texts: How do you check for soft or muddy ground on a backcountry landing?

texts:
I've been curious about backcountry landings, but one part of the practice still seems to based more on instinct and experience than on well-explained processes.  I've read about making sure the strip is long enough, looking for power lines, avoiding campers and wildlife, checking your GA area, and other stuff, but what about mud?

Everyone seems to say that you do a pass close to the ground or a touch and go, but after that they seem to just make an educated guess based on how the ground looks and feels.  Given that a misjudgement here could be disastrous and prevent you from being able to accelerate to a take off, what's the actual process and list of things to consider to make sure you're landing in a good airstrip and not a foot of deceptive-looking mud?  Does a touch-and-go give you enough information or do you need to carefully consider things like recent rainfall, watershed shape, etc.?

Image from this video.


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

texts:
As seen in the picture below, Concorde used to have a droop nose which would be deployed during takeoff/landing and would be retracted to the normal position while in cruise (do reduce drag).

Concorde with a droop Nose deployed

Concorde in normal configuration

According to the wiki page on Concorde, this Droop Nose was added in the later versions of Concorde when the authorities raised questions about the restricted view which was available to pilots during landing/take off at very high angles of attack (which was required for the Concorde).

What are the other possible solutions which could have been employed instead of the droop nose to tackle to the restricted view from the cockpit?
Why did Concorde had to land and take off at higher than normal angle of attacks?
How did the Droop nose actually work? (Which mechanism was used to deploy and retract it)


texts: Why not add more blades to a helicopter?

texts:
There's something that bothers me inherently, and just like the Hueys from Vietnam, 'only' having two blades.  Doesn't seem enough, I mean, if despite your best planning, engineering -- whatever -- you lose one, you're like a twisty brick plummeting to the ground; and on the way down, it won't be any value shouting "That shouldn't have happened!!"

OK, first up, I accept the higher centre of gravity thing, if I have 4 blades, f'instance, but that's an engineering problem that can be fixed, ie. that's no reason.

There must be some other reason I can't have -- if in fact I actually can't -- have 4 or 6 or... isn't there an Aerospatiale chopper with 9??

Please tell me what I don't understand....


texts:
I've noticed that on some airlines (I may have seen it on SAS) the cabin crew had a small touchscreen at the front of the plane which they were using to select recorded audio messages etc, in both their language, and English.
Searching the internet, I found out it's called a Flight Attendant Panel — here are some photos I found:

So I gather they can control the lighting, and movies; but what else can these panels do?

I also found a FAP trainer, which says:

This virtual training environment generates a realistic FAP representation including OBRM, CAM and PRAM

What are OBRM, CAM and PRAM? What is being displayed above?


texts: Why Apollo 11 was launched in summer? (Performance question)

texts:
The question could seems stupid, but i think that best moment to launch a rocket is when temperature is lowest in order to achieve the best performance in a reaction engine. I do not know if there is some explanation to this or is just because that performance degradation is irrelebant.
Thank you for your time.


texts: How Helicopters Change Attitude (Gyroscopic Precession or Thrust Vector Tilt)

texts:
I am trying to determine how helicopters pitch and roll (i.e. change attitude). I have heard two explanations.

1) Pitch/roll change is achieved by tilting the tip path plane and therefor tilting the thrust vector. By tilting the thrust vector, a moment is generated about the center of gravity which pitches/rolls the helicopter.

2) Pitch/roll is achieved by imparting a moment onto the rotor, which can be viewed as a giant gyroscope, causing the helicopter to precess with a 90 degree phase lag (see page 2-16 here).

In Helicopter Theory by Wayne Johnson (© 1980), section 5-5 pg 191, he writes:

  Thus, there are two ways to view the rotor flap dynamics. First, the rotor blade can be considered a system with natural frequency of 1/rev, so that aerodynamic moments due to cyclic pitch excite the system at resonance. The response has a phase lag of exactly 90° (i.e. one-quarter of a cycle, which at 1/rev means an azimuth angle of 90° also). Alternatively, the rotor can be considered a gyro, with the flap hinges at the center of rotation forming the gyro gimbal. A control moment on the disk due to cyclic pitch then precesses the rotor with a 90° phase lag characteristic of a gyro until the flap damping produces a moment to stop the precession.

So, are the two explanations (1 and 2) equivalent, or are they both characteristics present? Wayne Johnson seems to suggest the former but gave no proof. Thanks in advance!


texts: What does 'in-trim speed' mean with respect to Boeing 737 mis-trimming correction?

texts:
This question was prompted by discussions of the recent Boeing 737 MAX crashes, but it is not specifically about that variant.

In Boeing's 737 NG Flight Crew Training Manual, in Chapter 8 (Non-Normal Operations), under the heading 'Manual Stabilizer Trim' on page 8.16, it states:

  Excessive airloads on the stabilizer may require effort by both pilots to correct the mis-trim. In extreme cases it may be necessary to aerodynamically relieve the airloads to allow manual trimming. Accelerate or decelerate towards the in-trim speed while attempting to trim manually.

In this context, does 'in-trim speed' mean the speed it is mis-trimmed to, the speed it would be trimmed to when put back in trim, or something else? For example, if the airplane is mis-trimmed nose down, and therefore, presumably, for a higher speed than intended, what action would relieve the airloads on the stabilizer, and why?

Additional information about what 'extreme cases' might require the airloads to be relieved in this manner would also be appreciated.


texts: Is it possible for the Boeing 737NG to do a powerback?

texts: I'm curious, in a non-normal situation, where it's not possible to use a pushback tug, would it be POSSIBLE to perform a powerback on the 737NG, assuming the area was reasonably clear of FOD?


texts: How can I calculate stall speed using foilsim?

texts: I need to find the stall speed of an airfoil using foilsim not the formula (https://www.grc.nasa.gov/WWW/K-12/airplane/foil3.html)


texts: What does it take from the airlines to be ETOPS certified?

texts: I have been told that the airlines to be certified for ETOPS apart from the aircraft certification, engineering wise it should have some conditions met in order to get the certification and to maintain it too.


texts: Could low pressure compressor blades be made of aluminum?

texts:
With the compressor blades on a gas turbine, could the low pressure blades be made of aluminum, or would it be catastrophic?

Edit:
Like the 6061 alloy.


texts: What is the takeoff decision speed (V1) for a Gulfstream G500?

texts: Can someone tell me what is the decision speed (V1) of the Gulfstream G500? Is it 200kt as shown in this picture?


texts: Case Study: Did I need to declare an emergency?

texts:
I am a fairly newly minted private pilot licensee (PPL). I had just taken off from a small private, (but open to the public) airfield. We are under the shelf of Class B, but are G up to 700 and then E to the B above at 4000.

My instructor noticed our oil Pressure gauge was very close to the red line, and so of course we  headed back. I was about to make a call to inform CTAF we would be crossing midfield and joining the left down wind. Instructor takes control and makes a call asking if any others are in the pattern. Then declare that we will be entering a right down wind (we are a left hand field).

A voice pipes up: Are you declaring an emergency?. I reply no, this is an urgency. (By now the wisdom of my instructor's decision to not cross midfield was clear: It would take much less time to land; it kept us out over paddocks should the situation get worse; It would not take us over houses as the left down wind would.)

Said voice pipes up again: This is the airfield manager, you must declare an emergency if you are using a right hand pattern. My Instructor told me to ignore him and make another call to CTAF asking for any traffic to report position. There was no traffic. We landed without incident.

Who was correct? The manager or us- and does anyone have a FAR/REF to support the conclusion. The old adage Aviate, Navigate, Communicate seems to apply here - but what might the manager be basing his claim on and why?


texts: What are the effects of separation at hypersonic rarefied flows?

texts:
Shock wave causes an adverse pressure gradient which causes an airfoil to stall. Also because gas density is much lower boundary layer becomes laminar and unable to prevent separation.

Correct me if information above is incorrect. Also are there any sources of stall? Like how much AoA affect separation? Can an airfoil stall (just because of hypersonic rarefied conditions) at 0° AoA?


texts: Are there any special considerations involved in designing manual flight controls for supersonic/hypersonic aircraft?

texts: What things, if any, might need to be taken into account in the design of manual flight controls for supersonic or hypersonic aircraft that wouldn’t need to be taken into account with manual controls for subsonic aircraft?


texts: Why do the old A320s have a lower tailwind limitation compared to the newer enhanced ones?

texts: In my company on the older A320s particularly the ones which are in the MSN 2000 range their tailwind limitation for takeoff and landing is 10 knots. But our newer enhanced ones have a 15 knots limitation. Any reason for this? Does Airbus do any modifications to the aircraft so that it's tailwind limit increases?


texts: Do noise abatement procedures have an impact on aircraft emissions?

texts: The ICAO has imposed Noise Abatement Departure Procedures (NADP1 and NADP2) in order to limit the noise impact of departing aircraft on communities living nearby airports. Could noise reduction lead to an increase in NOx/CO2 emissions (an aircraft needs more power to achieve faster climbing rates)? If so, why don't the ICAO (or local authorities) impose "Emission Reduction Procedures"?


texts: What was the aerial chase scene plane in 'Murder in the Clouds'?

texts:
I spotted this aircraft (tail number NC-406N) in an aerial chase scene in the movie Murder in the Clouds (1934) on Turner Classic Movies.

It appears to be a Travel Air D-4000. Is this correct?


texts: Why does elevator input move the turn coordinator ball in steep turns?

texts:
When practicing steep turns, I'm running into an unusual phenomenon.  If the airplane is losing altitude in coordinated flight and I apply aft stick pressure to pitch up and correct, I notice that the ball swings to the outside of the turn indicating a skidding condition.  Conversely if the airplane is gaining altitude and I release back pressure to the stick to descent, the ball always swings to the inside of the turn, indicating a slip.  This seems counter intuitive as one would think that an increase in AoA to gain altitude would result in increased adverse yaw, requiring more rudder pressure in the direction of the turn and less rudder pressure when the nose is lowered resulting in a lower AoA and adverse yaw.

