I'm a USPA AFF, tandem, and static line instructor.  Your signed and completed A-License Proficiency Card is valid and USPA will process it without the stamp.  You only need the stamp if you want to go to another dropzone and use your card as a temporary license.

The proficiency card is only valid for 60 days after the date it was completed, so don't waste time sending it in.  The last I heard, USPA is taking 3-4 weeks to process license applications.

Edit to add:  Don't send in the actual card.  You can mail a photocopy, fax it in, or scan it and email it to membership@uspa.org.  Faxing or emailing will get you your official license a few days faster.


In which phases of flight should the carb heat be turned on?

Carburettor icing is rare at high RPMs, as there will not be much of a venturi effect. To have carburettor icing in such a scenario, it would have to be very cold and very humid/wet, in which case you would probably also encounter airframe icing, and might want to reconsider your flight.

Applying carby heat has two downsides:

The air will be unfiltered, meaning dirt or other contaminants can be sucked into the engine;
More importantly, the warm air means you won't be able to reach your usual maximum RPM.

These are two undesirable traits for takeoff.

The POH in a Cessna 172 I fly says to have carburettor heat off for takeoff and landing, but only really says it should be on when you suspect icing. I was taught to be much more conservative - prevention is better than cure. I apply carby heat whenever the RPM is below the 'green range', unless it is especially hot and dry outside. However, I remove it when I'm about 30 seconds from landing, in case I need that extra power for a go-around. You also shouldn't apply it 'half way'. Either it's all in or all out.

Boldmethod has a good article on why it's important, and you should pay attention to the conditions where it is most likely to occur.


Why does the MD-87 have strakes on its engines?

They are indeed strakes which serve to reduce flow separation on the lower rear engine fairing by creating a vortex which will mix the outer, faster flow with the slowed down boundary layer on the lower rear part of the fairing. You will notice that the nacelle is mounted at an angle of 3 degrees to the fuselage: This is to position the intake and nacelle in line with local airflow, which is pointing slightly downwards at the rear fuselage due to the wing's downwash. The exhaust is again pointing directly back, so the thrust will be aligned with the lengthwise axis of the fuselage and will not produce pitch moment variations when thrust is changed. In combination with the nacelle incidence this produces a more pronounced curvature on the lower side of the nacelle, which in turn is more prone to flow separation.

You could as well place a row of vortex generators on the bottom of the fairing, but the strake will produce less drag when downwash is low and its service is not needed. With higher downwash, the strake will produce a stronger vortex, just when it is needed most.


What are the disadvantages for using short-field take-off technique?

Three main things:

There is a little bit of increased brake wear because you apply them to stop, they usually creep a bit at full power, and when releasing them, there is also that short period where they are slipping while under pressure.  More wear than not using them at all anyway.  Of the three this is pretty trivial however.
Sitting stationary at full throttle has the engine at maximum heating rate and minimum cooling flow.  The area of the exhaust valve on the head heats up very quickly.  During maintenance, full power engine runs except for very short bursts are to be avoided without a special cooling box shroud, to catch large amounts of air and force it down between the cylinders, installed in place of the cowling.
The full power condition while sitting stationary turns the prop into a pretty powerful vacuum cleaner and it will suck up just about every pebble and bit of grit on the pavement (and even clean looking pavement is full of that sort of FOD).  Or water if you are over a puddle (and water erodes aluminum).  It will leave you wondering why you have to constantly have your propeller dressed out to clean up all the little stone nicks (this is why I always do run-ups over a patch of grass whenever possible).  Of the three, this is probably the biggest item in my experience.


Why did the US Airways Flight 1549 passengers stay on the wings?

Because they were told to evacuate there, if you take a look at the official audio transcript from the accident:

  place both arms through the straps and hug it to your chest. flight
  attendants are pointing out there are a total of eight exits on this
  aircraft, two door exits in front of the aircraft, four window exits
  over the wings, and two door exits in the rear of the aircraft. once
  again, two door exits at the front of the aircraft, four window exits
  over the wings, and two door exits in the rear of the aircraft. each
  door is equipped with an evacuation slide if directed to exit... the
  aircraft jump onto the slide and move away from the aircraft.

The rear exits were largely blocked by water making the forward exits the only ones with slides, those slides were utilized as evidenced by photos included in the report:

(source)

With only half of the slides available the wings also had to be used. The wing slides are intended only for ground landings and do not double as rafts, as per the accident report

  According to TSO C-69c, Type IV is a combination inflatable exit ramp
  and wing-to-ground slide. The off-wing ramp/slides were intended to be
  used in the event of a ground, not a water, evacuation.

As such the over wing slides could not be used in this case.


what are the advantages and disadvantages of tilt rotor vs ducted jet engine for a VTOL aircraft?

Well, engines and rotors obey the same laws regarding induced drag (induced power in this case) as wings: larger fan/propeller/rotor is more efficient, but limited to lower speeds. And from that, the advantages should be obvious:

Tiltrotors (V-22, AW609) are only a little less efficient in hover than normal helicopters, but they can only go around 300 knots (both aircraft have max speed quoted at 275 knots); above that, the tips would become supersonic and generate too much drag.
These can be built with engines similar to what a comparable fixed-wing turboprop aircraft would need and can cary comparable payloads with only slightly higher fuel burn. The AW609 is a product for civilian market aiming at charter operators supplying oil platforms and similar remote stations where it should be more efficient than helicopter.
The main disadvantage is that they are more complex and therefore more expensive to build and maintain.

Tiltjets/vectored thrust jets (VJ-101, Harrier, Yak-38, F-35B) are horribly inefficient in hover, but they can go fast.
Jet engine for thrust/weight ratio 1 (needed for hover) takes up most of the aircraft, leaving very little room for payload. Such design and thrust/weight ratio is common in fighters, but out of question for anything else.
This configuration also consumes a lot of fuel for take-off and landing. Absolutely no way would anything like that be competitive for commercial operation. However, the military is willing to pay it if they can have a fighter jet that can be deployed from an assault ship. And even they prefer conventional aircraft when possible.
This is really niche design, but one that offers enough tactical advantage that the Marines and the Royal Navy want it (US Navy will use the conventional F-35C with CATOBAR, Royal Navy decided it will be cheaper to use the STOVL F-35B version than upgrading the carrier they are building to CATOBAR).

I can't really compare maintenance. Obviously both are more complex than conventional aircraft and even than helicopters. But also, anything military is usually much more maintenance intensive than civilian designs, because military usually wants to squeeze out every bit of performance at the cost of simplicity.


It seems to be an access door for the pilots, judging from this photo. Not a super easy entrance, the door in the back is a bit lower down.


How can I ensure that I have a mode C transponder?

For any aircraft you should check the accompanying POH for a full equipment list of what the plane has been outfitted with. Likewise you should be alert for any place cards noting defective or inoperative equipment. You should also check the aircrafts logs to make sure the transponder has been properly inspected according to § 91.413 ATC transponder tests and inspections and that it is operable. Just because you have one does not mean its legal to fly with. A transponder capable of Mode-C (altitude encoding) needs to either be connected to an altitude encoding altimeter or a blind encoder to report altitude. You should be able to find this out in the POH, if its not connected to one of these two units it will behave like a Mode-A transponder. You can find a  discussion on the various setups here. If you are really curious about how Mode-A/Mode-C communication works this is a pretty good read.

Specific to the Garmin unit you have pictured you can get it to display the aircrafts altitude by pressing the "func" button (pressure altitude that is) and compare with your altimeter. If the unit has a readout it then an pressure unit can be assumed to be connected. NOTE: This is not an official test by any means.


Is it true that as of 2014, flight reviews are waived for current flight instructors under FAA rules?

It is false.

14 CFR §61.56(f) states:

  A person who holds a flight instructor certificate and who has, within
  the period specified in paragraph (c) of this section, satisfactorily
  completed a renewal of a flight instructor certificate under the
  provisions in §61.197 need not accomplish the one hour of ground
  training specified in paragraph (a) of this section.

Also, AOPA has some great input on this topic:

"Pilot's Guide to the Flight Review"

Bottomline: You are correct, your friend is not.

Maybe there was a misunderstanding in the conversation whereby they were specifically talking about their own certificate (and any ratings they may be seeking that may take place of the flight review) as opposed to a general term?


What's the difference between a TSO Authorization and a letter of TSO design approval?

I don't know much about this, but it looks like a TSO Authorization is for domestic (US) manufacturers, and a letter of TSO design approval is for foreign manufacturers who want to import their products into the US. See 21.621:

  §21.621   Issue of letters of TSO design approval: Import articles.

  (a) The FAA may issue a letter of TSO design approval for an article—

  (1) Designed and manufactured in a foreign country or jurisdiction
  subject to the export provisions of an agreement with the United
  States for the acceptance of these articles for import; and

  (2) For import into the United States if— [...]

And the FAA's page on it says:

  What is a letter of design approval?
  An FAA design approval for an article manufactured outside the United States that meets a
  specific TSO.

I have no idea about other aviation authorities, but I assume there are similar regulations in other countries because the same general issue exists everywhere: how do you ensure that both manufactured and imported aviation components meet all required standards?


Can Flight Simulators (FSX P3D) give you the expecience you need to fly a RW plane?

GdD brings up some good points but that really depends on what you mean by "home simulator" and it depends on the airplane. There are some people that have taken it to the extreme and built simulators that are fairly close to real and provide a solid learning platform not only for the flying but the actual physical operation of the controls. You can fairly easily build a home sim for a small plane that has all the controls and instruments you would see in a real plane and even in emergency situations you will see real warning lights in your sim and be able to mitigate it as you would in a real plane (nothing is stopping you from wiring in a smoke machine either).

