How prevalent is traditional radar tracking of commercial aircraft?

There are many surveillance technologies available to track aircraft.

Radar is the most common technology used for ATC (Air Traffic Control) surveillance. Basically there are two varieties:

Primary radar

This type of radar sends a high energy radio pulse which reflects of the aircraft. The time delay of the received echo is a measure of the distance.
The characteristics of the transmitted radio pulse. Since aircraft don't have to participate for this radar to work this radar principle is mostly used for Air Defence purposes.

ATC primary radar usually has a maximum range of about 50-100NM, but can exceed 200NM. Primary radar is mostly used for airspace protection (monitoring unauthorized access) and airport surface control. These radars have a limited maximum range but a very low minimum range and provide reasonable accuracy.

Long range primary radar is expensive to operate. Due to the free space signal loss, long range radar needs to transmit a very powerful pulse and receive an very weak echo. The associated infrastructure (large antenna, active cooling) and power requirements make long range primary radar very expensive.

Military use of primary radar includes over the horizion (OTH) radar which has ranges well over 1000NM. These radars are geared towards detection of incoming missiles and aircraft and not suitable for air traffic control due to their lower accuracy.
Secondary radar

Secondary radar is the most common surveillance technology used by ATC.

This type sends a radio signal to the aircraft's transponder to which the transponder replies with its own radio signal. Again the time delay is a measure of the distance. The transponder can encode additional information about the aircraft (such as altitude or identity) in the reply. This radar technology relies on the correct functioning of the radar transponder.

Because the radar relies on transmission of energy from the aircraft, the transmitter needs less power than a primary radar. The maximum range of secondary radars can exceed 250 NM for aircraft flying high enough (above the horizon). Not all secondary radars are operated at that range though, airport radars are often limited to 50 - 100 NM.

Radar signal horizon

Then there are a number of surveillance technologies which are a bit different than radar:

(Wide Area) Multilateration

This technology uses multiple receivers spread over an area. By accurately comparing the times that an aircraft's transponder signal arrives at the different receivers the system can calculate where the signal must have been transmitted from. The transponder signal must be received by at least four receiver to get an accurate position. The accuracy of multilateration is best in the area surrounded by receivers; outside that area the accuracy of the system degrades quickly. A provide with enough receivers, a Wide Area Multilateration system can cover vast airspace volumes.
ADS-B

Automatic Dependent Surveillance - Broadcast is a surveillance technology that relies on the aircraft transmitting their position twice per second. A simple antenna and receiver is all that is required to receive these positions. Since the signal comes from the radar transponder, the above signal horizon figure applies. A very sensitive receiver can detect high flying aircraft far away. Not all aircraft are yet equipped with ADS-B but most passenger transport aircraft are.

The company Aireon is equipping satellites with ADS-B, so in 2018 there will be oceanic ADS-B coverage.
ADS-C

Automatic Dependent Surveillance - Contract is again a surveillance technology that relies on the aircraft transmitting their position. Contrary to the broadcast counterpart which transmits to all interesting parties, ADS-C addresses its transmissions to the contracted ATC facility. The data goes via a satellite link or over VHF when the aircraft is flying over land. Because of the satellite link, coverage is global (except the poles).
ADS-C reports are less frequent that radar or ADS-B reports, typically the system only reports at specific reporting points.

ADS-C is not installed on every aircraft, mostly on intercontinental transport aircraft. It is used mainly over the Pacific and the Atlantic.
Verbal position reporting

Not really a surveillance technology, but used in areas where there is no other means of surveillance available. The pilot reports his position over the radio to air traffic control. The maximum range of the radio transmission is the limiting factor here. Using HF radio, global coverage is achievable. The transmissions suffer a lot from static noise and sometimes other aircraft have to relay messages if no proper direct communication between ATC and the aircraft can be achieved.


What is the most efficient way to get your instrument rating?

The fastest path to any rating is intensive training.
If you can take time off from work and do an "accelerated instrument training" program you can probably knock out the rating in less than a month. That AOPA article says 8 days, I've seen a lot of two-week courses advertised.

Note however that there's a difference between being instrument rated and proficient for real-world IFR operations in actual IMC. These courses will almost certainly cram all the knowledge and procedures into your head that are required to get you to pass your instrument checkride, but you may have never flown an approach in actual IMC (if suitable weather doesn't pop up for you to fly in your time will all be simulated under the hood), and because everything is compressed and focused on "passing the test" you may come out of the program lacking the confidence to actually go out and use your newfound rating without doing some additional work with a local CFI (this is a point sometimes raised by pilots who have gone through these accelerated training programs).


Can you identify the plane with number NC 14959 photographed in Boston in 1937?

It is a Lockheed Electra 10A, and, by good fortune, quite a famous one now admired by hundreds of people every day. Details on the Electra Survivors Project. It was delivered to Eastern Air Lines on 24 September 1935.

It was later re-registered NC5171N and can be seen today in the Science Museum in London, displayed in the 'Making the Modern World' exhibition (as opposed to the aviation section). Its prominence there derives in part as being the same type as Amelia Earhart's aircraft on her final expedition, as well as the same type that British Prime Minister Neville Chamberlain used on his return to England after the ill-fated Munich Conference. (Note, this was not the actual aircraft in either of those events - but it is the one in your photo.)

 source


What kind of flight counts toward the commercial 100 nautical mile cross-country flight requirement?

Your question didn't give enough information for a 100% correct answer, so I'm going to make a few assumptions:

You are asking about FAA certification in the USA
You are asking about part 61 training, not part 141, 142, or anything else
You're asking about a single-engine commercial rating (this one is less important than the other two)

With those assumptions in mind, the controlling regulation is 61.169(A)(3)(iii-iv), which says (emphasis added):

(iii) One 2-hour cross country flight in a single engine airplane in daytime conditions that consists of a total straight-line distance of more than 100 nautical miles from the original point of departure;

(iv) One 2-hour cross country flight in a single engine airplane in nighttime conditions that consists of a total straight-line distance of more than 100 nautical miles from the original point of departure;

So you need to ask yourself:

Did you fly at least 2 hours?
Did you land at an airport at least 100 miles away from the original point of departure?
Did you do the entire flight during the day/night?

If so then you're good.  If not then no.


Could the Boeing 757 replace the Boeing 737 Max 8/9/10?

(Own work; adapted scaled drawings via boeing.com)
It's no coincidence the fuselage widths match, the 757 borrowed the 727's fuselage, which width-wise is the same as the 707 and 737.
@Brilsmurfffje and @CarloFelicione already raised good practical points, namely the indirect airline costs and why airlines would favor the 737 over a 757 re-engine, and the reboot costs.
If we look at the two planes from a pure engineering viewpoint, the 757 makes for a lousy substitute.
The MTOW is 27 tonnes heavier, but we'll gloss over that and say Boeing will certify it at a lower weight.
Bad wing (for the mission)
The 757 as shown above has a lot more wing. The wing areas are 185.25 $m^2$ and 127 $m^2$, for the 757 and Max, respectively. (45% more wing.)
Bigger wing is higher empty weight, i.e., the plane has more material, and subsequently the associated manufacturing costs. 13 tonnes of more stuff not counting the re-engine – newer engines are heavier. As for using CFM LEAP, between the highest 737 Max thrust and lowest 757 thrust option, the 757 has 13 kN more, so we're okay there.
Those 13 tonnes at approx. \$1,700/kg OEW:unit cost correlation already make the 757 some 22 million USD more expensive without taking into account the development cost associated with a re-engine. Unlike MTOW, there is no workaround for that.
Secondly, the 757's bigger wing is really bad for the cruise economy of the 737 missions. Low wing-loading is good for maneuvering and for using short runways, but cruise economy comes from aspect ratio and – ideally if it won't impact too much the takeoff performance – high wing-loading.
The 757 needed such a wing for fuel carrying reasons (volume and MTOW), after all it's suited for transatlantic operations using older engine technology. But when that much fuel is no longer needed (re-engine), the physical big wing remains.

Now, much like how the A330neo complements the A350, one could argue a re-engined 767 could complement the 787, but like also how the A330neo ended up badly for the A350-800, a 767 re-engine could be troublesome for the smaller 787s.


Why is the Aerodynamic Centre not affected by changes in Angle of Attack?

As the pitch of the wing increases moment arm decreases and at the same time lift increase, so the pitching moment stays constant.

In typical airfoils such as the wings of an airplane flying level sub-sonically the pressure center is at approximately 0.44 of the  cord length, and the aerodynamic center is at 0.25 of the cord length.

When the AoA increases the lift increases linearly and at the same time the CoP moves forward closer to aerodynamic center in a way that reduction in the length of the pitch moment arm is cancelled by increase in the force (lift); so the pitch moment is constant.

In fact the location of AC is calculated by finding the point that the decrease in pitching arm is proportional to increase of lift, otherwise one could pick any arbitrary point along the cord and calculate the pitching moment at that point, but it would not remain constant for a different AoA.


Is it possible to tow a smaller aircraft (like a LSA with a non-functioning engine) with a more powerful towplane?

Yes.
I know of a pilot in the USA who has done exactly this.  Both aircraft were Cessna 182s.  The aircraft to be towed was outfitted with a releasable tow hook mounted on the prop shaft (I believe the prop was removed).  It took a lot of effort to satisfy the FAA that this could be done safely.  Part of this effort included videotaping towing a Cessna 182 (the one that ended up being the towplane) into the air via the same prop shaft-mounted towhook with a motorcycle on a long 7000' runway.  Since the motorcycle had much less engine power than a Cessna 182, this was evidence that the concept would work.
The end result was that the disabled plane was successfully ferried in this manner, with permission from the FAA.  I don't recall the exact starting point of the ferry flight but I believe the distance was in the neighborhood of 60 miles.
The ending point was an untowered field and as best as I recall the starting point was as well.
Naturally, the tow line was released before the aircraft entered the landing pattern.
This all happened sometime between 1990 and 2005; I don't recall the date more accurately than that.
If your LSA did not have a tractor (nose-mounted) engine, you might have more of a challenge.
A qualified glider tow pilot will be needed to fly the towplane.


