How were astronomical observations performed from Concorde?

The Concorde was first used for observing solar eclipse in 1973. The aircraft used was Concorde 001, piloted by André Turcat with a scientific team of 8 people from US, UK and France.

The main reason for using Concorde was that the eclipse can be observed above the clouds for far longer than on ground by literally 'chasing the moon'. Multiple instruments were used for observing the eclipse.

Institut Astrophysique de Paris used cameras to capture images of the eclipse using a telescope mounted on anti-vibration mounts, which looked out of the aircraft through one of five silica quartz windows installed in the Concorde's roof. The equipment is shown in the image below:

Source: xjubier.free.fr

Queen Mary College's InSb Far-Infrared Detector experiment consisted of an interferometer that used a tracking mirror to view the solar eclipse via a quartz window fitted into the roof of the cabin, as shown in this image.

Source: jcgl.orpheusweb.co.uk

The dark opening in the roof holds the quartz window of the cabin, which looks like this:

Source: xjubier.free.fr

This was the most important (structural) modification made in the Concorde (BAC was supposed to provide Concorde 002 for this flight, but they backed out when they realized that some holes were to be made in the roof).

Los Alamos Scientific Laboratory (LASL, later to become Los Alamos National
Laboratory) used a specially-designed 3-inch telescope which looked out of the
aircraft through a silica quartz windows installed in the Concorde's roof. One objective of the research was to look for oscillations in the sun's corona that occurred on a time scale of about five minutes (the eclipse was visible for ~74 minutes from Concorde).

The instruments were checked both in ground and air before the experiment.

Before installation of the instruments on the aircraft, they were tested on a low speed trolley, perhaps to check its sensitivity to movement.
After the ground test, they were installed on the aircraft and connected to the aircraft power system and checked.
Before the actual experiment, the aircraft were flight tested at supersonic speed with the instruments on board.

The Concorde was chartered for viewing Halley's Comet in 1986 and for viewing solar eclipse in 1999. These were chartered sightseeing flights (using unmodified aircraft), not scientific ones.


Why does an aircraft as big as the Airbus A400M use turboprops?

Both aircraft seem to have the same purpose

Not entirely.

The RAF see the C17 as a strategic airlifter, the A400 is seen as a tactical airlifter replacing the turboprop C130.

Strategic airlifters are more likely to make longer, higher-altitude journeys. Where jets are more fuel efficient. They are more likely to operate between airports with concrete runways where FOD is less of an issue.

Tactical airlifters are more likely to make shorter, lower-altitude journeys of the sort where turboprops are more efficient. They are more likely to operate between smaller airfields where FOD may be more of an issue.

References:

ThinkDefence
Airbus
RAF

Some random internet website alleges the fuel costs in \$ per Nautical mile are 19.63 for A400 and 88.14 for C17. They don't say for what mission profile. At a minimum, this illustrates that there is some motivation for matching engine types to expected mix of mission types.

The similar sized AN-70 also uses turboprop engines, illustrating that this choice is not unusual for this sized aircraft.


How can I get the velocity-power curve for a particular aircraft?

You are right, this curve has to be tested. Of course, during development a lot of simulation and wind tunnel testing is done to get the power required, but it still needs to be confirmed in flight test. The interaction of power plant and airframe can be quite complex, and only testing will ensure that the data is correct.

If it is not part of the manual, the plane's manufacturer will certainly have the power curves. Did you ask them for the data? And I would expect that you will find some data points in any handbook which will allow you to approximate the power curve. Start from the trim condition (basically, thrust equals drag) and calculate the curve with the help of a parabolic polar. Like that:

$$T = c_D\cdot q\cdot S$$

$$P = T\cdot v = (c_{D0} + \frac{c_L^2}{\pi\cdot AR\cdot\epsilon})\cdot v^3\cdot\frac{\rho}{2}\cdot S$$

Of course, now you need to get the zero-lift drag coefficient $c_{D0}$ somehow from one datapoint in the manual. Same goes for values like propeller efficiency or intake losses, because the listed power of the engine will not be what is effectively employed to generate thrust.

Nomenclature:
    $T$  thrust
    $v$  airspeed
    $q$  dynamic pressure
    $\rho$  air density
    $S$  wing area
    $c_L$  lift coefficient
    $AR$  aspect ratio of the wing
    $\epsilon$  the wing's Oswald factor


Why is most aircraft livery painted, rather than vinyled?

Changing the status quo always takes time. Aircraft have been painted almost since the dawn of flight (and the very earliest aircraft were still doped to stretch the fabric over the skeleton). That is reason in itself for antique and historical aircraft and their replicas to be painted instead of vinyled.

In addition, most liveries come factory-installed right alongside the host of other options available. Most high-end private jets as well as the big commercial ones are built-to-order inside and out, including the customer's brand livery. That livery, much like the factory color of a car, often stays with the plane its entire life, with only routine touch-ups performed as a normal part of maintenance. Refitting a fleet with new livery and/or interiors, until very recently, wasn't done often; Southwest's "Canyon Blue" livery change was noteworthy, as was AA's fleet rebadging, and neither airline bothered repainting planes that are on the way out anyway; the aging Super 80s as well as the 757s and some 767s are still in classic AA silver livery and will be that way until they're retired from the fleet.

So, aftermarket vinyl livery's market share is already somewhat limited; people buying a new jet will get their livery applied at the factory, and people buying a used jet and wanting the livery changed significantly are in for quite an expense even if they choose vinyl; the old painted livery will usually have to be removed and the plane refinished in a new base coat before the new vinyl decals are applied.

I would also venture, having seen aftermarket vinyl applied to other vehicles, that even if the utmost care is taken in applying it, the decal is always going to look like a decal, and it may not age well even with a meticulously-maintained airframe. If you're paying \$65 million (base price) for a G650, \$25,000 (or even \$100,000) for custom livery is a drop in the bucket.

Now, your 172 or Piper Cherokee sport pilot might be very interested in personalizing his plane on this kind of budget, as would an aircraft club of part-owners, or your self-employed commercial pilot like a crop duster or charter bush pilot. Vinyl on small planes thus makes more sense; however, it's still a significant expense, and a purely cosmetic one, so it's still rare to see a plane's factory paint scheme change significantly aftermarket, except for niche uses like aerobatics and stunt flying.


Are warbirds allowed to use afterburners?

No, no restrictions on using an afterburner. There are a few F104 Starfighters on the civil registration that must use the afterburner to take off.

However, most countries forbid supersonic flight by non military operated aircraft in their airspace. The only time Concorde went supersonic was over the ocean.


How does the V22 Osprey manage such high rotor speeds without shock waves?

The Osprey's engines drive the rotors at 412 RPM in heli mode or 333 RPM in forward-flight mode, according to this article. With a rotor radius of 5.8m, that puts the tip velocity at 250m/s, or about 75% the speed of sound, at the higher RPM. So they aren't near supersonic yet because the blades are short enough.

But there is a possibility of reducing blade length for higher forward speed and RPM, and there is research into how to make that possible on-the-fly:

  Helicopter performance depends on the length of the rotor blades. For heavy lifting, a large rotor works best, but short blades reduce drag and ultimately allow for higher maximum speeds. Farhan Gandhi, a Penn State University professor of aerospace engineering, has devised an elegant, simple way to achieve both configurations in the same aircraft, using the same rotor.


Is it practical to use ground effect to extend range in an emergency?

When flying close to the ground, there is an important reduction of induced drag, the larger the closer to the ground one flies, so the airplane needs less engine thrust to keep a given airspeed. Anyone who has made a low pass over a long runway may attest this...

Flying in ground effect is a nice way to save fuel and extend the range. I remember reading that it was often used by carrier planes returning from a mission low in fuel...


What type of aircraft did these drop tanks come from?

It looks like they were used some on the F-80 like you said, but also on RF-80s, T-33s, F-94s, and Navy TO-1s, TV-1s.  They look similar to the Misawa tanks, but are different.

http://tailhooktopics.blogspot.com/2017/06/lockheed-pf-80-shooting-star-tip-tanks.html

https://commons.wikimedia.org/wiki/File:TV-1_Shooting_Star_at_NAS_Oakland_in_1954.jpg


How do propeller planes sync their propellers?

I fly a large 4-engine turboprop.  It uses constant speed hydraulic props, which automatically change blade angle to maintain 1020 rpm.  The sync box (which I was unable to find a picture of) takes inputs from each engine's tachometer generator (where it gets the RPM signal) and a pulse generator, which is a magnetic pickup right behind the prop.  There is a magnet on the number 1 blade of each prop.  With this information, the solid state logic components inside the sync box can slightly change blade angle by sending power to the speed derivative servomotor.  This is different from the answer that @davidinnes provided, but I suspect that he's correct for the type of propellers he's familiar with.  The sync system on the P-3 also takes inputs through a potentiometer attached to the power levers, and can start increasing or decreasing blade angles if you change your power setting quickly.  It works faster than the hydromechanical system and lessens RPM overshoots and undershoots as the prop works to get back to 100% rpm.

In this picture you can see syncrophasing in action.  The props are all slightly out of phase with each other, which reduces noise and vibration. #2 and 4 look pretty close, but it's far from a perfect system.  You can definitely tell the difference from the cockpit when it's working well.  Again as @davidinnes mentioned, you can adjust the system to the change where the point of minimum (or maximum) noise is in the cabin.  We call it "running the buzz" up and down the tube, and it's a great way to annoy a navigator that you don't like


Are peer-to-peer communications feasible between aircraft?

Yes, this we could do this.

Actually, we already do it: If an airplane cannot be joined by ATC, ATC will ask planes in the neighbourhood to relay the message.

As for what you are actually asking, which is a P2P mesh network for data or ATC, without active pilots involvement, this could work but would be completely impractical:

Mesh networks are still an active research topic (i.e., not exactly production ready), and offer little to no advantage over a traditional communication (satellite, aircraft to ground) that nobody would bother implementing this.

Few of the downsides are:

What if there is no plane to relay the message ? You are back to P2G (Plane to Ground), so why not use P2G in the first place.
What if there is a broken/rogue airplane that blocks/modify/fake your messages ?


