What is the "one-in one-out" FAA rule for IFR traffic landing or departing at an airport without a tower or at an airport with a closed tower?

Several sections of the AIM give guidance on this. It is explicitly stated that only one aircraft at a time is given a departure clearance. It is implied that there would be no approach clearances until the departing aircraft’s position is known by ATC.

  4−4−1. Clearance

  a. A clearance issued by ATC is predicated on known
  traffic and known physical airport conditions. An ATC clearance means
  an authorization by ATC, for the purpose of preventing collision
  between known aircraft, for an aircraft to proceed under specified
  conditions within controlled airspace.

  5−2−6. Departure Restrictions, Clearance Void Times, Hold for Release,
  and Release Times a. ATC may assign departure restrictions, clearance
  void times, hold for release, and release times, when necessary, to
  separate departures from other traffic or to restrict or regulate the
  departure flow.
  1. Clearance Void Times. A pilot may receive a clearance, when operating from an airport without a control tower, which contains a
  provision for the clearance to be void if not airborne by a specific
  time. A pilot who does not depart prior to the clearance void time
  must advise ATC as soon as possible of their intentions. ATC will
  normally advise the pilot of the time allotted to notify ATC that the
  aircraft did not depart prior to the clearance void time. This time
  cannot exceed 30 minutes. Failure of an aircraft to contact ATC within
  30 minutes after the clearance void time will result in the aircraft
  being considered overdue and search and rescue procedures initiated.

  NOTE−
  1. Other IFR traffic for the airport where the clearance is issued is suspended until the aircraft has contacted ATC or until 30 minutes
  after the clearance void time or 30 minutes after the clearance
  release time if no clearance void time is issued.

  5−5−4. Instrument Approach

  b. Controller.
  1. Issues an approach clearance based on known traffic.

  5−5−4. Instrument Approach a. Pilot.
  1. Be aware that the controller issues clearance for approach based only on known traffic.


What parameters to focus on when constructing a wing for turning?

Strength, ability to withstand the G forces of turning.  Secondly, having a stall Angle of Attack as high as possible.

A low aspect ratio wing with a very thick airfoil is a good candidate, such as the ones designed by Hugo Junkers and seen on Fokker planes of 100 years ago.  These work very well for slow, turning flight.

Another candidate would be the delta.  Strong and easy to construct, deltas offer a very high stalling AOA, making them very good at turning tightly.

Deltas have more drag for a given amount lift than a straight wing, so the first candidate will stay in the air for a greater amount of time, the second may give a thinner helix.

Good reading articles can be found in Air and Space magazine:  "What the Red Baron never knew" and "The Perfect Airplane Wing".


At 353.9 m/s:
 your phugoid mode is unstable as well as degenerated (Poles lie on real axis and has damping ratio 1).
while at 235.9 m/s:
phugoid mode has become stable as well as oscillatory and has some damping and frequency.

so, nothing has been canceled its just phugoid mode poles changing positions.
you can check it clearly by plotting root locus using rlocus command on MATLAB.


Why do spoilers seem to be slightly activated during take off?

Spoilers lower lift and increase drag on the side where they are deployed. Symmetric spoiler deployment, therefore, is for slowing down. Asymmetric deployment not only creates a (small) rolling moment, but primarily a yawing moment which helps to counteract the adverse yaw created by ailerons, especially at the high lift coefficient at takeoff and early climb.

Spoiler deployment increases pressure ahead of the spoiler due to the slowing of local flow ahead of the obstruction caused by the spoiler, and it creates a local flow separation at and behind the spoiler, which in turn lowers the local pressure. Only the first effect lowers lift, but both create drag. The main effect of a limited spoiler deflection, therefore, is to increase drag.


Where is the inlet for the APU on a Fokker 70/100?

You can check this report from the BFU.

I reproduced the image of page 12 of the report here

Obviously, the exhaust is in the middle of the picture and the inlet is on the top right part (trapezonidal shape)


In which countries can I fly an FAA compliant Part 103 ultralight?

Although the formula for compliance is somewhat different, in general you can fly an ultralight that is compliant with FAR 103 in Canada as a Basic Ultralight.  The major difference is it has to be registered (not certified in any way, just registered with call letters), and you need an Ultralight Pilot Permit to fly it.


This looks like a flutter system of a representative wing section. Plunge is the vertical degree of freedom as shown in the diagram below (the other degree of freedom is pitch, $\theta$ or $\alpha$ in your assignment). You also have structural damping terms, which are omitted in the diagram.

Image ref: https://www.researchgate.net/figure/Sketch-of-airfoil-aeroelastic-system_fig1_313820106


How does a pilot switch from IFR to VFR mid-flight?

You simply tell ATC your request:

  A: DEXPL, request cancel IFR.
  R: DEXPL, roger, report VMC.
  A: DEXPL, we are VMC.
  R: DEXPL, IFR cancelled at 20. Squawk VFR, approved to leave frequency.


Why do modern jetliners provide Thrust Reversers at all in their design decisions?

There are  a couple of reason for the presence of thrust reversers:

To reduce wear on the brakes.

To provide a margin of safety (for example in wet conditions).

In 1995, NASA carried out a survey on airlines Why Do Airlines Want and Use Thrust Reversers?. The results of the survey, though dated, give an indication of presence of thrust reversers.

The main reasons given by the airlines was to provide additional stopping force in adverse weather and to reduce brake wear.

The first question posed to the airlines was "why do we have thrust reversers?" (...) The number one reason given by the airlines was to provide additional stopping forces in adverse weather conditions (i.e. on wet, slushy or slippery runways). The airlines also use thrust reversers to reduce brake wear and to provide directional control and additional safety margins during an aborted takeoff (RTO).

According to the airlines, the thrust reversers were there because they wanted them there. This meshes with the fact that the thrust reversers are not used in calculating stopping distances during certification.

When the airlines were asked who they perceived as the principal organization behind the installation of thrust reversers on commercial transport aircraft, the airlines responded that they were. That is, the
aircraft manufacturers put the systems on board the airplanes because the
airlines want them.

Most airlines recommend using the thrust reversers early in the landing to minimize braking.

The airlines weigh the economic benefits of using the thrust reversers (and engine wear) against the use of brakes and the results seem to indicate a significant amount of money saved by using thrust reversers. The report notes:

... the savings in brake system costs due to the use of thrust reversers was estimated. The results show that the total yearly savings in brake system costs is about \$8.6 million, or an average of about $17,700 per airplane for airline 17.

Though this is almost certainly an exaggeration, the numbers indicate that the airlines would definitely prefer thrust reversers over increased braking.
In the end, the reverse thrust can be important in reducing the runway requirements in case of a wet runway. In 1999, a Qantas 747 overran the (wet) runway in Bangkok and landed up in a golf course. Qantas has used only idle reverse thrust rather than full power during the landing as per the operational procedure. The official accident report included data from Boeing 747-400 Flight Crew Training Manual, which stated that,

Immediate initiation of reverse thrust at main gear touchdown and full reverse thrust reduce brake usage, thus minimising brake temperatures.
To minimise wear of carbon brakes, minimise the number of brake applications. Use maximum reverse thrust and operate the autobrakes normally.
The importance of establishing the desired reverse thrust level as soon as possible after touchdown to minimise brake temperatures, tyre and brake wear, and to reduce stopping distance on very slippery runways cannot be overemphasised..

As a result, Qantas revised their operational procedures, requiring full reverse thrust. Brake wear is an important reason for having thrust reversers. For example, in Airbus A380:

... unlike the thrust reversers on most airliners, including the Boeing 747 jumbo, they do not stop the aircraft in a shorter distance than brakes and spoilers alone. They do, however, take some of the strain off the brakes and are useful if water or snow makes the runway slippery.

The BAe 146 lacks a thrust reverser; it makes do with an airbrake in the tail and spoilers all along the wing for braking (which should give an indication of how much spoilers is required to eliminate reversers). The 146 got away with that because of the low touchdown speeds (~90 kt) and the huge airbrake, which is not avialble in the other commercial airliners. For the same amount of spoiler area in other commercial airliners (in absence of airbrakes), they (spoilers) would occupy most of the wing surface, increasing weight and complexity. Some Embraer ERJ 145s also lack thrust reversers (they are optional).


What currency requirements exist specifically for Commercial and ATP pilots that a Private pilot wouldn't know about?

Autoland currency

If equipped with autoland, the flight crew will have some requirement to use the system, or else autoland operation in real CAT III weather, where autoland is required, will be prohibited. For many types, this also applies to the aircraft itself.

Currency is satisfied by conducting a successful autoland in any weather, so in periods of good conditions, autolands may be practiced during normal CAT I or CAT II approaches. Crews can also do this in the simulator. All autoland use is reported to the company so they can track currency.

It varies by airline policy and aircraft type, but typical requirements may be one every 30 days, one every 90 days, or 2 or 3 landings between 6 month sim checks.

Some airlines will put a movable placard on the flight deck as a reminder to crews what the status of the aircraft is, e.g. you will see "CAT II" or "NO AUTOLAND" when the system is faulty or not current.


How does a delta wing deal with supersonic boundary separation?

1. Aeroelasticity
Unlike a tailplane, a delta wing is more rigid due to its much bigger chord and multiple spars, so control reversal due to aeroelasticity isn't a special concern.
Big subsonic jetliners typically lock the outer ailerons at high speeds. Concorde featured a similar function for the outer elevon, but only if $V_{MO}$ is exceeded by 25 knots as a safety measure (flight manual page 09.01.03).

Concorde's structure also makes it much more resistant to the distorting forces of supersonic flight than aircraft built before her. (...) If Concorde gets substantially above its design speed, the outboard elevons are automatically neutralized, so that no twisting is possible (heritageconcorde.com).

2. Transsonic separation
Delta wing aircraft rely on thin airfoils (vs. blunt) where the pressure gradient is more forgiving. And due to the bigger chord, the elevons deflection doesn't result in a big camber change as happens on the smaller tailplanes. The big sweep angles of delta wings also make the airflow see thinner airfoils, making the transition to supersonic easier.
3. Supersonic separation
Not an issue since the shock wave moves to the trailing edge at supersonic speeds.

