How are wooden aircraft protected from lightning strikes?

By not flying through thunderstorms. For a small aircraft, the lightning is not the most hazardous part of a cumulonimbus (Cb) cloud system. Mature Cb clouds have huge updrafts underneath them, which can cause enough turbulence to upset most aircraft. Heavy rain and hail is also commonplace underneath Cb clouds. Even the rain can be heavy enough to damage wooden propellers and any components on your leading edge (such as the leading-edge slats found on the Tiger Moths I fly). Hail can put holes in your canvas, which are expensive to repair - if you manage to get the aircraft home at all. This turbulence and rain persists for a much longer period and across a wider area than the thunderstorm itself.

For these reasons, the chief protection against thunderstorms is by training and procedure: student pilots are taught to avoid Cb clouds when they're visible, and to plan flights to avoid areas where Cb are forecast. Weather forecasts and reports specially call out Cb clouds to help with this, and ATIS messages often warn of "cumulonimbus cloud in the vicinity of the aerodrome".

Protecting a wooden aircraft specifically against lightning is not hugely worthwhile, because it's unlikely to be able to stay in the vicinity of the Cb cloud for long enough to be at risk of a lightning strike. It just wooden happen.


Why can’t more older 737s be retrofitted with more newer winglets?

Winglets change the spanwise loading on the wing. By increasing the effective span of the wing, lift is increased towards the tips of the wing. With more lift there, you get an increased bending moment on the wing.

All this means is that you can't just put winglets on or change the ones you have. You must retrofit the structure of the wing which is very expensive and requires significant downtime. It also adds a weight penalty which decreases the benefits of the winglet.

For example, on the A320, which was already wingtip fence equipped, going to the sharklets requires removing the skin and reinforcing both the tip and the center wing box near the fuselage. This takes the aircraft out of service for 15 days and involves, I've heard, in excess of $1 Million in parts alone.

On the 737, the list price for the blended winglets is $1.06 Million.

So the answer for why is because it often is not economical to do such a huge modification given the limited lifetimes on older models.


What area is used to determine the horizontal and vertical tail volumes of a vtail?

Depends on what the tail volume is used for.

For control authority and trim: Use the projected area.

For flight dynamics and damping: Reduce that by the cosine (horizontal) rsp. sine (vertical) of the V-angle, in your case multiply the projected areas by 0.707.

The control effectiveness of a control surface is proportional to the cosine of the V-angle, but the damping characteristics go down with the square of the cosine.


A slip is uncoordinated flight and this shifts the effective gravity vector you experience.  Passengers in the back are also at a disadvantage without a visual horizon in front of them.  This can induce a mismatch between what the passengers can see versus what they are physically experiencing.  In some people this can cause discomfort and potentially vertigo.

Other discomfort can be psychological in nature that the airplane isn't behaving how they expect.  Passengers expect if a plane isn't turning that the wings are level.  If you are flying when the plane lands in a crosswind with a slight bank and touching down with one main gear, then the other main gear, many passengers will comment that the landing was incorrect because the main gear didn't all touch down together and the pilot was flying "sideways".  They don't realize the wind requires this technique and that the landing was in fact correct.  The perception of things not being right, however, can cause discomfort in some passengers.


How unique are waypoint names supposed to be?

The names are not globally unique and when entering the plan into the FMC, the crew should check the leg distance.  They are sufficiently far enough that the crew will see 1,812 miles instead of 135 miles.

Many FMCs will also only offer "sensible" choices and a deliberate action is required to select a "nonsensical" waypoint.

Often, a mistake in choosing the wrong waypoint will also alert them with a "not enough fuel" message, or an obvious gross error such as a total distance of 3,323 miles instead of the 756 miles expected.


Why don’t airliners have temporary liveries?

They do have temporary liveries. This is very common in wet lease operators, where an aircraft is flown for an airline during a peak period or when their planes are down for maintenance. Airlines want customers to feel they are getting the brand-name product they are paying for; they don't want customers to board a generic white jet.

An airplane will be painted and decals applied only for several months. Just like motor vehicles, 3M makes aircraft film wraps, including models specifically for short-term use.

It is also common to have a livery for a special event, say the Olympics. You can expect ANA's jet for the 2020 Tokyo Olympics to be returned to normal shortly after the Olympics are over. You can see Lufthansa and Egyptair dressed their planes up for the World Cup. Egyptair's photographic livery can only be done by printing onto a decal.

This video shows Alaska Airlines paint essentially an ad for Disneyland and the Cars movie franchise. They paint the simpler parts like the clouds and the large solid areas, but at 1:28 you can see them apply decals of the characters' faces. They say it took 29 days to paint. This is another video where they're simply applying a decal to advertise another movie.

So, no, there is no technical reason not to have a temporary livery and such schemes are done regularly. It's merely an issue of marketing and customer impressions.


What happens if full thrust is applied at cruise altitude for 5-10 minutes on a 787?

Autopilot flying straight and level

Upon reaching the VMO/MMO the A/P will be inhibited from trimming down any further, which will result in the airplane climbing at the VMO/MMO.

  Overspeed protection limits the speed to which the airplane can be trimmed. At VMO/MMO, the trim reference speed is limited by inhibiting trim in the nose down direction.

Hand flying straight and level

Pushing the thrust levers forward will result in a climb at the current speed due to the fly-by-wire design—only the trim buttons change the "trim reference speed".

  Once the column forces are trimmed to zero, the airplane maintains a constant speed with no column inputs. Thrust changes result in a relatively constant indicated airspeed climb or descent.

Source: Boeing 787 FCOM chapters 4 and 9.

Further reading:

What does the term "trimming" most commonly mean in aviation?
Why does overspeed cause structural damage or failure when limit load factors are not exceeded?
How does envelope protection work in Airbus vs. Boeing aircraft?
How does auto-trim work on fly-by-wire aircraft?


Why does the NASA X-57 need a "gust control system"?

It would depend on the direction of gust. High-aspect-ratio wings have a lower rate of roll. Thus, an upward crosswind gust that introduces a rapid uncommanded rolling action may not be sufficiently correctable by aileron deflection alone, and may require the asymmetrical application of thrust to increase the control surface authority and lift of the lower wing.


How does the Airbus ECAM / ND transfer work?

All this depends on the A320 generation. On early models all computations are done by the SDACs and the DMCs, and the switching corresponds to data switching in the DMCs, so the screen will display what it receives.

On later models all screens receive all data and on request they can display what you ask when you do the ECAM/ND switching.

In fact in latest models of A320 the displays switching possibilities are voluntarily limited just for conformity with earliest A320’s


Why was this commercial jet accompanied by small plane near Seattle?

It's a Fedex 777F N894FD in (probably) pre-delivery aerial photography/test flight accompanied by one of Boeing's chase aircraft.

After some maneuvers (shown below), the plane headed to MEM, Fedex's "SuperHub".

(Source)

The flight on flightradar24: https://www.flightradar24.com/2019-07-24/03:16/12x/FDX9032/2168b4b1 and flightaware: https://flightaware.com/live/flight/FDX9032/history/20190724/0215Z/KPAE/KMEM


Are there any privately owned V-22 Ospreys?

There are no 'private' Ospreys thus far (all are operated by USAF, USMC and JSDF)- the Bell Boeing MV-22 Osprey used by the US Marine Corps's HMX-1 presidential helicopter squadron:

  ... will conduct presidential support missions, which means these aircraft will carry presidential support staff and news media representatives travelling with the president," the USMC says. "The Osprey mission at HMX-1 does not include carrying the President of the United States."

so I'm not counting on 'luxury' interiors. When (and if) a civil version of V-22 is produced (or if the Japanese feel like selling theirs), you can buy it and make the interior whichever way you like.


Does ARINC 825 (Aviation CAN bus) follow the same protocol as automotive CAN buses?

Yes, the underlying CAN protocol is the same.  The 825 standard specifies some CAN IDs/priority scheme for standard purposes, similar to the ARINC429 label standard.  It also specifies certain CAN bit timing configuration, such as 1 sample per bit at 75% of the bit time, and re-synchronization jump width at 1 time quanta.  These are all settings in the CAN standard.

This datasheet provides some hints, but unfortunately being an ARINC standard there isn't much public information about the label and data structures.

Holt HI-3110 ARINC 825 compatible transceiver

If you connect a CANBus tool that supports extended ID's you should be able to see the CAN data.  The bus is comparable at a CANbus and electrical level.


Gyroscopes have two types of motion.

The gyroscope spins within its housing (usually at a pretty high speed).
The housing can change attitude within some limits.

The vanes aren't part of spinning gyroscope, but they are part of the housing (which can shift/rotate with respect to the airframe).  The vanes create a torque to change the attitude of the housing.

There is a youtube video with some animations that try to show this effect.


How are weather-related limits on arrival capacity determined?

ATC has to keep planes a minimum distance apart, and that distance increases as weather gets worse. You could fairly easily calculate from the required spacing in each case to get an expected arrival rate, but the real world never works exactly as planned. The numbers in that table have almost certainly been "adjusted" to make them agree with experience.


Is engine sync to avoid beat frequencies also a concern for jet engines?

Some aircraft with turbofans have an engine synchronization system for exactly that reason: reducing the beat resulting from different, but similar, frequencies for the two engines.

MD-80: The McDonnell Douglas MD-80 can synchronize its engines by EPR, N1 or N2 when the autothrottle is engaged:

  Engine Synchronizer System

  The engine synchronizer system automatically matches the N1 or N2 speed or
  EPR of left engine to match right engine. The system includes a three
  position (N1, OFF, N2) ENG SYNC selector, ENG SYNC ON annunciation, and control
  system with actuator to trim left engine fuel control. The pilot can override
  the system at any time with throttles.

  When the ENG SYNC selector is placed in N1 or N2, signals from the tachometer
  generators causes engine synchronizer system to trim left engine fuel control
  until left engine RPM (N1 or N2) matches right engine.

