank, approximately 1.5 gallons remain in a standard tank, and 2 gallons
  remain in a long range tank as unusuable fuel. The indicators cannot be
  relied upon for accurate readings during skids, slips, or unusual attitudes.

I'm pretty sure the "r" variant in your question is the 172 fitted with long range tanks.


What happens if the pilot tries to do a loop in a full-motion simulator?

The motion systems in simulators do NOT mimic the airplane's attitude. Whether the airplane is right-way-up, upside-down or inside-out has no effect on the motion system.

The motion system is used to move local gravity around to mimic the accelerations felt while flying. eg. To mimic the braking during landing, the cab tilts forward, moving local gravity forward relative to the cab, making it feel like you're hanging in the straps due to the braking. Note that when you are braking during landing, the cockpit is level, and yet you are still propelled forward.


Why does flight duration differ for the same flight?

Several possible reasons:

different equipment (not every aircraft flies at the same speed)
different routing
known seasonal changes in high altitude winds (which can prompt routing changes)
extra time built in in some periods for historically experienced frequent delays during those periods (e.g. in summer when a lot of inexperienced travelers with small children are expected, boarding and deplaning tends to take longer than in spring and autumn when there's more business travel).

I'm sure there are other reasons as well.


Is it possible to get the QNH value in Austria using a web service?

The current QNH at an airport is included in METARs so you can grab it form there. There are a few online services to retrieve the METAR automatically, such as this one (using Vienna airport as an example).

The latest METAR when I wrote this answer was:

LOWW 281050Z 14010KT 9999 FEW040 SCT065 BKN300 04/M03 Q1012 NOSIG

which shows a QNH of 1012.

Note that depending on the country the format may vary slightly, but in Austria (and European countries) you should always find a Qxxx value in the report.


How is the visibility at airports measured?

The visibility is measured alongside the runway, usually at various positions, and is called the Runway Visual Range (RVR).

RVR is defined as the range over which the pilot of an aircraft on the centre line of a runway can see the runway surface markings or the lights delineating the runway or identifying its centre line.

RVR is measured using so called transmissometers.

source: keesfloor.nl

These units transmit a beam of light (usually using laser) to a detector. In some case the transmitter and detector are in the same unit and a reflector is used. The ratio of the transmitted energy and the detected energy is a measure of how much light is absorbed in the fog. From this the RVR can be calculated.

Another type of sensor used to measure the visibility on airports is a forward scatter sensor. This type of sensor can be mounted on a single mast and gives more accurate results for visibilities > 2 km. This kind of sensor is used for both determining RVR and Meteorological Optical Range (MOR).

source: KNMI (PDF)

This type of sensor works by detecting how much of the transmitted light is scattered into a detector which is placed off-axis.

Aircraft don't have means to measure the visibility other than the pilot Mk 1 eyeball.


What is the maximum acceptable gap between the jet bridge and airplane door?

In general, there is a gap between the jet bridge (also called Passenger Boarding Bridges or PBB) and the aircraft. This is due to various reasons like,

To prevent damage to the fuselage
The jet bridge may not fit all the aircraft similarly as their fuselage dimensions are different.

According to FAA Advisory Circular 150/5220-21C,

  The PBB should be equipped with sensors to safely prevent
  dangerous contact with the aircraft

The jet bridges at most airports are designed for larger passenger aircraft that are higher off the ground. When a small aircraft utilizes these jet bridges they must use a "ramp" to bridge the gap between the jet bridge and the aircraft.

According to the same Circular,

  The maximum horizontal gap allowable along the path to the aircraft can be no
  greater than 1.25 in (32 mm)

So, I guess that a 4 inch gap is not allowed.


Why are the controls of transport category aircraft much heavier than light aircraft?

The control forces are there by design.  All airliners have artificial force feel from springs, dampers etc. A B747 flies through the skies a lot faster than a Cessna 172 and bad things could happen if it were easy to deflect the flying controls at M 0.85.

The B737 elevator is a good case in point. It has q-feel (artificial feel) provided by a spring device, and the spring gradients stiffen up as a function of airspeed.  At higher speeds it is quite hard to deflect the column by pushing/pulling and much easier to use the trim button to control the pitch. For Level D simulator control forces we measured the forces necessary to deflect the column fully when trimmed in mid position, which turned out to be a serious body-building exercise:

About 200 N at zero airspeed
About 500 N at 400 knots 20,000 ft. (Measurement taken on ground with a pressure hose attached to the pitot tube, and aircraft on jacks with the landing gear retracted).

By contrast, helicopter flying controls are light because helicopters are inherently unstable and a lot of stick action is necessary, particularly in the hover. In most helicopters the feel forces can be switched off completely with the trim button, resulting in a very light stick, perfectly OK with the relatively docile response of the helicopter.

But a 747 is a stable airframe. A fast aircraft with large control deflections results in high accelerations, which can result in Pilot Induced Oscillations or structural damage to the airframe.

The two measurements of B737 control column, digitised from the original plots and on the same scale: column position on the x-axis, force on the y-axis. By design, force required to deflect the column fully from about mid position is about 40 lbf at zero knots, 100 lbf at 400 knots. This is from an artificial q-feel system and the feel is implemented by design. The vertical distance between the sides of the curve is caused by friction.

At 0 knots:

Notice that around mid the spring gradient is very steep: the breakout, to indicate neutral position.
Then between 0 and 5 inch a spring gradient of 4 lbf/inch.
Beyond 5 inch a relatively flat gradient, to make it not too hard to deflect the column fully.

At 400 knots: it is made hard to fully deflect the column. 100 lbf pull from a seated position is nothing to sneeze at.


What closed-cockpit biplane is this model modelled after?

(wikimedia.org)

Beechcraft Model 17 Staggerwing first flew in 1932. It flew air races, served in WW2, and served as a civilian transport. One of its rare features is the lower wing being ahead of the top wing.

  The Model 17's unusual negative stagger wing configuration (the upper wing staggered behind the lower) and unique shape maximized pilot visibility while negligibly reducing interference between the wings.


The FAA handles all US aircraft registration:  FAA Aircraft Registration  Note that there are ownership requirements related to US citizenship etc.  See FAR 47.3


Why was the DC-8-70 successful, but not the 707-700?

I think there is a bit of a misconception in your question.

The DC-8 was already out of production by the time the CFM56 was developed, so all of the DC-8 70 series are actually just retrofits of the 60 series aircraft already in use. So it’s really not correct to say “a CFM56-powered version of the DC-8 became available in 1982.” More like a CFM56 retrofit option for existing DC-8 60 series became available. They did not return to producing the DC-8. On the other hand, although the last civilian 707's were made in 1976, before the CFM56 was available, Boeing did manufacture new military versions of the 707 with CFM56 engines from 1986 to 1991.

As for why the civilian 707-700 was not pursued, the main reason is stated in the Wikipedia page:

  Boeing abandoned the retrofit program, since it felt it would be a
  threat to the Boeing 757 program.

The 757 and 767 programs were already in the works when the CFM56 became available.
The 707-700 was really more of a test program for retrofitting the fleet of military 707 aircraft with the new engines. They didn't pursue a retrofit for the civilian fleet of 707's so they could sell more of the new 757 narrow body aircraft.

If you consider how many DC-8's were upgraded to 70 series (110) vs the number of KC-135’s retrofitted (500) plus 39 more new CFM56 equipped 707 variants, then the new HBP engine was much more successful on the 707.


Do fighters or bombers ever ditch their weapons?

Introduction

I have experience flying the A7-E Corsair off the USS Nimitz in the mid-1980's. There were typical scenarios that would require us to either jettison fuel, ordinance, or other stores. Below you will find a description of some of these scenarios.

 Take off

I was in a brief with my Skipper for a night hop, and he asked me perhaps the best question any one ever asked me in a brief. I didn't have an answer, but started practicing that flight until I left the Navy. He asked, "Salt, what do you do after your take-off checklist while under tension, and right before you salute for the catapult shot?" He went on to describe what he thinks and does.

Reach out look at and touch the salvo jettison button. Physically touch it.
Grab the lower ejection handle.
Salute and come back inside to look at the airspeed indicator. If you don't have 175 knots by the end of the cat stroke eject. No questions.

Every catapult shot I took from that day on I practiced his advice. There were 2 buttons available to jettison stores attached to the pylons under the wing. One was the select jettison, which allowed you to pick a location under the wing, and then jettison that store. The salvo jettison was a big red button close to the middle of the instrument panel, and did not discriminate. Both buttons were next to one another. All stores were ejected from the pylons. If you had a catapult shot that didn't give you enough airspeed off the bow this was an option to buy some immediate lift.

I came off Cat 2 one day and made my clearing turn. As I was cleaning up the aircraft and heading to the squadron's rendezvous point I saw something in the ocean. You know what it looks like when you take a big stone and throw it in a pond? It disappears but leaves a foot print of turbulence and bubbles on the surface of the water. Well, I looked down over the water as I was heading out and saw that kind of footprint. It was as big as an aircraft and persistent, just kind of staying there without dissipating. It looked like an aircraft had ditched, but an A6 had gone off just prior to me and used the salvo jettison getting rid of all his stores.

 Tanker Duty

At times the buddy store would malfunction, and stop transferring with 500 pounds of fuel sloshing around in one of the tanks on the aircraft. You couldn't take a trap with a partially full fuel tank. The slug of fuel would shoot forward, and the tank might be ripped off the pylon. Fuel tanks were not too expensive, but the buddy store had all sorts of hardware and electronics it. Squadrons didn't like to lose these. I had a buddy store on pylon 3 and a drop tank on pylon 4.