As for the flight dynamics they get more real as time goes on and computers get better and better. I use X-Plane and simulate the Piper Archer I fly in real life which I find to be pretty close to the real thing from a flight dynamics/response stand point. My simulator did a great deal for my cross wind proficiency when I was training. I cant say I learned to fly in the sim but I did a great deal of honing of my skills in my home sim.

  The sim is a tool not a replacement

If you understand this you will better be able to realize that the sim can provide you a great deal of proficiency and can suffice for training in some (not all) cases. Even the big guys use simulation to train for the real thing (this article provides some nice pros and cons). The FAA even considers approved simulator time to count towards certain things.

Unless you have a full motion sim at home, the sim wont provide you with the feeling of flying which is very hard to replicate. It wont disorient you in IMC by having G-Forces cause your vestibular sense to distrust the instruments. It wont physically throw you around on a bad cross wind landing with wind sheer causing your knee to bump the yoke. It wont shake you to the point you drop your iPad while briefing an approach plate. It wont spin you until your lunch decides it wants to be elsewhere. These are the kinds of experiences you may only find in a real plane...

One last thing to consider as well is some what of the reverse case. Aircraft cockpits are actually getting closer to computer based units as time moves on. Its common to see keyboards in airbus cockpits and many of the former steam gauges have been all but replaced with screens. As we move into a more automated era some switches have even been lost to digital control units. Even the flight controls them selves have moved into the modern age with fly-by-wire systems removing physical linkage from the side stick to the control surfaces.


Do military jets' radar jammers block their own radar? And, if not, why not?

If you are emitting RF, you can be seen.  There are two ways to emit RF: 1. Transmit (or leak) a RF signal, and 2. Reflect a RF signal.

A jamming device emits (usually) high amounts of RF, with the general idea that the receiver of someone's radar unit will be desensed or otherwise overwhelmed by the signal.  Like putting a multicolored sun into a small dark room.

So with multiple receivers (as in multi-static radar) a jamming aircraft can normally be rather precisely located (assuming omnidirectional uniformity of the jamming signal).

When noise jamming, your aircraft may not broadcast on, near or on harmonics of a given frequency within a temporal frame of when you are emitting on that frequency, so your receiver has the opportunity to detect returns. More importantly, your noise emitter may drop power and your radar receiver may have cans (well, cavities) tuned to protect the sensitivity of your radar receiver when expecting a return signal.

There are many books on radar technology, but I believe EW102 covers radar, deceptions, noise jammers and other techniques in a manner that most mildly technical people can read and understand.  There are other books, but I use that series in an Electronic Warfare course I teach, and they are reasonably current. The open literature is rich with advances in jamming and other stealth methodologies that have advanced tremendously in the last 50 years.


Does a dual-rotor helicoptor like the Chinook transition from hover to forward flight differently than a single rotor helicopter?

The cyclic (dubbed control stick for the CH-47) takes care of that, not separate collectives (there's only one collective for both rotors per seat).

For forward flight, the pilot moves the control stick forward; the thrust of the aft rotary wing is increased while the thrust of the forward rotary wing is decreased, causing the helicopter to move forward. Since there is a large range of longitudinal control, high forward speed and extremes in center-of-gravity travel are inherent.

Source: CH-47 familiarization manual (see pages 55-56; PDF; 40 MB)


What's the technique for landing without one set of wheels?

The techniques vary slightly aircraft to aircraft, and also based on what landing configuration you have.  However, the general gist is to hold off the malfunctioning side from the runway for as long as possible, slowing the aircraft in the process, until forced to put it down on the deck.  This minimizes the contact between the wings and/or fuselage with the ground.

The single greatest danger with these types of landings is the risk of fire. The friction between the runway surface and the aircraft is tremendous generating an enormous amount of heat.  This is particularly problematic when you consider that the fuel is stored in the wings.

Fuel may be pumped to the opposite wing to counter-balance weight and move the fuel away to the fuselage with the highest possibility to have contact with the ground. This technique will shift weight away from the missing wheels and consequently reduce the possibility of fire.


What is the tailhook on naval aircraft made out of?

They're made of alloy steels that have ultra-high strength, high fracture toughness, excellent fatigue resistance, and high resistance to stress corrosion cracking.

Based on one of the manufacturers—QuesTek—the steel's grade is AMS 6516.

The 6xxx grade is a chromium-vanadium steel:

  Chromium-vanadium steel refers to steel alloys incorporating carbon, manganese, phosphorus, sulfur, silicon, chromium, and vanadium. Some forms can be used as high-speed steel. Chromium and vanadium both make the steel more hardenable. Chromium also helps resist abrasion, oxidation, and corrosion. Chromium and carbon can both improve elasticity.

Elasticity is important because you wouldn't want a deformable tailhook.

Other applications for it are:

  Landing gear, rotorshafts, driveshafts, arresting tailhooks and hookshanks, actuators, armor, munitions, gun barrels, and blast-resistant or impact containment devices.


Why are yaw rate and pitch rate obtained by these equations?

Turn rate is referenced to earth axes, yaw rate to aircraft axes, hence the $cos\Phi$:

If you turn at $\Phi$ = 0, your rate of turn is the yaw rate and the pitch rate is zero.
If you turn at $\Phi$ = 90°, your yaw rate is zero and your pitch rate = rate of turn.

In order to maintain a steady turn and not lose altitude the pilot does need to pull on the stick when turning..


Does a long time to solo hurt your chances of becoming an airline pilot?

It depends on the final product presented to the airline.  If an airline had two candidates, one of whom soloed in 10 hours and did well in a Sim Eval but was self absorbed, didn't like to follow procedures if he/she knew better, and didn't work well with people, and a candidate who took 30 hours to solo but was a team player, can get along with anyone, was an eager learner and was emotionally mature, and did a passable job in the Sim Eval, they'd take the "slow learner" in a heartbeat if they were confident the candidate could get through the type course.

In the airline world, raw flying skills are an important baseline, but big picture personality related issues are just as important and personality problems with crews are a bigger long term problem than how long it took someone to catch on at the start.


Is there a common route that Seattle GA pilots use to circle Mt Rainier while avoiding class B airspace?

I fly out of BFI and RNT.  The short answer is go East to clear the B, then South to parallel terrain as you climb.  You will have more time to do this if there is a North flow.
There’s no specific route per se, just climb as best you can while keeping between the two.
The Lake Youngs departure gets you going in the right direction, and once just past Enumclaw you can make a circling climb to get comfortably above the ridges.


Can a CFI give required instruction and endorsements on a 3rd class medical?

A CFI with a third class medical can provide any kind of instruction that they are qualified for (and be compensated for it), per 14 CFR 61.23(a)(3)(iv) and (v). The FAA's position in these scenarios is that you're being compensated for the transference of knowledge, not the operation of the aircraft.

For completeness, A CFI can provide instruction WITHOUT a medical if they are not flying PIC or acting as a required crew member. In this scenario training can be provided for certain additional ratings (e.g. commercial) or flight reviews AS LONG AS the student can PIC during that flight AND the CFI is NOT a required crew member (i.e. safety pilot for insturment training).  Additionally, the FAA has made a legal interpretation that a CFI can provide instruction to a pilot that is not current to carry passengers, as long as all other requirements for the student to be PIC can be met.

The specific regulations that allows this are 14 CFR 61.3(c)(2)(viii) and 14 CFR 61.23(b)(5)


What are the biggest challenges for GA airports?

One set of challenges that comes to mind are the types of things you find at an airport that is on that cusp between having an operating control tower and not.  I fly out of KJYO, Leesburg, VA and it very much fits into that catagory.  It frankly just gets too busy sometimes to support operations managed only by pilots coordinating on CTAF.  Examples of this include:

Wind conditions causing a conflict over whether Runway 35 or 17 should be in use.
Pilots doing straight in instrument approaches, while VFR pilots do pattern practice.
Conflicting planes on the single taxiway.

Indeed, I think the FAA understands this, since they are using it as the first US test site for a remote control tower.  The several times I've flown when this was in operation where a breath of fresh air!


What weather should we expect when temperature and dew point are similar?

Both 20/20 and 4/4 will probably result in fog or thick haze/mist.
4/4 is a problem because it tells you that besides the airport being likely fogged in, the freezing level is only a couple thousand feet above the airport and there is very likely icing at that level if there is any cloud up there. Only airplanes capable of flight in icing would be coming and going, if at all, depending on the actual runway visibility.
20/20 is also likely fogged in, but the freezing level is up at 10000 ft so that's not a problem.  15-20C is a sweet spot for carb icing, so saturated air at that temperature is a major concern.
The other thing to take into consideration is temperature tendency.  Generally, a zero spread like that in the morning means you can expect to wait a couple hours and the fog will lift.   On the other hand, a spread approaching zero in late afternoon is a big red flag.
When I was bush flying on floats in Northern Ontario, the dew point spread was the most important bit of data when checking weather.  A spread of one degree in the morning when departing on a trip was no worries because it would only improve (absent frontal conditions etc) as the day warmed up. On the other hand, a tight spread in the afternoon might mean making a customer wait at the lodge until the next morning rather than risk getting caught out scud running home at 500 ft, with clouds forming all around as the spread became zero, necessitating a diversion to the nearest lake on the route.


Do vortex generators increase Re of a wing?

Reynolds number depends on the free-stream speed, the chord length, fluid density and viscosity. So vortex generator does not modify the Reynolds number. However, it trips the flow aft of the device into turbulent flow. Turbulent flow, in fact, has higher drag than a laminar flow (at the same Re). Therefore, on top of the additional skin friction drag introduced by the VGs, the aerodynamic surface would also have higher drag.


Where does the final approach begin if the glide slope is intercepted at an altitude above that depicted on the approach chart?

