texts: What about the DC-9's wing makes wingletting it so difficult?

texts:
A common way of making older airliners more efficient without increasing their wingspan is to add winglets, either as a retrofit for existing aircraft or as a new, wingletted derivative of a preexisting non-wingletted model.

One particular older airliner for which this doesn't work, however, is the DC-9; winglets for the DC-9 have been studied, but never made it into production.  One of the main reasons for this (alongside the relative smallness of the benefit that could be gained by wingletting a DC-9, compared to that gained by wingletting other types of airliner, and the increasing smallness of the world's DC-9-classic1 fleet) is that the DC-9's wing structure makes it unusually difficult to safely and successfully winglet:

  APB has investigated a retrofit design for the DC-9 family. Those design studies have not been successful in creating a viable business case. Projected block fuel burn reductions of less than 2 percent are offset by substantial modification costs. The limited potential for the DC-9 is a result of the existing wing structure, which hinders installation of a large winglet, as was possible on the Boeing 737 family. Since the DC-9 has been out of production since the early 1980s, the fleet size has shrunk and the fleet has aged, making the business case for a retrofit winglet or wingtip not as attractive as that for the Boeing 737 and 757 families.  [Emphasis added.]

What is it about the DC-9's wing that makes it so hard to winglet, compared to (say) a 737?

1: The DC-9-10 through DC-9-50, but not the DC-9-80 or DC-9-90.


texts: What is Waterline and why is it called so?

texts: What is waterline and why is it called so?  Is it same as fuselage reference line?


texts: What does this symbol on this Aerodrome Chart mean?

texts: Does anyone know what this symbol on aerodrome charts is?


texts: My windsock is erect, what does this mean?

texts:
I know that airport windsocks are calibrated to reach full erection at a particular wind velocity. At half that speed, the first half of the windsock should be erect and the second half should droop sorrowfully. At one third the speed it will be one third, and so on.

Trouble is that not all windsocks are calibrated the same way. How do I find out what wind velocity will bring my airport windsock to a fully erect state?


texts: Is there any rule in commercial aviation, that two pilots in a plane cannot be a married couple?

texts: Is there any rule followed or imposed by commercial airlines that the pilots of a particular plane may not be a married couple? My thinking comes from common workplace rules, where generally HR does not allow a couple to work in the same department, for obvious hierarchical issues.


texts:
I have a question regarding the production mechanism of induced drag.

I understand the downwash aft of the trailing edge (steaming from wingtip vortices) causes the induced drag by changing the relative flow (blue line) into the effective relative airflow (red line), and thus by bending the lift vector rearward (L to Leff).

My question here is: How does the downwash, that has already passed behind the trailing edge of the airfoil, influence the airflow upstream, causing the entire relative airflow to bend upward as in the picture.

Or is it just an imaginary concept to explain the induced drag?


texts: Why are the Boeing 737 nacelles odd shaped?

texts:
Why is a Boeing  737 NG engine not completely round in shape? It seems to be flat at the bottom and round at the top and sides. Earlier Boeing 737 versions (100 and 200) seem to have a more rounded shape.

(Source)


texts: Was the 1992 Gimli DHC-4 Caribou accident ever investigated?

texts:
On August 27, 1992, 3 people were killed when a de Havilland Canada DHC-4 Caribou crashed immediately after takeoff at Gimli Industrial Park Airport.

Wikipedia describes the accident as follows:

  Three people were killed on August 27, 1992 when a NewCal Aviation turbine-modified de Havilland Canada DHC-4 Caribou they were aboard crashed on the airfield during climb-out after a short take-off from the airport. The aircraft nosed sharply up, arced right and nosed into the ground. […] The cause was listed as failure to deactivate the plane's gust-lock control in the cockpit, […] [T]he Transportation Safety Board of Canada has no record of this incident.

The entire flight was captured on a video which has circulated on the Internet.

Was this accident ever officially investigated? If not, why not?


texts: When is an aircraft required to be pressurized?

texts: For example a Cessna Grand Caravan doesn't have a pressurization system, but a Phenom 100  is pressurized, so what are the main reasons a manufacturer has to build an aircraft with a pressurization system: altitude, speed, etc?


texts: If the push was accidentally started with the brakes on, what will happen since these towbars don't have shearpins?

texts: The push was started accidentally before the brakes was released. What will happen since it doesnt have shearpins?


texts: Below what altitudes do shock waves form?

texts: For a shock wave to form, the air must have a certain density. Surely in Thermosphere or even upper parts of Mesospheres the air is very thin. I was wondering if there is a formula related to the Mach Number and the probability of shock wave.


texts: Does a constant power prop exist? What are the tradeoffs compared to a constant speed prop?

texts:
Variable-pitch props allow pilots to adjust the angle of attack of the propeller to change the load on the engine.
The most common implementation of this is a constant speed prop where the prop governor adjusts pitch to maintain the chosen RPM.
From a pilot's perspective, we only really care about two things:

Power output
Fuel economy

Using a constant speed prop, you can't directly set the output power - you set the throttle and prop speed and observe the power output.
Using a constant speed prop, you also can't directly set the fuel flow rate - you set the throttle and prop speed and observe the fuel flow (or look up the POH).
Using a constant power control law instead the pilot could set the desired power and have the prop pitch adjusted automatically to maintain that (or if impossible, fail in a similar way to a constant speed prop going off the governor).
It is also possible to pick the most fuel efficient RPM for a given engine load which means that the two inputs (throttle + prop speed) get reduced to one: desired power.
The benefits I see are:

Reduced workload
Increased efficiency

The drawbacks I see are:

Inability to operate the engine at anything other than best efficiency for a given power - but I don't actually know what use case that would be useful in.
System complexity
Certification cost

Has a constant power control system ever been used in aviation? Are there other drawbacks that I'm missing?


texts:
There are accidents where the pilots couldn't see the instruments and literally flew the aircraft blindly due to the excessive smoke in the cockpit, ranging from UPS Flight 6 to other accidents.

How come no company has made an airtight cockpit to prevent smoke from entering the cockpit? Even though it can be said it is complex I think it doesn't make an multimillion airliner a lot more expensive?


texts: Do pilots adjust the throttle setting during a Red Bull air race?

texts: During a race do the pilots adjust their throttle settings to control speed, or do they leave the throttle wide open the entire time?


texts: Does shrouding a propeller minimize induced drag by equalizing the downwash velocity along its blades?

texts:
EDIT: It's not a duplicate of Are ducted fans more efficient? That question and the answers doesn't address the reason for the higher theoretical efficiency, it is more about efficiency in practice (drag on the duct, weight, etc) and hence why they aren't used despite the higher theoretical efficiency

I was told shrouded propellers are more efficient becuase tip vorticies are eliminated by the wall which would imply no induced drag but apparently that is wrong Do ducted fans eliminate induced drag? therefore I've been trying to figure out why they are still more efficient than an open propeller despite still having induced drag. It must have less induced drag.

The vortex around an unshrouded propeller:

At first I thought the wall somehow increases the effective wingspan, moving the vorticies to the top of the wall much like winglets do and thus reducing the induced drag that way

However unlike winglets the walls don't have a pressure difference on either side (it's not an airfoil) therefore the vortex can't be there.

So the vortex must be around the whole wall because above the wall the pressure is low and below it the pressure is high.

But this doesn't change the effective wingspan so why does it have less induced drag?