On my last rendezvous the buddy store failed to finish transferring all the fuel in my drop tank on pylon 4 and so I said goodbye to the aircraft on my wing and called maintenance to discuss the problem. The maintenance officer got on the radio and we went over the NATOPS procedures for jettisoning the fuel tank. We found a stretch of ocean that was clear of any traffic, and after going over it once he emphasized to me, "Look at the station you selected and read it off to me." After telling him it was number 4, he finished with, "Now make sure you use select jettison and not the salvo button." I pushed the select jettison button and looked in my mirror to see the fuel tank drop away from the wing, and quickly looking in my left mirror caught the buddy store falling away as well. I swear I pushed the select jettison button, and had that image in my head. I had of course hit the salvo jettison button out routine practice of reaching for the salvo jet button every cat shot.

 Air Combat

The performance characteristics of the A7-E put it at a disadvantage against fighters designed specifically for air-to-air combat. The training we received for dealing foreign fighters suggested that, once engaged ingressing to the target, we would make a defensive turn, and if the enemy got behind our wing, jettison our bombs and other stores, e.g. fuel tanks fully committing to the fight. The fuel consumption while at military power at sea level for the subsonic A7-E was around 6,000 pounds per hour, which is quite good. On the other hand, a fighter in burner, by the time it gets to behind the A7's wing line will be fuel starved. To stay in the fight with burner will require a kill within 30 seconds.

 Landing & Dumping Fuel

We brought back weapons all the time to the ship. A good example is the AGM-62 Walleye, a 1,000 pound bomb with a television camera on the nose and in-flight avionics for "guiding" its flight. This was done either by the delivery aircraft, or a second aircraft in a stand-off position. We seldom dropped this weapon in practice, and would bring it back to the ship. We would launch with AIM-9's, when the fighters weren't hogging them all, and bring those back too.

The following acknowledges that there are Rules of Engagement, and within these rules and I will say this. As an attack pilot my mission was to put bombs on target, and if I didn't get the bombs there someone had to go back the next day and finish my job. The enemy would be waiting for that next strike. If for some reason I couldn't get to my target I would find a target of opportunity. Attack pilots don't bring their bombs home with them. Drop them somewhere.

As for fuel, tactical high performance aircraft from the time they take off are emergency fuel in a sense. By the time you got to the landing sequence you were almost always short on fuel. Emergency fuel is at 1,200 pounds and calling the ball at 2,500 pounds was pretty typical. That gave you 30 minutes in the pattern. A divert to another field where there was a climb en-route would eat at that reserve a bit more aggressively.

Every once in a while you might come back heavy with fuel. The maximum field landing weight was 5,000 pounds, and above this weight the procedure was to dump fuel. There were altitude restrictions on how low you could be to do this. The 5,000 pound limit was because the brakes would overheat. This would eventually cause the fusible plugs to blow releasing the pressure in the tires sometime later. This was to be avoided.

 Taking the Captain to NAS North Island

While at NAS China Lake I was working with the A7E software development team on aircraft software enhancements. I would go out and test the software in the operational environment. The detachment there had an A7E Trainer, which was a two seat version of the single seater. I would at times ferry personnel where required. I got a call to take a Captain to NAS North Island and this was a quick hop. I ended up landing over weight. After dropping off my cargo I headed out to the hold short and got a call from tower informing me that my breaks were smoking. I decided to get airborne so I could get home, and if the tires blew in flight, take the gear at my home base. Left the wheels in the air stream climbing out staying below the 220 knot restriction for lowering the gear. The flight was incident free.


What is the flight that returned to base after dumping fuel due to toilet issues?

I'm going to be a bit lazy and only point you in the right direction (sorry):
The Aviation Herald website is a simple, yet excellent source of aviation "occurences". There is a search tool at the top of the page, here is a link to a sample search I did using word lavatory:
Avherald.com search with word lavatory
...and below is a sample report picked from the results of the aforementioned search.

Incident: Jet2.com B738 near Cork on Aug 4th 2019, lavatory issues
By Simon Hradecky, created Monday, Aug 5th 2019 21:46Z, last updated Monday, Aug 5th 2019 21:46Z
A Jet2.com Boeing 737-800, registration G-JZBC performing flight LS-167 from Glasgow,SC (UK) to Lanzarote,CI (Spain), was enroute at FL360 about 90nm south of Cork (Ireland) when the aircraft turned around due to problems with the lavatories and diverted to Manchester,EN (UK) for a safe landing on runway 23R about one hour later. A passenger reported toilets were leaking water flooding the aircraft. The airline reported the aircraft diverted to Manchester to permit maintenance to service the toilets. A replacement Boeing 737-800 registration G-GDFV reached Lanzarote with a delay of 3.5 hours.

Searching the avherald.com database with relevant words will give you a plethora of cases for your white paper.


What's the meaning of underlined frequency in sectional chart nav aid box?

Navigation receivers can be used as a fall back for regular VHF/HF radio transceivers

Before data links, there were essentially two types of radio receivers in the flight deck, and this is still the case for most GA aircraft: "COM" used for voice communication, and "NAV" used to receive navigation signals. When COM transceivers fail, the pilot is left without information from ATC, and will follow their current flight plan and clearances.

However ATC may try to send additional information and new clearances using the NAV radios. In that case this is a one way communication, as NAV aboard the aircraft have no transmitting capability.

Information provided to ATCO by FAA in JO 7110.65:

  a. In the event of lost communications with an aircraft under your
  control jurisdiction use all appropriate means available to
  reestablish communications with the aircraft. These may include, but
  not be limited to, emergency frequencies, NAVAIDs that are equipped
  with voice capability, FSS, Aeronautical Radio Incorporated (ARINC),
  etc.
  [...]

  b. Broadcast clearances through any available means of communications
  including the voice feature of NAVAIDs.

The voice feature is present on all navaids, except TACAN. It may also be used to transmit ATIS when no communication emergencies are going on.

Pilot has also instruction to use NAV receivers, e.g. in AIM 6-4-1. Two-way Radio Communications Failure, 6-4-3. Reestablishing Radio Contact:

  a. In addition to monitoring the NAVAID voice feature, the pilot
  should attempt to reestablish communications by [...]

Audio mixer, source

Navaids without voice capability

No voice or underlined frequency indicates ATC can't use this navaid for to transmit voice messages.

Such navaids have a class code W (without), e.g. CHANDLER NDB in Arizona:

Source: AirNav

Source: SkyVector

See also:

NORDO.


At what age may a student log time and use that time to obtain a rating?

FAR § 61.83 states:

To be eligible for a student pilot certificate, an applicant must:
(a) Be at least 16 years of age for other than the operation of a glider or balloon.
(b) Be at least 14 years of age for the operation of a glider or balloon.
(c) Be able to read, speak, write, and understand the English language. [...]

A student pilot certificate enables you to fly a plane solo or on a solo cross country.
In other words, you need to be at least 16 years old to fly a plane (non glider/balloon) solo.

Now, back to your initial question. If you go through FAR §61.83 - §61.95 you will find all the regulations about student pilots (which would be the kind of pilot you are referring to ).
I have found no age restriction going through them for the pre-solo instruction. All it says that it must be done before soloing which does require a medical exam and certificate (but these don't have age restrictions either).
Summing up, a 9 or 12 year old child is legally able to take flying lessons with an instructor, but may not solo before his/her 16th birthday (no glider/balloons).


Why do the inlet cones on an SR-71 retract at higher speeds while the one on a MiG-21 extends at higher speeds?

This is only a guess, so please take this with a grain of salt.

An important characteristic of supersonic engine inlets is the total pressure loss (or also sometimes pressure recovery). The total pressure loss over a normal shockwave is a lot higher than if you would slow down the air to the same speed through several oblique shock waves.

If you want to understand why the sr-71 spike retracts I recommend you watch this video. The sr-71 had a quite complex inlet geometry to ensure that the air was slowed down over many oblique shocks.
sr-71 engine inlet

On jet engines that don’t have such a complex inlet geometry as the sr-71, the best pressure recovery is mostly achieved by getting the primary oblique shockwave from the spike or inlet ramp, to hit the leading edge of the engine inlet, where it gets reflected as another shockwave.

As speed increases the primary oblique shockwave that gets formed on the spike gets shallower meaning that if you wanted to keep the shockwave of the mig-21 spike at the leading edge of the engine inlet, you need the spike to move forward as speed increases.


Why are different routes flown between the the same pair of airports?

Lots of reasons are possible, ranging from winds to other issues. In this case I'm willing to bet that the first flight was based on the most efficient routing to take advantage of tailwinds en route and that the second was avoiding Syrian and Turkish air space because of the political issues there earlier this year.

See also:

Flight Delays Incurred Avoiding Syrian Airspace
Royal Jordanian stops flying over Syrian airspace


Is it true that different variants of the same model aircraft don't require pilot retraining?

It appears to depend on how much changed. You do have to have some training between models. The selling point was that an airline with 737 pilots could fly the MAX variant with minimal retraining

  "The airplane is configured to be very common with the [737 NG]," Wilson, who is now retired, said, "and so a pilot can walk into here and will find everything he can just like he can in the [737 NG]."

  "FAA-approved this for two-and-a-half hours of computer-based training for the transition between the two aircraft," Wilson continued. "All the overhead panel switches are the same. The only minor difference is, because of the change in the display, is to move some of the center console items here on the forward console."

And from the Wall Street Journal

  To make the plane as inexpensive as possible for airlines to adopt, Boeing was intent on persuading regulators that pilots of earlier 737s should be allowed to start flying the MAX without simulator training. That training would have been required if there were substantial safety differences between the models, boosting the plane’s cost to airlines since training cuts into time flying paying passengers.
  “Our marching orders are no training impact on this airplane. Period,” Richard Reed, a former Federal Aviation Administration engineer, recalled a senior Boeing official telling him during a meeting in the early years of the MAX’s development.