What is the pilot's obligation to verify a registration has not expired?

You verify new (expiring) registrations the same way you verified the old ("for life") registrations -- by looking at the document. You just have to pay attention now (it's not just "It's there", you need to check the expiration date too).
New-style registration certificates (issued some time after October 2010) are supposed to have the expiration date clearly printed on the certificate (In the lower-left corner, under the date of issue).
For certificates without an expiration date printed on them (registered prior to October 2010) the FAA established a table of expiration dates back when the re-registration requirement was initiated.
ALL of the old certificates have expired by now: The last ones expired December 31, 2013.

As regards the pilot's liability, an unregistered aircraft (or one with an expired airworthiness certificate) is de facto unairworthy:

Does expiration of registration affect an aircraft's airworthiness certificate?
Because an aircraft with an expired registration is not registered, its airworthiness certification would be considered ineffective. Without registration the aircraft is not authorized for flight.
…

From The FAA's registration FAQ.
Aside from being a violation of the FARs to fly the aircraft with an expired registration (because it's "not airworthy") this triggers other implications, for example most aircraft insurance is invalid if the aircraft is "not airworthy" .


Do crew need visas when landing at airports in countries other than their own?

It all depends on the laws of the country that the crew is visiting.  Some do and some don't.  Many do unless they have a reciprocal agreement with the pilot's country, in which case they don't.

This would be a great question for a specific country pair, or even if you want to know the laws about a specific country (in which case we could give the actual requirements), but the best answer for a general question like this is "it depends".

In some cases, the crew isn't even required to clear customs unless they are leaving airport property.  Other times they have to clear as soon as they land.

Part of qualifying for a route with the airlines is making sure that you have the required visas.  Having two passports help a lot in getting multiple visas, because they can keep flying internationally while the visa application is in process.


May pilots perform FMS database updates under Part 135?

Updating a navigation database used to be considered preventative maintenance and was required to be performed by a mechanic under Part 135.  However, the regulations were changed at the end of 2012 (here is the final rule) and it no longer falls under this category so pilots are allowed to update "aeronautical databases" (a new term) if it is "easy" to do (see the regulation quoted below for the exact requirements).  There is no training requirement specified by the regulations, however there may be company specific procedures which require it.

14 CFR 43.3 was updated, and now says (in part):

  (k) Updates of databases in installed avionics meeting the conditions
  of this paragraph are not considered maintenance and may be performed
  by pilots provided:

  (1) The database upload is:

  (i) Initiated from the flight deck;

  (ii) Performed without disassembling the avionics unit; and

  (iii) Performed without the use of tools and/or special equipment.

  (2) The pilot must comply with the certificate holder's procedures or
  the manufacturer's instructions.

  (3) The holder of operating certificates must make available written
  procedures consistent with manufacturer's instructions to the pilot
  that describe how to:

  (i) Perform the database update; and

  (ii) Determine the status of the data upload.


Which country has jurisdiction over incidents in flight?

In my PPL class I was taught a simplified explanation:

If a baby was born (or a crime committed for that matter) on an aircraft, the official country in which it was born depends on wether the aircraft's doors are open or closed (within reasonable limits, so assuming they can't be open in flight).

If the doors are open, the country will be the country where the aircraft is currently located. If the doors are closed, it will be the country in which the aircraft is registered.


Where do LAX commercial cargo planes land/take off?

Large airports like LAX see hundreds of planes departing or arriving every day. They manage traffic flow in the entire area (class Bravo airspace) to optimize their traffic. Cargo aircraft will be treated just like any other aircraft. Which runways are in use for departures and which ones for arrivals, depends on the current winds and preferred configurations of the airport. Due to the high traffic, the airport will not deviate from this configuration to accommodate a single cargo aircraft, which would then be closer to its cargo area. Cargo aircraft will then taxi to their respective cargo areas just like passenger aircraft taxi to their gate on the ground.


For find a value of obstacles height below mentioned in intermediate segment why I should take the IAF MOCA instead of FAF MOCA?

I am not sure if I fully understand your question. This may be the answer. If the Intermediate Segment does not have a published MOCA altitude, and there is no crossing altitude for the Intermediate Fix, you should stay at or above the Initial Segment MOCA. You can only descend when you are given published or explicit ATC instructions to do so.


Are there reference speeds like V1, Vr or V2 for a touch and go procedure?

While for touch and go there isn’t a speed that carries the same guarantees as the takeoff speeds (you will not hit anything nor will you exit the runway on ground at undue speeds), for procedure reasons there are indeed predefined speeds at which to rotate and at which to climb. On the 777, for example, rotation is called at VREF (standard manual approach speed for selected flap setting) on touch and go, and climbout is flown at VREF+15 to VREF+25. .

In any case, the touch and go manoeuvre is only a training manoeuvre and is not in any way considered in performance calculations. Since it’s not calculated, it is also not a manoeuvre for which sufficient runway distance and/or obstacle clearance is assured by either calculation or regulation, neither on all engines nor following an engine failure, other than by flight crews’ experience and prudence. The actual speeds for touch and go are therefore somewhat more arbitrary than on takeoff.

The closest manoeuvres that are considered in performance calculations are a normal takeoff and a go-around from minimums. The relevant speeds for the former you know, for the latter it is the predetermined approach speed.


What is "temporary flight plan" in A320 MCDU?

The temporary flight plan is visible on the mcdu in yellow when you modify the actual flight plan. It will be shown in yellow as well on the ND (for modes ARC, NAV and MAP) until you press the 6R button of the MCDU, which mean * insert.
The goal is to let you see your modification before inserting it in your flight plan. Knowing that most of the time you will create a discontinuity in it and you will have to review and delete the discontinuity.
If you use secondary fplan you will have the information in white.


What happens to a plane that goes to / from an enclave when the surrounding country closes its airspace?

it would be no different than in case say China and Russia both closing their airspace for aircraft flying into and out of Mongolia. There'd be no way for aircraft to enter or leave that country.

Nothing special about being an enclave there.


Does the Autopilot switch to ALT ACQ mode at a fixed altitude difference from target altitude?

The simple answer is that autopilots are designed to fly the aircraft in the same way that a human pilot would.....only more accurately!
If you were climbing/ descending at 3500fpm you’d anticipate the level off earlier than if climbing/descending at 1000fpm or you’d risk exceeding g limits and it wouldn’t be a very smooth transition.
Autopilots, including the 737NG, take into account the ROC/ROD to ensure a smooth transition to level flight so yes ALT ACQ engagement will vary.


What is this device on the nose of a Bombardier Global 6000?

That is the sensor for the aircraft's Enhanced Vision System (EVS) - a combination of a visible low light and infra red video cameras which are combined together via computer into a composite image for display on either the PFDs or HUD in the cockpit.  It provides better situational awareness in poor visibility and during night operations for the crew.  See demonstration video here, and a video for how it can light up high terrain here (frame below):


Why is the relation of height and temperature different when calculating altitude?

The equation is saying, that for every degree difference from standard temperature, the difference between pressure and density altitude grows by 118.8 ft. A completely different factor from the lapse rate.


Why does the B777 have no winglets? Are there any drawbacks to having winglets?

As in anything in aviation design, the use of wingtips has both advantages and disadvantages. In the end, the decision to use (or not) a winglet is based on the cost-benefit analysis of the winglet to be used in that particular aircraft.

All winglets incur a drag and weight penalty- the question is whether they conserve fuel more than they increase it in the first place.
One problem in winglet addition is that they are prone to flutter.
Also, an equal span extension is sometimes more effective and is less risky.
Another thing to add is that most of the present aircraft using winglets (A320s and B737s) were not designed with winglets to begin with. They were retrofits. Most of the new aircraft are designed with plenty of aerodynamic experience and the engineers can take a call based on the data available as to whether to have 'conventional' winglet or not (See A350XWB Vs B787).

Coming to B777, it should be noted that the -300ER, -200LR, and -200F have wingtip devices after all- raked wingtips. These act in the same manner as the winglets to reduce drag.

Boeing 777 raked wingtip; image from Boeing.com

According to Boeing,

  Each wing on the Boeing 777-300ER (extended range) is being extended by 6.5 feet, and raked wingtips are being added to improve the overall aerodynamic efficiency. The raked wingtips help reduce takeoff field length, increase climb performance and reduce fuel burn.

So basically, these act in the same manner as the conventional wingtips. Also, it is crucial to consider the tradeoff. B777 was designed when the advantages of the wingtips were well known, yet they decided to go without one anyway. From airspacemag:

  Because winglets are a tradeoff: In the highly visible case of the 777, an airplane with exceptionally long range, the wings grew so long that folding wingtips were offered to get into tight airport gates.

Finally nobody ordered the folding wingtips when they were first offered, though that has not stopped Boeing from trying. Note that one main reason for offering folding wings is to fit into existing gates- else the wingspan would've become too great.

Boeing considered all the options before deciding to go with this option:

  Dave Akiyama, manager of aerodynamics engineering in Boeing product development, points out that designing winglets can be tricky-they have a tendency to flutter, for example. "We find that it really doesn't matter what kind of wingtip device you use-they're all like span," he says. "The devil is in the details. Span extensions are the easiest and least risky."

And finally, winglets were considered for B777, especially for the earlier versions, though nothing came out of that- so most probably they were of not much use in improving fuel burn. Note that 787 also has a similar 'raked' wingtip instead of winglet.

Note: The fuel burn can be reduced by other means than wingtip devices- Boeing did exactly the same through Performance Improvement Package (PIP) for the Boeing 777, improving fuel burn by 1%:

  ... for long-range 777s, with United, Continental, and Delta investing in
  modifying the outboard aileron droop and the environmental control system, making ram air improvements, and installing smaller wing vortex generators to yield a total of 1 percent fuel burn improvement.


Why aren't there brake lights on aircraft?

They simply aren't necessary.

Brake lights are on road vehicles because often they travel at relatively high speeds, and follow relatively close to one another. If a driver suddenly slows, the brake lights help provide a visual cue (which grabs the attention of other drivers, and is visible from quite a long distance) that the vehicle intends to slow or stop.