My explanation is that the existence of the wall causes the inside of the vortex to "straighten out" with the flow through the duct which makes the downwash velocity constant along the length of the blades (since the flow is irrotational). This means that this condition is satisfied:

from page 7 of http://naca.central.cranfield.ac.uk/reports/1923/naca-report-121.pdf

Therefore induced drag is minimized. Is this correct?


texts: Is any readback required when ATC uses the phrase "RADAR CONTACT"?

texts:
As the title says, is a readback required? I've heard some people say that it's not required, while some others say we should readback our call sign only. Some even say just push the transmission knob twice to inform the controller that we are acknowledging.

Which one is the correct action and what are the references or publications?


texts: In a Boeing 767, what percentage of the aluminum is in structural components?

texts: For a Boeing 767 (model year 2000), does anyone know how much aluminum is in 'structural' components, as a percentage of the total amount? And specifically the wings?


texts: What is the correct range of the 787-10?

texts:
There are two conflicting values for the 787-10's range; they are:

6,345 NM (11,750 km) -- boeing.com

7,000 NM (12,975 km) -- on the same website few years ago, as well as flightglobal.com

Note: In its early development the value was 6,345 NM (11,750 km), same as #1.
Which is correct and why do the values keep changing?


texts: What is the correct phraseology for declaring a fuel emergency?

texts:
If I am  pilot, approaching my destination airport and realise that, after landing I will have less than 30 minutes of fuel remaining, how exactly should I express this when communicating with ATC?

in ICAO rules
in FAA rules
in EASA rules

For example, in a country where Spanish is an approved ATC language, would it be sufficient to say "ABC12345 FL210 en acercamiento y solicitamos prioridad para la aproximación. Al momento se nos ha presentado un problema de combustible" ("ABC12345 FL210 inbound and we request priority for the approach. Right now we have a fuel problem")


texts: What is the correct phraseology to request a climb?

texts:
If you'd like to request a climb to a higher flight level while cruising, which do you think is a more proper way to request it:

Request to climb FL350
Request climb FL350

I know they have zero difference in meaning between them, but I'm curious which one might sound more natural or professional in the EPTA test.


texts: Which compressed air and fluid are generally used by oleos?

texts: Which compressed air and fluid are generally being used by oleo-struts?


texts: Are military jets always scrambled when communication to a commercial aircraft is lost?

texts:
I've heard that in case a commercial flight does not respond to Air Traffic Control, military jets would always be scrambled to check the state of the flight.

The benefits of scrambling jets are clear. My question is, are they always scrambled in every case?


texts: Has there ever been a successful 'bail-out' during an airliner test flight?

texts:
Has there ever been an instance of a crew having to 'bail out' during a test flight of a commercial style aircraft (I.e Airbus, Boeing etc)?

I know that test flight crews often wear orange suits, parachutes during preliminary flight in case there is an issue.


texts: How do people suffering from hypoxia not realize they aren't getting enough oxygen?

texts:
I've seen reports of flight passengers/crew suffering hypoxia, and many times without knowing it.

My question is, how could you not be aware of it? For example, at above 10000ft, if your body is suffering from a lack of oxygen, doesn't it make you breathe faster and harder? (which in turn, makes you aware that something is wrong in the air you're breathing)

Second question: if you're dealing with air containing half as much oxygen, is it not enough (sustainable) to inhale (faster) twice as much air when breathing (without oxygen mask of course) ?


texts: is it possible that setting a lower airspeed makes a steeper climb?

texts:
I'm now studying a Flight Management System (FMS), and it says that when the FMC predicts that the airplane will not reach an ALT constraint, the CDU will display "UNABLE NEXT ALT" and then we have to manually set a lower airspeed to provide a steeper climb.
But, I've learned that when we pitch up, the aircraft slows down because of more drag.
I also remember that when an aircraft increases speed, pitch goes up because of the increase in thrust and more lift from the wings.
So why is a decrease in speed needed to make the FMC altitude constraint, rather than an increase?


texts: What types of gear/supplies are "must-haves" for private pilots?

texts: Is there certain gear that people consider "must-haves" for a private pilot? Specifically, a new pilot or student pilot.


texts: Are these logged time assumptions correct for commercial checkride applicants?

texts:
If an applicant is an ASEL private pilot without an instrument rating, are these assumptions correct?

Multi-engine dual time can be used to satisfy the 10 hours complex time requirement
Cross-country time flown as a solo student pilot can be used to satisfy some of the 50 hours total cross-country required, including the long (300 mile) cross-country flight
Cross-country time flown as multi-engine instruction cannot be used as cross-country PIC because the pilot was not rated in category and class


texts: Some aircraft takeoff from aircraft carriers using a ski jump.  What does it feel like to takeoff this way?  Does it feel like an alpine ski jump?  How does the feeling compare to catapult takeoff?


texts: What range or variation should we expect from gyroscope in a helicopter?

texts:
I need to measure the angular variation of a helicopter. Hence, I am looking for a 3-axis gyroscope? However, what kind of specification the gyroscope should have, like sample rate etc? Therefore, I want to know how the angular velocity changes (in any axis) in helicopter. I need to know the range only.

Any reference would be highly appreciated.


texts: How the maximum service interval is related to UAVs?

texts:
I´ve been reading about the aircraft´s maximum service interval but this concepts is hardly related to the day to day aircraft (civil and military ones of course). How does this concept is related to UAVs?

Note: I´ve restructured the question, I´m sorry for the previous one


texts: Is a biennial flight review valid for any airplane category?

texts: If I do a biennial flight review (BFR) in a glider, does it also satisfy my BFR requirement for powered flight (ASEL)?


texts: Are modern aircraft (fully loaded and fueled) able to operate from hot and high airports?

texts:
Some decades ago, aircraft had really difficulties to take off and land at high altitude airports in hot weather.

I'm not sure whether advanced FADEC and better mastering of aerodynamics might today allow a heavily loaded and fully fueled FedEx MD11 to take off from 5000+ feet elevation airport in hot weather.

I'm curious to know about how much progress there was over the last 20 years or so.


texts: What is wrong with a high-speed landing for an ultralight or GA aircraft?

texts: Is it okay to land an ultralight or a general aviation plane at a speed higher than the recommended landing speed for such plane? Will there be any damage if the descent rate is very low?


texts: How does the performance of an aircrafts propeller change with respect to distance from obstructions?

texts:
I am interested to know if there are any changes in propeller performance (thrust, efficiency) with respect to distance from obstructions such as the fuselage or wings?

I am particularly looking for studies or experiments. Mostly interested in tractor/puller configurations but info for pushers would be nice to know too.


texts: Why didn't Boeing produce its own regional jet?

texts:
Boeing, although it produced many larger narrowbodies, never designed its own regional jet; the only regional jet it ever produced was the DC-9 (from 1997 through 2006, in the DC-9-80 and DC-9-90 series), a (McDonnell) Douglas aircraft which Boeing inherited from Long Beach through a corporate merger.

Why didn't Boeing design and build its own regional jet earlier, to compete with the DC-9?


texts: What is the lifespan of a level D simulator?

texts:
We have a few interesting questions about the normal ways aircraft end their lives.  What about simulators?  How long do they typically last?  What is the typical reason for retirement?
I am particularly asking about high level simulators used for airliner type ratings.
This question was inspired by discussion of the time taken to reboot a simulator:
Do Flight Simulation Instructors stop the simulator before a simulated crash?
Related questions:

Why are some aircraft's life limited by both cycles and flight hours?
Under what conditions do airliners retire aircraft and sell them to other airlines?
What limits the lifespan of helicopters?
What is the lifespan of commercial airframes (in general)?


texts:
From YouTube.