Source: https://history.nasa.gov/SP-367/f87.htm

Must reads:

Why is the coefficient of drag for straight wings at supersonic speeds lower than for swept wings?
What is the pressure distribution around a supersonic wing?
What causes the reduction in speed across the shockwave?
Why does supersonic flight detach airflow from a wing?
How does aileron reversal work?


Are there any guidelines on airframe age and metal fatigue in light aircraft?

The short answer is no, age or airframe hours alone are not something to be concerned about on these light Cessnas.

A 1975 C172M I flew for work had about 20,000 hours, or more, on the airframe (can't remember exactly), largely in low level flight at or below 500 ft AGL, often in high winds, moderate turbulence, low level wind shear, etc., and flight including plenty of relatively high G maneuvering, and lots of crosswind landings far exceeding the demonstrated crosswind component. Years ago, before my employer bought it, someone managed to flip it over on it's back while taxiing. The thing has also had several bird strikes.

As an A&P mechanic, I have thoroughly inspected this airframe, to the level of an annual/100 hr inspection. Keeping in mind the airframe's age and history, my inspections included paying special attention to items of structural interest such as spar and strut attach points, control surface attach points, firewall, spars, etc. I have no concerns about the structure of this particular airframe, and I've trusted my life to it over 840 flight hours.

I have quite a bit of experience maintaining a number of single engine Cessna models, including quite a number of older, well worn individuals. I cannot recall encountering any structural issues that were due to metal fatigue alone. Most of the structural instances I can think of would be due to one time events such as a hard landing causing a firewall to wrinkle or crack. Some, such as cracked gear strut castings—in a U206G for example—are relatively common on such airframes that are used for rough, backcountry flying. I suppose that could be chalked up to a type of metal fatigue, but I don't think it is what you are concerned about with this question. Such items are a known issue and won't cause you to fall out of the sky.

The real age-related concerns regarding structural issues will be corrosion. Obviously, corrosion can occur over a short time frame, but give an airframe an extended stay in a harsh, corrosion conducive environment and it may fare more poorly than in a "good" environment. That being said, there are plenty of great airframes from the '50-'70s that have been hangered or sitting in barns in humid climates that are in excellent shape. The same will probably not be true of the engines if they sat unused, but the airframes may be in great shape.

Every airframe is different, and a thorough pre-buy inspection will be necessary to ensure that yours does not suffer from some major structural issue. But age and hours alone should not be of real concern.

I would not hesitate to buy a high-time, vintage Cessna airframe merely on account of those factors.


Why does the MiG-25 have silver-coated panels?

As you have pointed out yourself, the Silver is there because it is highly reflective. The panels around the engines were coated with silver to prevent the heating of the fuselage around it. According to this document,

  The engine bays each incorporated heat shields coated with a 30-micron layer of silver (5 kg/11 lb per  aircraft), which absorbed 5 percent of the heat and represented a more cost-effective solution than gold or rhodium, though these  metals were tested.

The panels basically trapped the heat within the engine bay, which is then cooled using boundary layer bleed air from drain slots between the air intake sides and airframe sides.


How is an aircraft with a stabilator trimmed?

Trim is simply a force that offsets the neutral position of the control surface. On aircraft with mechanical controls it is provided aerodynamically via trim tab, but it can also be provided by springs, hydraulics, or simply by adding the selected offset in the fly-by-wire computer. Since F-16, F-18 and F-22 are all fly-by-wire, the last option is most likely.

In fact, all these fighters are aerodynamically unstable, which requires using “cooked” controls where centred stick commands the computer to maintain straight flight and the computer then adjusts the stabilators accordingly, doing small corrections all the time since the flight path would quickly diverge without that. So there is no trim in the traditional sense at all.


Engine Oil Consumption limits part of certification?

Indirectly yes, the FAA engine certification guidelines can be found here. The FAA does not really care how much oil you burn so long as you specify it in the documentation and the installation can provide enough to safely run the engine with some margin on top of that.

  Paragraph 23.1011(b)

  The engine requirements for oil quantities and temperatures are
  established by the engine manufacturer and may be found on the Type
  Certification Data Sheet or in the engine installation manual. The
  airplane installation must not cause the engine limits to be exceeded
  under normal operations.

  Paragraph 23.1011(c)

  Paragraph 23.1011(c) requires that, “The usable oil tank capacity may
  not be less than the product of the endurance of the airplane under
  critical operating conditions and the maximum oil consumption of the
  engine under the same conditions, plus a suitable margin to ensure
  adequate circulation and cooling.” In other words, there needs to be
  enough oil (usable supply) to allow the engine to consume the usable
  fuel. This should be substantiated by a quantitative analysis. In
  addition, a suitable oil quantity margin for system circulation is
  necessary for all engine installations. The oil system should be
  capable of maintaining the engine within its operating limitations
  (i.e., oil temperature with the minimum oil quantity provided for
  circulation). Cooling tests do not need to be performed with a low
  usable oil supply provided the oil is properly cooled at all oil
  levels.

(To avoid copying all the text here) The document explains how to calculate these numbers as well under Specific Oil Consumption (SOC) and further under Single-engine Installations/Multiengine Installations. The content of Paragraph 23.1011(d) as well as Paragraph 23.1011(e) discuss feeding and pumping the oil around as needed.


Why would an airport use an L/R runway combination and a second number instead of L/C/R?

There is flexibility on the numbering of parallel runways based on a number of factors as described in FAA advisory_circular/150-5340-1J -page 4 (see excerpt below). In the case of KPHX for example, there is the main terminal between runways 8/26 and 7R/L-25R/L.  Also, when approaching from the east the threshold for runway 25L is a significant distance from the threshold for runway 25R (about 2500 feet inset).
I would guess that minimizing possible pilot confusion factored into the decision not to have a "center" runway designation.


Turboprop vs turbofan (in regional aircraft)

Turboprops are more efficient, because they accelerate more air by less to create the thrust, and therefore the air carries away less energy , since kinetic energy is proportional to square of velocity. This is true at all altitudes.

Neither engine benefits from altitude. They do benefit somewhat from the colder temperatures up high as heat engine efficiency is proportional to the ratio of high and low absolute temperature. But the main benefit from flying high is that drag is proportional to density, so in the less dense air up high the aircraft flies faster with the same thrust. This is true for both engine types.

The key difference is that turboprops are limited by true airspeed as when the propeller tips get close enough to speed of sound, shockwaves start to form that create massive drag (and a lot of noise) and the efficiency declines fast. In contrast the inlet of a turbofan modifies the pressure field around it so that the air always hits the fan the same speed independent of the speed of the aircraft, converting the extra velocity to pressure instead. Therefore turbofans maintain their efficiency to higher true airspeeds.

Since the low density at high altitudes also increases true stall speed, the true airspeed restriction of turboprops creates an altitude restriction too.

So for short routes where there is not enough distance to climb up as high, the higher efficiency of turboprops is better and turboprops are used. But for longer routes where you can climb up above about 30,000 ft and fly most of the route there, the increase in efficiency due to lower density and resulting higher true airspeed offsets the lower efficiency of the turbofan engines and they become better.

Plus flying faster reduces other costs. For short routes the aircraft spends larger fraction of time on the ground loading and unloading and refuelling, so flying faster has less effect and you want to minimise the fuel burn. But for longer routes flying faster means the aircraft can make more trips in a given time and the crews can make more trips and therefore the fixed costs spread over more passenger miles, which makes it worth flying faster even if it means using a bit more fuel. That again requires using turbofan engines.


The VFR on top clearance is often given with a block of altitudes.  Such as this from the reference document "Maintain VFR-on-top at or between six thousand and one zero thousand.”  With this clearance the pilot can fly any altitude they want within this block of altitudes without having to contact ATC for further clearance.  This flexibility can be useful with the conditions are such that the clouds come and go as you fly along.  So if you are cruising along at 6500 and encounter a cloud and need to climb to 8500 to maintain clearance you just do it.  No need to contact ATC and wait for them to ensure they can clear you higher while the clouds keeps getting bigger and bigger in the windshield.

Even if there are not cloud issues, the ability to change altitudes may be useful in seeking an altitude with more favorable winds.


Is there similar result between simulation and reality?

Yes, usually

Simulators are pretty accurate, at least for the specific things they're programmed to measure and account for.

For example we have a pretty good idea how airflow works, so airfoil/wind tunnel simulation is very accurate. We also have quite good ideas of how materials react, flex, break etc, and can model them pretty accurately.

However

No simulation is 100% accurate: there is always potential for things in the "real world" to happen in a way we either didn't account for, or weren't expecting.

For example sometimes manufacturing flaws mean a material breaks in a way we weren't expecting, or an external influence changes the way something happens. We also don't have a 100% understanding of aerodynamics under all conditions.  This is why we still need real-world testing. There are also circumstances we've never encountered and therefore can't be certain of: eg aircraft are designed to handle around 150% of the force of the strongest known/experienced turbulence, but we can't be truly sure that this hypothetical 150% turbulence would act as "regular" turbulence, merely 50% stronger

In short: yes, the results will be similar, but they will not necessarily be identical, depending on exactly what you are testing.


Can I fly a STAR (standard terminal arrival route) if I can't maintain the minimum speed for it?

According to the FAA's Instrument Procedures Handbook, chapter 3 (p. 3-16):

Pilots may have noticed that minimum crossing altitudes and airspeed
restrictions appear on some STARs. These expected altitudes and
airspeeds are not part of the clearance until ATC includes them
verbally. A STAR is simply a published routing; it does not have the
force of a clearance until issued specifically by ATC. For example, minimum en route
altitude (MEAs) printed on STARs are not valid unless stated
within an ATC clearance or in cases of lost communication.