  The company had promised its biggest customer for the MAX, Southwest Airlines Co. , that it would pay it $1 million per plane ordered if pilots needed to do additional simulator training, according to Rick Ludtke, a Boeing engineer who worked on the jet’s cockpit systems, and another person who had been involved in the airplane’s development.

And later

  Boeing officials were focused on making the MAX fly as similarly as possible to earlier 737s. The fewer differences, the less likely the FAA would require pilots to undergo retraining.

  Mr. Ludtke, the former Boeing cockpit engineer, said company managers put pressure on engineers to avoid tweaks in designs that could result in pilots needing to learn new maneuvers in a simulator.

Wasn't there a difference?

The issue was that the MAX had a system (MCAS) that could push the nose down to make it behave more like previous 737s. Having read several articles on it, the root problem was

The initial specs said it was a minor change with the same course of action to correct as a runaway stabilizer (i.e. it was something 737 pilots already knew)

  The company reasoned that pilots had trained for years to deal with a problem known as a runaway stabilizer that also can force the nose of the plane to dip. The correct response to an MCAS misfire was identical. Pilots didn’t need to know why it was happening.

Boeing made MCAS 4x more powerful without really notifying anyone. It could also operate at slower speeds.
Boeing apparently wrote its manuals based on the original MCAS spec. Assuming it was still a minor system, it was buried or omitted

  Southwest Airlines, the jet’s first and biggest customer, followed Boeing’s lead and deleted MCAS from the manuals and emergency procedures it devised for its pilots. Other carriers didn’t mention it, either.

As predicted, the previous crew of the aircraft that would be Lion Air 610 had issues with MCAS, but correctly diagnosed a runaway stabilizer and shut off MCAS in the process

  The puzzled cockpit crew checked a quick reference handbook, running through other emergency steps before successfully regaining control of the plane by executing the checklist for a runaway stabilizer. That turned off MCAS and the crew flew manually for the rest of the trip.

Lion Air 610 would not be so lucky. They only figured it out moments before the plane slammed into the ground. Apparently it wasn't as obvious to pilots as Boeing thought.


A380 reverse thrust on only half the engines

Yes, the outboard engines do not have reverse thrust to avoid them kicking up dirt. On a regular runway they will be outside of the concrete surface, so using reverse thrust there will incur the risk of foreign object damage.

This was already covered in this answer.


Should landing on a runway that has been closed by NOTAM be a violation of the FARs?

There's no specific rule against it, so whether it should be a violation is a matter of opinion. FWIW, AOPA's legal counsel believes it isn't a violation per se, but the FAA has still pursued action against airmen for doing it.

The 'obvious' regulation involved is 91.13:

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

The NOTAM is presumably there for a good reason and even if the runway seems clear and usable from the air, there may be hazards or poor surface conditions that you can't easily make out. As AOPA's counsel pointed out in the article above, the FAA apparently ignores the requirement to prove "endangerment" but the NTSB also seems to back them up on that, so as a pilot you probably have little chance of arguing successfully that a landing wasn't reckless.

A famous (infamous?) example of landing on a closed runway was Senator Inhofe in 2010. Afterwards he said that no one checks NOTAMs anyway and it just wasn't a big deal, despite there being workers and equipment on the runway at the time. As it happens, he's a member of the Senate Transportation Committee, which oversees the FAA, and he represents Oklahoma, where the FAA has its headquarters. He was required to do remedial training and that might or might not have been appropriate but personally I suspect that if I buzzed some construction workers and then told the FAA that I didn't care about NOTAMs, I'd be a lot more likely to get enforcement action.


Why do airplanes use an axial flow jet engine instead of a more compact centrifugal jet engine?

Centrifugal compressors only produce a more compact engine at low mass flow, which means low thrust.

The amount of thrust an engine can produce is proportional to its intake area times exhaust velocity. Increasing the latter is undesirable, as energy and thus fuel consumption is proportional to velocity squared. So engine designers target mass flow to gain more thrust, not more velocity.

Since they are 3D structures, in a basic solid design (that you'd find in early jets and small modern turbines), the volume of a centrifugal compressor grows in cubic proportion to its diameter, while frontal area, which limits its mass flow and thus its thrust, increases only as diameter squared. This creates a cube-square law.

Large real-life parts are filled with lightening and cooling channels, so the mass-to-area law is more complex. Still, it cannot eliminate the volume effect entirely. The end result is that the mass of centrifugal compressors grows considerably faster than their mass flow.

At the highest power levels, centrifugal compressors become prohibitively heavy even for fixed powerplant machinery, where durability otherwise trumps weight, so the largest base load powerplants run all-axial. With axial compressors, the flat design with a short air flow path allows mass to only grow in direct proportion to mass flow, and very powerful engines can be built within reasonable dimensions.

It's not pure cube-square law in either case, but it's something like k1*massflow^[2.5, 2.8] for centrifugal versus k2*massflow^[2.2, 2.4] for axial, where k2>k1, giving centrifugal compressors some advantage in small sizes. Centrifugals are also much cheaper to produce (at least small ones).

High-performance engines, such as those in commercial aircraft, also need to pack more thrust into the smallest cross-section they can, while maintaining efficiency, so as to reduce drag and also fit under the wings, enabling heavier jets. Axial compressors offer a lot more intake area for any given cross-section - thus more thrust.

The smallest jets, where thrust requirements are small and the engine's cross-section is very small compared to the fuselage, can afford the extra diameter of a centrifugal or diagonal flow compressor. Yes, it's the same cube-square law (also reduced somewhat in practice) that keeps the engine cross-section to total cross-section ratio increasing as aircraft go up in size. Small centrifugal compressors are simpler, easier to build, and more robust than small axial ones.

So in every industry, as power grows, there is a crossover point from centrifugal to axial. For aircraft where drag is critical, it's just above small bizjets, mobile ground and helicopter turbines stay centrifugal or mixed up to a few MW, and in the tens of megawatts even fixed powerplants switch from axial/centrifugal to all-axial.

Engines close to that crossover point typically combine axial and centrifugal stages. Newer diagonal compressors are in-between and quite good, offering an even more tailored compromise.


Does flight training have any impact on my H1B visa?

Having flight training has no effect at all on your visa status. It's actually the other way around: your visa status can determine whether or not you can have flight training. But you can definitely get flight training with an H1B.

And flying has no special impact on your job: how you choose to spend your free time is none of your employer's business. There could be some very specific scenarios where flight training and work intersect, e.g. if your company is in the aviation sector you might be able to get them to pay for training. Or if you're a very senior executive at a very large company then the Board of Directors might have concerns about you spending your time on 'risky' activities. But otherwise, flying has nothing at all to do with your work.


Why is it assumed on sectionals that the area outside of a 700 AGL Class E (Echo) transition area is Class E starting at 1,200 AGL?

Take a look at the legend on the side of a VFR chart. (You can get them for free at https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/vfr/ )

Class E exists at 1200' AGL unless otherwise designated as shown above.


Why are brake temperature limitations lower when the brake fans are running?

The fans cool not only the brakes, but also the temperature sensors, at different rates. The temperature difference is a measure to correct this anomaly. From the document  Proper Operation of Carbon Brakes by Airbus Flight Operations Support:

  ... the  temperature  indicated in the cockpit when the brake fans are running is significantly lower than the temperature indicated when the brake fans are OFF. This is because the brake fans are ventilating the brake temperature sensor that is not located inside the material itself. Therefore,
  as soon as the brake fans are running, the indicated brake temperature  decreases almost instantaneously.

  ... For all brake types, when  the  fans  are  running, the difference ranges typically  from  approximately  50°C  at  100°C actual brake  temperature up to about 150°C  at  300°C  actual  brake temperature.

  ... When fans are selected, the warning will disappear instantaneously,  but the takeoff must be delayed until the indicated temperature  consistently decreases below 150°C (for a warning set at 300°C)


Can a company be both an airplane manufacturer and an airline?

Another historical perspective: Junkers helped to found and participated in dozens of airlines in the early 1920s. This helped to boost demand for his products (mainly the F-13, but all started with two converted military two-seaters).

That was everything but unusual: Many aircraft factories, among them Albatros and Sablatnig in Germany, tried to shift their products after the cessation of hostilities by founding airlines.

Generally, when a city wanted to be connected to the new air travel network, it would supply an airfield and some capital and the aircraft company would be happy to contribute aircraft and personnel. This way, dozens of airlines providing mostly local connections were operating in the early Twenties in Europe and competition would drive down prices and increase demand. Therefore, all those airlines were unprofitable and successfully lobbied for government support, which grew from year to year. But also Junkers was not profitable and had to be supported by government loans.

By 1925, 40% of all civil air traffic worldwide was flown on Junkers airplanes and Junkers Luftverkehr AG completely or partially owned many of the airlines operating its aircraft. The failure of Junkers to repay government loans at the end of 1925 meant that ownership of those shares was transferred to the German government which moved swiftly to consolidate the German airlines into Luft Hansa, thus ending the price war and greatly helping to reduce the subsidies.

By resolving to only subsidize one single airline, the national flag carrier, Governments effectively ended the habit of aircraft manufacturers to operate airlines. Specific legislation was not needed.


Callsign includes the term 'with Kilo' ; What does that signify?

What that probably means is that the pilot is reporting that they have ATIS information kilo. Automatic Terminal Information Service (ATIS) is a radio broadcast on a specific frequency (often a local navaid like a VOR) which a pilot dials up to get weather and airport information before joining one of the airfield's frequencies. Each time the information is updated in a day the next letter of the alphabet is used; "information Kilo" means the information has been updated 11 times that day.