Is the turning motion of a banked airplane caused by true centripetal force?

Centripetal force is defined as the component of the total force acting on the object that is causing it to follow a circular path. It is the force exactly perpendicular to the velocity vector.
To create a circular path, the force needs to turn with the velocity. If you have a force that keeps its spatial orientation, less of it will be centripetal and more of it will just accelerate the object as it moves and the resulting path will be parabolic (e.g. the ballistic curve under gravity).
The horizontal component of lift always contributes wholly to the centripetal force, but this is again quirk of the definitions: lift is the component of the aerodynamic force on the wing that is perpendicular to the relative wind and drag is the component that is parallel to it. So analysing the situation in the reference frame of the air mass, relative wind is the velocity vector.
Now if the plane didn't turn with its velocity vector, it would just gain side-slip, the lift would decrease—banking into side-slip reduces the angle of attack—and the aircraft would stop turning—it's flight path does turn initially, even if the body does not—and settle in sideways flight. So we need to make the aircraft rotate with the turn.
Now just like linear motion, rotating motion stays constant¹ unless acted upon by a moment of force (a.k.a torque). So when initiating the turn, a yawing moment of force needs to be created to also initiate the rotation.
A moment of force may be created by a pair of force of opposite direction and different action lines, so it does not have to cause any linear acceleration, but in case of aircraft usually an initially unbalanced force is created on the tail that starts the rotation, but also accelerates the aircraft sideways until balanced by drag on the fuselage. Note that this force is out of the turn (and up), so it reduces the centripetal force a bit.
But in a steady turn the torque is zero. Or oscillating around zero as the correct angular velocity is maintained via feedback loop. So the horizontal component of lift is the only centripetal force in a coordinated turn. In not coordinated turn, some side force on the fuselage is added or subtracted depending on whether it is a slip or skid.

¹ Angular momentum is conserved but the angular velocity does not have to be. Depending on the axis of rotation and mass distribution (moment of inertia) you may get strange phenomena like the Dzhanibekov effect.


To be statically stable in pitch, the tail has to generate a downforce that opposes a continuous nose down pitching moment.  Everything else being the same, more speed increases downforce, less speed decreases it.  The equilibrium state is when the opposing forces are in balance in steady state flight, hands off the controls, and the airplane is said to be "in trim".  This is achieved at a given airspeed for a given set of "configuration of forces" you might say (pitching moments, thrust lines, C of G positions etc) and is called "trim speed".

Trim speed is the speed at which tail downforce balances the nose down pitching moments to achieve equilibrium (not accelerating or decelerating) for a given set of physical conditions.  FAR 25 static stability requirements require the plane to positively seek this speed by pitching uphill or downhill when disturbed from that speed in an attempt to regain equilibrium.

So the relation to the tailplane is that speed in excess of trim speed causes the nose to pitch up due to excessive downforce, which makes it go uphill and slow down, trying to get back to that equilibrium state.  Vice versa when speed is less than trim speed; it pitches down trying to get to the equilibrium state.  In an actual airplane it overshoots its equilibrium point several times trying to get there and eventually zeros in (the Phugoid oscillation).

Some other configuration change, a power change, a C of G change, a dragging item change, a flap sticking down, or elevator incidence change, will alter the speed at which equilibrium is achieved or trim speed. Once stabilized at a new trim speed, it will now seek the revised trim speed as before, if disturbed, as the tail responds to downforce changes with airspeed as described.


What are these FAA facilities in Seattle doing?

Seattle’s "golf ball" in Discovery Park was once part of the country’s Nike Hercules air defense system of missiles and radars in the 1950s. While most of the structures have been torn down, this golf ball still stands as a relic of the Cold War.
Discovery Park used to have an array of radars at its peak. It was a Nike Ajax air defense site in 1953 before becoming an Air Force command center for the Nike Hercules system. The remaining radome was built in 1959. It is not currently in use.

https://blog.seattlepi.com/thebigblog/2013/04/09/what-is-that-giant-golf-ball-in-seattle-sky/#photo-226558

Initially assigned a Permanent ID of RP-1 and later a Sage ID of Z-1. Abandoned by the Air Force in 1963 and turned over to the FAA, now known as Fort Lawton FAA Radar Site.

https://seattlediscoverypark.org/faa-tower/

More information:

https://en.wikipedia.org/wiki/Project_Nike


What does aerodynamic noise of an airliner sound like in landing configuration?

Aerodynamic noise has many sources. It is not white noise, because some frequencies are dominant. Generally it happens when flows of different speed collide, or when a standing wave develops in a cavity. Common noise sources are:

Uncovered openings, like vent holes or control surface gaps. Like when you blow across the top of an open bottle, they produce a howling sound with a dominant frequency that depends on flow speed and opening size.
Tollmien-Schlichting waves in the boundary layer. These frequencies change with speed and their location along the flow path, and generally are responsible for most of the hissing sound of gliders.
Separated flow, which produces alternating separations behind blunt bodies. Here the main frequency is that of the Karman vortex street that forms behind them. It can be calculated if the Strouhal number Sr of the flow is known. This is the equation for the main frequency $f$ of a bracing wire with the diameter $d$: $$f = Sr \cdot \frac{v}{d}$$
Here $v$ is the airspeed, and for bracing wires Sr is normally 0.2. Bracing wires (or a blunt trailing edge, for that purpose) produce a characteristic whistling sound.

As you said, the landing configuration makes most noise. In addition to the factors above, you now have

Extended flaps, mostly with gaps between them which show high local flow speed. This local high-speed flow is very noisy.
Many more blunt objects sticking out of the airframe: Landing gears, gear covers or landing lights. The particular noise of landing gears was once tested with a high-performance glider which had styrofoam gears fitted under the wings. They broke off when it had to land, but yielded valuable data when compared to the noise of the clean glider. Sorry, there is no photo of this experiment on the web!
The gaping hole of the landing gear well. Especially while the gear is moved, this creates a lot of noise, but even after extension a part of the well is uncovered and adds its noise.

Here is a good overview of different noise sources. It is best read with a good working knowledge of German.

To answer your question: The sound is a mixture of hissing and whistling in different frequencies. If you stand close to the Autobahn (best is a section without speed restrictions), the noise of the passing cars is similar, but less intense. At 180 km/h, engine noise starts to vanish in all the aerodynamic and tire noises ...


Which sub-scale setting may a pilot use on an instrument approach in South Africa--QFE or QNH?

I have never been given a QFE to conduct an instrument approach in S.A. It does happen in some countries but then everyone has to use it. If you look on an approach chart you will see the vertical profile is given in terms of height above sea level so you wouldn't be able to conduct the approach with QFE set. Edit: The SACAA charts do show height of the waypoints of the vertical profile, but Jeppesen doesn't. The MDA and DH are given terms of elevation and height, but this is to use in conjunction with the radio altimeter. QFE might be used by aerobatic pilots or some military operations but I think its use is rare. Having said that, the AIP does appear to allow the use of QFE on a second altimeter during the final approach see note(2) and point (f) below. Therefore it appears that B is the answer the CAA is looking for. Using the word "only" in answer A would make it incorrect.
Please look at the AIP here with particular attention to the Altimeter Setting Procedures, I will try elaborate in due course.
Firstly the AIP says

The altimeter setting procedures in use conform to those contained in
ICAO Doc 4444 ATM/501 Procedures for Air Navigation Services and ICAO
Doc 8168 OPS/611 Procedures for Air Navigation Services - Aircraft
Operations

Then it says

During flight in the vicinity of an aerodrome at or below a fixed
altitude called the transition altitude, an aircraft shall be flown at
altitudes determined from an altimeter set to sea level pressure (QNH)
and its vertical position shall be expressed in terms of altitude.

Further down below it says

On reaching the transition level at least one altimeter within the
aircraft shall be set to the QNH and thereafter the vertical
positioning of such aircraft shall be by reference to altitudes.
Note 1: On reaching the transition level, pilots shall reset their
altimeters to the QNH without requesting Air Traffic Control (ATC)
permission to do so and without notifying Air Traffic Control (ATC)
that the change has been made.
Note 2: This does not preclude a pilot from using a QFE setting for
terrain clearance purposes during the final approach to the runway.
f)   During the approach to land, terrain clearance may be determined
by using either a QNH altimeter setting (giving altitude) or a QFE
setting (giving height above the QFE datum)

I believe the intention is to allow the pilot the discretion of using a second altimeter with the QFE set, but when you talk to ATC it will be with reference to the altimeter having QNH set.


Where is the mistake in this air density calculation?

The mistake is subtracting the ISA temperature at sea level from the ISA+18°F temperature at altitude in step two. If your atmosphere is heated up, it needs to be hotter at sea level as well, or your lapse rate in the first step and the denominator is wrong.

First calculate density for ISA conditions. This gives 0.7708 kg/m³.

Then used the ideal gas law to see how a 10 K temperature increase will reduce density at constant pressure. The density ratio is inversely proportional to the temperature ratio, so the result is 0.7421 kg/m³.

When checking your result, input only 10 K into the calculator, not 18 K !!!


Is there a formula to calculate how big a ventral fin should be?

There is no single formula - the number of factors to consider are too numerous and the load cases are too diverse. Here is an incomplete list:

Directional stability: Depending on fuselage size and shape, the tail must be sized to pull the aircraft into the wind direction. The fuselage is destabilising in yaw and the tail is needed to counteract that. Depending on factors like wing sweep, some of that stabilisation can be contributed by other parts of the airframe.
In multi-engined aircraft: Yaw from asymmetric thrust. If one engine fails, the fin must be large enough to create an equal but opposite yawing moment to that of the still running engine on the other side. Multi-engined aircraft have a minimum speed below which directional control with one engine inoperative is lost.
In high aspect ratio designs: Counteract adverse yaw. When ailerons are deflected and the aircraft rolls, the direction of lift on the side with the trailing-edge-up aileron tilts forward and vice versa. This horizontal lift component creates an undesired yawing moment that the tail needs to neutralize. This effect varies with speed, so if you want good low-speed maneuverability, this load case determines vertical tail size (mostly of gliders).
Dutch roll damping: Sometimes static stability in yaw is not sufficient and dynamic stability sizes the tail.
Maximum flight Mach number: At high Mach, the upper side of the plane flies in less dense air and a traditional vertical tail loses much of its efficiency. Here a ventral tailfin can help to reduce tail size considerably.