(MD-80 FCOM Sec. 18 Power Plant - General)
CRJ: The Bombardier CRJ-700/-900 can also synchronize by either N1 or N2 via the FADEC:

  N1 and N2 Synchronization

  In the cruise range, thrust is set to a specific value by the FADEC based on throttle
  position. Synchronization allows the FADEC to match the fan (N1) or the core (N2)
  speed of the two engines for noise reduction. Synchronization is selected by using the
  SYNCH switch on the engine control panel . The left engine is designated as the
  master engine and the right engine will be slaved to it.

  For N1 synchronization to be enabled, the right engine N1 must be within 1.5% of the
  left engine N1.

  For N2 synchronization to be enabled, the right engine N2 must be within 7.5% of the
  left engine N1.

(CRJ FCOMv1 chapter 20 Power Plant - Thrust Control)

As far as I know, no Boeing or Airbus aircraft has an engine synchronization system. Presumably, the beat is less of a problem for wing mounted engines since the passenger cabin is shielded from direct sound by the wings. For tail mounted engines, engine noise is more of a problem in the cabin.


How do Throttle control and Propeller control work together?

In a constant speed prop, the prop control lever basically changes the speed of the prop (it is not always running at the same speed as you indicate in your question, but rather once the speed is changed by the prop control lever, the governor keeps it at that speed). If power (or airspeed) is changed, the blade angle will automatically change in order to keep the prop turning at the same speed (within the limits that it is designed for).

Since adding power would normally increase the speed of the prop, the governor automatically changes the blade angle in order to keep it at the same speed.  The same is true when power is reduced or airspeed is changed.

Thrust is changed by engine power because, even though the prop is turning at the same speed, the angle of attack of the prop has been changed, which changes the amount of thrust.

For more general information about how a constant speed prop works, see this question and answers:
How does a Constant Speed Propeller Work?


What's the smallest 3-blade propeller for this motor?

You need the largest prop that keeps the tip speed below about .9 Mach, roughly 1000 ft/sec, so you want the largest propeller than can operate at that RPM at .9 mach.  Here's a tip speed calculator for larger propellers that should suffice.


Could any complications arise if the two FMCs are using different OPS programmes, i.e U10.7 and U10.8A?

It wouldn't work. The two FMC's need to communicate & stay in sync; that process requires the same OFP in both.


How and how often are the oxygen masks in the cabin checked?

There is a maintenance schedule to test the mechanism that causes the passenger masks to deploy(drop down). It is usually performed each 12 months. During this test, the masks themselves are inspected, any discrepancies found dealt with, and re-stowed in the little overhead box until the next scheduled inspection.


Why does the Yak-28 cockpit have two attitude indicators?

It's possible that the soviet attitude indicators are subject to tumble when operated inverted. the easy way to overcome this is to provide two instruments, one of which does not tumble when flying mostly right-side up and the other does the same for flying upside-down.

Soviet-era acrobatic planes had dual G-meters installed for this same reason. One was installed upside-down and registered negative G's while the other was installed right side-up and registered positive G's.


At what angle-of-attack (sideslip angle) would a symmetric vertical fin plus a deflected rudder have a lift coefficient of exactly zero?

Here are two links to Tom Speer's homepage. They show the performance of a couple of flapped airfoils. They aren't symmetrical, but it doesn't matter for what you are doing. What you want to look at is the change in the AoA between adjacent flap deflections.

For instance, it the first link, the there is a series for -3 degrees flap and one for 5 degrees flap. Holding the coefficient of lift constant, you'll see about a 4 degree difference in AoA. Thus deflecting a smallish 20% flap is about the same as rotating the whole foil by half as much.

http://www.tspeer.com/NACA23012/N23012wflap.htm
http://www.tspeer.com/NACA23012/N23012wflap.htm

For a 50% flap, it can be as much as 80% effective. See also Tom's analyses of wingsail performance with various sized flaps at the same site. These are symmetric foils, but you have to do some extrapolation to run the lift down to zero.

Tom worked for Boeing, and has worked on numerous high performance projects including the America's cup wingsails and landyacht projects.


I wear earplugs all the time flying in both pressurized and unpressurized environments, and have done it for many years.  Air pressure changes have no noticeable effect when wearing foam earplugs as the interface between the foam and ear canal is not totally air tight.   The silicone flanged ones made for airline flying have a tiny bleed hole in them (flanged ones are way too uncomfortable for me though).

If anything, on an explosive decompression, the earplugs would help by delaying the escape of pressure on the outside of the eardrum while the pressure equalizes on the inside through the eustachian tubes, which can take a second or two if you have to work your jaw to open them.

Put them in whenever you want and take them out whenever you want.


Where can I find the number of commercial jets that a country or airline purchases annually?

planespotters.net lists, for many commercial airlines, all their airplanes along with their delivery dates.

As for an authoritative source, you would have to look at the IATA or any other paying site such as airfleets.net.


Do landing planes brake with wheel-brakes or air-brakes or both?

Depends on how long the runway is.

If you have a 12,000' runway and your terminal is at the far end of it, you can roll out with no wheel braking and as little (or no) reverse thrust as you're allowed, and you'll be close to taxi speed by the time you're ready to turn off.  In that case, the brakes only absorb enough energy to get you from maybe 60-80 knots down to 20-30, since the drag devices lose most of their effectiveness by that point.

On the other hand, on a really short runway, you may be getting on the brakes immediately after touchdown, which means that the amount of time that you're dissipating energy due to drag (spoilers) and reverse thrust is reduced, and much less energy is lost that way.  So in that case the brakes get a great deal of your kinetic energy.

The case beyond that would be if you didn't use reverse thrust, your brakes would get nearly all of your energy, with only a small amount dissipated due to aerodynamic drag.


Simply put, a lot of airports, especially ones that are Class B (very busy), will have multiple control towers. Most of the time, there is a single operational control tower focused on departures/arrivals into the airport environment with one or multiple smaller ground control towers focused on ground movement area coordination. I hope this helps!


Why did WWII prop aircraft have colored prop tips?

The prop tips are painted for visibility, to show that the prop is turning. This is especially important when the aircraft engine will be running in close proximity to people on the ground, but is also helpful in alerting the crew of other aircraft that the engine is running, and the aircraft might be moving soon.

For visibility, the tip color should be in high contrast to the blade, typically white on black.

Some operators paint the prop tips in an alternating pattern for a strobe effect for heightened visibility. This is especially helpful when operating in areas where people on the ground may be unused to being around aircraft; the strobe effect is an attention-getter. A three bladed prop painted in this way might use a pattern of one, two, and three stripes, or two, three, and four stripes.

Here is an example of what this pattern would look like on a 206:

Source: own work

This is what the pattern on a Quest Kodiak looks like in motion:

Source: excerpt from original photo by Dave Forney


Is lift greater at the wing root of an horizontal wing,just like it's greater on a tapered wing

Well this is sort of definitional.

Generally speaking the idea of any sort of taper or shaping of the wing like the examples you posted above is to deliberately reduce the lift at the tips in order to reduce induced drag. In that case, no, the rectangular wing would be more even across the span - although there's all sorts of other effects that would likely come into play that would adjust that to some degree.

But really what you're asking about is the lift per span. If you really mean "is there more lift at the root" then the answer is "absolutely every time" for the simple reason that the lift force at the root is the lift force of the entire wing, whereas at the tip it's the force of only the tip. That's why the spars get thicker as you move in toward the root.


How do you sump fuel when it's raining outside?

AOPA has a good article about checking fuel:

  ... check the fuel caps and replace worn, brittle, or cracked seals
  that can allow rain to seep into the tanks.

You cannot be 100% that the fuel does not contain any contamination. If you risk that by putting the sample fuel back in the airplane (debatable topic) will add more water in the tanks, then simply don't do it.

I guess since many flight schools offer wet rentals, they don't want to waste a drop of fuel. But it is okay to do that, so that their aircraft and your life are safer.

Update

There are many arguments about putting sump fuel back in the tank. Many people say that a GATS Jar is there to capture the contamination and then you can put it back in the fuel tank. In Cessna training material, they use a container where you can put sump fuel. At many places, there is a fine for throwing it on the ground.

So in case of rain, the best option is to put in such a container. However, if it is raining that hard with strong gusty winds, I am sure taking care of sump fuel should not be your problem.


What is this device below the door of a 737 (and other aircraft)?

That is the outflow valve. The outflow valve allows air to leave the pressurized section of the fuselage. The aircraft's pressurization system controls the valve to keep the desired pressure, balancing the air coming in through the bleed system.

Source


What classes of aircraft require hydraulic flight controls?

Hydraulic flight controls are not mandatory for a specific class, but above some size and speed it will be hard to fulfil all certification requirements without at least adding some hydraulic boost.
Historically, aircraft used manual controls. With increasing size and speed, the forces went up and increasingly clever force reduction systems were invented to keep stick forces within limits.

On the first flight of the Messerschmitt Me-321 glider it was found that control forces especially in roll were way too high, so a second pilot with a second stick was installed.
The Dornier Do-335 or the Republic P-47 used a telescopic stick: At low speed the stick was short and could move through the full range of aileron deflections while at high speed it could be telescopically extended. This limited the motion range but improved the leverage of the pilot.
The English Electric Canberra used internal balances for the ailerons and a spring in the aileron controls to limit the stick forces. At top speed the control horn could still move through its full range but the achievable aileron deflections were only a few degrees - still enough for sufficient roll agility, however.

Ailerons have mass. There is a spring. Something that moves. Every engineer should think next: What about flutter? With more complex force reductions, the chance grew that something unexpected happens and failure modes multiplied. In the end, introducing hydraulics solved so many problems that de facto above a certain speed and size combination no other option makes sense.
I have worked together with Rockwell (formerly North American) on a two seat jet trainer; a size and speed combination that would have had manual controls 60 years ago. I proposed to use the same force reduction mechanisms that were used on the F-86, but in the end a hydraulic boost was selected. Why?