So unless ATC explicitly, verbally assigns you a minimum airspeed, you don't have to maintain it. If they do assign one and you can't maintain it, you can simply say "unable" and request to fly it at a lower airspeed. If ATC can't allow that for some reason (like spacing) then they'll likely vector you instead.
That means that if you are simply cleared for the STAR with no specific airspeed it's not a pilot deviation to fly it more slowly than the airspeed on the procedure.
I have no idea how likely or not it is that ATC would allow you to fly the STAR you have in mind. That would depend heavily on traffic, and things could change at any time.


Does the FAA construe FAR 91.225 to prohibit aircraft w/o electrical systems w/o ADS-B-out from flying above 10,000' MSL unless below 2500' AGL?

The content in this FAA link indicates that the answer to the question is "no".

  Under the rule, ADS-B Out performance will be required to operate in:

  Class A, B, and C airspace.
  Class E airspace within the 48 contiguous states and the District of Columbia at and above 10,000 feet MSL, excluding the airspace at
  and below 2,500 feet above the surface.
  Class E airspace at and above 3,000 feet MSL over the Gulf of Mexico from the coastline of the United States out to 12 nautical
  miles.
  Around those airports identified in 14 CFR part 91, Appendix D.

  The ADS-B Out rule does not apply in the airspace defined in items 2
  and 4 above for any aircraft not originally certificated with an
  electrical system or that has not subsequently been certified with
  such a system installed, including balloons and gliders. For
  additional requirements for using the exception for item 4, please
  refer to CFR 91.225 section (d) for the requirements.

(italicization added)

(as of Feb 24 2020, the quoted web page had last been updated on August 22, 2019)


Why was pitch angle protection not active in the CRJ 200 during the crash of Sweden Air 294?

I am intimately familiar with that incident.  The airplane only had FDR recording the left PFD so they don't really know what was showing on the right one based on FDR.

The only pitch angle protection is the shaker/pusher. They didn't get that slow.
The AP runs off the Flight Director it's selected to.  This is normally the FD of the pilot flying.The  autopilot kicks off when the pitch attitude exceeds a certain angle (I forget what it is).  The capt was PF so the AP would have been coupled to the left flight director.
There is no yoke force mechanism for disconnecting the AP.  If the autopilot was in Pitch Mode and the PFD suddenly goes nose up it'll drive the elevator and follow up with trim inputs to keep the A/P servo loads in limits.  But in any case the AP will be in ALT Mode, the mode you are in once you capture and are holding an altitude.  It pitches to hold the altitude.  If the pitch indication goes nose up, but the altitude is not changing, it won't kick off until the pitch attitude exceeds the auto-disconnect attitude. Until then the AP will be holding whatever pitch attitude keeps the selected altitude.

The scenario was, the capt was sitting there, it's black outside, like black black, up and down, no lights anywhere.  He noticed his own PFD going "blue" (all sky).  Either he kicked the AP off or it would have kicked itself off when that PFD exceeded the auto kickoff attitude.  The airplane is just sitting there minding its own business in level cruise still.

Read the report here.  Capt panics and goes into tunnel-vision mode, and thinks they are in a zoom climb so he shoves the stick forward, putting them into a "bunt" (negative G pushover) in the pitch-black-in-every-direction sky.  The FO, (it was assumed his PFD was functioning normally but there was no FDR for it) would meanwhile have seen all brown on his PFD by this time (and on the Standby Attitude Indicator, but I don't think they ever looked at it).

So there you are as copilot: capt is all confused and has you both hanging in your straps with speed building and crazy roll attitudes to boot.  Your PFD shows all brown - diving.  It's black outside, everything that was on the floor is on the ceiling, and neither of you has a horizon; left side is all blue with the high pitch chevrons and display de-clutter happening, and the right side is all brown with the low pitch chevrons and de-clutter.  The noise is building to a crazy roar and with no horizon (all blue left and all brown right) it's hard to tell where the wings are relative to the horizon.  They both became hopelessly disoriented.

The did several rolls on the way down and hit the ground close to Mach.  There were no large pieces.

In my opinion there was a basic breakdown of a fundamental IFR skill.  When the Capt's PFD went weird, with no physical sensation to match, and no altitude and speed deviations to match, the FIRST reaction should be to do nothing, and cross check with the opposite PFD and the Standby ATT.  It's a case of the old saying, "Don't just do something, sit there".  Seeing the right PFD and the Standby working normally and the airplane's behaviour agreeing with what they showed, the capt should have transferred the AP to the right FD and made the copilot the Pilot Flying, turned off that display, and they would've carried on their merry way.

So bottom line is if the Capt had done nothing, they'd have been fine.  Even once the AP auto-disengaged due to the erroneous pitch attitude, the airplane itself would have continued level flight as trimmed.


What is "company compensation fuel" and "pad fuel"?

Company Compensation Fuel
This is a term, which seems to be used by Korean Air. They define it on their website:

▶ Company Compensation Fuel
fuel to minimize abnormal flight occurred. Based on this, fuel consumption performance is modeled for a certain period of time, and based on this, the amount of fuel repeatedly consumed excessively compared to the flight plan is added.

(koreanair.com, translated by Google)
So this is fuel added based on the airline's experience (hence company) for typical fuel use on a given route.
Pad Fuel
I have never heard this term and Google also does not find anything related to aviation. Is it possible this was a translation? If so, could you add the original term and where you heard about it?


What does " X miles in trail, runway 25R cleared to land" mean?

The controller's telling Southwest 1565 it's cleared to land (otherwise they would use the other aircraft's identification), and by the way there is an airplane of a certain type coming up behind and to take that into consideration in the event that Southwest 1565 was thinking of spending too much time on the runway after landing instead of promptly getting out of the way.

That kind of comment added to the landing clearance suggests that the airplane behind is a little closer than usual, or is going significantly faster, or it's just really busy with airplanes spaced at minimum separation, and Southwest should expedite clearing the runway.


Is a biennial flight review valid for any airplane category?

Yes.  61.56(c)(1) calls for "an aircraft for which that pilot is rated."  The reg does not require a review for each category/class.

And as further confirmation, AOPA's Pilot's Guide to the Flight Review specifically states:

  The satisfactory completion of a flight review allows you to exercise
  the privilege of pilot in command in all categories and classes of
  aircraft on your pilot certificate.


Can I fly under a Military Operations Area (MOA)?

Yes you can. The MOA floor, 10000ft in this case, is the lower limit of any restrictions a MOA imposes. Otherwise there would be no point in assigning a floor to MOA (or any other airspace for that matter)
See FAA AIM Section 4. Special Use Airspace


What exactly happens to kinetic energy in the turbulent layer on an aerofoil?

Energy is transferred from the moving airplane's skin into the air in the turbulent boundary layer. Because the layer is turbulent, all the momentum vectors for every little parcel of air entrained in the layer are pointing in random directions with some uniform component (in the direction of the plane's travel) superimposed.
Thus the air in that layer gets vigorously stirred up, and since air has viscosity, the stirring action gets fairly quickly transformed into frictional heat. So after the plane has departed out of the picture, the turbulence and net motion in its wake get dissipated and the air is left a little warmer than it was before the plane flew through it.


How else can snowy/icy conditions disrupt airport operations?

There are multiple ways by which snow can affect the operation in an airport.

Snow (and ice) in runway can affect takeoff by absorbing energy and can impact the aircraft after being kicked up by tires.
During landing, snow or slush in runway can reduce the deceleration rate by reducing friction coefficient, sometimes causing hydroplaning.
The runway length requirements in case of dry and wet conditions are different. This means that some aircraft cannot use the available runway in case of snow/wet conditions.
The requirements to clean the runways (and taxiways) continuously means that the flights will be delayed.
The snow may reduce the visibility of runway and terminal visual markers.
Ramp operations may be affected due to snow/ice.
Beyond a certain level of snow, the airports have to be closed as the aircraft cannot takeoff/land.
Also, it will be snowing in areas around the airport too. This means that there will be difficulty for people in reaching airport in the first place.

Also, see the FAA advisory circulars AC 150/5200-30C - Airport Winter Safety and Operations and AC 91-6A, Water, Slush, and Snow on the Runway


How do engineers make sure UAV don't land on their front propeller?

Due to center of gravity limitations, it would be impossible for any type of aircraft to be loaded so that the front became the heaviest part. The aircraft would not be able to fly.

These UAVs are meant to crash land and DO land on the front propellor. You can do a Google search and see multiple videos showing the “break apart” landings they are designed to do.

Here are some landing videos:

Puma landing 2

Puma landing 1

Coast Guard Conducts First Unmanned Aircraft System Deck Landings


What is the pressure in a civil aircraft fuselage at flight ceiling?

The pressure inside the cabin is usually more than the outside pressure at the cruise altitude. The pressure altitude (ISA altitude with the same pressure) inside the cabin of civil aircraft is called the equivalent effective cabin altitude or normally cabin altitude.

As the aircraft climbs, the cabin altitude is gradually raised so that it reaches around 8000 ft for the aircraft cruising altitude of ~40000 ft. This level is maintained at flight ceiling too.

Source: www.flyertalk.com

The pressure is around 0.75 bar inside the cabin. The outside pressure at this point is around 0.2 bar, resulting in a pressure differential of 0.56 bar. This pressure differential causes stresses on the aircraft body.

Source:ecnmag.com

In addition to the stresses, pressurization - de-pressurizatoin cycle can cause fatigue in the windows.

As reducing the cabin altitude will improve the passenger comfort, newer aircraft tend to have lower cabin altitudes. For example, the Boeing 787 has a pressure altitude of around 6000 ft and the Bombardier Global Express jet has a cabin altitude of around 4500 ft.

This is achieved by the use of advanced composite materials, which allow a higher pressure differential have excellent fatigue properties compared to the metals. As a result, the windows of newer aircrafts are considerably larger than their predecessors.

Image: Boeing


Why are W, S, N, E highlighted on a flight management computer?

N, E, S, W is definitely used for entering lat/long coordinates. On the Airbus graphic in the question, you can see the pilot has entered their starting latitude and longitude with N and W.