If the tower had to relay weather, runway in use and other instructions to everyone pilot who joined the frequency it would take loads of their time; ATIS is instead there so controllers can spend their time controlling. When a pilot introduces his/herself on frequency at an airfield they announce the latest ATIS they have so that the controller knows they have up to date information and they don't need it relayed.

From a phraseology standpoint just saying "with kilo" is okay. I usually say "with information kilo" because it makes sure that kilo isn't confused as being part of my callsign.


What is the smallest aircraft to have a CVR / FDR?

Looks like in the EU as well as in the US the Cessna CE-510 Mustang needs one according to the minimum equipment list.

In the EU

  -70-01

  *** Cockpit Voice Recorder (For Combined Voice Data Recorder, refer to 31-30-01)

And in the US

  -30-01

  *** Flight Data Recorder (FDR) System

That is a 6 seat plane, you will be hard pressed to find something smaller although other similar in class aircraft may also have them.

It looks like some versions of the Cirrus SR-22 include an Aircraft Data Logger but im not sure if that conforms to the various impact regulations for a black box.


What is this very isolated, modern aviation/heliport in Northwest Antelope Valley, California?

It appears to be the Northrop Tejon Ranch RCS facility. It is used for testing of radar cross sections. There’s a page here with a little more info on it.


Does Jeppesen display runway declared distances on their charts?

No.

What does the runway distance mean under "Additional Runway Information" on Jeppesen plates?
What are Runway Declared Distances?
How do pilots use stopway, EMAS, clearway and displaced threshold?
How do runway declared distances affect my takeoff distance?

Jeppesen uses its own method to calculate additional runway information.  They have been providing additional runway information long before the FAA started providing declared distances and are fairly accurate but there is some discrepancies pilots using Jeppesen products need to be aware of.
Analysis of the two runway distance providers show Jeppesen's takeoff value is very close to the FAA's TORA value.  Jeppesen's landing beyond threshold value is the same value as the FAA's LDA value.
The two values that Jeppesen does not provide information for is TODA and ASDA.

TORA: Takeoff runway available
TODA: Takeoff distance available
ASDA: Accelerate-stop distance available
LDA: Landing distance available

It is the ASDA value that will get multi-engine pilots in trouble.  From the previous Q&As we learned that multi-engine pilots are required to ensure the airplane's accelerate-go distance is not greater than the TORA or TODA value (depending on whether or not their airplane can use a clearway for takeoff considerations) and their accelerate-stop distance must be lower than the ASDA value.
If these multi-engine pilots fail to reference applicable declared distance information they could potentially takeoff at a weight greater than allowed by their AFM and FAA regulations.
The FAA has developed a presentation talking about runway declared distances:
http://www.faa.gov/tv/?mediaId=1132

How about examples:
Lake Tahoe, CA (KTVL)

Analyze the data and you will see that if multi-engine pilots only go by the takeoff distance on Jeppesen charts they could takeoff overweight.  Jeppesen does not include ASDA values on their charts.
These pilots may conclude they can use the whole length of the runway for takeoff performance.  If their takeoff distance is the runway length they will lose the runway safety area protections designed to keep them safe.
There are many other examples.  KPIT, KSUN, KGYY, KPBI, KMIA.  Airports big and small have this issue and multi-engine pilots need to be aware of the lack of information presented to them by Jeppesen.
Stay safe!

An email from Jeppesen concerning this oversight:  After reading the email response below, it may not be a good idea to trust the runway information presented by Jeppesen.

Our Airport Diagram Charts are designed to be used for air navigation, flight procedures, and airport operations. They are not designed for aircraft performance planning. The distances contained in the Usable Lengths section of the Jeppesen Airport charts are informational and are not intended to be used for take-off and landing performance planning. These distances are provided on the charts to assist with the operational use of the runway. In order to comply with published declared distances, pilots need to reference take-off and landing performance planning data that is provided by either their own performance group, or another provider, such as Jeppesen’s OpsData service. OpsData provides on-demand runway take-off and landing performance analysis for airports worldwide, in part by analyzing, using, applying and presenting Airport Declared Distance data.
Another reason that the usable lengths are informational is that we do not revise our charts for all state source that we receive, we instead analyze that source and then revise charts based on our process criteria. What this means for the usable lengths is that we only process charts for changes in usable lengths when the change is greater than 200’. If the only change on a chart is the usable lengths and they are less than 200’, then we will make a note of the change and apply it to the chart when it is next revised sometime in a future revision. On the other hand, OpsData will update declared distances and re-run performance calculations whenever any of the lengths change by 25’ or more.
We don’t identify what the Usable Lengths should and shouldn’t be used for in the Airway Manual. Since the lengths are not intended to be used as declared distances, we have refrained from labeling them as such. That is why only some lengths are supplied and they are located under the heading ‘Usable Lengths’. The Introduction section defines the lengths we do supply and mentions that they are in regards to the physical runway length only (i.e. they don’t take into account any stopways, clearways, etc.).
AIM 4-3-6 provides the definitions of declared distances and where pilots can find them, which is the Chart Supplement (formerly the A/FD). For pilots that don’t have the availability of performance planning services, this would be where they could go to find that information.


Why doesn't the A320 have a dorsal fin like the 737?

Boeing learned the value of a dorsal strake the hard way: On their civilian version of the B-17, the Boeing 307 Stratoliner, the first Boeing aircraft with a pressurized cabin, the lack of a strake ahead of the fin caused the rudder to lock in the hard-over position when the pilot demonstrated the capability of the aircraft to fly with two dead engines on one side. The aircraft entered a spin and crashed, and that was on a demonstration flight for prospective customers.

Early Boeing 307 with the two right engines off and props feathered (picture source). Note the deflected rudder and the rectangular windows in a pressurized fuselage. It worked because the pressure difference was small.

Late Boeing 307 in flight (picture source). The vertical was enlarged and had the strake added; the same vertical was also used on later versions of the B-17.

With today's hydraulically operated controls the risk of an uncontrollable hard-over is reduced, but exactly this happened to several early Boeing 737s. From the 737-300 on the strake was added and the control system (PCU = power control unit) was exchanged for a  modified version.

Airbus never had those issues and did not see the need to add a strake since the existing vertical could do its job in all conditions. A strake is worthless at small sideslip angles and will only help when the vertical is close to stalling due to extreme sideslip. Adding a strake will increase the wetted surface area and add friction drag, so Airbus did not include one.


Why, on carrier landings, does the Flight Path Marker (FPM) seem to be placed near to the end of the runway?

The short answer is that it is because the carrier is moving toward the point that the FPM is indicating; where the ship and aircraft will converge at the moment of landing.

In reviewing my answer to the other question linked in the comments, it struck me that some clarification might be needed to distinguish between landing visually, or by reference to ship based ILS, versus flying a HUD equipped aircraft.  In the first two cases, (visual or ILS) the frame of reference is the ship itself.  Whether the ship is stationary with 30 knots or natural wind across the deck, or steaming at 30 knots to make wind on a calm day, the indications to the pilot are identical.

Contrast that with a HUD equipped aircraft.  The FPM uses the earth as a frame of reference, not the ship.  It shows where the aircraft is going relative to the surface of the sea, its position is based on calculations from inputs of GPS and air data computer, and factors in the wind.  (which itself is calculated…)  It doesn't know or care if the ship you are trying to land on is moving.  Therefore, if the ship is stationary one would expect that the FPM would indicate a touchdown point right in the landing area.  Just as it would a stationary runway on land.  (if the pilot is doing his or her part!)

If the ship is steaming at 30 knots the FPM will still indicate where the aircraft is going relative to the surface of the sea.  However, since the carrier is moving as well, the FPM will be out in front and to the right of the landing area during approach.  (Because the ship hasn’t gotten there yet!)

In the video you can see that the ship has a decent wake behind it, but as the aircraft closes in the FPM moves from up and right, to right in the landing area at touchdown.

Keep in mind also that the FPM is pretty much instantaneous, so that pilot corrections to glideslope deviations will show up as well.  For example, if the pilot rolls out high and right at the start, even if the ship is making all its wind the proper correction might put the FPM down and left until re-correcting.

And finally, the Navy discourages “HUD Cripples”.  While (I have heard) it is a wonderful tool, the pilot should reference the traditional meatball, lineup, and AOA on short final.  So while the pilot is supposed to be aiming for the ship, his or her FPM may actually be aiming just a bit in front!  ;)


Are regulations covering private jets different from those covering commercial jets?

Technically no, but in the spirit of your question, yes.

All aircraft, including those operated for private and commercial purposes, are governed by 14 CFR 91 - General Operating and Flight Rules.

14 CFR 119 specifies additional regulations that govern certain types of aircraft and operations, including larger private aircraft and commercial operations:

14 CFR 125 covers larger (airline style) private aircraft
14 CFR 121 covers the airlines
14 CFR 135 covers commuter and on demand (charter) commercial operators

So it isn't that private aircraft have relaxed regulations, it is just that they aren't required to comply with the additional regulations that govern the airline and charter operators.

There are many, MANY additional regulations that commercial operators have to comply with, including operational and maintenance regulations.

A few example:

Pilots flying commercially have strict limits on the time that they are allowed to fly or be on duty.  Pilots of private aircraft don't have any limit, other than not to fly if it would be unsafe.
Commercial pilots are subject to more strict medical requirements.
If an aircraft has to divert due to a mechanical problem, it must be reported to the FAA if being operated commercially.
There are strict limits on how far that a commercially operated aircraft may be from a suitable airport, but there are no such limits for privately operated aircraft.
Passengers must be screened and must be checked against government maintained no-fly lists for commercial flights.
An aircraft used for commercial purposes is required to be inspected more often.
With certain (very limited) exceptions, commercial aircraft are required to be operated by a company (certificate holder) with required management personnel such as the Chief Pilot and Director of Maintenance, while private aircraft can be managed by one person (even the pilot).