In aviation, no aircraft should be traveling on the ground (taxiing) at such a velocity that stopping in a short distance is a problem - nor should they be following another aircraft too closely (regulations/airport rules govern both taxi speed and following distances). Taxiing aircraft are either in communication with an air traffic controller, or each other, making the need for sudden stops, change in speed or direction highly unusual. In addition, there is a higher degree of professionalism within the aviation community than your ordinary automobile driver; pilots pay closer attention to what their and other aircraft are doing; i.e., you won't find a pilot with a Big-Gulp in one hand, a shaving razor in the other, head facing the back seat passengers, all while attempting to pilot the aircraft!

In short, brake lights wouldn't be necessary on road vehicles either under the same conditions - but as it is, they assist in preventing collisions in numerous situations. In aviation, these sorts of collisions do not occur often due to the factors above, and therefore are not necessary.


Is it possible to power an ultralight airplane with a single-cylinder weed-whacker engine?

There are methods of calculating the power required to fly a particular plane.  In your case, assuming that you'll also need to carry ~18 kg of fuel and a pilot (roundly 75 kg), the answer is NO.  A 2 hp (1.5 kw) power plant will be insufficient to give safe takeoff and climb performance -- with the possible exception of a high performance sailplane airframe (some self-launching sailplanes use ridiculously small engines).


Is moving payload masses during flight to restore mass centering, or to avoid having to trim, a useful approach?

While I don't know of any airplanes that move load in flight for CG purposes, there are definitely airplanes that have various fuel tanks that can be used to trim the airplane during flight. Some of these systems will move the CG aft after takeoff for better performance in cruise, and then move the CG forward before landing for a more stable approach and landing.


Does transition to SBAS or GBAS navigation require alignment of the intermediate segment with final segment?

I've never seen an SBAS approach that had more than one intermediate segment. In all cases, the IAF/IF is aligned and more than 2 NM from the FAF. There may be multiple IAFs that feed directly to the IAF/IF. A good example is the PSM RNAV (GPS) RWY 16:

As you can see, ITAWA is aligned with PUDYE.  You can get to ITAWA via SATAN, ITAWT, or directly. Arriving directly at ITAWA requires flying the procedure hold to establish the final approach course.

GBAS (or GLS in the US) is intended as a functional replacement for ILS and as such one of the goals is that GLS mimics the behavior of an ILS. As a result, the GLS procedures are designed to be flown just like an ILS approach.

You can compare the GLS and ILS approaches to Newark Rwy 04L below:

If you compare the two, you'll see the path from the FAF HOWYA to the MAP is identical. The IFs are slightly different as the GLS IF EMBAY is a pure extension of the glide path out to 2800 elevation. The ILS path is slightly different vertically between the IF and FAF due to having to identify the IF via the DME.


Where is a missed approach point for circling while flying ILS?

Circling approaches are non-precision, regardless of how you arrive at the MDA.  When circling you'll level off at the circling MDA and use the missed approach point depicted for the approach.

If you are looking at a Jeppesen approach plate there should be a level-off and 'M' depicted in the profile view.  If you are looking at government plates the level-off and MAP are not depicted in the profile view but are still specified elsewhere.  In any case, you'll fly the localizer to the MAP and then go missed.  You'll descend either via the GS or step down altitudes to the circling  MDA and stay there until either the MAP or you are able to further descend.

RVR probably won't be listed for circling minimums (it isn't published for the chart as a whole) as they will generally be at least 1 mile or more.  Whether the visibility requirement is specified in feet (RVR) or miles, this is the visibility you need to descend out of the circling MDA.  You have the further restriction that you may not descend out of MDA until you are in a position to land.  The same familiar rules in 91.175 still apply.

In summary, fly the approach like you normally would but level off at the non-precision circling MDA and go missed at the non-precision MAP if you have no visual contact with the runway.  You do not go missed exactly upon reaching the MDA, just as you wouldn't if you were flying a VOR or LOC approach.  You go missed at the missed approach point.


Why did water come into USAirways Flight 1549 if an airplane is sealed and pressurized?

Two reasons:

Airplanes are not completely, perfectly hermetically sealed. They are pressurized using positive air pressure from the engine bleed air and packs. If there is a failure in the system, the aircraft internal pressure will return to the outside ambient pressure. Air will escape the aircraft or enter the aircraft if the outside ambient pressure is greater. Water will react the same way. Especially when you have the combined greater pressure of the water and the atmosphere above it.

Combine this with the structural damage caused by the dynamic pressure of the aircraft impacting the water, the aircraft will have ways of water entering the aircraft through burst seams. The structural and hydrodynamic load alone, created by the rapid deceleration of the aircraft will be enough to tear apart the airframe, open sealed doors and bulkheads, and blow out windows.


Can I circle to a different runway if cleared for an instrument approach without circling minimums?

The only minimums that apply to any approach are those printed on the plate. Doing anything else is being a test pilot. Minimums are charted based on obstacle clearance, descent gradient, distance from the airport, and a variety of other factors.

The appropriate course of action is to either:

land straight in on 31 and attempt to deal with the crosswind. This would be preferred, in my opinion.
go missed and pick up the GPS Y 31 approach and circle to 25. You can't switch approaches once you're cleared. Given the ~1 mile visibility and low ceilings, this would not be ideal.
divert to your alternate if neither of those works.

Choosing a build-your-own circle with 600' ceilings is reckless - certainly more so than landing with a ~15-20 knot crosswind. There's no guarantee that you'll remain clear of any surface obstacles.


Can a wide body airliner land safely with a full fuel tank?

Can a wide body airliner land with a full fuel tank?

Yes! But it is safer to land an aircraft below its published MLW.

Wikipedia has the relevant specifications for the B777 and the A330

Using the B777-200 as an example.

Maximum take off weight: 545,000 lb / 247,200 kg
Maximum landing weight: 445,000 lb / 201,840 kg

So this particular aircraft may have to drop roughly 46,000 Kg of weight if taking off at its maximum before it can land safely. That's not to say it's impossible to land without doing so, but it's certainly not advisable.

When an emergency presents itself, what is "advisable" is getting on the ground as quickly as possible, and if that means landing overweight then so be it. There have been plenty of times when an overweight landing has caused no damage - and even if the aircraft is damaged by an overweight emergency landing, that's still often a better outcome for the people on board than would be the case if the aircraft waited to get below its MLW before landing.

However, with that said, just because you are taking off with a full load of fuel it does not imply that you must be at MTOW. You could be taking off with a full load of fuel but no cargo/passengers, in which case it is entirely possible that you may be below MLW. And in which case the answer would be yes, it's entirely possible to land with full fuel tanks.


Was there more than one incident or accident where an Airbus FBW aircraft reverted to mechanical backup?

Sadly yes, there was at least one other flight, XL Airways Flight 888 from 2008 on which the use of the mechanical backup trim wheel might have saved the plane.


In helicopter, the yaw control is usually obtained by adjusting the pitch of the tail rotor, that changes the 'thrust' produced by the tail rotor; this rotates the helicopter about its yaw axis.

Source: cfidarren.com

In case of helicopters without a tail rotor, the yaw control is obtained in different ways. The NOTAR used a method similar to the tail rotor, by varying the thrust. In case of tandem rotors (like Chinook) , the yaw control is obtained by differential lateral cyclic.

Source: tech-mp.com

The quadcopters obtain yaw control by adjsuting the speed of the rotors. In quadcopter, two rotors (say 1 and 3) rotate in one direction, while the other two (2 and 4) move in the other. By slowing down 1 and 3 while speeding up 2 and 4, you can make the quadicopter yaw to the left. The torque of 2 and 4 spinning to the right makes the body spin to the left. Conversely, by slowing down 2 and 4 while speeding up 1 and 3, the quadcopter yaws to the right.

Source: safaribooksonline.com

In case of coaxial helicopters like the Kamon Ka-25, the yaw control is obtained by varying the torques (i.e. by varying the pitch) of both the main rotors simultaneously in opposite direction.

Source: simhq.com

Coaxial helicopters (like Kamov Ka-25) do have movable rudders like aircraft for use in forward flight as it reduces the main rotor adjustment required and is more effective.

Ka-25 rudder, image from travelforaircraft.wordpress.com

The image below shows the control methods used in different types of helicopters.

Image from unicopter.com, credited to Rotary-Wing Aerodynamics.


How do I know my AGL altitude while in flight?

You can't know with 100% accuracy, even radio altimeters have limitations, and if you're flying on a PPL the aircraft probably wouldn't have one anyway. The VFR pilot flies with a map which shows the height of the highest terrain and noteworthy landmarks, but unless you are directly over one of these it is a matter of your experience in judging vertical distances.

I'm not sure if it's different wherever you come from, but where I fly in Australia, all airspace is measured in sea level altitudes or flight levels, never in reference to ground height, so we would never encounter your situation. Trying to stick to one height AGL might sound like a fun challenge to some but to me it sounds like less time to save my life when the engine quits.


It is a wind tee; it serves the same function as a wind sock. It is designed to resemble an airplane from the air so that pilots overflying the field can more easily determine in which direction they should land. The top of the "T" is the front of the airplane and represents the direction in which an airplane should land.

When the wind hits the vertical tail surface it weathervanes. The tail points in the direction that the wind is blowing.

Unlike the wind sock, the wind tee does not provide wind speed information, only wind and landing direction.


How can an helicopter end up with the same tail number than an airplane?

N133AA appeared on an American Airlines DC10, but American Airlines retired, sold or scrapped all their DC10 and MD11 aircraft by 2002, releasing the registrations for other uses.

Wind the clock forward 15 years and somebody has used N133AA for a Robinson R44 helicopter. I speculate that the effective owner of the helicopter is one Agustin Anaya, who submitted the photographs to JetPhotos, even though the aircraft is registered to a company.

The FAA registry shows only the helicopter because the American Airlines usage was released long ago.


Why are thrust reversers not used to slow down to taxi speeds?

A minimum max reverse power speed is often an airplane operating limitation.  It's mostly related to FOD (mostly sand grains and small gravel) and on some designs there may be compressor stall issues due to flow disruptions.