Nobody had any experience with manual controls anymore. After so many years, all F-86-era engineers were long retired or had passed away.
The North American archives had been thrown away years before, so no documentation was left on how to properly design a manual control system for that speed range.
The hydraulic boost system was easy to install, used standard components and was cheaper to design because everybody was familiar with the technology.

As I said before: Don't get me started on how exactly you can tailor roll stick forces - this will be a post that will be much longer than anything I have written here before.


Which FAR/AIM addresses Shortest Turn to Assigned Heading vs Runway Traffic Pattern?

The most important point is that if any ATC instruction isn't clear then you should just ask them to repeat or clarify it.

Having said that, turning in the shorter direction is stated in the FAA's Pilot/Controller Glossary:

  FLY HEADING (DEGREES)- Informs the pilot of the heading he/she should
  fly. The pilot may have to turn to, or continue on, a specific compass
  direction in order to comply with the instructions. The pilot is
  expected to turn in the shorter direction to the heading unless
  otherwise instructed by ATC.

In my personal experience, ATC almost always say left or right for heading changes if you're on an approach or departure, but sometimes leave it out if you're in cruise. That makes sense to me: the busier the airspace the more they want to make sure that you don't turn the wrong way.


How does contrail formation differ from turbofan to turbojet?

It appears that the higher bypass engines available today increase the contrail occurrence. From Influence of propulsion efficiency on contrail formation by Ulrich Schumann:

The  thermodynamic  analysis,  which  is  the  result  of first-principle  arguments,  implies  that  aircraft  and  engines, performing with a higher overall propulsion efficiency release a smaller fraction of the combustion heat during cruise  into  the  exhaust  plume, and  hence  cause plume conditions which during mixing reach higher relative  humidity  for  the  same  ambient  temperature  and hence form contrails also at higher ambient temperatures.
Hence aircraft will form contrails more frequently when
using more fuel efficient engines.

TO test the theory, a flight test was conducted between two aircraft with low and high bypass engines:

For a direct test of the theory, a formation flight of two different large  jet aircraft was arranged, wing by wing, during an ascent and a descent f the aircraft. Contrail formation and ambient conditions were observed simultaneously from a research aircraft.
The two contrail forming aircraft were
(i) a Boeing B707 equipped with four jet engines of type JT3D-3B with bypass-ratio of 1.4 and
(ii)  an  Airbus  A340-300 with  four  jet  engines  of  type
CFM56-5C4  with  bypass-ratio  of  6.8.

The results indicated that contrails were formed in more instances in case of the A340 (with higher bypass engines) compared to the B707.

Photo of an A340 with contrail and B707 without one. Image from Influence of propulsion efficiency on contrail formation by Ulrich Schumann

Ambient  conditions were measured and the contrail formation was observed from a research aircraft flying less than 1 km behind the two contrail forming aircraft. As documented in several photos, an altitude range exists in which the A340 causes  contrails while  the  B707  causes  none.

Though the sample size is pretty small, it does appear that the high bypass engines used in modern commercial aircraft are more prone to contrail formation compared to the older turbojets.


Which aluminium alloy is used in the Boeing 747's fuselage?

The primary alloy for the original 747 is 2024-T3, which is not the strongest or otherwise perfect, but a well-established convenient choice. Second is 7075-T6, used for major load-bearing parts.

7075 is stronger, but less workable and less tough than most; it comes closer to the edge for aluminum, so to speak.
6061 follows for for less-loaded or some more complex parts, where it's a staple, being overall the easiest to use out of common Al alloys. This is not nearly an exhaustive list, just the main alloys.


Can PC joystick simulate aerodynamic lock in spin?

Yes there are PC joysticks that can remain in an off center position: the active feedback joysticks, without the force feedback switched on. The stick feels pretty light in that situation and kind of remains where you put it, almost like a helicopter cyclic stick with the trim button released.

When switched on, the force feedback can act like a passive spring and accepts some input parameters for varying the feel. The neutral position can be varied, the return position of the spring. All pretty course, not bad for the money, although the stepper motor produces grainy feedback forces.


Why do hydraulic jack stalls result in pitch up and right roll?

A moderately quick search reveals a few pprune threads and an accident report. From these I understood that:

The hydraulic jack stall occurs when the aerodynamic force on the rotor blades exceeds the force the hydraulic actuator can apply.

The actuators are controlling pitch of rotor blades and are applying force to keep the angle of attack high. When the angle of attack gets too high the blades stall which is associated with change in centre of lift creating a moment trying to rotate the blade to lower angle of attack, strong enough to overpower the actuator.

The right pitch moment is because the retreating blades have higher angle of attack and approach stall earlier.

The forward pitch moment is when the stall happens in higher G manoeuvre where the helicopter is pitching up and thus the blades in front are running at higher angle of attack and approach stall earlier. If the stall happens due to overspeed, the pitch moment will be back instead. In either case it will be opposite to the selected cyclic.

The down collective moment is because the angle of attack decreases on the forward (or backward) and right blades, but does not increase on the other ones, so the total lift is reduced.

The behaviour can be considered a good thing as it prevents aerodynamic stall from fully developing. The effect is also similar to what would happen if the actuators were more powerful and aerodynamic stall did fully develop. It can however be more surprising for the pilot since it may happen before vibrations that normally indicate incipient aerodynamic stall. The condition is self-correcting in that the reduction in pitch causes reduction in G loading and thus reduction of the aerodynamic forces, but the drop in performance can obviously be a problem if it happens too low.


How can I acquire an N number that's showing as deregistered?

If the number is deregistered, you cannot re-register it unless you have the previous registered owner of that number submit a request to relinquish the number to you.

So you must get in touch with the old owner of that N number, and if he is willing to write a letter relinquishing it, all you should have to do is send his letter in with your request and a check.

If you have any other doubt, this page has information about your issue:
About Aircraft Registration Renewal

If you need any other information, do not hesitate to comment and I will try to give you a more detailed answer for your problem


Tip tanks are only used when the wing volume is not sufficient to carry the needed fuel. They can mostly be found on the early jets which had thin wings for a higher Mach number of drag rise onset and very thirsty engines. They offer two advantages over conventional external tanks:

Their wing tip location allows the highest wing bending relief for a given fuel mass.
They widen the wing by their diameter, so reducing induced drag a bit.

Later designs used the area rule to shape the tip tanks, so they could help to reduce wave drag a bit, especially on designs which predated the knowledge of efficient transsonic shaping.

On fighter aircraft, tip tanks should be jettisoned with the start of air combat because their high roll inertia contribution puts the aircraft at a clear disadvantage.

The XF-104, the prototype of the Lockheed Starfighter. Where else would it allow to store all the fuel?


Can I do a CAT III ILS approach if minimums are above CAT I?

Yes, you can request it. We (ATC) may or may not grant it. It can be quite complicated for us to establish CAT II/III procedures, including having to switch over to backup power, turning on stopbars and other protective measures, limiting aircraft and vehicle movements on the maneuvering area, closing certain taxiways etc.

Doing a CAT III approach is not just looking at a different chart, it can involve a lot of complicated procedures for the airport!


How much does it cost to lease a jetliner?

Slide 19 of this IBA presentation (PDF) shows how the aircraft's age is a factor:

Other factors such as global outlook, supply and demand, fuel prices, etc., all have an effect.

Anyway, that presentation confirms the accuracy of the data on an airliners.net thread from 10 months ago, from which:

For a 737-800 you are looking at USD 120,000–350,000 monthly.
For a 747-8i you are looking at USD 640,000–1,250,000 monthly.


Why is flutter a function of true, not indicated, airspeed?

Flutter happens when structural and aerodynamic eigenfrequencies converge. Aerodynamic eigenfrequencies depend on the time the air molecules take to transverse an aerodynamic surface.


What was the airline attendants looking at in LED display before light off in A320

The panel you have seen near the forward left door was most probably the Flight Attendant Panel of the CIDS (Cabin Intercommunication Data System). It looks like this: picture of the CIDS panel at jetphotos.com

In the lower part, it has two LED scales which can show the quantities in the fresh and waste water tanks of the aircraft. If I remember correctly, they will only light up while the IND ON pushbutton next to them is pressed.

The cabin crew will routinely check those water levels to ensure e.g. the lavatories can be used.


What is the difference between Review and Analysis in DO-178C?

No they are not the same.

Reviews are qualitative. They typically compare the artifact being reviewed to a standard using a checklist.

Analyses are quantitative. They could be functional analysis, data flow analysis, timing analysis, or other evaluation of the software artifact.

From DO-178C:

  6.3 Software Reviews and Analyses

  Reviews and analyses are applied to the outputs of the software
  development processes. One distinction between reviews and analyses is
  that analyses provide repeatable evidence of correctness and reviews
  provide a qualitative assessment of correctness. A review may consist
  of an inspection of an output of a process guided by a checklist or
  similar aid. An analysis may examine in detail the functionality,
  performance,  traceability, and safety implications of a software
  component, and its relationship to other components within the system
  or equipment.


Why is powering on the APU so low on the A320 emergency checklist?

The assumption was that a multiple engine failure happens at altitude, for instance in cruise while flying through volcanic ashes. This happened to British Airways Flight 9 and to KLM flight 876, with all four engines switching off due to the ash cloud. Total engine failure at altitude buys time, and if time is available first priority is to attempt to re-light an engine. APU will probably be off during cruise, and given the choice to re-light an engine or to light the APU it is clearly the engine that is the most beneficial to start.