See the online eCFR for the specific regulations that fall under each part.


Why is the coefficient of drag for straight wings at supersonic speeds lower than for swept wings?

Mark is right when he says that there is no induced drag at supersonic speeds, but it is an invitation for misunderstandings. Induced drag is replaced by lift wave drag, and all what happens is that aerodynamicists choose to use two different names for basically the same effect: Air gets pushed down.

As usual when I post a long answer, I was not quite happy with the existing answer(s). Now I have some time and try to give a better answer.

First, why does the straight wing work better only at very high Mach numbers (> 2.0)? Because at lower supersonic speed a swept wing gives overall better performance. The sweep angle $\varphi_0$ must be high enough to allow for a subsonic leading edge (Mach < $\frac{1}{cos\varphi_0}$). Then the flow around the leading edge is subsonic and creates a suction area when accelerating around the nose contour. This suction helps to reduce drag - after all, this same suction is why a subsonic airfoil in inviscid flow has no drag. Edward C. Polhamus did a lot of research on this at NACA Langley and published several papers with equations for calculating the suction force.

Once you fly faster than Mach 2, the sweep angle for a subsonic leading edge rapidly gets too high for acceptable subsonic flight, and an unswept wing becomes the better alternative since you need to accept a supersonic leading edge. Examples are the wing of the F-104 or the canard of the XB-70.

Now for the airfoil drag at supersonic speed. Because it is easiest to explain, I select a rhombic cross section:

Rhombic airfoil in supersonic flow at zero angle of attack (own work). The plus sign denotes higher pressure, the minus sign lower pressure than ambient. By selecting a rhombic airfoil, the flow is very easy to determine because the pressure only changes when the local contour gradient changes. The two compression shocks create the typical sonic boom when arriving at the ground. Note that this airfoil already creates pressure drag even at zero lift. Any airfoil thickness greater than zero and any airfoil camber will cause this type of drag where the forward-facing areas see higher pressure and the rear-facing areas experience suction. This type of drag is called wave drag. It can only be minimized by minimizing the relative thickness of whatever is supposed fly at supersonic speed.

When the angle of attack is increased, this airfoil begins to create lift. Now the compression by the lower forward shock becomes stronger and that by the upper forward shock becomes weaker. The expansion fan is the same again on both sides, so the upper rear half experiences less pressure than the lower rear half. I tried to symbolize this by the amount of plus and minus signs:

Note that the pressure difference is constant over chord, so the center of pressure is at 50% of chord length. Note also that the lift vector is perpendicular to the chord line. Since lift is defined as the force perpendicular to the direction of the undisturbed air, supersonic lift always carries a drag component which is proportional to the angle of attack - there is no suction at the nose to alleviate this! The wave drag of the airfoil at zero angle of attack still comes on top, so we have a shape-dependent wave drag and a lift-dependent wave drag component. This lift-dependent wave drag replaces the induced drag of subsonic speeds. If we compare the magnitude of both, we find:

Subsonic: $c_{Di} = \frac{c^2_L}{\pi\cdot AR\cdot\epsilon}$

Supersonic formula for 2D flow: $c_{{DW}_L} = c_L\cdot\alpha$

This doesn't look so similar, so let's now express the angle of attack $\alpha$ by the lift coefficient divided by the lift curve slope:

$$\alpha = \frac{c_L}{c_{L\alpha}} = \frac{c_L}{\frac{4}{\sqrt{Ma^2-1}}\cdot\left(1 - \frac{\lambda}{2\cdot AR\cdot\sqrt{Ma^2-1}}\right)}$$

and the lift wave drag component becomes $c_{{DW}_L} = \frac{c^2_L}{\frac{4}{\sqrt{Ma^2-1}}\cdot\left(1 - \frac{\lambda}{2\cdot AR\cdot\sqrt{Ma^2-1}}\right)}$

Now let's compare the F-104 wing, which has an aspect ratio $AR$ of 2.45 and a taper ratio $\lambda$ of 0.385: If we plug in the parameters and adjust $\epsilon$ such that both sub- and supersonic lift-dependent drag coefficients agree, $\epsilon$ would need to be 0.89 at Mach 1.2, 0.58 at Mach 1.4 and 0.31 at Mach 2.0. The dramatic rise of lift wave drag over Mach is caused by the reduction in the lift curve slope over Mach.

For slender bodies the lift curve slope is $c_{L\alpha} = \frac{\pi\cdot AR}{2}$ and the lift wave drag component becomes $c_{{DW}_L} = 2\cdot\frac{c^2_L}{\pi\cdot AR}$. For slender bodies the supersonic $\epsilon$ is 0.5, regardless of Mach.

The important conclusions from this for wing selection are:

Sweep does no longer help once the leading edge is supersonic.
Lift wave drag continues where induced drag drops off. Lift always causes drag.
For a supersonic wing the aspect ratio is of minor importance.

Now back to the original question: Once the leading edge is supersonic, sweep is no longer helpful. Now the best wing is straight, because it will need the lowest wing area to create the required lift at subsonic speed. At supersonic speed its lower area will translate into lower friction drag, making it better than comparable delta or swept wings.


What is the 3 click sound when the autopilot is disconnected on Airbus aircraft?

There are two separate aural warnings that you might be referring to: one is indeed called 'Triple Click' and consists of three brief clicks, but is emitted when the landing capability becomes degraded or the autopilot otherwise changes mode.

The warning generated upon autopilot disconnection, instead, is the so-called 'Cavalry Charge' and consists of three longer beeping sounds; it's either played once or repeated continuously (cases 1 and 2 below).

From a table in the Airbus A320 FCOM, DSC-31-10 P 4/6:

  TRIPLE CLICK

  Meaning: Landing capability downgrade or some cases of mode reversion.

  Duration: 0.5 s (3 pulses)

  CAVALRY CHARGE

  Meaning:

  A/P disconnection by takeover push-button.
  A/P disconnection due to failure.

  Duration:

  1.5 s
  Permanent

  Cancellation:

  Second push on takeover push-button.
  Press Master Warning light or takeover push-button.

See this YouTube video (at 2:52) for a cavalry charge immediately followed by a triple click (thank you Jack).


Are there differences between the runway lighting on a land runway and on an aircraft carrier?

Yes, basically just (dim) Edge and Centerline lights plus the IFLOLS


Can VOR indication be reliable if one of its antennas breaks?

No, it should not be used.

Twin antennae, as you have shown, are balanced and fed into a balun (BALanced to UNbalanced) to feed the single transmission line to the receiver.   Together, they provide the correct impedance for the aerial system.  With an antenna broken, it is likely that the impedance of the circuit is wrong and therefore, the input to the receiver is, at best, suspect.

[GUESSWORK]

It's impossible to predict the indicated behaviour without knowing precise details of the aerial fit but a reasonable guess would be that the standing wave ratio in the feed will be altered and therefore, a phase error will be introduced.  The magnitude of the error will vary in proportion to the sine of the actual phase angle so my guess would be that the bearing will be accurate when due South or North of the VOR then increasingly inaccurate as you move round with an maximum error at 90 or 270.

[EDIT]

Early in the morning when I first wrote this but I think I am wrong about being accurate due North or due South.  It will be accurate somewhere on the compass and at 180 degrees opposite to that, with increasing inaccuracy as you move towards 90 degrees away from that somewhere.  Only calibration would tell you where the somewhere is.


Compliance with Airworthiness Directives (ADs) involves an appropriate logbook entry. Examine the aircraft logbooks, or have someone competent in the subject matter—an aircraft mechanic, for example—to determine if applicable ADs have been complied with.

Each AD requires different compliance measures, ranging from a one-time inspection or parts replacement to recurring inspections. In each case, a logbook entry should be made to document compliance. Apart from the logbook entry, the aircraft or components concerned can often be inspected to confirm compliance, such as checking for a marked part ot that a placard installed. The details of what such an inspection could confirm would vary depending on what the AD requires.

In some cases, such as AD 68-17-04, which deals with Cessna stall warning systems, the AD calls for a one-time inspection followed by installation of a placard. The placard calls for the pilot to test the stall-warning system as part of pre-flight. In such a case, compliance with the AD extends beyond the actions of maintenance personnel, and will include pilot compliance with aircraft limitations—the placard.

Now, you seem to be asking three questions, beyond the title question of How does one determine if an airplane meets airworthiness directives? Let me paraphrase these questions:

How does one determine if ADs have been complied with?
How does one find ADs that apply to an aircraft?
How does one find "safety bulletins" for an aircraft?

The first question I have answered above.

The second question is primarily the purview of aircraft mechanics, especially IAs where applicable. The site you linked is a good way to find applicable ADs. It sounds like you may have run into some difficulty in getting the site to work correctly. A search for "Cessna 172" returns 21 ADs. Since ADs list aircraft or component applicability by make, model, and serial number range, among other criteria, each AD will need to be examined to determine if it is applicable to any given aircraft.

The third question is more difficult. Airframe, powerplant, and parts manufacturers may issue Service Bulletins and disseminate them at their choosing. Some manufacturers are easier to deal with in this regard than others. An exhaustive answer on this topic is beyond what is appropriate here, in part because it is constantly changing. If in doubt, contact the manufacturer for what you need.


How can the fuel decrease evenly from both wing tanks when an A320 is running on APU only?

