How would the Airbus A320 PFD respond to failure of all pitot and AOA sensors?

The primary flight display¹:

is a single display, but it shows five separate instruments:

On the left, the speed tape. This shows the value from the pitot probe.
In the middle the attitude indicator. This shows attitude from gyroscopes. All gyroscopes are grouped in the “inertial reference unit”.
On the right the big tape is altitude. This shows the value from the static port.
The smaller tape at very right is vertical speed. It is normally taken from the inertial navigation system, which is part of the inertial reference unit, but can fall back to the static port.
On the bottom is compass. This shows the value from the inertial reference unit, which has drift automatically compensated by reference to magnetometer.

The angle of attack is not displayed anywhere. It is only used for stall warning, as part of the alpha-protection logic and for checking the weight set in FMGC.

For all the instruments, each instrument shows value from one input. The three pitot probes, static ports and inertial reference units each feed one of the three displays in the cockpit: captain's PFD, copilot's PFD and the standby instrument (which in the modern version looks like smaller PFD and is placed between captain's (left) displays and the centre display.

When any of the input fails, the computer will generate a warning (accompanied with the annoying cricket sound) stating that the values do not match, but it leaves it up to the pilots to determine which one is wrong. The pilots can then switch the displays to show the one they determined as trustworthy.

So:

If all pitot probes failed, the speed would show nonsensical values, but the attitude, altitude and heading would remain operational. The system would fall back to alternate law. There is an unreliable airspeed procedure where the aircraft is kept in safe speed range by reference to attitude and vertical speed. Failure to execute that procedure properly was an important part in the accident sequence of Air France flight 447.
If the angle-of-attack vanes fail, the stall warning and alpha floor protection will not work, but all displays would work. However, the system may actually not notice that they failed as evidenced by the accident of XL Airways Germany flight 888T. This was a test flight where they intentionally tried to activate the alpha-floor and it did not activate without any prior indication because the AoA-vanes froze due to improper wash.

¹ The image shown clearly is supposed to be Airbus PFD, but some elements like the protection indicators and the Mach number are missing. I just didn't quickly find better as this one is very readable.


What kind of aircraft may land on iced areas, like Antarctica?

I've spent 6 summers in Antarctica (Mt. Erebus), travelling through McMurdo, where the busiest airstrips on the continent are. Most flights to McMurdo are on C-17s or C-130 Hercules. Some of the Hercules are LC-130 -- the L  indicates that they have skis. The skis enable them to land and take off on some including ungroomed or poorly groomed snow / ice surfaces. Sometimes they need JATO for takeoff, though, if the conditions aren't great.

McMurdo has three runways which open and close operations during the year: Willy Field, Pegasus, and the Ice Runway. The Ice Runway is on sea ice and the other two are on the Ross Ice Shelf with Pegasus built on blue ice and Willy Field on snow. The Ice Runway breaks up each year during the height of the summer so it is carefully monitored. It bends downwards each time a C-17 lands. That deformation is measured and is one of the parameters that's used to decide when to stop using the Ice Runway each year.

Sometimes, planes designed for non-military use are flown to McMurdo; the New Zealand Antarctic program often flies an Airbus A319 there. As far as I know, a well-groomed snow / ice runway can accommodate any plane in good weather. A Boeing 757 flight to McMurdo from Christchurch had a scary incident recently where it was forced to land in low visibility because it didn't have enough fuel to "boomerang" back to New Zealand. The C-17s often boomerang due to bad weather. The Hercules, like the 757, don't carry enough fuel to boomerang, but they are better at landing in inclement conditions so it doesn't seem to be an issue.

For flights within-continent, Twin Otters and Baslers are in common use.

No, there's no military presence with offensive capability. I don't really understand this (recently added) part of the question -- did you think they'd hit you with antiaircraft??? There's a bunch of air force guys who operate the flights, and a single US Marshall in McMurdo.


Does an airfoil drag coefficient takes parasite drag into account?

Airfoil drag is "parasitic" (or better: everything but induced) drag.
It consists of shear drag and pressure drag, the latter mostly from local flow separation. Both are only present when viscous flow is assumed. Airfoil drag is for the wing section without taking tip effects into account, presuming an infinitely wide wing. This kind of theoretical wing has no induced drag (d'Alembert's paradox).
L/D max is the point on the polar curve where the angle to the origin of the coordinate system is steepest. This is not the point of the lowest drag coefficient! Maybe you mean the point of lowest drag for a full airplane – but that is another story, with more than just the airfoil polar. Now induced drag is part of overall drag and due to its inverse relationship with speed, a distinct minimum can be found when lift is held constant.

Drag polar of the NACA 23012 airfoil (picture source, colored comments own work)


Why is paragliding not an old invention?

Paragliders as we know them depend on parawings with relatively high glide ratios and useful levels of steering.  Neither of these qualities were well represented in the round parachutes (even the so-called glide 'chutes) in common use before modern flat canopy glide parachutes came along (in the 1970s?).  Parawings as we know them were an outgrowth of these highly maneuverable parachutes, modified to have lower loading (for better sink rate) and optimized for horizontal flight, without the need to open in a near-vertical fall at terminal velocity.

If the knowledge had existed, parawings as we know them could have been built as early as the 1860s (when plain, round, uncontrollable silk parachutes came into use for stunt jumps from balloons).  The missing ingredient, as it were, was simply the knowledge that such a thing was useful and possible.


Why does Airbus continue with the A330-800neo despite only having 6 orders?

There used to be a bit more demand. Hawaiian committed to 6 orders plus 6 options, and Transasia also ordered 4, coming to 16. Unfortunately, Transasia ceased operations and canceled their orders, and Hawaiian hasn't exercised any of their options yet. That leaves the -800neo at only 6 planes on order.

Update: Hawaiian Airlines announced they would cancel their orders for the A330-800neo and instead opt for the 787-9, signing a letter of intent to order 10 with purchase rights for 10 more.

Airbus was probably hoping for more orders and continuing development of the -800neo somewhat "at risk". Of the 1368 currently delivered A330ceo, 615 of them are the -200. This would suggest there may eventually be demand to replace those with the -800neo. Almost all of the A330 fleet is less than 20 years old at this point. There's still time for more orders as the A330neo only recently made its first flight.

As the first -800neo has now been built, most of the overhead in developing it has already been spent. There will of course be more as it must also be flight tested and certified, but evidently Airbus still sees value in going through with that. It will be a balance between Airbus recouping costs of development or avoiding costs of further development and support, and the needs of the customer.

Airbus probably also sees value in keeping Hawaiian happy. Hawaiian has not ordered any -900neos and they currently have 24 -200s in their fleet, suggesting that even if no other -200 operator orders the -800neo, Hawaiian might order more. Airbus may prefer that Hawaiian takes the only 6 -800neos they ever build than for them to go and order the 787 instead.

The 737-7 MAX is in a very similar situation. Boeing only has 58 orders for the type, which is 1.4% of the total orders for the MAX (the 6 -800neos account for 2.7% of the total A330neo orders). To compound this, the launch customer, Southwest, recently announced that they're delaying 23 of their 30 orders, possibly to covert them to a different version. Yet Boeing recently rolled out the first -7 and seems to plan on going ahead with it.

Since these planes have already been built, the manufacturers probably see some value in keeping the orders around so they can still sell the planes, and avoid the bad PR of going through the trouble to develop, sell, and build the plane only to cancel it. It remains to be seen if the airlines will continue to see value in taking delivery of types that no one seems to want.


What will happen if satellite navigation fails?

It only takes 3 satellites for a GPS fix (4 if you want altitude). There are 31 operational satellites currently in orbit and at any given time you can most likely receive a signal from half a dozen of them at least. That being said the chances of them failing completely is almost 0%. But of course what if they did, well...

There is always the Russian version of GPS known as GLONASS so there is effectually an entire redundant global navigation system in space. While not all aircraft are equipped with GLONASS receivers it is of course becoming more common. Even the little tiny receiver I use for GA flights has it now. So there is that redundancy.

In controlled airspace you have ATC there to help you. They can effectively watch you on radar and tell you what to do which is basically what flying IFR is. For this you will need an operational altitude encoding transmitter so that ATC knows your altitude along with position. If you are flying VFR and require assistance you could call for Flight Following here in the US, load permitting. They can offer limited guidance but if you tell them you are lost they will generally help.
If there is no ATC you can hone in on VOR stations, or some of the older radio direction finders like ADF systems assuming your aircraft is equipped with such equipment. Some modern handheld radios can also hone in on VOR stations

If all that fails you have your good old magnetic compass and hopefully some way of keeping time. With close track of your airspeed, a clock, and a compass you can navigate pretty accurately even in the blind (although I don't recommend that).

No compass, no problem, you always have your ground reference points to get where you need to be. Basic VFR navigation which every pilot know how to do is learned this way. This will require you have a VFR map of the area which most GA planes will carry. Note the roads, power lines and other large things marked on the map that are easily identified from the sky.

Outdated/less popular systems:
Inertial navigation systems are still used in plenty of places however they are not as accurate as other systems available in modern aircraft but they work by knowing how fast you have gone and in what direction you have accelerated to that speed. Thus position can be calculated. INS systems suffer from integration drift which can add up over time and make the margin of error pretty big.
There was once a time in history when you could get a navigators rating on your license. These people were trained in many times of navigation including celestial navigation. Older planes were even outfitted with a sextant for that very reason.

LORAN C was officially shut down here in the US/Canada in 2010 but there are still active chains elsewhere in the world. Some planes out there still have the units in them (one of the Cherokees I fly still has it sitting there). So depending on where you are you may be able to use it.
What Time Is It:
The US GPS network is synced up via the USNO master clock and while it is unlikely that all the satellites will fail simultaneously or fall out of the sky, or be shut down. The master clock does provide a central point of failure for the system. While I am not up to date on the full function of the system I would imagine that a downed clock could introduce a margin of error into the system. Worse so an incorrect value fed from the master system may cause an erroneous reading.


How challenging is it to land a plane on a tabletop runway?

There are a couple of optical illusions that can come into play on tabletop runways:

Because the runway sits higher than the surrounding terrain, depth perception can be thrown off and the runway may seem like it should be lower than it actually is.