But why are they highlighted? I'm going to guess and say it has to do with the transition between old-style numeric nav computers and "modern" FMS. Old style IRS only had a numeric keypad like this Concorde unit:

(Source)

and you can see that N, E, S, W is entered on the 2, 6, 8, 4 keys. So instead of typing "3253.9N" on the CDU you'd hit "325392". You'll still find these numeric keypads today on some forgotten corner of the overhead panel for who knows why, even on a 777.

I think the squares are a cue for the old time pilots that you can't enter a N coordinate by hitting 2, you have to hit the N key, and it also helps them find it.


What are the advantages and disadvantages of ducted fans in designs such as the Airbus E-Fan?

An answer to your question can be found here.

Advantages of ducted fans would be:

reduced noise
Better containment of broken blades
protection of ground personnel when the engine is running
Smaller size than a comparable propeller
They look like a fancy jet engine. This is probably the main motivation of Airbus for their use on the E-Fan.

For almost all aircraft designers, their drawbacks have weighed more heavily:

Less efficiency, because a smaller mass of air is used for propulsion
Additional friction drag and weight from the shroud

The highest propulsion efficiency is possible with a large, slow-spinning prop. Once flight speeds approach the speed of sound, the propeller has to become smaller to avoid supersonic propeller tips, and then the shrouded design becomes more attractive. Electric airplanes so far are not fast enough to profit from this effect. I would be very skeptical of the increased thrust claim - both efficiency and thrust of the E-Fan ducted fans are lower than what a well-designed propeller can offer.

The addition of the shroud only increases thrust when compared to the naked fan, but the fan is a poor replacement for a decent propeller at low speed.


How much different are civilian and military aircraft autopilots?

There is no civillian autopilot for an F-16, because there are no non-military F-16s. Ditto with the F-117 or or B-1 or B-2, so who knows what unique modes those autopilots have for their uniquely military missions (i.e. dropping bombs or low level terrain following). However, when the military aircraft has a non-military equivalent (KC-10/DC-10, KC-135/B707, C-40/T-43/B737, C-21/Learjet, T-44/C-12/KingAir, etc) then the autopilots are generally identical.

Any differences are more likely to be found in FMC software rather than in the Autopilot, and those differences would be very specific to each aircraft & its mission.


Does the phrase ".78/280/250" have a standard meaning to an airline pilot, in the context of a long descent?

It means the profile is based on descending at 0.78 Mach until the IAS increases to 280 knots, at which point that speed is maintained to 10,000', at which point the aircraft slows to 250 knots for the remainder of the descent until it's time to slow & configure for landing. That 0.78/280/250 is a very standard profile for descent planning in the 737, although variations such as 0.80/320/250 or 0.76/250 are certainly possible.


When do you contact ATC when departing from a non-towered airport into class C controlled airspace?

This is spelled out clearly in CFR 91.130:

  (c) Communications. Each person operating an aircraft in Class C airspace must meet the following two-way radio communications requirements:

  (1) Arrival or through flight. Each person must establish two-way radio communications with the ATC facility (including foreign ATC in the case of foreign airspace designated in the United States) providing air traffic services prior to entering that airspace and thereafter maintain those communications while within that airspace.

  (2) Departing flight. Each person—

        (i) From the primary airport or satellite airport with an operating control tower must establish and maintain two-way radio communications with the control tower, and thereafter as instructed by ATC while operating in the Class C airspace area; or

        (ii) From a satellite airport without an operating control tower, must establish and maintain two-way radio communications with the ATC  facility having jurisdiction over the Class C airspace area as soon as practicable after departing.

You can try contacting them while on the ground, but if you can't raise them, you have to do it as soon as you can after take-off.


Would atmosphere floating inside an airship be counted towards the mass of the airship?

Yes, but not for buoyancy.

Does this mean that below the hydrogen cells sits an empty volume of air equal to roughly 58% of the volume of the cells?

Yes, exactly.
When calculating the lift produced by the interior of the airship, the gas with lower density compared to outside air (hydrogen) produces lift while the internal air of equal density to outside air has no influence. It simply cancels out. While hydrogen displaces air of higher density, creating lift in the process, this internal air displaces outer air of equal density. So for lift that internal air can be disregarded.
However, when maneuvering this air does count. It increases the inertia of the ship, both when changing direction and when accelerating or decelerating. To this air the airship designers even counted the outside air which is influenced by the motion of the ship. An airship in motion continuously displaces air at its bow and lets it flow together again at the stern. The air is thus given an impulse which - as the product of mass and speed - can be described as an additional mass of the airship at this speed. In the case of an elongated body, this additional mass in the direction of travel is small in relation to the mass of the displaced air, but is of the same order of magnitude in case of lateral or vertical movements. In case of rotational movements, the inertial forces and moments of the gases within the airship envelope are added. To make it easier to calculate the forces on the airship hull, the concept of virtual mass was introduced. This virtual mass depends on temperature, altitude and speed. Although this technique allows a simple mathematical description of the effect near an operating point, it can only be generally applied with additional effort. If you are interested in the actual values: NACA-Report 184 contains tables and correction factors for the calculation of virtual mass.

I ask because water in a ship's hull makes it heavy and sink.

Because this water would displace air which is lighter than water and makes the ship float. This comparison only works when air would be replacing hydrogen in the gas bags. See the empty volume in the airship as akin to an external tank which is added to a ship and submerged. Its weight would be carried by the water. The air-filled volume in an airship is needed to have space for the gas bags to expand into without disturbing the aerodynamic shape of the hull.

Why wouldn't air in an airship make it heavy and fall to earth? Or would it?

Because this air displaces air of equal density. It cancels out in the buoyancy calculation.


What class is the airspace at KGCN when the tower is closed?

It may be an error on the chart, it should be either Class D or Class G, but it depends...

If the ATIS reverts to ASOS when the tower is closed, the airspace can be Class E. If ATIS/ASOS is not available, then the airport has to be Class-G. I would stick with the chart supplement here:

June 1 through September 30th, the tower is manned from 1300Z to 0300Z and is Class D. October 1 through May 31 the tower is manned from 1400Z to 0200Z and is Class D. All other times it is Class G meaning they do not have ASOS available. (AWOS is available by phone).

So according to the chart supplement, if the tower is not occupied the airspace is Class G.


What happens to en route flights when a major earthquake etc. destroys facilities?

This is a valid and good question. The answer is all the different entities will work together to solve the issue.

It's called a system wide event, be it a natural disaster or otherwise.

  [It's an] event that affects a flight and a sufficiently wide area that all alternate routes and airfields briefed during pre-flight preparation have become unavailable. Ground facilities such as navigation beacons and air traffic services may also be affected.

A somewhat recent example is the closure of many airports in Japan after the 2011 Tōhoku earthquake and tsunami.

As you can imagine, this only affects a tiny portion of flights that are too near the center of the event. The ATC, flight-crew, and company (airline) personnel will all work together. Even a simple thing such as using the internet access aboard planes to gauge the situation on ground from the different news feeds can be used.

Best case scenario is there would be enough fuel to turn around and exit the radius/area of the event toward the most suitable location. There usually will be enough fuel, and using the performance manuals the flight crew can make their plane very efficient. Airlines balance fuel and time using what's called a Cost Index, in this case, they will push to save on fuel and forget time (flying slower but farther).

In conclusion, the affected are few, the events are far between, each flight will be very unique, and this is where human ingenuity, training, and decision making skills come in.

For the facilities part, there are a few posts on that here, for example see: Is there an ATC radio backup? Even if the radio is down, handheld radios can be used. Most of the aviation systems have many built-in redundancies.


How much can falling down due to a stall influence the angle of attack?

In AF447 the falling motion most definitely affected the angle of attack. Due to the fact that the pf did keep the stick pulled back for all but the last few seconds of the fall the aircraft was so steep that, although the aircraft was falling at a slight pitch up, angles of attack actually reached as high as 60°.

The descent was so steep that the air was passing over the pitot tubes at such an angle that it was reading below 40 knots, although the plane was moving far faster then that. The computer required that the airspeed be of a certain value to consider the aoa plausible so the stall warning stopped sounding even though the aoa was between 30° and 60° during the fall. When it hit the water the forward ground speed and the vertical speed were both 107 kts.

As far as why the pilot did not realize he was stalled, that's the question of the century. Much effort has been put into figuring that out, and there are numerous things that are at play. But in the end I don't think anyone has come up with a satisfactory answer for that.

If you want to dig into the causes of this crash and get a good understanding of Airbus systems in general I highly recommend this book and it's companion website. The author is uniquely qualified and gives the most thorough explanation yet is not as technically challenging as reading the BEA report.

All of the numbers mentioned in this answer come from the linked book.


How can you tell what position the flaps are in whilst on a commercial aircraft?

If you are seated behind the wings, but close, you can usually see black markings (thick line and a number) near the inboard side of the engine pylon which indicate their extension. Some might not be visible when the wing is in cruise configuration.

Same goes for leading edge slats, only you'd need to be seated near the overwing emergency exit to see those.

I've personally seen them on both Airbus and Embraer jets (no recent flights on Boeing airframes so can't confirm if they mark them too).

(Source)


Have there been any incidents caused by an inability to shut down an engine?

Qantas Flight 32
Enroute to Sydney, Engine Number 2 of the A380 disintegrated explosively. The shrapnel of the explosion destroyed many systems, including a hydraulic system, the anti-lock braking system, flaps and electronic controls.
After emergency landing, the pilots were unable to stop engine number 1, because the controls had been destroyed by shrapnel. Emergency services had to douse the engine until flameout was achieved.

Source


How does wind affect the airspeed that I should fly for maximum range in an airplane?

My answer was rather concise first, and I got the impression that I need to elaborate the question first. The question is about the best airspeed for maximum range. With wind. Best range means you cover the most distance while the wind is carrying the plane with it. If you have a headwind, the longer you stay aloft, the more you are carried back, so you better hurry up. With a tailwind, it helps to slow down because now the wind is helping you to cover even more distance.