On the CRJ 700 max reverse is limited to 75kt although you can use up to 60% N1 down to zero speed.  On a 900 you have to be at idle below 60kt.

In practice, you start to come off max reverse during the landing roll transition from high energy to low energy (on the RJs, there is a speed call at 90 kts for this).  You come down to idle not too quickly and linger at idle for a second before stowing them; if you just slam the levers down to stow position, the reversers stow while the fan is still producing a lot of energy and you actually get a little kick of acceleration, which feels like you let off the brakes for a moment.

You can use idle reverse, which gives a little bit of braking, while taxiing if the alternative is riding the brakes and overheating them, say like a taxi along a downhill slope or along a slick icy surface where braking is marginal, and you don't want to taxi single engine, and in a pinch you may use reversers to try you save your butt if you start sliding off an icy taxiway with no braking control.


On an energy-maneuverability (E-M) diagram how does the shape of a specific excess power (Ps) curve change as thrust is increased or decreased?

The shape does not change much, but they shift up and down. Below you see a diagram I once made for a HALE unmanned airplane with a turbofan engine. Instead of varying thrust I calculated the instationary turn rate at different sink speeds. Sinking frees up energy similar to a thrust increase, so these curves should look the same for different thrust levels. After all, the unit for SEP is a speed, too.

Turn rate diagram for different sink speeds and flap settings. Blue lines are for cruise and red curves for the landing setting of a simple camber flap. The aerodynamic model did not include wave drag, so the results above Mach 0.7 are not correct.
As you rightly assumed, the curves shift to lower speeds for lower thrust, but only the red ones become flatter for lower sink speeds / thrust levels.


Why do aircraft take this strange route into JFK?

Stormy change of arrival plans

Originally, the flight was planned to use the CAMRN4 STAR coming in from SIE VOR south-southwest of KJFK.  However, there is a strong band of storms just south of that VOR on the FlightAware map, blocking that route.  So, the flight got a reroute to pick up the LENDY6 STAR instead, getting vectored northwesterly to around FQM (Williamsport) VOR first and then back onto the course to pick up the STAR in order to provide sufficient space to descend to FL230 by JENNO.


Can Air Traffic Controllers participate in Q&A?

I am not aware of any legal limitation for air trafic controllers to speak out on a public website, but there could be one.

StuckMic.com is however an ATC forum in which FAA ATCo's seem to participate actively. This leads me to believe that they are allowed to speak out on a public website. There are very likely restrictions on what they can share.


In a pattern, when do you begin your descent from TPA if following another aircraft?

Every CFI I have ever flown with has a different procedure for when to descend. Its annoying. Think of it as descending to the runway when you are in a position to land. If you are not following another aircraft, then you can begin your descent abeam the threshold. If you are following another aircraft, then you should wait to descend until you are in a position to land as #2, which could be after you've already turned base or (long) final.


Could maintenance data be downloaded via ATC facilities?

Not through ATC.  The airlines have "company" frequencies they can use for such data.  Outside of airlines, General Aviation can use FBO frequencies for the same communications.


What are the pro/cons of polyhedral cranked wings?

While dihedral wings offer increased stability in the roll axis, they also decrease the lift that the wings provide. A polyhedral wing provides a compromise: a steep dihedral at the tip of the wing in order to maximize stability, and a shallower dihedral angle closer to the root in order to maximize lift.

Therefore, a polyhedral wing allows the best of both worlds for a wing design. Other applications of a polyhedral wing are utilitarian; the gull wing on the Vaught F4U Corsair is designed so that the landing gear is positioned close to the ground while maintaining roll stability and aerodynamics.


What constrains a paraglider vertically?

To be similar to the constraint produced by a rail, this vertical constraint should be in the order of thousands of kg, IMHO. Any suggestions on how to estimate this amount, and its origins?

The thing is that the constraint is something you "perceived":

  I perceived a very strong vertical constraint

not that was actually there.

Only gravity, lift, and drag (and thrust, if powered) are acting on the paraglider, nothing else.

And the lift is easily estimated, as it is roughly equal to the weight of the passengers and the aircraft summed up and being this a paraglider, definitely not in the range of the thousands of kg.

Having this been your first experience, the sensation can easily be explained by your lack of familiarity with the transportation method.


What are the radius of containment (Rc) and horizontal protection limit (HPL) and how are they related to Type Code?

Mode S ADS-B messages use DF17 or DF18.  The type code field with the DF17/DF18 is set to reflect the current navigation performance.

The Containment Radius (Rc) is the radius that there is a 95% probability the aircraft is within that radius of its stated position, both horizontally and vertically.

HPL is computed by the GNSS and is the theoretical 100% containment (protection) limit in the horizontal only. It is approximately double the value of the Rc. Since HPL is horizontal only, the vertical is mostly addressed by the cases of 1) no altitude, 2) baro altitude or in its absence, 3) the GNSS height.

So based on the presence and value of HPL and altitude data, the appropriate Type Code can be set by referring to the table. The receiver of the message can then determine the transmitter's Rc.


What is the best pair selection algorithm?

When using a DME pair, the location of the receiver can be determined with some accuracy associated.

The time measurement is performed with some uncertainty leading to a slant range that is within a ring area (the double circles).

Observation

When looking at the intersection of the two rings with different positions of the DMEs:

The hatched area must be eliminated using some method
The blue area is reduced when the two DME bearings are at a right angle
As the width of a ring is proportional to the radius (the uncertainty is a percentage of the range), the smallest blue area is obtained with DME at right angle and the closest to the aircraft (last diagram).

Proposed algorithm

Divide the area around the aircraft into, say 8 sectors of 45° (the number of sectors impacts the accuracy but also the number of computations to be done, in an exponential way).

Look for the two closest stations, write down the sector(s) they belong to
Compute the intersection area
Find the next closest station D, note its sector S
If S is a sector already tested, ignore D, return to 3
Else within the already known sectors, find sector SP closest to 90° of S. Get station DC of this sector.
Compute intersection area for pair D-DC
If this area is smaller than the previous smallest area, keep it as new smallest
Repeat from step 3 until all sectors have been tested (one station per sector) or the radius has exceeded some predetermined limit.
Determine the new aircraft position using the best pair found.
Restart at step 1 using the new aircraft position (the time interval before restarting the cycle may be determined from the distance the aircraft moved. If the aircraft hasn't moved, then the next search for a pair is likely to find the same pair).

Example

Step 1: The two closest stations are in sectors S3 and S7 (fig A).
Step 2: Their intersection area is X (fig. A).
Step 3: The next closest is D3 in sector S2 (fig B).
Step 4: S2 has not yet been visited, so let's look at D3.
Step 5: In {S3, S7}, S7 is the sector closest to 90° of S2
Step 6: D3-D6 intersection area is Y (fig. B)
Step 7: Y is smaller than X, so our candidates are now D3-D6

Step 3: The next closest is D5 in sector S5 (fig C).
Step 4: S5 has not yet been visited, so let's look at D5.
Step 5: In {S2, S3, S7}, S3 and S7 are the sector closest to 90° of S5, we chose S3 because D4 is closer than D6.
Step 6: D4-D5 intersection area is Z.
Step 7: Z is smaller than Y, so our candidates are now D4-D5
Step 3: The next closest is D2 in sector S2
Step 4: S2 has already been visited, we ignore D2.
Step 3: The next closest is D1 in sector S1
Step 4: S1 has not yet been visited, so let's look at D1 (fig D).
Step 5: In {S2, S3, S5, S7}, S3 and S7 are the sector closest to 90° of S1, we chose S3 because D4 is closer than D6.
Step 6: D4-D5 intersection area is Z.
Step 7: Z is smaller than Y, so our candidates are now D4-D5
Step 3: The next closest is D1 in sector S1 (fig D).
Step 4: S1 has not yet been visited, so let's look at D1.
Step 5: In {S2, S3, S5, S7}, S3 and S7 are the sector closest to 90° of S1, we chose S3 because D4 is closer than D6.
Step 6: D1-D4 intersection area is T.
Step 7: T is larger than Z, so our candidates still D4-D5
Step 8: Our maximum radius has been reached, our pair is D4-D5


Yes, this is dangerous and must be avoided.

Consider this: Between the low speed range where the aileron works as intended and the high speed range where it works like a Flettner flap there is one speed point where the rolling moments of the aileron and the wing twist cancel each other out. There the aircraft is uncontrollable in roll. No sane pilot would fly such an aircraft voluntarily.

Set the speed at which full aileron deflection produces only a quarter of the rolling moment coefficient as the never exceed speed.


To keep it simple (source for all that follows is Wikipedia - Propfan):

You can think of the contemporary propfan as a turboprop that has two high rpm contra-rotating propellers or fans with six or more highly swept fan blades each. These fans are driven by a turbine engine through a reduction gear or a low-speed free turbine.

High rpm is used to reach higher speeds and altitudes than conventional propellers.

The contra-rotating fan arrangement is used to remove torque effect, and to enhance efficiency (note: some early versions had just one fan).

Fan blades are swept to keep drag minimal at high rpm (high blade airspeed).

This description might very well be considered an oversimplification, but I guess this is what was asked for.


Spoilers have many uses, but first I want to distinguish types of spoilers.  Airplanes will typically have ground spoilers and flight spoilers and they work like they sound.

Ground spoilers only open up on the ground -- these are usually much more detrimental to lift than the flight spoilers.
Flight spoilers open when actuated by the pilots

Another type of spoiler is the spoileron, which is used on some airplanes like an aileron, that is to bank the airplane by destroying lift on one wing.
Since you ask about use in the air, I will focus on flight spoilers.  When would I use flight spoilers?