I suspect the reason here has to do with the direction the nose is being forced in by the elevator input during the turn.  At a steep bank angle the nose is inadvertently being pulled inside the turning flightpath which results in a skidding condition, which should, therefore, be countered by less rudder pressure in the direction of the turn.  Conversely when elevator pressure is reduced, the nose would tend to stray outside of the tangential flightpath, resulting in a slipping condition.  The end byproduct of this would be reduced or even cross control inputs needed to maintain coordinated flight.  Can anyone else confirm this?


texts: Why did America not build its own ekranoplan?

texts:
The Lun-class ekranoplan (NATO name: "Duck") is a ground effect vehicle designed by Rostislav Evgenievich Alexeyev and used by the Soviet and Russian navies from 1987 until sometime in the late of 1990s. This project was huge, scattered a lot of effort, over-cost and under-delivered.

Why did the USA not design its own ekranoplan?


texts: How to artificially increase the Reynolds number in a wind tunnel?

texts: I'm currently scaling down a model 64 times for a wind tunnel analysis, where I'm measuring drag force (for drag coefficient) and lift force (for lift coefficient). However, I read that scaling down 64 times means that wind velocity must be scaled up by 64 times to keep the Reynolds number constant. I read that using trip strips are a viable solution. How do I calculate the location, size, and number and strips of the slips required to increase the Reynolds number by 64 times so I can get accurate results?


texts: Is there a way to register for updates on certain NTSB investigations?

texts:
I would like to track the progress of an investigation of a particular accident, NTSB WPR18FA200.

Some areas of the FAA website (advisory circulars, for example) allow users to register to receive updates by email when these items change.  Is there a similar functionality available for users of the NTSB accident database?  If so, where do I find it?


texts: What happens if a passenger dies mid-flight?

texts:
Last month (December 2014), there were news that a passenger passed away during a flight. As mentioned in this answer, it appears that it is not a very uncommon scenario.

In an unfortunate incident like this, how is this matter handled?


texts: What is Squawk on radar tracking websites?

texts: I have been noticing squawk on virtual radar, anyone have any idea what this is?


texts: Is it possible to define a "good landing" in terms of pitch angle and vertical speed?

texts: Is there a specific combination of pitch angle and vertical speed at touchdown that would be usually be considered a "good landing" in a B737NG?


texts: What were the "flap pump" and "gear pump" on the F-4E Phantom II?

texts:
When I choose the F-4 in X-Plane 8 there are "buttons" labeled "flap pump" and "gear pump", whose tooltips say something like:

  Manually operating and closing flaps/pumps in a failure

So

How did pilots operate these hand pumps? Video is appreciated.
How much "pumping" was needed to open and close the landing gear?
How much "pumping" was needed to move flaps a single unit?
Did you need to be powerful in order to operate these hand pumps?
How did these pumps work?


texts: How does air traffic control communicate with an aircraft?

texts:
I have a question on voice/data communication between air traffic control and an aircraft.

I read somewhere that control communicates with an aircraft directly, through a direct radio link, while it's within the line-of-sight. After that control communicates through satellite.

My questions are:

Why doesn't control use satellite throughout the flight?
Are direct radio links used only for voice services? or are they used for data as well?


texts: What constitute "known icing conditions" and when can you fly VFR while they exist?

texts: For flight operations conducted under 14 CFR part 91(other than subpart F) in VMC, what conditions constitute "known icing conditions"? Under what circumstances (e.g., altitude difference or no visible moisture), if any, could a VFR flight operation (other than in an aircraft certified for flight into known icing) be legally conducted despite an Area Forecast, AIRMET Zulu, Pirep or other possible indicator of known icing conditions?


texts: What are the climb rates during the different phases of flight of an A320?

texts:
I have read about common climb rates for an A320. It is said that the initial climb rate for an A320 is between 15-20° and it differs depending on the weight and also the altitude.

I therefore have the following questions:

Do climb rates for a given flight mission stay constant in one phase of flight (e.g. until reaching 1500ft altitude) and then change at a specific flight level or are they continuously adjusted?
Do given climb rates exist for (one arbitrary) given flight mission?
Is there a method to calculate the change of climb rates depending on altitude and weight?
Are there sources like papers, reports, manuals that will work for genuine citation?


texts: Is it better to reduce drag or increase lift?

texts:
Essentially my question is, in general is it better to have a lower drag or a larger lift. I know lift to drag ratios are used as an indicator but I think these don't give the best picture. For example, I'm running a 2D airfoil analysis and for 2 cases the CL/CD changes varies between 80 and 160 (obviously doesn't account for 3D drag). So you'd expect the best option as CL/CD as 160.
However the CL/CD only looks at the % change. So if the % increase in drag is say 70% and for lift it's 10% CL/CD will be larger for the increased drag but the amount of increase in lift force greatly outweights that of the drag (an increase of 175N of lift vs reduction of 14N of drag).
I guess it would depend on the application as well.
Any help would be greatly appreciated, thanks in advance!


texts: Can 'neutral static stability' only be achieved by constantly augmenting the control surfaces?

texts:
I watched a flight mechanics lecture that mentioned that some combat aircraft like the Hornet has a 'mode' where the on-board computer simultaneously and automatically adjusts all the control surfaces to make the plane fly with Statically neutral stability which to my understanding means that the lift moment is constantly aligned with the plane's center of gravity.

The result is that the pilot is able to pull back on the controls and pitch up and release the input and have the plane continue to fly in a new direction without any tendency to diverge or return to equilibrium (the trim position).

Is this true and is this stability only possible with a constant re-balance of the control surfaces of the plane?


texts: What are these two tail elements of the Avro RJ100?

texts:
What are these two tail-side elements of British Aerospace Avro RJ100 and what is their function:

Photo source: Eric Verplanken, jetphotos.net.


texts: Are compressor maps for multistage compressors drawn for one blade row or the whole compressor?

texts:
Apologies if this is a stupid question.
I am a little confused about compressor maps.
Are compressor maps such as this one, drawn for one blade row only or the whole compressor?

(source: Wikimedia)

If it is for one blade row, can you predict the behavior of the next blade row from the compressor map of the previous row? Like, I am guessing that the blade rows of say the HP compressor have the same speed lines because they are on the same spool, so would they move up or down the speed line?

If those maps are drawn for the whole compressor, then does that mean that all blade rows have the same operating conditions (in my opinion, they should have different operating conditions)?

Any insight would be really appreciated! Thank you!


texts: Is this "bearing" sentence utterly incorrect?

texts:
There is often tremendous confusion between bearing, track and similar terms.
On Wikipedia, I saw the following sentence:
NOTE CAREFULLY, THE FOLLOWING SENTENCE IS WRONG...

In aerial navigation, bearing refers to the actual compass direction
of the forward course of the aircraft.

...NOTE CAREFULLY, THAT SENTENCE IS WRONG.
PLEASE NOTE I believe that quote is totally incorrect, do not quote this page!
I refer to the "where the aircraft is going/pointing" as either "track" (the vector of motion over the ground) or "heading" (where the nose is pointing). Whereas, "bearing" means bearing regarding some distant object, (that could be either relative or absolute), and does not relate in any way to "where the aircraft is going/pointing".
{Indeed, you could just be standing somewhere - not moving and not in a vehicle - and very much talk about "bearings" to various landmarks.}
In other words, I have always thought this diagram is correct, and the only usage.
My question for actual pilots, controllers, etc, is this! ...
In fact, am I correct that the quoted sentence above is totally wrong?
Further: am I being "too dogmatic"? Hence specifically: is it the case that, in aviation, perhaps you sometimes do use "bearing" loosely to mean track or heading?
Let me repeat myself: I'm pretty sure I understand what bearing means and what track means.  But the wiki quote in question, says the opposite: in fact, is it just plain utterly 100% incorrect, a typo? Or, am I naive... ie, you dudes sometimes do use "bearing" to mean what I call track?
{Just TBTC ... for me "bearing" cannot be used about "us". The sentence "our bearing.." is meaningless.  You use bearing about another object. "What's the bearing to blah..." [Of course, that could be implicit, ie, "is our bearing still 123?" meaning, I'm still talking about bearing to Sydney as in the previous sentence...].}
As a curiosity: physics programmers (for games, whatever) constantly use these terms, and of course, we have to use them really precisely like any programming. You can imagine a character or whatever (perhaps a car in GTA!) has all these qualities, they are discussed constantly in relation to physics of the virtual objects in all senses, AI paths of tanks, etc etc.  Next time I scream at someone "that's not bearing you idiot, that's track" I want to be on a sound footing!


texts: Why does this plane have vapor trails coming out of wings?

texts:
See this video of Birmingham strong crosswinds landings:

At 2.57, there is a 737-800 landing (screen shot below).
One can clearly see some vapor (?) coming out of what seems to be two holes on both wings, from 3.03 to 3.10, were the plane lands.

This does not seems to be a 'classical" vapor trail, as asked in this question, as it clearly does not occur at the tip of the wing.

What is this? What explains this? Something specific to the 737-800?

Edit: While it is clear to me that this is a vapor trail, the question is more about why there is a vapor trail at this precise location of
the wing.
Usually, these appear at the wing tip, and this is clearly not the case
here. Maybe something with the flaps, as suggested ?
Thus, while the question itself is not exactly a dupe, this answer (and the associated pictures) give a clear explanation.


texts: How do trainer aircraft differ from non-trainer versions?

texts:
In flying schools, there are aircraft designated for training student pilots. Do these aircraft have special equipments or controls on-board which are used by instructors?
Like maybe extra panels or something?


texts: I overboosted an engine in a Mooney 231 - do I need to do an inspection?

texts:
I have an intercooler, but no wastegate. Manifold pressure was not controlled on takeoff and went to 50. The max is 37!  If overboosting doesn't really exist because the relief valve opens, then how did the gauge even get to 50?  It was at that level for 20-30 secs. The engine appears to run great afterwards.

Is there anything that should be inspected or done?


texts: Why do some Mach trimmers move the elevator?

texts:
A pop-up rod on a the FO's control column on a DC-9 that shows the Mach trim position. (YouTube)
Regarding the title, I'm not sure if it's just some or all jetliners (I tried to research it). On the DC-9, MD-80, and 737NG,* it is stated clearly in the FCOMs that the Mach trim moves the elevator to counter the Mach tuck. On the 737 the system starts operating above Mach 0.615 (See FCOM 9.20). And below is part of the text from the MD-80 FCOM:

Operating on a Mach schedule, the Mach trim compensator pulls the First Officer’s control column aft as Mach number increases. As the control column moves aft, an indicator rod on the left side of the First Officer’s control column extends, giving visual indication of Mach trim operation.