But how much? We need to pick that particular speed where the change in fuel consumption just balances the change in speed over ground. I always found that easier to explain with gliders, and there you can really observe which polar point is best. Just picture yourself as an observer on the ground who sees the plane fly by in the distance. If you plot a line with the combination of positions and altitude, there must be one flight speed that produces a line where the flight path angle is the shallowest. This is the desired optimum. That has only little to do with optimum L/D - this is just one other point you can find with a sink speed polar. And it happens to be the point for best glide in still air. But there is so much more that humble polar will tell you, if you look at it the right way.

With powered aircraft you need to pick the polar point where your fuel flow is lowest for the given speed over ground. Basically, you fly like the glider and add enough power to stay at the same altitude. That is all the difference. User2168 has answered that part already with a graphical solution.

OK, now back to gliders. Please look at the plot below which shows airspeed on the X axis and sink speed on the Y axis.

The solution is graphical: You start on the X-axis at the point which corresponds to the wind speed and put a tangent on the sink speed graph. Where the tangent touches the sink polar (blue line), the plane flies at the best L/D for that given wind speed. Move the starting point to positive speeds for headwind and to negative speeds (not shown here) for tailwind. If the term "best L/D" is already reserved in your mind, please read this as the "best polar point". It is really the same.

Since User2168 has beaten me to the graphical solution, I will add an analytical solution.

For powered flight things become more tricky, because thrust changes with speed. To simplify things, we can say that thrust changes over speed in proportion to the expression $v^{n_v}$ where $n_v$ is a constant which depends on engine type. Piston aircraft have constant power output, and thrust is inverse with speed over the speed range of acceptable propeller efficiencies, hence $n_v$ becomes -1 for piston aircraft. Turboprops make some use of ram pressure, so they profit a little from flying faster, but not much. Their $n_v$ is -0.8 to -0.6. Turbofans are better in utilizing ram pressure, and their $n_v$ is -0.5 to -0.2. The higher the bypass ratio, the more negative their $n_v$ becomes. Jets (think J-79 or even the old Jumo-004) have constant thrust over speed, at least in subsonic flow. Their $n_v$ is approximately 0. Positive values of $n_v$ can be found with ramjets - they develop more thrust the faster they move through the air.

Now for fuel flow: This goes up and down with the power output of the engine. Again a simplification, but it helps to get to grips with the problem and gives useful results. This lets us re-formulate the problem as: At what airspeed do I have the best ratio between power and ground speed?

Mathematically, we want to fly with $\frac{P}{v_w+v}$ at the lowest possible value. $P$ is the power, $v_w$ is the wind speed and $v$ the airspeed. To express the thrust behavior over speed, I break P up into a product of a constant $K_S$, the throttle setting $\delta$ and the speed like this: $K_S\cdot\delta\cdot v\cdot v^{n_v}$. Here is the general solution, pasted as a PNG to save me all the typing in the editor:

Please note that implicitly the lift coefficient is on both sides of the equation. To solve it, you need to do it recursively, until speed and lift coefficient match. I took this form because of the similarity to the general form at still wind which can be found in many performance books. This here I didn't find anywhere, and it took me a while to figure it out. Thank you, Lnafziger, for the excellent question! It gave me a chance to learn something.

Now I have put the results into a plot. In order to eliminate the aircraft-specific parameters, it shows the ratio of $c_L$ with wind over $c_L$ without wind. The plot is metric, but will work for all units if you use the same units for wind speed and air speed.

To give an example for the application of the correction factor: If you are flying in a 20 m/s headwind and your best range speed at still wind is 50 m/s (approx 97 kts), the $c_L$ needs to be 70% of the $c_L$ at still wind for piston-powered aircraft. This makes your corrected airspeed 60 m/s (v is proportional to $\sqrt{c_L}$), and now the recursive nature of the formula rears its ugly head. At 60 m/s, the correction is only 77.5%, so we need to do a few loops until we arrive at a point where the airspeed and the correction factor match. In this example, this would be 57 m/s or 110 kts in case of a piston-powered aircraft.


What is the difference between rate of climb and climb gradient?

The climb gradient is the percentage of the rise over run (100% if you are climbing at 45 degrees) that your aircraft is climbing at while the rate of climb is the speed at which you are climbing based off the airspeed and climb gradient (given in feet per minute).


Where can I find the correct POH for my Cessna 152?

Strictly speaking the POH/AFM is specific to your airframe as it generally contains the weight and balance information which will be unique to your airframe as it is equipped. Thus you should always reference the POH that is in the plane for the most accurate source of information.

For example here is a nice scanned PDF of a POH for a C152. You should confirm that the numbers match those in the POH for the airframe. As long as they do you can use it for reference. The POH does not need to match for the specific year but it does need to match for the given aircraft configuration and setup in regards to the engine and performance data as well as any data related to things like extended range tanks etc.


For military helicopters, what is the typical fatigue life of the main rotor dynamic components?

The fatigue life of helicopter dynamic components is determined by the manufacturer based on the number of hours flown and as such, varies from helicopter to helicopter.

In general, life of the dynamic components are less than that of the helicopter structure. The life of the dynamic components depend on the fatigue loads (the magnitude and load spectrum) and the materials used.

So, the same helicopter involved in more demanding operations (civil vs. military) will have less life. Actually, during development, the fatigue life is determined in number of cycles, which is then converted to flying hours based on the expected flying pattern. Also, the materials used make a difference, with composite materials having better fatigue resistance compared to metallic blades.

The life of the UH1 MRB (Main rotor Blade), for example is around 2500 hours. For UH60 MRBs, similar values have been quoted for metallic blades. However, Studies by MBB (Now part of Eurocopter) indicate that the composite blades under normal loading have a fatigue life of around 4000 hrs (AGARD conference Proceedings No. 297, Helicopter Fatigue Life Assessment).

The life of other dynamic components, e.g. pitch horn, pitch link etc. are usually around 1000 hours. However, with little data available in public domain for helicopters under service, it is hard to say with any certainty.

It should be kept in mind, however that these values are only indicative as all dynamic components are periodically checked using NDT methods and decision on their continued service is solely based on the results of these tests. For example, any damage to the bearing in the pitch links will result in their replacement. Also, the development of Health Usage Monitoring Systems (HUMS) means that most of the H/c manufacturers are moving away from a life based approach to a health based approach, resulting in variation in life of individual components.


What kind of drone might be able to fly so high that it "operate(s) outside national boundaries"?

Normally, controlled airspace ends at 60,000 ft (Flight Level 600). Airplanes flying higher than that would be operating outside of controlled airspace. Currently, there is no internationally agreed definition where national airspace ends. However, aircraft flying higher than 60,000 ft (18,288 m) could claim to fly outside of national boundaries.

There are several airplane designs capable of flying above that height:

The venerable Lockheed U-2 should be first on this list, even though it is sometimes loaded with sensors such that it can climb above FL600 only at the end of its mission.
Next would be the Lockheed SR-71, but none are still flying.
Both the Myasishchev M-17 and the larger M-55 also qualify.
But most likely the photo has been taken by a RQ-4 Global Hawk which officially flies up to 60.000 ft high.

Even though those designs fly at a height where 98% of the atmosphere is below them, they are still firmly flying within it, technically or otherwise.

There are several more which can fly much higher, but those are research aircraft which do not take photo trips into Iran. Of course, there can still be a classified design of which we don't know yet.

EDIT: Now it is reported that satellite tracking has identified the source of the photo as USA 224, a spy satellite launched in 2011. Using the shadows in the picture as a sun dial, the exact time could be determined and the corresponding satellite was traced down by amateur satellite hunters.


How did Airbus fit 6,340 gallons more fuel into the A359?

Bloomberg says minor changes to "piping and venting" made the capacity available. It came from previously unused space in the center fuel tank.

The a359 center tank filling point is not at the highest point in the tank, so it needs a vent in order to use that space. Without the vent, the tank airlocks and no more fuel will flow in.
Piping refers to changes to that tank's inerting system, designed to prevent explosion of fuel vapor in the tank. Inerting has been required for wingbox center tanks ever since TWA800. See Leeham for more detail, search the page for Update2.

As to why this is not part of every a359, it is operating cost. The regional variant has a 260t MTOW and therefore lower landing and navigation fees. The 280t MTOW needed for the ULR will be available from 2020 on the standard model, so there is very little difference otherwise. If you order the ULR you can paper change it to a regional, though I don't know anyone who would.

Leeham also has an interesting article on how seating (passenger weight) has to be limited to get maximum range from the ULR.


Is the mach number of an aircraft measured with respect to stagnation speed of sound?

The Mach number is defined with respect to the static speed of sound.
Note however that the Mach number is not measured by somehow measuring the TAS (True AirSpeed) and dividing it by the known speed of sound because this would require knowing the static speed of sound, which is temperature dependent. Instead, we derive the Mach number from the ram air pressure $p_0$ measured by the pitot tube and the static air pressure $p$ measured by the static port:

$$ M^2 = \frac{2}{\gamma - 1} \left[ \left( \frac{p_0}{p} \right)^{(\gamma - 1) / \gamma} - 1 \right] $$
[...]
The velocity can be determined from
$$ V^2 = a^2 M^2 = \frac{a_0^2 M^2}{1 + \frac{\gamma - 1}{2} M^2} $$
but this requires knowing either the static speed of sound $a$, or the stagnation speed of sound $a_o$.

(MIT Lecture Notes on Subsonic Pitot Tubes)
You can see in the velocity equation that the Mach number $ M = V / a $ is defined via the static speed of sound $a$ instead of the stagnation speed of sound $a_0$.
The above equations are only valid for subsonic flow. If you want to determine the Mach number in supersonic flow, you have to solve the following equation iteratively:
$$ M \approx 0.88128485 \sqrt{\left( \frac{p_0}{p} + 1 \right) \left( 1 - \frac{1}{7 M^2} \right)^{2.5}} $$
(Wikipedia - Mach Number)


The wing was swept to move the center of lift back, closer to the center of gravity. When the design of the DC-1 was advanced to a point where the center of gravity became clear, a redesign of the wing-fuselage intersection would had been more effort, so the outer wing panels were swept back a little.