All-engine-failure in airliners is very very unlikely. It is a function of number of engines - in a four-engined aeroplane, the chance of all four engines failing is assumed to be super extremely incredibly unlikely. With a statistical failure rate of 10$^{-5}$ per flying hour per engine, a four-engined aeroplane would experience all engine failure due to statistical causes once in $\frac{10^{20}}{24}$ flying hours1: a billion times a billion times four. So very uncommon that the only practical consideration would be a common mode failure from external causes, such as the volcanic ash cloud.

For a twin-engine like the A320, chance of all engine failure due to random causes is 2 * 10$^{-10}$, still considered an Extremely Unlikely event. Procedures are written for the least unlikely events, and updated according to events that actually happened. Now that a dual engine failure during take-off has actually happened, updating the procedures will be the result of failure analyses: how likely would it be to happen again, or what other procedures can be put in place to avoid this situation.

 1: The chance that any of four engines fails is 4 * 10$^{-5}$ per flying hour. Then 3 * 10$^{-5}$ per flying hour for the remaining engines etc.


What training is required for pilots conducting ASETPA operations?

According to the CASA AOC Handbook, section 15.3.1.2, pilots do need to have specific training. Most of this training is regarding engine failures and emergency landings, in some situations in IMC.

CASA requires that all ASETPA operators have a training and checking
organisation.
The CASA Inspector will verify that for ASETPA
operator’s the following additional procedures are included within the
training and checking organisation:

Engine failure or malfunction which necessitates stopping the aircraft on the ground
Engine failure or malfunction which necessitates an off-airport landing after take- off on the most suitable terrain in the vicinity of the aerodrome. These can be organised into a number of procedures, depending on the height of the aircraft at the time of the failure
Engine failure or malfunction which necessitates turning to execute a glide landing upon a serviceable runway, including a ‘turn-back’ manoeuvre. This procedure is to contain a minimum indicated airspeeds and altitudes
Engine malfunction, during climb, cruise and descent and from the approach to land phase in VMC and IMC
Additional procedures for the conduct of a forced landing in IMC to ground level

The next section discusses route limitations, which I am assuming the pilots should at least be familiar with.


Which supersonic airplanes use Pitot Air intakes?

A pitot intake will decelerate supersonic flow in one single, straight shock, while a ramp or cone intake will do this in several oblique shocks. It takes its name from the pitot tube, which in turn is named after the French physicist Henri Pitot who invented it to measure flow speed.

The objective of an air intake is to supply the engine with a uniform flow of air at approximately Mach 0.4 to 0.5. At higher flight speeds as much of the kinetic energy of the flow as possible must be turned into a pressure increase. Doing so efficiently reduces the work of the engine's compressor and increases mass flow, and consequently thrust. A pitot intake will have the lowest mass and complexity of all intake types and is the preferred choice as long as the pressure recovery can be performed efficiently.

A shock is the only way to decelerate supersonic flow. While the flow speed tangential to the shock will not be changed, the normal speed component is reduced downstream of the shock, approximately to the inverse of the upstream Mach number. The bigger the jump, the higher the friction losses in the shock become, the air is heated instead of compressed and pressure recovery suffers. Generally, those losses are acceptable up to a maximum flight speed of Mach 1.6. The lower mass of the pitot intake will make it more attractive, while for higher speeds the deceleration has to happen over several oblique shocks which are triggered by a spike or a ramp ahead of the intake lip.

Therefore, all supersonic jets which were designed to fly at less than Mach 1.6 use a pitot intake for mass and complexity reasons. This includes the smaller US jets (F-100, F-101, F-102, F2Y, F-8, F-16) and their counterparts in the Soviet Union (MiG-19, Yak-27, Yak-38M), Sweden (Saab 32, Saab 35, Saab 37), France (Super Étendard), Egypt (HA-300), Taiwan (Ching-Kuo) or Korea (T-50).

Pressure recovery measurements from the YF-16 (source: "Fundamentals of Fighter Design", RAeS Lecture by Ray Whitford, Cranfield University). The loss in efficiency above Mach 1.2 (left; 1 on the y scale denotes full conversion of kinetic energy into pressure) is readily apparent. This is mitigated by the pre-compression from the forebody at increasing angle of attack (right). The result is higher efficiency just when it is needed most, namely in turning supersonic flight. The same trick is used by the Rafale, and the wing root does this pre-compression in case of the F/A-18 and the Ching Kuo.

Top view of the right XB-70 intake at Mach 3 (source: "Fundamentals of Fighter Design", RAeS Lecture by Ray Whitford, Cranfield University). At Mach 3, a single shock intake would be grossly inefficient. Now a cascade of ever steeper oblique shocks is needed, culminating in a last straight shock. A multitude of moving ramps is required to adjust the geometry for the actual Mach number, and the square geometry, which is required for this flexibility, makes the intake tube much heavier (it is a pressure vessel, after all!) than the round tube of a pitot intake.


Why does a higher load factor increase stall speed?

What does 'having' a load factor1 mean? It means, by definition, that you are experiencing a force G times your weight. It doesn't matter how it happens: in a turn or loop or turbulence. But in all cases practically all that force (which usually counteracts the weight) comes from lift.

In normal unaccelerated flight, lift = weight. In a more general case, lift = weight $\times$ G. If G > 1, you need more lift than weight.2

How can you get more lift (from the same wing)? Either you go faster, or you increase angle of attack. So inevitably, for a given speed, you'll have to fly at a higher angle of attack, closer to stall. Or in other words, you'll reach stall at a higher speed than normal.

Note that exactly the same thing happens if you 'just' increase your weight, by other means than transient loading with G - say, by having more cargo or fuel. Again, you'll need more lift - with exactly the same consequences.

1 Load factor is applicable in all three axes, but we are implicitly talking about the normal factor in relation to stall speed. When you are accelerating forward or skidding, you'll also have a load factor, but it'll usually be well below 1.0.

2 On the other hand, if G = 0, you don't need wings at all and you'll go ballistic.


Do swept back wings affect the moment of inertia of an aircraft enough to be relevant for the roll response?

A wing has three basic design parameters—span, chord and sweep—which are all independent of each other.

Span is always measured along the perpendicular axis of the whole aircraft and chord is always measured along the longitudinal axis. So pivoting the wing around its root will change all three parameters and affect the properties that depend on them.

When designing the aircraft, you choose area (span times chord) to give you the needed amount of lift, then span to give you the desired minimum lift-to-drag speed and sweep for transsonic capability and/or stability. So you should be comparing swept and unswept wing of the same span and area, and those somewhat obviously have the same moment of inertia in roll.


Does FAR Part 121 require at least 45 minutes of fuel remaining upon landing?

No, the regulation only concerns dispatching and taking off. Fuel burn will usually vary a little bit based on unpredicted wind shifts, performance variations and traffic deviations.

  § 121.639 Fuel supply: All domestic operations.

  No person may dispatch or take off an airplane unless it has enough fuel -

  (a) To fly to the airport to which it is dispatched;

  (b) Thereafter, to fly to and land at the most distant alternate
  airport (where required) for the airport to which dispatched; and

  (c) Thereafter, to fly for 45 minutes at normal cruising fuel
  consumption or, for certificate holders who are authorized to conduct
  day VFR operations in their operations specifications and who are
  operating nontransport category airplanes type certificated after
  December 31, 1964, to fly for 30 minutes at normal cruising fuel
  consumption for day VFR operations.


What callsign would a medical emergency flight use?

The variety of callsigns used for medical flights are covered in the AIM 4-2-4:

  b. Air Ambulance Flights.

  Because of the priority afforded air ambulance flights in the ATC system, extreme discretion is necessary when using the term “MEDEVAC.” It is only intended for those missions of an urgent medical nature and to be utilized only for that portion of the flight requiring expeditious handling. When requested by the pilot, necessary notification to expedite ground handling of patients, etc., is provided by ATC; however, when possible, this information should be passed in advance through non−ATC communications systems.

  Civilian air ambulance flights responding to
  medical emergencies (first call to an accident scene,
  carrying patients, organ donors, organs, or other
  urgently needed lifesaving medical material) will be
  expedited by ATC when necessary. When expeditious
  handling is necessary, include the word
  “MEDEVAC” in the flight plan per paragraphs 5−1−8
  and 5−1−9. In radio communications, use the call
  sign“MEDEVAC,” followed by the aircraft registration
  letters/numbers.
  EXAMPLE− MEDEVAC Two Six Four Six.
  Similar provisions have been made for the use
  of “AIR EVAC” and “HOSP” by air ambulance
  flights, except that these flights will receive priority
  handling only when specifically requested.
  Air carrier and air taxi flights responding to
  medical emergencies will also be expedited by ATC
  when necessary. The nature of these medical
  emergency flights usually concerns the transportation
  of urgently needed lifesaving medical materials
  or vital organs. IT IS IMPERATIVE THAT THE
  COMPANY/PILOT DETERMINE, BY THE
  NATURE/URGENCY OF THE SPECIFIC
  MEDICAL CARGO, IF PRIORITY ATC ASSISTANCE
  IS REQUIRED. Pilots must include the word
  “MEDEVAC” in the flight plan per paragraphs 5−1−8
  and 5−1−9, and use the call sign “MEDEVAC,”
  followed by the company name and flight number for
  all transmissions when expeditious handling is
  required. It is important for ATC to be aware of
  “MEDEVAC” status, and it is the pilot’s responsibility
  to ensure that this information is provided to ATC.
  EXAMPLE−
  MEDEVAC Delta Thirty−Seven.


Explain how the infrared flame detector work?

Infared flame detectors have an imaging sensor that "sees" infared light.

When a flame ignites the various  types of materials burn at different strengths, intensities, and -what we care about- wavelengths.  In the visible  spectrum  we can describe a flame as red or blue which can be simplified flames discrete wavelengths.

The IR sensor can detect the wavelengths  given off outside that visible light spectrum. This helps eliminate sources  like a technicians  flashlight from setting off a pure visible  optical sensor.

An example from Wikipedia shows a distribution  of this emission.