I want to descend faster
I want to slow down quicker
I want to descend and slow down

I want to descend faster
This can be broken down into three categories

I screwed up and I need to make a crossing restriction
The anti/ice system turned on (more on this below)
I am initiating an emergency descent (abnormal)

The bit about a/ice comes from the fact that on many airplanes when a/ice is on there is a high demand for bleed air.  In the EMB-145 the FADEC bumps up idle thrust quite a bit to meet this demand and if you did not anticipate this in your descent planning, we were authorized to use our spoilers in icing conditions to aid in the descent.  This could be interpreted as an "I screwed up" case, but really isn't in my opinion.
I want to slow down faster
If there is a charted speed restriction, this may be useful.  Particularly if you have just prioritized the descent to meet a crossing restriction and now need to bleed off speed.
You might need to start descending out of 10k feet ASAP, and need to be at 250 kts to do so, and in this case spoilers can be useful.
I want to descend and slow down
In a jet, this can be hard when clean.  Often the choice is descend or slow down.  When you need to do both, spoilers can be a great help.

In the case of landing or rejected takeoff, all of the spoilers (including flight spoilers) should deploy automatically on most airplanes when the thrust levers are moved to idle, there is weight-on-wheels and you are above some threshold speed.
In addition, spoilers are useful in some airplanes for roll control, in addition to airplanes with pure spoileron roll control.  I didn't spend much time on this topic as like the ground spoilers in landing and RTO, these are passive from a pilot point of view -- you aren't specifically controlling these spoilers, the flight control system is doing it for you.  In any case, the spoilers used for roll control are quite important during flight.
As you can see, spoilers have many uses in flight and not just for landing.


What is the meaning of this airport marking?

The marking indicates that vehicles must yield to aircraft. It is placed in areas where a service road crosses a taxiway.


How the maximum service interval is related to UAVs?

Service interval  - is a maintenance term indicating the interval (either in time or number of flight cycles) between two successive services (e.g. inspection, change of oil, etc.) that a component requires.

In case of UAVs this is not different. It can be for example that the Service Interval of the engine is 100 hours of flight time, meaning that the UAV can fly missions for 100 Hours between engine maintenaince services.


Between land and sea, which route is preferred?

At the cruising altitude of most airliners, there is no noticeable aerodynamic difference between being over land or over sea. At lower levels, being over sea would typically offer less turbulence, in part because as the ground warms you can encounter rising air thermals.

Generally, airliners fly whatever route provides the shortest time, which is not always the shortest distance, often called the Great Circle route. The GC route is not always quickest because of jetstream winds.

One thing to consider when choosing between an over-land or over-sea route is the distance to another airport should an engine fail. You might have heard of ETOPS. Basically, twin engined aircraft must fly within a certain distance of a suitable landing site - often 2 or 3 hours of flying time on one engine. In the middle of the ocean the quickest route may take the aircraft outside of this range, so it will have to fly closer to land, or even in certain remote parts of the world, still over land.

Another consideration is life rafts. They are legally required when flying more than 25 miles (if I recall correctly) out to sea. Life rafts add weight and therefore cost so some airlines have actually removed life rafts from their aircraft, or at least only have a few of their jets allocated for flights over water.


What is the diameter of a Trent 900 engine?


Can one become a CFI with a sport license?

Yes.

FAR 61.403.

  To be eligible for a flight instructor certificate with a sport pilot rating you must:

    (a) Be at least 18 years old.

    (b) Be able to read, speak, write, and understand English. If you cannot read, speak, write, and understand English because of medical reasons, the FAA may place limits on your certificate as are necessary for the safe operation of light-sport aircraft.

    (c) Hold at least a sport pilot certificate with category and class ratings or privileges, as applicable, that are appropriate to the flight instructor privileges sought.

A CFI never needs a medical certificate.  It is not required for the operation of that certificate.

A medical certificate may be required if the CFI has additional roles.  For example, the CFI also is acting as the legal pilot in command.  A sport pilot acting as the legal pilot in command does not need a medical.

FAR 61.23(b)

  (b) Operations not requiring a medical certificate. A person is not required to hold a medical certificate—

    (1) When exercising the privileges of a student pilot certificate while seeking—

      (i) A sport pilot certificate with glider or balloon privileges; or

      (ii) A pilot certificate with a glider category rating or balloon class rating;

    (2) When exercising the privileges of a sport pilot certificate with privileges in a glider or balloon;

    (3) When exercising the privileges of a pilot certificate with a glider category rating or balloon class rating in a glider or a balloon, as appropriate;

    (4) When exercising the privileges of a flight instructor certificate with—

      (i) A sport pilot rating in a glider or balloon; or

      (ii) A glider category rating;

    (5) When exercising the privileges of a flight instructor certificate if the person is not acting as  pilot in command or serving as a required pilot flight crewmember;

    (6) When exercising the privileges of a ground instructor certificate;

To answer your questions.  A sport pilot or CFI will never need a medical because the operation does not require a medical but a valid driver's license.

A glider pilot or CFI never needs a medical or drivers license, if I am reading the regulation correctly.

A sport CFI does not require a CPL as does a regular CFI. The CPL requirement is found under part 61 subpart H

  Subpart H—Flight Instructors Other than Flight Instructors With a Sport Pilot Rating

    §61.183   Eligibility requirements.
    To be eligible for a flight instructor certificate or rating a person must:

      (c) Hold either a commercial pilot certificate or airline transport pilot certificate with:

But subpart H specifies Other than Flight Instructors With a Sport Pilot Rating. The rules for sport CFI are found in subpart K where no such requirement is found. (see 61.403 above)

It does not relieve the pilot or CFI from adhering to FAR §61.53 Prohibition on operations during medical deficiency though.


Light aircraft elevator/aileron/direction not working

If a major flight control surface fails in flight, you'll be lucky if the ballistic parachute can save you.  An aileron, for instance, that goes "hard over", will put even the most docile training aircraft into a tight spiral or a roll that will quickly become a spin (because the airplane doesn't have enough speed for a complete roll and will stall).  A stuck elevator could result in anything from a stall to a steep dive.
In this situation, immediate deployment of a ballistic parachute might prevent fatalities; waiting will not.  Delay will allow airspeed to build, G forces on the pilot to increase (presuming a spiral or spin), and potentially the wings come off due to flutter or G forces after passing Vne -- not to mention likely exceeding the parachute's maximum deployment safety margin.
Fortunately, this kind of failure is exceedingly rare, absent the kind of damage that comes from air combat, ground impact, or extreme weather phenomena.


Which version of the FAA's Instrument Procedures Handbook is current?

8083-16 ,dated 2014, is current version, superseded 8261-1A. It is stated in Summary of Change.

For future reference, the FAA page you linked in the question is best resource available.


Why are the aerodynamic characteristics of a finite wing different from the properties of its airfoil section?

Because the wing is finite, while the airfoil is assumed to stretch out sideways indefinitely. The consequence is that on a wing you get spanwise flow outside of the plane of symmetry, while on the airfoil all flow speeds are in the airfoil's plane only.

Spanwise flow is caused by the pressure difference between lower and upper side which can equalise around the wingtips. This lets the pressure difference diminish towards the tips and especially in the rear part of the wingtips. The consequences are:

Lift is smaller on a "real" wing relative to a wing of the same airfoil with no such sideways flow.
The center of pressure of a "real" wing is ahead of the one of the airfoil.
On a swept wing the air transverses the surface differently than it transverses the airfoil. Basically, a sideways speed component is added to the speed around the airfoil.


How can multiple airplanes prevent simultaneous communication between ATC?

As you fly more you will get to know the flow of radio transmissions and be able to identify when another exchange has completed. This comes with time and needs to be learned over time, it may be beneficial to listen into things like liveATC in your spare time to get comfortable. The FAA has a nice little brief on it here with some good pointers:

  Listen before you transmit. Many times can get the information you want through ATIS or by monitoring the frequency. Except for a few
  situations where some frequency overlap occurs, if you hear someone
  else talking, attempting to transmit will be futile. You will probably
  jam ("step on") someone else's attempt to transmit, causing a need to
  repeat the call. If you have just changed frequencies, first pause and
  listen to make sure the frequency is clear.

  Think before keying your transmitter. Know what you want to say and, if it is lengthy, (e.g., a flight plan or IFR position report),
  jot it down so you do not waste transmission time trying to remember
  what you need to say.

A solid 1-3 second pause should ensure the channel is free for you to transmit. The nature of transmissions is to keep them short and to the point, even on a busy frequency you will have plenty of time get in what you need and get a response.

As for the multiple transmissions at once, you will know! When two people attempt to transmit at the same time a nasty noise occurs. This is addressed here.


I would like to know where ideally it is to be sat on an Emirates A380 to get a nice picture of the wing and wingtip as well as the outer landscape?

The best seats would probably be in the back because you can see the wing and the ground without having to twist or having the wing in your view.

Here is a picture I took from the back end of a Boeing 757-200. Is it the view that you want?


How is collision avoidance regulated in controlled airspace in Canada?

You are correct, it applies when operating in the vicinity of an aerodrome:

  Division V — Operations at or in the Vicinity of an Aerodrome

  602.96 (1) This section applies to persons operating VFR or IFR aircraft at or in the vicinity of an uncontrolled or controlled aerodrome.

  (3) The pilot-in-command of an aircraft operating at or in the vicinity of an aerodrome shall

    (a) observe aerodrome traffic for the purpose of avoiding a collision;

Also this part:

  Part VI — General Operating and Flight Rules

  602.19 (1) Notwithstanding any other provision of this section,

    (a) the pilot-in-command of an aircraft that has the right of way shall, if there is any risk of collision, take such action as is necessary to avoid collision; and

    (b) where the pilot-in-command of an aircraft is aware that another aircraft is in an emergency situation, the pilot-in-command shall give way to that other aircraft.

The way I'd interpret the above is vigilance in see-and-avoid is always there, unless of course you don't have ACAS and TAWS and flying IFR in instrument meteorological conditions (IMC).


What are effective ways to spot the aircraft ATC specified?

(Daytime flying only. Peripheral and night vision is different and I have zero practice of night flying.)

The highest resolution part of the eye is the fovea, and it's surprisingly narrow. If a small, slow-moving object is outside this area it probably won't be seen. If you scan from say 20 degrees left of an object to 20 degrees right of it you will also miss, because the eye tends to jump in steps and we only see a small fraction of what is actually in front of us.

So I was always told to gaze steadily, in ten degree steps, for a few seconds at each area. A grid of search areas both above and below the horizon should be checked. You'll only recognise an object when your fovea is virtually on it.