I always thought SAT (Static Air Temperature) and OAT (Outside Air Temperature) were the same thing. So does this answer, so does Wikipedia:

  [The] outside air temperature (OAT) or static air temperature (SAT) refers to the temperature of the air around an aircraft.

So, what is the difference based on that video capture?


texts:
Nowadays they are no longer needed but why do they cover them up like in this photo?

What is their purpose and why aren't they used anymore?

Source


texts: Why is the cockpit color of eastern aircrafts different than western's?

texts:
Commonly, the cockpit of eastern aircraft have a MediumSpringGreen or PaleTurquoise color while the cockpit of western aircraft have a Black or Gray or SaddleBrown color. Is it kinda standard? e.g.
Tupolev Tu-142M3

Ilyushin IL-86

Boeing 747-84AF

Beechcraft B200GT Super King


texts: How can I get flying again after FAA medical rejection for anxiety two years ago?

texts:
Post Military Service I was diagnosed with Generalized Anxiety Disorder and put on Zoloft (Sertraline). I had taken it for a while but had not refilled my prescription, and was off the meds with the approval of my doctor. During my FAA medical exam (3rd Class) they checked my insurance and saw that I had been prescribed the meds. I had not put it down as I misread the prompt as currently taking or being treated for those conditions.

I'm totally fine now, currently an EMT, been off the meds for 3 years now, and hoping to start flying again.

My hopes are low, but is there any hope for me getting flying again?


texts: Can a controller be tasked to provide more than one ATC service at a time?

texts:
During a visit to one of the ATC Facility  I found out that the Aerodrome Controller was also providing procedural approach control service along with aerodrome control service.

Similarly, Area Radar Controller of the same facility was also permitted to assume the responsibility of Procedural (Non Radar) controller (who acts as a backup to the Radar Controller) in the absence of Non Radar controller to provide relief to him.

I find both of these arrangements a violation of safety. I tried to find some reference to support my idea about this in the ICAO DOC 9426 (ATS Planing Manual) and Human factors Training in ATM, but could not find out anything that specifically prevents or allows this particular arrangement.

Can these services be combined? Any reference to the ICAO doc or some regulation would be a great help.


texts: Why would a commercal flight circle while enroute?

texts:
While selecting random flights to learn about FlightRadar24, I came across AC7311 flying from Toronto, ON (CYYZ) to Indianapolis, IN (KIND), and saw that it flew a couple of circles southwest of Lima, OH (near KAOH).

What are some of the reasons Air Traffic Control would direct the pilots to do that?


texts: Is flight training on Russian planes performed in Russian?

texts: When doing flight training in a Russian plane (e.g. Tupolev, Antonov, etc.), does the flight instructor speak Russian or English?


texts: Does having lead-in lights in sight allow descent below MDA?

texts:
Does having lead-in lights in-site during an approach that includes them allow for a pilot to descend to 100 feet above the touchdown zone elevation? 14 CFR 91.175 allows a pilot to make such a descent if the approach light system is in-site, but does a lead-in light system qualify?

The approach also states the following:

  When visual reference established, fly visual to airport via lead-in lights to Rwy 13L or 13R.

Also worth referencing here is this question about what counts as runway in sight, but this question is specific to lead-in lights and is not answered directly by that question.


texts: What is the exact definition of Taxi Time?

texts:
I found some definitions on the web, but they weren't same.

Some resources mentioned it is sum of the times the aircraft is moving on the ground with its own engines. Some defined it as the time between chocks-on and take-off.


texts: How is an Airbus A380 fuselage joined and fastened together?

texts:
An Airbus A380 fuselage is manufactured in three different parts and then assembled together:

(Images courtesy of Airbus S.A.S 1994)

The fuselage functions under extreme conditions: low pressure outside and normal pressure on the inside (normal for humans, that is), and wind drag at near Mach 1 speeds.

How are the three parts joined together to complete an airtight unit? Does one fit into the other in a male-female configuration and how are they held together? Is it nuts and bolts, rivets, screws, airtight glue or a combination of them all?  Pictures would be greatly appreciated.


texts: What is the maximum Mach number for a titanium aircraft?

texts: What is the maximum achievable Mach number for a titanium aircraft assuming speed is limited by structural heating?  The answer would be even better if there is a list of different materials and maximum Mach numbers.


texts: Are the VFR weather minimums in 91.155(d) redundant because of 91.155(a)?

texts:
14 CFR 91.155(d) specifies that:

  ... no person may take off or land an aircraft, or enter the traffic pattern of an airport, under VFR, within the lateral boundaries of the surface areas of Class B, Class C, Class D, or Class E airspace designated for an airport ... unless ground visibility at that airport is at least 3 statute miles ...

But we already know from the table in 91.155 (a) that for Class B, C, D, and E, the minimum flight visibility is 3 sm. So it's not possible for this rule (d) to apply without already triggering the rule (a).

My question is then what's the point of this additional rule? Am I misinterpreting the text?


texts: I have a European SPL EASA license - can I fly a Cessna 172 in the US?

texts:
I have a European EASA SPL licence with 200 flight hours logged and would like to fly in the US. I understand that a few hours flight training with a US instructor due to differences of rules makes perfectly sense. I also understand that I need a TSA approval.
My question is, will I be able to get a Foreign Private Pilot License issued and fly a Cessna 172?


texts: Why might this trans-pacific flight not follow a more direct route?

texts:
I notice that this flight from DFW to PVG has a path that’s not a single arc of a great circle. Rather, it looks like it flies to some city in California and then takes a direct route for the remainder.

Why might it do that, instead of following a more direct route, such as a great circle route?  It didn’t stop along the way, so why would it need to overfly an intermediate location that’s not on the direct route?

(flightaware.com) American Airlines 127 Thursday 04-May-2017

Compared to great circle route:

(gcmap.com)


texts:
Russia has the proven capability to build large jet airliners.

Ilyushin Il-96
Tupolev Tu-204

But, if we take a look at the major airlines in Russia, they don't appear to have Russian airliners:

Aeroflot
Rossiya
Red Wings

Why aren't Russian jet airliners popular even in Russia?

If there is any reason like X, Y, or Z,  what is Russian government doing to make its home-grown airliners popular?


texts: What can disqualify an airport to be used as an alternate?

texts: As a military pilot, our regulations listed things that disqualified airports as being alternates.  I have not been able to find a reference to these same items listed in the 14 CFR Part 91.  Does anyone know where to find the regulatory references for the list of things that disqualify an airport as an alternate for an IFR plan?  For example, an airport cannot be used as an alternate if the instrument approach at the airport you plan to use is listed as "Radar Required."  Is that a consideration in General Aviation?  Likewise, I was trained that if a navaid is unmonitored or if the airfield only has GPS approaches, again disqualifies the airfield as an alternate.  However, I don't know where that is written in the FARs.  Does anyone know where I should look?


texts: Why do some turboprop engines require motoring after shut down?

texts: A retired pilot I know told me about his time flying a Cessna 441 Conquest II. He said that after shut down he'd have to go out and motor the props. What engines require this procedure and what is the purpose?


texts: When does root bending moment start to become important?

texts:
I guess for small aircrafts ,hangliders etc root bending moment is not important at all,because it is relativly easy to achieve sufficient strength ,so their ideal solution will be eliptic..?
Does that mean,small aircrafts dont have any benefits of using bell distribution?
I am also interested what is  root bending moment/wing weight ratio between small aircrafts and big ones,airliners etc?


texts: Can all helicopters hover, and how long does it take to "stop"?

texts:
Following the accident of Kobe Bryant's helicopter N72EX, there are a few things that puzzle me:

While waiting for clearance to fly close to Burbank airport, the helicopter didn't "stay in place", but actually made all sorts of loops and circles over Glendale:

Source: Flightradar

Does this mean that such an helicopter can't actually "hover", and has to move forward to stay up in the air? There are definitely helicopters which seem to be able to stay in the same location (TV helicopters, police helicopters), so I wonder what is the difference (size? load?). Or is it just "cheaper" to make loops rather than hover?