Due to the steep drop off just past the end of the runway, it can be difficult to judge the remaining length as it seems to stretch on into the landscape beyond, almost like an infinity pool.

Beyond this, tabletop runways in general tend to punish overruns more than traditional runways because there can be very limited space before the large verticle drop. Precise, well-configured approaches are vital, and proper care must be taken to ensure that the runway provides plenty of length for the landing roll of the aircraft (considering speed, flaps setting, weight, runway condition, etc.)
To simplify: There are plenty of runways that are trickier to shoot, but might not have such a severe penalty for getting it wrong.


Taxiing with one engine: Is engine #1 always used or do they switch?

Airbus aircraft have 3 hydraulic systems (Green, Blue, Yellow). Green is pressurized by left engine, Yellow by right engine, and each one can be pressurized by the other using the PTU. In addition the Yellow circuit has an electric pump.

The Blue circuit is a backup pressurized on demand by several means (electric pump and RAT).

Each circuit powers different aircraft components:

Source: A320 FCOM

The choice of which engine(s) to use is based on the need to have pressure:

For brakes
For nose wheel steering system.

Normal brakes and nose wheel steering are pressurized by the Green system. The brake accumulator must be pressurized, this can be done by running the an electric pump without starting an engine..

Engines are numbered 1 for left, 2 for right on twin-engined aircraft and from left to right (1/2 and then 3/4) for four-engined aircraft.

From this document:

Which Engine to Use?

  A320 Family: ENG 1
  A330: ENG 1
  A340: Outer engines (ENG 1 + 4)

Why?

A320 Family:

  ENG 1 pressurizes GREEN HYD (NWS + NORM BRAKE)
  YELLOW HYD pressurized via ELEC PUMP
  PTU is not needed

A330:

  ENG 1 pressurizes GREEN + BLUE HYD
  HYD BLUE ensures ACCU PRESS
  ELEC PUMP are not needed

A340 (outer engines when possible -- exception would be a narrow taxiway and FOD risk):

  ENG 1 + 4 pressurize GREEN HYD (NWS + NORM BRAKE)
  Check ACCU PRESS normal before ENG start
  ELEC PUMP are not needed


Is the airport capacity related to number of runways?

Airport Capacity

At major airports the capacity of the system of runways is the most restricting element. While it is usually possible to increase capacity of the other airport elements or adding a new runway (plus associated taxiways) is very expensive and takes a very long time to complete.

The runway capacity is the principal cause of most extreme instances of delays that lead to widespread schedule disruptions, flight cancellations and missed flight connections. The runway capacity varies greatly from day to day and changes are difficult to predict (even a few hours in advance).

Factors:

The capacity of the runway system depends on several factors, the most important ones:

Mix of aircraft classes using the airport: the aircraft mix indicates composition of aircraft fleet that is using any particular runway (e.g. 25% S, 60% L and 15% H).
Separation requirements imposed by the ATM system: due to wind tip vortices, leading aircraft and trailing aircraft must be separated by a determined distance (Heavy aircraft are the ones that produce more wake turbulence).
Type and location of exits from the runway: trailing aircraft of any pair cannot touch down on the runway before leading aircraft is clear of the runway. High-speed runway exits (also well placed runway exits) reduce runway occupancy times for arriving aircraft.
Mix of movements on each runway and the sequencing of the movements: specified for all combinations of consecutive operations (arrival-departure). There's an important trade-off between maximum arrival and departure rates that an airport can achieve.
Lateral separation: (especially in bad weather) between aircraft approaching the same airport on parallel runways.
Sequencing and separation of departing and landing aircraft on runways that intersect.
Sequencing of aircraft approaching airports located in close proximity to one another, where one aircraft must cross the path of another aircraft landing at a nearby airport.
Direction and strength of winds.
Noise-related and other environmental considerations and constraints.

Conclusion:

It is difficult to predict the capacity of the runway system of an airport, so it is difficult to compare two airports with similar runway characteristics, since the factors depending on the airport capacity involve different design and operational parameters. Furthermore, everything is subject to the important probabilistic factor, the weather, which makes the prediction and comparison of airport capacity even more difficult.


Acme screw type screw jacks with the square threads, as used in stab trim systems (as opposed to a recirculating ball screw), are usually inherently irreversible because of the higher friction of the direct sliding contact of the square sided threads vs a rolling ball interface (as a sliding interface, it's totally dependent on the grease to keep friction in check).

This is why the trim screw jack of the 737 becomes extremely difficult to move manually when the jack is heavily loaded, even though the movement input is coming from input side that is supposed to be the low effort side, requiring a technique of unloading it with elevator inputs to manually trim when the airplane's actual speed and trim speed are far apart.

Ballscrew type jacks however, typically used for flap actuators, have very low internal friction and very high efficiency thanks to the ball interface between the "nut" and screw (rolling, not sliding).  As a result they can be back-driven more easily; how easily depends on the gear reduction within the worm drive gearbox.

Ballscrew operated flap systems typically require friction brakes in the drive line, or anti-backdrive devices incorporated internally in each actuator (basically a clutch device that is disengaged only when the torque is coming from the input side), to prevent a flap surface that is disconnected from its drive motor from creeping up from air loads.

Acme screw actuators also have internal brakes but these mainly function to lock an inoperative motor when there are dual motors, so that the live motor can't backdrive the dead one instead of the downstream gear train.  They also serve to lock the acme screw when both motors are off, but this isn't as critical with an acme screw.


What's the difference between an airplane that stalls nose down or just mushes in a stall?

You are absolutely right that it has to do with the pitching moment (Cm) characteristics of the aircraft. Take a look at the sketch below illustrating three different pitching moment characteristics:

In all the cases, you can assume that the CLmax occurs around 12deg AOA (not presented here). Cm1 is the aircraft that would present a distinct nose-down upon reaching CLmax. This is also known as a pitch bucket, because of its shape, and is good for stall identification and recovery as the aircraft tends to un-stall itself.

Cm2 is the mushy case. With increasing aft column pressure, the AOA will continue to increase, while the airspeed may stagnate. No stall identification is naturally provided to the pilot.

Cm3 is anything from stick lightening to outright pitch up, depending on the aggressiveness of the instability. This is a common characteristic for high speed aircraft that have large LE sweep and the stall does not originate from the root of the wing.

As mentioned by Carlo, the degree of nose-down or nose-up would also be CG dependent. Aft CG would always have smaller pitch bucket and worse pitch up (if exist).


Why are some A350s missing SSA probes on their nose?

You are right: the three side slip angle probes are redundant because side slip can be calculated by the ADIRS without these probes. Airbus included them in earlier A350 models to crosscheck this calculation, but they are removed now:

Spot the difference 2: SSA (Side Slip Angle) Probes.

This one’s a bit more technical. If you look closely around the nose of the aircraft, you can see an array of sensors. These form part of the Air Data and Inertial Reference System – in other words, they feed flight parameters to the pilots, such as the angle the aircraft is flying, the outside temperature, and the barometric and static pressure.
As the A350 entered service, Airbus still wanted to gather more information to compare the data between different systems that help pilots fly on approach in crosswinds. To do that, a few early models had extra probes added to cross check the data from the other instruments. You can see these three extra vanes on the front of the aircraft just below the ‘Zorro’s Mask’ windscreens. Having now gathered enough side slip information to establish that they’re not required, they’re being removed on all new A350s. They’ll also be taken off our first two aircraft in the coming months, which will save weight and maintenance costs.

(Virgin Atlantic Blog: Airbus evolution: Can you spot the difference?, emphasis mine)


Is a pilot responsible for CTAF announcements in this scenario?

In the U.S., the definition of an accident is covered under 49 CFR Part 830.2:  (emphasis is mine)

§ 830.2 Definitions.
As used in this part the following words or phrases are defined as follows:
Aircraft accident means an occurrence associated with the operation of an aircraft which takes place between the time any person boards the aircraft with the intention of flight and all such persons have disembarked, and in which any person suffers death or serious injury, or in which the aircraft receives substantial damage. For purposes of this part, the definition of “aircraft accident” includes “unmanned aircraft accident,” as defined herein.

From your question, this appears to clearly be an "Accident."


How do redundancies work in aircraft systems?

Triple-redundant systems have four independent members, so if one fails, a two-to-one vote of the remaining three is still possible.

One system    = No redundancy.
Two systems   = Simple redundancy.
Three systems = Double redundancy.
Four systems  = Triple redundancy.

However, often the term "triple redundant" is used when the system has only three members. And if all three disagree, two of them must be faulty already, so this is a case of multiple failures.

In case of Airbus, besides the three main FCS computers two backup systems are available to help isolate the faulty one. Inside, each has two channels which run software written by a different team, run on a processor different to the one in the other channel and which are supplied by two different suppliers.  This helps to reduce systematic errors, when all together would fail because of a common malfunction.

Airbus flight control system diagram (picture source). Only the first system of each is expanded; the boxes for system 2 and 3 look the same on the inside. Input is from the side sticks, and output goes to the hydraulic valves at the control surfaces. The voting happens first in the comparator step (between the two channels) and again in the filters (between the single systems).


It's not possible to tell for certain based just on this one picture, but I don't see any reason why it wouldn't be. Unlike the US, Canada doesn't recognize the concept of an ultralight helicopter, so you'd need a regular helicopter license to actually fly it.


How are helicopter rotor blades balanced?

Most blades are as close as possible when built at the factory. Yes, it is like a car wheel you use weights to balance. For the Blackhawk helicopter there are inserts on the hub near the blade to add weights. But additionally there are a maximum amount of weight that can be added. If you're unable to balance the main rotor head, sometimes you have to switch blades around to other sides and adjust weights. If it still doesn't balance usually it is due to the installation of the hub to the main transmission then gaps have to be measured.


What are the factors that determine the speed flutter appears on wings?

It's an aeroelastical phenomenon driven by pitching moment, torsion stiffness, and inertia of the wing. It's a classical spring-mass-damper problem: increased aerodynamic pitching moment causes torsion on the wing structure, which causes more pitching moment until the local airfoil AoA is such that the air flow separates. Torsion is counteracted by the wing torsional stiffness, thin wings have less torsional stiffness.