Add to this the fact that the destabilizing effect of the fuselage increases with sideslip angle and the fact that the vertical tail as the higher aspect ratio surface of the two will reach its maximum lift first and suffer a noticeable decrease in effectiveness at larger sideslip angles. Now details like a highly swept fillet are needed to maintain tail effectiveness at high sideslip angles.

Finally, it depends which of the load cases is sizing your tail, and that can be determined by factors like fuselage length. Tail effectiveness for directional control grows linearly with fuselage length and for yaw damping with the square of fuselage length. If you want to fly the same tail on fuselages of different length (like most airliner models do), your tail might be sized by a different load case on a different aircraft than the one it is mounted on.

If you want to fly low and fast, it might be that the loads on the vertical deform the structure so much that the efficiency of the vertical tail is greatly reduced. In that case it does not help to make the tail bigger, instead ventral fins must be added. Now you need not only to look at the best tail size but at the best overall tail configuration as well.


How do Class B transitions work in the US?

Is requesting VFR flight following in a class bravo the same thing as requesting a class bravo clearance?

No. Flight following just means that the aircraft is receiving traffic advisories. A VFR aircraft needs explicit clearance to enter the Class B. The pilot should net ATC know that they intend to enter the Class B.

Does requesting a class bravo airspace transition automatically include VFR flight following (radar traffic information service)?

Yes, ATC must separate VFR aircraft from VFR/IFR aircraft while in the Class B. (7110.65X Section 7-9-4)

If I am cleared into the bravo airspace and the controller gives me a heading and altitude to fly that clips the airspace of an underlying class C / D airspace, have I satisfied the requirements to enter said airspace (class C - 2-way communication and squawking mode C, class D - 2-way communication)?

If ATC has given specific instructions that take a pilot through other airspace, then ATC should coordinate this with the appropriate controllers. Per 7110.65X Section 7-9-2 the controller should also either vector aircraft to stay in class B or to inform them if they are leaving it. Pilots should not change frequencies on their own unless asked, and the pilot should ask the controller if they are unsure.

Also, note that:

  Assignment of radar headings, routes, or altitudes is based on the provision that a pilot operating in accordance with VFR is expected to advise ATC if compliance will cause violation of any part of the CFR.

Why does ATC provide traffic advisories for VFR aircraft in class bravo airspace at all if they are on the hook for providing separation?

As described above, ATC is required to separate VFR aircraft from other aircraft in the Class B. ATC is instructed by 7110.65X Section 2-1-21 to:

  ...issue traffic advisories to all aircraft (IFR or VFR) on your frequency when, in your judgment, their proximity may diminish to less than the applicable separation minima.

Unless a VFR aircraft has explicit instructions, ATC does not know for sure what they will do. And IFR aircraft may still need to perform unexpected maneuvers like a missed approach. Traffic callouts make it easier to apply visual separation if needed.


How can an aircraft hover almost vertically?

The aircraft in the video is a remote-controlled (rc) airplane. Why it can "hover" is simply:
The thrust generated by a big fan / rc-jet-engine is much higher than the weight of the plane.
If the force generated by the turbine is the same as the downward-force of weight of the airplane, it hovers.
By very carefully adjusting the thrust and placing the aircraft in this "nose-up" position, a skilled rc-pilot can hover the plane until the battery runs out or fuel gets low.

As example:
An aircraft that weights 10,000 kg's produces a downforce:
$$F=m\cdot g=10,000 \cdot  9.81  = 98,100N $$
To make this aircraft hover, you have to create a upward force of at least $98,100 N$. If you manage to do that and you can align the generated thrust / downforce perfectly on the Y-Axis, the aircraft will hover:
$F_{down} - F_{up} = 0N$, the two forces will cancel each other out and you don't have any movement in the Y-Axis.
However, if you have engines that create more thrust than the downforce, the following will happen:
$F_{down} - F_{up} \geq 0N$, that means the aircraft will climb vertically (On the Y-Axis).
The same principle applies to other "real" aircraft, like the Sea-Harrier:

It uses the engine to create a force facing upwards. Because the force is greater than the downward-force created by the aircrafts weight, the Harrier can land / takeoff vertically.
The hovering airctaft is controlled by a trust-vectoring fan / turbine. Controlling the plane with the "normal" surfaces is not possible, because the airflow over the controll-surfaces on the wing is to slow. Therefore, only planes with trust-vectoring capabilities COULD hover like the rc-plane in your question.


What are the reasons behind switching FDs off for a VOR approach?

ok two questios there really:

entering vapp as speed constraint at the FAF.
After the FAF you want to be flying a constant 3deg path (or whatever the approach gs is). Changing configurations and deploying flaps while on final will make the aeroplane baloon and deviate from that flightpath. To minimize those (uncorectable) deviations, the SOPs will call for the aircraft to be fully configured (flaps full, gear down and Vapp) at the FAF when starting the final descent.
By entering the vapp in fmgc at the faf you are basically telling the computers I want to slow down early and configure to full flaps before thr FAF. The fmgc will then compute your descent to allow for that deceleration segment. It's not SOP as far as I can tell, just a gimmick people use to tell computer you want early stabilized.

Switching FDs off
Two points here: you are not switching them off at the FAF. You are changing them to a TRK/FPA mode (usually 1nm from FAF) to better control your glidepath angle durring final. Yes, you could use v/s to do that, and use trigonometry to compute the v/s required to maintain 3 deg for a given groundspeed, but why would you.  Changing winds will change your groundspeed, and thermals will mess up your flight path. Setting -3deg in the FCU is much easier.  I can then set -3.2deg if I get, say 20 feet high, and I should be back on profile in about 1nm.
Second point: FDs will be switched off (completely) after disconecting A/P and at least at reaching minimas. Reason is the ap guidance is not certified to guide you after that so it is manual/visual flying using PAPI if available.

Note: this is all about flying a manually-selected non-precision approach (eg in NAV/FPA or TRK/FPA) mode with AP on. Using a fully managed approach is a different story


Do dispatchers ever update and re-send a flight plan to an aircraft in flight?

Anytime the original routing or altitude is significantly changed, a new flight plan is calculated by dispatch and sent to the aircraft.  Significant changes could mean the aircraft may not have enough fuel to reach the destination. Even minor changes are routinely re-calculated and sent to the aircraft.

The pilots send dispatch the new routing and altitude along with an updated ETA and FOB(fuel onboard) for the next waypoint. The flight plan is then recalculated from that point and sent to the aircraft.

Routing changes can be due to traffic conflicts, airspace closures, military activity, volcanic activity, etc.

If for any reason the aircraft is unable to contact dispatch, the pilots must do their own calculations to insure they have enough fuel.

If the fuel remaining is marginal, the flight can be re-filed with a new alternate closer to the final destination. If conditions can be met, the flight might be re-filed with "no alternate".


How does the MD 900 accomplish auto rotation with the NOTAR system?

According to https://en.wikipedia.org/wiki/NOTAR the NOTAR fan is driven by the main rotor transmission. This will ensure maneuverability during autorotation.


You have asked two questions here. The first one:

  Does the thrust of the fan in a turbofan jet engine decrease proportionally with decrease in the diameter of the fan?

We need to clarify what you mean by "proportionally". If you mean if you halve the fan diameter, the thrust goes down by half, the answer is no. If you mean if you reduce the fan diameter, the thrust goes down, the answer is yes.

For a subsonic engine, net thrust is given by mass flow (kg/s), and the change in velocity of the mass flow between the inlet and exhaust exit. Exactly how the mass flow and exhaust velocity will change as the fan diameter changes is complex and will vary with each engine, so a general statement cannot be made.

Question two:

  As the fan in a jet engine is responsible for over 70% of the total thrust can a spark ignition engine driven fan of 1 meter give an equal thrust of a 1 meter diameter turbofan jet engine with the jet exhaust thrust removed form the sample? All inlet duct and shroud would be identical, also the fans.

Firstly, you have said "the fan in a jet engine is responsible for over 70% of the total thrust" as if this is a fact. It's not - what you can say is something like "in a high bypass ratio engine, the fan can be responsible for over 70% of the total thrust".

So, now to the question part:

  Can a spark ignition engine driven fan of 1 meter give an equal thrust of a 1 meter diameter turbofan jet engine with the jet exhaust thrust removed form the sample? All inlet duct and shroud would be identical, also the fans.

If, as you state, the inlet, fan, and exhuast duct are the same, and we ignore the thrust from the core (turbine exhaust flow), then if the fan driven by the spark ignition engine and a fan driven by a turbofan engine are at the same RPM, then, yes, the thrust produced by both fans is the same. The fan doesn't care where the torque required to turn it comes from, so long as the torque is adequate to achieve the same RPM.


Has a commercial jet airliner ever stalled on takeoff / at low-altitude?

There are two fairly recent airliner crashes I can think of that were the direct result of an aerodynamic stall, one is Air France 447 and the other is Colgan Air 3407.
AF447 was at cruise height when the incident began, so that one does not fit with your question.
Colgan3407 was landing, so was pretty much "low level" (Does "jet" permit a turboprop?).