From this website by Jeff Lucker:

  the unique and characteristic swept wing of the DC-3 was an attempt to
  keep the wing in its original location as the center of gravity moved
  toward the rear.

When Douglas produced new variants (DC-2 and DC-2 sleeper, a.k.a. DC-3), they kept the proven layout.


How did the USS Vincennes misidentify an Airbus aircraft?

tl;dr We don't know.

The US Government has not made enough information available to answer this question. The official Iranian and US reports contradict each other. Inofficial accounts of sailors on other USN vessels operating in the vicinity at the same time contradict both the official US report as well as statements made by Vincennes commanding officer.

There are several possible explanations, many of which have not been officially acknowledged, and probably, the real cause will be a combination of multiple factors. And some of those are easy to address:

User Interface Design: the target tracking system recycles target designations. Shortly before the shootdown, the system had assigned a new target designation to the aircraft and recycled the old designation for a fighter operating over 100 miles away. When the CO asked what the classification for the target designation was, the answer was "fighter" and that it was descending, which was correct for that target designation, but was actually for a completely different aircraft now.

Don't Do That!

No access to current flight plans: the crew only had access to the standard regular schedule, but not to updated flight plans, e.g. including delays or cancellations. On the day in question, the flight was delayed by over half an hour.

Assets used for monitoring mixed-use airspace should be equipped with civilian radios and be in contact with ATC.

Ergonomic Design: the lights were so dark, and flickered every time the weapons were fired, that the crew assigned to monitor the airspace couldn't read the printed out flight schedules.

Better lighting. Or, put the schedules / flight plans into the computer. Even better: integrate them into the target tracking system.

Timezone confusion: the flight schedules were printed out in Iranian time, but the ship's time was Bahrain.

One word: UTC.

Missing Equipment: the Vincennes had no possibility of using civilian frequencies (other than the international distress frequency 121.5), so they had no way of knowing that the "unresponsive" aircraft was in fact in constant communication with ATC.

See #2. Note that directly after the incident, the US Navy did install tunable VHF radio on all ships in the Gulf.

Wrong Frequency: of the 10 attempts to establish contact with the aircraft, 7 were made on military frequencies. Obviously, being a civilian aircraft, the Airbus had no way of hearing this.

Train crew to remember that failure to respond to a military frequency does not imply hostile intent, especially since civilian aircraft won't even be able to respond.

Speed confusion: when the Vincennes adressed the unidentified aircraft, they gave the aircraft's speed in groundspeed as 350kts, but the indicators in the aircraft would have read 300kts indicated airspeed. Since the speed was wrong, the pilots may have thought the calls were made to a different aircraft operating in the vicinity whose speed was closer to the one in the call.

Make it clear in your transmission that you are talking about groundspeed.

A year earlier, another USN vessel was (mistakenly) hit by Iraqi missiles. Her commanding officers received official Letters of Reprimand, effectively destroying their careers, stating that defense of the ship is the first duty. This may have put the CO under additional pressure, fearing for his and his family's livelihood.

Don't punish people for being hesitant in highly complex combat situations involving close proximity of civilians.

Scenario Fulfillment is a psychological condition affecting both individuals and groups where once a situation looks like a certain training scenario, that scenario will be followed to the end, filtering out all Information that does not fit the scenario. The US Government has put forth the possibility that the entire bridge crew may have collectively suffered from this condition.

Psychological training.

The crew was under stress since they had illegally and unprovoked entered Iranian waters, and were simultaneously also engaged in a firefight with Iranian gunboats (which Vincennes provoked by illegally sending her helicopters into Iranian airspace). Either of these two infractions would have been cause for Iran to send fighters to intercept and attack the ship.

See #9.

The CO was known to be a hot-headed aggressive guy looking for fights, and even creating them if there was none. He may have been looking too hard and found one where there was none.

Don't hire such guys, filter them out using psychological evaluations.


How could a wood and fabric aircraft be controlled after a fabric tear mid-flight?

A wing tear is not something people train for because the impact on the airplane depends on where it is, how big it is, and what other systems have been damaged. If it's just a fabric tear then the damaged wing will produce less lift than the good one, meaning the airplane will want to roll in the direction of the damaged wing. For a pilot to survive there needs to be enough aileron and rudder authority to compensate for this and keep the plane level. So the first priority is to maintain positive control of the airplane and learn how to fly it again by using control inputs against the rolling action. If I feel like I need more aileron power I would decrease speed from cruise in small increments, seeing how a slower speed effects my ability to control the airplane, if it reduces the rolling and gives me better control then I'll keep decreasing speed bit by bit to find a sweet spot. If the damage happens at a slow speed, like in a climb, I would increase speed by increments. I would keep a very healthy margin above stall speed though, as the damage to the wing has probably increased the stall speed of the damaged wing. If the damaged wing stalls then I'm in a snap roll and unlikely to recover.

Once I have control I want to land as soon as I can, and I ideally want a very long runway into wind with emergency services. If I know the area well I probably already know where I want to go. If I can't maintain altitude then I need to find a big field, quick.

Once I've aviated an navigated I will communicate and declare an emergency with ATC and state my intentions. ATC can't help me fly the airplane so I didn't need them before now, but now they can help reduce my workload. If I don't know the area ATC can help me find the best place to go, and they can give me weather information and notify emergency services.

Once I get to an airfield comes the tricky part - landing. It's tricky because I don't know when the damaged wing is going to stall, so I have to keep a lot of extra airspeed on approach and landing without flaps (flaps will change the shape of the wing and the dynamics of the situation in ways I cannot anticipate). This means a faster approach and putting the wheels on the ground at a much faster speed - this is why I would want a really long strip. Once the wheels are on the ground if one wing stalls before the other I can probably control it, and the wheels will help give some stability as well while I gently brake.


What job opportunities are there for low time pilots in Malaysia?

Malaysia I suspect would be very similar to where i started working a few years back in Africa. In countries (continent) like that you really need to be there if you are a low timer. Hanging around the airports and meet people who could help you with finding your first opportunity forget about sending CV's from miles away hoping for an opportunity, key here is to be pro active and make yourself known locally....


During an engine failure should I deploy 10° of flap or keep it clean?

You keep it clean: adding flaps adds drag. You can see this in Section 3 of the Cessna POH, which includes a Maximum Glide (distance) diagram. In the C172S POH that I checked, it notes that maximum distance is achieved with:

  SPEED 68 KIAS
  PROPELLER WINDMILLING
  FLAPS UP
  ZERO WIND

(A tailwind would extend your range, but only in one direction.)

Two other points worth noting:

If the engine failure also caused an electrical failure then you won't be able to use the flaps anyway (in models with electrically operated flaps)
You might want to reduce your gliding distance if the best landing spot is relatively close by, and extending flaps is one way to do that (along with slipping, S-turns or other maneuvers, and extending the gear)


Are the window wipers on jet aircraft ever deployed in flight?

In the Falcon 50 and 900, we have windshield wipers that we are allowed to use in flight (up to 205 KIAS), but I have never used or seen them used in the eight years that I have been flying them because they simply aren't needed.  They are usually stowed out of the wind stream so don't really cause much drag.

The Learjet's on the other hand DO have hot air that blows on the windshield and we sometimes used it to blow water droplets off of the windshield when on the ground.  However, the primary purpose of the hot air was to heat and defog the windshield.

On a larger airplane, the additional piping, valves, etc. required to get the hot air all of the way up to the windshield actually weighs and costs more than just putting the windshield wipers up there along with electrically heated windshields to keep them from fogging up.


Do you need to put your wings at the center of gravity when building an airplane?

For supersonic speed, putting the wings near the center of gravity would be a good start. Even better, place the wing's center slightly aft of the center of gravity in a conventional configuration.

Lockheed F-104 in flight (picture source)

If you use rotating wings, placing their roots right above the center of gravity has worked well, too, especially if there is only one attachment point for them.

AS 355 Ecureuil helicopter (picture source)

If there is more than one attachment point, however, the rotating wings should be at opposite ends of the fuselage, quite a bit away from the center of gravity.

Boeing-Vertol CH-46 helicopter (picture source)

At subsonic speed it is advantageous to stretch the wings out sideways, so at least their tips are again quite a bit away from the center of gravity.

Nimeta single-seat glider (picture source)

And then there are some odd designs which try to separate the wings from the center of gravity as much as possible, and they still fly.

Rutan Proteus tandem wing (picture source)

So there is no general rule. Maybe these answers help to answer your questions about wing placement relative to the center of gravity.


Does landing in extreme weather conditions require any different or special training?

In some regards there is but this depends on what you consider extreme weather.

On one hand there are physical limits to which a plane can be landed when it comes to wind both head on and cross winds. Granted they are cases they may never or only rarely come up you may simply not be able to land the plane.

Assuming you have made it to the airport and are able to land...

There are some check lists and different procedures that me be executed for different weather. Snow and wet runways in general may see a longer landing distance and roll out however this is not "special" training as landing distance should always be calculated based on conditions.

Approaches are flown as published but changing winds and weather may cause the pilot to react differently or do different things to fly the approach. For example if you compare a calm wind approach to a dry runway with a wind sheared approach to a wet runway you may see some differences. The pilot may elect to come in a few knots over Vref and possibly with less flaps in a wind shear situation. Again this is not special training as much as it is standard.

On a contaminated runway the pilot may chose to preform something like a short field landing so as not to potentially collapse the nose gear. All pilots (even GA) are trained in this maneuver. There are so many possible situations here it would be hard to train for ever one but some are trained for or a checklist exits.

Side Story: I was talking to a commercial pilot recently who flies the 777 and he was telling me a story of a time during training in the sim where they gave them heavy rain and 40Kts of wind shear (no one could successfully land the plane that day in his group in the sim). So they do at least throw situations like that at pilots in the sim, if they do it all the time I cant say.