If you look at the fuel leak checklist you will see that you will come to this point only after you have confirmed that there are no leaks from the inner wing tanks and engine fuel feed lines.
According to the checklist if there are no visual indications of fuel leaking near the engines, you are to ensure the fuel cross feed is maintained closed. Then you turn off the center tank pumps. When the center pumps are off the engines will be only supplied by the inner tanks. Then you are to monitor the fuel in the tanks for a total of 30 minutes. If one tanks depletes faster than the other tank by 300 kg you can assume an engine leak. So, you shut off the associated engine. If this stops the leak, engine leak is confirmed. If it continues to leak you can assume an inner wing tank leak.
Now, the checklist says, if both the inner tanks deplete at a similar rate, you can suspect a center tank leak (remember the pumps are off) or a leak from the APU feed line. I have highlighted the word similar, because the checklist says to check for similar readings, not same or symmetrical readings. Yes, with the APU on, the left wing inner tank will deplete faster than the right tank, but it should not bring a massive difference to the figures. The A320 APU burns about 130 kg of fuel per hour. The checklist says to monitor the fuel for 30 minutes. This means, at the APU fuek line a leak would happen at a lower rate. That is why it says to look for similar rates, because an APU fuel line leak is quite insignificant. But you cannot still assume no leaks at the APU fuel line. The fuel leak checklist is a very conservative checklist. It is all about trying to close off any possible areas where a leak might be possible.
The checklist also says that if you have a fuel smell in the cabin, to turn off the APU to prevent additional fuel loss. It uses the word additional because the rate of leak at APU fuel is insignificantly low.

The checklist says similar not symmetrical (highlighted).


Why are the cockpit controls of airplanes so complicated?

I would argue that the controls of an aircraft are not complicated, but rather that they are simply foreign to you.

In the vast majority of cases, the various controls in the aircraft do one thing:  Turn something on, or turn it off.  They are quite simple actually, but what makes it appear complicated to you is that there are so many of them.  As you learn about the airplane (especially modern ones) you will see that these individual controls are grouped together by system, in a way that actually makes pretty good sense.

To put it in perspective, let's say that you had never seen a laptop computer before:

This...  thing (remember, you've never seen one before!) has 94 buttons on the top alone!  It has all kinds of little jacks and plugs on the outside.  It has things that pop open from the side.  It's just...  complicated.

Then someone points out that most of the buttons on the top are buttons that you can press to make a letter show up on the screen.  This takes much of the mystery out of the complicated mess on the top, but then as you start to learn more you figure out that some of the less commonly keys are grouped together by function.  You have the arrow keys, the function keys, the key modifiers, the CD controls...  Suddenly it doesn't seem quite so complicated anymore.

You complain to your friend that the monitor (hey, we've learned a fancy new word!) is a little too small, and they suggest that you hook up an external monitor.  We can do that??  Of course, that's what this port is for.  Cool, now that's one less mystery.  This goes on, and before long you can even pick up a different brand of laptop, with different buttons and pretty much figure it out on your own.  Before long...  the mystery is gone and it's just a laptop computer.

And so it goes with airplanes.  Newer airplanes are being designed with fewer switches and gauges.  Take a look at the progression in the Falcon 900 series aircraft:

Falcon 900B

Falcon 900EX

Falcon 900EX-EASy

Each iteration has fewer and fewer controls and instruments.  You may even say that they look less complicated.  However, I can assure you that each newer model has far more capabilities and a lot more to learn in order to understand and safely fly the airplane.  They each have the full capability of the model before it, along with additional features and more to learn.  Certain systems no longer have switches or dials and you have to look through different menus in order to access them.

Appearances... can be deceiving.


Advantages in using a flight sim to prep for a private license?

I'd advise against "flying around aimlessly".

Even if it is a simple, routine flight between two nearby airports, fly it fully, and try to fly it as professionally as possible (can you keep your heading to within +/- 3 degrees? can you keep your altitude spot-on?)

Another good exercise is to do all your navigation planning in detail (each heading for a certain number of minutes), then try to take off, and using nothing but the compass and stopwatch, find out how close you get.  (and when you end up off-course, figure out where you went wrong!)


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

I believe that it is an Israeli Aircraft Industries Westwind. This is based on the mid-set wing and the 5 windows on each side.

Image source: https://upload.wikimedia.org/wikipedia/commons/thumb/f/ff/IAI_Westwind_%282323424886%29.jpg/300px-IAI_Westwind_%282323424886%29.jpg


Is there any difference between "EMERGENCY LANDING" and "FORCED LANDING"?

Not all forced landings are emergencies, and not all emergencies are forced landings! (See below)
In general, the term "Emergency Landing" is a superset which covers a bunch of different scenarios where a landing is not quite to plan. Such as

Forced landing due to mechanical failure. Note that a forced landing can absolutely be at an airfield. It can also be in a literal field.
Precautionary landing, such as where continued flight is possible but inadvisable
Ditching in a body of water
Belly landing due to inoperable landing gear

A forced landing can also be one where the pilot is forced to land due to military interception, which is not always an emergency.
This is all covered in great detail here

The FAA also publish some useful information on this subject which repeats much of the above information, reproduced below for clarity

Types of Emergency Landings
The different types of emergency landings are defined as
follows:
• Forced landing—an immediate landing, on or off an
airport, necessitated by the inability to continue further
flight. A typical example of which is an airplane forced
down by engine failure.
• Precautionary landing—a premeditated landing, on
or off an airport, when further flight is possible but
inadvisable. Examples of conditions that may call for
a precautionary landing include deteriorating weather,
being lost, fuel shortage, and gradually developing
engine trouble.
• Ditching—a forced or precautionary landing on water


How is the RAT on the Airbus A320 family manually deployed?

There is a pushbutton on the overhead panel in the hydraulics section to manually deploy the RAT:

5 RAT MAN ON pb
The flight crew may extend the RAT at any time by pressing the RAT MAN ON pushbutton.
Note: The RAT extends automatically if AC BUS 1 and AC BUS 2 are lost. (refer to 1.24.20).

(A320 FCOM - Hydraulics - Controls and Indicators)
There is another button on overhead panel in the EMER ELEC PWR section, which will also deploy the RAT and connect the emergency generator:

1 MAN ON pb (guarded)
AUTO: When the following conditions are met:

AC BUS 1 is not electrically supplied.
AC BUS 2 is not electrically supplied.
Aircraft speed is greater than 100 knots.

.

The RAT extends.
The blue hydraulics system drives the emergency generator.
As soon as the emergency generator electrical parameters are within tolerance and the landing gear is retracted, the emergency generator is connected to the aircraft network.

Pressed: This selects manual RAT extension. Emergency generator coupling occurs 3 seconds after the RAT supplies the emergency generator.

(A320 FCOM - Electrical - Controls and Indicators)
Here is the full RAT deployment and emergency generator logic from the FCOM:


Can one purchase a Cessna 182JT-A although it has not yet been certified?

They did have an engine out failure about a year ago which set everything back a bit.  They've had it at Osh a couple of years now.  Two years ago they were saying around the end of '14 beginning of '15.  Last summer, they were saying months.  If you're really curious, I would talk to the manufacturer in Kansas.  Dealers really aren't part of the FAA approval process...

I wouldn't read too much into the range calculator.  I would imagine that they would be adjusting numbers numerous times before release as they get more data.


There are regular flights between Singapore Changi and Sydney operated by FedEx Express. Here is a list of past flights from Singapore to Sydney (FDX9075):

(flightaware.com)
There are regular flights on Monday, Tuesday, Wednesday and Saturday. You can see that there was no flight on Monday, 05 October. This is likely because the aircraft coming from Sydney (FDX9077) diverted back to Sydney on Monday:

(flightaware.com)
I don't know the reason for the diversion, but as you can see, there is an MD11 enroute to Singapore right now. It is therefore likely that the same aircraft will depart Singapore back to Sydney later today as FDX9075, possibly carrying your parcel.
Update: Return flight is in the air right now:

(flightaware.com)

To answer your question about using other airlines:
Normally, FedEx does not use other airlines for international flights. They operate their own network of flights with their own airline FedEx Express. In these special times, it is quite possible that things have changed1, but I could not find anything official.
FedEx is however using a lot of other airlines for local transportation. They are called FedEx Feeder airlines. Wikipedia has list of them. They only operate regional aircraft (most of them ATRs).
1 Normally, a lot of air cargo goes on passenger aircraft (below the passenger deck). Due to the COVID pandemic, passenger travel is significantly reduced right now, which means more cargo needs to be transported on dedicated cargo aircraft than before.


John K and Koyovis's answers are both correct. However, as a former pilot of the UH-60 and a mechanical engineer here is a simpler version.

A helicopter must be balanced. If the front is much heavier than the tail, then it can't fly safely as the nose is too low. If the tail it too heavy, then the same. The point of balance is called the center of gravity.

The tail boom on a helicopter is very long. If you were to add one pound to the tail vs one pound to the nose, the pound on the tail would more impact due to the length of the tail boom. In engineering this is called the "moment arm" By canting the tail boom, the tail rotor actually lifts the tail boom. There isn't that much lift, but since the tail boom is so long it has a pronounced effect. This gives the aircrew more latitude in loading the helicopter. With the extra lift provided by the tail rotor, we can put more load (troops, fuel, etc.) behind the rotor mast and still keep the center of gravity in acceptable limits.


At what age does a regularly maintained airframe most commonly start needing frequent repairs?

Not an aircraft owner here, but based on the AOPA article Tips on Buying Used Aircraft, the one thing that stands out is to negotiate a much lower price if the aircraft is close to its time between overhaul (TBO).

  [Let's say] you are purchasing a 1977 C-172N for \$40,000. The TBO for this aircraft is typically 2000 hours, and costs roughly \$20,000; or half the value of the aircraft. If the aircraft you are considering buying has 1800 hours on the engine, you need to expect to spend an additional \$20,000 on the aircraft in your first 200 hours of ownership. Knowing this, it would be in your best interest to negotiate a lower price for the aircraft.

Depending on you where you will be flying, you may be required to install ADS-B by Jan 2020. If the aircraft you are buying is not equipped, then that's something to add to the list of things to buy. (What is ADS-B and who needs it?)