Following the clearance for final approach, landing gear and flaps (5 degrees) were extended. The flight data recorder (FDR) indicated the airspeed had slowed to 145 knots (269 km/h).[3] The captain then called for the flaps to be increased to 15 degrees. The airspeed continued to slow to 135 knots (250 km/h). Six seconds later, the aircraft's stick shaker activated, warning of an impending stall as the speed continued to slow to 131 knots (243 km/h) [...]
In its final moments, the aircraft pitched up 31 degrees, then pitched down 25 degrees, then rolled left 46 degrees and snapped back to the right at 105 degrees. Occupants aboard experienced g-forces estimated at nearly 2 G's. The crew made no emergency declaration as they rapidly lost altitude and crashed into a private home at 6038 Long Street,[24] about 5 miles (8.0 km) from the end of the runway

Going back in time, we can probably find a few more - some of the older examples may stretch what you consider "commercial aviation" by todays standards, and some most certainly were not "Jet" engined, but for the sake of completeness here goes:

1923 Daimler airways DH34 crash

The flight was a scheduled domestic passenger flight from Croydon to Manchester. It was also reported to be carrying mail,[2] although this was later denied by the General Post Office.[3] While flying over Buckinghamshire, a storm was encountered. Witnesses stated that an engine stopped, but was then restarted. It appeared to them that an emergency landing was going to be made at Ford End, Ivinghoe when the aircraft dived to the ground and crashed at Ivinghoe

Another DH34 a year later

The aircraft took off from Croydon Airport on a scheduled international passenger flight to Le Bourget Airport, Paris. Witnesses described the aircraft as flying low over Purley before nosediving to the ground

American airlines flight 1

American Airlines Flight 1, dubbed "the New Yorker",[1] was a regularly scheduled, multiple stop flight from La Guardia Airport to Chicago Municipal Airport. It had intermediate stops at Newark, New Jersey; Buffalo, New York; Detroit, Michigan; and South Bend, Indiana. On October 30, 1941, on the flight's leg between Buffalo and Detroit, the American Airlines Douglas DC-3-277B operating the route crashed into a wheat field approximately one half mile east of the town of Lawrence Station, Ontario

Llandow air disaster

the Avro Tudor was approaching runway 28 of Llandow aerodrome at an abnormally low altitude with the undercarriage down. The pilot attempted to correct the descent by increasing the power of the engines and brought the plane up. The aircraft rose steeply to 100 m (300 ft) attaining a nose-up attitude of 35 degrees to the vertical, and then the aircraft stalled

Aeroflot Flight 513

The aircraft was de-iced before takeoff. In the cockpit, the check captain observing the trainee's performance sat on the right; the trainee sat on the left. The captain and first officer remained in the cabin and did not assist the trainee and check captain during takeoff. Flight 513 took off from the runway at a bearing of 100°. At an altitude of 40–50 meters the angle of attack increased to the point of causing a stall. The Tu-124 never recovered from the stall and crashed into a field of snow

Delta flight 1080

During the takeoff, the Lockheed L-1011's left elevator became stuck in a fully upwards position, leading to the aircraft pitching up aggressively and causing the aircraft to lose speed and nearly stall. The pitching force, unable to be overcome by fully pushing the control column down, was counteracted by reducing the thrust on the L-1011's wing engines but not the tail engine. The differential thrust pitched down the nose of the airliner and allowed the pilots to land the aircraft.

China Eastern Airlines Flight 5210

On 21 November 2004, just two minutes after take off, the Bombardier CRJ-200ER fell from the sky and crashed into a lake in Nanhai Park, next to the airport, killing all 53 people on board and 2 more on the ground. [...] An investigation by the Civil Aviation Administration of China (CAAC) revealed that the plane had not been de-iced by the ground crew while it was parked on the tarmac.

Regional Airlines Flight 9288

On approach to Varandey Airport, the crew allowed the An-24RV's speed to drop and its nose to rise until in stalled. At 13:53, the aircraft struck a hill, crashed about 5 kilometers (3.1 miles) from the airport, and burned, killing 28 people (two crew members and 26 passengers).

West Caribbean Airways Flight 9955

The aircraft, a Let L-410 Turbolet, had just taken off from El Embrujo Airport at 9:50, when the left engine flamed out. The crew continued with the takeoff, but the speed of the aircraft decreased rapidly. The aircraft then banked dangerously too far to the right and stalled. The aircraft crashed into a mangrove forest, located just 113 metres (371 ft) from the airport runway.

Turkish Airlines Flight 1951

The crash was caused primarily by the aircraft's automated reaction, which was triggered by a faulty radio altimeter. This caused the autothrottle to decrease the engine power to idle during approach. The crew noticed this too late to take appropriate action to increase the thrust and recover the aircraft before it stalled and crashed.

TransAsia Airways Flight 235

Two minutes after takeoff, the pilots reported an engine flameout. Flight 235 climbed to a maximum height of 1,510 feet (460 m), then descended. The other engine, still working, was shut down mistakenly.[1][2] Immediately before crashing into the river, it banked sharply left and clipped a taxi travelling west on the Huandong Viaduct

So, yeah, quite a few actually!


There's an option for a tail mounted camera for the passenger entertainment system (PES). It's the same one they use on widebody jets, but it's not hooked up to the cockpit for taxi purposes.

Airbus press release says

  Designed for a private customer, this cabin seats just over 30 passengers and includes such features as touch-screen technology, advanced passenger entertainment and communications, plus a tail-mounted camera.


Using e.g. Boeing's annual commercial aviation safety statistics, one can essentially show that with each new aircraft generation, the accident rate reduces. This answers your question about statistic involvement, but doesn't really confirm a causal relationship, since it's not only automation but e.g. also human machine interface (flight deck) design and system architecture that improves. However, I would assume there are quite probably at least some safety improvements due to automation in there. One would need to go about analysing the accident factors to prove this.

As an interesting aside touching on this topic, a former colleague of mine flying commercial jets recently offered his first-hand view on different aircraft automation levels in his blog.

While not a comprehensive answer as such, I hope the links allow you to pursue this a bit further.


Jet fuel will not self-ignite when starting a modern turbine engine.
This article from the WingMag Aviation Magazine says:

As the temperature isn’t quite sufficient to initiate self-ignition (the autoignition temperature of aviation fuel is around 220 degrees Celsius), spark plugs are arranged around the combustion chamber. They generate a spark that ignites the air-fuel mixture and the turbine now drives the fan and compressor through a shaft, as described above. The exhaust gas temperatures begin to rise and the engine will now keep “running” as long as there is a supply of aviation fuel. The igniters are switched off by the FADEC once the exhaust gas reaches a certain temperature because they are no longer needed.

Once the engine is running at a sufficiently high speed, the autoignition temperature can be sustained (same article):

[The fuel] is injected into the combustion chamber through several “fuel nozzles” where it can self-ignite and continue to run if the temperatures are sufficiently high.

See also How is combustion flame maintained in the combustion chamber after igniters are switched off?
Igniters are not only needed for a cold start. They are also used in case of an engine flameout. From the Boeing 747-8 FCOM (7.20.8 - Engine System Description, emphasis mine):

Auto-Relight
An auto-relight capability is provided for flameout and rollback protection.
Whenever the EEC detects an engine flamout or rollback, both igniters are
activated. A flameout is detected when a rapid decrease in N2 occurs. A rollback
is detected when N2 falls below idle RPM or compressor pressure falls below idle
minimums.

Note that this is for a modern jet engine, the General Electric GEnx.


Does a glider pilot need to file an IFR flight plan to legally fly in cloud in class E airspace in the US?

As answered here, requesting a pop-up IFR from ATC counts as "filing" a flight plan.

It should be noted, as explained here, that airfiling with ATC is a "workload permitting" activity, meaning ATC is not obligated to grant it. They can always refer you to FSS.

Climbing or descending through a cloud layer is one of the generally accepted use cases for pop-up IFR requests, so while ATC might be surprised by a glider asking for it, I can't see why they wouldn't treat it the same as an airplane requesting the same.

The main challenge I see, at least for non-motor gliders wanting to climb, would be phrasing the request correctly to get a clearance they can physically comply with. Maybe "circling within Xnm of present position" to allow for thermaling? It's also possible to request a 3D box if you want to do more complicated maneuvers/work; I'm pretty sure I've seen a question here on that.


Why would a PAPI and ILS glide slope for the same runway not coincide?

From the FAA AIM (section 2-1-2(b) Visual Glideslope Indicators): PAPI angles are based on obstruction clearance +/- 10 degrees from the runway centerline, up to 4 miles from the threshold. The ILS provides for obstruction clearance in a 3-6 degree angle on a 3 degree glide path. Therefore, if there are obstructions in the PAPI clearance area (e.g. a tower off to the side of the rwy) that don't exist in the narrower ILS clearance area, the PAPI will have to be a steeper angle.


What are the "spur" devices on this U2 pilot's boots?

These are part of the foot restraint system fitted to the seats used in the SR-71, later U-2 and some Space Shuttles. (They're all derived from the same basic design).

The spurs engage in two ball nipples that protrude from the lower part of the seat. The nipples are connected via cables to reels beneath the rear of the seat which pull the pilots feet in during the ejection sequence.

The seat separation sequence severs these cables (amongst other things) allowing the seat to drop away.

You can see the nipples on the lower part of this Space Shuttle seat:

Source:The Ejection Site


Where can the ICAO recommendations be found?

ICAO publishes and maintains 19 Annexes to the Chicago Convention. They pertain to all matters in aviation and provide the framework for national legislation in each of the member countries in the form of Standards and Recommended Practices (SARP).
In addition to the 19 Annexes, ICAO also produces more detailed guidance in the form of Procedures for Air Navigation Services (PANS): PANS-ABC, PANS-OPS, PANS-ATM. These are also usually referenced by their Doc number: 2007, 8168, 4444, etc
In addition to the PANS, for specific regions of the world ICAO publishes Regional Supplementary Procedures (SUPP) to incorporate regional variants/requirements.

Any ICAO contracting state may have local legislation different from SARP/PANS, but is obliged to notify ICAO of these differences. You will find these differences in the country's AIP section GEN.

Getting electronic copies of these documents is a bit more difficult.  ICAO sells these documents for a very 'aviation' price. Some CAA's and institutions will provide electronic copies in PDF form, but they will most likely be out of date and their legality is suspicious at best. Welcome to the world of international law.


Is there a landing gear system that extends automatically to prevent belly landing?

The simple fact is that an unintended gear deployment could be catastrophic, as it has a profound impact on the flight dynamics of the aircraft (one of the reasons there are warnings for both retraction and extension).

The benefits would be marginal as checking gear down is part of the bread-and-butter procedures for all retractable gear aircraft.