This question and associated answer seem to indicate that there is actually a limit to the "hovering" capability of helicopters "in the air", though I'm not what the consequences are when you go beyond the limit. Is the helicopter just not able to "stay in the air"? Or does it need to move forward to be able to maintain level flight? How does it actually work, shouldn't "tilting" the helicopter forward reduce the "upwards" force?
At the end of this ill-fated flight, the helicopter makes a left turn until it crashes in the mountain.

Current "expert" analysis (pending NTSB's inquiry) point to an issue with the weather that suddenly got very bad (basically the helicopter being sandwiched between very low ceiling and rising terrain) which made the pilot make a manoeuvre that ended up being a very bad choice.

Could the helicopter not just have "stopped" or at least "slowed down" rather than turn? If it should have been able to stop, how long (in time or distance) would it have taken?


texts: What's the point of using T-38 to instill flight proficiency in Space Shuttle pilots?

texts:
As discussed in this Q&A, NASA pilots had to fly 15 hours a month on T-38 to maintain flight proficiency.

NASA Dryden's T-38 Talon trainer jet in flight over the main base complex at Edwards Air Force Base. Source

As a newbie, this seems rather weird - from all little I know about the Shuttle, its flying characteristics in no way resemble T-38.

So why use T-38? (or any normal jet at all)?


texts:
Does an aircraft use its engines to taxi or is it always pulled by some other vehicle?

I have seen a small lorry pulling it sometimes; is it really pulling the huge thing, or does the aircraft use its own power somehow?


texts: Why would a country prefer to purchase Su-35 rather than Su-30MK?

texts: Given that the Su-35 is merely an upgrade from the Su-27, why is Indonesia purchasing Su-35?


texts: Why does the F-15 have a swept-back trailing edge at its wing tips?

texts:
The F-15's wing has an curious feature: a swept-back trailing edge near the wingtips, along with an unswept inboard portion of the wing.

(Modified from https://en.wikipedia.org/wiki/McDonnell_Douglas_F-15_Eagle)

This feature is not present on comparable teen-series fighters (e.g. the F-16):

(https://en.wikipedia.org/wiki/General_Dynamics_F-16_Fighting_Falcon)

Lots of Soviet-made aircraft (e.g. MiG-25, -29, and Su-27 families) appear to use a swept trailing edge. However, these fighters all have a constant sweep across the wing--not two sections of different sweep like the F-15.

(https://en.wikipedia.org/wiki/Sukhoi_Su-27)

Why then does the F-15 have such a seemingly unique feature (i.e. a trailing edge with two sections of differing sweep)? Clearly its designers must have thought it served some purpose--I presume they would not have added it for mere decoration.

EDIT: to clarify, my question seeks the physical reason(s) for why the trailing edge of the wing tip has a rearward sweep--not why the wings are cropped at an oblique angle, or a citation of historical precedent.

EDIT 2: I'd also like a well-sourced answer, if possible.


texts: Why is mist abbreviated BR on METARs and TAFs?

texts: The abbreviation for a condition of mist is BR on METAR and TAF reports. How did mist end up getting abbreviated as BR?


texts: Why is it runway "1" instead of "01" in America?

texts:
In the case of a runway with a magnetic heading of 10° in America the runway number ("1") isn't hugely distinguishable from the runway centreline IMHO, (for example see Washington Airport and San Francisco Airport).

Is there a reason why the USA doesn't add the leading zero like the EU (example Brussels Airport and RAF Waddington)?

Does the ICAO make any recommendations about this?


texts: Is (or was) it acceptable to throttle up for takeoff before being aligned with the runway center line?

texts:
30 years ago I was on a flight from Spain to Brussels and when we were heading to the runway for takeoff, the commander opened full throttle to the engines while we were still some 60º away from being straight on the center line. At the same time he said loudly over the cabin loudspeakers "¡Nos vamos!" (Let's go!).

Well, a psychiatrist on board said: "A psychopath, a complete psychopath!". And Gerald L Klerman, MD once told me that the FAA was concerned about finding a way to detect a manic pilot before takeoff.

Was the pilot dangerously irresponsible, or was it an acceptable way of handling an airplane?


texts: How do ratings work with pilot certificates?

texts:
Just wondering how ratings work with pilot certificates.

Let's say I get both a private pilot certificate and a commercial pilot certificate for airplane / single-engine land.

If I want to add a rotorcraft / helicopter rating onto my commercial pilot certificate for airplane / single-engine land, do I also need to get training to add a rotorcraft / helicopter rating onto my private pilot certificate for airplane / single-engine land also?


texts: What is a good and simple software for calculating propeller thrust and required power?

texts:
My main requirements:

Calculate propeller thrust with big range of the altitudes (0 - 200 km) or to have air pressure input parameter, which I can type. For example pressure for 152 km is $4.98\times10^{-7} kPa$ as mentioned here.
Calculate required power.
Calculation can be done for static case, like helicopter which is staying on the ground or moving up very slowly like 1 m/s.

I found this one which is good enough for me, but I am not sure if it is doing good calculations for high altitude (50-100km) and I can trust it. Below is the screenshot from it. I would be more confident, if I would be able to type air pressure, but not altitude.

P.S. I do not want to dispute if it make sense or no to use propeller at high altitudes. I just want to know if there is software which can do this calculation. I will do calculation and based on the calculation will decide if it make sense or not. Please do not put comments about propeller inefficiency at high altitude.


texts: In this picture, how do you determine the amount of the camber? Is it the average difference in the distances between the mean camber line and the chord line from the leading edge all the way down to the trailing edge?


texts: How large are the banners that are trailed behind small planes for advertising?

texts:
How large are the banners that are used for aerial advertising, and how much do they normally weigh?

Example:

source: © Raimond Spekking / CC BY-SA 4.0 (via Wikimedia Commons)

Wikipedia page on Aerial Advertising


texts: What is this pattern on the windshield of aircraft?

texts:
The image is extracted from this Airbus A350 video (at 3m40s, when taking off)
I circled in purple the strange pattern formed by few black straight lines. I'm quite puzzled as I have no idea of what it is or what purpose it can serve.
EDIT: I would like to sum up the ideas in comments as there is interesting guess and discussions in the comments. It is a strange device which can be:

a kind of gauge useful as the windscreen seems to be a completely new one and the aircraft presented is one of the test aircraft
part of some windscreen heating device


texts: Can biplane or triplane designs be revived with modern materials?

texts: With the new-age technologies and cutting-edge composite materials etc available currently, is it possible that biplane and triplane designs will make a comeback in the near future?


texts:
Airbus' (A300 / A310) are being used by French companies (i.e. Novespace) that offer zero G flights.

Now the airbus seems to risk a stall at a 40 degree angle of attack (i.e.Air France 447).

In a zero g flight, they climb at 45 degrees and then nose dive at the same angle.

Why does the climb not stall the aircraft?


texts: If you replaced jetfuel with hydrogen could the aircraft engine work on hydrogen?

texts: I know that hydrogen has a reaction with oxygen like with jet fuel, but could the engine run on hydrogen.


texts: Can I use any reference area for lift and drag coefficient?

texts:
I know that for rockets they often use the circular cross-section S_reference for the drag prediction: drag = rho/2 v^2 * c_D * S_reference

For aircrafts they use the chord length of a wing as S_reference.