! Fire spectrum


Validity of Volga-Dnepr An-124 Grounding in US

It only makes sense USA enforces the action of Ukraine, if it wishes Ukraine does the same in the future (as noted by @JuanJimenez). Luckily, those countries (states) already agreed to the following terms as part of joining ICAO:

4.2.1 State [Country] of Design
4.2.1.1 The State of Design of an aircraft shall:
a) transmit to every Contracting State which has in accordance with 4.2.3 a) advised the State of Design that it has entered the aircraft on its register, and to any other Contracting State upon request, any generally applicable information which it has found necessary for the continuing airworthiness of the aircraft, including its engines and propellers when applicable, and for the safe operation of the aircraft, (hereinafter called mandatory continuing airworthiness information) and notification of the suspension or revocation of a Type Certificate;
Note 1.— The term "mandatory continuing airworthiness information" is intended to include mandatory requirements for modification, replacement of parts or inspection of aircraft and amendment of operating limitations and procedures. Among such information is that issued by Contracting States in the form of airworthiness directives.
Note 2.— The Continuing Airworthiness of Aircraft in Service (Cir 95) provides the necessary information to assist Contracting States in establishing contact with competent authorities of other Contracting States for the purpose of maintaining continuing airworthiness of aircraft in service.

(Source: Annex 8 to the Chicago Convention; bold emphasis mine.)
That's the legalese for when a country that has designed a plane, finds an issue (e.g., the alleged unauthorized maintenance making those affected not airworthy), shall notify the other contracting states (other ICAO member states).
If any state wishes to ignore that it has been notified that certain planes are not airworthy, will surely have consequences, but this is a better fit for Law.SE.


How does type ratings training work at the airlines?

The carrier trains you for their aircraft.  If you don't already have a type rating for your new aircraft, then you'll get one as part of the checkride at the completion of Captain training. (Maybe you flew that aircraft at another carrier, or you were an International Relief Office -- a type-rated F.O., or maybe you simply got the type rating as part of F.O. training on that aircraft earlier.)  If the carrier needs you to have the type rating on your new aircraft as an FO, you'll get that as part of your training for that aircraft. If you don't need it, you probably won't.

Once you are in the system, everything is driven by seniority -- what do you have the seniority to hold -- and the rules of the contract.

Each fleet at each carrier, and more often than not, each domicile at each carrier, will have different dynamics.  In some cases, pilots "camp out" in one aircraft at a particular base for a long time; in other cases, after a couple of years, they're typically bidding (exercising seniority) to go back to training for the next step up the ladder (MD80 to 737 to 757 to 777 FO, then MD80 Captain to 737 to 757 to 777).  Different contracts have different rules; some allow a pilot to camp out as long as he wants -- perhaps he's enjoying the quality of life being a senior FO on a nice aircraft at a base close to home, and he isn't interested in upgrading to a bigger aircraft (where he'd be less senior) or the left seat of a smaller aircraft (where he'd also be rather junior) at a base far away. Other contracts (historically) have had provisions that once you can hold either your same seat on a bigger aircraft (or the left seat on any aircraft for an FO), your clock starts & within so many months, you have to upgrade (assuming one is still available) -- for whatever reason that contract was written to avoid having lots of pilots camping out in lieu of upgrading.  All very dependent on the contract in place where you work.

Also, the state of the economy and of the airline can drive a lot of this... with Delta retiring many, many senior captains over the next few years, there are lots of opportunities for progression.  When everything tanked after 9/11, forward progress stopped and in many cases people moved backwards... MD80 captains went back to being FO's, widebody FO's went back to being narrowbody FO's, junior FO's were furloughed, etc.  During the stagnation of the 2008+ recession coupled with the change to Age 65 retirements, nobody upgraded due to retirements (okay, very few retirements), and almost nobody was growing their fleets, so pilots stayed put much longer than they might have otherwise -- there was nothing available to bid FOR.  You can only exercise your seniority for a slot that is open.

  I'm also wondering how you get selected for the aircraft you will fly once reaching a major

It's essentially whatever aircraft/base needs the bodies that month.  One class may get a lot of 737's and a few A320's, another class gets all 767's.  Often, the vacancies in the 767 would be filled by pilots moving up from the smaller aircraft, but that doesn't always occur, and it's not at all unheard of for newhire FO's to sometimes go to much larger (read, better-paying) aircraft.  Of course, they'll be junior on that aircraft for a long time; they'd get a "more senior" schedule -- fewer weekends & holidays at work -- sooner on the smaller, more junior aircraft.

Likewise the domicile -- if JFK has the openings, you go to JFK (I'm so sorry). If JFK is full & ATL has the openings, you go to ATL (which is probably better, unless you live close to New York).  Easier to change domicile than to change aircraft, since no retraining is typically required. (Maybe an "international" course if your old domicile flew only domestic and your new one flies international -- but that's no big deal.)

Welcome to the airline industry!


How can I calculate a pitch/power table?

I got the answer from cessna company, as below.

The pitch/power table you have provided is not a product of Textron Aviation and has been developed outside of our flight testing and engineering. We have no formula available for calculating required pitch attitudes, The table shown appears to be developed by a flight school based on actual flight test observations.
In general terms, pitch relates to angle of attack. Angle of attack required for certain climb and descent rates are dependent on variables such as gross weight, C.G. location and indicated airspeed. In relation to the quote “pitch + power = performance”, a more accurate approach for developing a quick reference chart assuming the aircraft gross weight and C.G. remains constant is to match indicated airspeed with power settings. Pitch + power can approximate an airspeed, but more accurately power + airspeed = pitch. Flying an aircraft “by the numbers” relies on power settings and airspeeds, which consequently will produce a certain pitch attitude. Conversely, to facilitate a desired climb or descent rate we set power and approximate a pitch attitude to arrive at the desired airspeed.
The interrelation between pitch and airspeed is for the most part interchangeable, but most accurate is thinking of pitch attitude being a consequential product of power and airspeed in the context of normal flight maneuvers.

Well, nothing new here. But I found that there are no exact formula to deal with power and pitch table. I'll try to collect actual data.
Thank you guys.


How are temperature differences handled in a jet engine?

1. The combustion chamber

Temperature here is usually controlled via design of the chamber shape, in particular of the location where combustion occurs vs the airflow.

Image source

In the image above you can see that the fuel line (2) terminates in a nozzle. The nozzle will turn the fuel into tiny droplets to increase the surface area and hasten the combustion process.

Indicated with (6) are instead the main air holes: the cool air coming from the compressor (on the left side) enters the chamber with high pressure from these holes. Note that the holes are distributed in an annular pattern: high pressure air will be entering from all sides of the chamber.

The result is that the flame will not directly touch the walls of the
chamber, we then got rid of conductive heat transmission.
Convective is a non-issue: cool air keeps coming and hot air goes
into the turbine.
Radiative heat transmission might be an issue, but the new air
incoming will cool the walls via conduction.

The engine can thus run without the combustion chamber melting. Note that the use of specific materials does greatly improve the conditions, as higher temperatures can be tolerated, and thus better efficiencies achieved.

2. The turbine cooling air

The air is usually bled from a stage of the compressor, usually a high pressure stage, in a similar manner as done for the air used for the passenger compartment.

3. Thermal stresses

a. Short term

Over the duration of a flight the blades will warm up when the engine is turned on and cool down at the end of the flight. Intermediate load variation do not have a significant impact.

Even the initial warming and the final cooling do not pose a significant problem. The only effect to be taken into account is that the rotating hot blades will become slightly longer: a special material is placed on the opposing stationary side so that the gap is minimal during operation and the losses due to the air going around the blades (instead of between them) are reduced.

b. Prolonged

The most problematic aspect here is the so called "creep": the blades, after prolonged use, will tend to change shape, because they tend to be more malleable at high temperatures, exactly when they are under high tensile load. This becomes a problem over the lifetime of an engine, not during a single flight.

To mitigate this problem the blades are nowadays manufactured as single crystals: each blade is a single solid block of metal and not made up af many tiny crystals as the metal tools we use everyday. This is because under tensile load each of the crystals can slide over its neighbors (and high temperatures facilitate this) changing the shape of the blade. To visualize it, think of a rubber band that does not go back to its original form.

Having a single crystal prevents this sliding, giving more strength to the blade.


Would a homemade lawn chair balloon be visible on ATC and collision avoidance radar?

It might be visible to ATC, but, at best, only as one of several inconspicuous unidentified red dots.

It wouldn't appear on aircraft collision avoidance displays (TCAS) and would not trigger any TCAS alerts.

Radar cross section

Balloons, and clusters of balloons are mostly air (or similarly insubstantial gas). There is a thin layer of plastic but many plastic materials (e.g. mylar) are transparent to radar, or only weakly reflective.

It is for this reason that aerostats and high altitude balloons carry radar-reflectors when they need to be detected by radar.

Whether the chair itself has a detectable radar cross section depends partly on what materials it is constructed from. I suspect most available lawn chairs are not constructed from solid sheets of metal fixed at right angles but, at best, from a relatively tiny amount of relatively small-gauge metal tubing.

I'd be surprised if any improvised lawn-chair balloon had the same radar cross-section as a glider - and those are allegedly hard to see on primary radar.

Some helium balloons are made from metallised mylar (because it keeps the helium in for longer). These may be much more reflective to radar. The Calgary aviator pictured was said to have used "oversized party balloons" - they don't look like the metallised balloons that are commonplace where I live.

A perfectly conducting metal sphere of 1.15m diameter has a radar cross section of 1 m²

Some other radar cross section values:

  Human: 1 m²
  small combat aircraft: 2–3 m²
  Cargo aircraft: up to 100 m²

This suggests that military radar might display a return to an operator. A civilian primary radar might be less likely to display a return to an operator.