The FAS begins when you've intercepted the GS, and are at or beyond (below) the charted GS intercept point (altitude).  So if your charted GS intercept is at BONGO at 3000' and you intercept the GS outside BONGO at 4000', your FAS begins at BONGO.  If ATC has you join the localizer at 2500' and you intercept the GS at 2500' inside of BONGO, then that point, where you intercepted the GS, is where the FAS starts on that approach that day for you.

There can be lots of ways to say that, some of which are less clear than others.  But that's the simple, and hopefully clear, answer.  And, maybe, going back to the FAA definition, you can see how what they put on paper matches this concept as stated here.


Airplanes in static display at Whiteman AFB

F-100, F-15, and F-4.  There is no F-22. The thing that looks like a brown nose cone on the F-100 appears to actually be the long, nose-mounted pitot boom, painted a light color, with its shadow visible just above it in the photo, all blurred together to give the impression of a much wider object.  It's clear from the shadow of the fuselage that the fuselage truncates abruptly in front, as per the air intake of an F-100.

All these three types were used by the US Air Force.

According to Wikipedia the F-100 on display at this base is a D model, number 55-3667.

Aerial Visuals has information about it, the neighboring aircraft, and other aircraft on display on the base.

This facebook page  describes these three aircraft being moved to their current location, with closer photos of the F-100.

This webpage of military aircraft on display in Missouri also has photos of these 3 aircraft before they were moved to Whiteman AFB (see the "St. Louis, Lambert Field" section), as well as other aircraft on display at Whiteman AFB.

These three types were all flown by the Missouri Air National Guard 131st Fighter Wing, now the 131st Bomb Wing- a unit currently based at Whiteman AFB.  Read more about it on this Wikipedia page.


What is the minimum speed at which the Antonov An-2 can maintain level flight?

"No stall speed" just means no stall break in the traditional sense.  The AN-2's slatted wing's maximum AOA is very high (typically about 10+ degrees higher than un-slatted, or mid-high 20s vs mid teens) and there isn't enough tail power to get the AOA high enough to get any kind of break.
Stall speed is normally published as the speed at which the wing is at maximum lift coefficient.  A typical wing makes a Clmax of about 1.5, slats raise that to about 2.5, and a slotted flap raises that again to about 3.5-ish. The AN-2 has full span slats and flap-flaperons so you can assume that just about all of its 770 sqf of wing area is producing a Clmax of mid 3s with slats out and flaps down.
You can use the handy calculator on this page (click on the "Stall Speed Calculator" link) to work out what the speed is at which this is achieved. For the AN-2 you could assume with 770 sqf of wing area, with, for argument's sake, a Clmax of 3.5 for the entire wing, and operating at, say, a relatively light 9000lbs, you get a "stall" speed of 32.8 kts (37 mph), the speed that the wing is making maximum lift based on those assumptions and technically, this is the answer to your question.
With a slatted wing, the lift curve has a more rounded top; this is, lift declines fairly gently after the peak, so you can continue raising AOA and all that happens is sink rate goes up, until the tail runs out of downforce authority.
With power, thanks to the slats, you get both more tail downforce with the slipstream blowing on it, and because you can reach very high deck angles, you start to get a significant boost from the vertical component of engine thrust itself when the thrust line is canted up at, say 25 degrees.  And on top of that you get added lift from the slipstream itself passing the wings..
If the engine is making, for argument's sake, 4000 lbs of thrust when at full power (you get roughly 4 lbs/hp) and the thrust line is canted up 25 degrees, there is a vertical thrust component of about 1700 lbs.  This has the effect of reducing your weight by 1700 lbs, and plugging in a 1700 lb weight reduction into the calculator gets you down to about 29 kts (or 33 mph).  Add in the additional lift from slipstream passing part of the wings dropping the minimum speed a few more mph, and you can see how you can get to the point of the plane being able to back up at 5 mph in a 35 mph headwind using power in the slow-flight regime, at a relatively light weight at least.
So, the AN-2, at a relatively light 9000 lbs, using the standard formula and using typical assumptions, should be able to fly at a minimum speed of 37 mph power off and about 30 mph or a little less power on without sinking, which agrees more or less with the article's statements.
Plus, there is enough tail power with power on to increase AOA a little more, getting speed down to 25 mph, but while it's under control, total lift will be declining and the airplane will be sinking while doing so.
None of this is particularly special.  The AN-2 achieves its performance with lots of wing area and full span slats and flaperons.  Other STOL aircraft with full span flaps and slats can do the same thing.


How does a VOR or a VORDME affect the coding decision between CF or IF-TF respectively?

First; you have to understand that ARINC 424 is an industry standard.  It is not regulatory.  The regulatory documents are published by RTCA (and EUROCAE in the EU).  The basic database coding requirements of it are generally well accepted and used by the industry as those are essential to its primary function of interoperability.  But there's a lot of flexibility in how strictly developers follow the standard.
The example you give is one of application of the standard.  Both of the leg combinations are valid, though the IF-TF is preferred.  Note that ARINC 424 uses the word 'should' and not 'shall'.
Having worked FMS, I can say that the VI-CF could be coded but there are potential issues if XYZ is not a VOR/DME.  How is FOOBR defined if there's no DME?  It would have to be defined as an intersection with a radial from another VOR and the XYZ radial or as a Lat/Lon fix.
If it's a Lat/Lon fix, you can't reliably use the CF leg to get to it even if it's nominally on the radial as the radial error is quite large and could result in 'missing the fix' while flying the radial.  And since the Lat/Lon fix is the RNP standard, the preferred leg type would be an IF-TF leg with the IF at XYZ.
If FOOBR is an intersection, it can be workable once you are established on the CF leg - by tracking the crossing radial.  But the VI leg intercept is a floating fix which complicates the path generation as the relative positions of the intercept and FOOBR are not easily computed.  That problem is much simplified if FOOBR is a Lat/Lon.
In my experience, I would expect the CF leg to be coded as a IF-TF.  That provides fixed start and end points and a much simplified intercept computation.  And it wouldn't be unusual for an FMS to convert the the original CF leg (based on the VOR/DME) into a TF leg.


In track while scan mode of radar operation what are the methods to predict next position of target?

Standard approach for radar tracking is as follows:

Prediction of next position using one Interacting Multiple Model per aircraft. The basic model is made from two Kalman Filters, one of which predicts constant velocity (in 3D), the other predicts a constant-rate turn (also in 3D). The model selects the prediction from the filter that performed better during the last few updates.
Data from the scan arrives. Positions of the blips are compared to the predicted positions and the Joint Probabilistic Data Association technique is used to associate each blip with one of the tracked aircraft. If there are unassigned blips, a new model is set up to track the newly discovered aircraft.
Each aircraft's model is updated with the associated blip's position. This includes updating each Kalman Filter as well as selecting which of the filters should be used for the next prediction (the one that predicted the current blip more accurately).


Why is training regarding the loss of RAIM given so much more emphasis than training regarding the loss of SBAS?

From a safety perspective RAIM is more critical than SBAS.
If you are flying using GPS, you always rely on RAIM to keep you safe, sometimes you need SBAS too.
Receiver Autonomous Integrity Monitor is a function within an aviation grade GPS receiver that monitors the integrity of the GPS system. Without RAIM, a malfunction in the GPS system can cause large position errors that go unnoticed. These position errors can lead to nuisances such as controlled flight into terrain that really ruin the day.
SBAS on the other hand is (merely) an augmentation to GPS. It improves the vertical accuracy by a few feet, improves the RAIM function so that it is quicker to detect position errors and can detect smaller position errors. But basically, GPS without SBAS is safely usable for the vast majority of applications.
So, if you loose SBAS, you may not be able to perform certain approaches or use certain routes, but RAIM is still there guarding the system integrity.
But if you loose RAIM, the GPS position shown may be correct, or it may be 5 miles off, or 10 miles, or more; it's anybody's guess. The GPS receiver simply has no way to determine whether the calculated position is correct if RAIM is not available.

Now to your questions:
1) Why is Garmin so indirect about the loss of SBAS in their annunciations?
I can't speak for Garmin as to why they emphasize RAIM more than SBAS in their annunciations.
In case of case of the SBAS loss, the annunciation focuses on the operational effect (Approach Downgrade). In case of the RAIM loss, the annunciation focuses on the cause / technical description (RAIM UNAVAIL and LOI).
My guess is that SBAS was added later to their product line as RAIM, and their interface design philosophy had changed from focusing on the technical cause to focusing on the operational effect. For system commonality reasons they did not update their pre-existing RAIM annunciations when adding SBAS.
2) Why do pilots not also perform SBAS predictions like they do for RAIM?
SBAS depends mainly on the availability of a healthy SBAS satellite. The SBAS satellites are predicted to be healthy, and they cover a fixed area of airspace (they are geostationary satellites). The availability status of SBAS in not dynamic; SBAS is predicted to be available.
RAIM depends mainly on the number of GPS satellites visible from the GPS receiver, and how the GPS satellites are distributed over the sky (from the GPS receiver's viewpoint). This is very dynamic, depends on the  total number of GPS satellites in orbit, their health status, their distribution in orbit, the position of the GPS receiver etc. etc. For RAIM to work, the GPS receiver needs at least GPS 5 satellites to be visible (a few degrees above the horizon) and they need to be nicely distributed over the sky. So for RAIM, the situation is very dynamic, but it is predictable. That is why RAIM prediction is done.
3) Why is the loss of RAIM given so much more emphasis in training than the loss of SBAS?
Because, if not properly handled, the loss of RAIM has a much higher probability of killing you than the loss of SBAS.


Is a 5 hour 3 session process normal for a plane checkout you're already trained in?