Keep in mind adding some automation to an aircraft has far ranging impact, just off the top of my head adding automatic gear mechanism would require:

Standardization of the automation
Modification of procedures
Training of pilots, and then re-certification of pilots
Training of maintenance crews, and then re-certification of the crews
Possible change to the maintenance schedule of aircraft
Certification of the new system by the regulator

and you would still need a backup / redundant system; and now you are back to the manual controls.

I can imagine this being implemented in remote piloted or autonomous aircraft though; as an additional workload relief.


Do pilots turn off the engines during de-icing?

Generally, it's not required to shut the engines down.
Sometimes you're deiced at the gate or just off the gate, and in those cases you've not started the engines yet. Or if it's necessary to remove ice on the bottom of the wings or from the bottom/front of the (extended) flaps, those would be cases when you'd shut the engines down for deicing. But most commonly, you taxi to a de-ice pad (parking area), leave the engines at idle with the bleed valves closed (to avoid getting deice fluid into the air conditioning system - even a trace of it creates kind of a stink), and deice with engines running.
The engine cowl is deiced NOT with fluid but thermally, tapping bleed air (upstream of the bleed shutoff valves, so it's always available) to heat them. Thus the fluid is not directed at the engines, but is intentionally kept away from them.


Longitudinal stability of airships: How is the critical speed defined?

On page 43 of the Technical Manual of Airship Aerodynamics I found the following image:

Here $F_e$ is the resultant airforce on the hull, or the dynamical lift of the hull. As this is before the CoG, it is destabilizing.
This source mentions Munk's formula being:
$$ M_e = Volume \cdot 0.5 \rho V^2 (k_2-k_1) \sin{2\theta} $$
Where $k_2$ and $k_1$ indicate the effect of gas movement inside the airship.
I tried to trace the origin of this formula in Munk's paper, available here, but I can't immediately find a clear explanation.

The critical speed is reached when this resultant airforce equals the moment induced by the weight:
$$Wh\sin{(\alpha + \theta)}=Volume \cdot 0.5 \rho V^2 (k_2-k_1) \sin{2\theta}$$

In this sense, the critical speed is the maximum speed at which the gravity moment is able to compensate the moment induced by dynamical lift. As such, one should stay below the critical speed.


How much might soft skin reduce aircraft skin friction?

This has mostly been examined for aquatic flow, e.g. with the soft skin of dolphins. Studies were done with test setups because measuring the boundary layer around live dolphins is exceedingly hard.

One study compared a rigid cylinder with a soft one of the same dimensions, using a polyurethane coating. Below is a diagram from that study with 3 denoting the rigid and 6 the soft cylinder. As you can see, the difference is small but consistent over the range of Reynolds numbers tested. Picture source here.

For dolphins, active regulation of muscle tension might be responsible for a resonant vibration of the skin, but much of the literature is still rather speculative. From the study:

  Based on experimental research on live dolphins, a hypothesis has been formulated (see Chapter 1); this is that by the regulation of the skin muscle tension dolphins promote resonant interaction with a flow. This leads to interaction of fluctuations of the boundary layer and natural frequency of fluctuation of the dolphin skin. As a result, the skin coverings vibrate with resonant frequency practically without energy consumption. Fluctuations of this coating occur at a frequency that controls the frequency of bursting from the viscous sublayer. This is also the reason for the abnormally low resistance, which has been discovered in the authors’ modeling experiments.


Chocks - why the wide variances in price?

The point of wheel chocks is to prevent the tire from rolling (and thus the aircraft from winding up "somewhere other than where we parked it). The aircraft doesn't know how much we spent on the chocks, and if it did it probably wouldn't care. (OK, it might laugh at you if you buy solid gold bars to chock a Cessna 150.)

Aside from pretty obvious quality-related things (a $5 set of chocks made out of cheap rubber that fall apart when you squeeze them in your hand)
the big reasons for price differences come down to a few things:

Size

Just like with chocking a car or truck there are various sizes of chocks available, and they vary in length and height:

For very large aircraft very large chocks are used (wider and taller):

…and for smaller aircraft smaller chocks are used (shorter and narrower):

Big chocks require more material, and thus cost more to make than small chocks, so logically they cost more.

Nice Features & Laziness

I have a set of $20 aluminum wheel chocks. They have a bungee cord that keeps them tight against the tire (so there's no room for the tire to roll), and they weigh just over 1 pound (they're light and small enough to throw in the plane without thinking about it).

The guy two planes down from me has a wheel chock made of three sections of 2-by-4 inch lumber, screwed together to be just slightly wider than his tires and painted safety-orange. It probably weighs less than 5 pounds and cost him $10 and a few minutes with a power drill & spraypaint.

Both work equally well, but I was willing to pay for someone else to cut and bend some aluminum that I can fold up into a small space easily rather than finding a chunk of lumber I didn't need and making my own chock.

"Standard Aviation Markup"

There's a joke that when trying to determine the price of a component for an aircraft you take the price of that component in a non-aviation application and add some zeros to the end of it.
That's not a joke in this case: Those two rubber chocks you posted are, for all practical purposes, identical - with the exception of their price.


What is this weapon spotted at an airshow in South Africa?

@mins got this one right. It's a British Tigercat short range surface to air missiles launcher system. The cones are protective weather covers for the missiles which are removed prior to launch.

As to the 'buckets and chains' I'd venture a guess that they are a device to deflect and dissipate the rocket blast during launch but I am not totally sure. But they can be seen on YouTube (at 0:07 and 0:39).

From YouTube, on the right the blast being deflected up/down.


What are the differences between symmetrical and cambered airfoils?

symmetric wings don't produce any lift at 0° AOA whereas cambered wings do.

Yes, that's correct.

Usually, the most important difference is that a cambered wing is optimised for a positive angle of attack. It produces less drag for the same amount of lift, and can produce more lift before stalling.

Obviously that assumes that the wing is the right way up - a cambered wing will be less efficient and stall earlier when inverted. And a symmetrical airfoil will produce less drag when no lift is required (e.g. a vertical stabiliser in steady flight)


Why do all new European fighter jets have delta wings?

No, they were not designed separately. They were designed by people who had all participated in collaborations before. The origin was the research into unstable configurations performed by MBB in Germany in the late 1970s by a modified F-104, the control configured vehicle F-104 CCV.

F-104 CCV (picture source)

As a result, MBB designed the Taktisches Kampfflugzeug 90 (or TKF-90), the first design of an unstable delta canard which promised unmatched maneuverability. Since Germany could not afford to develop the aircraft all by itself, collaborations were started with both Dassault and BAe, so that French and British engineers could learn of the advantages of this layout.

MBB TKF-90 concept (picture source)

First, BAe collaborated with MBB and joined the TKF-90 design, resulting in the European Collaborative Fighter proposal, only to continue on their own with two delta canard designs of their own, P.106 and P.110. P.106 had one engine and one vertical tail while P.110 had two of both, like the TKF-90. P.106 was rejected by the RAF, but went into a collaboration with Saab and eventually became the JAS-39.

To be fair, the first company to build and fly a closely-coupled delta canard was Saab with their Saab 37 Viggen. Saab has a long history of innovative work, beginning with ejection seats in 1942 and sweptback jets in 1948.

Saab 37 Viggen (picture source). In contrast to the TKF-90 it was an aerodynamically stable layout.

Meanwhile, MBB collaborated with Dassault in the Future European Fighter Aircraft (FEFA) program, so the French side learned of the advantages of a delta canard. Eventually, the French wanted less air-to-air capabilities and a smaller aircraft for better export chances, and the remaining FEFA partners continued in the European Fighter Aircraft (EFA) program which resulted in the EF-2000, while Dassault went it alone with the Rafale.

The EF-2000 is hampered to this day by this heritage. Its wing area was decreed by Maggie Thatcher and Helmut Kohl to be no more than 50 m² when a 60 m² wing would had resulted in a much more capable design. Next, the British engineers insisted on a straight leading edge, ignorant of the fact that only a cranked delta would provide good post-stall pitch characteristics. They also refused to accept a faceted design, and the German side could only rescue the "smiling intake" in order to reduce the radar cross section of the EF-2000 somewhat.

"Smiling intake" of the EF-2000 (picture source). The curved contour avoids corner reflections of electromagnetic waves.

And don't get me started on the odd location of the airbrake: On the center fuselage where it is least effective at high angle of attack and will blanket the single vertical tail. Designed by a committee with too many British engineers.


Is it possible to get a list of Cl/Cd values for various NACA Airfoils?

Perhaps the most important resource for airfoil data is the NACA (the predecessor of NASA) Report No.824 Summary of Airfoil Data by Abbott, Von Doenhoff and Stivers.

This report contains the description, generation and experimental data like variation of lift, drag and moment coefficients with angles of attack for a number of NACA airfoils.

You can also see NACA report No. 460 The Characteristics of 78 Related Airfoil Sections from the Tests in the Variable Density Wind Tunnel by Jacobs, Ward and Pinkerton.

Also, Aerodynamic characteristics of a large number of airfoils tested in the variable-density wind tunnel by     Pinkerton and Greenberg.

These are similar to the first report, but older.


What are these two tail elements of the Avro RJ100?

The one behind is an aerobrake. The tail opens up to increase drag. It is much better seen in this Wiki image:

The one in front looks instead like the APU exhaust.


Are there certain areas where a pilot can jettison his/her external fuel tanks?

This depends where in the world you are, over civilian US territory military planes chose to operate under the FAA FAR's (although they are not explicitly legally required to), as such its pretty cut and dry

  Sec 91.15 Dropping objects.

  No pilot in command of a civil aircraft may allow any object to be
  dropped from that aircraft in flight that creates a hazard to persons
  or property. However, this section does not prohibit the dropping of
  any object if reasonable precautions are taken to avoid injury or
  damage to persons or property.

Elsewhere in the world the rules may vary. There may also be rules about dropping tanks over open water due to their being residual fuel in the tanks.

This question covers what happens to them after they are dropped.

This thread would indicate that they are actually not dropped all that often.


Is VOR identification automated in modern avionics?

