texts: Is aspect ratio efficiency related to the momentum added to the air?

texts:
Many years ago I was taught that for generating lift or propulsion, lower losses were associated with imparting less momentum change to a larger volume of air, and higher losses were seen when imparting larger momentum changes to a smaller volume of air - and that the losses were due to friction (i.e., the air's viscosity).

The propulsive example of this is the commonly-cited turbojet-versus-high bypass turbofan engine comparison, and I had been under the impression that the airfoil example was high aspect ratio versus low aspect ratio wing designs. However, having just learned that this is in fact incorrect (it has to do with induced drag instead), is there in fact any connection at all between the imparted momentum change/volume of air argument and airfoil aspect ratio?


texts: Why do some Airbus jetliners at full thrust sound like turboprops?

texts: When riding an A3xx I always noticed the unique "turboprop" like sound when close to full throttle. Why is that so?


texts: Why do aircraft models end their life as freighters?

texts:
There seems to be a tendency that aircraft models are more long-lived for cargo than for passenger service.

For example, both the A300 and MD-11 are all but extinct in scheduled passenger service, but FedEx and UPS still fly scores of them.

My understanding is that the reason an aircraft model goes out of service is not that the planes are too old to possibly continue flying, but that it becomes economically favorable to replace them with newer models with better fuel or maintenance economy etc. Shouldn't those considerations apply with equal strength to cargo planes?

Which factors contribute to passenger aircraft obsolescence that do not apply equally well to freight?


texts: Why do flight times differ between traveling East versus traveling West?

texts:
Why does it take longer to fly East to West than West to East?
Which factors affect this?
Does Earth's spinning affect the time difference? Maybe the air circulation?


texts: What is the stability of a 777-like plane if the engines flameout and the autopilot disconnects and the pilots don't make any inputs?

texts:
According to Wikipedia:

  If no control inputs were made following flameout and the disengagement of autopilot, the aircraft would likely have entered a spiral dive and entered the ocean within 20 nmi (37 km; 23 mi) of the flameout and disengagement of autopilot.

Does this mean the autopilot automatically disengages when both engines experience flameouts? If so, how likely is it it would enter a spiral dive within 37km of the flameout?

Are there any other control inputs the pilot could have made before flameout that would cause the plane to glide until it impacted the water?


texts: How do AHRS systems meet the "gyroscopic" requirement of 14 cfr 91.205.d?

texts:
EDITED
Among the instruments listed as required for IFR operations in the US FAR is are various "gyroscopic" instruments, including those for the turn coordinator, attitude and heading. In modern avionics, though, there are no gyros. All the inertial sensing is done through some sort of non-spinning resonator (see https://en.wikipedia.org/wiki/Vibrating_structure_gyroscope). How are these things "gyroscopes" within the language of the FAR? Am I misunderstanding what the term means? I thought the "gyro" root meant "to turn in a circle" (as in "gyrate" or the making of the Greek sandwich), which is how heading/attitude/rate-of-turn devices all used to work. Obviously this is a nitpick since the point is to  sense  rotation. But then why does the FAR specify "gyroscopic" as a modifier for the various instruments?
ETA:
The origin of this question was a Sheppard Air test prep q referencing the FAR. Supposedly, all of these questions are on actual FAA exams. Here's another one, which in light of the comments I marked "B" for. But according to SA, the correct answer is "C". So (if SA is correct) the FAA seems to think here that a gyro is actually a spinning object.

(Also, thanks whoever downvoted this, while a People Magazine question about JFK Jr's IR training gets upvotes.)


texts: What is this long Bar/Rod on the Boeing MH-47G?

texts: This MH-47G has a thick, long rod at the bottom left front. What's the purpose of this thing?


texts: Why does "airplane mode" turn off Bluetooth and WLAN if I can just turn them on again?

texts:
On my (Android) phone, enabling airplane mode automatically disables all wireless antennas except for GPS and NFC (I assume the latter is either passive or way too low power for anyone to care about).  In particular, it disables mobile data (4G/LTE, or whatever it has roamed onto), WLAN (WiFi), and Bluetooth.

However, I can turn WLAN and Bluetooth back on again without disabling airplane mode.  Asking the airline, as suggested in this answer, is useless.  During the safety briefing of every flight I remember in the recent past, they would say something along the lines of "You can use electronic devices as long as they're in airplane mode," or very rarely, "You need to switch your electronic devices completely off until we hit 10k feet, and then use them in airplane mode."  But they don't tell you anything more specific in the safety briefing or on the information card (e.g. "WLAN is fine, but keep Bluetooth off" or similar).  At the same time, most airlines clearly want you to turn on WLAN so that they can sell you internet access.

The obvious interpretation is that you can do whatever you want as long as your device is in airplane mode ("They said to put everything in airplane mode, and I did, so I complied with their instructions.").  But that actually doesn't make sense.  I own multiple devices which only have Bluetooth and/or WLAN antennas (e.g. the Nintendo Switch, most smart watches, and probably a truckload of other non-phone devices).  In most cases, you can turn both antennas back on after enabling airplane mode.  At that point, airplane mode is just a pretty little icon that appears in your device's status bar.  It doesn't actually do anything (but is presumably still required).

What is the point of disabling Bluetooth and WLAN if you're not prohibited from turning them on again?  What is the point of even having airplane mode on devices that don't support mobile data in the first place?


texts: Airplane gently rocking its wings during whole flight

texts:
I was on a flight with a regional airline a while ago in a Bombardier airplane (if I recall correctly) where the airplane would slowly and gently rock its wings just a little bit on the whole flight. I wasn't a long flight but wasn't very short either at roughly 2 hours.

It was very comfortable and the rocking made for a very gentle cradle feeling

My question is, why would that be? Is it economical to do so for any reason? Is it possible that the airplane had no autopilot and the pilot was flying it by hand? What could cause such a behaviour?


texts: What to look for in a flight instructor?

texts: I want to make the most of my time and budget. There are ton of flight instructors and the quality has to vary widely. Besides being a competent pilot, what should I look for in a CFI? What are the warning signs of a poor CFI?


texts: Can static electricity affect navigational instruments?

texts: Is it possible for navigational instruments to get affected by static electricity or electrical discharges like lightning? If so, how does this happen?


texts: What is the relation between roll angle and pitch angle?

texts:
I was wondering about roll angle and pitch angle values.
Will I get same pitch angle at different roll angles and vice-versa?

For example. At its initial position, the aircraft is standing on the runway). I got roll and pitch values from a sensor. Lets say X and Y resp. Now, when aircraft is taking off, it is obvious that it will pitch up so  my pitch angle will change to lets say Y1. Now if I look for roll Value, will it be same 'X' or it will be different?


texts: Why do some towers reference departures by compass direction, others by leg of pattern?

texts:
Got my Private about 6 months ago, and I've always wondered - let's say I request a VFR departure to the South, with the active runway being, say, 2. Some towers will give my departure clearance in reference to the requested compass direction, i.e.
    cleared for takeoff runway 2, right turn to heading 180 approved
whereas other towers will reference it to a pattern leg, such as cleared for takeoff runway 2, right downwind departure approved. Similarly, I've noticed pilots based at airports that use the latter convention will follow that convention when making their departure requests. Is there any rhyme or reason behind which convention a tower follows?


texts: Who has authority to close a runway/airport?

texts:
In the recent runway excursion at LGA, visibility was bad, and an airport ops vehicle called the tower to inform them of the excursion and that runway 13 was closed, and then that the airport was closed.

The tower is in charge during normal operations. Who has the authority to close a runway/airport? Is this codified somewhere?

This also applies on a smaller scale, as I've heard of such things as chunks of taxiway pavement going missing.


texts: Can a wing generate lift in excess of its aircraft's weight?

texts:
"For a plane or bird to fly, its wings must produce enough lift to equal its weight. "

I got that excerpt from "https://www.sciencelearn.org.nz/resources/300-wings-and-lift".

My questions:
(1) Can an aircraft wing create lift that is greater than the weight of the aircraft?
(2) If the answer to question (1) is yes, then what happens in such a situation?


texts: Why is the critical angle of attack lower in ground effect?

texts:
Why is the stalling angle of attack lower in ground effect?
Does ground effect more increase pressure on lower side of wing (cushion effect) or more decrease pressure on upper side, or both? So which side of wing more change pressure in ground effect compare to free flight?

(Please don't explain with terms like downwash, tip vortices, wake vortices etc.. I am big supporter of explaining aerodynamics with pressure/pressure fields rather then "past-things"  that happen behind wing.)


texts: How much compensation does an unruly passenger have to pay to an airline if the flight has to be diverted to remove them?

texts:
If a passenger becomes unruly and the captain decides to land and remove that passenger from the flight, how much does the passenger have to pay the airline for the cost?

In addition, what are the reasons for flight crews to decide whether to divert or continue the flight?


texts: What is the cause of tire marks at the extreme ends of runways?

texts:
At LAX, planes (usually) take off from east to west. On the west end of the runways there are dark tire marks.

What is the cause of thesey tire marks? Failed take offs? Late landings? Something else?

See Google Maps of LAX


texts:
I always remember playing FSX as a kid and using the NASA F/A-18, and never thought much about it.  And then I saw the picture of the Space Shuttle on top of the 747 being escorted by these planes.

Why does NASA have these fighter jets?
What are they usually used for?  Military?  Science?  Advertising NASA?


texts: Why does the Convair 990 produce this howling sound during landing?

texts: Watching this video of a landing Convair 990, one can hear a whooshing howl at about 0:11-0:12, as it flares just prior to touchdown (not to be confused with the run-of-the-mill howling that you can hear from 0:13 on as the engines spool down after touchdown); what makes this sound?  Does the CJ805-23 engine have a different sound profile than other engines?


texts: Why don't more airplanes incorporate spiroid winglets?

texts: In typical airplanes, lift induced drag can account for the majority of the overall drag. Why don't more aircraft employ methods to reduce this and specifically why not spiroid winglets? From every source I have read on them, they have shown to increase the lift curve slope by a significant margin, allowing for a more efficient wing that results in less induced drag.


texts: What is the difference between aviation "accident" and "incident"?

texts:
When I hear speaking about aviation crashes, sometimes I hear about "accidents" and other times about "incidents".