Parameters that determine flutter speed:

Wing profile: aerodynamic $C_m$ and wing thickness
Wing aspect ratio
Number of jet engines mounted forward of the aeroelastic axis
Wing sweep


How to calculate the flight envelope and maneuvering envelope for the B727-200F?

Start with the appropriate sections in FAR part 25. The link is to the current version - you will probably collect bonus points if you dig up the version from the Sixties which was current when Boeing applied for the certification of the 727-223. Once the application is started, the rules remain relevant for that particular type - that is why Boeing redesigned the 737 several times over but kept the old name and the certification regulations that came with it. This is called Grandfather policy.

Calculate the minimum speed curve over load factor, then draw the v-n-diagram and the gust lines for 56 ft/s vertical gusts at sea level and repeat with 44 ft/s gusts at 15,000 ft, decreasing to 20.86 ft/s at 60,000 ft for the current version. Older versions used gusts of 50 or 66 ft/s from sea level to 20,000 ft, decreasing to 25 or 38 ft/s between 20,000 and 50,000 ft - the lower level is for the Sixties, the higher one for the Nineties. Note where the  minimum flight speed line will cross the maximum load factor - this is where your $\text{v}_A$ should go. Next, the limit speed in turbulent weather $\text{v}_B$ is determined by the point where the gust line will reach your maximum load factor. Cruise and dive speed are more tricky, but the limit Mach speeds are even listed in Wikipedia or on Airliners.net.

The negative side will involve some speculation unless you have been given a minimum lift coefficient - use 0.7 times the maximum clean value if you have nothing else. Use the intersection of the minimum lift line with the -1g line to continue horizontally and reduce the envelope between $\text{v}_C$ and $\text{v}_D$ from -1g to 0g, and you are done.


What kind of liquid can be seen 'leaking' from the bottom of a Boeing 737-800 engine?

There is really no telling without being there & getting a sample of the fluid.  A mechanic can tell the differnce between hydraulic fluid vs engine oil vs fuel vs etc, but the place where any of them would come out is essentially the same spot under the engine.

In general, any of the above is uncommon but far from unheard of, and in small amounts is no big deal.  The fittings aren't supposed to be leaking, so a mechanic will probably end up fixing whatever it was, but the hazard from a few drops just isn't all that great.  Sure, the idea of "oh, just a fuel leak, no big deal" intuitively sounds pretty bad, but the fact of the CFM engine is that the motor is incredibly tolorant of this sort of thing with nothing bad actually happening.  It needs to be checked out because something isn't exactly right, but there would have to be several other things go wrong as well (each of which is pretty rare) before anything bad actually happens.

Some lines are allowed no leakage at all, while others actually do have a "drops per minute" limit for what is allowed without needing maintenance action.  Not being a 737 mechanic, I couldn't tell you offhand which fluids are in which category.  If I see it leaking, I call the mechanic & he can sort it out.

Of course, in the days of the big radial engines, the saying was that when it's leaking, that means there's still fluid in it, and when it stops dripping, THAT is what's bad, because that means you don't have any more oil!

We're a long, long ways from those old days!


Should one use mainly the rudder or the ailerons combined with rudder to go back to center line on short short final?

Rudder.  It is amazing how much even a tiny puff of wind can move the nose off line.
If you are on "short short", just clearing the fence, your momentum will carry you onto the runway even if you are almost sideways. (But this is not good for the landing gear).
Most important here is to round out correctly at the proper airspeed (the earlier you get your approach speed right the better).
It is not unusual at all for the nose to move offline, keep flying the plane all the way down using rudder corrections to hold the nose to the line.
Only if your plane drifts towards one side or the other do we need ailerons, and this is how we do a crosswind landing:  aileron holds drift, rudder holds line.
A light GA aircraft will usually pivot faster than it will drift.
The physics is that the torque turning it requires less force than to move the whole thing sideways.
But air is rarely completely calm, so be ready to use your rudder and ailerons and continue using them until the wheels stop.


Can reverse-thrust be used to push back from the gate?

It has been done before but is generally frowned upon due to high fuel consumption, equipment FOD caused by debris kicked up by the fan exhaust and intake suction dangers.  It is just simpler and safer to connect a powered tug and give the aircraft a pushback.

But yes, you can pushback using thrust reversers.


Why does ETOPS not apply to older 4 engine aircraft?

I think it's because the last 747-400 was built in 2009.

  §121.162   ETOPS Type Design Approval Basis.

  Except for a passenger-carrying airplane with more than two engines manufactured prior to February 17, 2015 and except for a two-engine
  airplane that, when used in ETOPS, is only used for ETOPS of 75
  minutes or less, no certificate holder may conduct ETOPS unless the
  airplane has been type design approved for ETOPS and each airplane
  used in ETOPS complies with its CMP document as follows:

  (a) For a two-engine airplane, that is of the same model
  airplane-engine combination that received FAA approval for ETOPS up to
  180 minutes prior to February 15, 2007, the CMP document for that
  model airplane-engine combination in effect on February 14, 2007.

  (b) For a two-engine airplane, that is not of the same model
  airplane-engine combination that received FAA approval for ETOPS up to
  180 minutes before February 15, 2007, the CMP document for that new
  model airplane-engine combination issued in accordance with
  §25.3(b)(1) of this chapter.

  (c) For a two-engine airplane approved for ETOPS beyond 180 minutes,
  the CMP document for that model airplane-engine combination issued in
  accordance with §25.3(b)(2) of this chapter.

  (d) For an airplane with more than 2 engines manufactured on or
  after February 17, 2015, the CMP document for that model
  airplane-engine combination issued in accordance with §25.3(c) of this
  chapter.

  §25.3   Special provisions for ETOPS type design approvals.

  (a) Applicability. This section applies to an applicant for ETOPS type
  design approval of an airplane:

  (1) That has an existing type certificate on February 15, 2007; or

  (2) For which an application for an original type certificate was
  submitted before February 15, 2007.

  (b) Airplanes with two engines. (1) For ETOPS type design approval of
  an airplane up to and including 180 minutes, an applicant must comply
  with §25.1535, except that it need not comply with the following
  provisions of Appendix K, K25.1.4, of this part:

  (i) K25.1.4(a), fuel system pressure and flow requirements;

  (ii) K25.1.4(a)(3), low fuel alerting; and

  (iii) K25.1.4(c), engine oil tank design.

  (2) For ETOPS type design approval of an airplane beyond 180 minutes
  an applicant must comply with §25.1535.

  (c) Airplanes with more than two engines. An applicant for ETOPS
  type design approval must comply with §25.1535 for an airplane
  manufactured on or after February 17, 2015, except that, for an
  airplane configured for a three person flight crew, the applicant need
  not comply with Appendix K, K25.1.4(a)(3), of this part, low fuel
  alerting.


Has fuel boiling ever been an issue for high altitude aircraft?

Yes, e.g. U2

  Both planes, equipped with the older -37 engines, landed at Kirkland Air Force Base Albuquerque, New Mexico. After each development flight, a careful accounting is made of fuel consumption. A special fuel, dubbed lighter fluid, was developed by Shell Oil Company specifically for the Angel, and the finished product was shipped to Nevada in tank cars labeled LF 1A. This blend will not boil at the low pressures encountered at altitude, yet will still give adequate air starts. It is so involatile that fire seldom follows a mishap.

  A simple 100 gallon-slipper tank has been developed to fit each wing for extremely long flights. These pressurized tanks contain enough fuel to carry the Angel to cruising altitude where they have no significant effect on speed or range. Even after the addition of an external drag chute, three times the normal oxygen supply, improved breaking and an autopilot, the final all-up weight was within ten pounds of the original proposal.

https://www.cia.gov/library/video-center/video-transcripts/u2-developments.html


How do you hold at a non-towered airport?

There's no "standard holding pattern" at any airport, towered or not. If the runway is occupied or temporarily closed for some reason, you might was well leave the traffic pattern and go putt around for a while someplace where there are fewer aircraft. At a towered airport, the controller will likely tell you what to do - but again, you can make both his life and yours easier by just leaving the pattern and going somewhere else until the situation is resolved.


Why do we lean the mixture in a turbocharged airplane (C182T)?

Turbo or not, you lean mostly because the mixture required for takeoff is far richer than necessary for lower power settings, even at sea level.  Aircraft engines are partly air cooled and partly liquid cooled - the full-time liquid cooling is oil, and on takeoff, there is part time liquid cooling in the form of excess gasoline from the full rich mixture.
The reduction in air pressure with altitude, or density with heat, means this effect becomes more extreme the higher you go, but you should be leaning, even at sea level, once power is reduced from takeoff (you should be leaning on the ground as well as soon as the engine is running smoothly after start, until just before takeoff, if you want to best mitigate the effects of the lead in the avgas).
The turbocharger just fools the engine into thinking its altitude is lower than it really is. A cruise power setting of 22" of manifold pressure is 22" inches of manifold pressure to the engine, whether it's 22" of natural atmospheric pressure achieved at wide open throttle at 8000 ft on a non-turbo engine, or 22" of artificially produced manifold pressure at 15000 ft in the turbocharged one.
The density of the compressed air intake charge is reduced by compression heating of the charge by the turbo, which reduces its efficiency (you'll need a slightly wider throttle opening to get the same MP with a hot charge) and complicates cooling (the hot air reduces detonation safety margins). Intake intercoolers are used to reduce the temperature of the intake charge, without reducing the pressure, to mitigate this problem.
In all cases, leaning is done in reference to exhaust gas temperature, usually some value on the lean side of peak EGT to get best fuel economy and relatively cool cylinders, with an eye on cylinder head temperatures.
With a turbo, the main effect of altitude that has to be kept in mind is cylinder cooling efficiency.  The turbo gives the engine an artificial ability to make low altitude power at high altitude. The problem is although the intake charge is "thick", being compressed air, the air coming in to cool the cylinders is "thin" and the heat rejection rate via the cooling fins declines, so leaning and cowl flap settings need to take this into account in managing cylinder head temperatures.
Exactly how that is to be done depends on the engine/airframe, per the POH and you should be leaning at all times based on POH procedures.
Cooling efficiency is critical to cylinder life with turbocharged engines, because they tend to operate a lot closer to temperature margins because of the demands of cooling in thin air. Good engine baffling is key.  Badly installed baffles or degraded baffle seals, that wouldn't be a problem in a non-turbo installation, can cause high cylinder head temperatures with a turbo at higher altitude.  Even if the cylinder head temperatures are good, bad baffles can lead to hot spots not picked up by the CHT probes and can ruin a cylinder with no obvious outward signs until it's too late.