Why don't the mentioned Mach trimmers use the stabilizer? I always thought the stabilizer had more fine control, not to mention the drag penalty of an offset elevator. There must be a reason for moving the control column aft and not just trim the stabilizer.
Update
It is not an era's technology limitation. The Boeing 707 moved the stabilizer for its Mach trim according to both an accident investigation report and a Cambridge University book. And like the DC-9, the 707 did not have hydraulics for its elevators.
* The MD-90** and B717 move their stabilizer according to their FCOMs.
** Unlike the rest of the DC-9 family, the MD-90 uses a powered-elevator.
My current working hypothesis is that the answer relates to stick forces, but I can't find any reliable sources on the design reasoning.

I checked these posts where Mach tuck was discussed:

Why does aircraft stability increase when it transitions from subsonic to supersonic flight?
What are the advantages of a Trimmable Horizontal Stabilizer?


texts: Which official document lists active airport identifiers?

texts:
Is there an official FAA document with which I can find an airport by its identifier code if I do not have a name or location? In the Chart Supplement I can find the airport if I know the city and state. However, I can’t seem to find any sort of reverse lookup document that lets me find it by code only.

I know I can search on SkyVector/ForeFlight/etc. but I am specifically asking if there is a government published “index document” for this.


texts: Is drag the only aerodynamic force that acts upon an asymmetric body (a glider in particular) travelling through the air?

texts:
It is known that for a symmetric body, like a sphere falling through the air, the only aerodynamic force that acts upon it is the drag that points always in the opposite direction relative to its speed.

Now, an asymmetric body traveling through the air, I guess, will have a drag that makes an angle different from 180 degree with its speed.

As a glider is just an asymmetric body, it means that the only aerodynamic force acting upon it is the drag that is conventionally decomposed in what we call Lift and Drag.

Is it true that Lift and Drag applied to gliders or airplanes are just a convention, two forces that in reality do not exist, and there is only a True Drag that makes an angle of a certain value with the speed of the aircraft?


texts: What are the crewing requirements for a B787 flying LAX to SIN?

texts: I’m wondering what the crew size, and rest requirements for the flight crew of a Boeing 787-9 flying LAX to SIN (Flight number UA37).


texts: What is the Boeing 727 AC Generator Panel Part Number?

texts:
Does anyone know the part number for the Boeing 727 AC Generator Drive panel?  I have searched the Internet and have not found the part number.

(Source)


texts: How can the landing gear of an A320 be lowered in the event of a simultaneous hydraulic and electrical failure?

texts: What is the process for lowering the landing gear of an A320 when the hydraulic and electrical systems are not operational?  What happens to the aircraft when you lower the landing gear with inoperative hydraulic and electrical systems?


texts: Can someone please explain the concept of circulation? I am able to understand the mathematical form i.e. it is the line integral of the velocity field. But I am not able to understand the physical meaning of circulation.


texts: Why does the 737 Original have an explicit hydraulic-quantity indicator for only the A hydraulic system?

texts:
The 737 (Original, Classic, NG, and MAX) has two primary hydraulic systems (A and B),1 which provide power to the aircraft’s flight controls and other aircraft components (like the wheelbrakes, landing-gear extension/retraction, and nosewheel steering).
On all 737s, the cockpit instrument panels have gauges which provide a readout of the pressure available in both of the primary hydraulic systems.2  Hydraulic quantity, however, is a different matter; on the 737 Original, the cockpit instrumentation features a quantity gauge only for the A hydraulic system, with the B system having to make do with a mere low-quantity warning light (the same type of indicator as with the standby hydraulic system, although on a different one of the instrument panels):

(Diagram originally by the National Transportation Safety Board, page 11 [page 29 of the PDF]; cropped and imageified by me.)
In contrast, the later 737 Classic has quantity gauges for each of the two primary hydraulic systems:

(Diagram originally by the National Transportation Safety Board, page 17 [page 41 of the PDF]; cropped and imageified by me.)
Why doesn’t the Original have quantity gauges for both main hydraulic systems, rather than just for the A system?

1: A third, standby system is unpressurised in normal flight, but can be activated by the flightcrew (or, in a few critical situations, automatically) in the event of a primary hydraulic failure; the 737 also has manual-reversion capability for the ailerons and elevators in the event of a complete hydraulic failure, one of only a few jetliners to still include this capability.
2: The standby hydraulic system, which is normally unpressurised anyways, merely has a warning light that comes on if the pressure within an active standby system falls too low.


texts: Have there been any studies on which fly-by-wire pilot interface is preferred; rate control or direct control?

texts:
Provided an aircraft with a fly-by-wire system, there are basically two possible choices when it comes deciding how to let the pilots interface with it:

rate control / attitude hold: a deflection of the stick will command a certain rate, releasing it will make the system maintain the current attitude. See the Airbus Normal control law.
direct control: a deflection of the yoke will directly translate to a deflection of the surfaces, mimicking the "old" mechanical control setup. It is my understanding that this is the design choice of Boeing in its new aircrafts.

I do not wish to discuss how Airbus and Boeing made their design decisions, but rather see if there has been performed a study on what interface is preferred by pilots, eventually differentiating among private/commercial pilots or Airbus/Boeing certified pilots or even pure civil/(former) military pilots.

Does any of you have any reference?


texts: What is this light passenger prop airplane which crash landed in East Kalimantan, Borneo in 1983?

texts: Plane crash landed in Borneo jungle in 1983.


texts: Does the Zenith have anything to do with the read-out of an IRU accelerometer?

texts:
Let's say that I have an accelerometer as part of an inertial reference system. Will the position of the Zenith with-respect-to the current position (in terms of rotation) of my accelerometer, have any impact on the accelerometer readings? Is there any kind of relationship at all?

Or, in other words, do we ever speak of accelerometers as part of an IRU... in terms of relationship with the Zenith?


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

texts:
For example, take N133AA.

https://www.jetphotos.com/registration/N133AA shows American Airlines photos from the 90s and an helicopter from this decade:

The FAA only shows the helicopter registry:

https://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=N133AA

Transtats shows that the last time N133AA flew from LA to NY was in 2008, and I'd bet that was not the helicopter.

Is it normal that tail numbers get reused? How can I make my cross-searches reliable?


texts: How should ground crews act to safely extinguish an airliner's brake unit fire?

texts:
When the brake unit was overheated and had just begun to catch fire due to excessive braking because of long taxi distance upon arrival, the ground personnel (not firefighters) made the first intervention with the fire extinguisher on the parking stand until the firefighters arrive.

I’m wondering, are there any points to be taken into account in terms of ground safety when approaching landing gear during this first intervention or in the case of extinguishing? Is there any guidance procedure for ground crew other than professional firefighters?

What type of extinguisher content should be used to extinguish the fire?

Regarding the related post: How do fire crews handle hot brakes?

I don’t think it’s the same topic. I would like to know if there is a guidance document explaining how the ground crew [not fire crew] should behave in the event of a brake fire upon aircraft arrival.


texts: Why is Airbus proceeding with both the A330neo and A350 XWB?

texts:
Looking at the specifications for the A330neo and A350 XWB, it strikes me that the two under-development models of the A330neo are relatively similar in specification to the A350-800, one slightly shorter and one slightly longer, with corresponding variances in passenger numbers. List pricing (for what little it's worth) is approximately the same, as well.

As a result, it seems like having two distinct models competing for essentially the same market segment should just increase costs for Airbus, and it's not clear to me what the gains are. Is it easier to sell the A330neo to airlines because of it's relative similarity with the existing A330? Is the A330neo cheaper to operate than the A350 (this seems dubious given cost of operation is one of the big selling points of the A350)?

There's been some rumours about the A350-800 getting cancelled and customers pushed towards A330neo or larger A350 models; this still counterintuitive to me. Surely having a smaller range of aircraft families (i.e., A320, A350, A380) simplifies a lot (manufacturing, certification, etc.), so why increase the number of families instead of a smaller A350 model?


texts: Can I transfer TSA approval between flight schools?

texts:
I have finally been approved by the TSA for my current school and it has not been one month.

If I decide to change the flight school, can my TSA can be transferred fast without any fee?


texts: Why do private jets such as Gulfstream fly higher than other civilian jets?

texts:
I heard in a TV show that private jets such as Gulfstream can fly at about 50,000 ft, higher than other civil jets.

Is it an aerodynamic reason (lighter aircraft to be sustained in a less dense air) or does it depend on the fact that a smaller fuselage is more resistant to lower outside pressure at a higher altitude?

I think that – if possible – flying higher, in order to fly faster and with lower fuel flow, is always better. Am I correct?


texts: Why aren't auto-pilot systems used on helicopters to make them trivially easy to fly?

texts:
As far as my understanding of helicopters goes, it is generally much harder to learn to pilot a helicopter when compared to a plane. This is because a helicopter is naturally unstable and would crash if left on it's own, while the airplane has aerodynamic stability when up in the air.

But why aren't there auto-pilot systems for helicopters to take all the difficult work away? There are already auto hover systems available for helicopters, so shouldn't it be possible to manufacture a helicopter that is trivially easy to handle?

Obviously a lot more goes into piloting than just controlling the aircraft, but it would be great to be able to skip a large chunk of it.


texts: Why does a turbofan shut off when rapidly retarding the thrust levers?

texts:
In a turbofan engine, when the thrust lever is at maximum and is then suddenly pulled back to idle, the engine will shut off and lose power.

How can this be the case as the engine should be at idle when the thrust lever is brought to idle? But in this case, the engine shuts off because of the sudden movement. What is the specific reason for this?


texts: How can pilots identify, in flight, the cracked layer(inner/middle/outer) from an impaired windshield?

texts:
Depending on the cracked layer, there would be some actions from the crew.
The inner layer seems to be simple to identify, but if the middle and/or outer layer is cracked, how will pilots identify the right crack's position?


texts: What can happen if a bird strikes the engine during landing?

texts:
I am not sure what can happen if a bird strikes an engine during landing.

To narrow it down: commercial airliner (B787/A380 etc.) hitting a large bird so engine out is likely.


texts: Is Electronic Flight Bag(EFB) any different from our day-to-day tablet?

texts: Other than the fact that EFB must be installed with appropiate charts and other manuals, is there any difference between EFB and normal tablet? Can I use the same tablet I play Plant VS Zombie as EFB if I load appropiate charts?


texts: Is there a regulation that defines when to use QFE or QNH for landing?

texts: Is there an EASA regulation that says to use QFE or QNH when landing?


texts: Are there any aircraft that were grounded and later approved for flight?

texts:
Last year the Boeing 737 Max 8 was grounded after two fatal crashes.