What distinguishes them? Is there an international standard that determines how aviation crashes are classified or is it based on national regulations?


texts: What is the reason for the poor low-speed characteristics of sweptback wings?

texts:
I know there are advantages of swept-back wings delaying shock-wave allowing a aircraft to fly faster. However, what are the disadvantages.
I know one of them is that they have very poor low speed characteristics, however I do not know the reason. Another disadvantage will be on the F-100 Super Sabre Dance, do not understand these either.

Can any kind soul explain the disadvantages?


texts: Is the SEPECAT Jaguar's design aerodynamically inferior to more modern jets?

texts:
If we compare the SEPECAT Jaguar's design with the latest jet fighters, what aerodynamic shortcomings do we find in its design? (I'm only asking about aerodynamics, not AESA radars, electronics suites and so on.)

For instance, in what way is the Jaguar inferior to the SAAB JAS 39 Gripen, PAC JF-17 Thunder, or the HAL Tejas? Is it inferior at all?


texts: How does radar detect turbulence and wind speed?

texts:
In an answer to a questions about turbulence this answer mentioned that aircraft use radar to help detect the most turbulent areas of a storm so that pilots can avoid them.

How does radar do this?  Does it have to do with rain inside the storm moving up and down with the wind?  And if so, can radar detect wind speeds outside of a storm at all?


texts: What might the business model be for a hypersonic jet?

texts:
According to this video, NASA and Boeing are doing research into a new generation of hypersonic passenger planes that can travel at Mach 5. The designs look really cool and I would love to see them in the air someday.

What I am curious about is the business model for such a plane. Are they planning on targeting high-end business travelers alone, or could the ability to make multiple flights in a very short time span bring the cost down enough for the rest of us to be able to afford a seat? Or is this another bid for the high-end market alone?

As a side note, whatever the market is for superfast travel, Elon Musk also seems to think that that there is a business opportunity there.


texts: Is it easier to land planes on an aircraft carrier with a high flight deck?

texts:
The Wikipedia page for the USS Wolverine says that the low flight deck of that carrier is disadvantageous for warplane landing, but it was 70 years ago.

Assuming other things (including displacement, length, width and draft of carriers, flight deck length, width and texture.), is it easier to land the latest planes on an aircraft carrier with a high flight deck?


texts:
Looking through NOTAMs. What does SVC TAR/SSR U/S mean? Does that mean I cannot shoot practice approaches in the area?

Here is the NOTAM text:

  07/052 (A0474/17) - SVC TAR/SSR U/S. 21 JUL 12:00 2017 UNTIL 21 JUL
  17:00 2017. CREATED: 20 JUL 12:08 2017


texts: Why is it common to speak of "Concorde" rather than "the Concorde"?

texts:
Suppose you researching a book on the history of Boeing B-17.

Suppose you researching a book on the history of the Boeing B-17.

Which of those sentences sounds more complete and correct?

OK, so why on an hour-long PBS documentary on the Concorde, were people constantly talking about "Concorde" this and "Concorde" that, as opposed to "the Concorde" this and that?

It is easy enough to find similar examples on Aviation SE.  Just start to enter any proposed new question with "Concorde" in the titlea and you'll see what I mean, in the long list of "Questions that may already have your answer".


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

texts:
This weekend I was on a Airbus A319, and I noticed that the flaps have small extensions at the location of the shockbodies (indicated in the picture with the red circles)
I was wondering what the reason is for these extensions?
My guess is that it could be to compensate for the lower local lift generation caused by the presence of the shock bodies, but I'm not sure. I'm also interested in knowing why they have different sizes at different locations.


texts: gear down during takeoff for extended period of time

texts: Normally when an aircraft departs, the landing gear is retracted shortly after the aircraft is airborne. While watching aircraft departing from an airport in my city, I noticed, that occasionally the pilots leave landing gear down for many miles (10NM or possibly more). What is the reason for this, are they trying to cool down something?


texts: How to decide on which side of the runway the approach path indicator (VASI, PAPI) are placed?

texts:
This answer provides pictures and drawing of implementation of both PAPI and VASI. In all pictures I found, I cannot figure if there is a rule to put those lights on the right, on the left, or on both sides.

Is there some rules to decide if the path indicator lights should be placed on the right or on the left side of the runway?


texts: What is the criteria for selecting BNR or BCD as data encoding in ARINC429

texts: I was going through ARINC429 part1-18 and found all the labels that are defined along with transmission bit and data encoding. What is the criteria for choosing BNR or BCD for data encoding ? Why are some BNR while rest are BCD ?


texts: Are both RVR and visibility minimum required for CAT I ILS?

texts: Is it required to have both RVR and visibility to be more than minimum for ILS CAT 1 or one of them is acceptable. If both required which one has priority.


texts: Where can I find more about a cargo pickup technique that doesn't require landing the plane?

texts:
A number of years ago, I read about a technique for cargo pickup and recovery at remote sites using a low-and-slow-flying plane.  The plane would enter a slow orbit around a point on the ground and lower a bag to the ground on a long (hundreds of feet?  A thousand feet?) line.  Once the bag was down, the plane would maintain its turn around a point so that the line stayed slack and the bag stayed in position.  Cargo (perhaps mail?) could be retrieved from or placed in the bag, then once the transfer was complete, the plane exits the circle and lifts the bag.  I'm a lot less clear on that part.

However, I don't have any idea where I read about this, and haven't been able to find any more descriptions of this.  Can anyone tell me if this technique is real, what it's called, where/when it's been used?


texts: What is the current status of the deployment of RNP 1 and RNP 2 airspaces and approaches in Europe?

texts:
Is there an overview of the deployment of RNP 1 and RNP 2 airspaces and approaches in Europe?

I'm looking for a map, that shows this information. Maybe even 'special' solutions that are not quite RNP.


texts: How do I know if I'm able to use LPV minimums on a GPS approach?

texts: Many GPS approaches have lower descent minimums labeled LPV. How do I know if my aircraft is equipped to allow me to fly to those LPV minimums? And while we're at it, it would be good to know which minimums to use from the whole array of minimums found on GPS approaches.


texts: What if all passengers move from one side to the other?

texts:
Given the question What happens when all passengers jump at once?, I wonder what would happen if they all moved from side to side. If all the passengers moved from the front to the tail, or the other way around, there might be balance problems, but what if they moved from right to left (or vice versa)? I imagine the fuselage is not wide enough for this to seriously affect the aircraft's balance, but I would like confirmation for this assumption.

To have the greatest visible effect, the answer may focus on aircraft with relatively wide fuselages (for instance, A380, B747, B777). Maybe the effect is more visible for aircraft with smaller wingspans, thus, answers may also mention GA  aircraft with a large enough body-width-to-wingspan ratio (the opposite of a glider).


texts: What are the consequences of throttling up past 100% of N1?

texts:
The B737 is probably my favorite aircraft and I'm always sure to never throttle past 100% of N1. I was told the aircraft is pretty much totaled if you take N1 past 100% but you can eke out that extra power for emergency purposes. Is that true? What are the consequences of exceeding 100% N1?

And what numbers should I be paying attention to for takeoff in a 737?


texts: How do police/ambulance helicopters communicate with ATC?

texts:
I was watching some police programme on TV the other day, with an air chase that had the police helicopter crew on their toes; having to perform a lot of sudden maneuvers.

How do police, or HEMS (medical), helicopters communicate with ATC? I presume they get priority, but do ATC clear other traffic out of the way? Is there a comms person/navigator on-board? Do they simply "see and avoid"?


texts: Do pilots turn off the engines during de-icing?

texts: During winter operations and de-icing are the engines (jet engines) usually in operation? If not, what is the reason for that? Also I was wondering if the engine nacelles require de-icing since I have never seen them being spryed in any video footage.


texts: In case of a drone strike with an airplane below 400 feet, who is at fault?

texts:
If a plane is flying VFR (see and avoid) below 400 ft, and the pilot collides with a drone due to not seeing the drone until it's too late to take evasive action, then would the pilot be at-fault for insurance purposes? Would the drone operator (or the pilot) have violated any federal regulations for not keeping clear of the other craft?

Conditions:-

Class E or G airspace
out of the 5nm radius of an airport
sparsely populated area
operator of drone is not within 500 ft of where the collision occurred (i.e. for the purposes of FAR 91.119 (c)).
I have a smaller piston engine plane in mind, but I'm assuming that the outcome would be the same for faster jet aircraft too


texts: Why is there such a difference between the study material for the FAA and EASA ATP knowledge tests?

texts:
What's the difference between the FAA & EASA ATPL written/knowledge test?

The FAA test seems way easier; you just study the Gleim which has 1650+ multiple choice questions and composed of 1,048 pages.

The EASA test which seems very difficult; you have to study the complete set of Jeppesen EASA ATPL training which is 15 manuals/books and composed of almost 3,900 pages!!

So why is there a huge difference between the study materials for the various tests?


texts:
I watch STOL pilot champs Zenith CH701 here.

The engine power are: 130 HP, 80 HP, 120 HP and 100HP, respectively. Amazing. As per my observation, the third airplane takes off in a distance shorter than its length. It uses an 120 HP engine. I tried to search over the net how long the required runway is to make it take off. Unfortunately, I could not find it. But I believe that should be longer than its length.

What are the technical requirement to make an airplane able to STOL?


texts: Why are propeller driven aircraft commonly built with a higher wing aspect ratio and a straighter wing angle?

texts: Why do propeller driven aircraft (especially smaller ones like fighters) tend to have a narrower wing with a higher aspect ratio and a more perpendicular wing angle in relation to the body, whereas jet powered aircraft have a broader wing with a lower aspect ratio (a more "delta" shape) and also more angled? Does it have something to do with the operating speed and aerodynamics?


texts:
Every time I have flown and sat in a window seat, I have noticed this small tube at the base of the window.

It looks like it might be either metal or a small air pocket, but I'm not sure. I've been seeing it for years and always wondered what it is.

What is this "tube" embedded into airline windows, and does it have any purpose?


texts: How high could Concorde potentially reach by going fast and pulling up?

texts:
If Concorde was travelling at mach 2 and FL 600 then pulled up, it would enter a trajectory that went above its normal flight altitude before diving back down. I assume that it couldn't pull up to full control surface deflection in those conditions without the wings folding, so without damaging anything, how how high could Concorde go using this method? Is there a way to calculate/estimate this, or is it only provable by testing? I've searched google for answers but I can't find anything on this subject.
(An unrelated question that I couldn't find an answer to: what was the structural G limit of Concorde at cruising speed)


texts: Why couldn't Air Moorea Flight 1121 use pitch trim to land safely?

texts:
On August 9th, 2007 an Air Moorea Twin Otter crashed into the ocean. The cause of the crash was determined to be loss of pitch control after an elevator cable snapped.