Are there any standards on the dimensions of PFD symbols?

Yes there are standards. There are industry standards which not regulatory standards, but they have been deemed acceptable by the regulatory agencies (e.g. FAA). So following them is usually accepted without issue.

The FAA also provides guidance in the form of an Advisory Circular, AC 25-11B Electronic Flight Displays.

You have two separate things to address; the actual display hardware and the displayed content.

The standard for the hardware is SAE Aerospace Standard AS8034B, Minimum Performance Standard for Airborne Multipurpose Electronic Displays.

The rest is covered under a group of SAE Aerospace Recommended Practice (ARP) documents. The top level is ARP4102, Flight Deck Panels, Controls, and Displays. Under it are several Volumes and Appendices.

ARP4102-7, Electronic Displays, covers the general requirements for what must be displayed.

ARP4102-7 Appendix A, Electronic Display Symbology for EADI/PFD, covers the details for the PFD. Appendix B covers the EHSI/ND and Appendix C covers the Engine displays.


Can anyone help me with the Make, Model (version), and Unit of this WWII army trainer. Appears to be an AT-6 version

That is a North American NA-36, BC-1, a North American NA-16 derivative, the predecessor of the  North American T-6 Texan

Source: nationalmuseum.af.mil
Some observations that helped to determine the precise model:

The fuselage is covered with fabric. Later models used metal

The trailing edge of the rudder is rounded, later models had a straight rudder

The bottom corner of the rudder is squared, some other models are rounded (e.g BT-9)

The fuselage shows the crest of the USAAF's Technical Training Command:

Source: Picturing Meteorology. The text "Sustineo Alas" is latin for: "I sustain the wings", or more loosely translated: "I keep em flying"
The aircraft belonged likely to Chanute Field Technical Training Command (Illinois), located some 200 miles south of Madison.


I'll use the start sequence of a JT-9D on a 747-200 as an example. It's typical, and since there was no FADEC and since it took two people having to manually do the individual items that will better explain things.

The f.e. turns on the engine ignition switches to energize the igniter that will ignite the fuel when introduced.

The figure doesn't show the next step, that of starting the engine rotating. The f.e. did that by opening the start valve which directed pneumatic air into the starter. Starter operation was confirmed by the f.e. observing N2 rotation—the figure calls that the compressor. Some gas turbines use an electrical starter rather than a pneumatic starter.

At 30% N2 rotation, the captain opens the fuel valve and light-off occurs. The captain and the f.o. monitor the EGT to confirm light-off and to avoid an overtemp—the figure calls that the Peak Starting EGT.

At 50% N2 rotation, the engine can accelerate on its own. The f.e. turns off the igniter and closes the pneumatic vale supplying air to the starter.

The engine continues to accelerate on it's own to idle rpm.

All sorts of things can go wrong, and you practiced those things in the sim, and occasionally you had to contend with them in real life.


Would a pilot know that one of their crew is armed?

The answer to this question is protected as Sensitive Security Information (SSI) and can't legally be disclosed here.  Anyone who does answer the question either doesn't know what they are talking about, or faces steep legal consequences.

Many, even most, questions relating to airline security (in the US at least ) are similarly handicapped.


Are there tricks or training to handle spatial disorientation?

The issue with spatial disorientation is that sensory input is insufficient (based primarily on vestibular input) or that the pilot fails to properly process sources of valid orientation.

Generally, when we refer in aviation to spatial disorientation, we really mean attitudinal disorientation.  (Spatial disorientation could also mean not knowing where we are relative to a fix or navaid, as an example. Rather we are really interested in pitch and roll.)

Primary input for attitudinal orientation is an artificial horizon, which emulates a visual horizon providing pitch and roll information. Secondary input can come from a combination of altimeter, turn indicator, and variant instruments (VSI, DG).

With respect to techniques and practice, the standard method is developing a discipline to rely on the AI and associated instruments, and to force a reliance on the instruments, particularly when the pilot senses a conflict. Some people acquire this discipline quickly and others take longer. The general standard for teaching is to continue to provide practice and diverse evaluation opportunities, until the pilot demonstrates consistent correct behavior.

Assuming primary and instrument students are acquainted with the basics, I tend to employ frequent "unusual attitude" opportunities. My experience has been that students who perform well under stress, generally perform well without stress. Unusual attitude opportunities can be instructor induced opportunistically, such as when flying to and from the practice area. When putting on foggles, I customarily will have the student raise their head up after having "reoriented" the aircraft. This may happen 4 to 10 times, sometimes more, in a lesson, and generally students get very proficient.

An alternative technique, which is often done on student cross countries, is to have the student close their eyes, and continue to try to keep the plane straight and level, and then command them to open their eyes once some attitudinal change has presented itself. (There is a secondary benefit to this method, and that is it encourages proper trim maintenance.) If the student has a view limiting device on (foggles) then they get the opportunity to recover using instruments. If they do not have a view limiting device, then they can benefit from both instruments and outside reference.

These things can be practiced with a simulator, however, unless you have a Level D simulator (full motion) there is little opportunity for false vestibular input, and there is little benefit. Besides, nothing beats pulling 1.5Gs and hearing the wind pick up, and sensing the sunshine moving around in the cockpit to get a student's interest up prior to opening their eyes to begin the recovery.

So the best answer to practice is to have your CFI provide frequent, varied, and sometimes stressful opportunities. In my experience, I have never had a student who could not master recoveries, even with nausea inducing preludes.


Can a 737 be on final at 160 knots, and also touchdown at 160 knots?

You fly final approach at the "reference speed" (Vref) for the flap setting which varies with weight.  You will normally set up the reference speed for full flap on the speed bug on the speed tape on the primary flight displays, and on final while the autopilot flies the glide slope you will modulate thrust to hold the approach speed (or let the autothrottle do it if equipped).

For a given landing weight, the reference speed for full flap is worked out from the "speed book" or "speed cards" which the crew usually has handy on the center console.  The airplane on short final with landing flap will be going at Vref, which is usually well below 160kt, typically between 110 and 150 kt for different airliners at different weights.

As you cross the end of the runway and pass through 50 ft, you should be at Vref.  As you get close to the surface and start to flare to land, you reduce thrust to idle at some point (the technique varies with the airplane) and as you hold it off the speed will bleed off as you trade inertial energy for reduced sink rate in getting a gentle contact with the runway.  In most jets you want to be at idle before touchdown, with exceptions.

So in the interval from when you started to flare and reduce thrust, and the actual touchdown occurs, you are coasting along, settling gently as you pitch up to trade inertial energy for reduced sink, with the speed bleeding off as you do so. At touchdown you will be below Vref, perhaps 10-20 kt.  So if a 737s Vref for a given landing weight was some number like (wild guess) 135 kt, by the time it makes ground contact, depending on how much effort the pilot put into holding it off trying to get a gentle touchdown, it'll be doing perhaps 125-130 kt.

In any case, touchdown speed is always below the approach reference speed, unless the pilot just flies into the runway like a carrier landing, which will get lots of people excited.

160 kt on short final is pretty fast for most jets, but you could be going that fast if the flaps had failed while retracted or at an intermediate position and you had to use a higher approach speed (on the CRJ200, the reference speed with flaps failed fully retracted, which they do from time to time, is about 165 kt +/-).  Same thing though; during the landing itself, the touchdown speed should be less than the final approach speed due to the energy conversion process of the flare and touchdown.

If your reference speed was 140 kt and you crossed the threshold at 160, yes you would float quite a bit if you used normal landing technique. You would also get sent for remedial training.  If you tried to drive it on at that excessive speed, there is a good chance you would have nose wheel contact first (called a wheelbarrow), which would get people even more excited.


Do presidential aircraft use additional call signs?

When multiple U.S. military aircraft are operating in formation, they do so as a "flight". This flight has a callsign, and in the case of Presidential transport flights, this callsign is the Presidential one, such as Air Force One or Marine One.

For POTUS transport using a fixed-wing aircraft, the flight typically consists of a single aircraft, usually one of the VC-25s specifically built for the purpose. Its fighter escort, if any (typically there is one), is a different "flight" that operates in tandem with Air Force One as the escort "element" of the complete transportation "package". Therefore, for Air Force One and for Navy or Executive fixed wing equivalents, the aircraft is the flight and has the callsign.

When the "Marine One" helicopters must be used, however, a very sophisticated "shell game" is played, as you already know. Not only are multiple helicopters used (I've seen up to 6 in use at the same time), they are externally identical in appearance, and they change position in the flight formation constantly. The Secret Service has even gone so far as to use body doubles that would make positive ID of the helicopter the actual President has entered difficult, even if an enemy faction had spotters in place to track each individual helicopter's position in the flight the whole time it's in the air.

This entire flight of multiple helicopters is what carries the "Marine One" callsign. Individual aircraft within the flight, if typical military radio procedures are followed, would be identified by adding a craft number suffix: "Marine One-One", "Marine One-Two", etc. I don't know whether the aircraft change craft numbers during flight to match formation position, or if the pilots just keep track of which chopper's where as they juggle.

So, a potential assassin would either have to take a 50-50 shot (or worse) at one of the choppers in the flight, or he'd have to coordinate with multiple launchers to attack all the choppers simultaneously (and the larger the effort, the more communication is required to plan and execute it, which increases the group's exposure and the potential for detection). If there is any reliable intel that the President would be targeted with this level of sophistication during a visit, he usually doesn't go; he has a VP, a Secretary of State and a cadre of ambassadorial representatives whose job it is to personally represent the President anywhere in the world the President himself cannot be, for any reason.