It is normal for flying clubs and flight schools to require a checkout before allowing a renter to solo, which may take several hours, regardless of their license level or previous experience. They often require additional training if you dont have a certain minimum time in type.

Your club might be slightly more paranoid than average, but that probably translates to cheaper club insurance and thus lower rental rates, which means you will probably save money if you stick around.

Also, it should be noted that 70-200 hours is the period with the highest accident rate, so some paranoia on their part is probably justified. Even if it's "just a 152."


Does it help to climb in case of a partial engine failure?

Agreeing with @Antzi, high engine speed when combined with some sort of small scale physical damage or corrosion is a typical failure mode for propeller engines. Combining that logic with the fact that propeller engines run more efficiently at lower elevations (higher air density) I would recommend against climbing. In fact, lowering your elevation and speed will greatly reduce the stress/strain you are putting on the engine and will likely give you a better chance of making it safely to the closest airfield.


Why are static ports external on a non pressurized aircraft?

Remember Bernoulli? Lift is created on the wings because the air pressure decreases as the air moves faster. Same thing around the fuselage, but to a much lower extent. The air flowing around the fuselage creates a low pressure area so air in the cabin moves from inside the cabin to outside causing a lower pressure inside the cabin. Opening the cabin air vents can cause the pressure to be higher inside the cabin than outside.

Many general aviation airplanes that are used for IFR flying have two external ports that are placed well back along the fuselage. The  ports are usually positioned in areas where the boundary layer of air tends to be very stable, which lessens the effect of the static ports being hampered by turbulent flow and the Bernoulli effect.

Barry Schiff has an interesting explanation of how the pitot-static system works and shows how the placement of the static ports affects the reading of the instruments.


Why are the 737's variable-speed generator drives so unreliable?

@Jpe61 is correct in his comment that it's likely an electronics issue, since indeed a VSCF is mechanically simpler.
VSCF is also used on the MD-90, with poor initial reliability[1] – MDC went back to IDGs for the MD-95 (717).[1] It's also used on the 777 (only for backup, also with poor initial reliability[2]), and on the F/A-18.[3]
Capacitors
The F/A-18 utilizes cycloconverters, while the aforementioned civilian applications utilize DC-links (possibly the voltage-source inverter type based on this patent by Sundstrand, the makers of the 737 unit).[3]

... when electrolytic capacitors are used, in the case of a voltage DC-link, there is potentially a reduced system lifetime (Wikipedia: AC-to-AC converter § DC link converters).

More here: Wikipedia: Electrolytic capacitor § Operational characteristics
Your link says "the failure rate was just over 1 every 2,000 hrs". The 2,000 hours match the lifetime graphs in the article linked above (shown below). This being the culprit is supported by a paper on aircraft power generation:

The VSCF systems, apart for some noteworthy exception previously mentioned [referring to the F/A-18 and F-117A], did not get the same level of diffusion of IDG systems. This can be safely attributed to the role played by the PEC [Power Electronics Converter] (either ac/dc or ac/ac), which processes all the generated power and represents a single point of failure. Therefore, the PEC needs to be designed for the full-power rating and with high reliability requirements.[4] [emphasis added]

High load and cooling
Once you lose a generator, say running at 0.35 load, the other needs to pick up the slack and run at 0.7 load. The CAA's imposed limitation despite the redundancy tells us they don't trust the VSCF at high loads.

Source: airliners.net

One feature on the MD-90 is the air scoop for cooling the VSCF components. The more electronics are used, the more intricate cooling is needed (you can't just dip them in engine oil).
Maintenance practices
There's an official Honeywell video on installing the MD-90's VSCF with hints at improper maintenance practices, which would be a headache for an airline since the system is very niche with different tolerances.
Summary
So whether it's a 737 or an MD-90, the issues seem to be:

Cooling
Capacitors
Maintenance practices

Note that the technology hasn't become obsolete, at least academically: a 2017 paper proposes a "novel DC-Link VSCF AC-DC-AC" for the Embraer 190/195, from which:

Problems existed with the older VSCF systems in the past; however, the switched power electronics and digital controllers have matured and can be now, in our opinion, safely integrated and replace existing constant-speed hydraulic transmissions powering CSCF AC generators.

1: Douglas Jetliners, Guy Norris and Mark Wagner, page 85
2: Boeing tackles 777 power problems, 18 August 1999, flightglobal.com
3: Control of Power Electronic Converters and Systems, Volume 2, page 341
4: Madonna, Vincenzo, Paolo Giangrande, and Michael Galea. "Electrical power generation in aircraft: Review, challenges, and opportunities." IEEE Transactions on Transportation Electrification 4.3 (2018): 646-659.


How is a conflict between aircraft with TCAS I and II resolved?

TCAS 1 will only give a Traffic Advisory (TA). The crew will lookout for the other aircraft and take evasive action if necessary. They also may contact ATC for instructions. They will follow ATC instructions unless they see that the instructions will bring them into the path of the other aircraft.

TCAS II will give a traffic advisory first, then a Resolution Advisory (RA). The crew has to follow the resolution advisory and inform ATC of their maneuvering (e.g. TCAS climb, Big Jet 123). They are trained not to follow ATC instructions that oppose the TCAS RA.

Note that TCAS II RA's are always in the vertical plane; TCAS II can not give instructions to turn.


What runway length and width is needed to land a G650 and take off?

75-foot wide runway, and since you'll need to takeoff after landing, the takeoff distance at maximum takeoff weight at sea level is 5,858 feet.

Sources:

G650 spec sheet
Rocky Mountain Metropolitan Airport Facility Requirements


Are tracked landing gear systems still in use and development?

For the first half century of manned flight, landing gears overwhelmingly had only a single, large wheel per leg. This was the cheapest and simplest way to ensure ground mobility, but ran into trouble when aircraft grew in size. When the XB-36 prototype started testing in 1946, only three airfields in the US were able to tolerate the 156 psi pressure of its single main wheels.

For operating from unprepared surfaces, tracked gears were the straightforward transfer from tank experience to landing gear design.

Tracked main gear on the XB-36 prototype (picture source)

However, another route which was tried at about the same time was to increase the number of wheels the aircraft rests upon. With hindsight, the multi-wheel way was the better solution and has prevailed. When used with large, low-pressure tires it does not exert significantly more ground pressure than a tracked gear.

Some early and rather extreme examples for the multi-wheel route include the Arado 232 four-engine tactical transport aircraft. Only 20 were produced, however.

Arado 232 from up close. No prize for guessing why it had the nickname "Tausendfüssler" (millipede) (picture source).

When it comes to designing large aircraft for soft field operations, the Ukrainian design bureau Antonov has unsurpassed experience. This comes to bear in the landing gear of the Antonov 124, shown below (source). When you have 24 wheels to spread the load out, even 400 tons might not be too heavy, especially when the tire pressure can be adjusted from the cockpit.

An-124 in a botched landing. No worry, the gear will tolerate this kind of abuse, too.

Therefore, the research on tracked gears has come to an end shortly after it begun, and even the B-36 ended its days on a four-wheel bogie. Today, every large airplane has at least two wheels per leg for redundancy and sometimes a lot more.


What's the reason for the local flap extensions at the shockbody locations?

The anti-shock bodies also serve as fairings for the flap actuators. When the flaps are extended, the anti-shock bodies move down as the flap mechanisms extend. The upper surfaces of the anti-shock bodies are open to allow room for these mechanisms to extend.

The extensions to the flaps are to cover the openings of the anti-shock bodies when the flaps are retracted to provide a more aerodynamic surface. Evidently the outer locations have larger openings to cover.

Below is an image of a different aircraft and flap track design, but the principle is the same. You can see some of the hardware that sits in the fairings, and the covers that allow the hardware to extend out of the fairings.

Source

When the flaps are retracted, you can see that the flaps close out the top of the anti-shock bodies, and the outer position is closed out further aft.

Source


Does the AC-130 have de-ice or anti-ice protection for wings and surfaces?

The C-130 uses pressurized bleed air for leading-edge and window anti-ice. The props are deiced with electric heaters in the prop.

Source

The C-130 is very often used in places that experience icing. For example, the US Air Force flies the C-130 as a cargo/transport aircraft for Antarctic and Greenland operations:

(Source: Popular Science)


In theory which causes more parasitic drag? A large smooth wing or a small, rough exhaust port?

The wing creates more drag due to the much larger area.

The wing is beautifully streamlined and the flow stays attached to the wing if the angle of attack remains below stall values. So friction drag is the only drag that acts upon the wing, while stubby shapes like exhaust ports have friction drag and pressure drag. This means that area for area, short stubby shapes have way more drag, as illustrated in the figure below from Prouty. But multiply with the length of the wing & stub, and the picture changes.

But the exhaust ports don't have pressure drag, because the exhaust gases are ejected backwards, in the spot where normally the separated airflow would extra drag.


Term to differentiate between a flight and a flight instance?

You might say "the QF 72 service between Singapore and Perth" for the flight schedule, and "the QF 72 flight on July 25" for a particular instance of the flight.

The term service used in this way is seen more often in other transportation sectors such as bus and train. But it can also apply to scheduled air services.


Is MIL-STD-1553 still used in modern aircraft?

MIL STD 1553 is alive and still in use.  Backwards compatibility will keep it around for some time.  Not only is it used in aircraft but also on spacecraft.

It tends to be used for control applications and lower data rates.  High volume data, for example from sensors, will employ different bus structures.  Many control, communications and guidance applications can readily be accomplished with 1553.

Having said that, I cannot say whether it is right for you application, as I know little about your application.  Noise, data rates, latency and other factors may cause you to look at different interconnection architectures. There are many competing bus/LAN structures.