In my world (Cessna 152), if an elevator control broke I would be pretty sad, but the pitch trim tabs would probably allow me to put the plane down safely somewhere.

As far as I could tell based on my research, the Twin Otter is equipped with a pitch trim tab (aircraft are required to have them, but they can come in a variety of forms). Why couldn't the pilot use pitch trim to descend safely?

--EDIT--

In my checklists, I am required to "set trim for takeoff" in the engine run up. What is the point of this step if that trim setting doesn't hold the proper attitude for not falling out of the sky?

--EDIT #2--

In a highly hypothetical follow up question, would it have been possible, with 400' of altitude, for the pilot to go so hard nose down that he could pull out in an inverted configuration and fly the plane safely that way (the only cable that snapped was the elevator-down cable)?


texts: Can an armed door be opened from outside an airliner?

texts:
This is a continuation from this question, whereby it discussed the meaning and significance of an armed door.

Now, is it possible to open an armed door from outside, for example, if for some reason the passenger or crew are incapacitated, due to inhalation of poisonous gasses etc.


texts:
Understand that the APS5000 used in the B787 is the first all-electric APU for large commercial aircraft.

Source: http://www.pwc.ca/en/engines/auxiliary-power-units

Sorry if this sounds too amateurish, but what exactly is an 'all-electric APU' and how does it differ from past traditional APUs? Does the design allow it to generate the higher electric power required for the B787 and more electrical aircraft?

Any help would be appreciated, thanks!


texts: What advantage might interplane-strut mounting offer to ailerons, on the Curtiss Model F?

texts:
Glenn Curtiss's 1912-1918 Model F biplane flying boat has large ailerons on the struts between the wings, not contiguous with any other flying surface.  Did this aileron position have any advantage that either he knew of or that we now know?
[Per SupBruh's comment, contrast this position to conventional upper-wing position.  Lower wing was rare even then, and particularly for a seaplane where an aileron this big would hit the water when deflected.]
He knew about wing warping, so he knew the effectiveness of camber (hinging an aileron at a wing's trailing edge) as compared to just changing an airfoil's angle of attack.  He knew how to make a hinge: this aircraft uses them at rudder and elevator.
He also knew about modern ailerons: in 1908 he flew an aircraft with them.
Maybe he chose such a large chord for the ailerons to try to increase their authority.  Photos suggest that the airfoil was just a flat plate, which stalls at a deflection angle much less than that of a conventional aileron.  But the drag from a stalled aileron that big would produce scary adverse yaw.


texts: Are there any aviation vehicles for Internet service?

texts:
Facebook announced on Wednesday (2018.06.27) that it is ending its Aquila drone program after four years of development. Aquila was a high-altitude platform station (HAPS) system designed to deliver internet in remote locations.

The solar-powered Aquila was designed to fly between 60,000 and 90,000 feet and to stay aloft for up to 90 days at a time, while providing broadband coverage to a 60-mile-wide area on the ground. The drone flew twice in 2016-2017.

Do any organizations or governments have or plan to provide Internet service via a drone or other aircraft?

source


texts: Why does spin recovery involve cutting the throttle?

texts:
When recovering from a spin, the first step is generally to cut the throttle:

  ... Otherwise, to recover from an upright spin, the following generic procedure may be used: Power is first reduced to idle and the ailerons are neutralized. Then, full opposite rudder (that is, against the yaw) is added and held to counteract the spin rotation, and the elevator control is moved briskly forward to reduce the angle of attack below the critical angle. Depending on the airplane and type of spin, the elevator action could be a minimal input before rotation ceases, or in other cases the pilot may have to move the elevator control to its full forward position to effect recovery from the upright spin. Once the rotation has stopped, the rudder must be neutralized and the airplane returned to level flight. This procedure is sometimes called PARE, for Power idle, Ailerons neutral, Rudder opposite the spin and held, and Elevator through neutral. ...  [Wikipedia]

This is extremely counterintuitive; given that another vital step in spin recovery is to apply full down elevator1 to get the nose down, one would expect that the blowback from the engine (especially for tractor-propeller aircraft) would aid in recovery by striking the underside2 of the deflected elevator, and, thereby, pushing the tail up (and the nose down), making it seem, at first glance, that it would be best to firewall the throttle in order to get the tail up and the nose down as quickly as possible.

In addition, even without the contribution from the elevator, applying full throttle would:

drag the aircraft forwards through the air, increasing the forward component of its motion and decreasing the angle of attack seen by all the various parts of the aircraft;
for tractor-propeller aircraft, blow air at high speed backwards over the wings, dramatically lowering the local angle of attack felt by the wings.

Both of these effects would tend to destall the aircraft and transform the spin into a boring old trivial-to-recover-from spiral dive.

So why do spin-recovery procedures for most aircraft generally call for cutting the throttle, rather than firewalling it?

1: Or, if spinning while inverted, full up elevator.

2: Replace "underside" with "upper side" if spinning inverted.


texts: Is the well known textbook-formula for net-thrust oversimplified or do I have a misinterpretation?

texts:
In order to understand how Jet-Engines works I came across the "famous" formula for net-thrust:
https://en.wikipedia.org/wiki/Turbojet#Net_thrust
$F_{thrust} = Q_{out} \cdot v_{out} - Q_{in}\cdot v_{in}$
From well known physical law about momentum this sound quite reasonable for me.
But now assume an empty cylindrical chamber with nozzle at the end, mounted statically in a wind channel:

Regardless of any details, just by continuity equation we must have
$Q_{out} = Q_{in}$
and
$v_{out} \gt v_{in}$
Nevertheless, this construction would not produce a net propulsion in left direction. It it were true, we just had to put this "empty" construction on a plane...
I was thinking over that quite a time and become already a little crazy.
Where is my mistake? Or is the formula above not the whole truth?
Anyway, I'm not sure if
$v_{in} = v_{air}$
although it sounds reasonably for me.
But even when I take the formula
$F_{thrust} = Q_{out} \cdot v_{out} - Q_{in}\cdot v_{air}$
a left thrust would be produced, whenever
$v_{out} \ge v_{air}$
Is this the key-factor where I'm wrong?


texts: What is the largest aircraft ever put in a spin?

texts: What is the largest aircraft, by weight, ever deliberately put into a spin?


texts: Do pilots ever suffer PTSD after emergency landings?

texts:
I have watched a few documentaries about plane crashes where the whole crew and passengers survived. Of course the passengers are usually all scared, but what about pilots?

Do they ever suffer from Post Traumatic Stress Disorder (PTSD)? Are they ever too scared to fly again after such landings?


texts: On which point(s) in a jet engine does the reaction force act?

texts:
Turbojet and turbofan engines are part of a family of engines referred to as reaction engines to emphasize the fact the aircraft is pushed forward mostly by Newton's 3rd law of motion when gases are accelerated.

Diagram of a turbofan jet engine, source
On which point(s) does the reaction force act?


texts: Did Airbus do anything about Qantas Flight 72?

texts:
I recently read about Qantas Flight 72
I'm wondering if Airbus did anything else besides release an Operators Information Telex? And I'm also wondering if this threat is still possible today? One last question, does the new Airbus A330-900neo and new Airbus A340 BLADE have the same ADIRU system as the other Airbus A330 and Airbus A340 or was something changed or fixed?


texts: What happens if Solar Impulse II encounters un-expected head wind and runs out of battery power?

texts:
I noticed that battery charge level dropped to fair levels in some occasions in this article. It dropped to around 20% at the end of day 5 before morning of day 6.

To what extent will a flight be affected by unexpected strong head wind that results in lower Eastward ground speed and delaying time to next sun shine and battery runs out?

I tend to think weather prediction is quite good nowadays, what is the plan if this happens on long ocean flight? Does the ocean have thermals where a glider can stay up 'forever' while waiting for morning sunshine?

On Solar Impulse, or similar 'experimental' (at the edge of limits) flights, like the solo circumnavigation balloon flight, do they usually have a 'chaser/spotter' plane flying along?


texts:
Old timers swear aircraft performance can be increased by getting an aircraft "on step" similar to how boats are operated.

They claimed a couple extra miles per hour (airspeed was in MPH then) were common. The "step" was alleged to be a "just-right" angle of attack which
minimized drag and allowed an airplane to cruise at a higher airspeed than normal on the same power.

Can airplane performance be increased by cruising "on step"?


texts: Would a airfoil move backwards if you rotate it vertical

texts:
Lets say i have a wing with an engine attached to it like a propellor.
And now i point the nose of my airplane up untill it is vertical.

Would the wing still generate lift because of the air flowing past it. Resulting in a backwards movement of the entire airplane?

EDIT I am suggesting that the plane is hovering vertical not gaining or losing any altitude.

This may sound very vague, so here an image hopefully to make it clearer:

So just to clarify, the brown thing should resemble a propellor.
the yellow line the horizontal normal orientation of a wing.
and the red arrow the resulted direction of the airfoil.
and the green lines the airflow.

As you may have guessed i am not an expert when it comes to planes and the physics behind it all. So pls let me know if more information or clarification is needed.


texts: Which among the two contributes most of the lift, the upper or lower surface of the airfoil?

texts: I see some explanations that lift is due to the suction of low pressure on the top surface of the wing and deflecting down of airflow on the bottom which results to upward force lift. I wonder, which among the two surfaces (top and bottom) contributes most of the lift?


texts: Are there any regulations on fueling aircraft inside hangars?

texts: My FBO routinely refuels aircraft with 100LL while they're parked inside hangars. I have complained about this being a dangerous practice. My previous FBO required aircraft to be at least 10ft outside the hangar for refueling. Are there any regulations or advice on this?


texts: On FSX flight lesson on climbs and descents, what does "free ride" mean?

texts:
The following is from a lesson on Microsoft Flight Simulator X regarding climbs and descents:

While engine power moves a car uphill, gravity pulls it down. Without your foot on the accelerator, the car's downward speed is determined by the steepness of the hill it's descending. The steeper the hill, the faster it goes. If the hill becomes shallower, then the speed decreases. If the hill becomes too shallow, then some power is necessary to maintain sufficient forward speed.
Airplanes can also move downhill without power.
Just lower the nose, and you'll get what appears to be a free ride (it isn't, but let's not get into that).