Only look for a second or two at each are because any longer and the vision "bleaches" and you are even less likely to recognise anything in that region; just keep moving on to the next.
The narrow 10 degree steps are that size because that's the region
of acceptably sharp vision. (I suspect it differs between individuals)
This was what I was taught for general lookout, though I suppose it should apply to a specific search area given by ATC too.

Apparently these tips were all derived from RAF training for this sort of thing, but I don't have any notes on that.  In any case I suspect it's more practice than bookwork anyway.

One of my gliding instructors liked the spotting game. One point for every aircraft I spot before him. He had one dodgy eye and of course still won by an appalling margin... (I've also heard some play this game for beers, though frankly none of my instructors would ever be able to drive home.)


Do all passenger aircraft have a nickel cadmium battery?

No, they don't.  At least, not for propulsion.

Jet engines burn oil and can't be powered by batteries.
Even if we forget that, jet engines produce enormous amounts of power and no battery technology can store anything close to that much. Certainly not NiCad, which isn't even suitable for powering your phone or laptop.
Airliners are only allowed to operate on routes where, if one engine fails, the plane can still reach an airport with plenty of safety margin. A second engine failing independently is so unlikely that I wouldn't be surprised if it had never happened on a modern plane.
Even if the second engine fails, airliners can still glide for tens of miles to find somewhere to land (e.g., the Gimli Glider and Air Transat flight 236).
In reality, the only way that all your engines are going to fail is if there's a common cause. Running out of fuel is the most obvious, and is in the news at the moment. The other one that comes up from time to time is flying through volcanic ash clouds. The solution to all of these problems is management, not technology. Airlines are very careful to put enough fuel on board for every flight, and regulations require there to be not just enough fuel to reach the destination but also extra to allow for delays and diversions. Likewise, they're very careful not to fly their planes through conditions that will break them.  Another possible common cause is a bird strike, though it's unusual for that to affect more than one engine. However, bird strikes almost always happen close to the ground and it's usually possible to get back to the airport.

So, even if batteries for backup propulsion were possible (which they aren't), they wouldn't be useful. They'd be required on such a minuscule number of flights (surely less than one in a million) that you'd probably kill and injure more people with battery fires than you'd rescue from engine failures.

And that's before you consider the huge amounts of extra weight you'd have to carry around in the form of batteries and electric engines.  Extra weight means you need more power, need to burn more fuel and have less space for passengers and cargo.

Note that planes do carry batteries to power some electrical systems. They also have a thing called a ram air turbine (RAT), which is a little windmill that drops down and provides power for the electrical and hydraulic systems in case of engine failure.


What is lifting force of V-22 Osprey? Is any other than the two rotors?

The lift is provided by the rotors only. The rotors are powered by Rolls-Royce T406 engines, which are turboshafts: all useful generated turbine power is converted into shaft power for the rotors. Note that turboprops do convert some of the exhaust energy directly into propulsion thrust, turboshafts do not.

All helicopters can provide enough rotor thrust to lift their own weight plus that of (internal or external) payload. Wikipedia lists the max. VTOL weight as 23,859 kg, about the same as the CH-47 Chinook double rotor helicopter at 22,680 kg. The Chinook rotors are indeed longer and therefore require less power to generate the same amount of thrust: 4,590 kW for the V-22, 3,529 kW for the Chinook.


Why do carburetors tend to produce richer mixture at higher altitude?

The simple reason is that high altitude changes the density of air, but not the density of fuel.

Most simple carburetors use a simple venturi design that mixes air and fuel by VOLUME.

But, the correct air/fuel mixture must be based on MASS, not Volume.

If the air/fuel Volume is correct at sea level, it will be too rich at altitude. This is because a given volume of air will have less Mass at high altitude, while a given volume of fuel will have the same Mass at high altitude.

Aircraft carburetors have a mixture control to "lean" the volume of fuel to the volume of air, and are then able to maintain the correct air/fuel ratio at all altitudes.


What materials make up most of the weight of an aircraft?

Besides aluminum alloys, most of an airplane's weight is steel, titanium, and composites. Here is a chart comparing the 747 and 777 structural weight, with a breakdown typical for similar airliners:

Source

Steel is used in components where strength or part life is most important, like landing gear and other important structural elements, as well as many fasteners. Titanium is used where weight and high temperature are important, such as around the engines. Composites are traditionally used for many less-structural applications such as panels and fairings, but may also be used in the empennage (tail surfaces) or on the interior as floor beams. Other materials will include alloys like nickel, as well as specialty materials like rubber, plastic, and fabric, which are used mostly in the cabin.

New aircraft like the 787 and A350 use composites much more extensively, replacing much of the aluminum. Titanium is also used more in these aircraft because it does not tend to corrode in contact with carbon fiber composite like aluminum does.

Source

Federico pointed out that the two graphics differ in the amount of aluminum on the 777 (70% on the first vs. 50% on the second), because the first chart shows only structural weight, while the second is overall.


An APU lacks the critical component that produces thrust, a propelling nozzle.

  A propelling nozzle converts a gas turbine or gas generator into a jet engine.

and

  Most modern passenger and military aircraft are powered by gas turbine engines, which are also called jet engines. There are several different types of gas turbine engines, but all turbine engines have some parts in common. All gas turbine engines have a nozzle to produce thrust, to conduct the exhaust gases back to the free stream, and to set the mass flow rate through the engine. The nozzle sits downstream of the power turbine. (NASA)

Would it be enough to keep flying an airplane if the main engines went out?

It would, in the sense that it will provide electrical and pneumatic power for the different aircraft systems, but no thrust. Or airplanes would have just been built with a few of those tiny APUs. :)

Another alternative for backup systems power when airborne is the Ram Air Turbine.

RE comment about turboprops having some exhaust thrust, they also have nozzles, which an APU still lacks. (NASA)

  Before entering the nozzle (...) the exhaust velocity of the core is low and contributes little thrust because most of the energy of the core exhaust has gone into turning the drive shaft.


Is there a standard term for "3D groundspeed"?

The former is correct; an F-16 climing straight up has 0 groundspeed.
"Inertial velocity" would accurately describe the 3D motion you're describing.


What is this in the primary flight Display?

It is a digital Angle of Attack Indicator. From the Boeing 737 FCOM:

  Digital AOA Readout (white)

  Indicates digital AOA value to the nearest 0.2 degrees. When on the ground and
  ground speed less than 80 knots, the readout is fixed at 0.0 degrees.
  Stick Shaker Indicator (red)

  Indicates point at which stick shaker activation occurs for existing flight
  conditions.
  Blank if AOA signal is invalid.
  Analog Needle (white)

  Indicates analog AOA value.

  needle travel is limited to a range of -6 degrees and +21 degrees
  fixed at 0.0 degrees when on the ground and ground speed is less than 80
  knots.

  Approach Reference Band (green)

  Indicates appropriate range of approach AOA for a Vref(xx) + 5 approach.

  displayed when in normal or single engine landing flaps (15, 30, 40)
  moves with flap position
  inhibited on takeoff and initial climb.

  Zero Degree Reference Line (white)

  Indicates zero degrees angle of attack. Reference lines are displayed every 5
  degrees from -5 degrees to +20 degrees.

(Boeing 737 NG FCOMv2 10.11.11 Flight Instruments, Displays - PFD/ND - Displays)

All Boeing aircraft have at least two alpha vanes to measure angle of attack, but the cockpit display shown above is an airline option, i.e. not every aircraft will display this dial:

  Angle–of–Attack

  There are two alpha vanes, one located on each side of the forward fuselage. The
  vanes measure airplane angle–of–attack relative to the air mass.

  [Option - Angle of attack indicator]

  The primary source of data for the AOA indicator on the PFD is supplied by the
  ADIRU, with the Stall Management Yaw Damper (SMYD) as the backup source.
  The source selection is automatic in the event of primary source failure. Slight
  differences between the Captain’s and FO’s indications may be noticed due to
  sideslip or vane installation errors. These differences could be as large as 2
  degrees alpha.


Are you allowed to do your entire PPL on a medium-sized jet aircraft from day one?

It will not work in EASA for a variety of reasons. Of the top of my head:

Like Lnafziger mentioned, you will need to do at least 10 hours solo. Most jet engines (but the smallest such as the D-Jet) have a minimum required crew of two. Also, you are not allowed to switch airplanes in the PPL course (ie. fly solo with one airplane and dual with another see FCL.235) so you are stuck.
Most jet aircraft (and as far as I know all commercial ones) are multi-engine. You will need 70 hours PIC before you can receive instruction on multi-engine, and you cannot fly PIC before you have your PPL.
Multi-engine jet aircraft require a type rating, which has a lot of license pre-requisites before you are even allowed to enter the cabin: MCC, IR, MEP(land)

There are a few prerequisites specified in  Part-FCL about getting your first class or type rating, and to accomplish most of them you will need to have at least a PPL (eg IR(A), ATPL theory tests, hours PIC ,etc)

FCL.235 Skill test
(b) An applicant for the skill test shall have received flight instruction on the same
class or type of aircraft, or a group of balloons to be used for the skill test.
FCL.720.A Experience requirements and prerequisites for the issue of
class or type ratings — aeroplanes
Unless otherwise determined in the
operational suitability data established in accordance with Part-21,
an applicant for a  class or type rating shall comply with the
following experience requirements and prerequisites for the issue of
the relevant  rating:
(a) Single-pilot multi-engine aeroplanes. An
applicant for a first class or type rating on a single-pilot
multi-engine  aeroplane shall have completed at least 70 hours as PIC
on aeroplanes.
(b) Single-pilot high performance non-complex aeroplanes. Before starting flight training, > an applicant for a first class or
type rating for a single-pilot aeroplane classified as a high performance aeroplane shall:
(1) have at least 200 hours of total flying experience, of which 70 hours as PIC on aeroplanes; and
[...]
(c) Single-pilot high performance complex aeroplanes.
Applicants for the issue of a first type rating for a complex single-
pilot aeroplane classified as a high performance aeroplane shall, in
addition to meeting the requirements of (b), have  fulfilled the
requirements for a multi-engine IR(A), as established in Subpart G.
[...]
(d) Multi-pilot aeroplanes [...] or comply with the following
requirements:
(1) have at least 70 hours of flight experience as PIC
on aeroplanes;
(2) hold a multi-engine IR(A);
(3) have passed the
ATPL(A) theoretical knowledge examinations in accordance with this
Part; and  [...]