Which country is responsible for prosecution if a crime is committed over international waters?

Broadly the legal constructs that apply here are essentially the same as for sailing vessels - in other words when you're outside the jurisdiction of any given nation the laws of the country the vessel is registered in apply, and the captain is the one who makes the decisions.

More specifically once you enter the airspace of a nation that nations laws also apply (the same as crossing the boundary from international waters to the territorial waters of a nation - by entering their territory you're obligated to abide by their laws).

If the above doesn't seem murky enough, it's because it actually gets a lot more complicated than that when you start considering all the laws various countries may pass (and subsequently attempt to enforce).

Consider for example The "Special Aircraft Jurisdiction of the United States" in which the US claims jurisdiction over any aircraft in our airspace, or any aircraft in flight which is intending to land on our soil (as long as they actually do land on our soil).

As with most areas of international law going to far down this rabbit hole will likely lead to madness.
For practical purposes you can assume that four bodies of law will govern every flight:

The laws of the country from which the aircraft is departing.
The laws of any country whose airspace the aircraft transits, while in that airspace.
The laws of the country in which the aircraft is landing.
The laws of the country to which the aircraft is registered.

...and if you can avoid breaking any laws in those 4 categories you'll be pretty well covered for most circumstances.


How should I read these climb and descent profile notations?

For the climb profile, the first two values are indicated airspeed -- below 10,000 and above 10,000 feet MSL, and the final value is a Mach fraction. So 250/280/78 would be a climb of 250 knots below 10,000', 280 knots above 10,000', and transition to a climb of Mach .78 somewhere in the high 20's or low 30's (i.e. at the point where 280 KIAS = M 0.78).

For the descent profile, it is the reverse, initial Mach number from Cruise altitude until reaching the transition to indicated airspeed, then the IAS above 10,000', then the IAS below 10,000'.

The 250/280/78 climb profile is very standard for the 737 NG and Max aircraft; most airlines fly them at something fairly close to those speeds, using a Cost Index which starts there and then the FMC applies an adjustment for headwind or tailwind.  In a stiff headwind, the climb speed will increase up to maybe about 310 KIAS (as a ballpark) and Mach .80; with a strong tailwind the speed will go down to maybe 270 and Mach .76 (again, ballpark - exact Cost Index being used affects these adjustments).

The typical descent profile looks similar, although at least in the US we'd never use 280 knots below 10,000' -- it would always be 250 below 10.  If the country you were flying in didn't regulate that, you might do 280 down to close to pattern altitude, but I don't know what countries would allow that, and what you'd gain in time saved (not much) you'd pay for in terms of risk if you hit a big enough bird on or near the windscreen.

But that's what those numbers are almost certainly referring to.


Does useful load increase with more horsepower?

First, you ask one thing in the title and another in the text of your question. Useful load is the sum of fuel and payload, whereas the gross weight is the force produced by the mass of the whole aircraft in the gravitational field of Earth.

First: Gross Weight

If you change engine power during airplane design, gross weight will go up. At that point, you will have relative parameters like wing loading (kg/m²) and power loading (kW/kg) defined and will size the aircraft accordingly.

If you switch the engine of an existing aircraft to a more powerful one, you will need to modify the airframe and systems if the aircraft had not been designed for the more powerful engine initially. Now your gross weight is already defined and cannot simply be changed. Let's first see what happens if a more powerful and heavier engine is fitted:

The higher engine mass will affect the location of the center of gravity and reduce the possible payload. Note that the mass increase will include a stronger engine mount and firewall, and possibly a balancing weight in the tail to put the center of gravity back into the legal range.
If you want to maintain the same power loading, you will need to increase gross weight, which in turn will increase structural loads. Now you need a heavier structure.

For now, let's assume that you stick with the old gross weight and reduce payload accordingly, because you do not want to rivet doublers all over the structure. Fine, but we are not done yet.

You might want to fit a larger propeller, which might require changes to the landing gear to keep a minimum ground clearance.
Your minimum flight speed will go up. If the aircraft is certified according to FAR part 23, the minimum speed should stay below 61 knots (see §23.49(d)). Maybe you will need to fit more effective flaps to keep the minimum speed constant.
Your maximum flight speed will go up. Technically, you can keep the limit speeds of the less powerful aircraft, but dive speed is calculated in one case by assuming 75% engine power (see §23.335(b)4i), so you will most likely be required to adjust limit speeds.
Once you raise limit speeds, structural loads go up. Now you need again to start riveting doubles all over the place.

You see, you cannot legally escape. Fitting a more powerful engine will require adaptions in the structure, and once you need to reinforce wings, landing gear and fuselage, you can as well choose a higher gross weight. But now you need to re-size the structure and re-certify the modified aircraft.

And we have not even started to look at the systems:

The bigger engine will have a higher fuel flow. Are the fuel pumps adequate, or will you need to switch them for more powerful pumps?
The higher design speeds might increase control forces, so now you need to modify the control system to avoid exceeding maximum stick forces (§23.143, §23.175)
Will the new engine excite new harmonics somewhere in the aircraft? Maybe now a part will vibrate and shake itself to pieces which had stayed calm and in one before?

The list goes on, but this shall suffice.

Now to your specific case: If you want to keep the power loading constant (which will give you the same performance as before), the airplane gross mass goes up by 54%, and so does the wing area.

If you want more performance, you will need to reinforce the structure (or start all over with a new design of the same size), and now it is up to you which gross weight to pick. The heavier engine and structure will eat into your payload and fuel, but if you accept that limitation, you can fly with the same gross weight as before.

Second: Useful load

As you can see from the first part of the answer, useful load is reduced by fitting a heavier and more powerful engine. Only when you re-work the structure to cope with the higher loads can you raise wing loading and regain the loss in useful load. Whether you can increase it by more than what you have lost so far depends on the maximum wing loading.

Let's assume for the rest of the answer that the outside shape (wing area, airfoil etc.) will stay identical to the original aircraft, except for maybe a bigger cowling, propeller and radiator.

The mass increase of the power plant plus its supporting structure is linear to the increase in performance. To beef up the structure, you could use the same percentage rule to stay on the safe side, but the real increase will be smaller. There are books which list parametric formulas for airplane masses, and those will show you the influence of the main parameters. They show that wing mass goes up with the square root of dive speed. Since speed is proportional to the third root of engine power, you will see that 54% more power means 15.5% more speed and 7.5% more structural mass.

Now let's assume that the propulsion system is 15% of the aircraft mass, and structural mass is another 40%. Your empty mass will go up by 8% (engine) and 3% (structure), and if your useful load was 30% of gross weight before, it will now be down to 19% of the same mass. Now we need to bump up the gross mass, and go for half of what you would gain if you keep power loading constant. This means your gross mass is going up to 127% of the original gross mass.

Before you rejoice that now your useful load has gone up to 46%, we need to account for the additional structural reinforcement that this gross mass increase produces. The parametric formulas give a structural mass increase proportional to m$_{gross}^{0.3}$ for the fuselage and m$_{gross}^{0.7}$ for the wing, and a higher wing loading will again result in a dive speed increase, so your total structure will now maybe weigh 15% more than before, for a total of 47% or 48% of the initial gross mass. Yes, your structural mass fraction will go up when you  increase wing loading! But still a sizable increase in useful mass should remain - you will now have 39% or 40% of the original gross mass available for fuel and payload, for a relative increase of 30% over the original useful load.

Now I never tried to keep minimum speed constant, but that would had complicated this answer even more. If the original plane had no or very simple flaps, this would be quite feasible, but result in almost a new wing design.


Would fitting a T-tail on the 737 Max make MCAS unnecessary?

No. A t-tail would worsen the characteristics of the airplane. While not necessarily a horrible idea in its own right, the already-nasty slow-flight/high alpha/stall characteristics of the aircraft that necessitated MCAS in the first place would make this idea dangerous. The pitch-up tendency could lead to a stall, which in a T-tail can lead to a deep stall. A deep stall is a condition in which the wing blanks the tail surfaces. Since the tail is no longer effective, recovery is EXTREMELY difficult, if not impossible. So really, a T-tail offers no advantages and may actually be MORE dangerous. Regarding your second question, no. This proposal is such a drastic departure from both the 737 and 727 that recertification would be unavoidable.


What is the visual manoeuvring area (circling approach) radius for PANS-Ops (ICAO)?

The 300 m and 1 000 m tables you found are examples. For the actual radius for any aerodrome elevation you need to apply the formulae.

The radius is determined using the formulas in Section 2, Chapter 3, Turn area construction (...) The TAS is based on:
a) altitude: aerodrome elevation + 300 m (1 000 ft); and
b) temperature: ISA + 15°.

First is $R$ (rate of turn) using $V$ (TAS in km/h) and $\alpha$ (bank angle of 20° for circling per Table I-2-3-1). Then plug $R$ in $r$ for the radius.
$$R = (6\;355 \tan \alpha) / \pi V
$$
$$r = V / (20 \pi R)
$$
Now, the $V$ (TAS) depends on the category and altitude (which is already aerodrome + 1 000 ft).
First get the IAS from Table I-4-1-1, then convert the IAS to TAS using the conversion factor in Section 2, Appendix to Chapter 1 (I-2-1-App-1).


Do airline pilots have to wear face masks in the cockpit because of COVID?

I can answer this question accurately - not as an airline pilot directly, but as the son of two.
To keep it short, no. Airline pilots are free to make their own decision about their safety in the cockpit. In the airport, yes. In the taxi, bus, or ground transportation, yes. But, when they enter the cockpit, they usually sanitize the entire touch area, use some germ-x, and settle in for the 12-14 hour flight. When going back into the cabin, they put a mask back on (while on break).
There have been some cases reported in the pilot body but not enough to cause any large issue. Thanks for your question.


A gold seal flight instructor is obtained by having a ground instructor certificate and within the previous 24 months have a pass/fail rate of 80% or above and recommending at least 10 applicants.