I cannot seem to understand what the author meant by the last sentence. Is the author trying to say that descents are not "free" as in descents are not "powered" by the weight of the aircraft and some form of thrust is needed?
I am rather new to the concepts of the physics of flying and may be missing out on something. Hopefully, someone is able to point out what I am not catching. Thanks so much!


texts: What is the function of this small hole on the B737's hydraulic reservoir line?

texts:
This is picture of a B737-800. When you open the bleed system a small amount of air is discharged from this hole (marked with an arrow, lower right). What is it for? And what happens if this hole gets clogged?

AMM Part I Reference 29-09-00, page 3.

Click images for higher-res.


texts: Is it possible to fly VFR above the IMC floor or VFR-On-Top without a specifically filed route, both using an IFR flight plan to go through IMC?

texts:
*Note, I'm not trying to recommend this, but I am curious if it can be done.

In this question, Steve V.'s answer made me wonder about this:

One time during my commercial training, my instructor and I received an "area clearance" over downtown Nashville for simulated aerial photography, which allowed us to circle over downtown with visual reference within class C airspace as we wished with no defined route.

In the above case, we were not on an IFR flight plan, nor were we above the IMC floor.

Scenario 1:

Is it possible to get an IFR clearance for an area as VFR-On-Top, without having to file a routed flight plan with fixes, effectively allowing an instructor and a student to practice with their own spontaneous navigation choices in VMC at an altitude above IMC conditions?

Scenario 2:

Same as above, but foregoing the VFR-on-top and accomplishing it purely as IFR.

Scenario 3:

File two IFR flight plans, cancel the first one once above clouds in VMC, do your thing, and then receive the next IFR flight plan clearance to shoot the approach back down.

Are any of those options?


texts: Do F-22 and F-35 use force sensing flight sticks like F-16?

texts: Do F-22 and F-35 use force sensing flight sticks (as opposed to flight sticks that actually deflect and sense movement), like F-16?


texts: What is the Dimension of Equilibrium Space in Longitudinal Space?

texts:
Full untrimmed Flight Dynamics model of an Airplane is separated into two separate systems: Longitudinal and Lateral.

When the untrimmed model in Longitudinal direction, which is six dimensional, is trimmed (f(x,u) = 0), what is the dimension of the equilibrium space? Is it two dimensional? If yes, then why?

x = state vector for longitudinal direction
u = control vector in longitudinal direction


texts: How can I correct an expected climb rate for density altitude?

texts:
If a flight manual (for a naturally aspirated piston engine plane) gives a figure for a best climb rate at standard temperature and pressure, is there a way to adjust that figure for a different density altitude?

(I'm thinking there must be, but I can't find such a formula anywhere. Assume the same speed, weight, etc.)


texts: What's the record for total commercial flight-hours?

texts:
Which airline pilot has the record for the highest number of total airline flight hours globally?

I found an article on Ed Long who had over 65,000 hours, but I'm only interested in airline pilots (also, most of his hours were at an altitude of under 200ft...)


texts: Why does XKCD say that autogyros will crash if the pilot reacts to a stall as in a normal airplane?

texts:
This recent XKCD comic is all about autogyros.

Image is copyright XKCD, licensed under CC 2.5 BY-NC

The note at the bottom is what got my attention

  Extremely safe, unless you do the one thing you instinctively do to escape a stall in a normal airplane, in which case it will crash immediately

So what is that one thing, and why does it not work in autogyros?


texts: How to determine the maximum servo torque required for a nose gear?

texts: It's pretty much it. I know how to calculate the friction force on the nose gear for a three-point landing condition using the method set forth in Structural Loads Analysis for Commercial Transport Aircraft Theory and Practice, by Lomax. To calculate the torque I am looking for, would I just take the cross product between the friction and the radius of the nose gear?


texts: Did we get closer to another plane than we were supposed to, or was the pilot just protecting our delicate sensibilities?

texts:
Yesterday, April 28, 2019, I was flying on Alaska flight 557 from LAX to PDX.

About an hour into the flight (near the California/Oregon border) I was looking out the window and saw a jet travelling the opposite direction from us.  It was travelling exactly the opposite direction of us and I saw it when it was ~45-60 degrees forward of us.

Within a couple of seconds of my seeing it, we banked sharply to the right.  It was not a violent turn; An answer to this question describes true evasive maneuvers as, "those of you not strapped down would have been hurled to the ceiling or slammed to the floor and your stomach would be heaving in a different direction from the rest of you." - and we didn't have anything like that.  I'm not sure I would have even noticed the turn had I not been looking out the window.

However, it was a pretty sharp mid-flight maneuver, and because I was over the wing, I didn't get to see the other airplane at closest approach because the wing blocked my view.  I would estimate that it was about 3-5000 feet away from us.  I felt like he was at pretty close to our altitude, but again, as the linked question says, that's hard to say for sure.

The linked question points out that distances and altitude differences are hard to judge.  That's fair, so I'll offer the following bona fides:

I live about half a mile from a commercial airport, perpendicular to the end of the runway, so I have a good idea of what jets that are half a mile away from me look like.  I would estimate that the other jet was a bit but not a lot further away than that.
If two jets pass by each other at 1/2 mile, and you can see another jet that is 60 degrees in front of or behind you, and he, like us, was travelling 480 mph, he would have been in my field of vision for 6.5 seconds.  That sounds about like what I remember.  At 3 miles, that number turns into 40 seconds.  I don't remember the exact amount of time, but my initial estimate before I did this math was 8 seconds.

I could imagine our pilot banking the plane simply to lessen the odds of the passengers noticing a safe encounter, as even a safe encounter leads to awkward questions on sites like this.

So, my question: Did we have a near miss, or was this a standard close-but-intended encounter?


texts: What is the bulge under the engine of the Mirage III and some of its variants?

texts:
While attempting to create a Kfir in 3D modelling software, I noticed a bulge under the engine on the reference picture (a 2D side view) I was using, which I initially assumed to be a fin. After looking at some 3D images of it, however, it is far too wide to be a fin:

There is a similar bulge in the same position on the Mirage III:

The Atlas Cheetah and Mirage 5 both have a bulge in that position as well, although every non-Mirage-III-based Mirage seems to lack it. The Mirage 2000 has a bulge in a similar location; however, it appears to be much smaller:

My initial thoughts were either ECM or some kind of fuel tank. Does anyone else know what it might be?


texts: Is it possible that a aircraft can fly without having wings? I am wondering if somehow it can fly then will aircraft will be able to maintain the balance.


texts: I'm curious if there is ever a purpose to use full flaps like that? Was it a bit of an overkill?


texts: I have an engine that took a prop strike (previous owner).  The engine was completely disassembled to check the crank, case, etc for damage.  It was reassembled with new parts, bearings, rings, etc., overhauled cylinders, and mags with fresh 500 hour inspection. The logbook entry says "0 SMOH Lower End."  What else would be required to list this engine as simply "0 SMOH?"  How should I track this in my log book?


texts:
How reliable are WWII turbochargers? Does adding them to an otherwise reliable engine, e.g. the P&W Double Wasp and the Allison, decreases the overall reliability of the engine? Are they well made enough to sustain the heat of the exhaust (my guess from rough calculations under the presumption of adiabatic combustion puts it in the 800K-1200K range) without creeping? My impression is superalloys are not around until about 1950s.

Is the relative unreliability of the turbochargers (turbine wheel to be exact) the reason why the great majority of high-performance WWII engines opted for supercharging as supercharger operates in the cold end of the engine only?


texts: What is advantages of a wing mounted engine in comparison to tail and fuselage mounted engine?

texts: What is advantages and disadvantages of wing mounted, Tail mounted and fuselage mounted engines?


texts: Why is rotating engines in opposite directions more important for a propeller-driven plane than a jet?

texts:
From here it is seen that many multi-engine propeller planes spin their propellers in opposite directions. To avoid producing "left" and "right" types of the engine, a gearbox is fitted.

In contrast, jet engines usually spin in the same direction. Why is the spinning direction less important for a jet engine than for a propeller engine?

A Boeing 777 may have a turbine fan as large as 325 cm in diameter (GE90-115B). Not every propeller is that large.


texts: Why are the stabilised approach criteria different for an instrument approach and a visual approach?

texts: My question mainly pertains to the simple altitude difference. Why is the stabilised call given at 1000ft for an instrument approach and 500ft for a visual approach?


texts: Which is the difference between IMA (B777) and Open IMA (A380)?

texts:
The integrated modular avionics concept (IMA) was developed by Boeing for its B777. Open IMA is an improved version developed by Airbus starting from A380. Which are the differences? For example, I got that the network is optical fiber for IMA and Ethernet/Avionics Full-Duplex Switched Ethernet (AFDX) for Open Ima: why?

I know that the question may be too broad and not very easy, so I would welcome even some links to deepen the argument.

Moreover I would like to understand: where is it used IMA nowadays? Only in B777, or even in B787 and new generation B747 and so on? Idem regarding Open IMA: only A380 or even in the A329 Neo?

If Boeing and Airbus have these new systems, what do you have in all other companies? Embraer, Eurocopter, Tupolev etc.


texts: Why are the angle-of-attack sensors on most airplanes mounted on the forward fuselage rather than at the wing roots?

texts:
A source of reliable angle-of-attack information is important for airplanes, as flight at an excessively-high angle of attack can cause the airplane to stall, which is generally considered to be an undesirable occurrence.  To this end, airplanes generally have several redundant angle-of-attack sensors (usually consisting of vanes that stick out into, and align themselves with, the airflow, but sometimes using complicated pressure-sensing mechanisms instead) to provide warning of a dangerously-high angle of attack.

These sensors, however, are generally mounted on the forward fuselage, below the cockpit, which is not, for most airplanes, where high angles of attack actually cause problems.  Where AoA matters is on the wings, which produce the lion’s share of the airplane’s lift and which need to be kept from stalling, and where the direction of the local airflow is not necessarily the same as that experienced by the AoA sensors on the forward fuselage.  Exactly how not-same it is depends (as do quite a lot of an airplane’s aerodynamic properties) on the airplane’s airspeed, which is why readings from nose-mounted attack-angle sensors need to be adjusted to correct for the effects of airspeed, which is why (for instance) high-attack-angle protection on fly-by-wire Airbusses is inoperative in the absence of valid airspeed data.