So when I want to compare those to for their aerodynamic performance, can I just use
S_reference{rocket} * C_D{rocket}

and S_reference{aircraft} * c_D{aircraft}

So to my mind: I can always use any reference area I want for determining c_D , but when I want to compare two bodys for their aerodynamic performance, I have to use: c_D * S_reference

Thanks for your opinion,


texts: Why is alcoholic gasoline such a showstopper for aviation?

texts:
One of the main reasons the common avgas grades are still full of 3-plumba-3,3-diethylpentane is the incompatibility of many aircraft fuel systems with the oxygenates (primarily ethanol, with some ETBE) used as octane boosters in mogas, as mentioned (for instance) here:

  [...]  87UL/E0 (similar fuels are called 82UL or 85UL) -- This is a tightly specified form of motor gasoline (mogas) -- without any ethanol or oxygenates in it, as many aircraft fuel systems aren't compatible with ethanol -- that is used in low-compression aviation piston engines mounted in airframes certified or STCed for operation on motor gasoline.  [...]

Bolding in original; emphatic italics added.

But the automotive industry had the exact same problem, and, yet, adapted easily to the advent of alcoholic unleaded gasoline (namely, by replacing incompatible fuel lines and seals and whatnot with ones not dissolved by ethanol).  So why are oxygenates so much more of a stumbling block for aircraft fuel systems and engines?


texts: Why does the A320’s maximum allowable aileron deflection decrease, rather than increase, when the flaps are extended?

texts:
According to this answer to why the A320 uses mainly spoilerons for roll control during landing, rather than conventional ailerons, the ailerons can’t extend as far when the flaps are extended, for fear of stalling the wing:

Downward aileron travel must be restricted when flaps are deflected. Since flaps change the local incidence on the flapped part of the wing, the outer wing will experience an increase in its local angle of attack. The increased suction over the inner wing will accelerate not only the air flowing over the inner wing, but also that air which will flow over the outer wing as well. Left to itself, the outer wing would stall if powerful Fowler flaps are deployed on the inner wing.
Adding slats will push the stall angle of attack up, and now the outer wing is back in business. However, if the aileron is deflected downwards, the stall angle of attack is reduced again. The outer wing could stall simply due to the aileron deflection!

Which would make sense - after all, if the trailing edge of the wing is already angled more down than usual, then it can’t safely extend as far further down for roll control than it would be able to do otherwise - if not for the fact that the ailerons aren’t located on the portion of the wing with the flaps on it (they’re located near the wingtip, where they’ll be more effective at rolling the aircraft, whereas the flaps are located near the wing roots, where there’s more space to store them and they won’t increase the bending stresses on the wing as much), and, since extending the flaps increases the amount of lift produced by the wings at a given speed and vertical load factor, thereby allowing the aircraft as a whole to fly at a lower angle of attack than it would be able to do with the flaps retracted, the A320’s allowable aileron deflection should increase when the flaps are extended, since the lower attack angle of the unflapped, aileron-containing portion of the wing should allow the ailerons to deflect further without stalling.  Indeed, the A320’s direct competitor, the 737, exhibits precisely this behaviour, where higher flap settings increase the allowable aileron deflection (and, thus, the lateral control authority available) for a given indicated airspeed and vertical load factor1 - so why does the A320 behave in precisely the opposite way?

1: This means, for instance, that the 737’s crossover airspeed, like that of essentially all aircraft, decreases as the flaps are lowered, whereas, if the aforementioned quote were accurate, the A320’s crossover airspeed would increase at higher flap settings!


texts: How has afterburner design changed since its inception?

texts: I came across a NACA summary paper on the past 5 years of afterburner development and started reading cause it seemed interesting. However, a couple of pages in I scrolled back up and realized that it was written in 1956. How much have afterburners changed since then and would the information contained in the article still be relevant?


texts: How do we choose a frequency range of interest for flutter prediction?

texts: I'm trying to perform some flutter and dynamical (gust etc.) calculations with Nastran. It has been told to use a range up to 30 Hz for an aircraft I'm working with, but why the upper limit is so choosen 30 Hz? Why for some aircraft the range is up 60 Hz and for another one even up to 100 Hz? I suppose it depends on matirials used in a particular structure and/or a frequency range of presumed loads. I would be grateful if someone can explain how the frequency range of interest is exactly chosen. Thanks!


texts: What is the reason for these strange radio altimeter calls?

texts:
I ask as a dilettante, so please feel free to correct or emend this.

I transcribe the radio altimeter enunciations for https://www.youtube.com/watch?v=Vr-0LiQA6wo:

  0m 21s: 400

  0m 23s: 400

  0m 36s: 100 above

  0m 41s: 200

  0m 49s: 100

Are the radio altimeter verbalisations part of the Ground Proximity Warning System?
Why was 400 uttered twice? Isn't the A380 descending?
Same question for 100 at 49 s, compared with 36 s?
What does the above imply?


texts: ASTERIX category 240 fields placement in a UDP packet

texts: I searched the placement of ASTERIX Category 240 radar video data fields in a UDP packet. But I cannot find any useful info. Is there a standard for this work?


texts: Where is the airport in Disneyland Paris? (DLP)

texts:
I just found out that there is an airport in Disneyland Paris with the IATA code DLP. Since I've never heard of it, I wanted to see it on Google Maps, but haven't found it.

Is there actually an airport, and where?

Why does Disneyland has its own, with CDG not far away?


texts: Is the rotor described in this Kickstarter new?

texts:
A NewAtlas story linked to a Kickstarter for a the "Whisper Drone" that shows a CAD model of a rotor that the Kickstartee-aspirant has apparently 3D-printed and flown (four of) on a quadcopter.  I find the rotor strongly reminiscent of something I can't place.

Is the rotor design new?  If not, what is it (presumably a variant of)?


texts: A Question about Departure Procedures at KLRU

texts:
The Las Cruces International Airport has the following text in the Takeoff Minimums and ODP document:

  LAS CRUCES, NM

  LAS CRUCES INTL (LRU)
   TAKEOFF MINIMUMS AND (OBSTACLE)
  DEPARTURE PROCEDURES
  AMDT 2 16231 (FAA)
  TAKEOFF MINIMUMS: Rwys 4, 8, 12, 22, 26, 30, 2500-3
  for climb in visual conditions.

  VCOA: All runways, obtain ATC approval for climb in visual
  conditions when requesting IFR clearance. Climb in visual
  conditions to cross Las Cruces Intl southwest bound at or
  above 6500 on CUS VOR/DME R-038 to ZAXOX INT/
  DMN 27 DME. Continue climb in ZAXOX holding pattern
  (hold W, right turns, 094° inbound) to cross ZAXOX at or
  above MEA or assigned altitude for route of flight

What I don't understand is if these procedures are optional or required.  While I understand that part 91 doesn't have to abide by Takeoff minimums and ODPs, would a commercial carrier be expected to do the VCOA?  In IFR training they said VCOAs can be requested but not offered by ATC.  Would a commercial carrier be expected to do the VCOA or could they do a Diverse Departure?  Also do the Takeoff minimums only apply to the VCOA?

Link to document Here


texts: Does an Airbus FAP display any indication of a full waste tank?

texts:
I have doubt about controls on FAP regarding Waste Tank.

I understand when crew person clicks on Input On button, FAP displays the quantity of Water and Waste tank.

But what happens when Waste Tank is Full?