What is the content of a Letter of Agreement between the Collaborative Decision Making participants?

First, a little bit about CDM and the participants that make up the team.  The FAA's CDM Website provides the following overview:

  Collaborative Decision Making (CDM) is a joint government/industry initiative aimed at improving air traffic flow management through increased information exchange among aviation community stakeholders. CDM is comprised of representatives from government, general aviation, airlines, private industry and academia who work together to create technological and procedural solutions to the Air Traffic Flow Management (ATFM) challenges faced by the National Airspace System (NAS).

This "team" of government/industry representatives is called the CDM Stakeholder's Group (CSG). There is a "Membership Agreement" that all parties of the CSG sign. This agreement outlines the roles and responsibilities of the FAA and each CSG member. It provides "rules" and processes for exchanging data and resolving disputes should any arise. It outlines the methods by which to modify the agreement, and how long the agreement should last.

A sample of the agreement letter that the FAA provides to each stakeholder member of the CSG is available to view here: http://cdm.fly.faa.gov/wp-content/list_yo_files_user_folders/cdm_editor/cdm_doc/CDM%20MOA.docx


What are the fins near the tail of a helicopter called?

You can call them horizontal and vertical stabilizers, since that is exactly what they do, in forward cruising flight.  The vertical stabilizer is there because the tail rotor itself doesn't provide as strong a weathervane effect as a fixed surface. So it stops the nose from oscillating left and right in forward flight same as the stabilizer in an airplane.

The horizontal stabilizer is to provide some down force to keep the body angle a little more level in cruise flight.  The rotor disc is flying along doing its thing with this big weight under it, which wants to swing back and pitch the nose down from air drag and the forward movement of the suspension point (more or less like running along with a tennis ball suspended on a string - it swings back and stays at an angle until you stop running).  The horizontal stabilizer's down force counteracts some of this and helps dampen pitch oscillations and keep the nose at a more desirable (higher) attitude.


What is the relationship between the code of an Area Control Center (US) and associated Flight Information Region?

KZDC is the FIR associated with the ZDC ARTCC.  Think of KZDC as the airspace itself (the flight information region), and ZDC as the facility which services it.


About climb: If we use T/W as input, the second grade equation yields two solutions for W/S. Are both solutions realistic?

Raymer's G is a little unusual. In effect, it is the tangent of the flight path angle $\gamma$, and since his equations are for small values of $\gamma$, we can assume that it is approximately equal to $sin\gamma$ or $\gamma$ itself when expressed in radians.
$$G \approx \gamma$$
Next, the expression $\pi\cdot AR\cdot e$: This is part of the square root of the lift coefficient for minimum drag. The complete equation is:
$$c_{L\:(minimum\:drag)} = \sqrt{c_{D0}\cdot\pi\cdot AR\cdot e} = c_{L\:(md)}$$
Next, I need to express that thrust-to-weight ratio differently. As long as we keep $\gamma$ small:
$$\gamma = \frac{T}{W} - \frac{c_D}{c_L} => \frac{T}{W}-\gamma = \frac{c_D}{c_L}$$
Now I can rewrite the equation of your first question:
$$\frac{W}{S} = q\cdot\frac{\frac{c_D}{c_L}\cdot \frac{c^2_{L\:(md)}}{c_{D0}}}{2} ± q\cdot\frac{\sqrt {\left(\frac{c_D}{c_L}\right)^2\cdot\left(\frac{c^2_{L\:(md)}}{c_{D0}}\right)^2 - 4\cdot c^2_{L\:(md)}}}{2}$$
and when I restrict the equation to the minimum drag point where $c_{D0} = c_{Di}$, I can write
$$\frac{W}{S} = q\cdot c_{L\:(md)} ± q\cdot\sqrt {c^2_{L\:(md)} - c^2_{L\:(md)}}$$
Fancy that! The expression under the root becomes zero when I look at the polar point of minimum drag! The only variable term under the square root is the ratio $\frac{c_D}{c_L}$, and it reaches its minimum at the $c_{L\:(md)}$ point. When I move away from this polar point, I should get two valid solutions.

I guess these two wing loadings allow to fly with the specified flight path angle at the given polar point and thrust-to-weight ratio. Since the weight is prescribed by the thrust-to-weight ratio, the solution is actually for two different wing areas. The smaller wing requires a higher speed and the larger wing a smaller speed than what you get at the lowest drag point. Between both, the speed and wing area should result in configurations which achieve a higher flight path angle $\gamma$, and outside of this interval no level flight should be achievable with the resulting wing areas and speeds.

I cannot follow how you arrive at the second question. The term under the square root should be
$$\left(\frac{T}{W}\right)^2 - 2\cdot\frac{T}{W}\cdot G + G^2 ≥ \frac{4\cdot c_{D0}}{\pi\cdot AR\cdot e}$$
But when I insert again as explained above, I can write for the term under the root:
$$\left(\frac{c_D}{c_L}\right)^2 - \frac{4\cdot c^2_{D0}}{c^2_{L\:(md)}}$$
so the condition for a positive root is
$$\frac{c_{D0}+c_{Di}}{c_L} ≥ \frac{2\cdot c_{D0}}{c_{L\:(md)}}$$
or
$$ \frac{c_{D0}}{c_L} + \frac{c_L}{\pi\cdot AR\cdot e} ≥ 2\cdot\sqrt{ \frac{c_{D0}}{\pi\cdot AR\cdot e}}$$
which is certainly true; both sides of the equation are equal at the lowest drag polar point and away from it the left side is bigger and the right side stays constant.

If you just isolate the term under the root and look at it by itself, I doubt you have something that corresponds to a realistic configuration. You need to extract both numerator and denominator to keep the physical analogies intact. What Raymer does is to look at the term under the root in isolation and then postulates that the first summand must be larger than the second. He puts both on the two sides of an inequality and extracts the roots on both sides separately. Then he moves G over to the other side. There is no second version of the inequality possible.


Is a lapsed Advanced Ground Instructor certificate acceptable to use as proof of FOI when taking CFI initial?

That would be 61.183(e)(1):

To be eligible for a flight instructor certificate or rating a person
must:
(e) Pass a knowledge test on the areas listed in Sec. 61.185(a)(1) of
this part, unless the applicant:
(1) Holds a flight instructor certificate or ground instructor certificate issued under this part;


How can a Cessna cut the wing of a Boeing?

An airliner wing is built to be as light as possible. Its strength is calculated to withstand the stresses of flying, i.e. lift equally distributed over the wing, bird strikes on the leading edge.

The wing consists of one or more spars from the fuselage to the wingtip, ribs perpendicular to the spars and skin panels. All of these are made from thin aluminium: the spars (the main loadbearing structure) are a few mm thick outside the landing gear and engines.

Fire a one-ton object into the wing at a few hundred km/h and you can do a lot of damage. Even if that object is another aircraft with similar construction.

The damage gets worse if the wing hits the Cessna's engine block, but the accident descriptions I've seen don't say if that was the case.

Don't assume the animation is accurate. The Cessna won't slice cleanly through the wing, there would have been a collision in which both structures are crumpled and roughly torn apart.


How can I rebuild my missing logbook after 20 years of not flying?

You will probably not be able to recover any solo flight time you have completed to this point, but contact your previous flight instructors in Illinois.  They should have logged the training time they did with you on dual instruction, which will allow you to recover that flying time this way.

If you don’t have contact information on this instructor, you may be able to search them out, either on the FAA’s website or third party flight instructor directories like this one.

http://www.iflightplanner.com/FlightInstructors/

Good luck


The phenomenon is called trimming.

This is the process by which the pilot adjusts the lift at the tail surface to shift the center of pressure right above or below the center of gravity and removes any stick force so the airplane will keep this attitude unaided.

If the center of gravity (CG) is right above or below the aerodynamic center (AC), the aircraft's longitudinal static stability is indifferent. Move it forward and stability increases, move it further back and the plane becomes unstable. The aerodynamic center is where the angle-of-atttack-dependent lift forces act, and in an indifferent configuration the lift coefficient on wing and tail will be equal. Increasing stability thus means to reduce lift at the rear surface, and if a lot of stability is desired, lift at the rear surface will become negative.

When the airplane is hit by a gust (change in vertical wind speed), the angle of attack at both wing and tail will change by the same amount. Now it is important how much lift changes relative to the lift before the gust. If the lift coefficient on the wing is larger than on the tail, the same amount of angle of attack change will cause a relatively smaller change of lift on the wing than on the tail, and the center of pressure will move such that it causes a correcting pitch moment.

By selecting the proper center of gravity location, the pilot can adjust the level of stability he/she desires. To stay at the desired attitude in flight, he/she now has to move the incidence of the empennage (or the elevator deflection) to a point where any pitch moment disappears. The consequence is a downforce on the tail if that is what it needs to trim the aircraft with the given center of gravity location.


Where can you join a STAR & STAR Altitudes?

You can only file, and ATC can only assign, one of the listed transitions. However, that doesn't mean you will actually fly it as charted (unless you lose comms). If you filed lower than the charted altitudes, you are not expected to climb. In practice, ATC mau give you direct a later fix (e.g. FZT) where you'll join aircraft descending to your level. Or, if you're slow, they might put you on vectors off the STAR to keep you out of the way of faster traffic. It all depends on what else is going on around you, so it's difficult to predict what will actually happen.


Aerodrome actual weather - METAR decode - 3 letters for this sky?

This work sheet may be of use and generally the system of Okta is used to denote coverage in a Metar, but I would say

  L1 Clouds: Cumulus (Cu) with little vertical extent

but it could also be

  L5 Clouds: Stratocumulus (Sc) not from spreading out of Cumulus (Cu)

But I will agree with Ron on this one, its BKN (5-6 Okta based on the picture in my opinion)


Areodynamics of ancient flying machines. Did they really worked for them?