Historically, are there any other commercial aircraft which were grounded (due to safety issues), and later “fixed” by manufacturers and approved by FAA and/or other authorities for flight?


texts: What are the equation linking static air temperature with true airspeed & altitude?

texts: If I want to calculate static air temperature (OAT), but I'm only given an altitude and a true airspeed. Is there such an equation that relates these principles together. I've had a look at wikipedia and to calculate OAT, the total air temperature is required. Problem is, I don't have a Mach number to solve the equation. Is there another way to solve this problem


texts: How much fuel did the N Class Navy blimp carry?

texts: The Navy N Class blimp was powered by 2 Wright R-1300 Cyclone 7 radial engines and was able to cross the Atlantic and back again without refueling.  How many gallons of fuel did it carry for a maximum range cruise?  The information is needed for a ton mile/gallon efficiency calculation.


texts: To what extent is the clerical work (i.e. amending flight plans, logging, etc.) of a center air traffic controller now automated?

texts:
Specifically, do center controllers have to manually amend every flight plan now that En-Route Automation Modernization (ERAM) is fully implemented in the USA? To what extent is the process automated?

I know that, once the flight is en route, if the computer predicts a conflict the controller will need to okay a flight amendment. When flight plan requests are sent in and the center computer checks their viability, do controllers still have to give the okay to amend them and send them back?

Essentially, my question is this: what do FAA center air traffic controllers currently (I say currently because of when ERAM was implemented) do besides talking to the pilot?


texts: What do Fighter pilots' thumbs look like?

texts:
I have to imagine this question doesn't get asked too often, but I read actress Sienna Miller said her "nipples look like fighter pilots' thumbs" from breastfeeding.

I'm so confused. Do pilots' thumbs have a certain way of looking that is known?

I'm a blogger and want to write about her comment, but I'm looking for some context to explain it to our readers with.

Any ideas?

http://www.eonline.com/news/844242/sienna-miller-prefers-her-postpartum-nipples-they-look-like-fighter-pilots-thumbs


texts: What is the purpose of the ball and string attached to the tip of the vertical fin on test aircraft?

texts:
This question applies to aircraft being tested, presumably within a certification program.

I've seen what looks like either a ball or "shuttlecock" at the end of a tether attached to the top/rear extremity of an aircraft's vertical fin. An example can be seen toward the end of this video.

What is its purpose? Is is part of or does it contain any instrumentation, or is it there to provide direct visual indication of something - such as trailing airflow patterns?


texts: Which operating systems do entertainment systems run on?

texts: Which operating systems run the In-Flight Entertainment Systems on commercial passenger aircraft?


texts: Why does a subsonic nacelle inlet have a throat before the diverging section?

texts:
Aircraft propulsion 2nd edition by SAEED FAROKHI" p.340

Aircraft propulsion 2nd edition by SAEED FAROKHI" p.123

As we can see from the image, the nacelle slightly converges towards a throat, before diverging. Why?

Is it to produce the lip thrust force? If so, is that force independent of the diffuser thrust (i.e., the  internal pressure rise in the diverging section) ?

And if the cowl lip  represents an airfoil operating at a negative angle of attack, shouldnt the  "lip thrust" be in the opposite direction?


texts: Why does turbofan exhaust appear to reverse direction?

texts:
Yesterday I was at the airport planespotting. I observed the exhaust of a couple of turbofan engines, and found it curious how the fluid seemed to behave as it was leaving the engine and gaining distance to the aircraft.
From observation, this is what it appeared like:

The exhaust left the engine in a high speed, violent manner and quickly slowed down as it got farther from the engine.
The exhaust appeared to move in the other direction, aka going back towards the airplane before it met with new high-velocity exhaust gas and was violently mixed and pushed again further from the plane.

I remember the Saturn V's exhaust being pulled back into the flame duct right after engine start as the flame gained speed and the surrounding pressure dropped, and I was curious if something similar was happening with the turbofan?

Source of image: https://space.stackexchange.com/questions/26183/why-does-air-get-sucked-in-for-a-moment-before-engine-start


texts: When was the first rudder on an aircraft used?

texts: I have seen pictures of World War I-era airplanes that have rudders much smaller than today. When did the first rudder come out?


texts: What was the first monoplane airliner with a full cantilever wing (no struts)?

texts:
By Towpilot - Own work, CC BY-SA 3.0, Image source

By the mid 1930s, the gold standard of airliner construction was achieved: the DC-3 was a full aluminium aircraft with monocoque construction and a cantilever wing. But which aircraft was the first airliner with a full cantilever monoplane wing, no struts?


texts: Can the real time operating system used in aviation equipment be certified by itself?

texts:
Can the real time operating system used in aviation equipment be certified by itself, or must it be a part of some software certification effort?

I'm asking for getting a certificate of 178C. I don't understand if it is possible. There are a lot of resources that tell us about "certified operating system", but if is certified as a part of a project or it is certified just itself without any project... I have no practise in this field, but I was asked this question and it makes me puzzled.


texts: What aerodynamic characteristics arise from trailing edge sweep angle?

texts:
I drew 3 wing planforms, each with the same leading edge sweep. But they have different trailing edge sweep.

Let's just assume for the moment that all those wings have the same surface area, so that they all have the same total lift. What would be the different aerodynamic characteristics due to the trailing edge sweep angle?

Note: let's leave out considerations of control surfaces. Obviously the first wing would have the easiest implementation of control surfaces, but I want to focus on what the static wings do.

I looked into this and that related question. IMHO they're not quite the same thing as what I'm asking here.


texts: Can any conclusions about aerodynamic efficiency be drawn on the basis of fly-by noise?

texts:
Edit: I'm beginning to think this is more suited to the physics stack exchange, but I'll keep this here for a while...
Being bored mindless, surfing the interwebz, I came across this video, where a Sukhoi SU-57 is performing aerobatics:
Youtube: Су-57 с новым звуком пилотаж на форуме Армия 2020 Кубинка
At timestamp 1:45 the plane makes a pass, emitting a distinct screech with prominent components at about 1000, 2500 and 3600Hz.
This screech may very well be from external "add on" equipment such as radar reflectors (see this Q&A), as I kind of combine such noise to some kind of "fault" in the aerodynamics, and therefore I think during design phase sources of such disturbances in airflow would be eliminated from the airframe.
As first hand observations from real life, two examples: sailplanes and the B757, close encounter of which I have found to be memorable: the sailplanes for being very quiet, emitting a slight whisper with maybe a dash of a faint whistle at a high speed fly-by, and the B757s making a very distinct and sharp hizz on short finals (B757 is categorized as "heavy", not due to its size or mass, but for the nasty wake turbulence it makes).
So: can one draw conclusions about planes aerodynamic efficiency based on acoustic observations, and if so, to what extent?


texts: On average, how often (in flight hours) will a pilot face an emergency situation?

texts:
Experienced pilots (e.g. those with over 10,000 hours) are more likely to have faced an emergency situation some time in their career, compared to a new pilot (with say 40 hours). My question is, how often can one expect to encounter an emergency situation (e.g. one every 5,000 hours) ?

Here, an emergency situation is defined as a situation where the use of a "Mayday" call is justified, for example engine failure (in single / multi engine aircrafts), loss of electronic instruments in the cockpit etc. Medical emergencies are not counted.


texts: Wing Shape: Long/Wide Span Wings vs Deep Wings

texts:
Planes use wings to generate lift. The wider the span of the wing (looking at the plane from the front) the more lift it generates, however, this is at the expense of more drag.

Some planes like the F-22, or hang gliders, however, seem to adopt the strategy of having their wings larger front to back, instead of extending more out to the side. I'd guess that having a deeper wing would also increase lift at the expense drag and weight.

A third way to increase lift at the expense of drag is to increase the angle of attack of the wing, but I am not really interested in that for this question.

What are the advantages and disadvantages of a deeper wing versus a wider wing span?


texts: Is ADS-B intended to replace other traffic management systems?

texts:
What is the main purpose of ADS-B? How do aircrafts interact with each other using them?

Is it intended to replace the Traffic Collision Avoidance System (TCAS) or ground based Air Traffic Control (ATC)?

Also, why they need the Global Navigation Satellite System (GNSS)? Are there other systems that has a dependency relationship with ADS-B?


texts: Why does my wind tunnel experiment give two different stall angles of attack?

texts:
When I increase the angle of attack from 0 to 20 the stall begins at 18 deg.
When I decrease the angle of attack from 20 to 0 the stall ends at 13 deg.
Why the difference and what value (13 or 18 deg) should I use as the stall angle?


texts: How does having a bigger engine placed slightly more forward and higher impact the plane in pitch?

texts:
I'm asking about general aerodynamics for under-wing twin-jets – I'm not after information/speculation on the Max 8 crashes/systems, but I mention the crash below because of what I see as an unclear (to me at least) explanation:

In response to Lion Air Flight 610, leehamnews.com wrote:

  All objects on an aircraft placed ahead of the Center of Gravity will contribute to destabilize the aircraft in pitch.

But as one commentor wittingly pointed out, wouldn't the fwd engine also move the CG fwd.

And then:

  [G]enerating an angle of attack close to the stall angle of around 14°, the previously neutral engine nacelle generates lift. A lift which is felt by the aircraft as a pitch up moment (as its ahead of the CG line), now stronger than on the 737NG. This destabilizes the MAX in pitch at higher Angles Of Attack (AOA).

I read this as insufficient pitch authority, not pitch instability. Going by the text above, I would also imagine the destabilizing force to be a drag from the larger nacelle's bottom, not lift. For example, the relaxed pitch stability of the MD-11 warranted an LSAS system, but not a special anti-stall system.

I tried to look for an official explanation for why MCAS was added to understand the general aerodynamics, but the prelim report doesn't mention it.

I've presented what has me confused, but the question is the one in the title, wrt general aerodynamics, not 737 Max or MCAS.


texts: What does Hawaii ATC do in the case of ICBM warnings?

texts:
Recently somebody pushed the wrong button when testing the ICBM warning system in Hawaii and set off an ICBM warning statewide for 45 minutes.