What is this thing sticking out in front of wings?

You're correct. That is the pitot tube (head), placed  there so that it is in undisturbed airflow. This location of pitot tube is found in othe aircraft too, like the Messerschmitt  Bf 109 G-2  as shown below.

By Unknown - http://www.militaryimages.net/photopost/showphoto.php/photo/8212., Public Domain, https://commons.wikimedia.org/w/index.php?curid=2278317


What's the relationship between AOA and airspeed?

"Can we get into a stall without reaching the critical AOA?" -- no.
"We know that any aircraft will stall at its stall speed (for a specific weight, CG position, etc.)"-- we need to add "G-loading" to this list of parameters.  The "stall speed" we usually talk about is the 1-G stall speed.  Change the weight or the G-loading, and the airspeed correlating to the stall angle-of-attack changes.
"On the other hand, I know that the critical AOA doesn't change with weight"-- correct, but for a given G-loading, such as 1 G, the airspeed correlating to that critical AOA scales according to the square root of the weight.
"What's exactly the relationship between AOA and IAS?" -- if we know the IAS where the wing reaches the stall AOA at some given weight and G-loading, then we can adjust that IAS for some other condition by multiplying by the square root of the change in weight times the square root of the change in G-loading.  "Change in" meaning the ratio, i.e. new divided by initial.
The fundamental relationship between AOA and IAS is that net lift force at any given AOA is proportional to airspeed (IAS) squared.
Here's an extra complication that you may not want to worry about right now -- the "dynamic stall" -- What is the immediate cause of stall? -- scroll down to last paragraph.


FAR 91.215 (b)(3)(ii) -- transponders-- does the "or below 10,000' MSL" clause have any practical significance?

The answers to the questions appear to be "yes", "yes", and "no".  Neither FAR 91.215(b)(2) nor FAR 91.215(b)(4) have any effect above 10,000' MSL.
The "or below 10,000' MSL" clause in 91.215(b)(3)(ii) has no effect on anything at all and does not prevent an aircraft with no electrical system from operating above Class B or Class C airspace as long as it is above 10,000' MSL.
This is clarified in this 2006 interpretation from the FAA Office of the Chief Counsel.
It possible that the original intent of FAR 91.215 was to prohibit aircraft without electrical systems and transponders from flying above 10,000 MSL above any Class B or C airspace that lies within a Mode C veil; if so the regulations were inadvertently written in a way that did not accomplish this.  This has been rectified in FAR 91.225, pertaining to where aircraft without electrical systems and without ADS-B-out will be able to fly starting January 1, 2020-- these aircraft will no longer be able to overfly ANY Class B or C airspace, regardless of altitude and regardless of whether or not the airspace lies in a mode C veil -- see related question What additional airspace will be off-limits to an a/c w/ no elect. system or xponder under 91.225 (ADS-B) compared to under 91.215?


When pilots check in with a different controller, how to reference flight level?

The word 'maintaining' is used, not 'level'. Using your example it would be:

(ATC Facility) Baron X5XS level maintaining FL 250.

The pilot can say maintaining if they're expecting higher/lower, otherwise omit maintaining altogether:

(ATC Facility) Baron X5XS FL 250.

If climbing/descending:

(ATC Facility) Baron X5XS climbing/descending FL 100.

On the first contact with a radar service, for example going from tower to departure, the SID and passing altitude are also mentioned:

(ATC Facility) Baron X5XS on the STACK 1C passing 2300 for FL 60.

In a busy environment you may be asked to 'report call sign only', in this case:

(ATC Facility) Baron X5XS

Local guidelines should also be used if different. I couldn't find examples in ICAO Annex 10 and Doc 4444, but clear examples are in the UK's Radiotelephony Manual (click image below to view).


Why do some airplanes allow separate right and left rudder pedal adjustment?

As with any question along these lines—"Why did the designers do X"—a definitive answer is very difficult absent specific documentation, which is rare.

I am not familiar with the Dornier 228, but I am familiar with the King Air B200, which is a very similar class of aircraft. Beechcraft also designed the King Air with individual pedal adjustment.

In my examination of that system, I believe the primary reason is simplicity: the individual adjustment system on each pedal is simple and lightweight, whereas a system to adjust both pedals simultaneously would likely be heavier and more complex. Weight and complexity are both undesirable characteristics in aircraft design.

See this excerpt from the King Air B200 Illustrated Parts Catalogue (IPC) depicting the left hand side rudder pedal assemblies:

Source: KA B200 IPC 27-20-00-06

I have highlighted the rudder pedal adjustment lever assemblies—B and C—in light blue. I have highlighted the adjustment pin—No. 375—in green. (Note that the IPC incorrectly depicts the two adjustment levers in reversed locations; see the aircraft photo below.)

The figure clearly shows the simplicity of the design and the way the adjustment relates to the overall rudder pedal control system. The adjustment lever is a simple assembly of stamped metal and hardware, light and cheap to manufacture. The system is simple and intuitive to use and requires little or no rigging.

This is a photo of the left hand side rudder pedal assembly in an actual King Air B200; adjustment is accomplished by depressing the lever with the outer edge of one's shoe and moving the pedal forward or aft:

Any design allowing simultaneous dual adjustment through a single adjustment action would likely have resulted in some combination of increased complexity, expense, weight, or maintenance requirements.

Moreover the system, as designed, allows for separate adjustment, which could be helpful for some individuals or situations.


Is aerodynamics study compulsory for building a plane?

You don't need to know much aerodynamics to build a plane if you follow plans for an existing design that somebody else has engineered and validated, and you don't make any modifications.

If you are trying to design and build something new, even if superficially similar to existing aircraft, then yes you will need to study aerodynamics and other aspects of aeronautical engineering. This doesn't necessarily need to be formal academic study but there is a substantial body of knowledge that you will have to learn in order for your project to be safe and successful.


How much maintenance time did it take to make an F4U Corsair ready for another flight?

Far more than that. Try 50 maintenance hours per flight hour.

  actually finding a reliable source on-line has proven to be a bit difficult. RNZAF, pacific maintenance 58 man hours per flying hour. NZ based (training) F4u 50.5 man hours per flying hour. P51s NZ based (conversion and training) 36 man hours per flight hour.

Piston engines (esp. WW2-era high-performance fighter engines) are very maintenance-intensive compared to jets.

Here's a comparison of various military aircraft types:

Saab Draken.- 50 to 1
Eurofighter....- 9 to 1
F-14............. - 24 to 1
F-18E/F........- 6 to 1
F-18E/F........- 15 to 1 (different source)
Saab Gripen..- 10 to 1

C-17.............- 20 to 1
F-15A/B........- 32.3
F-15C/D........- 22.1
F-16A...........- 19.2
F-117...........- 150
F-117...........- 45 (after improvements, post 1989)
CH-46E........- 19.6 in 1995 GlobalSecurity.org
CH-46E........- 27.2 in 2000
CH-53D........- 24.8 in 1995
CH-53D........- 27.9 in 2000
F-20.............- 5.6
A-6E............- 51.9
F/A-18C.......- 19.1
B-2..............- 124

and you can see modern fighters require far less maintenance hours/flight hour due to several factors:

improved systems that require less frequent maintenance
design improvements to make maintenance take less time (better access, more line-replaceable units)


Does an aircraft landing on a carrier increase the carrier weight before it touches down?

No. Weight is defined as the effect of gravity on a body. Until the aircraft becomes part of the body of the carrier, it has no effect on the weight of the carrier.

I think you are confusing force with weight. For example, if wind shear drives wind against the top deck, this does not make the carrier have more weight, but it does cause the carrier to move down. Likewise any gust from an aircraft may apply a force to the carrier, but does not increase its weight. You might consider that force to increase the "apparent weight" of the carrier, but it cannot be said to increase the weight of the carrier itself.

Note also that the downward wind force of a landing fighter is relatively slight. For example, a person can easily walk under rotating helicopter blades and still stand up and walk. The force is probably only around 1-2 pounds per square inch, maybe 5,000-15,000 pounds total. For an aircraft it will be even less.


Does the wifi uplink antenna affect aerodynamics or efficiency?

Any kind of antenna like that is creating an increase in the flat plate area of the aircraft and thus increasing the parasite drag on the airplane.  Fortunately newer antenna designs, such as the KU/KA band satellite internet systems can be arranged in a manner which greatly reduces the frontal area of the antenna.

The ideal solution, which will inevitably come about on future airliners as these systems increase in popularity with the travelling public, is the creation of an integral compartment on the dorsal side of the fuselage aft of the rear pressure bulkhead and fitted with a dielectric which is flush with the aerodynamic envelope, thereby eliminating parasite and interference drag as well as affecting airflow over the vertical fin.  However for earlier aircraft or those currently in service, this is not going to be possible for several reasons.

First, an installation like that would require major modifications to aircraft structure and pressure vessel of the fuselage and cost big, big bucks in order to get an STC or approval from the airline's engineering department.  Current designs are arranged to as they are to be minimally invasive; all that's required for a typical installation is the attachment of a series of brackets and longerons to the cabin frames which can then be attached to brackets outside of the aerodynamic envelope with a minimum series of fasteners penetrating the fuselage.  This arrangement is preferred by the airlines as their engineering departments and the FAA or other regulatory authority can sign off on the installs without requiring the OEM's involvement.

Secondly, many jets are not owned by the airlines themselves but are leased from financial brokerage firms and any kind of system which minimizes alterations to the airframe is preferable to major - and irreversible - alterations to the aircraft.