Just a few points:

You are yourself conceding that these are from mythology. If something is from mythology, it is (almost) certainly a myth.
Description of a fictional flying machine and explaining their principles of operation are completely different. To the best of my knowledge, none of these texts even try to explain the principle of operation.
Actually, there was a study carried out on one of these texts, which thoroughly debunked the claims made and concluded,

  ... the planes described above are (at) the best poor concoctions, rather than expressions of something real.None of the planes has properties or capabilities of being flown; the geometries are unimaginably horrendous from the point of view of flying; and the principles of propulsion make then  resist rather than assist flying.


Does propeller size affect total drag force of plane?

the drag force that a propeller generates while under power is expressed as a torque applied to the engine's crankshaft and arises because of skin friction on the propeller blade surfaces. as long as the prop is generating net thrust it is not generating drag in a direction opposite to its direction of travel.
Prudent design of the prop blades guarantees that no portion of the blade is ever generating backwards thrust for all possible combinations of airspeed, RPM, and blade pitch.
A propeller that is not generating thrust is generating drag which does act against the airplane's direction of travel.


Is it possible to takeoff without flaps extended?

Yes take-off without flaps is possible. The Airbus A300 and Boeing 767 are approved for such take-offs and it is being done regularly. It results in a better climb gradient, especially with one engine out. The one engine out climb gradient is an important and sometimes limiting factor in take-off calculations.

One important constraint is the length of the runway.

Another limitation, perhaps less obvious, is the maximum rolling speed of the wheels. The tires are rated to a limited speed which may be exceeded by a flap-less take-off.


What is the meaning of R88/70D in this METAR from Ashgabat International airport?

I assume it was a typo, as R88/70D is not a correct METAR format. According to this website with historical METARs the METAR of today at 1300Z at UTAA was:

  METAR UTAA 071300Z 13006KT 9999 FEW050CB BKN050 BKN100 15/06
             Q1013 R88/CLRD70 NOSIG=

All other METARs from UTAA today contain "R88/CLRD70 " as well.

R88/CLRD70 means: all runways are cleared (no more deposits), and a friction coefficient of 0.70.


How do I find the floor of controlled airspace on sectional charts?

It does not say it anywhere because the answer is not variable like class B airspace but lets dig in.

The question here is really trying to get you to identify the airspace that surround Coeur D'Alene Airport and we can see the dashed magenta line encircling it. If you take a look at the legend you will see that denotes

  Class E (sfc) Airspace.

The same goes for Sandpoint Airport which is surrounded by a faded magenta line. The legend again denotes

  Class E Airspace with a floor 700ft. above the surface


What are the procedures for flying supersonic over international waters?

As a non-commercial civilian, the high seas (international waters) do not exempt you from the local governing rules: the civilian FIR boundaries meet over water, and there is no free-play gap in between. This goes as far back as 1948:

  Flight over the high seas. It should be noted that the
  Council resolved, in adopting Annex 2 in April 1948 and
  Amendment 1 to the said Annex in November 1951, that the
  Annex constitutes Rules relating to the flight and manoeuvre
  of aircraft within the meaning of Article 12 of the Convention.
  Over the high seas, therefore, these rules apply without
  exception.

If your plan is to fly VFR and not file an IFR plan with the appropriate ATS authority, then you can't fly supersonic (unless authorized):

  4.4 Unless authorized by the appropriate ATS authority,
  VFR flights shall not be operated:
  a) above FL 200;
  b) at transonic and supersonic speeds.

Reference: ICAO Annex 2 (Rules of the Air).

Note: Consult the local AIP for listed deviations from Annex 2 if the country of operation is an ICAO member.


Do airliners have horns for use on the ground?

(Source) Ground call horn.

There's a horn the pilots can sound to attract the attention of the ground engineer, so they can talk on the intercom (by wearing a headset). It's not loud enough to have any effect in the air—or when the engines are running loudly.

It's more of an annoying alarm really.

Taxi lights can be flashed on/off to attract the attention of ground crew, also opening a window and waving would work.

(Source)

(Source) Ground crew member wearing a headset connected to the plane.


What is the meaning of "transition area" as used by the FAA? Has the meaning changed over time since the term was introduced?

As per the FAA Procedures for Handling Airspace Matters:

Transitional areas, Class E, are designated to serve terminal and en route aircraft to include helicopter operations such as:
a. Transitioning to/from terminal and en route.
b. Transiting between airways and routes.
c. En route climbs or descents.
d. Holding.
e. Radar vectors.
f. Providing for course changes.
g. When the route under consideration is almost all within existing Class E airspace and small additions would complete the coverage.
NOTE-
The only areas that are normally excluded in the Class E description should be limited to Mexico, Canada, SUA and international airspace. Exclude SUA only when active. Do not exclude Federal Airways or other airspace areas.
h. En route training operations.

Link here.
I don't know that this definition has necessarily "changed", but they apparently thought it needed clarification in 2011.


Would using a drone to pay for something count as commercial use?

Laws around drone use are very new, and the only way to be certain about this is to have a case come to trial. You probably don't want to be the person it comes to trial over. A lawyer would give you a much better interpretation, but even they can't be sure.

If you are interested in my personal uninformed opinion (IANAL) then I think it would not count as commercial use. My reasons are:

The drone is completely incidental to the transaction. The cashier would do exactly the same if you showed up in person on foot or in a car, or if you sent someone else to make the transaction.
If you drive your car to McDonalds, that does not count as commercial use of your car. If you fly to McDonalds  then that does not count as commercial use of an aeroplane.


It looks like the nose skin panel with the gun ports that some T-33s had.  So I'd be willing to put serious money down on "yes".

Lockheed T-33 Shooting Star ‘69330 / TR-330’ (N651)
Alan Wilson from Stilton, Peterborough, Cambs, UK


How did a Soviet SA-3 missile manage to shoot down the F-117 Nighthawk?

"Stealth" does not mean invisible. In fact, there are photographs of F-117s, so clearly, they are visible.

Stealth means less observable than a comparable non-stealth design. A stealth aircraft still has a radar signature, it still generates heat, it still generates noise, and it is still visible … just less so than a non-stealth aircraft.

In this particular case, there was a combination of several factors:

The F-117 was the first production stealth aircraft. A lot of things weren't known by then, for example how to integrate sensor pods, radomes, etc. into the faceted hull in such a way as to not negate the stealth characteristics. As a result, the F-117 was pretty starved for sensor data, for example, it didn't have a radar warning system. The pilot literally didn't even know that he was overflying a missile station until he saw the missiles coming at him through the clouds.
The F-117s were flying exactly the same route at more or less exactly the same time night after night. That's just shoddy mission planning.
The bomb bay is a huge radar reflector, with the doors open, the plane is no longer stealthy. (This is still true for the B-2, BTW.)

So, since they flew the same route every night, it was likely that someone, somewhere would just simply spot or hear them by accident. No matter how stealthy your aircraft is, if someone looks up and you pass between them and, say, the moon, they will see you. Since the route was known, the Yugoslav Army could move their missile station right into the flight path. Since they were also repeatedly bombing the same targets, the Yugoslavs could even make an educated guess at which point the bomb bay doors would be open. They also only had to turn on their radars for short periods of time (again, since they already knew roughly when and where the airplane would be), making it harder to detect them.

And once the missile hits you, it doesn't really matter how old it is. Kaboom is kaboom, regardless of age.

So, to summarize, it was a combination of

bad mission planning
limited sensor capabilities of the F-117
a very clever missile commander (credit where credit is due!)


Which FAA certifications may be used as a name suffix and how are they properly used?

I don't know that there's any kind of official rule about what name suffixes a person may use. I suppose as long as he is not being subversive then there's no problem.

These would fall under the "professional" suffix category and like many suffixes may only be recognized by people familiar with a certain industry. For example, CISSP or CISM may only be recognized, ie. they know what it stands for, by those who work in information technology and other related fields.

If it isn't a professional FAA certification, then obviously, it shouldn't be used as a suffix.  I have seen the following used as a suffix or listed as a desirable qualification:

CFI, CFI-I, CFI-G and MEI
AGI, BGI, IGI
ATP, ATP-R
DPE

There is, however, a point that shouldn't be missed;  you won't see pilots going around signing documents and adding suffixes at the end of their name like a doctor, but it is usually a way of conveying to an audience what that person's qualification or source of legitimacy is such as on a business card, advertisement, or flight school staff page.

A commercial pilot would not use that qualification like a suffix because it is not commonly abbreviated, and without any other qualification that would imply that a commercial certificate is held, they are extremely limited on what they can actually get paid to fly for. Therefore, the advertising aspect is irrelevant because there is virtually no public target audience.

The lack of a public advertising target also goes for certificated flight dispatchers.


Short answer: log it however you like as long as you log it.

According to the FAA:

  When the applicant has successfully  completed the review, the CFI
  should endorse the pilot’s logbook to certify that the pilot has
  satisfactorily accomplished the flight review.  The CFI should make
  the endorsement for a  satisfactory review in accordance with AC 61-
  65. The flight and ground time must also be  logged in the pilot’s logbook in  accordance with § 61.51(a)(1)

61.51(a)(1) simply says that "Training and aeronautical experience used to meet the requirements for a certificate, rating, or flight review of this part" must be logged.

So you do have to log both ground and flight time, but exactly how you do that is really up to you. The FAA doesn't require any specific logging format as long as the information is correct and CFIs, DPEs and others can see what they need to see.

Personally, I would note the ground time beside the CFI's endorsement and then log the flight time as I would for any other training flight. I've never met anyone who logged their 'ground instruction' time precisely (simulator time is a different story), but if you want to then you can do it any way that works for you. The FAA just wants you to log something that shows you did receive the necessary ground training.


What is this "flap-like" thing on the back of the F-15?

It is a speed brake (air brake). Here is a closeup of it.

Image from aero-cafe.com

It is usually used reducing speed landing (approach). It is also used for other functions- to slow down quickly at high speeds and to prevent too much speed buildup in a dive.

This image shows it being used during approach.

"F-15A 21st TFW landing with extended speed brake 1984" by SSgt. K. Vail, USAF - U.S. DefenseImagery photo VIRIN: DF-ST-85-11671. Licensed under Public Domain via Wikimedia Commons.

Similar airbrakes are also found in other aircraft, notably the Su 27 and its derivatives.