In all probability ATC would ground departing flights and possibly local ones, but what about inbound flights? Were they ordered to turn back? Continued inbound? What is the procedure for dealing with such a warning?


texts: Can a C152 land VFR in Miami International Airport (KMIA)?

texts:
I know that it is a Class B airspace and VFR aircraft should request clearance at least 1 hour in advance before entering. The question is more related to MIA operations restrictions due to airliners.

It is possible to land with a C152 there, apart from being above VMC weather minimums (3 SM visibility and clear of clouds) and having 2-ways radio and transponder Mode C? How much is the landing fee? How can I gather all the information for GA and light ACFT operations in MIA?


texts: How big is the influence of color on the stability of the boundary layer?

texts:
I'm not sure if this is the best place, or physics.SE would a better place. I guess the aerospace engineers might be on both.

In class we were talking about stability of the boundary layer, and the influence of the temperature on the boundary layer.

The governing equation is given by Wiki boundary layer:

$$ u{\partial u \over \partial x}+\upsilon{\partial u \over \partial y}=-{1\over \rho} {\partial p \over \partial x}+{\nu}{\partial^2 u\over \partial y^2} $$

If we evaluate this $y=0$, where both $u$ and $v$ are zero:

$${1\over \rho} {\partial p \over \partial x}={\nu}{\partial^2 u\over \partial y^2} $$

We then deduced that, since $\nu=f(T)$, the instabilitiy of a boundary layer is thus a function of the temperature.

One of us mentioned that this was the reason that the Pepsi-livery Concorde had a lower maximum operating speed, since it is not white, but blue:
This would increase the temperature at the wing, making the boundary layer less stable.

I did so a search, which brought me to this Concorde SST website, which says that the wings were kept white, to reduce the temperature of the wing, but because of the fuel temperature. As the wings are white, the effects we were talking about are not relevant anymore, but still it made me wonder.

Could the color of a surface have so much influence on the stability of the boundary layer?


texts: What is the official term of a plane flying under another plane to avoid radar?

texts:
I was watching the news and, just now, learned that the Russians used a "trick" by flying a fighter plane under a cargo plane to Syria and successfully avoided radar detection for the fighter plane.

I wanted to learn more about this method (a Wiki article, for instance) but failed to find anything. So do the experts here know what this term is called, if there even is one?


texts:
The JF-17 Thunder is a fighter jet which has been developed with the joint collaboration of Pakistan and China. There has been a lot of hype about this aircraft in recent years. Pakistani and Chinese authorities are aggressively searching for customers for this aircraft. Recently they have got some orders from an Air Force of an undisclosed Asian country.

Is the JF-17 merely an upgraded Mig-21/F-7 (like Mig-21 Bison), or is it a whole new aircraft?


texts: What is the english term for "vol en ficelle"?

texts:
From what I have read online and understood, "vol en ficelle" is basically a low altitude flight preparation method that requires calculating a set of altitudes to be followed in order not to crash.

It consists of flying near the ground, but following small portions of levels (so without trying to flight closely the contours of the relief).
It is then necessary, during the mission preparation phase, on a predefined route, to cut it into sections and determine, for each of them, an altitude (not a height) that allows to keep a sufficient margin relative to the ground.
During the flight, it is important to know with sufficient precision where you are, then fly at the preset altitude.

The flight preparation is the main part of this technique, where you have plan properly the flight course and accorrdingly define corresponding landscape and montains heights.

Below is a map of such preparation. On the left side of the map is the "ficelle altitude", this flight preparation technique is apparently also called the "méthode numéri"

Image source : Le diable a bord

EDIT:
I doubt it is contour flying, even though that's the closest term to "flight en ficelle" so far.
Contour flying means flying at very low heights by maintaining a constant height above the ground, which means the altimeter is going to vary widely depending on the terrain profile. But with flying "en ficelle", the pilot follows a predetermined set of altitudes, thus we can fly without radars and the altimeter changes only in successive levels, i.e map in the OP. In "Flying in ficelle" the bulk of the job is the planning, ficelle refering to the thread used in the mapping technique to find out the "predetermined altitudes".

EDIT 2:
In the HUD of the Mirage F1, the "ficelle altitude" that the aircraft should go not lower than, is represented by the reticle below.

Rings a bell?
Are we overthinking this ? It is basically a low flying technique with predetermined set altitudes calculated in advance.


texts: How can I identify a low flying plane at night over Bangalore?

texts:
I often see a low flying plane circling over south Bangalore around 00:30-01:00. It circles at least twice and it's not very big, mostly the size of a private jet.

How can I go about identifying it?


texts: What are the advantages of the Cri-Cri's tail and fuselage design?

texts:
I have some questions regarding the Cri-Cri design. If some of them can't be answered directly, I would like to read what theory says about it.

Why is a T-tail used? What are its advantages for an LSA over a classic tail?
The plane has a polygon-shaped fuselage which is not streamlined. How much efficiency was traded for production simplicity?


texts: How does the adiabatic cooling of wingtip vortices work?

texts:
This question on condensation and wingtip vortices, What is the mechanism by which condensation forms above wings?, attributes the reduction in temperature found in wingtip vortices to Adiabatic cooling.

The reasoning for this, as quoted from Wikipedia, is given as:

  Adiabatic cooling occurs when the pressure on an adiabatically
  isolated system is decreased, allowing it to expand, thus causing it
  to do work on its surroundings. When the pressure applied on a
  parcel of air is reduced, the air in the parcel is allowed to expand;
  as the volume increases, the temperature falls as internal energy
  decreases

Emphasis mine

My question is: why are we assuming that a parcel of air—which, according to Bernoulli's principle has  a lower internal pressure—would be allowed to expand against the external pressure which would be higher?

This reasoning to me would suggest that the parcel would compress (if it was compressible) and that its temperature would increase.

Also, why are we assuming that air is now compressible below Mach?

Wouldn't it make more sense to attribute the reduction in temperature to an isochoric cooling process?  This would only require the internal pressure to decrease, and would not require a change in density.


texts: Can a DPE do a checkride in any plane of the same class?

texts:
Do DPEs have to be certified in a specific aircraft type, or can they do a checkride in any airplane of the same class?

For example, if I have done all my training in a Cirrus SR22 and want to do my IFR in the same Cirrus SR22 that I own, can I use any DPE who can do IFR for ASEL?


texts: Why do some airports have a non standard traffic pattern altitude?

texts: Some airports have a non-standard traffic pattern altitude.  For example KGXY is 800 feet.  Why is this?


texts: Why is Reverse thrust more effective at higher airspeeds?

texts:
It might seem logical at first but why is reverse thrust actually more effective at higher airspeeds?

If we assume that engine performance will not change during a 100 knot deceleration on landing roll-out, and engine is kept at constant reverse thrust throughout the whole landing then the engine will produce a constant force to slow the aircraft down. It won't be more effective at higher airspeeds because we are continuously redirecting a constant amount of air at specific velocity. Even if we include an engine performance change on landing roll-out, thrust will probably not change by more than a percent. Am I missing something?


texts: Why does one of the Boeing 777's spoilers deploy differently from the rest?

texts:
There is one spoiler that isn't totally deployed. Look:

Source: Airliners.net

And also on this other picture:

Source: Airliners.net

Why aren't they deployed at the same angle?


texts: What is the "off-side engine generator" on an A320?

texts: For the A320 family, is the "off-side engine generator" the same as the "emergency generator driven by the RAT"? I can't find the location of the "off-side engine generator" on the A320.


texts: What is the purpose of these movable panels on the MiG-35?

texts:
The MiG-35 has movable panels on the LERX (leading edge root extensions). There are a number of images around the web showing these panels deployed during slow flight and retracted otherwise.

When do they have to use these and what does the use of them change in the flight envelope?


texts: How many variations are there of the Avro Lancaster?

texts: How many different variations of the Avro Lancaster are there?


texts: Can a Greek EASA Part 66 License be converted to a German EASA Part 66 License?

texts: I want to convert my Greece Part 66 license to a German Part 66 license. What procedure do I have to follow?


texts: How strong is the A380 fuselage-wing joint?

texts: The Airbus A380 has a maximum take-off weight of almost 600 tons. How strong does the joint between the wings and the fuselage have to be so it doesn't break? And how could it be trusted unless real-time fractures don't occur? How was it tested? I mean, you cannot accomodate such a big joint in a wind tunnel except in computer simulations.


texts: Can a CFI provide endorsement training to non-US citizens without TSA approval?

texts:
Does a CFI need TSA approval to provide endorsement training to non-US citizens, such as the complex, high performance and tailwheel endorsements laid out in 14 CFR 61.31?
Recurrent training is exempt from TSA approval, however training for an endorsement isn't recurrent because it doesn't have to happen again. And it includes training in an aircraft, which usually requires TSA approval.
Some places such as AOPA suggest all of 61.31 is exempt:

He/she is seeking recurrent training, such as a flight review,
instrument proficiency check, or flight training listed under 14 CFR
61.31

But the TSA only suggests that 61.31(g) is covered:

High Altitude Training (HAT)  14 CFR Part 61.31(g) - Type rating
requirements, additional training, and authorization requirements.

If only 61.31(g) is exempt then only high altitude endorsement training is exempt, and TSA approval is required for complex, high performance and tailwheel. Is that accurate?
Government references are highly appreciated.


texts: What descent rate would be a "hard" landing in a Huey or similar helicopter with skids?

texts: I would like to know what vertical descent rate a Huey or other helicopter with skids can land safely at.  What would be considered a "hard" landing that would require air frame inspection?  What would the descent rate be for a running landing?  Thanks.


texts:
I'm currently in the process of designing a winglet for my low speed aircraft in xflr.

While researching about winglets I read in a Boeing article that if the baseline outboard wing is relatively lightly loaded, as on the 747-200, the potential benefit of tip devices can be greatly reduced. I don't understand the logic behind this statement.

Also what would be the optimal airfoil selection for the winglet? How would the chord, thickness, camber, etc. affect the weight and drag reduction due to the winglet?

And would the geometric twist affect the performance of the winglet?

Any other tips for winglet design would be greatly appreciated.


texts:
At what distance would you begin to see the sequenced flashing strobe on an approach light system at night? 10 NM? 20 NM? Visibility plays a role, but consider CAVU.

Also, strobe lights on radio and cell towers, what is their visibility distance at night?