Primary radar

So far as I can tell, most civilian ATC and powered aircraft (TCAS etc) don't really make much use of primary radar to detect other airborne vehicles. They rely on transponder returns (i.e. secondary radar)

Even a large metal object like a Boeing 777 can disappear from the view of ATC and other aircraft when it turns off its transponder.

The Guardian newspaper reported

  Last month, the Swedish government complained that a Russian military aircraft had been flying near its airspace with its transponders turned off to avoid being spotted by civilian radar, and nearly collided with a passenger jet.

I'd be surprised if an improvised lawn-chair balloon was detectable where a Tu-95 was not.

What ATC see

This is from what is said to be a radar recording of flight 77 (at 4:18) probably at Dulles after controllers were aware of the prior 9/11 attacks.

Flight 77 had turned off its transponder, it is one of the small red dots at the left. Here's a closer look at that

Flight 77 is the red dot about 20% in and up from bottom left. There are other red dots that come and go but this one tracks steadily from left to right. I'd guess an especially alert controller who is not very busy would notice this sort of dot.  Even if the radar display doesn't filter it out,  unannounced slow-moving lawn-chair balloons appearing from the suburbs might not always be noticed (though see James' comment to Peter's answer which suggests they often do notice and act on such targets).

Transponders

Radios and transponders designed for hot-air balloons are available (example) and I've read that

  Transponders are mandatory for flights in some types of airspace in many parts of Europe from March 2008 onwards. This includes balloons and other light / recreational aviation and aircraft.

So I suspect that authorities will expect aviators in lighter-than air vehicles will take appropriate measures to be in communication with ATC/other aircraft and perhaps to be visible to secondary radar in airspace where they may come into conflict with other aircraft.

Kevin Walsh

Heres a news report from The Milwaukee Sentinel - Jul 19, 1984

Snopes reports

  He had wrapped his tether lines in foil in the hope that they would show up on radar, and, sure enough, he was picked up on the screens of controllers at Boston's Logan airport

So you probably need to take specific measures to make yourself more likely to show up on primary radar.

Conclusion

When attaching balloons to your lawn chair, first scrutinize the intertubes for designs for large improvised radar reflectors you can dangle from your vehicle. Hope that nearby on-duty ATC controllers have their displays set to show primary radar returns and not just secondary radar returns.


What can I be allowed to do as a engineering/ maintenance intern at a european airline?

In europe the MRO are regulated by Part 145, this part precise that you have to be  Certifying staff (owner of part 66) to work on aircraft.
For all other people you can't even loose a bolt except if you are under supervision of qualified Certifying staff.

For engineering work (without work on aircraft) you only need to have a sufficient degree (under company appreciation except for special works like airworthiness where this in precised in concerned regulation (Part M for example)).


Why is there typically a large gap between the first flight and mass production of aircraft?

You don't want an aircraft that just 'works'- rather, you want an aircraft that satisfies your needs. The first flight is usually made by a prototype and does just that- it flies and pretty much nothing else.

Only once you start the flight tests do you understand the airframe limitations and whether the aircraft meets the requirements; usually, a number of modifications are needed. Also, the first flights are rarely, if ever in production configuration. In most of the cases, the required systems are fitted later. In general, most of the combat aircraft bring about substantial improvement over its predecessors- in fact it is a requirement, as the old ones can be used with small improvements at a much lesser cost.

Me 262 was really a revolutionary product and the use of jet engines caused a number of delays; in fact the prototypes were flight tested with piston engines in 1941. The first test flight happened with piston engine- just as well because both the jets flamed out soon after takeoff. By the time the second and third prototypes, the engines had been changed. However, these engines (Jumo 004) were larger, requiring larger nacelles, which in turn required a bigger vertical stabilizer (the landing gear was changed later). Pre-production of Me 262 had started in 1943 (and went nowhere due to engine troubles) when it was decided to change it into a bomber, further increasing the development period. By the time it took the field, it was in too few numbers to do anything.

Another example is the Mirage III. There were significant differences between the aircraft in first flight and the production one. The prototype never reached the required Mach 2 in level flight.The first one to do was the pre-produciotn Mirage IIIA with an engine with more than 30% extra thrust, lengthened fuselage for radar etc. Even this version was not combat capable- that was the Mirage IIIC.

The design is not frozen till the flight testing is over and the production plans can only be finalized after that- you never know what'll change (for example the hugely successful Su-27 underwent a change in wing design midway through testing). The delays due to setting up of production comes later and is normally quite less for countries/companies having experience. It is the design freeze that takes up more time during test flights.


Do new VHF radios need to be flight tested?

Avionics shops almost never test VHF radios in flight. They are almost always tested on the ground with test equipment. The only time I can think of an in-flight test being required is if the technician is trying to troubleshoot an intermittent problem that only happens in flight (such as a faulty connector in the vibration-rich environment of a military transport helicopter).


Why circle an airport after takeoff? (SLC particularly)

I would assume it was to avoid terrain, traffic and/or the restricted airspace close to the airport, but there is at least one departure procedure from KSLC that calls for a climb in the hold. The SALT LAKE TWO departure includes this:

  Continue climb in TCH VORTAC holding pattern (hold south, left turn,
  341° inbound)

And several other departure procedures call for climbing right or left turns; combined with a few ATC vectors that could easily give the impression of circling.

You might try looking for the actual radar track online if you search flightaware.com or a similar site for your flight. That would let you see what track you really flew.


May pilots receive compensation for performing preventive maintenance under US regulations?

First, it's a little too broad to say that a private pilot can perform preventive maintenance. The full wording in 14 CFR 43.3(g) is (emphasis mine):

Except for holders of a sport pilot certificate, the holder of a pilot
certificate issued under part 61 may perform preventive maintenance
on any aircraft owned or operated by that pilot which is not used under part 121, 129, or 135 of this chapter.

In other words, a pilot can't perform preventive maintenance on just any aircraft. The definition of "operate" in 1.1 could be stretched, I suppose, but the pilot has to have some degree of operational control over the aircraft. Another pilot without that control couldn't do preventive maintenance on your aircraft anyway, whether or not you were paying them.
Beyond that, the word "compensation" doesn't appear in part 43 so it seems not to be a factor in who can perform maintenance, preventive or otherwise. And common sense says that a pilot can be compensated because otherwise a part 91 ferry pilot wouldn't be allowed to top off hydraulic fluid or replace a landing light bulb (for example).


Do most flight schools and FBOs in the US prohibit student pilots from practicing stalls while flying solo?

The two flight schools I have used had this rule and all of the other local places I know of also have this rule. The FAA no longer recommends full break stalls during training anyway you merely need to bring it to the horn. Interestingly enough the data does not support the decision

  Student pilots are, by far, the least likely to suffer stall/spin
  accidents, as a proportion of in the pilot population. Pilots holding
  FAA Airline Transport Pilot (ATP) certificates are also less likely to
  stall/spin.

Although a case can likely be made that limits like this are what make student pilots least likely to stall/spin.


Why are aircraft coloured in yellow during construction, repair or overhaul?

For unassembled and new planes or planes not yet painted the green/yellow color you see is the anti-corrosive coating on the aluminum

  ...every unpainted airplane is nominally green from being coated
  (typically) with an anti-corrosive green zinc chromate or zinc
  phosphate primer over the aluminum skins. The different shades of
  green simply tell you that different vendors produced the different
  pieces—they don’t all use the exact same primer.

Originally it was some variation on Zinc Chromate but it was found to be fairly toxic other things have been used over time which lead to the more green color and even some potentially "chrome-free" options.


Can one country really ban another from using its airspace?

Yes they can.

There was an attempt to allow one to pass over a country freely with the Freedoms of the Air however this is not a blanket thing and not everyone partakes.

  ....As of the summer of 2007, 129 countries were parties to this
  treaty, including such large ones as the United States of America,
  India, and Australia. However, Brazil, Russia, Indonesia, and China
  never joined, and Canada left the treaty in 1988. These large and
  strategically located non-IASTA-member states prefer to maintain
  tighter control over foreign airlines' overflight of their airspace,
  and negotiate transit agreements with other countries on a
  case-by-case basis.:23 Since the end of the Cold War, first freedom
  rights are almost completely universal.:151 Most countries require
  prior notification before an overflight, and may charge substantial
  fees for the privilege (see the wiki article for references)


What is the most efficient symmetrical airfoil shape?

Truncation (chopping off the rear portion of the airfoil) does not reduce drag, although reducing up to 20% of the chord does not significantly increase it.  As Peter says, "trade off between more separation and more wetted surface area.  Hence "boat tail" bullets.

The 3:1 ratio of chord to width is apparently a bike racing specification.  Nothing new here,
the full airfoil produces the lowest drag.  Hence the cone they put on the back of the Space Shuttle while it was piggybacked on its 747.

What they did to meet the 3:1 specification was to truncate 66% of a 9 to 1 airfoil.
This produces the lowest drag within the specification.

The Kamm tail shape was designed for automobiles, providing a weight savings (as racers constantly accelerate and deccelerate) and to make the vehicle a little shorter, which can help changing lanes in a crowd.  Two different applications.  But a fully symmetrical airfoil, such as the struts of a Cessna 172 will do the job.

For an aircraft strut, if strength allows, make it as long and thin as possible until drag values begin to rise.  9 to 1 rings a bell from boat hull design, and would be a good place to start.


Do takeoffs and landings in a Pilatus PC-12 count for currency in a Piper Archer?

Category: Yes, both are "airplanes" as opposed to rotorcraft or gliders.

Class: Yes, both are single engine land planes, as opposed to multi-engined or sea planes.

Type: Yes, neither aircraft requires a type rating (both are under 12,500 lb max takeoff weight, neither is powered by a turbojet)

So the Piper Archer and Pilatus PC-12 qualify as currency for each other per this regulation.


What is the correct ATC phraseology in the US for an immediate - no delay takeoff?