Mounting the angle-of-attack sensors at the airplane’s wing roots, rather than beneath the cockpit, would allow the AoA to be measured directly right where it counts, eliminating the need to correct their readings for airspeed and allowing accurate attack-angle measurement even without any airspeed information at all, so why do most airplanes still have their attack-angle sensors on the forward fuselage instead of the wing roots?


texts: What could cause a rear twin-jet's throttle to oscillate on descent?

texts:
I rode a smaller twin-tail-engined jetliner for a few short hops last month, and I noticed that their airport approaches are much rougher than the widebody airliners I am used to. I believe that it was an MD-80 with United Airlines.

As soon as the pilot began the descent, it seems like the he/she was going wild with the throttle; the engines would appear to idle for 10 seconds, then suddenly and audibly power to full for another 10 seconds, and the cycle would repeat until we were right above the runway. I know that this was not crew specific because I took the commercial flight on 6 different occasions on three different routes.

Question: Why did the pilots increase and decrease the throttle so rapidly and so many times on descent to the runway?

edit: Terrain: flat, Atlanta area; Meteorological conditions: heavy cumulus, twice during the night and the other four during dusk, light to moderate rain under and in the clouds. The clouds had no breaks and often had a strange formation where in some areas they would rise much higher than others. Imagine a series of mountains and valleys with several? miles of distance between cloud peaks and cloud dips.


texts:
I think this is an okay place to ask this. Let me know if it is not.

In about a month, my school is going on a school trip and the plane ride is going to be around 15 hours. I was think about setting up a small network on the plane so that we can chat on a locally hosted program.

I would do this by bringing a small router and hooking it up.

Is this against the rules of most airlines and do you think I could get in trouble?


texts: Does the "bat wing" aircraft paint design have a proper name?

texts: I would like to do a web search for different planes that have utilised the "bat wing" paint application noticeable on the wings below?  What keywords should I search for?


texts: Why do some airfields not have a climb gradient for LPV?

texts:
Can anyone advise why for some airfields there are minimum approach climb gradients for LNAV with none for LPV, while at other airfields there are minimum approach climb gradients for both LPV and LNAV?

This is an extract from the plate for Campbeltown - EGEC.

For other airfields, MPA gradients are also given for the LPV as well as LNAV such as Islay - EGPI, shown below.


texts:
Aileron droop helps to:

A - prevent upfloat
B - correct adverse yaw
C - get control feel
D - compensate drag

Please mention the most appropriate choice and only one correct answer. With a brief explanation if possible!


texts: Are there any apps for easy Part 135 Flight Time and Duty Period calculations?

texts:
I need a solution to quickly and easily assist me in calculating Part 135 duty time.

I am a charter broker and presently use estimations for my own consideration, but rely on advice from operators to provide informed consultation to clients.

It takes me too long to arrive at my own estimations, and I feel like there would be a tool out there designed to save me time. I saw a couple of apps in the App Store, but I wasn't impressed and would like your opinions.


texts: Why should a test flight be performed when the propellers are changed?

texts: From this question I've learned that after a propeller change the plane should go through a test flight. Why is this?


texts:
How the AGL altitude changes with changed QNH? I'd like only to confirm or correct my intuition..

Airplane is maintaining certain FL with some QNH, its instruments are showing some AMSL. Now the airplane enters area with lower air pressure, but keeping the same set QNH. How the real AGL altitude changes?

My intuition is that altimeter is effectively showing certain pressure. If the atmospheric pressure drops (e.g. from 1013 to 990), to show the same measured pressure (altitude) the airplane has to descend.  Then the airplane is having lower real AMSL than displayed on instruments.

Is my intuition correct?


texts: Is the aircraft used by NOAA specially modified?

texts:
I have just seen this short video showing "NOAA hurricane hunters" flying through current hurricane "Irma".

My guess is that normally an aircraft would not be able/allowed to fly in winds sustained wind speed of 160kts, gusting to 180+kts, with the associated turbulence.

Is this aircraft modified in any special way? For example, reinforced structure, or specially designed engines?


texts: What is different between a Cat IIIA, Cat IIIB, and Cat IIIC ILS approach?

texts: In terms of aircraft equipment, approach minimums, procedural differences, and anything else relevant, how do the 3 types of a Cat III ILS differ from one another?


texts: What happens if full collective pitch is suddenly commanded on most modern helicopters?

texts:
Related, but not the same: What happens when you apply full cyclic + collective?

If the pilot suddenly applies full collective pitch on a turbine powered helicopter, will the engine stall? It seems from the other question, that this is not typically mechanically limited, so it is possible to force this onto the helicopter. However, does it cause the engine to stall? Any other problems?


texts: What wing spacing is best for a tandem wing configuration?

texts:
I want to build an airplane but I have limited power(25-28hp). This means that I have to build a power efficient airplane and I finalised on building a tandem airplane. I've read that the wing spacing(distance between the trailing edge of front wing and leading edge of aft wing) should be about 30-50% of the wing span.
So my question is, what wing spacing is best?
I suppose that will help me estimate the length of the aircraft from prop spinner to rudder as intend using wing tip rudders


texts: How are helicopter rotor blades balanced?

texts: Reading this answer, I realized that the balance of a rotor is critical. When one blade is changed, the whole balance of the rotor may be affected. Moreover, I doubt 2 blades are exactly the same. For a car's wheel, we add small weights, but what about helicopter's rotor? Adding pieces to the rotor may affect its aerodynamics.


texts: What is so special about new Russian jet engine called PD-14?

texts:
I think PD-14 engine is being promoted by Russians as something extraordinary.

What is so special about PD-14 that the West doesn't have?

Can you explain this in layman's terms?


texts: Is there a serious effort underway to move from a highways-in-the-sky approach to a mesh-network approach?

texts:
As far as I'm aware, there are certain "motorways" or corridors which air traffic uses, rather than navigating more directly from origin to destination.
I remember listening to a documentary which mentioned that in the early days of the standardisation of flight, the navigation system was being decided. The Americans put forward the "motorways" system because they already used intermittent beacons to guide aeroplanes across the country, which naturally form a kind of road system analogue.
While the British (or Europeans) put forward a direct point-to-point system.

Anyway, the US won, and everything was hunky-dory until we get to today with our extremely crowded skies. So the documentary went on to say that investigations were underway into a new system in which each plane communicates with the planes around it continuously, forming and reforming impromptu mesh networks to avoid collisions. In this way, planes can fly more direct routes and potentially save time and fuel.

My question is whether or not this suggestion is feasible, is it being investigated, and is there a push to move towards it at a level which could affect the international air community?


texts:
(Source)

The propeller on the Linke-Hofmann R.II (1919) holds the record at 6.9 m (22 ft 6 in).

What are some of the largest propellers post-WWII? Top 5 or so.


texts:
I am currently modelling an aero engine and require the weight breakdown of the individual components, I have the dry weight of the engine and need to verify the pylon and nacelle weight.

Raymer has presented an equation for the weight of the installed engine in his book
W installed engine = 2.575 *W engine^0.922*Nengine.

Does this include the pylon ?


texts: Why is there an altitude limit if we have an IDG failure on the A320?

texts: In my company’s MEL there is an altitude restriction if we have an IDG failure of 33500 feet why is that?


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

texts:
For example, if climbing (or descending for that matter) at 3500 fpm, will the AP switch to ALT ACQ mode at the same point it will as when climbing or descending with 1000 fpm? Or does the point of the switch is variable and depends on the ROC or ROD?
I am specifically interested in the B737NG.


texts: Why is a 737 Original speed-restricted below 10 kft with inoperative windscreen heating?

texts:
According to this page on the 737's operational limitations, the Original 737s (737-100/-200) are limited to 250 KIAS below 10 kilofeet if the windscreen-heating system is inoperative:

Anti-Ice & Rain
[...]
737-1/200:
[...]
Window heat inop: max speed 250kts below 10,000ft.  [My emphasis.]

Why is this?


texts: How do I track and visualize aircraft from home?

texts:
I have a R820 USB SDR and I am using ADS-B to track aircraft flying near my home.  I know I could also use ACARS to track nearby aircraft.  Are there any other aircraft signals I can monitor (doesn't necessarily have to give aircraft location, just info)?

Thanks!


texts: Where can FAA Letters of Interpretation be found?

texts: The FAA issues Letters of Interpretation and Chief Counsel Opinions in order to clarify existing rules and regulations.  Where these can be found and searched when looking for clarification of a rule?


texts: What is the format of data stored by a Flight Data Recorder?

texts: Is the raw data fetched from the FDR available only in binary format and if so what are the software tools that are used to convert it to readable format?


texts: Is it true an ILS CAT IIIc can automatically taxi-in an aircraft?

texts:
I've always wondered how would the theoretical (since no airport/plane has it) ILS CAT IIIc guide the plane off the runway? I mean from the perspective of radio signals. What component in the ILS system can help taxi off the runway after landing?

AVweb and other sources mention that:

  CAT IIIc means an actual zero visibility landing because the airplane not only can land and stop itself, but can also automatically taxi in to parking.


texts: Why can't they just land on the helicopter's floor? If it's for stability, they could still use skids which are shorter than what is commonly used.


texts: Do multi engines face the torque effect? What about jets?


texts: What's the point of the Total In-Flight Simulator?

texts:
Picture of the contraption:

Source: wikimedia.org

After a quick research, and Simon's link, it turns out to be a simulator for how different aircraft would handle. And was useful is simulating crosswind with the fins installed mid-wing.

If you already have the preliminary aerodynamic data (which won't change mid-testing) to simulate different planes, what's the point of taking that data in the air vs. a ground based simulator?


texts: What is the purpose of thinner airfoils used near wing tips?

texts:
I know that a thicker airfoil at root will strengthen the root spar but what is the reason behind using thinner airfoils at the tip?

Is it because thinner airfoils have higher stalling angles of attack? If so, why?

Comparing both thick and thin airfoils, who generates more lift and why?