And at those distances, are they initially faint as they fade into view?


texts: What scale is the speed trend line on a PFD's ASI?

texts: A primary flight display (PFD) in a glass cockpit has an airspeed indicator (ASI) that doesn't just display the speed, but also a vertical arrow or bar that shows the "speed trend" i.e. the acceleration. But there's no extra "acceleration scale" shown behind it like there is for speed. What's the scale of this trend arrow and how do you read it?


texts: What kind of warranty comes with a commercial aircraft?

texts:
Just wondering what the warranty is like. Can an airline simply decide to give every single aircraft back for the money they paid? Assuming they were unhappy with the results.

Will the manufacturers cover any repairs and regular service of the aircraft for x amount of time after the delivery?


texts: What can be considered under 61.113 (c) for passenger equipment?

texts:
Does 14 CFR 61.113(c) allow a passenger to pay for rental equipment for themselves (e.g. headset or parachute) in addition to their share of the operating expenses, or is that considered compensation?

e.g.

Occupants = 2
Hobbs cost = \$100
Headset rental for passenger = \$10

Can they pay either:

\$50 (Only allowed to split Hobbs costs)
\$55 (Allowed to include the headset in the total cost - i.e. included as 61.113 (c) rental fees)
\$60 (half the cost of the Hobbs + 100% of the headset)


texts: How long did the SR-71 take to get to cruising altitude?

texts: How long did it take for the SR-71 to go from taking off to 80,000 ft, including refueling?


texts:
The following table shows the operating temperature of Jet fuels (Source http://www.skybrary.aero/)

I know a lot of flights will be cancelled during bad weather conditions including the cold. How is the Engine fuel kept from freezing when the flight is operated at the mentioned fuel freezing temperature?


texts: Does an FAA pilot certificate qualify as an ICAO pilot licence?

texts:
What is an ICAO pilot license?

I've seen it as a job requirement before, does my FAA ATP count?


texts: What is the meaning of flap detent names (e.g., 10 degrees)?

texts: When I extend my flaps to 10 degrees, what exactly is the 10 degrees measuring?  Is this referring to the angle of the flap blades themselves, the new angle of the wing chord, the change in the new critical angle of attack or something else?


texts: Before COVID, what was the largest aviation crisis ever?

texts: The Covid-19 pandemic is the worst crisis aviation has ever faced. Which one was the biggest one before that pandemic?


texts: Which book should I study to learning flying in Australia?

texts:
I'm interested in buying a text book about learning to fly so that I'll have some basic knowledge when I begin lessons.

Someone recommended the Airplane Flying Handbook (FAA), but I was wondering if there's an equivalent Australian text and whether it's worth getting?


texts: What is the highest possible thrust generated by 15cm ducted fan?

texts:
I recently developed a sudden interest in flying. I'm wondering whether a pair of small ducted fans could lift a person off the ground.

Lets say the ducted fan is 15cm in diameter. What would be the most thrust a fan like that could produce?


texts: Is stall recovery training mandatory for Airbus pilots?

texts:
The recent reports about the Air Asia Flight 8501 crash mention that the plane was stalled and that the pilots could not recover from the stall. Indonesia's National Transport Safety Committee apparently had this to say:

  Subsequent flight crew action resulted in inability to control the aircraft ... causing the aircraft to depart from the normal flight envelope and enter a prolonged stall condition that was beyond the capability of the flight crew to recover.

Online information that I could find suggests that Airbus pilots were not required to learn stall-recovery and other upsets recovery as part of training, due to the aircrafts "inability" to enter those conditions. This may have changed, at least for stall recovery, at some airlines, after the crash of Air France Flight 447.

Is stall recovery mandatory training for Airbus pilots? Was it ever not mandatory? How about for pilots of Boeing, Embraer, and other large passenger aircraft?


texts: What drives and/or allows the move to higher-bypass turbofans on jetliners?

texts:
Note: I'm by no means an expert on any of this, I'm just curious.

There seems to be a general trend toward higher and higher bypass ratios in commercial jetliner engines. (I'm thinking here of 737/A320-size and larger aircraft.)

I understand why this is happening (fuel-efficiency & noise). But what has dictated the odd pace of the development?

There was obviously a drive toward higher bypass early on. E.g. P&W JT8D engines introduced in 1962 ran at 0.96:1, while - just a few years later in 1966 - the JT9D ran at 5:1. Quite a leap.

But then it seems to me that it settled around 5-6:1 for 25 years. Next big leap seems to be the GE90 in which runs at 9:1. That was 1992 and then it largely settled again at 9-10:1 for another couple of decades. The latest (smaller) leap appears to be the PW1000G at 12:1.

What has caused such sudden jumps and plateaus? Why hasn't there either been a more linear progression from the 1960s to now? Or a much faster progression toward the ratios we see today? They're obviously desirable.

I can just imagine P&W engineers looking at the JT9D in the mid-1960s, and thinking "well, we went from 1:1 to 5:1 in one go. Let's go for 10:1 next!". But that didn't happen. It seems their next major airliner engine was the PW2000 - fully 20 years later - at 6:1.

Was it due to technical/manufacturing limitations?
Has the emphasis on certain performance characteristics shifted? E.g. settling more permanently on economy over speed.
Is it simply that fleets stabilized around certain aircraft, and no new engines were needed/wanted for a long time?

The last point seems very plausible. Even so, the 747-8, 737-MAX and A320neo, while being comparable to their ancestors in size and role, have made sudden jumps from 5-6:1 to 10-12:1 engines. That feels like something that could conceivably have happened earlier or more gradually.

Of course I know that bypass ratio isn't the only interesting metric for an engine, but it's a noticeable one, even to the untrained eye; engines are simply becoming bigger and bigger. But that's also why I'm asking about the pace of development, since "making the fan bigger" seems like an obvious step to take (I know there's more to it but still). It also seems like something that'd be more likely to happen gradually, rather than in spurts.

Again, I'm no expert, I've just been googling. But I may have missed something basic.


texts: Who defines the callsign for radio communication?

texts: I started flying with VATSIM and but I couldn’t find a proper answer to this question online. Who defines a callsign for a plane in a given flight? Is a callsign set to a airplane? Is it related to the letters on the fuselage?


texts: When does an airliner switch from using the tiller to the rudder?

texts: When does an airliner switch from using the tiller to steer to the rudder on takeoff? Same for landing- when does the pilot switch from using the rudder to the tiller? What is this process? Once a pilot switches to the rudder on takeoff, is there a lock for the tiller? I'd imagine that it would be necessary to have some sort of system to lock the tiller so the pilot cannot accidentally hit it at high speed on the ground. If there is a locking mechanism, does it actually lock the tiller or does it simply disconnect the tiller from the nose wheel leaving the wheel free spinning so it can move as the rudder makes slight corrections while taking off/landing? Please expand as much as possible! Thanks.


texts: How do we derive Lift Coefficient of an airplane's wing?

texts:
In many references I read that lift coefficient ($C_l$) is a product of wind tunnel test. But many times I read the formula to calculate the coefficient of lift. From the lift equation, $$L=\frac{1}{2} \rho v^2 S C_l$$ $C_l$ is rearranged to derived the $C_l$ equation as below: $$C_l=\frac{2 L}{\rho v^2 S}$$

In my opinion, even it correct mathematically, but is not correct in the engineering process as it is not a product of a mathematic. The Coefficient of lift ($C_l$) is required to calculate the lift that will be produced by an airplane's wing with the given speed and the wings' area.

Am I correct with my opinion? Or, is any formula to calculate the coefficient of lift so the lift force can be calculated without any wind tunnel test?


texts: Are there generic routes all pilots can fly?

texts:
The recent question Is the destination of a commercial flight important for the pilot? stoked my curiosity but the answers were rather explaining that a pilot does not necessarily need to know where he is flying in advance (and general planning, broadly speaking).

I was more interested to know whether a pilot can fly anywhere. To take an analogy: I have a European driving license. With it, I can drive on all public roads in France and whether I got to Bordeaux or Calais does not matter. The road can be more or less complicated but all of them are accessible to me.

I can also drive to Germany. Sure, there re some minor differences in the regulations, but everything is basically the same.

I can also drive in the US. The differences are more pronounced but at least my European driving license allows me (in short) to drive there.

How is this with pilots?

Are there "generic" airports all pilots can land in? I know that a special license is required to land on some (the old airport in Hong Kong for instance) , but does this mean that "any airport is OK, except the ones which require special licenses?)
Same question for routes: are all domestic / international / overseas routes open to all pilots? Or one needs to have a special permit to fly one of these?

I know that each airplane type requires a license (or families of aircrafts) - similarly to my driving license type B for which a family car is OK but a truck is not. My question is on routes and destinations, once you fly something you are allowed to.


texts: How to get a home base airport in the UAE?

texts: How can you get a permanent home base airport in the United Arab Emirates, if your company is registered in different country?


texts: What are those arrow markings on the wing?

texts: I recently flew on a Boeing 737-800 and found these arrow markings on the wing. What are they for?


texts: Yellow chevron markings at end of runway, what do they mean?

texts:
In this YouTube video (link starts video at time of interest), the pilot appears to land in the area marked by the large yellow chevrons, in what appears to me (a layperson) to be a taxi way.

What are the meaning of the yellow markings? Under what conditions can a landing be made before this point?


texts: Would a helicopter with the blades on the bottom fly the same, if at all?

texts: I've heard that the pendulum rocket fallacy applies to rotorcraft as well. As stated above, I'm curious to know if a helicopter with blades on the bottom of the body would experience any effects from this. (Yes I know it's impractical and landing would be terribly difficult.)


texts: Can only victor way be used for route in cross country?

texts: In IFR low-en route chart, there are many ways related to victor ways. Do I have to select the route for cross county? Or, Can I choose the ways between victor ways?


texts: In the upper air, do pilots use flaps to generate lift as well slow down an aircraft?

texts:
I know, flaps are mostly used during take-off or landing to generate both lift and drag simultaneously.

I am wondering if the pilot uses flaps to generate more lift so that they can climb in less distance (due to drag of flap) and possible reasons for doing it. I have an idea that the flight control system may prohibit flap deployment above a certain altitude or at higher speeds due to flap structural limitations.


texts: 61.113 - is paying your pro rata share limited to the time you are in the plane?

texts:
Is the pro rata share that a passenger pays limited to the time he spends in the plane, or can it apply to the whole “operation”?
Let’s say my friend, who lives 100 miles away, asks me to fly him on a tour of his hometown. I take off from my home airport, fly 2 hours to his local airport, and land to pick him up. After flying him on a 1 hour tour, I drop him off and return, solo, to my home airport. Upon landing, 2 hours later, I refuel and, finding that I spent 100 dollars on gas for the entire day, prompt him to pay me 50 bucks. Given I made all legs of the flight for the sole purpose of entertaining his desire. Is my request for 50 dollars legal? Or, given that he was only in the plane for 1 hour out of 5, am I only entitled to 20?


texts: Why does the spiraling slipstream from a propeller hit the left side of the fin?

texts:
In the picture below, if the fuselage was shorter/longer, would the spiraling slipstream from a propeller hit the fin on the right side as opposed to the left?