Image from aerospaceweb.org


What lifting gas was used for barrage balloons during the world wars?

According to a BBC article here, hydrogen was used, not helium.


When modeling a shear flow for dynamic soaring, is the coefficient always a constant?

The shear layer is conventionally described as a "thin" transition above stationary air and below constant ambient wind.  Within that layer,

The wind's gradient w.r.t the altitude between the shear boundaries can be modeled by any smooth (say, twice differentiable) monotonic function.

-- Section III, "Novel Approach to Dynamic Soaring Modeling and Simulation," Kai et al, J. Guidance, Control, and Dynamics 42(6), 2019, https://doi.org/10.2514/1.G003866.
This paper mentions nothing about wind velocity changing w.r.t. horizontal location.  In fact it says

the wind blows horizontally by assumption

Because of incompressibility, and because the flow field is uniform both above and below the shear layer, any horizontal change within the shear layer would induce a vertical component of the wind vector.  (Handwaving argument: imagine a brick wall downwind in the layer.  That would force a downdraft along the wall.)
So today's models of wind shear ignore second-order effects like horizontal decay of magnitude of shear, perhaps because that suffices for the still interesting case of an albatros mid-ocean, as opposed to the turbulence immediately downwind of a mountain ridge.  But this won't be the case forever, of course.


Why is braking action (with Anti-Skid) best when the wheel rotates at ~85% of the actual speed?

Tire-road dynamics at speed are described by the Pacejka's "Magic Formula", so called because

  there is no particular physical basis for the structure of the equations chosen, but they fit a wide variety of tire constructions and operating conditions.

This empirical description was developed using regression analysis and consequently has no theoretical basis as to why it works, but it does work and is widely used. You may not like the answer that 85% is best because that is what the formula says.

The reference gives the parameters necessary for calculating the peak longitudinal force and corresponding slip. ABS systems attempt to balance a peak slip ratio with vehicle directional control, resulting in an ideal ratio between 0.1 to 0.3. (which is 70-90% of ground speed using your terminology)

source

I would modify your statement #2 to say that in order for the ABS to know when the tire begins to slip it has to know when the tire does not slip, which allows the determination of unbraked tire speed from which the desired slip can be calculated. I think this is one reason for pulsating brakes when ABS is active; the ongoing determination of zero slip speed as the vehicle decelerates.


Again, where is the pivot point in pitch

Disclaimer:  I am no expert and if you get a better answer from one of the other contributors here, you should listen to them, not me.

From what I can tell, it looks like you're asking whether you can define a point that includes all downward forces on the airplane, including center of gravity and tail downforce.  As I understand it, yes you can, and this point is center of gravity, which includes all the associated downward forces.

The airplane then would pitch about the center of gravity, as it usually does.


What is the purpose of an inboard aileron?

As far as I know, the inboard ailerons are used for high speed maneuvering.
The rolling moment induced by the ailerons is linearly dependent with the distance to the center of gravity (e.g. the farther out, the stronger the moment, the harder the roll).
As the aileron is an aerodynamic surface, the force induces is equal to:
$$F_{aileron} = c_l(\alpha) \frac{1}{2} \rho V^2 S_{aileron} $$.
The moment induced is equal to this force, multiplied by the distance to the c.o.g.:
$$M_{aileron} = y_{aileron} \cdot c_l(\alpha) \frac{1}{2} \rho V^2 S_{aileron} $$
If you're flying in cruise , and you want to make a smooth turn, you need a relatively small $M_{aileron}$.

However, the $V^2$ term, is already very large. So we want to make the rest of the terms relatively small.

We could do this with outboard ailerons: Use the outboard aileron with a large $y_{aileron}$, combined with a small $c_l(\alpha)$, usually the outboard $S_{aileron}$ is fixed by the low speed control requirements.
However, you can provide $M_{aileron}$ more accurate if you use the inboard ailerons (with a small $y _{aileron}$). The smaller distance makes the moment a bit smaller, and less susceptible to small deviations.

I think the Airbus A330 & A340 use their spoilers to maneuver at high speeds. They simply extend their spoilers -which are usually also reasonably close to the c.o.g.- a tiny bit, this changes the lift distribution, also causing a rolling moment. I did not research this fact, so I'm not 100% sure this is the reason the A330 and A340 do not have inboard ailerons, but I do know some aircraft use this method for high speed maneuvering.


Why would a flight from Frankfurt to Madrid fly over London?

I can't be completely sure but the most likely reason is a planned strike by ATC in south-east France. It was planned from the 30th of June to the 1st or 2nd (depending on the source) of July, meaning that ATC services would be unavailable or at least seriously reduced in that area, presumably with knock-on effects in other parts of the country. Some airlines had cancelled flights completely although in the end it looks like the strike was called off.

Strikes are notoriously common in France (there's even a website dedicated to tracking them all) and especially in the summer, so an airline might just plan to avoid French airspace altogether to avoid the uncertainty. Of course that costs more money, as you said, but a missed connection to Chile and stranded passengers in Madrid would also cost money.


What are the effects of rotating airfoil sections to match wing's dihedral?

All you do by not tilting the airfoil (around its longitudinal axis) is to reduce the relative thickness of the wing. Since that effect is proportional to the cosine of the dihedral angle, the effect is negligible for realistic values of dihedral.

Lift will most certainly not be affected, because it, being at its root a pressure, always acts perpendicular to the local surface.


Can I work on aircraft without an A&P license?

Anyone can work on a plane.  Only an A&P can certify the work and return the airplane to service, with a few exceptions.  A plane cannot (legally) fly unless the work has been signed off by an A&P, with a few exceptions found in pt43 Appendix A Para C (preventive maintenance).  Even if the work is allowed by pt43 App A Para C, the person performing the maintenance must be at least a private pilot, the airplane must belong to (or be operated by) that pilot, and the airplane cannot be in commercial service.

"Supervision" is loosely defined and is up to the A&P to decide in the field.  The idea is that the supervising mechanic should be observing while you work but the language allows the mechanic to determine exactly what must be observed while work is being performed.  Some will want to be over your shoulder the whole time, some will trust your word, but most are somewhere in the middle (trust but verify).

You may work in a shop as an apprentice and do all of the work you describe but you will be subject to the directions of your supervising mechanic.  Your time as an apprentice counts toward A&P certification, too.  They will likely start you at very low pay and assign menial tasks until you prove yourself to be reliable.  Sweep the floors with a smile and don't be offended that they don't throw cylinder replacements at you on day one.  You need to build up trust before shops will let you do any fun work on customers' airplanes that can easily exceed the price of most middle class homes.


Why does the Antonov AN-225 not have any winglets?

Winglets are less effective at producing added lift than an equal-length wingspan extension. They are used on airliners when simply enlarging the wing would put the plane into a larger size class, or outside the 80 m "box". A longer wingspan, which the An-225 has (10% over the limit), is better at producing lift.

The An-225 is a special purpose cargo aircraft for delivering very large loads such as the Buran space shuttle. It doesn't have to care for commercial airport traffic patterns meant for high-throughput operations - servicing thousands of planes separated into fixed size groups.

In its original role the An-225 would operate from airstrips purpose-built for it, and seeing little other traffic. Today, on the rare (or not so rare, but its most public deliveries are to remote destinations) occasion when it has a commercial airport in its itinerary, they can deal with the extra requirements of a somewhat larger plane.

Think of it like a wide load truck: they can go outside the 102"+3" limit at the expense of pre-planning the route. It's always a special delivery with these planes.


What switch was Skiles talking about shortly before the Hudson landing?

It's explained in the final report. Most definitely they asked him what he meant, as the transcript itself is:

  * * switch?

"*" denoting unintelligible words by the transcribers.

  The first officer was referring to the cabin emergency notification switch, which provides a signal to the cabin crew members indicating that an emergency has occurred.

To which Sully replied "yes", then the GPWS announced 30 or 50 (transcribers not sure), then the RETARD callout (for the thrust levers) was announced (computers eh). The recording ended about 5 seconds after asking about the switch.

(wikimedia.org)

Putting the switch to ON does three things:

lights the overhead emergency lights (more here on this cabin indicating system)
lights the exit signs
lights the exit markings on the cabin floor (proximity marking system).

Regarding the HOT and CAM, see: What is the meaning of HOT-1, HOT-2, CAM, etc., in cockpit voice recorder transcripts?

  CAM Cockpit area microphone voice or sound source
  HOT Hot microphone voice or sound source
  -2 Voice identified as the First Officer

The audio source indicated is usually the clearest one.


Will optimising the weight distribution of a commercial flight save fuel?

For precisely this reason the A310-300 had a fuel tank in the horizontal tail. However, the pilots I spoke with (Pan Am) did not understand the purpose and insisted that the tank is empty all the time. The A330 and A340 also have a tail fuel tank, and here its fuel level is automatically controlled.

A330 tank arrangement (picture source). Note the trim tank in the horizontal tail.

Shifting the c.g. a little back reduces drag slightly (less than 2% reduction in fuel consumption, depending on initial c.g. position) but also static stability. This is no problem when the FCS adds enough stability, but in case of a system failure you should make sure that the rear tank can be emptied soon. Hand flying an aircraft with relaxed static stability is tiring.

The A350 did away with this feature because it was felt that the added complexity would outweigh the benefits.


How does a large cargo plane like the C-130 Hercules take off and land in such a short distance?

Assault Takeoff/Landing Technique

This is a significant reason for the C-130's performance that you witnessed. "Assault" takeoff/landing speeds are lower than normal speeds, and closer to stall speed. Also there are some weight limitations. Further, the crew must be specifically trained.

Stopping Quickly

Any idea of a smooth landing is thrown out the window. The intent is to "plant" the wheels at about 300 feet down the runway. That is, transition immediately from approach attitude to actually landing rather than assuming a touch-down attitude and letting the aircraft float down to the runway.

The nose gear is pushed to the ground and the instant the wheels are on the ground the props are thrown into full reverse, now pushing air forward. At the same time the pilot puts all his might into mashing the brakes. He would "stand on the brakes" as we say. The yoke is also pushed full forward which puts as much weight as possible on the landing gear. The anti-lock brake system is critical here, preventing skidding out of control and blown tires.