How can I best prepare for my first lesson on stalls?

You will impress your instructor most by being eager to learn and learning quickly, and by having done book work beforehand.  Just do some reading on stalls and really get to know the 2002's Operating Manual, especially the numbers and limitations.

Be careful about trying to show that you already know it all.  If a student has taken the time to learn the operating manual and knows all the important numbers and limitations by heart, and can recite emergency drills etc while under stress, the instructor will way more impressed than if a student tries to show they already know how to do the lesson.  That being said, just read up, and really learn the manual.


How to escape from an aircraft if the door is not armed?

The door the passengers are loading through is obviously one route, back down the jetway or stairs.

The door being "armed" does not affect whether it can be opened or not.  When the door is armed, opening it will also automatically inflate the escape slide.  When the door is disarmed, the slide will not inflate.

Additionally, each door has a manual inflation handle for the escape slide which the crew can use to deploy the slide if needed.

I could not find a non-copyrighted picture to include.

You could start here for more information.


How much lift must a helicopter rotor produce?

In the hover, it must produce a lift force equal to the weight of the helicopter, in order for the helicopter to remain at constant altitude. A helicopter with a mass of 700 kg must produce a lift of 700*g = 6,867 N to hover at constant altitude.

In forward flight at constant altitude, the rotor must produce more thrust with the thrust vector tilted forward at angle α. Vertical thrust component = lift must be equal to weight for the helicopter to fly at constant altitude. As the helicopter picks up speed, less power is required to provide the same amount of thrust due to reduction of induced drag - if power is not reduced, the helicopter starts to climb when transferring from hover to forward speed.

If in the hover the rotor produces more lift than the weight, let's say 710*g,it accelerates upwards, resulting in a vertical velocity component that results in an additional aerdynamic damping force, proportional to vertical speed, caused by change of rotor blade Angle of Attack and fuselage vertical drag. So for a 700 kg helicopter with a rotor that exerts 710*g = 6,965 N, the extra 98 N is used for overcoming aerodynamic drag associated with vertical speed.

Assuming that by "lift" only the vertical component of thrust is meant: more lift than weight results in a constant upwards velocity. Less lift than weight results in a constant downwards velocity, even in a free fall (terminal velocity).


What is the maximum takeoff weight allowed for a part 103 ultralight?

14 CFR 103.1

The FAA currently does not discriminate between "VTOL" and "normal" ultralight aircraft, nor between gas-powered or electric. The aircraft, if powered, cannot weigh more than 254lbs "empty" weight excluding floats and safety equipment that deploys in an emergency situation.

I'm not sure what you mean by "peak limit" or "continuous operation". The aircraft, when weighed without liquid fuel, must be less than 254lbs. It can carry up to 5 US-gallons of fuel (which can add up to 30lbs).

There is no limit to the MTOW for the aircraft though, it can carry a 400lb individual if you can make it fly, but it can't carry more than 1 person. So if the aircraft weighed 253lbs, you were 400, fuel is 30 that is 683lbs and still legal under Part 103. (Depending on how liberally you want to apply the "single occupant" rule, you may try to squeak your 200lb Mastiff aboard as well)


For a homebuilt or ultralight, yes.  There are high voltage diodes that take a high tension lead from 2 separate sources with a single output, made for racing, that allow you to run a single plug from either of two sources, whatever they are.  They are popular on Corvair aircraft engine conversions.   You can run a mag and battery system together, or two battery systems, or whatever, with a one-or-the-other ignition switch.


Why are row numbers 10 and 11 skipped on Frontier's A-319?

Airline row numbering has more to do with fleet consistency than sequential numbering in one airplane type.

Head over to SeatGuru and look up Frontier. They fly 3 types of mid-size narrowbody - A319, A320, Embraer E190 - and not surprisingly row 12 is an exit row in each one. The E190 and A319 don't have row 11, only the A319 is missing row 10.

It's the same reason 2+2 seating skips seats B and E ( AC DF ), where 3+3 seating goes all the way across ( ABC DEF ). Widebody aircraft have a different sequence because it doesn't need to match - the same cabin crew will rarely work both major classes and they don't tend to run regional airlines on widebody (long-haul) routes.

Look at Air Canada's fleet - row 18 is the beginning of economy and an exit row in almost the entire widebody fleet (the exception is probably historical).


This depends on where you are in the world but under the FAA here in the US the FAA defines it as

  Flight level means a level of constant atmospheric pressure related to
  a reference datum of 29.92 inches of mercury. Each is stated in three
  digits that represent hundreds of feet. For example, flight level 250
  represents a barometric altimeter indication of 25,000 feet; flight
  level 255, an indication of 25,500 feet.

In other words its the altitude if you set your altimeter to 29.92. In the US all aircraft in class A airspace (18,000 and up generally) set their altimeter to 29.92 thus flight levels are used at that altitude. When an aircraft is below Fl 180 the local altimeter setting is used.


Mitteneffekt
The pressure fields of the left and right part of a swept wing interfere at the center, causing a drop in lift. The Horten brothers called this "Mitteneffekt", and it was never properly translated into English, so the German term is used. The Hortens increased chord at the center trailing edge of the wing, reducing local sweep and increasing the area for lift creation. This helped to fill the "hole" at the center and at the same time allowed them to better enclose the pilot.

Lift distribution over unswept and swept wing (picture source)
The same is achieved with the reduced trailing edge sweep, airfoil change and change in incidence at the wing center of airliners. Since this part is occupied by slotted flaps, the rounded trailing edge contour of the Horten planforms is not possible there, so a straight line is the best solution.
Structural Efficiency
Large wings need heavy spars, and saving some spar weight goes a long way in reducing lift requirement and, consequently, drag. While smaller airplanes do not profit much from an increased wing root thickness, larger ones can save hundreds of kilograms by increasing their root thickness. Since the flight Mach number must not suffer from this thicker root, the simplest solution is to extend the wing chord at the center. (Sorry, the link leads only to a library, but the thesis gives extensive proof.)
A nice side effect is the increased space for housing the landing gear.
Separation Control
Interference between fuselage and wing will cause separation there to start earlier than on the clean wing. Also, the superposition of the flow fields of fuselage and wing will cause shocks at a lower flight Mach number. Therefore, aerodynamic efficiency both at low and high speed is increased when the local lift coefficient drops near the wing root, so the flow has more margin before shocks or separation start. By increasing root chord over what is required for an elliptic lift distribution, the local lift coefficient can be lowered while the circulation distribution stays elliptic.
Flap Effectiveness
With an unchanged leading edge sweep, Mach tolerance is not much affected, but the lower trailing edge sweep is very helpful for increasing the effectiveness of the trailing edge flaps.
Regarding the word "Yehudi": This is the first name of a famous violinist, but I do not connect it with a wing planform.


Using aluminium busbar/cables in an aircraft instead of copper

While it is true that copper is 1.6 times more conductive than aluminum per volume,

  Conductivity in $\frac{\mathrm{MS}}{\mathrm{m}} = \frac{\mathrm{10^6}}{Ω\,\mathrm{m}}$:

  copper:    56
  aluminium: 36
  $$\frac{56}{36} = 1.56$$

aluminium is 2.1 times more conductive than copper per weight.

  Density in $\frac{\mathrm{g}}{\mathrm{cm^3}}$:

  copper:    8.96
  aluminium: 2.7
  $$\frac{36 \cdot 8.96}{56 \cdot 2.7} = 2.13$$

Another important metric concerns the cost. The conductivity per cost is 7.1 times higher for aluminium.

  Base metal price in $\frac{\mathrm{US$}}{\mathrm{lb}}$ (as of today):

  copper:    2.71
  aluminium: 0.81
  $$\frac{36 \cdot 8.96 \cdot 2.71}{56 \cdot 2.7 \cdot 0.81} = 7.14$$

Aluminium wiring is safe if it is sized and terminated correctly. In comparison with copper, aluminium is softer, shows more creep, and has 30% stronger thermal expansion.


Why are some item numbers missing in ICAO flight plans?

To complement @ocirocir 's answer and link, the messages used by air traffic services are not limited to flight plans.
Below from ICAO Doc 4444 are all the fields and the intended use. As you see, the FPL is just one row, and other "missing" fields appear in other messages, while others are just currently not used:


How does pregnancy affect airline pilots operating under FAA regulations?

As long as the pilot is having a first class medical, her pregnancy should have no effect on the operations, at least legally, though the regulations differ from country to country.

I'm not aware of any FAA regulations that prohibit pilot ing during pregnancy. The closest it comes is in 14 CFR § 61.53 - Prohibition on operations during medical deficiency, which says (noting that pregnancy is not a medical deficiency in any way and the regulation is taken here in the widest sense) that:

(a) Operations that require a medical certificate. Except as provided for in paragraph (b) of this section, no person who holds a medical certificate issued under part 67 of this chapter may act as pilot in command, or in any other capacity as a required pilot flight crewmember, while that person:
(1) Knows or has reason to know of any medical condition that would make the person unable to meet the requirements for the medical certificate necessary for the pilot operation

As long as the pilot feels that she is medically fit and has a valid medical certificate, they can't be legally prevented from flying the aircraft.

In case of other regulattions (like EASA), pregnant women are not allowed to pilot after 26 weeks of pregnance. For example, UK Aviation Authority says:

(c) Pregnancy
(1) In the case of pregnancy, if the AeMC or AME considers that the licence holder is fit to exercise her privileges, he/she shall limit the validity period of the medical certificate to the end of the 26th week of gestation.  After this point, the certificate shall be suspended.  The suspension shall be lifted after full recovery following the end of the pregnancy.
(2) Holders of class 1 medical certificates shall only exercise the privileges of their licences until the 26th week of gestation with an OML.