Also, my final question is that in what kind of designs would such a change of airfoils be recommended? I'm currently working on designing a high lift wing (selig s1223 airfoil) for delivering a payload of about 15kgs. with the total aircraft weighing about 20-22kgs. Would changing the airfoils in my wing design be recommended?


texts: Are these two aircraft too close to each other?

texts: One aircraft is taking off and another is quick to land after it. Are they within safe limits?


texts: Why does this chart seem to show airports with magnetic variation up to 90 degrees?

texts:
I am trying to understand some plots of the earth's magnetic variation (declination) by trying to correlate what I see in a figure like the one below with the variation reported for some airports. I'm particularly interested in those locations where the figure seems to show an extreme variation of up to 90 degrees. But when I look up nearby airports, I don't see any variations values outside of 22 degrees.

Some locations I have checked are

SOG, Sorong, Indonesia (1.47 degrees)
BWN, Brunei (0.13 degrees)
CMB, Bandaranaike International Airport , Sri Lanka (2.15 degrees)
REC, Recife, Brazil (22.12 degrees)
IVA, Ambanja, Madagascar (9.8 degrees)

Am I misreading the figure? What are some airports with very large magnetic variations? I'd like to compare them with this figure and try to understand what I am missing.

Source: Wikipedia


texts: Can a nonresident American citizen get a Canadian helicopter license?

texts:
Is there anything preventing a non-resident American citizen from taking and obtaining a Canadian helicopter pilot license which could be converted to an American PPL helicopter certificate?

The reason I'm considering this is the current exchange rate is essentially a 25% discount off the listed Canadian price. Sure I have to drive a bit farther, but auto gas is cheap.


texts: Is there any plan to make flights more interactive using smartphones?

texts:
This question might be a little bit off-topic, but I'll give a try.

Me and many people are aeronautics "aficionados" that would love to know about flying data during flight. Today we all have smartphones that run apps for everything: why couldn't airplanes have an internal WIFI for only broadcasting flight data for being displayed in our smartphones (i.e. as if they were cockpit simulators) as well as video streaming from external cameras? Of course this kind of internal network's purpose would be to broadcast data, so security wouldn't be an issue.

Does anybody know if aircraft manufacturers plan to develop such kind of project?


texts: Can jet engine ingest (suck in) concrete from runway?

texts:
In the question Is there any emergency situation in which jet engines would not be shut down before passenger evacuation of a transport aircraft comment says:

  At full engine power, those vortices are quite capable of lifting something the size of a 1-foot cube of concrete from the ground into the engine!

Incredible! Did it really happened? I guess it did not ended up well for the engine. Any links/images?

I found this:

Can a human get sucked into a jet engine? - but concrete is denser than water (human body), so it would be harder to suck in
Can jet airplanes operate on 'rough' airfields? - mentions gravel, not concrete tiles.


texts: Variable versus fixed costs in the airline industry

texts:
I want to list the costs airlines have to sustain by distinguishing them between variable and fixed. Variable costs change in proportion to aircraft usage. Fixed costs show little or no change in proportion to changes in activity.
This is an incomplete list I took from the FAA website (here)
Variable costs:

Fuel and oil.
Maintenance (e.g., maintenance labor, parts airframe/engine/avionics, engine restoration, thrust reverser overhaul, propeller Overhaul).
In-ground and in-flight crew salaries (can also be thought as fixed costs).

Fixed costs:

Parking and hangar fees.
Insurance.
Aircraft modernisation.
Computerised maintenance management program.
Weather service.

Question:
(1) In which category should I put

Landing fees (ATC, runways, taxiways, parking at stand or apron for a certain time (e.g. 2 hours), use of gates / fingers / terminal for disembarking).

Lounges fees.

Scheduling coordination.

Surcharges or rebates in addition of landing fees (for noise, peak-hour operations)

Passenger charges

Administrative cost (managing/issuing tickets, etc.)

Overflight fees

(2) I'm fundamentally confused about the distinction between fixed and variable costs. For instance, landing fees increase with the number of flights and, hence, with the demand of tickets for a given route. Should they be classified as variable costs for this reason? Is this the same reason why fuel and oil, maintenance, and crew salaries are classified as variable costs?


texts: At what intervals do planes land and take off from Chicago O'Hare?

texts:
Is there some data available which shows the intervals at which planes take off and land at Chicago O'Hare?

Just by taking a look around the last time I visited ORD couple of months back, it seems to be one almost every 10-15 secs.


texts: Is there a way to avoid the effects of turbulence?

texts:
I am trying to determine the plausibility of a larger, broad question using a modified plane equipped with a modified E-fan and external electric ultra light weight rail. The power would be collected from the rail by Laser Induced Plasma Channel. The problem is to stay a safe 3-7 meters from the sky rail during flight because of turbulence.

Is there a plane or guidance system that can ensure a smooth and straight line of flight without any shift in position because of turbulence?


texts: Are the ICAO phonetic numbers used anywhere?

texts:
I ran across a table of ICAO (NATO) approved phonetic number pronunciations. As early as I can remember (50+yrs) in the United States "nin-er" is the only one I ever remember hearing in aviation and I don't recall hearing it in the last 30yrs. I recall hearing "Fife" but I don't remember where - perhaps ham radio operators.

I have never heard "tree" (three), "Tousand" (thousand), or "Fower" (four). If I heard ATC say, "maintain 'climb to nin-er humndred'", I would be very surprised. And if they said, "maintain 'tree tousand'", I would think they needed retesting for ICAO English language requirements.

Is there any country, military, or agency that regularly uses the full ICAO (NATO) approved phonetic number pronunciations? Is it taught to any pilots?

source


texts: Does engine failure shut off the auto-pilot?

texts:
After answering this question it got me wondering whether there can be a situation where a complete flameout of engines could cause a serious loss of control if the auto-pilot were to continue to try to maintain altitude despite the loss of power. If it did, presumably by raising the nose and losing air-speed, eventually the aircraft would enter a stall.

Which raises the question, does the auto-pilot automatically shut off in the event of engine failure? Though I suppose it depends on the auto-pilot and the aircraft model.

I do realize the pilot and co-pilot should be very aware something is awry, but I can also see them being rather busy trying to figure out what all the alarms are telling them, and or trying to restart the engines and not notice the AP is setting them up for disaster.


texts:
I assume there's some stupidly obvious reason that I'm missing, but why bother creating RNAV airways when I thought the entire point of RNAV was not needing to fly along a suboptimal preset path?

I can see the need for waypoints, especially around the corners of restricted airspace that you'd need to dodge rather than just flying direct everywhere, but I'd think an RNAV flight plan would just be a handful of such critical waypoints--no "airways" needed.


texts: I'm making a school project where I intend to design and calculate an rc airplane. Reading some books I found something I can't understand, it says that CL/Cd is equal to L/d, but the only possible way to make that true is to use the same surface on Drag and Lift equations. Isn't drag equation supposed to use frontal surface and Lift equation to use wing surface?


texts: Why would a propeller have blades of different lengths?

texts:
The Schempp-Hirth Duo Discus T powered glider has a five-bladed propeller, with blades of different lengths.

What is the purpose of such an arrangement?


texts: What must ATC do, following a reported laser sighting by a plane?

texts:
Supposing a pilot reports having a laser beam shone on them to ATC, what action should they take?

Is the pilot allowed to take evasive action?

Can other planes request clearance to avoid the area?


texts: How long is a winds and temperatures aloft forecast valid for?

texts:
How long is a winds and temperatures aloft forecast valid for and how often is it published?

Also, is there anywhere which says the times of publication and valid through times for all of the aviation weather charts? My google fu isn't helping.


texts: Which one is considered the departure time of a commercial flight?

texts: I was wondering, the publicly announced departure time of a commercial flight, is it the ETOT (estimated takeoff time) or is it the EOBT (estimated off-block time)? Or maybe some other time?


texts: Why can't commercial aircraft have a wing boundary layer suction system?

texts: I've read that NASA's boundary layer suction system on the wings can reduce drag by removing the boundary layer through the suction holes. If this can reduce a lot of drag (hence improving fuel efficiency), then why can't the same idea be used in commercial aircraft?


texts: How did the gyro gunsights of WW2 get the range and lead of a target?

texts:
I just read this article on the gyro gunsight, but I don't understand how it computed range/position to the target and then calculated how much lead is needed.

Surely it must have had radar to get range to the target? But I could only find one mention of radar in the article, and it only pertained to one particular model of the gyro gunsight. Even if so, I don't understand how a radar return is integrated with a gyro instrument.

I understand that a gyro can tell you your roll angle and rate of turn in any or all axes, but the main thing I'm missing is how did it know range and position of the target? It seems only radar can do such a thing and I don't know how radar data could be integrated with a gyro way back in the 1940's. The wiki article even says that these gyro gunsights were developed "just before the Second World War". But I also noticed the article is not that well-cited.


texts: Why does taxiing produce large lateral loads on the 747's engine pylons?

texts:
While reading through a bunch of old AARs recently, I found (in the context of a 1993 747 in-flight engine separation) this interesting tidbit:

  [...]  Boeing engineers report that the modifications will increase the pylon's vertical and longitudinal strength. However, the modification will provide a slight, if any, increase in the structure's lateral load-carrying strength. Additionally, it was provided by Boeing engineers that the greatest lateral loads on the pylons normally occur during taxiing.  [Page 40 of the PDF of the aforelinked AAR, numbered as page 33; emphasis added.]

I'm having some trouble seeing how taxiing would be capable of generating any significant lateral loads on a 747's engine pylons; assuming that one is not attempting to drift one's 747, nor taking it excessively close behind another jet running its engines up for takeoff, taxiing it at a reasonable taxi speed should not produce any large lateral accelerations that would make the engines want to swing on their pylons, nor any significant lateral airloads that would tend to push the engines sideways relative to the wing.

Intuitively, one would expect that the situations placing the highest lateral loads on the engine pylons of a 747 (or, for that matter, any jet with engines mounted on vertical pylons1) to be those involving one or both of the following:

Large, abrupt accelerations from side to side (such as during severe turbulence, as experienced by [for instance] the aforementioned 747 whose engine separated in midair).
Flight at large sideslip angles (in which case the direction of the airflow experienced by the engines and pylons would be out of line with the longitudinal axis of said engines and pylons, generating considerable, though steady, lateral airloads on the engine-pylon assemblies).

So why would normal taxiing produce such large lateral loads on the 747's engine pylons?

1: For a jet with horizontal engine pylons (such as a DC-9 or CRJ-1000), one would instead expect the highest shear loads2 placed on the pylons to be experienced during abrupt pitch changes, high-angle-of-attack flight, large vertical gusts, or (in the mostly-hypothetical case of a jet with wingtip-mounted engines) high-roll-rate manoeuvring.