When waste tank is full, Will FAP displays any indication upfront or Flight attendant has to click on Input on Button to know the quantity?


texts: How does an airborne DME unit differentiate itself?

texts:
The FAA's IFR handbook glosses over a keypoint:

  The aircraft DME transmits interrogating radio frequency (RF) pulses, which are received by the DME antenna at the ground facility. The signal triggers ground receiver equipment to respond to the interrogating aircraft. The airborne DME equipment measures the elapsed time between the interrogation signal sent by the aircraft and reception of the reply pulses from the ground station. This time measurement is converted into distance in nautical miles (NM) from the station.

Which is: how does one airborne DME ignore the replies meant to other planes?

Wikipedia says:

  The aircraft interrogates the ground transponder with a series of pulse-pairs (interrogations) and, after a precise time delay (typically 50 microseconds), the ground station replies with an identical sequence of pulse-pairs. [emphasis added]

So is the pulse-pair unique to each unit? Or does the DME unit listen for replies and then picks a different pulse-pair for itself?

ICAO Annex 10 mentions 4 modes:

  Mode W, X, Y, Z. A method of coding the DME transmissions by time spacing pulses of a pulse pair, so that each frequency can be used more than once.

But it is unclear to me how each airborne DME achieves a unique interrogating signal.

Just the basic concept would be great if the radio theory is too complicated.


texts: How do flaps help an aircraft take off at a lower speed, yet cause drag at the same time?

texts: Wouldn’t the drag caused by the flaps just decrease the acceleration, so, although they can lift off at a lower speed, wouldn’t it be faster to just use no flaps and rotate at the higher speed that is required?


texts: Where can I find the information from the back of a TAC if I don't have a physical copy?

texts:
The Atlanta TAC has a note that says "See back of this chart for procedural information within the Atlanta Class B Airspace":

If I don't have a physical copy of the TAC - because I'm using a flight planning app, for example - where else can I find the information?


texts:
We know that many Space Shuttles / Rockets etc. carry their own oxidizer with them. This is partly because at the heights they operate the atmosphere is too rarefied to have enough oxygen to sustain the combustion rates they need.

But also, the liquid oxidizer means small pumps can be used instead of massive compressor stages. Which motivates the following question:

Would it be feasible for a typical passenger jet to carry along its own Oxidizer? I am looking for a back of the envelope feasibility calculation. It intuitively sounds impractical but I'm just curious to see some back of the envelope estimates of how much ( weight / volume) of Liq. O2 tanks would be needed if we hypothetically had something like a B-747  with its own cryogenic Oxygen tanks in addition to already extant massive fuel tanks.

Partially motivated by this related SE Aviation Question and a comment by User @Freeman:

How do rocket engines produce more thrust than aircraft jet engines?


texts: How does wing sweep increase aircraft stability?

texts:
I was told at one point that the sweep of a wing can help with the straight line stability of the craft, in fact I think it's one of the main systems that keeps flying wings flying straight (like the B-2 or N9-M, which comes from the 40s, way before the use of flight computers for stability...).

Why is that?  Are there trade offs between that stability and say, speed?  Is there a such thing as too much sweep?


texts: How does an organization decide to evacuate planes (e.g. in a hurricane)?

texts:
I recently became aware that Embry Riddle temporarily evacuated Florida to escape an oncoming hurricane, taking dozens of planes with it. How does an organization like this decide that planes are at significant risk of damage and shouldn't just be tied down in a storm?  I would think tying down a plane and especially hangaring it would be good against any storm that isn't hurling debris or knocking down buildings.  How bad does the weather have to be to decide to move all the planes?  Do airlines similarly remove all their airplanes from airports in a hurricane's path?

A line of Embry Riddle's plane's parked at Auburn, taken from Auburn's Facebook page.


texts: What are the limits on myopia for a pre-eye refraction surgery for a class 1 medical certificate?

texts: Are there any limitations for myopia (-number) for a pre-eye refraction surgery for a class 1 medical certificate? I live in India & I have -6.5 & -7.5 in the left & right eye respectively.


texts:
I know how the basics of how jet engines work. I know that air goes into the compressor as the first step of the journey. However, where does the air come from that goes into the jet engine at such high speeds it turns the rotors. I don't think its coming from the air because, the plane wouldn't be moving and no air would be flowing at a high rate. Also, once the jet engine is started up, how does air keep coming into the jet engine in flight. From air in the sky?
Is there a difference in the processes for fighter jets and regular commercial planes?


texts: How does a true airspeed indicator work?

texts:
How does a True Airspeed Indicator work?
I am aware of how the air speed indicator works, but how is the density input being provided to this instrument?


texts: How can I know where wind is coming from by looking at water?

texts: For ground reference maneuvers, I know there are many ways that I can know wind direction: smoke, circling, weather reports from nearby airport and so on. However, how can I determine the wind direction by looking at water? I've tried to look for detailed explanations about it but I have found nothing useful. Can somebody help me to understand this issue? I would appreciate if there is any graphic materials.


texts: Is it possible to get a medical certificate from Canada and a pilot license in America?

texts:
I posted a question prior to this but it was too long and confusing. I have done some research and so I will ask:

If I obtain a medical certificate from Transport Canada (TC), and get my commercial pilot license through the FAA, can I work in the US as a commercial airline pilot and take school there?

I am a diabetic, so I can't obtain a class one or two medical certificate in America, but I can in Canada.

You can still fly in US airspace if you get a medical certificate from Canada, but I don't know if that's like from Canada into America.

Feel free to edit this question so it's more clear, I will include requirements from TC and such below.

On the second link, can someone explain it a little more to me? I am not great with understanding such things, I am sorry!

TC medical certificate regulations

Pilot medical certificate international use


texts: Where can I find a flight log archive for commercial flights?

texts: I heard that commercial flight logs are publicly available from the FAA, including mechanical delay reasons, etc.  Is this true?  If so, where can this information be found?


texts: I was chatting with an friend about the Embraer 135/145 and he mentioned that the engines have CVG. I assumed it might stand for "continuously variable" something, maybe "gearing," but I'm not totally sure. What is CVG and how does it impact engine performance?


texts: Is the FAA Medical Exam an IRS Medical Expense?

texts:
Does the FAA Medical Exam for a medical certificate qualify as a Medical Expense per IRS Publication 502 (thus allowing one to deduct the expense, or utilize a Health Savings Account (HSA)/Flexible Spending Account (FSA))?

One possible way to have the medical exam qualify as a medical expense would be to have a standard physical exam and the FAA medical exam together (which might also let you claim it with your health insurance).

Is this interpretation correct or consistent with your experience?


texts: What is the function of variable inlet guide vanes in terms of pressure change?

texts:
Nowadays in the turbofan Variable Inlet Guide Vanes are more and more used. My question is: which is their function in terms of pressure change?

The question is very specific: I know that they allow to give the most proper direction to the fluid, but do they act also to increase the pressure? So: what happen between the inlet and the outlet of each blade, talking in term of pressure?

I need some reference, if possible.


texts: Was the B727's wing supercritical (even if not so designed)?

texts:
The Boeing 727's wing upper surface appears unusually flat, especially at the root (Albeit at an angle).  Refer to the images linked below:

airlinereporter.com

Flickr

Also from Flickr

Was the B727's wing designed as supercritical? Did the B727's wing behave in a supercritical fashion, even if it wasn't explicitly designed as such?


texts: How do I calculate fuel reserves for IFR and VFR flight plan?

texts: I am trying to figure out how to calculate for IFR and VFR for a flight plan example. So from my basic understanding, VFR means you have to add extra 30 minutes to your fuel reserve, and 45 minutes for IFR. So if I wanted to make a flight plan, would I do distance/speed + .5 (for VFR) or + .75 (for IFR)? For instance, if I am calculating that I need an hour's worth of fuel to go a distance of 100 miles at 100 MPH, how would I figure out how much fuel I'd need taking VFR/IFR into consideration?


texts:
I came upon this clip on YouTube this week:

It appears to depict a Boeing 727 in British Airways livery. My first thought was that it's a Trident, but it is definitely a B727. I was a regular visitor to Heathrow and Gatwick in the 70s and 80s in my plane spotting days and I don't remember BA ever operating 727s.