Modern air transport and bizjet avionics do decode the audio ID and provide it digitally on the data output bus. This data is displayed on the Nav display or RMI (depending on Mode) along with the frequency. It's not as common for general aviation radios to have this capability.

VORs that comply with ARINC Characteristic 711, VOR MB Receiver, output the ground station ID in two ARINC 429 Labels.  The first and second characters will be in Label 242.  The third and fourth (if there is a fourth) characters will be in Label 244.  Characters are coded in ISO 5 format.

Since all modern radios are DSP based, detecting and decoding the audio tones is a fairly straightforward process.  The radios also provide an analog audio output, so the crew can select the VOR radio on the audio panel and listen to the Morse code if they desire. (I'd be surprised if you found a pilot that did that routinely.)

ILS is similar. The ILS ID is contained in Labels 263 and 264.


Does a pilot need clearance to enter the traffic pattern?

The US AIM (Aeronautical Information Manual) says:

  When necessary, the tower controller will issue clearances or other information for aircraft to generally follow the desired flight path (traffic patterns) when flying in Class B, Class C, and Class D surface areas and the proper taxi routes when operating on the ground. If not otherwise authorized or directed by the tower, pilots of fixed-wing aircraft approaching to land must circle the airport to the left. Pilots approaching to land in a helicopter must avoid the flow of fixed-wing traffic. However, in all instances, an appropriate clearance must be received from the tower before landing.

(AIM 4-3-2-b.)

(AIM Fig 4-3-1)

So it is mandatory to receive a landing clearance, but if traffic flow doesn’t demand it, there is no need to fly the traffic pattern. The controller basically has a lot of freedom here, but the standard is to get instruction to join it, even if this means to join a long final.


How was the endurance test in the Cessna 172 legal?

Regarding flight time, duty periods, or rest requirements, no current regulations would have specifically imposed limitations on this flight. This flight would have been operated as a private flight under 14 CFR 91 under today's regulations.

The flight, duty, and rest requirements are specified only for certain commercial operations including airline, charter, and fractional. Flight instruction is also generally limited to 8 hrs in a 24 hr period. Paid pilots routinely fly 12-14+ hours in a day, including in certain patrol activities and in flying private jets.

Refueling is not generally restricted by FAA aiation regulations in a way that would specifically impact this operation. As with the flight time concern, the catch all "careless and reckless" regulation might apply first.

For some of the same reasons that the crew flight time was not restricted, many of the maintenance requirements such as 100 hr inspections, would not be required of a private flight. However, the 100 hr seat rail inspection AD would be problematic today.


Accounting for torsional forces during wing load tests

You would have to calculate the torsional loads for a critical torsional loading case such as full aileron application at limit load, and distribute the sand bags chordwise to produce the calculated spiral loading.

That's quite an analytical task and is rarely done when the skin thickness/stiffness required for good aerodynamic qualities and flutter resistance is usually quite a bit more than the minimum required for adequate torsional stiffness to resist flight loads. So it kind of takes care of itself anyway and can be covered by analysis with suitable fudge factors, like most of the other load cases on the airframe.


What was the first supersonic wind tunnel?

The world's first supersonic wind tunnel started operating in National Physical Laboratory in Teddington, England in 1922.

It basically used a pressure tank upstream, which was used to generate supersonic flow in a cross section of 20.3 mm, which was used to study projectiles.

From the book Aeronautical Research in Germany: From Lilienthal until Today:

  During the same year, the National Physical Laboratory (NPL) in Teddington/England started operating, for the first time ever, a supersonic wind tunnel based on the pressure storage principle ...


What are the wings and fuselage of an airliner made of?

Most modern planes are made mostly of aircraft aluminum. Or at least are skinned in aluminum. The spars and cross members may be made of other materials but I am under the impression they are mainly aluminum as well. Generally high stress areas like wing/fuselage joints may be made of more rigid materials like steel. Aircraft Spruce provides a nice break down of the various types of aluminum here. This answer to a similar question provides a nice break down.

As the technology gets better and the facilities grow in both scale and ability, composites like carbon fiber have found their place in planes like the 787. Here is a break down for the 787

(source)


Runway Number Landing and Departure Left Traffic Question

There is a misunderstanding here. It is incorrect to say

  runway 36 is north end of the runway

Runway 36 is the entire runway, with traffic moving to the north (i.e. facing about 360 degrees, magnetic).  Runway 18 is the same north/south strip of pavement, with traffic moving to the south (i.e. facing about 180 degrees).

If you're lined up ON runway 36, you're at the south end of it, facing north.  If you're on final for 36, you're south of the runway, pointing at it -- again, facing north.

If you are taxiing on the airport surface and need to cross that runway somewhere in the middle, it is correct to be cleared to "cross runway 36..." or to "cross runway 18..." or even to "cross runway 18/36...", typically followed by the taxiway you're to use: "... on taxiway Alpha."  If there is no direction associated with the use, people typically refer to "Runway 18/36" in order to be clear, although sometimes you'll hear only one designation used.  Either way works in that case.

The "Approach End of runway 36" is the end of the runway that you first cross on approach, so the south end.  The "Departure End of runway 36" is the end that you cross after having departed on that runway -- so the north end.  And, the "departure end of runway 36" is the same end of the same strip of pavement as the "approach end of runway 18".  Which description is used depends on context -- i.e. if runway 18 is active (i.e. aircraft are arriving from the north & departing to the south), then controllers are more likely to talk about the approach or departure end of runway 18, than to refer to things in terms of runway 36.


What is the difference between Bell AH-1Z Viper and Apache Longbow in terms of role?

In terms of role, there is little difference between these two helicopters. Both are attack helicopters used for close combat and anti-armor. They area also capable of carrying almost similar weapons systems and combat commanders can use either of these for the same mission based on their availability(though this will depend on the compatibility of communication equipment)

Bell AH-1Z is development (albeit with significant upgrades) of  Bell AH-1, the first attack helicopter of US army.

After AH-1, the US army decided on a dedicated attack helicopter (AH-1 was developed from UH-1 transport), which led to the AH-64 Apache.

AH-64D Block III Longbow is an advanced version of Apache with the Longbow fire control radar. It is under use by a number of countries apart from US Army.

The AH-1Z Viper, however, is used only by the USMC.


Do airlines staff extra crew members when disabled persons are check in?

In almost two decades of flying for airlines, I've never seen it done, and never heard of any program to facilitate such staffing.


Why fuel left/right when C172 is secured?

It's pretty much to limit imbalance when parked on a slope, and if the tanks are full, stop fuel from the high side tank from forcing fuel out of the low side tank's vent or seeping out the fuel cap if it isn't completely fluid tight.

On the '68 Cardinal I used to own, the vents went straight to the wing tip on each tank's side.  If parked on a side slope with fuel on both and full tanks, you might end up with a third of the high side's tank volume on the ground under the left wing tip (later they were cross vented to prevent this).


What is the bend in the tip of the blade of the new Black Hawk?

It is blade sweep, used to delay compressibility effects at the rotor blade tip. From Leishman:

  The blade tips encounter the highest dynamic pressure and highest Mach numbers and strong trailed tip vortices are produced here.

Blade tip designs can get quite funky, but the UH-60 tip has a relatively simple straight sweep. Again from Leishman:

  The amount of sweep is usually kept low enough (< 20º) so that there are no inertial couplings introduced into the blade dynamics by an aft centre of gravity or by aerodynamic couplings caused by a more rearward centre of pressure. A constant sweep angle offers simplicity in design and construction, but may result in higher than desirable aerodynamic torsional couplings because of the rearward location of the local centre of lift.

So by delaying compressibility effects in the forward going blade, the helicopter can fly at a higher maximum speed.

  Could this be used on airplane propellers?

It could, and it is being used. This company offers swept blade propellers as an upgrade for the King Air series. They look a bit different because the sweepback for propellers is best started at quarter chord.

And the A400 uses swept blade propellers as well.

The simple sweepback on the helicopter rotor is a trade-off between aerodynamic efficiency and production costs. The same trade-off allows for more complicated propeller shapes, such as in the Wiki article for scimitar propellers.


Do ATC displays show the target altitude that the pilot has set in the autopilot?

Yes, our radar is indeed capable to display data of the Mode S Enhanced Surveillance Transponder like Selected altitude, IAS, Mach Number, Heading and more.
After issuing a climb/descend clearance and entering it into the sytem it would also warn us if the selected altitude is different from the cleared level.


How are Victor airways defined and numbered?

The general rules for this are in FAA Joint Order 7400.2K, Procedures for Handling Airspace Matters. Chapter 20 describes when and how air routes are defined and designated, although it doesn't go into much detail about some things.

For example, the instructions on when to create a route are fairly general:

  20-1-3. WHEN TO DESIGNATE AIR NAVIGATION ROUTES

  ATS routes should be designated to serve en route operations when:

  a. The route is predicated upon NAVAIDs that are suitable for
  inclusion in the system.

  b. The benefits of the designation should outweigh any adverse effects
  to other airspace users, and:

  1. The route is a normal extension of an existing airway; or

  2. Users will benefit from charted information pertaining to navigational guidance, minimum en route altitudes, and changeover
  points.

Similarly, although there are some clear rules for NAVAID spacing, it doesn't tell you why a route would follow certain ones and not others:

  20-3-1. NAVAID SPACING

  a. VOR Federal airways are based on NAVAIDs which normally are spaced
  no farther apart than 80 NM. They may be based on more widely spaced
  NAVAIDs if a usable signal can be provided and frequency protection
  afforded for the distance required (see Order 9840.1, U.S. National
  Aviation Handbook for the VOR/DME/TACAN Systems).

The naming convention is in 20-1-5:

  20-1-5. ROUTE IDENTIFICATION

  Dual designation of ATS routes must be avoided. All alpha-numeric ATS
  route identifications must be assigned by Airspace Regulations and ATC
  Procedures Group as follows:

  a. Identify ATS routes based on L/MF NAVAIDs by color names (e.g.
  Amber, Blue, Green, and Red) followed by a number designation.