It is a way for the FAA to recognize the best instructors in the industry.  You do not get any special privileges with the gold seal.

See AC 61-65 for more details.


Doppler shift in appendix G of ATSB report for the MH370 incident

1. Why should the Aircraft Latitude affect the Doppler frequency shift?

It seems to me that table 6 is a check to test whether the equation on page 55 can reliably be used to predict the possible locations of an aircraft from a measured BFO. It does this by using the equation to predict what the BFO should be for a given set of inputs and comparing that with the measured BFO. To see how reliable this is they vary one of the parameters, latitude in this example, to show that the predicted BFO is considerably different for different latitudes and that the best match of predicted BFO to the measured BFO is for the known location of the aircraft. Therefore you know that the BFO is useful - it can be used to rule out some locations.

If you hold constant all the other factors and vary latitude why should that affect BFO?

I guess it's because for the same aircraft heading (with respect to true north), different latitudes but same headings mean different angles of flight with respect to the satellite. That means that there are different magnitudes of component of velocity that is parallel to the line from satellite to aircraft - those different magnitudes represent different speeds in a line directly away-from or directly towards the satellite. This affects doppler.

Note: The above doesn't explain why ΔFdown varies with aircraft latitude.

Other independent analyses of this data

Dr Richard E Cole, University College London
Dr Duncan Steele (who asks the same question)

I'm pretty sure Duncan Steele is smarter than me, so you may be on to something.

  2. However, I can only derive this exact frequency using the satellite velocity for UTC time 16:55:00?

That's more of a statement than a question. I guess your question is:

  why do my calculations give a different answer?

I see two possibilities

you made a mistake.
the ATSB made a mistake†.

In order for readers to help you with the first or confirm the second, you'd really have to share your calculations with us.

† And presumably Inmarsat, the NTSB, the AAIB and others.


What is a heat dissipater and how does it work?

The heat dissipaters  are used to reduce the infra-red signature of the helicopter engine exhaust. They are also used in other helicopters, like the 'black hole ocarina' (BHO) infra-red suppression device used in AH-64 Apache.

Source: b-domke.de

The main purpose of the IR suppressors in use today is twofold:

Reduce the IR signature by reducing the exhaust temperature
'Shield' the hot engine from view.

The infra-red suppression systems in service today usually work by

'Bending' the exhaust, usually upwards, and shielding the exhaust from view by an insulating cowl. In these IR suppressors in Mi- 35 (export version of Mi-24), the exhaust is turned almost 90°.

Source: mamboccv.com

Mixing the hot engine exhausts with the cool air, effectively reducing the exhaust temperature. In the Black Hole IR suppression system, the exhaust temperature is reduced from ~600 °C to ~300 °C .
The RAH-66 Comanche had the infra-red suppression system integrated into the airframe (the exhaust was routed through the tail boom), though the principle is the same- mixing of engine exhaust with ambient cool air.

Source: sikorskyarchives.com

In some cases, the special high emissivity coatings are applied to the engine exhausts for reducing the IR signature.

Most of the present IR suppressors focus on achieving a thorough mix of the cool ambient air and the exhaust to reduce temperature and uneven mixing, in order to prevent 'hot spots'. Cooling of the exhaust pipe itself is achieved in some cases by using film cooling. In most helicopters, the infra red suppression system (IRSS) is optional and can be added separately.

The figure shows the schematic of the infrared suppression system used in AH- 64 Apache and the associated reduction in IR signature.

Image from Progress in helicopter infrared signature suppression by Jingzhou Zhang et al., Chinese Journal of Aeronautics, Volume 27, Issue 2


Why do airlines have intermediate stopovers with no passenger boarding?

DeltaLima is correct but there is a little more to the story which he hints at in his link. This topic is known as Freedoms of the Air. There are five official in total, each dictating in what way an airline may operate in a foreign country. What KLM has done is a:

Normal stop for those getting off.
Technical stop for the onward passengers.

Both are less controversial than what would essentially be letting a foreign operator offer flights in your country, which would not help local carriers ( and which would constitute Cabotage as DeltaLima says).
The technical stop is defined in the second freedom of the air:

Second Freedom of the Air - the right or privilege, in respect of scheduled international air services, granted by one State to another State or States to land in its territory for non-traffic purposes (also known as a Second Freedom Right).

The Third and Fourth Freedom states that the airline can load and unload passengers in a foreign country for transport to and from the carrier home country:

Third Freedom of The Air - the right or privilege, in respect of scheduled international air services, granted by one State to another State to put down, in the territory of the first State, traffic coming from the home State of the carrier (also known as a Third Freedom Right).
Fourth Freedom of The Air - the right or privilege, in respect of scheduled international air services, granted by one State to another State to take on, in the territory of the first State, traffic destined for the home State of the carrier (also known as a Fourth Freedom Right).

(Needless to say, 3 and 4 go hand-in-hand)
Source: ICAO
See also this Boeing document for easier reading.
The other option, aside from not doing it for legal reasons, is that KLM cannot justify the trouble and cost of doing it.

Setting up more domestic presence (websites, additional staff, pricing in regard to competition) in a foreign country is a somewhat complicated business.
There would be additional waiting time on the ground when stuff was loaded and paperwork sorted out.
Furthermore, I imagine that KLM would like to block the free seats for the complete leg as long as possible (which would generate the greatest revenue), so the actual number of available sub-segments for booking would not be that great.


Does the stability of a mass change if the center of gravity is above or below the point of thrust?

The most stable way to maintain a hover is center of mass below and center of drag above.
What confuses many people is how a "pendulum" reacts while being accelerated, and how it reacts when air drag stops acceleration.
Placing the center of drag above the CG is commonly seen on aircraft tails.  This is one reason why "classic" aircraft tails are "upright". Wing dihedral serves the same purpose,
to roll a side slipping plane back to level.
Once hover stability is achieved, one may reduce drag above or add drag below to reduce stability enough to allow controlled movement.
Leaving the Center of Gravity underneath will increase stability where when the object is not accelerating.  But "pendulum stability" is more properly called "pendulum  and drag stability", as in a parachute.
So, in your case, keep the triangle above with light materials., but have your weight below the rotors, and just use the rotors to lift and propel the aircraft.  But if you want a separate (red arrow) source of propulsion, try to put the center of horizontal drag and CG in the same spot, and push there.


Can you identify this model of a twin-engine propeller aircraft?

It resembles I.AE. 24 and I.AE. 30, but not close enough for a match.

I believe this is a model of the De Havilland Mosquito.

Image source: ThoughtCo.


Justification for the 2D cut-out method for determining a rocket's center of pressure

I couldn't justify this method more simply than NASA does:

  For model rockets, the magnitude of the pressure variation is quite small. If we assume that the pressure is nearly constant, finding the average location of the pressure times the area distribution reduces to finding just the average location of the projected area distribution.

So the pressure, constant everywhere, "cancels out" leaving you with only area.

And the simplification from a 3-D shape to its 2-D projected area is justified by the shape's relative simplicity and symmetry.  This wouldn't work with a grand piano.


Why does the Boeing 737 have 5 x the passenger fatalities of the Airbus 320?

For one, the early 737s had a design flaw which allowed the rudder to reach a hard-over position, and get stuck there. Boeing initially dragged their feet in rectifying this, so it took a number of accidents before this design flaw was corrected. This is a major contributor to the high number of fatalities in the early operational years.

To have a more meaningful comparison, I would suggest to compare the fatalities per year, so the status in operational procedures can be excluded as a factor. As others have pointed out, this should give a more equal basis for a comparison.

If you look at fatalities per year, beginning in 2000, these numbers emerge:

Now you need to factor in the number of flight hours per type per year, which I do not have available. But I would expect that the low fatality rate in the early 2000s is more due to the small number of A320s around. But if we just compare the 737 NG with the A320, this advantage is reversed, and still the A320 comes out slightly ahead.

But thankfully, there are very few accidents for each type per year, so the statistical base is too low for a meaningful comparison. If we want to draw any conclusions, it could be that the A320 is indeed a safer aircraft, but the certainty of this conclusion is very low, being based on a very small number of accidents.


What are the SOPs following an overweight landing?

The answer very much depends on the operator and type of aircraft (or rather its manufacturer).

First of all, overweight landing would normally be performed for the following scenarios:

Medical emergency on board that requires prompt medical attention
Any fire/smoke that cannot be extinguished/ventilated
QRH dictating "Land at the nearest suitable airport"
Any situation where safety might become further degraded by prolonged flight

It's hard to list all the situations here, and most of the time the Captain will have to make a decision whether to do an overweight landing or not.

Having made the decision to perform an overweight landing, the crew needs to take into consideration the following items:

Runway length available - landing at significantly higher weight than MLW increases landing distance substantially
Missed approach climb gradient - this might be a problem at airports with high terrain nearby
Reduced landing flap - normal landing flap speeds at higher than MLW might be too close to Vfe (maximum speed for the selected flap setting)
Required brake cooling - if heavy braking is required to stop within the required landing distance available, then it's best to vacate the runway and have fire services check the brakes and tires. Fuse plugs might have melted and tires might have deflated. Subject to all clear from the fire services, aircraft might taxi to the stand, have the chocks set and wait there with brake released for a while.
Overweight autoland is normally not recommended, as the autopilots are not certified for this.

After an overweight landing, an inspection is required by engineers to make sure there are is no structural damage on the aircraft, particularly its landing gear and the skin. According to my knowledge, the overweight landing inspection is just a bit more thorough walkaround by the engineer, provided the overweight landing wasn't a hard landing. If it was a hard and and overweight landing combined, the aircraft is likely grounded for a while, as more detailed inspection is required.

All Part 25 (FAR 25, CS 25) aircraft are certified to be able to land with sink rate of 600 ft/min (10 ft/s) at MLW and 360 ft/min (6ft/s) at MTOW, so unless you do a particularly poor landing when overweight, there should be no structural damage, even when landing straight away after a takeoff at MTOW.