So, how did this 727 come to be painted in BA colours?

Bonus question: which airport was this filmed at, since it's not either of the two main London airports?


texts: What information an aircraft responder must give to mode S ground receiver

texts: What is the minimum set of information (for ex.: aircraft registration, position, altitude ... and what else) that a transponder in an aircraft must provide after being interrogated by a ground station ? Is this defined somewhere ? Is there information about the airport of departure/arrival ?


texts: How does ATC locate a stealth aircraft if its transponder fails?

texts:
Stealth aircraft are built to have near-zero radar visibility, so that, in a warzone, it'll be harder for the enemy to see it on their radars to shoot it down.

However, air traffic control also use radars.

Normally, this wouldn't be a problem, since the aircraft is carrying a transponder that continually broadcasts positional and movement data (so-called "secondary" radar returns), not just to ATC, but also to other nearby aircraft (so that they can avoid running into it).

If an aircraft's transponder fails, though, then ATC is reduced to tracking it via "primary" radar returns (literally bouncing radio waves off of it and seeing where they're reflecting from)... but stealth aircraft are specifically built so that they can't be picked up by most primary radars (at least without a lot of trouble).

So how does ATC - and, for that matter, all the other planes in the air who would rather not run into it - know the position of a stealth aircraft if its transponder fails?  Do they have the flight crew of the stealth aircraft continually read off map position, height, speed, direction, etc. data and try to use this to steer other planes away from it?


texts:
During WWII, a number of German companies received financial backing and slave labourers from the government at the time. Companies such as Hugo Boss, Volkswagen and Lufthansa.

A thread on Airliners.net from 1999 mentions a documentary showing Lufthansa planes flying with the Swastika on their tail. I found this image online:

What is the story behind Lufthansa's involvement with the National Socialist Party? Did they indeed receive large monetary backing from the then-government?


texts:
What is the fan tip speed at maximum thrust? Is it any different for a Rolls-Royce Trent 900 (powers the Airbus A380) and Pratt & Whitney PW6000 (powers the Airbus A318)?

Are they efficient at maximum thrust?


texts: What is the sink rate of a glider during a roll?

texts:
For a glider in a steady bank at angle $\mu$, to a good approximation, the sink rate has a factor $1/\sqrt{\cos \mu}$ relative to the sink rate at zero bank angle.

What are the dynamics of the sink rate during a roll, for instance, when rolling from a bank angle of zero to a bank angle of $\mu \sim 20^{\circ}$ in one second?

I'm not looking for a very precise, quantitative answer but rather some qualitative idea of the physical effects that underlie the dynamics of the sink at such roll rates for a model plane.

Any references or guidance will be helpful, thanks!


texts: Would it be feasible to develop a dirigible-based refueling station for fighter aircraft?

texts:
The impossibly bad 2005 film Stealth featured a dirigible-based, mid-air refueling tanker station for the stealth fighters to use.

At first, this seemed like it might have been the singular good idea in the film as a dirigible would have a very long loiter time making it ideal for fighter refueling.

But I don't think it's possible, right? What is the maximum known air speed of a dirigible vs. the lowest possible air speed for a tactical fighter?

(Note: I do think it'd be possible for helicopters and osprey to use a dirigible tanker, right, as their stall speeds can be essentially zero?)


texts: Do pilots get full credit hours when they fly double or augmented?

texts:
In commercial airlines, in some very long flights as far as I know they require double cockpit crew sets (2 pilots, 2 co-pilots) to operate.

Do both crew sets get the full credit hours for these flights? Or do they get 50% only as they only operate half of the flight?

It would be nice if there's some sort of airline policy to back up the answer.


texts: Im thinking the window sequence and the shadow (possible a prop?) Might be your best help. My dad bought this photo and him nor I can figure it out. I work at a dang airport, too! TIA.


texts: What is relation between Reynolds number-turbulent flow-flow separation?

texts:
can some explain conection betwen re number -turbulent flow -and flow separation ,in example at wing in the air and water?
1)does high numbers= turbulent flow mean higher resistance to flow separation and low numbers=laminar flow less resitance to flow separation?
(becuase we use vortex generator to make trubulent flow which delay flow separation on upper wing surface...)
2)why L distance of chord has something with which type of flow will be over wing?
so wide chord will have more turbulent flow but it will delay flow separation?
3)in formula i see density and velocity in numerator,so high density and speed will delay flow separatin compare to lower density and lower speed?


texts: In this F-104 V-n diagram, why does the stall speed (in terms of IAS) decrease with altitude in some parts of the flight envelope?

texts:
(This question has been edited to reflect a change in perspective: based on answers to the related question What is causing these "corners" on this F-104 V-n diagram?, I now believe that the curves on the upper left edge of the envelope are intended to represent the stall speed throughout their entirety, both above and below the distinct "corners".  If the aircraft is being limited by something other than the actual stall along some portions of these curves, then it would be helpful to clarify and explain that in an answer either to the present question or the one linked above.)
In this V-n diagram for an F-104 (source: this Wikipedia link), why does the stall speed at any given G-loading (in terms of IAS) decrease with altitude-- at least in the part of the envelope that is below the sharp "corners"?
And why is the opposite is true for data points above the "corners"?
For example-- (numbers are approximate)--
Below the "corners"--
20,000', 5G, 415 knots IAS, versus 30,000', 5G, 375 knots IAS
30,000', 3G, 330 knots IAS, versus 40,000', 3G, 295 knots IAS
60,000', 1G, 175 knots IAS, versus 70,000', 1G, 140 knots IAS
Above the "corners"--
30,000', 5G, 375 knots IAS, versus 40,000', 5G, 475 knots IAS
And why do the curves cross each other?
(For example, at about 350 KIAS and 3.5G, the 40,000' curve crosses the 30,000' curve.)
Related ASE questions and answers-- but some of which seem to suggest the opposite relationship should be the case (at least for the "below the corners" cases)--
Why does indicated stall speed change? (see question and all answers)
What causes a slight increases in indicated stall speed with altitude? (see question and all answers)
How does the IAS stall speed vary with increasing altitude? (see question and all answers)


texts: Are the details of flight control laws the same for every fly-by-wire Airbus aircraft or are they only the same within the specific family?

texts: I was wondering if someone learns the details of every single flight control law for the A320 family, does that knowledge still apply to all the other Airbus aircrafts? If not, what are the differences?


texts: Orange object on back of jet-engine pylons, what is it?

texts:
Watching this Video of a L-1011, I noticed an orange/brown object on the back of the jet-engine pylons I never saw before.