2: The loads that try to snap the pylon in two, rather than move the engine longitudinally or stretch/compress it out of/into the pylon.


texts: Why does it take so much fuel to start a jet engine?

texts: I just watched an Abrams tank documentary and it said something like it takes "1 liter of fuel for every mile but 39 liters for a startup." Is it true of turbine engines in general that they need a lot of fuel to start? If so, why?


texts: Could higher aspect ratio actually reduce gliding efficiency of a smaller glider?

texts:
I have been building 1 meter wingspan 100g class free flight mono wing gliders with a chord of around 10 cm and a flying speed of approximately 3 meters per second.  So far glide ratios of around 10:1 have been achieved.  The wing thickness is 1.2 centimeters.  The airfoil
has maximum thickness at 3.5 cm from leading edge.  The bottom is flat, but only covered 6 cm from leading edge, leaving an undercambered area the remaining 4 cm to the trailing edge (this design grew out of thin undercambered wings).

So, is there a maximum aspect ratio  (possibly based on Reynolds number calculations and/or "pressure leakage" due to the small scale or low speed)?  Or do we continue to
go for as high an aspect ratio as structurally possible.

Reynolds number for airfoils = Vc/v where V = 3 m/s, chord = 0.1 meter, kinematic
viscosity at sea level = 1.460 × 10 minus 5th power = 20,548 for my model.

A response by Peter Kampf June 22, 2018 to "Is it best to use a thick airfoil or an undercambered airfoil for for slow speed flight" mentioned the Daedelus airfoils DAE 11,
DAE 21, DAE 31, so it seems to be on the right track.

I am getting ready to start a build, would there be an optimal aspect ratio for this
new aircraft?


texts: Which is more efficient: a jet engine or a rocket-powered engine?

texts:
Knowing that rocket powered engines have higher speeds than jet engines, it raises the question: are jet engines more efficient than rocket powered engines?

This is of course in terms of fuel consumption per distance traveled, as I am curious whether a rocket engine allows an airplane to travel a distance more quickly compared to a jet engine when consuming the same amount of fuel.


texts: Are there any airlines that fly a route that has an arrival time earlier than its departure time?

texts:
Imagine the scenario where an airline flys a short 30 minute route which crosses a timezone going west. They could theoretically leave at 00:15 (local) and arrive at 23:45 local the previous day. I'm wondering if there are any airlines which fly such a route.

P.S. I'm specifically interested in how the airline allows booking such a flight and the UI that is presented, but am leaving this question more general for any flights that do this.

P.P.S. If someone could help with the tags for this question, it'd be much appreciated.


texts: Are en-route ATC callsigns standardized?

texts:
I've seen different callsigns for en-route air traffic control, including Center, Radar, and Control (and Radio?). I suspect the only difference is the geographic location - Center in the U.S. (e.g. Salt Lake Center) and Radar and Control in Europe (e.g. Langen Radar, London Control).

Are there any other differences besides location? (is the location-assumption correct?) If not, why is it not standardized then?


texts: Is gascolator and fuel strainer the same thing?

texts: I am wondering is gascolator the same as fuel strainer, or this two things are bit different. Because sometimes I see one term, sometimes another, and I don't know if I am reading about the same thing.


texts: Where can I find an example of a raw 1090ES message for testing?

texts: Can anyone provide a raw 1090ES Aircraft Operation status message (DO-260B standard) so I can test my decoding logic?


texts: What liability concerns would drive an airplane homebuilder to scrap their plane?

texts:
Via this post by Ron Rapp, I found this video of a plane owner and builder dismantling a GA plane and then scrapping the airframe. The video claims this is because

  after consulting with aviation attorneys and other experts regarding builder's liability, the owner concluded there was only one way out.

However, I'm completely in the dark about - and rather baffled by - what this liability risk would be, and how it relates to the Van's Aircraft lawsuit. What liability would a builder pilot be under in the event of a crash that they would be able to avoid if the plane were factory-produced?


texts: What is the relation between missile fin deflection limit and altitude?

texts:
What's the relation between limit of deflection for aerodynamic control surfaces (tail control) and altitude for surface to air missiles?

Also how can the fin deflection range (Max/Min) be determined for any altitude?

Please mention any reference text related to the subject.


texts: What's the difference between a "runaway prop" and a "feathered prop"?

texts: My father was a P-51 fighter pilot in WWII. Another P-51 flown by a buddy of his suffered a "runaway prop", and as a result of that, the plane could not maintain its normal high speed, and in the end, the engine overheated and the plane exploded over the English Channel.  Luckily, the pilot, Major Foy of the 357th FG, had noted excessively high engine temperatures, and bailed out just before it exploded.  What would cause a "runaway prop" of the variable prop to create a loss of thrust and a high engine temperature?


texts: Why do pilots do walkaround inspections for regularly scheduled commercial flights instead of aircraft mechanics?

texts:
If the airline has personnel to maintain the aircraft, wouldn't it be more cost effective to have them inspect the aircraft before flight rather than have the captain or first officer do it?
Is it because whoever will fly the aircraft will probably do a better job of inspecting it because they are putting their own lives at risk?


texts:
If the amount of cargo is not evenly distributed across a network a freighter will sometimes have to fly a route not loaded to capacity. Do cargo freighters ever have to be ferried empty to alleviate this "back-haul problem"? The link uses the example of trucking, but my question is to what extent this issue manifests itself in scheduled air cargo (e.g. FedEx, UPS, etc.).

(Note: My assumption is that this affects scheduled air cargo operators more severely than specialty cargo operators doing "one-off" hauling of special goods)


texts:
Does a 4 bladed prop have almost twice the thrust of a 2 bladed prop?

As a general rule, I'm told GA planes generate 4 lbs of thrust per horsepower. (Source: Zenith School of Airplane Design, Flying on your own Wings)

So if you use a 4 bladed prop, does it generate anything close to 8 lbs of thrust per hp?  In other words, say for an ultralight, where you're only flying 60 mph, and prop drag isn't an issue, can you use an engine with half the horsepower, or some other fraction thereof?

Will that shorten my takeoff roll? Conceptually, takeoff roll is just the distance to accelerate from zero to my minimum takeoff speed.

Since F=ma, then a=F/m, so if I want to accelerate twice as fast, I need twice the force, or thrust ( probably more than twice the thrust, to overcome rolling drag, etc.)

Is this correct, at least conceptually?

Just to summarize:

In the GA world, I'm told as a general rule, props develop 4 lbs of thrust per hp. So, for 160 hp, I get 640 lbs of thrust, or is this not correct?

In the STOL world, with 8' props, I'm told, they get 8 lbs of thrust per hp. So, for 160 hp, I get 1,280 lbs of thrust.

Well, I'd rather have a 160 HP engine and prop that produces 1,280 lbs of thrust than 640lbs of thrust.

So... if I take my 8 ft 2 bladed prop, chop it in half to get a 4' 4 bladed prop ( same overall "wing area"), I'll still get 1,280 lbs of thrust ( less a few % for inefficiency), instead of 640 lbs of thrust. Is this correct? If not, what value of thrust should I expect, roughly?

Or are these rough estimates incorrect?


texts: What could explain the fact that during 1976-80, I used to hear commercial jets make sonic booms while flying overhead?

texts: I've read on this site & on Wikipedia that there have only been a couple of commercial jet planes in history that have broken the sound barrier--either in testing (without passengers) or during an unexpected descent.  However, during the period of 1976-80/81, when I lived fairly close to an international airport, I used to regularly hear commercial jets (I assume 747's) create sonic booms as they passed fairly low overhead. I now live even closer to a much bigger international airport, & never hear this. That's why I started to wonder why. & now that I've read that on record, it's only happened a couple of times, I'm even more curious of what the explanation could be. (It was Bradley Airport in CT, if that matters).


texts: Why is this plane flying a circular track?

texts:
Came across this on flighradar24 recently. It shows a jet making a very strange pattern. I would normally expect it to be some sort of aerial survey but seems unlikely in such a large aircraft at such a high altitude (I would expect to see a GA plane do this at lower altitudes).

Snapshot:

Closeup of snapshot:

Flight details (still might be able to find flight if you hurry and check out the latitude and longitude):


texts: Does every Safety–of–Flight Test (SOFT) include full testing of each and every equipment?

texts: Does every Safety–of–Flight Test (SOFT) include full testing of each and every equipment with the full EMC or is it just a basic quality test for some of the affected systems?


texts:
I have a control column head similar to that used on the Spitfire and Hurricane but with two levers for cables coming up from the stick. I would like to find out what aircraft used this type.
Markings on the side  are 444/35,  AK-2 and AK-8 in an oval and A1D 4 in a partially stamped circle.


texts: What is a "Land And Hold Short Of" light?

texts:
A runway inspection found a "Land And Hold Short Of" (LAHSO) embedded light had become dislodged and had caused damage to a tyre.

http://avherald.com/h?article=4bb1964c&opt=0

What is such a light, and what does it look like?

See also How are runway lights constructed?


texts: What does "Controlling Object" mean in FAA documentation?

texts:
I was examining FAA's legacy files, which contain information for various airspace elements, and I noticed that there is a field in the airport layout file called "Controlling Object", for both base and reciprocal ends of the runway.

Some of its properties:

Controlling object description
Controlling object marked/lighted
FAA CFR Part 77 runway category
Controlling obstacle clearance slope
Controlling object height above runway
Controlling object distance from runway end
Controlling object centerline offset.

It seems that it's an obstacle near the airport, but I can not tell why it is more important than the others. Does it lead to the most adverse situation, as far as aircraft's climb gradient is concerned? Does also the term "Controlling Obstacle" exist?

Could someone point me in the right direction?


texts: Why does increasing a glider's weight using water ballast improve its speed and performance?

texts:
I was studying gliders and how they fly.  There is a point that's not clear to me: why does using water ballast improve the performance/speed of a glider?  If I understand correctly, my glider jumps from one thermal to another more quickly with ballast than without.

How can more weight improve speed?