The FAA AIM and ATC (7110.65) documents don't mention the ICAO equivalent. But I found it in the US AIP:

  34.1 (...) At times a clearance may include
  the word “IMMEDIATE.” For example:
  “CLEARED FOR IMMEDIATE TAKEOFF.” In
  such cases “IMMEDIATE” is used for purposes of air
  traffic separation. It is up to the pilot to refuse the
  clearance if, in the pilot’s opinion, compliance would
  adversely affect the operation.


Does the CF6 use Pneumatic Reverse Thrust from the APU's bleed air?

Thrust reversers on high-bypass engines are airframe parts

The thrust reversers on a high-bypass turbofan such as the CF6 are treated as part of the nacelle, which is made by the airframer, as opposed to being part of the engine.  This is unlike target-type thrust reversers, which are treated as engine parts by and large.

Airbus uses hydraulic reversers by and large

The reversers on current Airbii (including the A330 that you ask about) are hydraulic.  This is in contrast to the B747 and the A300/310 which also use the CF6 engine and use pneumatic reversers (driven from high stage engine bleed air directly, not the general bleed ducts).


How do landing fees work at larger airports?

Well, the short version is that there really isn't a standard (and this applies to small as well as large airports).

Some airport authorities charge fees that are billed through the FBO, some don't.
Some airport authorities bill you directly, some don't.
Normally you pay at the FBO before you leave.
Most of the FBO's set their own fees (although they may come from corporate).
Some FBO's don't charge any fees (although not very many these days).
Some FBO's waive some (or all) of their fees if you buy fuel, some don't.
Most FBO's charge a fee based on the size/class/weight of aircraft, some don't.

In short, call ahead to the FBO that you will be using and ask them what the fees are and whether or not any of them can be waived.  They are used to this question and will have the information handy for you.


What is the standard date format used in aviation?

I'm not sure if there is really an industry wide standard for the date format, but at least the ICAO (International Civil Aviation Organization) uses the YYMMDD date format for flight plans:

DOF/ The date of flight departure in a six figure format (YYMMDD, where YY equals the year, MM equals the month and DD equals the day).

(FAA on ICAO flight plans)
Other flight plans may use different formats however. See e.g. the following example of a LIDO flight plan (Lufthansa Systems format):

(image source: SimBrief.com)


FADEC or EEC for PT6-42A...is it feasible?

It is quite feasible and available on other PT-6 family engines. The PT-6C engine is available with FADEC but appears to be more for rotorcraft. That being said its fundamentally a similar engine and the systems could be migrated to the common PT-6A.

The question of:

  I am wondering is there any necessity to equip this engine with FADEC

This is somewhat of an opinion based question depending on what you personally feel is necessary. FADEC allows a pilot to run an engine at optimal performance all the time without needing to babysit the various engine parameters and settings. Some see this as a great benefit (taking something off your plate in a demanding airplane) while the more classically minded prefer to have finer control and operate their engines in various ways that may be considered less than optimal but appropriate for the mission.

The cost of FADEC is putting the engine control in the hands of a computer, which many are slowly becoming comfortable with. One thing to consider on smaller planes like the M600 is backup power systems. Large planes have the luxury of things like an APU and  a RAT as well as lots of alternators and battery banks to mitigate power failures across 4 discrete power sources. The M600 has only its alternator and batteries as a backup so in the event of a power loss you have less to fall back on and may lose the engine.

  whether the cost/benefit ratio is justifiable

Without knowing P&W's financials its hard to say. They are clearly selling lots of PT-6's and many might say theres no reason to change something that works. Since they clearly have a FADEC system for the PT-6C I would imagine a great deal of the work has been done and the system could be migrated to the PT-6A at least in part but you would need someone from PW to confirm that assumption.

Just a bit of a history note the PT-6A is a fairly old engine and has been around since the early 70's a time long before FADEC was small enough for something like the M600. On the same note the PA-46 first flew in '79 a bit before FADEC was viable on a small scale. There is some reality to keeping up a certified config once its certified.


How much the true altitude will be lower than indicated altitude by 10°C colder?

It's not a linear deviation so it depends on the altitude and the temperature at that altitude.  The deviation gets worse as you go higher and colder.

Lower and warmer, the error for 10 deg is very small, but higher and colder it can be a couple hundred feet.

Everybody uses a standard table that you can find all over the place with Google.  See here on Page 33 of the General Section of the Canada Air Pilot CAP GEN (IFR approach plates for Canada)  which explains how to apply the corrections, and can also be found in the AIM.  They are only used for IFR use for correcting altitudes for instrument procedures when close to the ground, and are generally not applied unless the temperature at the airport is below freezing.


For any given modern turbofan engine, does bypass ratio stay approximately constant during a typical flight?

There are two factors that determine the bypass ratio (or rather, how it may change):

The first is the relative diameter of the fan, compared to the core. Obviously, this is fixed in the design process, and doesn't change during flight
The second is the relative difference in RPM speed between the two (or even 3) shafts that exist in the engine. This does change during a flight, from the takeoff condition, to a lower thrust setting at cruise. So let's look at this in detail.

The compressor acts like a pump, increasing the pressure of the air, whether it's sucking at the intake like in takeoff, or RAM feed, such as in cruise flight. Also like a pump, the faster a spool (compressor) spins, the larger the mass flow it pumps (creates). So, if we consider a CFM56-7B engine for example, its shaft speeds at 100% are 5,175 rpm for N1 and 14,417 rpm for N2. That's a ratio of 2.78. At takeoff, the engine will be close to this condition. But at cruise thrust at 35,000ft, the engine will be throttled back. What tends to happen in a gas turbine, is the N1 spool slows down relatively more than N2, as the throttle is reduced. So at cruise, N1 is maybe 3,880 rpm (75%), while N2 is maybe 11,534 rpm (80%). The ratio between them is now 3.41. The pumping capacity of the core has only reduced 20% from the takeoff condition, while the pumping capacity of the fan has reduced 25%. Hence, the bypass ratio will be lower at cruise than at takeoff.

Now, my values of 80% and 75% at cruise are just suggestions. But it is to illustrate the point, that if the ratio between the rpm of the two spools change, the bypass ratio will change.

In essence, the core flow is being determined by the rpm of both spools, while the fan duct flow is just determined by the rpm of the fan. So changes in the rpm ratio will impact the bypass ratio.

{Why is the N2 operating range less than the N1 range?: The CFM56 engine has a single stage fan, and depending on the model, either a 3 or 4 stage booster (or LPC), with a 9 stage HPC. These compressors are making the air flow in the direction of increasing pressure. The air doesn't really want to do that. So, if the design tries to increase the pressure ratio per stage too much, the blade is likely to stall. Getting aerodynamic conditions which avoid stall for the first stage, and the last stage, for the same operating condition is difficult. It's even harder when there are 9 stages on the shaft, than 3 or 4 (plus a fan). So the range of conditions that a 9 stage compressor will operate over is generally less than the range of conditions that a 3 or 4 stage compressor will operate over.}


Can an airplane fly with greater weight than lift and how?

There are many situations where the weight is not equal to the lift.

Lift is, per definition, the aerodynamic force perpendicular to the undisturbed incoming airflow.

The weight of the aircraft is due to gravity, hence pointing down.

An example of a steady situation in which the lift is not equal to the weight is the climb phase. During climb the lift is actually less than the weight.

In your comment you mention a weight-to-lift ratio of 5 : 4. If that would be during an unaccelerated climb, the flight path angle would be 37 degrees and the thrust minus drag would have to be 60% of the weight.

The image below shows the weight vector $W$, lift vector $L$, and excess thrust vector $T$ in a ratio 5:4:3.

The combination of the lift and thrust vectors is equal is size and opposite to the weight vector. It is denoted $W'$ in the image.

For simplicity I left drag out of the image and assumed thrust is purely acting in the direction of travel.


How is the Density Altitude performance penalty split between propeller and engine?

There is no reciprocating gas engine or gas turbine which is not affected by density altitude, the density of the air directly affects how much mass of working fluid can be taken in by the engine for a given volume of air and as a consequence the amount of power it can develop for a given fuel consumption.  The less dense the air, the less power or thrust the engine can develop.

Turbocharging or supercharging a reciprocating engine can maintain uniform power outputs for a throttle input provided the density altitude does not exceed the critical altitude of the turbocharger.  Turboprop and turboshaft engine are generally 'flat-rated' ie the fuel controller maintains a uniform power output right up to the thermodynamic rating of the gas generator at altitude.

As for propellors, the thrust they can deliver is directly proportional to the density of the ambient air, so higher density altitudes mean less thrust for a given power input from the engine.

Performance tables for both engines and propellors are available from the manufacturer and vary between make and models.  In general, pilots really don't use this as much as the aircraft performance tables in the POH for a particular aircraft.


Need more volume with my aviation headset (David Clark OneX). I wear hearing aids

This is a decent article to take a look at but you may want to consider the clarity aloft headsets which use hearing aid speakers and seem to be able to serve as a nice drop in replacement.

  I have a hearing loss. Can I use this headset with my hearing aid?

  Because our headset uses high quality hearing aid speakers, the pilots
  who have hearing impairment just remove their existing hearing aids
  before putting on our headset. A balance control can be adjusted to
  favor one ear with louder sound. We have many pilots who have a range
  of hearing problems from mild to moderate.


Why are the 737 trim wheels located so close to the seats?

My guess is that the manual trim wheel handle (when not motor driven) to adjust it manually needs to be:

easily accessible from the seat.
generate a sufficient amount of torque by moment arm.

Which leaves this as one of the few spots where it could be conveniently placed. You can find the same thing in older aircraft cockpits including the L1011, B727 and B747-100/200. The 737 design remains very unchanged from when it first flew.


Do fuselage rip/crack/damage sensors exist?