There are a number of medical issues that the pilot should be aware of while pregnant, so that appropriate measures could be taken, like,

Ability to move the controls to their full extent.

Ability to wear seat belts.

Effect of high altitude operation on the foetus
among others. The airline policy will vary and they have to consider a number of other conditions- for example, the ability of flight crew to egress during a crash etc.


Is a VOR usable on the ground when it's located at a higher elevation than the receiver?

In order to receive a VOR station there must be a line of sight from the airplane to the VOR.  This is basically what your chart is referencing, you can maintain line of sight at longer distances at higher altitudes.  It could be possible that the VOR is higher than the airplane and you could receive the VOR while flying below the VOR as long as you have line of sight.  However it would probably be best to make sure you have enough altitude before you try to intercept the VOR to make sure you don't have a controlled flight into terrain incident.


There are a few ways that yaw control is achieved.

The easiest and the first to be successfully used would be to have cables from rudder pedals on each side of the rudder to deflect the control surface and control yaw.

Airplane Flying Handbook pg 2-1

The first application to control yaw unsuccessfully was the development of gears and linkages that will control both roll and yaw with the pilot stick.  It was quickly discovered that there are cases where you may need to use the controls separately.
Yaw damper is an electronic device that sense yaw rate and will provide inputs to the rudder to keep the airplane coordinated.

https://www.gulfcoastavionics.com/images/products/3552/detail/detail.jpg


Has a life raft ever been successfully deployed in case of an accident?

Sure.  For example, Eddie Rickenbacker and 6 other people spent 3 weeks adrift aboard life rafts after their B-17 ditched in WW2.

Read more -- https://www.historynet.com/eddie-rickenbacker-and-six-other-people-survive-a-b-17-crash-and-three-weeks-lost-in-the-pacific-ocean.htm


Are there any Part 135 (On-Demand Passenger Charter) companies out there that use Aviation Bio-Fuel?

Biofuel has already been considered and tested on some aircrafts. Here you can find an article about tests.It states at least six of them

  At least six airlines, including KLM, Lufthansa and Finnair, have now
  used biofuel on flights carrying passengers.

However there is still a long way to go.On wikipedia it says

  The sustainable aviation fuels certification and production pace seems
  insufficient to meet the IATA target of halving the CO2 emissions by
  2050

But airports do not supply bio-fuels for now since you need tons, even for one flight.

And for the list that used biofuel on their commercial flight you can check this list out. On that list i know KLM, interjet,Hainan offers charter flight. So it is safe to say those companies environmentally conscious, if you want.


Do aircraft engineers take into consideration engine placement to avoid ground strikes in a cross-wind landing?

For jet aircraft, there is no rule about preventing a nacelle from contacting the ground before the wingtip. There will be a design requirement that the airplane can touch down at a certain angle of bank and have the landing gear touch down but not strike a nacelle or wing, but not whether nacelle or wing must strike first. The nacelle is already designed for a wheels-up landing, so it's possible it could survive better than a wing tip. While it's certainly more of a risk on 4-engine aircraft, it can also happen on twin jets.

Propeller aircraft are typically designed such that gear and wingtip will make contact without the propeller making contact, either through having gear directly below props on a low-wing configuration, or through a high-wing configuration. While a jet engine nacelle can sustain some structural damage in a strike, it will typically not affect the engine's operation. If a propeller gets damaged it could cause that engine to become unusable, making it much more difficult for the crew to successfully perform a go-around.


Is it possible to fly a Cessna 172 vertically?

Might be a good idea to stay humble.  Any type of acrobatics may not be recommended if the aircraft has
a gravity only fuel feed.  Keep in mind if (for example you attempt a loop) and you only make 1/4 of the way through (and are nose up and have lost all forward airspeed), 5 things can happen. Fall straight down tailfirst (will not last long as this is most unstable and the nose wants to be down), tip left, tip right, nose drops back to horizon, nose falls INVERTED to horizon.  The last one I would not want to be in.
Tipping left or right can be helped with rudder and is known as the "stall turn" or Hammerhead.  Nose dropping to horizon would be similar to a stall recovery.

There are aircraft much more suited to do this and qualified people who would be happy to take you up and show how it is done. You may wish to speak with them.


What are Altitude, Attitude and Heading Hold?

These are generally 3 different auto pilot modes. The first two are related to pitch and the third to heading/roll a nice overview can be found here

Altitude Hold: Generally speaking setting an autopilot to altitude hold will cause the autopilot to maintain that altitude by varying the pitch of the aircraft. Depending on the system it may attempt to maintain the altitude even its not possible which can lead to a dangerous situation.

Attitude Hold: Is the autopilot setting that will hold the pitch of the aircraft constant when set to this mode. For example if you depart and climb out at an 8 degree nose up attitude, engage attitude hold, the aircraft will hold 8 degrees nose up until set otherwise or shut off. As noted in the comments this can create a very dangerous situation as the aircraft may continue to maintain pitch (generally for a climb) even if power does not allow this can cause a stall at high altitude. More sophisticated auto pilots allow for constant airspeed climbs which are far safer.

In my experience you are generally in either altitude or attitude mode at any given time.

Heading Hold: This is a roll control mode that holds the heading of the aircraft (keeps it on track). It will typically be slaved to a bug on the HSI where you can set the heading the autopilot flies.


Why are landing fees at large airports based on weight?

From Anne Graham's book, Managing Airports:

  This charging mechanism uses the ‘ability to pay’ principles, since
  airlines using larger aircraft are in a better position to pay higher
  charges. Some costs such as runway wear and tear do increase with
  weight and also larger aircraft require vortex separations, which can
  reduce the number of aircraft movements during a certain period.
  Overall, however, there is not a strong relationship between aircraft
  weight and airfield cost. A flat rate landing charge for all aircraft
  types may be more appropriate, particularly at congested airports.
  This is because the cost of occupying the congested runway is movement
  related and independent of aircraft size. Each aircraft movement will
  consume the same resource.


If jet engines did leave chemtrails, wouldn't the chemicals cause adverse reactions in the engines?

Jet fuel is seldom if ever pure hydrocarbon molecules. It's got a lot of other stuff mixed into it to improve the properties. I'm going to quote Shell for the sake of examples:

  Antioxidants (gum inhibitors) must be used in Avgas to prevent the
  formation of gum and other antioxidation products. Jet fuels, which
  are inherently more stable than gasolines, may contain them, depending
  on the treatment process used during manufacture.

  A metal deactivator - now rarely used - may be added to nullify the
  effects of dissolved trace metals, especially copper, which can impair
  the thermal stability of jet fuels.

  Corrosion inhibitors can be used to reduce corrosion in fuel system
  and improve the lubricity - lubricating properties - of jet fuels.

  Fuel system icing inhibitors reduce the freezing point of any water
  that may be in the fuel system and prevent the formation of ice
  crystals that could restrict fuel flow. They are mandatory in military
  Jet but are not used in civil aircraft that have fuel heaters. They
  may be added to either Jet or Avgas during the fuelling of small
  aircraft.

  Static dissipater additives minimise the hazardous effects of static
  charges that build up during movement of jet fuels. They are sometimes
  used in Avgas as well. Source

Further analysis

No practical application:

  Aluminium based aerosols, Mono-atomic gold, Nano aluminum-coated fiberglass, Radioactive thorium, Cadmium, Chromium, Nickel, Desiccated blood, Mold spores, Yellow fungal mycotoxins, Polymer fibers, Barium.

Useful additives from your list:

  Ethylene dibromide- Anti-Knock agent in aviation fuel.
  Alumium: Derivatives containing it have been used.

Many of the materials you list might have the very real potential to (seriously) damage jet turbines and piston engines if mixed in during extended use.


Is C.G. of wing itself in line with hang point (hang glider)?

The centre of gravity must imperatively be located between the nose and the quarter of the mean aerodynamic chord. The quarter of the mean aerodynamic chord is the point where applies the resultant of the forces and moments aerodynamic. One finds of it the definition theoretical low.
If the centre of gravity is placed behind the quarter of the average aerodynamic cord, the wing is unstable and completely impilotable... If the centre of gravity is too ahead, it is hardly less serious, the wing " marsouine " by carrying out oscillations around the axis of the pitching, oscillations which can, at worst if the control surfaces are not sufisament dimensioned to be able to increase the moment to pull up, not diminishing and leading to the crash..
Check out http://aeropic.free.fr/pages/modelisme/theorie/theorieenglish.htm#:~:text=The%20centre%20of%20gravity%20must,of%20the%20mean%20aerodynamic%20chord.


Why did the Concorde require a droop nose and how did it work?

1) Though already mentioned that this might be too broad, I would dare to guess a properly fitted camera could do the trick. But I doubt that this would be effective considering the technology of the era that Concorde was developed.

2) Concorde due to its design for supersonic speeds, it was generating too little lift at low speeds (like those needed for landing). So they had to take into advantage another way of producing lift: vortex lift. In order to produce vortex lift, you need relatively high angles of attack and consequently high pitch attitude.

3) I cannot answer this since I am not an engineer. Though with little googling I found this. It seems to be very detailed, with photos of the lever and diagrams of the mechanism.