Thanks
Ale


texts: Wing moment - providing stability or not

texts: It is said that wing alone is unstable, because it provides a nose up moment, so tailplane is needed to damp it. But normally wing provides a pitch down moment (as far as I know, apart from very high aoa situation) because centre of pressure is behind the centre of gravity. So shouldn’t wing moment be actually stabilising? I’m confused about stability, because we one time we consider stationar lift acting in aerodynamic centre and moving centre of gravity, next time moving centre of pressure with stationary centre of gravity and so on... please help me out.


texts: Is it possible to build a flight-capable aircraft powered by compressed gas?

texts:
I pray this isn't a physics SE question.

A star engine can be considered "gas operated". So what if we power a star engine with unleashed, formerly compressed gas instead of... actual gas/aero-kerosene/etc...? So instead of fuel tank (oh the temptation to pun is so strong here) you use gas tank?

Note that since nothing has to BURN, we can use lighter-than-metal material, as engines usually play a big part when it comes to weight of aircraft.

Can you?

And if that's a YES, can you estimate the flight time?


texts: Why do supersonic planes fly higher than subsonic airliners?

texts: I saw on wiki that a boeing 737 flys at about 38,000ft and a Concorde flys at 60,000ft. What made it possible, and advantageous, for Concorde to fly so much higher?


texts: Which "Power Available" graph is more correct?

texts:
Trying to understand the drag and power required/available graphs for a piston + propeller airplane. Both graphs are from current book/website and while they are showing mostly the same thing, I noticed the shape of the power available curves are different.
If I have to guess I think the second graph make more sense, since power available from a piston engine should be almost the same throughout the entire speed range.
*If the above is true, can you please also explain why it's not a perfect horizontal line across? Ie: if the engine is rated for 150 BHP, then the line should be at 150 BHP, other things equal (density altitude)
I feel like I'm missing something fundamental here but can't seem to work this out.
Thanks


texts: Do all single-engined aircraft experience torque that cause a turning tendency during the takeoff roll?

texts:
I've been flying the Cirrus Vision SF-50 for quite some time on my X-plane 11.

Having a single turbofan engine mounted near the V-tail, I expected the requirement of at least a little right rudder. However, it seems to be perfectly aligned throughout the roll.

Why is a turbofan any different from a propeller aircraft in this regard?


texts: Is it required to be an ATP and work for an airline to be a Captain?

texts: I'm just curious if the ATP certificate and working for an airline are prerequisites to being a Captain, or could you have such a title as a PPL or a CPL?


texts:
How are pilots paired in the duty roster?

Pilots choose their co-pilots from a pool (whitelist)? (Pilot has the final say)
Randomly, but taking pilot wishes into consideration? (Airline has the final say)
Ramdomly, without taking anyone's wishes into consideration?

In the case of (2) or (3), can a pilot refuse to fly with certain other pilots (blacklist), thereby having the power to overrule the airline?


texts: Under VFR, can a pilot fly above a layer of clouds?

texts:
Image source

I often see charts like the one above showing VFR cloud clearance minima. Since the regs list a minimum distance above clouds obviously VFR flights are allowed to fly over clouds. However, it's not clear what kind of clouds one can fly over: only individual smaller clouds, a broken layer or a solid layer. In the US does a pilot under VFR have to maintain a visual reference to the surface?


texts: Why can't the 737 MAX's horizontal stabilizer autotrim be cut out by control yoke inputs?

texts:
According to this article, a horizontal stabilizer runaway on the 737 MAX, unlike with all other 737s, cannot be countered with yoke inputs:

Older 737s had another way of addressing certain problems with the stabilizers: Pulling back on the yoke, or control column, one of which sits immediately in front of both the captain and the first officer, would cut off electronic control of the stabilizers, allowing the pilots to control them manually.
That feature was disabled on the Max when M.C.A.S. was activated — another change that pilots were unlikely to have been aware of. After the crash, Boeing told airlines that when M.C.A.S. is activated, as it appeared to have been on the Lion Air flight, pulling back on the control column will not stop so-called stabilizer runaway.

Why would the addition of MCAS require removing the yoke trim override mechanism?  In the event of a trim runaway, the pilots' first reaction is going to be to pull (or push, depending on the direction of the runaway) the yoke, and requiring them to perform a separate, different action in the heat of the moment to disable the autotrim mechanism is an unrealistic expectation; allowing yoke inputs to cut out the autotrim relieves the pilots of the burden of having to recognise the problem as a trim runaway in order to solve it, and allows the problem to be solved in the same manner as other unwanted pitch excursions (by pushing and/or pulling on the yoke(s)).


texts: Did some early jet engines catch on fire at higher power settings?

texts: Recently I've being playing some IL-2 1946, and in this flight simulator jet engines had a strange problem where if I suddenly throttle up more than 60% the engines would catch on fire. Is this a real thing? The engines that this happens on are the Jumo 004 and the BMW 003 on the Me 262 and the He 162.


texts: When do the LNAV and VNAV NPS pointers appear in the PFD of a B737NG?

texts:
I am pretty sure the LNAV NPS pointer should appear from after takeoff, if LNAV is armed.
But I am not sure about the VNAV NPS pointer. A VNAV climb is based on Speed, not Path, so I assume there is no NPS Pointer visible during a VNAV Climb.
When will it first come on? Once cruise altitude is reached? What happens if one has to level-off before reaching his CRZ FL? Will the NPS pointer appear at that time?


texts: What happened with the balloons of project Excelsior?

texts:
After the flight to the ISS yesterday I am reading more stuff about mankind in the universe.

Reading about the Excelsior project makes me wonder what happened with the helium balloon after Joseph Kittinger jumped. I haven't found an answer to that, does anyone now?


texts: Have crash investigators ever used pilot cameras to help find the cause of a GA crash?

texts: With video cameras being completely ubiquitous and GoPro cameras able to be mounted pretty much anywhere, lots of GA pilots now like to make videos of their own flights. A passenger's cell phone video was used as supporting evidence in the Germanwings crash. Have there been any situations so far where a GA crash has been puzzling to investigators until they watch the video from the pilot's camera which shows the cause clearly? Are they even allowed to do this (anywhere, but NTSB in particular) or are there privacy regulations which prevent them from doing so?


texts: Can I stop crop dusters repeatedly flying over my home?

texts:
I have a crop-duster spraying the fields around me often. He flies over my house no matter what field he is spraying every few minutes. I think he uses my house as a pivot point. The old pilot rarely flew over my place.

My livestock goes nuts. It is annoying. He has to fly low and is loud. I called the company  awhile back and they said he was new and he would talk to him. He is back today flying over repeatedly and I called the company and the owner told me he would call me back. No call back and it goes to voice mail now when I call him.

Is there anything I can do? I told the owner that I understood they may have to fly over once in awhile but this is over the top.


texts: What is this device they bring on board from the jet bridge when we park?

texts: Every time I deplane a Virgin America A320, I notice that they grab something from the jet bridge, and stuff it between the jump seats. I haven't seen any other commercial airlines with things like this.


texts: Can I do the EASA part 66 theory exams before starting practical training?

texts: Is it possible to do the EASA Part 66 B1.1 exam modules first and do the practical training afterwards? Also, is it possible do the exams and training in different European countries?


texts: What airfoil design is needed for a 4 m wingspan soaring plane?

texts: I’d like to build one that is heavier than a F3J plane and it will be similar to NASA’s soaring plane of the "Autonomous Soaring Plane" project. What kind of airfoil do I need? Simply scaling a normal airfoil would have bad results.


texts: Who operates the hoist in a Coast Guard helicopter SAR team?

texts:
Could you tell me who operates the hoist in the Coast Guard helicopter SAR teams?

Is it the A&P technician(Flight mechanic) or the Rescue swimmer(winchman)?

I'm interested to procedures from around the world, in particular inthe US, UK and Canada, but not limited to them.


texts: Why is a combustor in a gas turbine engine asymmetric?

texts:
As the above question stated, the upper and lower section of the combustor isn't same. Is there any reason behind it? Due to which the cooling of the combustor is also different in the upper and lower section of the combustor.
The below picture clearly depicts it:


texts: Could one see stars from the Concorde in daytime?

texts: The Concorde flew to an altitude of 60,000 ft (18.3 km) where stars should be visible at noon, aren't they? This question asks on how high stars become visible, and it is said Blackbird pilots could see them at 80,000 ft. The Concorde flew at the Armstrong line when highest, above more than 90% of the atmosphere's mass. Are there reports of passengers and pilots on the Concorde seeing stars (other than the Sun) when at peak altitude? Also, did the Sun appear whiter due to the thinner atmosphere?


texts: Is it possible for crew oxygen to exacerbate a flight deck fire?

texts:
Crew oxygen is, as I understand it, a very high percentage of purity.

Oxygen-enriched air acts as an accelerant to a fire, causing things to ignite which wouldn't in ordinary air, and making fire more difficult to put out. Nice illustration of what oxygen-enriched atmospheres can do to shirts: here, p. 5. This also says that hair and clothes can trap oxygen, and this can be very dangerous. A spill from a mask might well accumulate in hair and clothes.

Also, although I'm not a chemist, it does appear that the margin between normal air and dangerous oxygen-enriched air is quite a slim one: this document says that at over 23% concentration "mixtures must be handled with all the precautions and care of pure oxygen as they start to change fire chemistry and enhance combustion."

In the event of flight deck depressurisation occurring simultaneously with a fire, and the crew using their bottled oxygen, could the following events pose a serious danger:

leak in one of the tubes involved in supplying the oxygen
crew member taking off their mask (and using a portable oxygen supply
instead)
crew member inadvertently pulling an oxygen tube out of its attachment in the course of some bodily manoeuvre
crew member switching their mask to "emergency mode" i.e. where constant pressure is maintained to prevent inhalation of noxious substances, but also perhaps resulting in leaks of oxygen from the mask? (here)

Not an aviation person so don't know how often emergency mode actually gets used, but if the FD were filling with smoke wouldn't you switch to emergency mode to try not to be breathing it in? But could this exacerbate the fire?

Unless my thinking is flawed in some way, wouldn't that mean that descent to an altitude where you no longer have to use oxygen might be quite an important priority in the event of a FD fire? Or maybe blowing an inert gas like argon into the FD*?

Just a final thought: oxygen-enriched fires also burn at particularly high temperatures (Apollo 1, EgyptAir 667). So the danger of such a fire actually destroying navigational or communication equipment and effectively killing the plane might be greater.

* High-concentration argon poses its own danger but for this specific situation, where the crew are on bottled oxygen, it might be OK until the fire was out.