  1. Designate those routes extending east and west as Green or Red.

  2.  Designate those extending north and south as Amber or Blue.

  b. Identify ATS routes based on VOR NAVAIDs as follows:

  1. Route lettering must be as follows:

  (a) The letter “V" will prefix low altitude ATS routes below FL 180.

  (b) The letter “J" will prefix high altitude ATS routes at FL 180
  through FL 450.

  2. Route numbering must be as follows:

  (a) Assign even numbers for those ATS routes extending east and west.

  (b) Assign odd numbers for those ATS routes extending north and south.

  c. Identify advanced RNAV ATS routes as follows:

  1. The letter “T" will prefix low altitude RNAV ATS routes below FL 180, and the letter “Q" for RNAV routes FL 180 and above.

  2. Route numbering must follow the guidelines detailed in paragraph 20-1-5.b.1.(a) and b.2.

  d. Route segments must be listed from West to East for even numbered
  ATS routes, or South to North for odd numbered routes.

Many airways don't follow that numbering convention exactly, at least on certain segments. For example, V67 is more or less east-west between the GHM and SYI NAVAIDs although overall it's mostly north-south (from ENL to GQO). I assume that as the number of routes increased, they became longer and less consistent, possibly to avoid creating too many total routes: it looks like the lower-numbered routes are often more 'correct' than higher-numbered ones.

But just like with a road, even if it's clear why the road exists (I can see that people want to drive from A to B) it may not be clear why it follows the exact route it does (why does the road go north of that hill and not south of it?). All those 'small' decisions were made by the person who designed the route and there's probably no way to know them all.


Why is the available power in propeller engine is almost constant for every velocity?

It is a gross simplification, assuming a constant speed prop.  If a fixed pitch prop, it is non-linear.  Even with a constant speed prop it is not exactly linear.

Lesser factors for power available are the angle of attack/angle of incidence, which will change with airspeed, assuming level flight.  Ram air is also a minor factor on some engines.

The diagram you show is a simplification meant to show you that the power is the same, regardless of airspeed, but in reality it varies.  How much? I can't say for certain in general, but on one aircraft I collected data on, I recall it varying about 6% in the 20 knot window we were looking at.  And to be clear, that was power converted to thrust, not simply power plant power.


How/Where can I get additional weather information for flight planning?

In Europe, several national meteorological services provide additional info (sometimes on a paid basis). Some other services cater e.g. especially to glider pilots. Examples:

http://www.flugwetter.de/ ($)
DWD - Deutscher Wetterdienst Luftfahrt  (free)
http://www.meteoschweiz.admin.ch/web/de/services/aviatik.html ($)
http://www.nzz.ch/wetter/thermikprognose/ (free)
http://wetter-jetzt.de/  ($)
...

There are also a number of private websites run by clubs and/or enthusiast pilots, e.g. http://www.schaenissoaring.ch/wetter_berichte.cfm?SelectedMenuID=154 or http://www.alpenstreckenflug.de/wettera.htm which offer excellent (curated) information, sometimes on very special conditions like mountain waves etc..


Does filing a flight plan with Garmin Pilot activate ACAS and SE-SAR for my inReach?

SE-SAR and ACAS are only available for flight plans that are either filed directly through 1800wxbrief.com or through an app that's linked to your Leidos account (1800wxbrief.com > Account > Service Provider Authorization).
Garmin Pilot isn't on the list of known service providers, so FSS won't be able to match your flight plan with your online profile... meaning these services won't be activated.
Some apps (like Foreflight) have their own built-in ACAS feed, separate from 1800wxbreif.com's SMS-based interface. If your app has that, it would receive ACAS messages directly via push message. Unfortunately, Garmin Pilot currently doesn't have this feature.
See also this related question:
Will Lockheed Martin Flight Services send me ACAS, EasyActivate™, and other text messages if I file my flight plan through ForeFlight Mobile?


Does the weight of the battery count as "fuel" in a battery powered ultralight?

The jury (i.e. FAA) is still out on this question as of early June 2014.  FAA has indicated it will not give a gasoline "fuel allowance" to be credited against weight for batteries.  Given that fuel weighs 6 lbs. per gallon, or 30 lbs. for the maximum legal gas an ultralight can carry, it would be a somewhat negligible, but certainly welcome, allowance for would-be electric manufacturers.

One company, Chip Erwin of AeroMarine, has imported a barebones ultralight motorglider based on the Goat towed ultralight glider.  It's called the Zigolo, and carries batteries enough for 30-40 mins. of flight, without exceeding the 254-lb. weight limit of the part 103 category.

In time the FAA may well decide to grant the allowance.  It's still not going to amount to much more time, maybe 10 minutes given current battery energy density, which is a fraction of the energy density of gasoline, but research into electric storage is at a feverish pace worldwide.

Look for sport, then commercial electric aircraft, within the next 5 to 10 years.  Several electric single and two-seat electrics are already flying.  The Airbus ducted fan, recently ballyhooed as the first electric aircraft, which it certainly isn't, is a promising look at one way commercial electric applications might come to market.


Why then don't aircraft fly even higher, for even greater efficiency?

Some do (or have in the past) but very high altitudes present their own issues. Historically the Concorde cruised anywhere from FL550 to FL600 and was actually allowed to climb and descend at its discretion up there since they were well clear of any traffic. However the increase in pressure differential on the airframe as well as supersonic flight meant the airframe saw much greater wear and tear per cycle than its lower altitude friends.

At some point you get near the coffin corner a point at which, even if you have enough thrust your stall speed exceeds your critical mach number (effectively your wing can't work right). The U2 spy plane is capable of flying right on this edge.

One of the big practical limiting factors is also the rapid descent requirement for airframe certification. The FAA requires that in the event of a depressurization the aircraft can get down to 10,000 ft. (no oxygen required altitude) in 10 minutes as discussed here. The higher you go the faster the emergency descent needs to be, eventually this becomes an engineering issue and the airframe becomes the limiting factor since you don't want to exceed Vne in the dive.


Is it OK to use foam for the ribs of an ultralight's wing?

The foam is used to take small shearloads and support the primary structural element in absorbing tension and compression loads.  The wood rib has the primary compression and tension members in the capstrip, with the diagonals absorbing shear loads, converted to compression and tension loads along the legs of the truss. On a foam rib, if it is a standalone rib not connecting to a stressed skin, you need to have a structural capstrip material, like wood or fibreglass because the foam only has strength when the loads are distributed over a large area.  The foam itself does the job of the diagonal members in holding the caps in place and absorbing shear forces in the rib.  Some ultralights have a foam rib core with an aluminum cap strip bonded to the edges to do this.

If the foam rib is inside a stressed skin wing, the stressed skin is effectively the cap strip and the foam can be bonded directly to it.  Because the foam isn't very strong it requires a large number of foam ribs, closely spaced to properly support the stressed skin.


Which jet airliner types have had the fewest accidents per million departures?

All newly developed types have zero number of accidents, at least immediately before the maiden flight.

Hence the actual safety of the type cannot be derived just from the number of the accidents. The number of flights flown must also be taken into consideration. For instance, Concorde used to be the absolutely safe (zero accidents) for many years (1969 - 2000), then it became comparable to other planes just because of the only crash of the type.

This source contains the table that includes the number of airliners operating, not just the number of accidents. It is very incomplete but looks like Boeing 777 and ERJ 135/145 may not be a bad choice while Boeing 737 'Classic' does not look equally good. The safety of this type has been discussed separately.


Discs, blisks, and blades are all very expensive components so if they can be salvaged through repair and overhaul programs they usually are. According to this article overhauling a high pressure turbine blade from the CFM56-7BE is 80% cheaper than producing a new one, which is roughly inline with my experience. The actual overhaul process will vary depending on why the item was taken out of service and what condition it is in. There are many companies out there that are built around overhauling various components of gas turbines and many OEMs like RR & Siemens have programs or side businesses for it.
Compressor blades
For a compressor blade a full inspection is required to check it still meets the original specification. This would include at a minimum:

Visual inspection for nicks, scratches, or any other damage
CMM inspection (or equivalent) for shape and size
Weight and balance measurements

If there is any damage to blade it may be possible to repair them through welding or other approved methods depending on the location and severity, but I've never actually come across any company doing so for compressor blades, they're normally discarded.
Turbine blades
All of the above also applies to turbine blades, except that they often can be welded and repaired if they're cracked. They're much thicker and sturdier than compressor blades. If the blade is coated, (pretty much all modern blades are) the coating will have to be removed, replaced and re-inspected for thickness. There will also be a check that all the cooling holes are clear and functional.


Which design method is used for super critical airfoils?

Critical speed or Mach number is the speed at which the speed of sound is locally reached somewhere along the flow around an airfoil. A supercritical airfoil can tolerate operating speeds slightly above the critical speed (hence the name), which means that a pocket of supersonic flow will show up, most likely on the upper surface. What qualifies an airfoil as supercritical is that the recompression does not need a shock, but can be done shock-free for a small lift coefficient range by clever shaping.

See this question for more.

Calculation of a supercritical airfoil is best done with a computer program which models the flow conditions around Mach 1 faithfully. Once such program would be TSFOIL. The picture below shows one result for the BACJ airfoil at Mach 0.8, and you can see that the speed on the upper surface reaches Mach 1.3.


Is there any combination of two airports that are connected via taxiways?

There are numerous joint use (commercial/military) airports with separate terminals/ramp areas. There aren't many where there are two connected fields. The only one I'm aware of is Naval Air Station Whiting Field near Milton FL that has two operational fields with separate identifiers.

There is NAS Whiting Field - North. ICAO: KNSE and
NAS Whiting Field - South. ICAO: KNDZ

The two fields have a central support base area between the two fields. There is a single taxiway that connects the two fields around the east side of the support area.


How might one start a new logbook for an engine that had one lost?

One way to get a new engine logbook is to send the engine for a factory overhaul.

Your engine will be regarded as a usable core, and will come back with all tolerances within "as new" limits and a new logbook.


What are the potential threats of having the landing gear dirt from mud in a rectractable landing gear airplane?