Is it a deliberate positioning if yes, to hit the left (port) side?

I know the diagram is cartoonish but I couldn't find wind tunnel or CFD illustration.

It may seem hard to hit the right side, but imagine hitting the top of the elevator on the right side. Would this slipstream affect the pitch as well as the yaw?

(Source)

Is the following image related? I mean the path of the vortex, not the cause of the vortex.

(Source)


texts: Why is FL398 the REC MAX altitude on the A320?

texts: On the A320 PROG page and in our limitations the REC MAX/ MAX FL is listed as FL398. What is the reason behind this ?


texts: Why would there be two RNAV waypoints co-located with a VOR?

texts:
Similar to this question but more so!
The Enroute H-5 chart shows two RNAV waypoints over Spinner VORTAC (SPI): SOHOW and USIRE. Neither waypoint appears on the Low IFR charts, nor on the VFR charts.

Enroute H-5 as of Feb. 25, 2021, via Skyvector

Searching the online Form 8260-2 database I see that Spinner is used for many different instrument procedures:

ROCKY SID off of Indianapolis
LAKES SID off of Kansas City
NATCA SID off of St Louis (an RNAV procedure!)
Several Victor airways and J-routes
Several instrument approaches to SPI and other nearby airports (including use as an IAF or feeder fix for RNAV approaches!)
MOTIF STAR into Chicago/Gary
Bradford STAR into Chicago
Braymer STAR into Kansas City
RIVRS STAR into St Louis
Vandalia STAR into St Louis

Some of these procedures only use Spinner to define a waypoint on the route, but in other procedures Spinner is actually flown over.
SOHOW does not have a Form 8260-2 listed in the database, but from a general search I notice it is used in:

LUCIT STAR into Gary

USIRE is used in:

KOLTS STAR into Indianapolis

Comparing the location of the three waypoints:

Waypoint
Latitude
Longitude

Spinner
39 50 23.04N
089 40 39.85W

SOHOW
39 50 25.37N
089 40 37.43W

USIRE
39 50 23.04N
089 40 39.06W

SOHOW is ≈300 feet northeast of Spinner
USIRE is ≈062 feet due east of Spinner
USIRE is ≈270 feet southwest of SOHOW

So the question is: Why do SOHOW and USIRE exist? And in particular why do they both exist? I can think of three reasons:

There is a rule saying that RNAV procedures must only use RNAV waypoints.
Counterargument: Spinner is a waypoint on the NATCA (RNAV) SID.
Spinner will be decommissioned soon, and the RNAV waypoints will be used instead. Neither waypoint is exactly on top of Spinner, but perhaps it doesn't need to be; the LBNON waypoint will replace Lebanon VOR/DME soon and those do not have the same exact coordinates.
Counterargument: Spinner is used in several VOR approaches and to define fixes on other instrument procedures; also I haven't heard of any plans to decommission it.
The specific configuration of the LUCIT and KOLTS arrival procedures necessitate the distinction between two points 270 feet away from each other (less than 0.05 nautical miles).
Counterargument: Really?


texts: Is there any work on improving fuel tanks so they could store hydrogen?

texts:
I think that hydrogen is among the best fuels for use in supersonic and hypersonic flight, is there any work on improving fuel tanks so they could store hydrogen?

What would be the best state to store hydrogen for use as an aircraft fuel: solid, liquid or gas?

What are the complexities for storing it at each state?


texts: How to remove clogging in aircraft fuel nozzles?

texts: I have a dual orfice fuel nozzle (Used in CFM56 Engine/ Parker make). The secondary orifice is not opening up even at the required injection pressure. It had been not used for 3 years and I assume that it is clogged. Please suggest a method to clean this.


texts: Where to get information on FAA AIXM 5.0 versions of Special Activity Airpace (SAA) files?

texts:
Does anybody know where to find documentation or someone to ask questions about the SAA database provided by the National Flight Data Center? I have some questions about the ambiguity of some of the data.

Or better yet, is there a better source for the boundaries and meta data for special-use airspace?


texts: Do Federal Regulations really require compliance with all crewmember instructions?

texts:
On commercial flights, we're frequently told that all passengers are

  "required to comply with lighted signs and placards, and all crew member instructions".

But when it comes to the CFRs, the closest I can find is 14 CFR 121.571

  (a) Each certificate holder operating a passenger-carrying airplane shall insure that all passengers are orally briefed by the appropriate crewmember as follows:
    (1) Before each takeoff, on each of the following:
      (i)Smoking. Each passenger shall be briefed [...] This briefing shall include a statement that the Federal Aviation Regulations require passenger compliance with the lighted passenger information signs, posted placards, areas designated for safety purposes as no smoking areas, and crewmember instructions with regard to these items.
      (iii) The use of safety belts, [...] This briefing shall include a statement that the Federal Aviation Regulations require passenger compliance with lighted passenger information signs and crewmember instructions concerning the use of safety belts.

These rules seem to say passengers only have to follow instructions regarding Smoking, and Seatbelts.

Is there some specific, Federal Rule1, other than catch-all 91.3, that requires general compliance with all instructions?

What if I want to leave my tray table down?  Or keep my electronics on? Or put my feet in the aisle?

1Not a contract of carriage with the airline


texts: Was the Space Shuttle aerodynamically neutral while piggybacking, or did the combination act like a giant biplane?

texts:
Trying to investigate this question, I see that 'Ask the Captain' says:

  The weight of the shuttle is calculated like any payload. The 747
  produces enough lift to fly and to carry the weight of the shuttle. In
  this respect it is no different than cargo carried inside the
  airplane. source

But of course it is different, since cargo is generally carried inside an aircraft.

There was a fairing for the Shuttle's engines for drag reduction, but I'm wondering if the wings of the Shuttle had some aerodynamic contribution to the lifting body, or whether that was all down to the 747's wings.

 source


texts: In a flight plan, does it make any difference to write an increase of the flight level instead of writing a cruise climb?

texts:
According to ICAO 4444, a change of speed or level should be written in item 15 of the flight plan according to these rules:

  Change of speed or level (maximum 21 characters)
  The point at which a change of speed (5% TAS or 0.01 Mach or more) or
  a change of level is planned, expressed exactly as in (2) above,
  followed by an oblique stroke and both the cruising speed and the
  cruising level, expressed exactly as in (a) and (b) above, without a
  space between them, even when only one of these quantities will be
  changed.

  Examples:

  LN/N0284A045
  MAY/N0305Fl80
  HADDY/N0420F330
  4602N07805W/N0500F350
  46N078W/M082F330
  DUB180040/N0350M0840

  Cruise climb (maximum 28 characters)
  The letter C followed by an oblique stroke; THEN the point at
  which cruise climb is planned to start, expressed exactly as in
  (2) above, followed by an oblique stroke; THEN the speed to
  be maintained during cruise climb, expressed exactly as in (a)
  above, followed by the two levels defining the layer to be
  occupied during cruise climb, each level expressed exactly as
  in (b) above, or the level above which cruise climb is planned
  followed by the letters PLUS, without a space between them.

  Examples:

  C/48N050W/M082F290F350
  C/48N050W/M082F290PLUS
  C/52N050W/M220F580F620

Does it make any difference to write an increase in the flight level instead of writing a cruise climb? Are they different flight maneuvers?


texts:
What is the correct definition of "spanwise" and "chordwise" with a swept wing?  For example, in the context of "spanwise airflow" and "chordwise airflow"?
a) spanwise is from root to tip, generally following the quarter-chord line, and chordwise is the direction that gives the shortest distance from leading edge to trailing edge, very roughly perpendicular to the quarter-chord line.  I.e., roughly as illustrated in this related question (either diagram): Where is the spanwise flow? How does the span wise flow point the air towards the wingtip?
b) spanwise is perpendicular to the aircraft's longitudinal axis, and chordwise is parallel to the aircraft's longitudinal axis.
c) either of the above definitions could be considered to be correct, depending on the context
d) other
Not meant to be strictly multiple choice, those options are just offered as food for thought-- if one of the choices is almost right but needs some tweaking, please elaborate--
Among other things, the intent is to understand whether the diagrams linked in option a), exactly as drawn, really illustrate any net spanwise flow at all.


texts: What do compressor/turbine stages mean, and why we need a different number of stages?

texts:
I am new to aviation. I realize that LP (Low Pressure) and HP (High Pressure) compressors/turbines have a various number of stages.

What do stages mean?
What is the reason to have a different number of stages for LP and HP?


texts: What are these FAA facilities in Seattle doing?

texts:
While walking in Discovery Park I discovered this radar dome with FAA notices on its fence.

And not far away I cam across this small FAA signed radio antenna and shack.

Any idea what these facilities do?

My guess would be the radar is used by Seattle Center and that the small antenna is a marker beacon for southbound approaches to SeaTac.


texts: Why are true headings followed above 73N in the northern hemisphere, whereas in the southern hemisphere the change is made at 60S?

texts: The question is in regards to the asymmetry of the changeover latitudes and NOT about why it needs to be changed.


texts: Why do oblique-wing aircraft suffer from significant aerodynamic cross-coupling?

texts:
Oblique-winged aircraft (which have one long wing that pivots around a central point, so that the wing is straight at low speeds but strongly-swept - one side forwards, the other side back - at high speeds), while theoretically more efficient than conventional aircraft, have a number of issues which have prevented them from seeing any significant use; one of these problems are their various unusual cross-coupling modes, including a significant tendency towards pitch-roll coupling (where pitching up or down makes the aircraft roll to one side or the other, and vice versa) and a need to hold a significant bank angle just to maintain coordinated flight and keep from slipping sideways (even with no thrust asymmetry), all of which become increasingly severe at high sweep angles.