There are several ways to do what you are requesting.  One way is to follow the guidance in the Airman's Information Manual, para. 5-1-7 (AIM).  This guidance describes how to use a "Composite Flight Plan."  With this procedure you are filing a VFR flight plan and an IFR flight plan simultaneously, and in your case with the intention of using the VFR Flight Plan first.
Although the description in the AIM describes a flight in which the pilot is not already talking to ATC (as you plan on doing because you will be in Class B airspace) the general procedure is clear.  Depart the airport, open the VFR Flight Plan with the nearest FSS (or other facility), and at the appropriate point where you planned to begin the IFR portion of your flight and while in communication with ATC in the Class B airspace, request the IFR clearance.
After picking up your IFR clearance make certain that you cancel your VFR flight plan (you can ask the IFR controller to do this for you, but if you have a second radio you may just want to call the nearest FSS and cancel it yourself).
A second, perhaps more efficient method to accomplish what your question suggests is to: (assuming you are departing from an airport near or within Class B airspace)

File an IFR flight plan with a starting point at or abeam whatever location/fix etc. you want to begin the IFR route.
Obtain a VFR clearance into the Class B airspace from ATC (you won't have a VFR Flight Plan, but you will be receiving flight following and thereby realizing essentially the same benefit).
At the appropriate point as filed in your IFR Flight Plan, request the (IFR) clearance from the controller you are in communication with.
In this case you won't have a VFR Flight Plan to cancel.

I'm not suggesting that you should not have a VFR Flight Plan if you will be traveling anything other than a short distance before you start flight following (or a Class B clearance) from ATC.  But, if you are departing an airport near the Class B airspace and will be talking to ATC shortly after takeoff the benefits of having a VFR Flight Plan may be essentially irrelevant if you are already talking to ATC receiving flight following or Class B service and will be transitioning to an IFR clearance.
Lastly, if your only intention is to get an IFR clearance while you are flying along VFR, see "How do you request a "pop up" IFR clearance?" which has already been answered in this StackExchange. But since your specific question indicates that you are interested in a procedure where you have filed an IFR and/or VFR flight plan before departing I hope my comments help your understanding.


Where's the A318 on the runway that caused a 747 to go around?

Look for the blinking light in the center of the runway
That's the strobe lights of the A319. It's all you can see of it in the video.  I had to step frame by frame through the video to capture a frame where it was visible and another frame where it wasn't.

Sorry for the turbulence.  :)


Difference between Assessment and Critique?

My understanding of the difference between assessing and critiquing is this.
Assessing or assessment involves grading a subjects performance or ability against a given standard or ideal. This can involve a letter or numeric grading, or a simple pass/fail grade. When grading against an ideal subject or situation, absent of an accepted standard, can be rather subjective.
Critiquing or a critique is a judgement of the way a subject performs. It is not meant as a way to judge the performance. Rather, it is meant to provide feedback to the subject regardless of the grade against the standard in order for them to improve. This is much like coaching. You would coach both your worst and your best performer for them both to improve. Even if their performance warranted a passing grade.


If all passengers moved to the back, front or one side, would they crash the plane?

The issue at hand is known as weight and balance. Most of the larger airliners do not have much of a problem with a large shift in Passenger weight but shifting cargo has indeed caused accidents (See https://en.wikipedia.org/wiki/National_Airlines_Flight_102) which was what happened when a large amount of cargo, not properly secured, fell towards the back of the aircraft during takeoff causing the B747 to crash.

In general, the smaller the aircraft, the more sensitive it is to Moment and Arm changes in its weight and balance. If there is too much weight towards the rear (known as Aft-CG) then the pilot may not have enough down-elevator authority to keep the aircraft from pitching up even further.

A forward-CG problem may also happen where there is too much weight towards the front of the aircraft which may cause the pilot to run out of UP elevator authority during the landing flare, causing a nose-first landing.

Both fore and aft Center-of-gravity issues have caused airline crashes in the past although usually not from passengers but rather shifting cargo not properly secured.

I am not aware of any sideways loading issues that could not be corrected with aileron (assuming both wings are attached). Flying with more fuel in one wing than the other can be tiresome but is usually safe.


Why does the A320 IR2 MEL OPS procedure suggest to switch to ADR3?

Even if ADR and IR perform two independent and separate functions, they are the same hardware object (example). A IR2 malfunction is a malfunction: you do not know, in general, what is causing the problem of IR2 and it can possibly be a common problem (maybe undetected on ground by the ADR2).
For example, in the ADIRS Honeywell manual you can find in the IR FAULT chapter:

The ADR function of the affected ADIRU may possibly still work, even
if the IR function is not working. Cross comparing air data
information gives the pilot some idea of the validity of the ADR data
for that ADIRU.

So you have no guarantee that if IR2 is faulty, then ADR2 works. This is why, for precaution, you switch F/O on ADR3.


Can a Rutan Quickie be made into a legal Part 103 Ultralight?

I doubt the Quickie would fly well enough at very slow speeds to meet the rest of the Part 103 requirements -- specifically, the limit on maximum level flight speed.  Limiting fuel capacity is easy, and the 18 HP original engine worked well enough on the Q1 -- but it was a lot faster than 55 kt (close to double, as I recall).  From comments (thanks, Gerry) I understand the Q1 has a stall speed of 42 kt -- fairly reasonable for a light aircraft, but well above Part 103 maximum of 24 kt.

You might be able to slow down enough by installing a flatter-pitch propeller, but that would have other effects (overspeeding the engine, for instance) that would need to be addressed, and then you'd be trying to fly with almost no speed range -- 42 to 55 kts isn't, IMO, a safe performance envelope (and yes, the Q1 would still go faster than 55 kt in a dive, but the level flight and climb performance are where the safety issues lie in this case).


What is the inner dashed line on this helicopter chart?

First of all, sorry for the confusing original image. It comes from foreflight and has three charts superimposed. 1) the sectional, 2) the houston helicopter route chart (white background) and 3) the foreflight aeronautical chart showing the airpace again. I'm attaching a simpler one which shows just the sectional and the helicopter route chart.

It turns out that the helicopter route chart is simply out of date (!?). I called the Sugarland tower and they confirmed that 2 years ago the Delta expanded from a 4.2 mile radius to a 5 mile radius. The Helicopter route chart still depicts this as 4.2 (https://aeronav.faa.gov/content/aeronav/heli_files/PDFs/Houston_Heli_9_P.pdf) Hopefully the next edition will correct this.


What are the pilot rating requirements for amphibians?

According to the Seaplane Pilots Association you can operate an amphibious airplane on hard-surface runways with a land class rating but need a seaplane class rating to take off or land on water, and vice versa.

As far as the regs, it seems that the airplane can simply be considered either land or seaplane class depending on how you are operating it.


How will radar systems be used in FAA's NextGen ATC plans?

Under the ADS-B rule of the FAA aircraft operating in Classes A, B, and C airspace, as well as certain other specified classes of airspace
within the U.S. National Airspace System are required to operate ADS-B Out avionics.

This means that these aircraft can be tracked without the use of radar. These ADS-B tracks will be more accurate than radar tracks and have a higher update rate. However for reasons of integrity, continuity of service and security, radar will continue to provide coverage. Currently a lot of airspace is covered by multiple radar layers, the introduction of ADS-B allows for a reduction in redundant radar coverage.

Aircraft not equipped with ADS-B (operating outside of class A,B, or C airspace) will be tracked using radar. The radar tracks will be broadcast on TIS-B (Traffic Information Service - Broadcast) so that aircraft with ADS-B In receivers detect these aircraft as well.


How do aircraft altimeters calculate altitudes accurately while airborne?

Altimeters are calibrated to a standard atmosphere model (International Standard Atmosphere, ISA).

What the altimeter shows you is the vertical distance between the altitude equivalent to your current pressure (pressure altitude) and a reference "pressure altitude". The reference pressure altitude is set in pressure units (hPa or In. Hg) on the altimeter subscale. This is known as the "altimeter setting", set in the "altimeter setting window".

Image credit: FAA Pilots Handbook of Aeronautical Knowledge

Flying at lower altitudes (below "transition altitude"), the altimeter is set to airport/regional QNH, which is a pressure calculated so that if you were standing on the measurement point, the altimeter would indicate your exact elevation. At other altitudes, it would approximate altitude above mean sea level, although it would show incorrectly if temperature differed from ISA.

Above transition altitude, the altimeter is set to QNE, or standard pressure (1013.25 hPa, or 29.92 In. Hg). The altimeter will now only indicate correctly if both temperature and pressure are in accordance with ISA. You are now flying on "flight level" (where the FL is your QNE indication in hundreds of feet, ie 20,000 ft = FL200).

For the purpose of avoiding obstacles, both QNH and QNE have to be corrected using various methods, which are described in various manuals. (QNH for temperature, QNE for both temperature and pressure, both for other possible factors such as wind etc). For instance, this diagram shows three different aircraft, all flying the same pressure altitude, but with three different true altitudes:

Image credit: FAA Pilots Handbook of Aeronautical Knowledge

However, altitude is also used for the purpose of traffic separation, and for this purpose, neither QNH or QNE is corrected. This might sound counter-intuitive, but as long as your altimeter is showing the same error as any conflicting traffic, you can be safely separated, therefore: The altitude shown on the altimeter is not corrected at all (except by calibration for possible aerodynamic interference, such as compressibility, venturi-effects etc).

In technically sophisticated aircraft, barometric altitude input is used for vertical navigation. Since vertical navigation is concerned with the true altitude of the aircraft, the aircrafts Air Data Computer (ADC) will calculated a true altitude based on information available to it (either through sensors, or through pilot input). The true altitude is however, as stated, not shown on the pilots primary flight instruments.


How is auto-rotation different in coaxial rotor helicopters?

There's one major difference between a coaxial helicopter and a conventional single main rotor -- single tail rotor helicopter during autorotation: yaw control.

A conventional helicopter has a main rotor which produces a torque. The tail rotor thrust, applied at the end of the tail boom, provides a counter-acting "anti-torque" to keep the helicopter pointing when the pilot wants it.  As the pilot, when I change the collective pitch of the main rotor, to go into a climb or a descent, the torque required to drive the main rotor goes up or down, and the pilot counters by raising or lowering the tail rotor collective to change the tail rotor thrust to match.  Additionally, if I want to yaw the nose to the left or right, I can use the pedals to raise or lower the tail rotor thrust in order to temporarily upset the balance between the main and tail rotor torques and steer the aircraft.