The main issues would be mud interfering with the uplock/downlock mechanisms, the switches that control indication of the function of those mechanisms, the brakes, and wheel balance.   Mud + freezing temperatures = worse.  Gears won't lock down, or they lock down but you don't get an indication, or the wheels freeze and skid on landing and blow tires, or mud in the wheel rim makes the wheel vibrate all to hell on takeoff.

There is usually enough robustness in the design that it can tolerate some contamination (obviously, it has to have some ability to take on mud on takeoffs from dirt runways), so as with most things, it depends how much when you look at it.  A little bit of mud spray here and there, not too big a deal.  Mud caked on on the wheels, brake calipers, any of the mechanical bits in the wheel well, that could interfere with moving parts, it should be removed before flying by hosing it off.

The mechanic who maintains the airplane you are renting would be a good person to ask about how to judge when mud contamination is excessive.


Is it possible to perform the Lomcovak manoeuvre in a C152 aerobat?

The list of approved maneuvers is in the POH, and I'm sure the Lomcovak is not listed. If you are willing to do unapproved maneuvers, the issue is that because the aircraft tumbles rather than flies in this maneuver you have a few things to worry about: it starts with an outside maneuver, it is inverted, and the exit requires a high-speed dive which will exceed Vne or the +6g the 152 Aerobat is rated for.


How should I interpret this raw SID data from the FAA?

To your first question, some SIDs exist to provide a basic set of information that will almost always be given as part of a clearance, rather than a path to fly. This allows a controller to not have to state that part of the clearance verbally, saving time and confusion.

On the Bellevue Three Departure from KRNT, the departure is as follows:

  Climb heading 350°, maintain 3000, expect RADAR vectors, expect filed altitude within 5 minutes after departure.

There's no location to code in the procedure (other than that from the Lost Communications section) so while the SID exists, there's not much to code for an automated system to interpret.


Would turbine blade twist change if all conditions except the density of the fluid remained the same?

A classic comparison would be boat props vs aircraft at various RPM.  A higher density (viscosity) fluid would put more stress on the blade tips, hence shorter and more robustly built blades.  The amount of twist would depend on loading of props and would include chord length.  A tapered prop may have a different twist from an untapered or reverse tapered.  Diameter and RPM are also factors in loading.  And, as in aircraft, twist would also play a role in cruise efficiency or acceleration from standing still.

So there is no one rule about this going from one fluid to another (rare application).
Variations of design and performance in one fluid are much more common.


What are the different types of procedures for starting a fuel injected engine?

The key thing that makes FI engines different is how you prime them.  You are using the pressurized fuel injection system itself to do the priming instead of pumping fuel into the intake ports using a syringe pump primer.  You do this by turning the boost pump on to pressurize the system and setting the mixture to rich, which on a crude-ish mechanical FI system like the continuous flow systems used on airplanes, just starts spraying fuel in the injectors as long as the mixture is in, whether the engine is turning or not.

Two main differences from a carb:

The priming procedure is one of timing using mixture, not counting pump strokes.
You start the engine with the mixture in idle cutoff (because with the system pressurized and the mixture not at idle cutoff, it'll be spraying fuel in continuously and you'll soon have a little pond of fuel under the cowl).  You don't advance the mixture until the engine catches.

As far as hot/cold starting goes, the basics are the same as a carbureted engine, more prime when cold, less prime when warm, no prime when hot.  So for a cold engine that uses 6 strokes of a manual primer, with the FI engine it's pump on and mixture rich for some period like 5 seconds, then back to idle cutoff before you crank it.  On a warm engine that uses 2 strokes, the FI version might be 1-2 seconds.  You're doing the same thing, just with a different process.

Because it requires careful timing with prime and then keeping the mixture at idle cutoff until start, it's easier to screw it up and flood the engine by messing up the timing, or to be late with the mixture after it starts and it goes and dies on you.  So they can be a little bit fussy until you get the hang of it.   If you're bush flying on floats in something like an injected C-185, where you need to be able to know you can start right now once you push off from the dock, getting it right really becomes important and hilarity will often ensue (drifting toward rocks or moored boats in the breeze as you scream and curse) if you don't.

At the other extreme, because the injector distribution system is normally on top of the engine where all the heat collects, when an FI engine is hot on a hot day it can cause vapour lock in the fuel distributor and lines (even with the very low Reid Vapour Pressure of avgas) and they just don't want to start at all until the cowling cools down a bit.  Not realizing this, you may decide that it needs priming, so you start priming when it doesn't need it and things have cooled down enough for fuel to start to flow again, and now it still won't start (the raw fuel smell with be a clue).  They can be frustrating beasts.


When the rudder is deflected, it creates a "lift" on the vertical tail due to additional camber. This "lift", when viewed from the airplane perspective, is a side force opposite to the direction of the rudder deflection. Since the centre of pressure of this side force is aft of the centre of gravity, it generates a net yaw moment on the airplane.

  For example, a right rudder deflection generates a left side force, which generates a nose right yawing moment, pulling the aircraft nose right.

Since the side force is relatively small in the big scheme of things, the airplane motion is essentially unchanged. As soon as the airplane nose begins to yaw, the airplane begins to have finite sideslip against the incoming airflow. This sideslip generates a side force that opposes the rudder force (from an increased airflow incidence against the vertical tail), as well as a yawing moment that opposes the yaw moment from rudder (i.e. a restoring moment).

  For example, a right rudder generates nose right yaw motion, which creates a sideslip that produces a nose left yaw moment.

For a finite rudder deflection, the airplane begins to accumulate sideslip, until such a point that the restoring moment balances out the rudder moment.


Do rivets on airframe need special sealant to be airtight on pressurized airliners?

I banged rivets on a production line long ago.  The countersunk rivets used in the pressure hull depend on expansion of the shaft, but some rivets also have a slightly larger radius where the shank flares out into the head compared to a standard flush rivet, which forms a tighter seal when the rivet is set.

You don't actually apply sealant to the rivet itself. The sealant, which is a crazy-sticky goo stuff (not epoxy, it cures to a hard rubber consistency), gets everywhere when you are shooting rivets on the pressure hull because the faying surfaces (the overlapping metal to metal surfaces) are coated in sealant before assembly, which gets in the rivet holes (the sealant is a pain in many ways; it acts like a lubricant if it gets on the skinny end of the rivet and makes it easy to dump the rivet over when you buck it).

Carbon fiber panels are usually joined to metal with bolts or Hi Lites or similar rivets, with some sort of insert or doubler of stainless or titanium in the carbon to distribute the loads.  Sandwich floor panels for example, typically use a titanimum insert bedded into the sandwich with epoxy resin, through which the fastener goes.  Carbon against titanium is fine, but if joining carbon to aluminum, you MUST have an insulating material to separate them because they live at opposite ends of the galvanic scale.  Carbon touching aluminum = lots of corrosive fun.


If all aircraft were TCAS-equipped, how would this change ATC routines?

Think of the ATC system as the road network, traffic lights, road signs, and police.  TCAS is a standalone device in your car that warns you the guy coming at right angles to the intersection in front of you is going to run the light and T-bone you.  Whether you have such a device or not, it doesn't change how the traffic control system work.

TCAS has been around for 40 years and it didn't change the way traffic is controlled because it's a stand alone system that only impacts the crew on board the airplane that gets a TCAS warning.

TCAS is mostly to protect big aircraft from incursions from small aircraft, that are hard to see and that ATC can't always prevent. What got it going in the first place was the famous crash in LA where the DC9 on an approach overran a C-172 back in the late 70s.


What is the correct way to get established on the outbound track on this approach?

I do not have a specific ICAO reference. By my interpretation of the chart, you can approach the airport at any assigned altitude above 2300 feet MSL from your specified East direction. Just as long as your aircraft stays between the 71° radial clockwise to the 215° radial of the VOR. But, you would have to be above 4900 MSL to intercept any part of the instrument approach. Once you are established on the approach, you can drop down to the appropriate designated at-or-above altitude marked on the approach. If you are joining the approach at the LCA VOR, you would enter the hold, either climbing or descending until you reach an altitude where you can safely descend down to 1500 feet MSL during the teardrop course reversal. Remember, you have to remain at or above 4000 feet MSL until passing the VOR when leaving the hold. This will be your Minimum Holding Altitude as well as your Minimum Crossing Altitude at the LCA VOR.
If you have already been cleared for the procedure at LCA, you would just have to make your radio call once you reach the VOR for the hold, and again at the VOR when you leave the hold (if one is necessary to gain/lose altitude).


Which hand do fighter pilots use for the control stick?

Most fighter pilots, regardless of their handedness, use their right hand to fly the stick, and their left hand to move the throttle(s)/PCL (Power Control Lever). This is just how most fighter cockpits are set up, with the power on the left side.

The sticks are also not really usable for a left hander because a few of the buttons would be inaccessible with a left hand on the stick. In some cases (like the F-16), the cockpit uses a sidestick layout, with the stick on the edge of the cockpit, rather than in between the pilot's legs.

So no, it would not really be possible for left-handed pilots to fly with their left hand on the stick for long periods of time (I will note, that if you need to select something on the right side, most will hold the stick lightly in their left hand for a brief second, actuate the item with their right hand, and then switch back) unless the entire cockpit were redesigned, which is just not worth it.


Why could a Rotax 914 light aircraft lose power at 7000 feet?


Under EASA rules, what do I need to do to be able to perform aerobatics?

The appropriate rules are in FCL.800 Aerobatic Rating

A licensed pilot may not undertake aerobatic flights unless they hold an Aerobatic Rating
40 Hours of Flight Time (or 120 launches for sailplanes as PIC) completed after issue of respective license
Aerobatic Training course including theoretical knowledge and 5 hours or 20 flights
Aerobatics must subsequently be flown in same category aircraft as used for rating
No revalidation/renewal requirements
Be issued a certificate of satisfactory completion of the instruction for the license endorsement

So there is no specific license to be obtained, however there is a specific rating, which is just an endorsement in your logbook.

Its not clear from the documents that I've read that formation flying qualifies as aerobatics. Some other countries don't consider formation flying an aerobatic operation.