For example (emphasis added):

  McMurtry found the handling qualities were very close to the simulator, but that the aircraft’s asymmetry resulted in unusual trim requirements, asymmetric stall and inertial coupling. [...]  For instance, the AD-1 required about 10° of bank in order to trim the aircraft with no sideslip at 60° wing sweep.

  [...]

  As hoped, the low-cost, low-speed, low-technology AD-1 successfully demonstrated the concept of a manned oblique wing aircraft, sweeping the wing to a maximum of 60°.  The aircraft experienced cross coupling between pitching moment and aileron deflection.  This pitch-roll coupling and the aeroelastic effects contributed to unpleasant handling qualities at sweep angles above 45°.  [...]  [A Summary Of A Half-Century of Oblique Wing Research, pages 20-21.]

  The proposed wing pivot was also to be canted so that at 0° sweep, the wing was canted to 0°, but at 65° sweep it would be canted to 10°.  The wing incidence would also have been increased (a standard feature of the F-8) with higher sweep angles.  These features were expected to reduce aerodynamic cross-coupling, such as the necessity to bank the whole aircraft to trim sideslip, as found in the AD-1 flight testing.  [...]  _[A Summary Of A Half-Century of Oblique Wing Research, page 23.]_

  Flight tests of AV1 and AV2 proved the design to be controllable in both pitch and roll.  Noble states, “The elevon mixing is standard symmetric and the aircraft responds equally to left and right inputs.  There is some slight roll coupling associated with up and down elevator.  I believe this can be eliminated with fine tuning of the elevon mixing.”  _[A Summary Of A Half-Century of Oblique Wing Research, pages 32-33.]_

Why do oblique wings come with these strange cross-couplings?


texts: What is a heat dissipater and how does it work?

texts:
Wikipedia's Mi-24 Hind article (a Soviet helictoper) says:

  Heat dissipaters were also fitted to exhausts to decrease the Mi-24's heat signature.

There's no citation. What exactly is a heat dissipater and how does it work?


texts: Why couldn't the CRJ100/200 be equipped with triple-string autoland?

texts:
The gold standard for zero-visibility ILS approaches and landings is a triple-string autoland system, where the signals from the localiser and glideslope beams and the aircraft's radioaltimeter system1 are fed into the aircraft's autopilots and control its flightpath directly (with the pilots monitoring the system so that they can execute a go-around if the ILS signal is lost or an autopilot fails), cutting out the human middleman.  For redundancy, each of the aircraftside links in the chain (ILS receivers, autopilots, radioaltimeters, etc.) is present in triplicate, producing three parallel autoland strings, each constantly comparing its inputs and outputs to those of the other two strings, so that a failure in any of the components of the autoland system can be automatically detected and alerted to the pilots.
However, apparently, not all aircraft are capable of being equipped with a triple-string autoland, with the CRJ100/200 series being one of the major exceptions:

Simultaneously, pilot organizations globally were advocating the use of Head Up Display systems primarily from a safety viewpoint. Many operators in non-sophisticated environments without many ILS equipped runways were also looking for improvements. The net effect was pressure within the industry to find alternative ways to achieve low visibility operations, such as a "hybrid" system which used a relatively low reliability autoland system monitored by the pilots via a HUD. Alaska Airlines was a leader in this approach and undertook a lot of development work with Flight Dynamics and Boeing in this respect.
However, a major problem with this approach was that European authorities were very reluctant to certificate such schemes as they undermined the well proven concepts of "pure" autoland systems. This impasse was broken when British Airways became involved as a potential customer for Bombardier's Regional Jet, which could not accommodate a full Cat 3 autoland system, but would be required to operate in those conditions. By working with Alaska Airlines and Boeing, British Airways technical pilots were able to demonstrate that a hybrid concept was feasible, and although British Airways never eventually bought the regional jet, this was the breakthrough needed for international approval for such systems which meant that they could reach a global market.

Why couldn't the CRJ100/200 be equipped with a full triple-string ILS-III autoland system?  Even if it didn't normally come equipped with triplicate autopilots/ILS receivers/etc., those surely could have been retrofitted to the aircraft to give it full ILS-III autoland capability...

1: The localiser beam is used for lateral guidance throughout the entire approach until the aircraft taxis off the runway; vertical guidance is provided by the glideslope beam down to flare height, and the radioaltimeters thereafter.


texts: Does cargo heat failure require a diversion? What about if there are live animals in cargo?

texts:
There was a story in the news recently that an Air Canada 787-8, enroute from Tel Aviv (TLV) to Toronto (YYZ), diverted to Frankfurt (FRA) when the pilots discovered a problem with the cargo heat.  There was a live dog in the cargo hold, and the diversion potentially saved it from freezing to death.

The narrative has been that the pilots diverted specifically in order to save the dog.  But I am wondering whether a cargo heat malfunction might require a diversion, as a matter of standard operating procedure, regardless of whether live animals are on board.  After all, even if there are no live animals, there might be other valuable temperature-sensitive cargo.

In general, according to airline policies or procedures, under what circumstances would cargo heat failure warrant a diversion?

Any major airline would be of interest; if you want a specific one, let's say Air Canada.


texts: How is an aircraft aligned at a jet bridge?

texts: I see these jet bridges (or aerobridges) at nearly every new airport I go to. How are aircraft aligned with these bridges, particularly the A380 which has doors on both decks?


texts: Why would a turboprop be better than an internal combustion engine for a UAV?

texts: Let us consider a UAV, long endurance high altitude (~26,000ft). Why would a user (most probably military) go for a turboprop rather than an internal combustion engine?


texts: What qualifications or training allow a test pilot to fly a new aircraft?

texts: What makes a test pilot a test pilot? I'd imagine recovery from unusual attitudes is a must, but aerobatic pilots can do that as well. What training does a test pilot go through, that is unique and not taught to general pilots, makes that person a better candidate to test-fly a new aircraft with uncertainty in its aerodynamics?


texts: Are red obstacle lights near an airport required to be lit during the day?

texts:
What are the FAA Beacon Light Requirements for 80 foot tall High Mast Poles Near an Airport?  Specifically, do the RED beacon lights need to be illuminated 24 hours per day?  Or, do they only  need to be illuminated at night?

Here are examples of Holophane high mast pole installations around the country.

https://www.facebook.com/media/set/?set=a.236398096375560.78767.131284353553602&type=3

https://www.facebook.com/media/set/?set=a.194847107197326.56223.131284353553602&type=3


texts: Trying to identify large WWII aircraft by aileron position on rudder

texts: So I have this artifact, a man's slide-on tie clip with the figure of a large, overwing, possibly four engine aircraft, with possible pontoons. Any idea what this baby is? It looks like a Pan Am Clipper, but the position of the aileron, midway up the rudder, has my search skills stumped so far. Thanks.


texts: What is the section of the fuselage below the wings called?

texts:
Is there a specific name for the protruding section of fuselage beneath the wings? Im talking about the area where the landing gear bay often is. In the photo it's where the red Emirates logo is painted.

source

Some older airliners don't have them, such as the A300

source


texts: What is the difference between "anywhere" and "other than congested areas" in regard to minimum safe altitude?

texts:
Just missed a PPL written exam practice test question that asked me what the minimum safe altitude was over areas "other than congested areas". I chose "An altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface."

It turns out this is the answer to the question for the area of flight called "Anywhere". The answer for the area of flight called "other than congested", however, is "An altitude of 500 feet above the surface, except over open water or sparsely populated areas. In those cases, the aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure."

I can now handily regurgitate the correct answers on the written exam for either stated scenario/area. However I'm wanting to know, is the FAA trying to tell me something here? What is the difference between "other than congested" and "anywhere"? Is "other than congested" presumably more congested than "anywhere"? Anything to take away from this hair splitting other than grumbling about the FAA?

FAR 91.119 is as follows:

  Except when necessary for takeoff or landing, no person may operate an
  aircraft below the following altitudes: Anywhere. An altitude
  allowing, if a power unit fails, an emergency landing without undue
  hazard to persons or property on the surface. Over congested areas.
  Over any congested area of a city, town, or settlement, or over any
  open air assembly of persons, an altitude of 1,000 feet above the
  highest obstacle within a horizontal radius of 2,000 feet of the
  aircraft. Over other than congested areas. An altitude of 500 feet
  above the surface, except over open water or sparsely populated areas.
  In those cases, the aircraft may not be operated closer than 500 feet
  to any person, vessel, vehicle, or structure.


texts: Do modern aircraft still use load bearing ribs in wing construction?

texts: Modern aircraft are generally of monocoque construction. Does this apply only to the fuselage, or are modern wings made without load bearing ribs as well? Are they just for shaping of the metal skin?


texts: What is the ultraviolet signature, if any, of aircraft and jet engines?

texts:
The Wikipedia article on the FIM-92 B variant of the Stinger Missile says:

  In this version, the infrared seeker head was replaced by a combined IR/UV seeker that utilized rosette scanning. This resulted in achieving significantly higher resistance to enemy countermeasures (Flares) and natural disturbances. Production ran from 1981 to 1987, a total of 600 missiles were produced.

I'm assuming "IR/UV" means "infrared/ultraviolet."

Do aircraft (or jet engines) really have a strong ultraviolet signature? If so, how is it formed? Is it only evident at high airspeeds?

(Also, what on Earth could it be talking about by "natural disturbances"?)


texts: How often do GA pilots use the Autopilot approach feature while landing?

texts: While flying in simulations, I found that using the Approach feature is very beneficial for riding the glide slope (clear weather or not), however, while watching videos of GA pilots, I do not see it performed too often. Which brings me to my question as to whether that is a common practice, or if it is frowned upon unless it is necessary for a safe landing?


texts: How does the hinge mechanism of plug-type pressure doors work?

texts:
Many pressurized aircraft have the type of plug doors that open by first swinging inside,  rotating about at least two axes, then moving through the opening and ending up outside parallel with the fuselage.

I'm intrigued by the mechanism that makes this possible, but I have never been able to really see how these intricate hinges work. As a passenger it's hard to even witness the actual opening or closing of the door. Some drawings are to be found on the web, but none that I know of give a clear understanding of its workings. Does anybody know of a video or an animation that gives some insight?


texts:
This Reddit post shows a picture of a disposable cup that is labeled specifically for use by pilots only:

Is that seriously a thing? If so, why? There's some explanation in that discussion thread about fitting cup holders more tightly, but it doesn't sound like a plausible explanation to me, since the cup holder should be designed to hold the cup properly, not the other way around.