There are also these related posts:

What are the typical facets of ownership costs, for a single engine aircraft?
Is there any limit by FAA on the age of aircraft to be operational?


Is it legal to make emergency landing on roads?

In the USA, when an airplane is in the air, it is governed by Title 14 of the Code of Federal Regulations, also known as the Federal Aviation Regulations (FARs). FAR 91.3(b) gives the pilot in command authorization to deviate from any flight rule necessary to meet an emergency: if that pilot needs to land on a road to meet an emergency, it is certainly legal as far as the FAA is concerned.

In fact, for private flights in small airplanes, the FAA doesn't bother much at all about specifying where you choose to land. There are no regulations about it at all.

The FAA's authority to regulate stops when the gear touches the ground, though. The road, or field, or waterway, or whatever you might be landing on usually belongs to someone or some government entity. Government entities often have laws against landing aircraft in certain places like roads or waterways, but just as often, they don't. It depends on which government. But in all cases I have ever seen, if such a regulation exists, so does an exception that starts, "except in cases of emergency...."


Could flaps replace spoilers by deflecting more than 90°?

The BAe Jetstream 31 is one of a few aircraft that had a "lift dump" flap position after touchdown. It is not "more than 90°", but it is quite effective.

(Jetstream 31 Lift Dump in action; YouTube)


What are the disadvantages of a delta wing biplane design?

The main benefit of biplanes is that the lift can be distributed across both wings. This provides more lift with less wingspan and places less load on each wing. Less load means the materials can have lower strength. This was very important in the early days of aviation, when engine power, materials, and weight were much more limited.

The major downside of a biplane is aerodynamics. The wings interfere with each other, causing drag. While structural bracing between the wings can reduce weight, it also adds more drag. This means that a single wing will almost always perform better, and modern materials and designs should make that possible.

A biplane configuration does not make much sense for delta wings. The main drawback of a biplane is drag, but drag increases with the square of velocity, and delta wings are best in high-speed flight. While delta wings have lower wave drag, they have higher viscous drag due to the large surface area. A second delta wing will add more area, increasing both wave drag (from the cross section) and viscous drag (from the surface).

Configuration of the aircraft also becomes problematic. Most aircraft with delta wings tend to be fairly flat, allowing lower area and therefore lower drag. The closer the wings are, the more they will interfere. The further apart they are, the more structure is needed, either in a larger fuselage or in structural braces, which increases weight and drag.


What are some "FAA approved" simulators for home that I can log time on?

Read this answer from AOPA, especially the last 2 paragraphs.
https://www.aopa.org/news-and-media/all-news/2004/november/flight-training-magazine/since-you-asked

Logging sim time
Dear Rod:
I'm a private pilot just a couple of days from taking my instrument checkride. My CFI and I have had discussions about simulator hours. He logs them but does not include them in total time. I've just closed the Federal Aviation Regulations/Aeronautical Information Manual for the umpteenth time and after reading about maximum of 20 here and a credit of 100 there, I'm confused. Maybe you can explain. What is the point of taking advantage of a sim if the hours logged don't count toward my TT?
Thank you,
Mark
Greetings Mark:
Simulator hours can count as training time, but are not considered "flight time" and can't be logged in the flight time (total time) column of your logbook. They can, however, be logged in the "Flight Simulator" column of your logbook. If your logbook doesn't have such a column, then make one using the letters "FS/FTD" which stand for flight simulator/flight training device.
Regarding simulator time counting toward your total time, consider that the commercial certificate allows 50 hours of simulator time to be counted toward the total aeronautical experience requirement of that rating -- see FAR 61.129(i)(1).
Thus, you could meet the commercial requirements of 250 hours of aeronautical experience with 200 hours of flight time and 50 hours of simulator time.
Even if simulator time didn't count toward the total aeronautical experience requirement of a rating, it might still count as training time. For instance, 2.5 hours of appropriate simulator time can be credited toward the total training time required for the private pilot certificate (FAR 61.109 i).
Now, read the federal aviation regulations carefully before running off and trying to log cross-country time in a simulator. The regs specifically state you must meet certain "flight time" requirements in an airplane. You're not getting away with packing a lunch and sitting in front of a simulator for six hours in hopes of logging this as a cross-country flight to meet the private pilot cross-country requirements.
(Yes, I heard of a case where someone actually tried to do this. Perhaps the ruse unraveled when the FAA examiner asked, "Hey, what kind of airplane is a Combat Flight Sim?")
Also keep in mind that you can only log simulator time when there is an appropriately rated instructor providing dual instruction. In other words, solo time in a simulator can't count toward your private or commercial certificate or instrument rating.
And it goes without saying that a simulator must be approved by the FAA for it to be used as a FS or FTD. (Sorry, but Combat Flight Simulator is only approved for shooting down other simulators, not flight training.)
Rod Machado is a flight instructor, author, educator, and speaker. A pilot for 34 years and a CFI for 30, he has flown more than 8,000 hours and owns a Beech A36 Bonanza. Visit his Web site.

FAA regs on simulators
https://www.faa.gov/about/initiatives/nsp/ac/
List of FAA approved simulators, and the aircraft type simulated
https://www.faa.gov/about/office_org/headquarters_offices/avs/offices/afx/afs/afs800/afs810/media/FAA_Approved_Airplane_ATDs.pdf


What is this squawk 7777 target at an altitude of 62,700' over Germany?

This is a military test transponder, not a real aircraft. The callsign GAFTT08 stands for German Air Force Test Transponder 08. When you zoom in on the map, you can see the reconstructed position move in a pattern around the fixed true position:

(adsbexchange.com)

As far as I can tell, the military does not publicly say what exactly they are doing here. The only sources I could find are from forums:

  GAFTTxx = German Air Force Test Transponder

(flugzeugforum.de)

  German Air Force Test Transponder. So not an aircraft, not a drone. Don’t know why it is online all the time, but it is. Sometimes over Würzburg, sometimes over Ingolstadt.

(forum.scramble.nl)

Additionally, the squawk code of 7777 is used in Germany for fixed test transponders according to Wikipedia (thanks to ymb1 for pointing this out):

  7777 US, Germany, Belgium, Netherlands: Non-discrete code used by fixed test transponders (RABMs) to check correctness of radar stations (BITE)

(List of transponder codes - Wikipedia)

This is also confirmed by the following ICAO definition:

  Code 7700 is reserved for recognizing an aircraft
  in emergency. (Codes 7711 to 7717 and 7721 to 7727 are
  reserved for SAR operations and code 7777 for monitoring
  the ground transponder.)

(ICAO - SSR CODE ASSIGNMENT SYSTEM, emphasis mine)


As a contractor for an FBO, is it okay for us to transmit Internet signals right above the tarmac?

There are no FAA restrictions on setting up WIFI transmitters and receivers at an airport in the United States.

WIFI transmissions do not interfere with the frequencies used by airplanes for operational purposes.


It's the component of the aerodynamic force perpendicular to the direction of the air flow, the aerodynamic force being the reaction of the wing to the relative wind.


Do small civilian aircraft have autopilots?

Many small, light aircraft are equipped with an autopilot today. They can range from very simple autopilots, without altitude selector and so on,

Source, ST SYS 30, $ 12,000

to advanced systems with altitude selector, automatic trim and so on.

Source, Bendix/King KFC 225, $ 15,000 - 42,000

And with this GPS, feeding the autopilot with data, it has the abilities of an airliner.

Source, Garmin® GTN™ 750, $ 17,000

You have to know, the systems in the general aviation industry are getting better and better. Of course they are way below the complexity of the avionics of airliners, but the features are the same if not more.

For example: A captain of an airliner has to review or change the flight plan with the FMC, respectively MCDU on Airbus, a not very straight-forward device to control the plane.

Of course, the FMS has a lot more capabilities than a GA GPS, but one of it's primary features is the input of the flight plan. And in that, from the usability-view, the Garmin® GPS has the better solution: An all-in-one navigation device with touchscreen input.


What does the * (asterisk) next to radio and nav aid frequencies on Jeppesen charts refer to?

It means that this frequency is not always available (not always staffed). From the Introduction to Jeppesen Navigation Charts:

8 - Indicates the service is part time.

And further below:

Navaid boxes include the navaid name, identifier, Morse code, and frequency. A letter "D" indicates
DME capability with an asterisk indicating part time.


Is responding to an internet forum post looking for a scenic flight "holding out"?

This is almost certainly holding out: someone asks for a flight and you agree to provide it. You weren't going to make the flight until the person asked, and you're receiving compensation for it. This is from the Bobertz interpretation:

  Absent a bona fide common purpose for their travel, reimbursement for the pro rata share of operating expenses constitutes compensation and the flights would be considered a commercial operation for which a part 119 certificate is required.

The Haberkorn interpretation that acpilot mentioned is somewhat similar to your scenario in that it talks about using Facebook but with the difference that the pilot advertises for passengers, rather than passengers asking for pilots. You can read the whole thing and although the FAA said they can only comment on specific cases, not general examples, they did make clear that they're concerned about situations where:

  there is an interest in carrying passengers with whom there is no previous personal relationship and that the offer to accept passengers is being made to the general public

But even if you already know the individual, it's probably still a commercial operation.


What do the different colors of weather stations indicate on SkyVector?

Colors
At present1, they mean (image source):

For more details, please see this description.
Fill-ins
These are called sky/cloud coverage.

Image Source

1 From SkyVector:

The color is controversial because the FAA is making the NWS swap the
colors for VFR and MVFR. When the new aviationweather.gov becomes the
current aviationweather.gov, we'll change our colors to match.