In Vietnam, in combat conditions, 130 pilots would put the props in reverse before touching down. If you've seen the video on YouTube of a C-130 landing on an aircraft carrier, they did it there too.

J's Props are a Huge factor

The performance boost of the J models thanks to the new prop and engine is amazing vis-a-vis the older models. But fundamental airframe limitations are still there. Nonetheless more blades (6 vice. 4) and the "un-ducted fan" design simply pushes more air.

Show Off Configuration

An empty airplane with a light fuel load of course maximizes the short takeoff and landing performance.

C-130 Has Fowler Flaps

Not blown flaps. Just because the props push air over the wing does not make it blown flaps. Otherwise, yes, the C-130 was given lots of flapage precisely for this purpose.


What is the Efficiency of Cessna-150's Propeller?

Probably quite low... After a series of gliding experiments made with a Luscombe 8E, and published by the AIAA, the conclusion was that the prop efficiency was around 62%...

https://engineering.purdue.edu/~andrisan/Courses/AAE490A_S2010/Buffer/AIAA-46372-872.pdf


What are the flaps on the exhaust of military airplanes for?

Those flaps on exhaust are for thrust vectoring. A simple definition would be:

  the ability of an aircraft [...] to manipulate the direction of the
  thrust [...] to control the attitude [...] of the vehicle

F-22 uses it like this:

  [Its] nozzle [...] is the first vectoring nozzle. That means
  the pilot can move, or vector, the nozzle up and down by 20 degrees.

  The gases coming out of the vector nozzle help push the airplane's
  nose up or down. This vectoring increases the roll rate of the plane
  by 50 percent, making it much more maneuverable than other fighters.

  Thrust vectoring [...] works automatically in response to commands
  from the pilot.


What do these double Class Bravo airspace floor and ceiling limits mean?

The way SkyVector shows airspace is subtly different than shown on FAA charts. Whereas the FAA shows the combined limits in each area, SkyVector shows the limits once for each layer, even where layers overlap.
So, what you are probably seeing here is one area of FL145/35 on top of another area of 35/SFC, possibly disjoint but the labels for both areas just happened to end up near each other. Or, it may be two areas with the same boundaries but different owners or airspace classes. As a result, it’s often difficult to figure out exactly which area(s) each label applies to.
Note that while SkyVector uses official maps from the FAA in/near the US, the rest of the world is computer-generated and not nearly as useful, especially since other countries often use airspace classes in vastly different ways that can’t be represented well in SkyVector’s pseudo-FAA style. Notably, they use blue for all classes, which often confuses folks used to the FAA’s color scheme.
According to the Spanish AIP, they are indeed two stacked airspaces; TMA SEVILLA AREA 3B and TMA SEVILLA AREA 3C. For example, in 3B (the higher one):

VFR traffic is not allowed, except for State aircraft, helicopters, medical and rescue flights.

Official e-chart here: https://insignia.enaire.es/


Is the Falling Leaf maneuver used for UAV recovery?

The maneuver as described is not a particularly efficient way of losing altitude: You're alternately stalling & recovering from the stall.
More efficient descent procedures exist.

The technique of holding the aircraft in a wings-level stall (or putting it into a spin) was used in the early days of aviation to get back below a cloud deck if you were trapped "on top": when you broke out below the clouds you would recover from the maneuver & proceed to your destination / landing (if you were lucky enough to have sufficient altitude to recover when you came out of the bottom of the clouds).

Needless to say neither of these maneuvers makes much sense for an unmanned aircraft: If your goal is a rapid descent you will execute a maneuver that gives you the best possible descent rate (such as the emergency descent procedure in the POH, or the one in the Airplane Flying Handbook); If your goal is to get back below the clouds you've already busted the regs (you need to maintain visual line-of-sight with your UAS), but if and when the regulations change you should also be able to recover using more modern techniques (like descending on an instrument approach or using a synthetic vision system) to ensure you don't hit anything, like another aircraft.


Why does the A330 sit nose-down on the ground?

For one reason or another, the main gear was made longer that originally planned and it was decided to avoid the cost and weight also extending the nose gear to match. The nose down angle while rolling along the ground is no big deal one way or the other, except for looking bad and disconcerting passengers who wonder why the plane is tilted forward.

Lots of airplanes are like that, sometimes because of changes made during development, but more typically after fuselage stretches where the main gear had to be made longer to keep the extended tail off the ground during rotation (the flying pencil CRJ1000, which I used to be type rated on, feels like a backwards taildragger in that regard).  Obviously, the freighter needs a level cabin floor for loading, hence the nose gear band-aid; for the passenger versions, it's not really necessary and the blister and extra structure to do all that is just ballast and drag, serving no useful purpose.


How do insurers apportion responsibility when airliners collide on runways or taxiways?

Insurance is a contract between the airline and the insurance company. Typically, the airline is simply compensated an amount by the insurance company and the case is closed.

Demand to another party for settling damages only occur if the damages is unusually large and one party is mostly at fault. You have to consider the time and cost taken into legal proceedings as well.

Insurance compensation actually occur more frequently than you think. For example, at my airline, someone either forgot to apply the brakes on the food trolley or the brakes failed. Either way the trolley smashed into something during ground operations, resulting in damage to the trolley itself (I heard it was destroyed). Insurance paid us.

Regarding the specific incident about airplane collisions on taxiways, it is highly unusual. My guess would be it was handled as a "special case" in this instance.

You are correct that any investigations, if any, focus on preventing future occurrences rather than assigning blame. Settling damages is a civil matter; as such insurance companies rarely launch their own "investigations". Even if they do, it would just be a corporate and expensive version of two drivers using dash cams to argue who has to pay for the stretched bumper.

At any rate, insurance may compensate the airline even if employees of the airline are at fault. That is what insurance is for.


What does the callout "300... MINIMUMS" mean?

Your friend is right. The "minimums" call is done at the level over the ground at which you must have a visual reference to the runway environment in order to continue your approach. If you do not have a visual reference at minimums (due to bad weather), you have to perform a missed approach.


Why does the stall angle decrease as camber increases?

At the same angle of attack, a cambered airfoil has a larger suction peak on the upper side (toward the leading edge), and a larger associated pressure recovery (toward the trailing edge).

Larger pressure recovery is equivalent to larger adverse pressure gradient, which leads to easier onset of boundary layer separation and stall.


Why do some airplanes have simultaneously a straight wing and a swept horizontal stabilizer?

The tail sweep helps to extend its range of angles of attack.

For both stability and control, it is very important that the tail doesn't stall before the wing in any circumstances (for a classic design; for canards it may be beneficial). Generally, for high positive angles of attack, the horizontal tail already has an edge because it is set at a lower angle of incidence for statically stable airplanes. Plus, the change of downwash with AoA helps.

Still, to delay stall further, particularly when control surfaces deflection is considered, a higher sweep angle can be used. The lift slope vs AoA decreases with the [cosine of] sweep angle, and the stall angle increases. Note that the maximum lift coefficient also decreases, so the tail may need to be sized larger.

You might notice that even for the airplanes with swept wings, the sweep angle of the tail is nearly always higher (typically by 5°), primarily for this reason.

The leverage advantage (mentioned by John K), may be important in practice only for naturally short-tail airplanes, typically with rear-mounted engines. A classic solution is to put the horizontal tail on top of a swept vertical tail. But in other circumstances the additional lever arm of a higher sweep will likely be offset by the lower effect per AoA and thus larger size (as mentioned above), and heavier design due to additional torsional loads.

And let's not forget looks! It's fashionable to have at least the vertical tail sweep. Compare different versions of C175, for example.


Can a supersonic aircraft have winglets?

This has been (and thus can be) done and there is some current research on it as well. The XB-70 Valkyrie had dropping wing tips that added stability at high Mach speeds as well as allowed the plane to ride on its own shock wave. It also effected trim drag,

  The repositioned wingtips also reduced the area behind the airplane's
  center of gravity, which reduced trim drag. The downturned outer
  panels also provided more vertical surface to improve directional
  stability at high Mach numbers.

You can check out this podcast episode that interviews some of the people at NASA doing various research projects including wingtip control systems and other interesting applications in that space.

You may find some info in this book on supersonic wing theory.

This thread (and you know how accurate the internet is) has some interesting points on the matter.


What's that "frame" in the windshield of some piper aircraft for?

As Thunderstrike suggested, these are windscreen heaters commonly marketed as "hot-plates".

The Piper Aztec I flew had one of these. When I first started flying the aircraft I expected some difficulty in seeing through or around it, as it was directly in my view. However, when actually flying the aircraft, I hardly noticed it was there.

As with all the electric windshield heat that I am familiar with, it is intended to be used as an anti-icing measure, not a de-icing measure. This means that the plate is heated so that frozen water that strikes the plate should melt and flow off, and liquid water should not freeze but should flow off. The heat is provided by fine, high resistance wires running vertically between two plates of laminated glass. The wires are visible if one focuses on them, but as with looking through a window screen, the wires disappear when one focuses on the distance.

See the following close up of a heated windshield employing the same type of heating elements:

Source: own work

These hot plates are available for multiple makes and models of aircraft, both as a replacement heater for aircraft with inoperative windshield heat such as the Piper Navajo, and for aircraft without installed windshield heat such as the Piper Aztec.

For this classification of aircraft, in order to meet flight into known icing conditions (FIKI), windshield heat is needed to provide an adequate view for taxi, takeoff, approach, landing, and certain maneuvers. Having an adequate view is helpful at any stage of a flight. However, for the practical purpose of anti-icing, windshield heat is arguably most important—and required—during the landing phase. See 14 CFR 23.775(f):

  (f) Unless operation in known or forecast icing conditions is prohibited by operating limitations, a means must be provided to prevent or to clear accumulations of ice from the windshield so that the pilot has adequate view for taxi, takeoff, approach, landing, and to perform any maneuvers within the operating limitations of the airplane.


What's the Canadian equivalent of a Biennial Flight Review?

There is a requirement to complete a flight review every two years. I guess it's technically just a 'FR' but for all intents and purposes it is a BFR!