Now, consider how yaw control works for a coaxial helicopter.  The torque of the upper rotor is now counter-balanced by the torque of the lower rotor.  To yaw the helicopter, the pedal inputs are set up to upset the balance of torques by raising the torque on one rotor (by increasing the collective) and lowering it on the other (decreasing collective), while maintaining the same thrust.

Now, when I increase my rate of descent to autorotation, the engines are no longer providing torque to drive the main rotor--the rotor is being driven by the relative wind.  In a conventional helicopter, the tail rotor is still being driven by torque transmitted from the main rotor through the drive shafts--so while there's no main rotor torque to balance, I can still use the pedals to change the tail rotor thrust and control my yaw.  However, in a coaxial helicopter, when the  torque on the rotors is low, differential collective does not have very much control authority: depending on the collective setting, pedal inputs can have a weak effect, no effect, or most surprisingly, a negative effect!  To counter-act this, most coaxial helicopters have very large vertical fins to provide good low-speed directional stability and many have rudders to augment control.

For instance, here's a picture showing the empennage of the Kamov Ka-25 (from aviastar.org).

More modern machines also have control systems that reverse the effect of pedal inputs on differential collective at the very low collective stick settings where control reversal can occur.  Flight manuals for coaxial helicopters advise against reducing forward speed too quickly during autorotation, since the directional stability is provided primarily by the body and tail.


Is the low air pressure on top of the wing the major contributor to lift?

You must have read the wrong sources. Low pressure on the upper surface of the wing is really the major source of lift. The surrounding air sucks the wing up as much as it pushes it up from below.

On a flat plate, the contribution of suction and pressure is about equal. On a wing with a thick airfoil, some additional suction is added on both sides due to the displacement effect of the wing, so the resulting negative pressure change on the upper surface becomes bigger than the positive pressure change on the bottom. At low angles of attack, you even get suction on both sides.

Your pressure calculation is maybe helpful for the mean pressure difference between both sides of the wing, but it will not give a correct value for absolute pressure. It is better to calculate lift from the momentum change imparted on the air by the wing, as shown in this answer.

Your example with the row is well chosen: The local height difference of the water to the undisturbed sea level is equivalent to the local pressure difference to the static pressure (a higher water level signifies higher pressure) and shows the approximate conditions on a section of the wing. The row is like an inclined flat plate. You can even change the angle of the row and see the additional trailing vortex as it floats away from the row.

Now for the hang gliders: They are peculiar in that the airfoil shape depends on local pressure, and early models did not use lengthwise stiffeners so the pressure over the fabric could invert when the wing caught a negative angle of attack for a moment. You are lucky that you could press the fabric up again: Several early hang glider pilots could not recover and fell to their death. This happened when designers tried to increase the aspect ratio of the initial Rogallo shape of their gliders. I only know a German word for this phenomenon: Flattersturz.


What is the identity of this abandoned, wrecked Sudan Airways airliner?

It looks to me more like an abandoned plane (that's fallen apart) rather than a crashed/wrecked one. A Sudanese A310 crashed at Khartoum in 2008 - but it caught fire and was destroyed, which clearly hasn't happened here unless someone came and repainted it afterwards.

This list gives ten A300s which have previously been owned by Sudan Airways; TC-OYC is stored at Istanbul (and this doesn't look like Istanbul), ST-ATA is stored location unknown, and ST-ASS was scrapped while last owned by Sudan. Of their A310s, ST-AST, is stored (location unclear); ST-ATN was destroyed by fire after a crash. So that's three A300/310s which might plausibly be lying derelict at a Sudanese airport.

For an alternative count, this thread lists four A300s "stored" at Khartoum, ST-ATA, ST-ATB, ST-ASS & ST-AST; all put up for sale as parts/scrap a few years back but never sold. No pictures but it's clear they're not in a great state.


Do Federal regulations compel airlines to avoid schedule disruptions?

The Department of Transportation has A Consumer Guide to Air Travel that discusses passenger rights regarding delayed and cancelled flights. Some key points:

Airlines don't guarantee their schedules, and you should realize this when planning your trip.
Overbooking is not illegal, and most airlines overbook their scheduled flights to a certain extent in order to compensate for "no-shows."
Airlines set their own "boarding priorities" -- the order in which they will bump different categories of passengers in an oversale situation.
DOT requires each airline to give all passengers who are bumped involuntarily a written statement describing their rights and explaining how the carrier decides who gets on an oversold flight and who doesn't.

There airline is required to provide various sorts of compensation if they bump you involuntarily and can't get you there within 1 hour of the original flight. This depends on how late you will arrive and what kind of ticket you have.
There is no rule that says airline employees must fly instead of customers, but each airline has their own Contract of Carriage that describes their rules. You can read United's here as an example. Rule 25 describes the process for denied boarding:

If there are not enough volunteers, other Passengers may be denied boarding involuntarily in accordance with UA’s boarding priority:
The priority of all other confirmed passengers may be determined based on a passenger’s fare class, itinerary, status of frequent flyer program membership, and the time in which the passenger presents him/herself for check-in without advanced seat assignment.

Of course IANAL but the way I read it, they "may" use any of those methods but they are free to deny boarding as they wish. Nothing stops them from choosing to bump customers before employees. Delaying or canceling a later flight because they bumped the employees would be more expensive than paying a few customers to be bumped involuntarily. But bumping employees may be less expensive than a PR fiasco.
There is also a program called Essential Air Service, where the DOT subsidizes airline service to smaller markets. Airlines bid to provide this service under certain conditions. Although I wouldn't say they are "compelled" to provide that service, if they don't meet the conditions, which could include not completing enough of the scheduled flights, they may not receive the subsidy.


Why landing gears still need bungee springs?

The key to this is the text in yellow in the bottom right-hand corner

Lower torsion link (Disassembled)

The bungee is simply being used to support part of the mechanism that is being worked on. It will be removed when the work is complete and the lower torsion link reassembled.


What is the difference between an Airbus A330-200 and an A330-243?

Airbus has a dash numbering system that specified the engine manufacturer and the engine variant in addition to the aircraft's series number. The system details can be found here:
http://www.aerospaceweb.org/question/planes/q0276a.shtml

The general format of the Airbus numbering system is Ammm-sevZ where the individual components are described below.

Ammm = model number
s = series number
e = number defining the engine manufacturer
v = number defining the version of the engine model
Z =  optional letter describing a variation of the series number

The series number refers to the different variants of a particular model that have been developed. Standard series numbers used by Airbus include 1 for 100, 2 for 200, etc. The primary exception to this system is the A300. The original series number designations used for variants of this model included the B1, B2, and B4 for passenger models as well as the C4 for a convertible freighter version. Later production variants of the A300 were designated as the A300-600 to become consistent with the rest of the Airbus product line.
The engine manufacturer codes that have been assigned to date include the following.

0 = General Electric (GE)
1 = SNECMA
2 = Pratt & Whitney (PW)
3 = International Aero Engines (IAE)
4 = Rolls-Royce (RR)
5 = Engine Alliance (joint venture of GE and PW)

The final number denotes newer
versions of the basic engine model. These numbers appear to start at 1
for the original engine and increase sequentially for updated engines.
An optional letter sometimes follows the series of numbers to
designate a variation on the series number. Common examples include
the following.

C = convertible passenger/freighter model
F = freighter model
R = long range model
X = enhanced model (?)


Why we don't see the "SkyRider" seats in action?

There are a lot of disadvantages, even if the possibility of lowering costs and increasing profits is a huge advantage for the airlines. This article discussed several issues from a passenger perspective:

Limited space in general (e.g. to use a laptop)
Face too close to the video screen in front of you (if there is one)
Doesn't fit tall, large, short or young people well (and I guess that older people might not be strong enough to use it)
Very limited space for carry-on luggage (because you lose space both under the seats and in the overhead bins)
Passenger resistance to the basic idea

The author's conclusion was that the seat isn't actually uncomfortable, just cramped, but he was very sceptical that passengers would be willing to use it.

Another article added some concerns from the airlines' point of view:

Could make cabin evacuations more difficult (and certification costs in general would be high for a completely new seating concept)
Difficult to market successfully
The manufacturer intended the seats to be used in a new budget fare class, not to replace current economy class seats (this adds more complexity to everything: aircraft layout and maintenance, marketing, booking systems etc.)

Both articles (and others) concluded that there's no fundamental technical or regulatory barrier to introducing them, the main problem would be convincing passengers to accept them. Even Ryanair - which is notorious for cutting costs wherever possible - rejected them although Wikipedia says that both Ryanair and Airbus have proposed an alternative but very similar concept in the past.

If the airlines really wanted to introduce this seating arrangement, I would expect them to keep the idea in the news as much as possible and generally work on convincing people that the seats are comfortable and it's a great way for them to get even cheaper tickets. Since they haven't done that (if they have, I haven't noticed) it seems unlikely that the airlines are actively working on them.


I think he wants to know that you have an understanding of P Factor, which is the main "imbalance" or thrust asymmetry issue that has a direct impact on you as the pilot when you fly the plane.


Why do I see moisture coming from the middle of the wing as well as wingtip vortices?

They are vortices coming from the flap panel, same as the vortices coming from the wing tip, but much more intense because the angle to the flow is so high.  Because of this, the pressure drop in the core of the flap vortice much more than pressure drop in the flow off the wing tip. This means the temperature drop is also much more, enough to condense the humidity in the air, like a horizontal tornado.