I've had this happen a few times on aging C152's and in all cases I have been able to simply push it against the airflow enough to pull it closed. On a PA28 with the door the other side of the cabin from the pilot seat, this wouldnt be possible. Not that I have experienced it in a PA28, but I might ask a passenger to attempt the same (hard push followed by a hard pull).

Some things to note:

There's no massive danger of a door slightly ajar, so waiting until  out of a critical phase of flight is advisable (ie, climbed to cruise, clear of any ATZ)
In all but one time I had another competent pilot sitting next to me who can keep an eye out and even hold the controls for a few seconds. Just one reason flying with other pilots is nicer than flying alone.

However, I would suggest that every situation is different. The most important thing is, as always, Aviate first. A light aircraft is unlikely to be critically unable to continue flying with a door ajar. Don't get distracted by something like an ajar door - fly the aircraft.

If in any doubt, land as soon as possible and fix the problem. It would, I think, be acceptable to call "Pan Pan" if you feel you need to expedite a landing.


You will need a fixed landing gear and a braced wing to keep your mass at your target of 40 kg. Expect a maximum L/D of not more than 10, maybe even 8.

You say that the flight mass will be 100 kg. The weight will be 980 N. 1/10 of that is 98 N. To arrive at a power from that will need a few more heroic assumptions. Your wing loading is probably 12 to 15 kg/m² and your lift coefficient around 1.0. This equates to a flight speed of 15.5 m/s (= 56 km/h). I assume a propeller efficiency of 70%, so your power for straight flight will be 2.2 kW.

For decent take-off performance, add 1.5 m/s climb capability at an air density of 1.1 kg/m³. The extra power to climb with those 1.5 m/s at 15.5 m/s and 70% efficiency is another 2.2 kW.

The sum is 4.4 kW which is 5.9 HP. Running the engine at this power level means 54% of maximum power. Make sure you have a gearbox which reduces prop RPM to not more than 2000 in order to make those 70% realistic. The wing will need to have about 8 m² area and the tail another 1.6 m². Will that all fit within your 40 kg?

I expect that 80 kg is a more realistic empty mass. Now the wing will measure 11 m² and the power demand climbs to 3 kW for level flight and an extra 3 kW for climb. Total power will be 8 HP or 75% of maximum power. Ask yourself how long the engine does this and how big your radiator needs to be in order to avoid overheating.


Is it true that there are VOR/DME and/or TACAN stations in the oceans?

There are no ship-based VOR's or TACAN's specifically dedicated to transatlantic flights. Transatlantic flights navigate using the inertial navigation system and GPS.

TACAN's are used on board naval ships for military aircraft to find their way to the ships, but this is typically not for flights across the ocean.


Can an armed door be opened from outside an airliner?

This depends on the aircraft:

DC9, MD80, B727, B737

On some (especially older model) aircraft doors such as the Boeing 737 for instance this is directly dangerous, since the slide is attached on the inside by hand with the means of a girt bar to the aircraft.

There is hence no way to open the door without the slide going off should it be armed. There is a helpful notice in red on the outside to "stand clear" when the red banner is crosses the window, the indication that it is armed. Judging by the space required and force the doors have, this is still most probably very dangerous idea that should not be used unless absolutely necessary.

Source

Airbus, B757, B767, B777, MD11, E-Jets

On more modern aircraft, this is safe: opening the door externally will push the arm handle to the disarmed position before proceeding to open it. This is for instance the case on all Airbus aircraft.

This video provides a nice example.


Why doesn't the Concorde have any wing fences?

The main purpose of the wing fence is to prevent the boundary layer thickening in the wing due to the spanwise flow observed in swept wing, as can be seen below.

Image from fuckyeahfluiddynamics.tumblr.com

This is the reason for having wing fence in aircraft such as Mig-25- to avert stall and improve stability. In case of highly swept wing like the Concorde, this is not required as the mode of generation of lift is different- using vortex lift.

Vortices over the Concorde wing, Separation in three-dimensional steady flow, ONERA

In fact, there is a significant cross flow, as can be seen in the following image:

Flow above the Concorde Wing, Separation in three-dimensional steady flow, ONERA

Due to this, the wing fences are not required in case of highly swept wings like Delta and Ogival wings (as in Concorde), where separation leads to vortex lift. Mig- 25 wings, though highly swept, was neither of these- the wing generated lift by conventional manner.


Is there a convention for type of switch used and where?

I can't give you a 100% correct answer, but I'll try as best as I can, having some experience with much smaller aircraft (even than the TBM850):

As far as I know, there are no strict conventions for this and this is why you see most aircraft types equipped with their own panels and cockpit design.

You always have to keep in mind that aircraft manufacturers put most of their engineering efforts into designing aircraft concepts for a specific market and then casting their ideas into an actual airframe that fits all the systems that are needed to operate the aircraft.

Allmost everything else (engines, landing gear, avionics, A/C, lights, APU, steering, braking and anti-skid systems etc.) is developed and manufactured by external suppliers with the aircraft manufacturer responsible for adapting and orchestrating all the systems.

This might lead to the aircraft manufacturer simply using already available switch assemblies or only slightly modifying the suppliers' reference designs for panels in the actual aircraft.

IMHO, this is easily recognizable when looking at the cockpits of (especially older) aircraft where there was no concept of the cockpit as a whole. Whatever switch assembly was needed was just somehow installed into the panels.

As Boeing's 707 was a great success, its cockpit design (at least partly) found its way into the 707s successors/derivates/siblings 727 and 737. This lead to the 707 setting the cockpit design paradigms for following (Boeing) aircraft.

Also, from a pilot's point of view, there are some semantic aspects about choosing a switch that 'feels right'. For example:

push-buttons to start an automated process
korry-type switches for switching automatic systems on or off or for on-off switches that might be controlled automatically (And therefor show their status; Airbus uses these a lot due to their cockpit philosophy)
toggle switches for everything that needs an on-off type switch on low-level without other systems needing access to it (for critical switches with safety cap as seen in the 737 overhead panel)
rotary switches for mode selectors
potentiometers for everything that is finely controlled by the pilot
rockers maybe for mode selection between two modes where neither of both is just "off"

are very intuitive to me. This might be training or just experiences from everyday life, but I understand what they are doing even before having read the manuals thoroughly, which makes it easier to remember which switch does what.


What are these markings under the passenger door?

They appear to be alignment marks for the passenger loading bridge (PLB) and air stairs. Some airlines choose mark their aircraft and bridges, in order to prevent damage to the aircraft door due to misalignment of the bridge or air stairs.

On the PLB, there will be a corresponding mark on the floor, at the edge.

The two lower marks would be used for air stair alignment (i.e., when a PLB is not available).

Note the marks at the edge of the bridge in this photo (the position of the alignment marks are not standardized and are carrier specific):


Can this helicopter/wrecking ball combo remain airborne?

EDIT

Huge apologies to one and all, in my first version of this answer I mistyped 184 as 84, and then proceeded to do all my calculations based on that.  This is the corrected version.

Also, huge thanks for all the up-votes and comments. I'm so glad it's not just me that is enjoying this question immensely.

The radius of the ball in the image is 21 pixels. The length of the fuselage is 184 pixels, which is 50' 7.5" (15.43m) according to widely available statistics. Hence, a pixel represents approximately 84mm

So, the radius of the ball is 21 x 84 = 1764mm = 1.764m

And the volume of the ball (if solid) is 23.0 m³.

For it to be liftable by the helicopter, using Pilothead's quote of 9000lb (4082kg), the density would need to be 177.5 kg/m³. Mild steel, at 7,850kg/m³, is way too heavy. Expanded polystyrene has a density of 28-45kg/m³, so that would be feasible.

However, if the ball were not solid, and were made of mild steel, the total volume of steel permissible would be 0.52m³. At an outer radius of 1.764m the inner radius must be at least 1.750m to keep the volume of metal down to 0.52m³, so the ball would only be 14mm thick (9/16") and would only cost about $3,300.

So, let's try Titanium (darling of the aircraft industry). With a density of 4,506kg/m³, we could have a volume of 0.90m³. That would allow a thickness of 24mm (15/16"). However, the price of that much titanium would be $229,500 (today's prices - 6 years ago, it would have been over a million US dollars).

Aluminium, however, has a density of 2,700kg/m³. So now we could have a volume of 1.51m³, allowing a thickness of 40mm (1 9/16"), and would only cost $9,360

Pumice, at 250kg/m³, would allow a volume of 16.33m³, allowing a thickness of nearly 0.6m (23½"). That would be very sturdy, I reckon. I can't find a price for a solid lump of pumice that size though.

Incidentally, the people in the picture are also about 21 pixels tall, making them around 1.76m (5'9") tall.

This has now taken up about 3 hours of my time, which like all other hours up to now, are hours I'm never going to get back.  However, it has been so much fun.

FURTHER EDIT

Following a suggestion from Jules in the comments, I've discovered Lithopore 75-150, which is a ridiculously low density foamed concrete.  This could give us the magical solid sphere that we want, with sufficient strength to squish multiple personnel without significant damage to itself.  At the 75 kg/m³ end of the range, we could possibly even have some spikes, and a non-negligible cable mass too.

More maths and engineering research required.....


What happens when lightning strikes an airplane?

Since the aircraft is not grounded, the physics are the same as with a car that gets struck by lightning. The aircraft's skin will be charged, but very little current will be induced in internal parts in the process. The outer skin will act as a Faraday cage and protect the inner parts from the electric field.

This is greatly helped by a metal structure. Composite aircraft parts need a copper mesh over all external surfaces to give them sufficient electrical conductivity. The terminals of that mesh must be connected to the metal parts of the structure to make sure that all parts will have the same electrical potential in case of lightning strike.

However, the ionized air caused by lightning will leave burn marks on the surface, and an inspection of the affected part and the electrical equipment is advisable.