Such sensors certainly exist. The sensor is as simple as can be: usually a piece of wire. The bonding of the wire to the skin or structural elements dictates what kinds of damage it's sensitive to.

The "wire" can be in the form of a thin metallization on a thin non-conductive substrate that's intimately glued to the skin - such gives the most sensitivity to cracks, and is a crack detector.

If you wish to detect whether the rocket is in the process of breaking up, you simply need to run a thin, insulated wire along a longitudinal structural member, such as a tank, and attach it in a few places, but certainly rigidly at the ends. The input is used sometimes for automatic flight termination.

The major problem with pressure differential sensors is that you really need a big hole to overwhelm the pressurization systems on turbine-powered transports. A pencil-sized or even coin-sized hole is noisy but essentially irrelevant, and no, you won't get sucked out through it.

Why is it so? For cabin ventilation to work to begin with, there must be an outflow valve. Such valves, in steady state, have openings way larger than a coin. The more unplanned-for holes you add to the pressurized section, the smaller the outflow valve's opening will be. Only when the outflow valve completely closes and the pressure is still insufficient, you've got a problem...

So yes, the outflow valve's position in steady state can be used as a measure of air leakage elsewhere.


Can stored/leased 737s be used to substitute for grounded MAXs?

It really isn't 1 new aircraft = 1 mothballed aircraft. Most of the 737 MAX aircraft were fleet expansions (for US carriers). The older aircraft get retired when they aren't economical to fly anymore, and even then a retired aircraft is often sold either to a scrap yard or to a lower budget operator. In order to bring an aircraft back into service they may have to go through C or D checks before they can be considered airworthy again (because old aircraft are often retired at a D-Check when it needs a major check).

Airlines need to schedule C/D checks out months in advance, each aircraft costing millions to go through the check and a month or more of downtime. There is only limited space available to do these checks, so even if they wanted to bring 10 aircraft back into service, it may take 6 months and cost $20-40 million. It's cheaper to cancel the flights.


What's the shortest amount of time a commercial airplane will be on the ground in between flights?

I flew SA-226/227 Metroliners for two different commuters back in the 1980s. If we were behind schedule, station managers had the option of asking the pilots to do an engine-running turn. The passenger entry door and the cargo door were on the left side of the airplane, so that meant the right engine was left running.

Such turns, usually only requested if there were few passengers exiting and entering, and little baggage being unloaded and loaded, took as I remember less than 10 minutes. The Metroliner was very noisy even with only one engine running and you didn't want to do it if any kind of a line would form at the bottom of the entry stairs.

Captains had the option of refusing such turns, and some captains wouldn't do them.


So, given Terry's remarks, GdD pointing out that the density altitude for Ovda is around 4300', and the current B744 Airport Planning Document, we can use the unadjusted (there's also a temperature adjusted version, but you don't need that when you have a density altitude in hand) T/O distance chart for the appropriate engine type (I'm going to use the CF6 version for example's sake) to compute how heavy a 747 out of Ovda can be.  (The chart you need is on page 72 on the PDF, by the way.)

Looking across the chart at the 10,000' line gets you an intersection with the 4000' altitude curve about halfway between 750,000 and 800,000 lbs; let us call this 775,000 lbs for argument's sake.  Since we have a slightly shorter runway and a somewhat higher DA, 760,000 lbs is a reasonable MTOW for a 744 out of Ovda; if you wished to be extra conservative, you could cap your MTOW at 750,000 lbs.

As per PDF page 15 of that same document, the typical operating empty weight of a B744 is about 394,000 pounds.  Adding the 120,000 pounds of passengers Terry quoted onto this leaves you with 236,000 lbs of fuel minimum, which is more than enough to get to anywhere in Europe with fuel to spare.  If you want figures, you can use the payload/range charts on PDF page 55 to get a max range of 4200 miles, which as per the great-circle mapper is enough to get you to anywhere in Europe or Africa, as well as the Indian subcontinent and much of SE Asia and China.

As to the landing half of it, the landing distance charts on PDF pages 94 and 95 can be used, assuming a wet runway, a 4300' density altitude for Ovda, the passenger configuration MLW of 630,000lbs, and the ability to use Flaps 30 (Flaps 25 yields a longer landing distance) we get a runway length of around 8700'; this'd be somewhat tight (you'd want to use max autobrakes and your reversers, and make sure you came over the fence at Vref with a firm touchdown to avoid floating in ground effect), but passenger flights don't land at MLW very often, so it'd be a workable operation.


The crew eats the food, no doubt. Just joking. The unused food is off loaded from the airplane into catering trucks and is discarded. It seems a bit sad but the reality is, any food that is leftover from a flight is considered “contaminated” so is discarded. This includes meals that passengers didn’t finish as well as entire carts full of food that were never used.

  So what is being done to help eliminate unnecessary waste? With
  limited space on flights, some airlines have started to make small
  changes by only loading 95% of the required meals on each flight with
  the expectation that some passengers will opt not to eat. Other
  airlines have started charging around $10 a meal, recognizing that
  less food is consumed when meals are only available for purchase
  rather then complimentary. In the past, some airlines have even
  donated their unused food to shelters and charities to help make a
  difference. Unfortunately due to incidents where food poisoning
  occurred, the liability became much too high and is no longer
  practiced by airlines. (Source)


Why does the MH370 ATC transcript never mention QNH? When is QNH given to aircraft?

Airline pilots generally get the QNH from the airport ATIS or similar. If they don't get it from there, ground control will give it before taxi.

Above the transition level (11,000 feet (3,350 m) in Malaysia, 18,000 feet in the US), the altimeter is set to the standard pressure (29.92 inHg, 1013 hPa), also referred to as QNE. It doesn't take that long to climb through this point, so they would keep the departure QNH set until reaching the transition altitude. They won't need to set it again until they begin their descent near their destination.

So after setting it before taxi, the next time they would need it is on approach before they descend below the transition level. Again, they can get the ATIS from their arrival airport for QNH. If not, the approach controller will give them the QNH.


Why aren't the CVR and FDR required to store data for a longer period?

CVRs typically store two hours of voice recordings (source).

It simply wouldn't serve any purpose to store longer recordings.
It is extremely rare for an emergency to last for such an extended time.
Qantas 32 was one of the longest emergencies in recent memory, and it was only 1:45.

The MH370 flight was longer, of course, but it still hasn't been recovered.

While I'm sure it is technologically possible to record more voice data, that would primarily record innocuous and routine conversations among the pilots.

I suspect that the pilots, and their unions, are reluctant to have their mundane and irrelevant conversations recorded and inspected.


Can aircraft stall at low speed during final landing?

When you learn to fly one of the first things that you learn is that recovering from a stall at low altitude is rarely successful. So we go up to at least 1,500 Above Ground Level (I like to go even higher) and we practice putting the airplane into a position just before it stalls—the stall warning light goes on and the wing begins to buffet. Then we use appropriate power, ailerons, and rudder to recover from the stall. Every pilot is tested on this before they receive their pilot’s license. Commercial pilots and air transport pilots are tested again with higher standards than private pilots. The idea is that you know the conditions that result in stalls and avoid getting into that situation. If for some reason you do stall the airplane, your training should kick in and you should be able to recover.

Unfortunately, many general aviation pilots get distracted on final approach and there are frequent stall-spin accidents in light airplanes. They are extremely rare in the airlines. The only one that comes to mind is the Colgan Air accident in 2009 where the plane iced up and the pilot flying ignored the stall warnings and pulled up on the stick instead of pushing the nose down and adding power.

We are taught that a stall can occur at any airspeed and any pitch if the airplane exceeds the critical angle of attack. There are lots of ways you can do that but the two most common are banking and icing up the wing. The Colgan Air crash is an example of the later. When the wings are iced up they do not provide as much lift as when they are clean. In order to keep the plane level you need to increase the pitch. This increases the angle of attack and at some point the wing exceeds the critical angle of attack and the plane stalls.

I am not aware of any recent airline accidents related to stalls while banking but there are plenty in light aircraft. An unfortunate series of events resulted in a stall spin accident in a Cirrus at Houston’s Hobby airport in 2016.

In the example you gave in your post of a 1.5 g load factor the stall speed increase is only going to be a few percent. So if you were in a Boeing 737 with a stall speed in the landing configuration of ~125 knots, the stall speed in the turn would be a few percent more—say 130 knots. The pilots know this information and will keep the angle of bank and airspeed within limits.

One of the maneuvers that we must master to get our Commercial license is steep turns of 50°. My Cherokee has a stall speed of 55 MPH in the approach configuration. The stall speed at a 50° bank angle is approximately 1.28 times 55 = 70 MPH. For me to successfully do a steep turn, I need to enter the maneuver at an airspeed of greater than 70 MPH.

Another maneuver that we must master is an accelerated stall. In this case we start out at our approach airspeed (in my Cherokee it is 80 MPH) and we bank to 45° and then pull up on the yoke. As you can guess from the discussion above, the airplane almost immediately stalls and then we recover from the stall. The reason we practice this maneuver is so that we don’t do this when coming in for a landing.

What causes pilots trouble is forgetting that your stall speed increases dramatically in a steep turn. Suppose you are turning to line up with the runway and you underestimate the wind and it blows you past the runway centerline. The natural reaction would be to steepen the turn. But when you steepen the turn you change the vertical component of lift so you start to sink toward the ground. If you pull up to get away from the ground you lose airspeed as well. So now you’ve increased the angle of attack past the critical angle of attack. The airplane stalls and if you weren’t coordinated with the rudder (which is often the case) the airplane enters a spin. This close to the ground they are rarely recoverable.

Stalls occur because the airplane exceeds the critical angle of attack. In most normal flying the angle of attack is directly related to the pitch and bank angles and the airspeed. We are taught how to avoid stalls in our primary training and when we get our refresher training every two years. We still manage to mess it up. Airline pilots receive much more training than we do and it is reflected in the accident statistics.