As for the economics of these systems, even if you did have an increase in fuel burn by 0.1% you could easily compensate for the loss if installed on a large enough aircraft.  Let's assume on a 747-400 flight from LAX to Narita Intl in Tokyo, you will typically burn about 290,000 lbs or about 44,000 gal of JET-A.  A 0.1% increase results in a mere 44 gal difference in fuel consumption at about $220.00 if you price the fuel at 5 USD/gal.  For a long haul fight like that, lets say that 25% of the passengers use this service at a cost of 44.00 USD each.  With a typ. 747 seating of 440 people, that's 100 passengers buying WiFi service totaling 4,400 USD in income for the carrier.  It's well worth it for them!


Why is a plane escorted while in technical difficulties?

It's not a common thing, as aircraft have technical problems every day without a jet escort. Generally only extraordinary circumstances would merit it.

In this case, the pilots were struggling with an uncontrollable aircraft as well as difficulty navigating - there was lots of bad weather about, and they repeatedly asked for directions to the ocean to ditch, indicating that they didn't know where west was. The jets were scrambled and were available to help the pilots navigate through the bad weather and towards a safe airfield (I don't know if the navigation systems were malfunctioning or if the crew were just understandably overloaded). Fortunately the pilots were able to get the aircraft under some control, I think before the jets even did anything (but more information might come out soon).

Fighter jets can also help check for damage - being better trained and more maneuverable that a civilian craft allows a closer inspection. An underrated benefit is by just being up there with them, panicked pilots can calm down and focus on the task at hand.

Finally there is the horrible option of shooting the jet down if it has been hijacked. This would absolutely be a last resort though, and it's possible that these fighters weren't even carrying weapons.


The ILS, or precisely the components localizer and glidepath antennas can be shut off, as they are electronic devices that emit radio signals. They can be turned off and on by ATC where required, e.g. having the same ILS frequency for two opposite runways and you only want one to be active at the same time or they can be shut down by maintenance directly at the emitters. ILS are usually not powered by UPS, so they will not be available during power outages.

If equipment is being shut down for maintenance or other reasons, you will see this mentioned in the NOTAM, such as here from Cologne/Bonn Airport, where the glidepath portion of the ILS runway 24 is out of service:

A4932/15 - ILS GP RWY 24 OUT OF SERVICE. 01 OCT 00:00 2015 UNTIL 30 DEC 00:00 2015 ESTIMATED.
CREATED: 27 AUG 13:34 2015

(Source: NOTAM EDDK)


Why don't all commercial aircraft transmit GPS data in real time?

Most commercial aircraft transmit their GPS-based position twice per second. This is part of their Automatic Dependent Surveillance – Broadcast (ADS–B) broadcasts. The problem with providing world-wide receiver coverage for this system is that the frequency it uses only travels line via line of sight, so it won't travel past the horizon.

Providing coverage over large bodies of water would require a network of buoys, which would be quite expensive.

Another possibility is to put ADS-B receivers on satellites. This concept has been developed by (Aireon) on the Iridium Next satellite constellation. The system (66 satellites + 9 spares) became operational in 2019 and provides global coverage.


Why is the MiG-23 landing gear nontraditional?

This configuration for the main landing gear was necessitated by the fact that the MiG-23/27's narrow fuselage combined with limited internal real estate in that section of the airframe made that type of retraction mechanism the best compromise in terms of fit, weight and providing a wide wheel track for the aircraft to facilitate operations on rough or unpaved airstrips (typical Soviet utilitarian philosophy for going to war).

An angled MLG strut which retracted forward such as that found on the F-104 or F-16 airplanes was not possible due to the side fuel tanks just aft of the engine inlets.

Aircraft which have narrow fuselages and high mounted wings are always going to require a more unorthodox retraction configuration for the main landing gear due to space limitations.  Other examples of this include the Dassault Mirage F1, Su-24 Fencer, and SEPECAT Jaguar.

This placement of the MLG and in this retraction configuration was the best available for the design limits.


What are the names of the vehicles to provide assistance to aircraft during the turnaround?

The most common vehicle seen is the tug.

source

source

Tugs are multipurpose tractors that are used to tow around all sorts of things.

Several types of equipment are shown in this diagram:

source

The tow vehicle at the nose is more commonly referred to as a pushback tug. They come in different sizes. Here is an example:

source

The GPU is most often a unit that is towed behind a tug.

source

Belt loaders usually can be driven on their own:

source

The wide loader is used to put cargo containers in the hold:

source

The cabin cleaning truck and galley service truck often have a lift built in:

source

Luggage can be brought in baggage carts

source

or in cargo containers which are brought to the aircraft on dollies

source

Another vehicle often seen is the people mover:

source


How is flight planning performed with short turnaround times?

The main reason why turnaround times can be that short is that pilots brief all flights of the day in the morning before the first flight.
This briefing is typically done in the crew room at the airport where the pilots are based. It typically starts about an hour or more before the first flight since there is a lot to cover:

Routes: the flight routes for all flights would already be planned by the dispatch department by this time. They are also filed with ATC by dispatch, so the flight crew only has to review it. This review involves discussing terrain and other possible threats as well as possible diversion airports in case of problems.

Fuel: the required fuel calculation is also done by dispatch, but the final amount of fuel to take is at the captains discretion, so the pilots would discuss possible reasons for taking more fuel (e.g. weather, expected delays at busy airports).
The final weight and balance is only known once the gate closes since passengers might not show up for a flight or additional passengers are booked onto the flight, which is not yet known in the morning. So this will be done during the turnaround.

Weather: the briefing package will contain the METAR (current weather) and TAF (forecast weather) for all airports visited during the day and all possible diversion airports. The crew will carefully review the expected weather at the expected times spent at each airport. The prevailing wind direction typically dictates which runways are in use for takeoff and landing. The crew would discuss which departure and arrival procedures they expect at each airport.
The crew will also discuss en-route weather, like e.g. thunderstorms (might require deviating from the planned route) or expected clear air turbulence (so they can brief the cabin crew about this).

Aircraft: since an aircraft can be dispatched with some items inoperative (Minimum Equipment List), the crew will review the information about the aircraft they are about to fly. This means they are aware of any missing or inoperative items and their consequences. Some airlines also have aircraft with different equipment or engines installed (e.g. A320ceo and A320neo) and the crew will brief the differences in operation (if any).

NOTAMs: these notices to airmen contain important information about the current situation at airports or for specific airspaces. This could be an airspace closed during a special event, it could be a taxiway closed for maintenance, it could be an unavailable approach because some equipment is broken, etc. The crew will go through all NOTAMs and discuss which ones are relevant for the flights today so they are already prepared.

Since all of these things are already taken care of, the actual turnaround can be pretty short. After shutting down the engines, one pilot will start loading the next flight plan into the flight management computer (FMC), which can usually be done via ACARS or loaded from a stored company route, and review that all waypoints and altitude/speed constraints are loaded correctly. In the meanwhile, the other pilot will do the external walk-around. Once that is done, the pilot flying will brief the pilot monitoring about expected taxi routes, the takeoff (including possible rejected takeoff) and the expected departure procedure (including possible return or diversion in case of an engine failure). An experienced crew can do this briefing in less than 5 minutes.
Once the gate is closed, the captain will get the final load sheet and will verify that everything is within limits. Now both pilots will independently do the takeoff performance calculation and compare the results. If they match, the values are entered into the FMC and you are good to go.
The limiting factor for turnaround times is usually the required time for disembarking, re-fueling and boarding. Regional airlines with short turnaround times do not load any trolleys for food and beverages during these turnarounds (they are all loaded in the morning) and only do a very superficial cabin cleaning (if any) to minimize time on the ground.
Aircraft manufacturers publish time estimates for these activities in their airport planning documents. Here is an example for an Airbus A320 without refueling (source):

They estimate 22 minutes without refueling, so anything shorter than that is really quite fast. With refueling of 20,000 litres (which is quite a lot, definitely more than you would need for a short haul flight), they estimate 44 minutes:


What is the relation between the boundary layer and lift of an aerofoil?

I wouldn't say that the boundary layer is responsible for creating lift, even if the real world friction enables the creation of circulation and therefore lift. It is mainly responsible for the drag.

Why? Take a look at airfoils in potential flow: they have lift but neither drag nor a boundary layer. Lift is created due to a pressure difference between the upper and lower side of an airfoil and you don't need any boundary layer to explain this pressure difference.

However, you do need a boundary layer to explain drag. The no-slip condition on the airfoil surface creates a layer with a high velocity gradient (from zero on the surface to $V_\infty$- the freestream velocity). Its thickness depends mainly on the viscosity the fluid around the airfoil:

No viscosity at all means no energy loss and therefore no drag.The velocity gradient can be infinite and the layer thickness is zero.
With higher viscosity the particles won't be able to follow such high velocity gradients and the distance between the no-slip surface to the freestream flow around the airfoil will be bigger: the boundary layer will be thicker. The drag will be higher too.


Is there any equation on propeller thrust that takes into account the number of blades

The most simple propeller thrust equations replace the propeller with an abstract disk in which the flow is accelerated. How this disk is composed in detail does not matter. However, more elaborate codes which also model the helical wake of each blade will use blade count specific algorithms.

So the answer is yes, there are algorithms which account for the number of blades, but they are more complex than a single equation.

This answer shows how the number of blades of the propeller for the Supermarine Spitfire grew with engine performance, and this answer sheds light on the number of blades of helicopter rotors.


How many axes are used in weight and balance calculations?

@Ron Beyer's comment is correct. Here's a little more information.

Generally speaking, in narrow-body aircraft, it's sufficient to calculate the CG only along the longitudinal axis. There may be limits along the lateral axis but which would only be exceeded with severely imbalanced wing fuel loads, and that is often handled by specifying a maximum fuel load imbalance.

Wide body aircraft typically require looking at the lateral CG as well as the longitudinal CG. However, the allowed lateral moment about the longitudinal axis may be high enough that the limitation comes into play only when carrying cargo. That's the case with 747-100/200/400 aircraft. As I remember, the max lateral imbalance for a 747-400 is 10,000,000 inch-lbs.

There are some fixed-wing aircraft that require looking at the vertical CG. The 767-300 does. I don't know about other 767 models. It's not an issue for 747s.

If you're interested in playing with CG movement on 747-400 and 767-300 aircraft, you can go to 747.terryliittschwager.com and look at worked examples or do your own.