What is it?
What's the purpose of it?


texts: Why are some dynamic derivatives not included in DATCOM file?

texts:
I am trying to understand Flight dynamics, particularly I am using Missile Datcom to get aerodynamic parameters of a missile, then use MATLAB, simulink to simulate its trajectory. It seems there are a lot of dynamic derivatives, have a look at
this, look at some dynamics derivatives.
 So why don't we have Normal-force derivatives due to yaw rate or Normal-force derivatives due to roll rate ? why don't we have Yawing-moment derivatives due to pitch rate ? etc...


texts: Where can I find an accurate list of IATA meal codes?

texts:
I'm trying to "compile" single list of IATA meal codes. By using different airlines and data sources I have found many meal codes. However, I have also found problems with codes that are used to mean different things, or different codes used to mean the same thing. For example:

On Cathay Pacific's special meal page I have found an information, that both Non-Beef Meal and Liquid Diet Meal are using the same code of SPML. These meal types seems to be far different. How to understand this? A bug on CP's page? To make things more complicated, another source uses SPML code for Special Meal or Specify Meal.
Cathay Pacific uses VGML for Vegetarian Vegan Meal (Strict vegetarian food with high protein, rich iron and high calcium). Other source uses VVML code for this meal type and have VGML code reserved for Vegetarian Non-Dairy Meal. Is there any difference between these two meal types and if yes, then which code is correct / official according to IATA.

Help with the above two examples would be appreciated. However, my main question is:
Where can I find official IATA codes for food?

If there is any "ultimate source", that we can / should use for this purpose (ignoring airline's specific listings, as in case of Cathay Pacific)? If so, then please, provide a link to it.

EDIT: Please, consider above paragraph. This question asks official IATA meal list, not about airline-specific regulations.


texts: Do airline pilots routinely carry out "gross error" checks?

texts:
Malaysian MH132 seems to have had a bit of a mix up over flight plans.  It appears to be a non-event but it does make me wonder if "gross error checks" are commonly used by airline pilots.

I'm only a PPL(H), but gross error checks are built in to me from training. For example, "after setting off on the first leg, the compass should be pointing NE which means the town should be on my right and the river on my left".

Some commentators have remarked that the captain did a "great job" in recognising the unexpected heading and querying it.  To me, it seems like basic airmanship to recognise and query it and leads me to also wonder if the crew studied the route during pre-flight and after it was loaded into the FMC.

Can any airline pilots add facts to the story?


texts: What are the rules for racing on airport runways?

texts: What are the adverse affects of burnout rubber left on the runways for airplanes?


texts: Is there a significant difference between the jet blast from Airbus and Boeing?

texts:
I am looking up for jet blast data and there are not much information in the net.

One of the main references I can found are the Airport Planning of each aircraft.
From these can be obtained that the jet blast contours from Boeing's aircraft are quite longer than the Airbus's ones at idle and breakaway conditions (the double in length of the jet blast print).

According to this, simulations carried out using specific software (AeroTurn, in this case) show that the jet blast affected area by a breakaway run of a B737-800, for example, would affect stands in a 100 m backwards zone, which is far from the truth.

Some researches can be find Googling a little, but they show comparison between simulations and experimental jet blast data from a JFK test campaign, besides the own JFK data.

Could anyone confirm if the difference is real? A mapping study, an experimental analysis or other similar evidence would be useful.

Thank you everyone for your help, and thanks for all your work in the community.


texts: Does the FAA allow a jet bridge to approach an aircraft that has engine #2 running?


texts:
Currently Australia is deploying F/A-18E/F Super Hornets to the UAE to fight in Iraq. Obviously the UAE (and Iraq) is a very long way from Australia and well beyond the typical range of one of these aircraft.

On TV they literally showed the Australian Prime Minister waving goodbye while the jets took off and flew into the distance, which for some reason seemed odd and made me wonder about how fighter jets are typically ferried to a distant war.

I kind of assumed they were loaded onto an aircraft carrier and shipped there, but Australia doesn't have an aircraft carrier so obviously this isn't the case.

I assume they must therefore fly, but:

Do they fly hop to hop within their usual range refuelling at each stop? Where would these stops be? I assume they can't just refuel at a civilian airport in an arbitrary country and would have to be an air force base belonging to a close ally.
Do they fly continuously with aerial refuelling? Does the tanker need to make hops to refuel?
Do they swap their weapons for extended fuel tanks which provide enough range to fly continuously to the UAE?
Are they actually shipped via regular military cargo ship and the "departure" on TV just for show?
If they do fly continuously, it seems like flying non-stop for ~13 hours in a cramped fighter pilot cockpit would be unreasonable (even commercial pilots take shifts), or would they fly supersonic and perhaps reduce this to 5 or 6 hours?

Answers don't necessarily have to be Australia -> UAE specific, I'd also be interested to know how the US deployed to Iraq and Afghanistan for example and if the process is consistent or depends on the aircraft and location.


texts: What currency requirements exist specifically for Commercial and ATP pilots that a Private pilot wouldn't know about?

texts: Besides a different medical certificate, what other currency requirements do commercial and ATP pilots have to contend with that a private/instrument pilot would not?


texts: Can anyone identify the aircraft in the background of this photo?

texts: This photo was found in some family belongings and we're trying to date it to identify the family member who may have been in his tri-service imaged. So, can anyone identify the plane in the background please?


texts: Why is the F-35B's elevator not in neutral position when in vertical flight mode?

texts:
I was watching videos of F-35B taking off and landing vertically on ships when I realized that when transitioning from horizontal to vertical flight mode (I don't know the exact vocabulary to describe that), the horizontal elevator moves to "stick pushed full forward" position. The elevator is also put in that unusual position when transitioning from taxiing to a vertical takeoff. I know that the elevator position is not significant in vertical flight as attitude is controlled via non-aerodynamics means. Thus I wonder why this control surface is then put in that position for that flight phase instead of staying in its previous position or in a more neutral position.
I'm even more confused as this behaviors doesn't seems to be reproduced on other VTOL fighters such as the AV-8B or the Yak-141.


texts: Where can I take ICAO Aviation English proficiency test?

texts:
Do you know some pages which listing the place I can take ICAO Aviation English proficiency test or useful pages?
I sent e-mail to ICAO and search it many times. But, still I can not obtain good information.


texts: At what altitude, if any, may an ultralight overfly the Gallup airport (KGUP) with no prior authorization without violating FAR 103.17?

texts:
At what altitude, if any, may an ultralight overfly the Gallup, New Mexico airport (KGUP) with no prior authorization without violating FAR 103.17?

This is a question about the meaning of

  "within the lateral boundaries of the surface area."

Resources--

FAR 103.17 --

  "No person may operate an ultralight vehicle within Class A, Class B, Class C, or Class D airspace or within the lateral boundaries of the surface area of Class E airspace designated for an airport unless that person has prior authorization from the ATC facility having jurisdiction over that airspace."

Sectional chart depicting KGUP

Description of the E2 airspace at KGUP-- from page E-116 of the FAA's "Airspace Designations and Reporting Points" document FAA Order 7400.11D--

  "ASW NM E2 Gallup, NM
  Gallup Municipal Airport, NM
   (lat. 35°30'41"N., long. 108°47'15"W.)
  Gallup VORTAC
   (lat. 35°28'34"N., long. 108°52'21"W.)

  Within a 4.1-mile radius of Gallup Municipal Airport and within 1.3 miles each side of the 242° radial of the Gallup VORTAC extending from the 4.1-mile radius to 4.9 miles southwest of the airport."

Note that no limitation is given as to the time of day that the E2 airspace is in effect, and therefore it is in effect 24/7.  No specific altitude limit is stated in this section, though on page E-1 we read--

  General.

  Generally, if the airspace is not Class A, Class B, Class C, or Class D, and it is controlled airspace, it is Class E airspace. Class E airspace extends upward from either the surface or a designated altitude to the overlying or adjacent controlled airspace. When designated as a surface area, the airspace will be configured to contain all instrument procedures. Also in this class are Federal airways, airspace beginning at either 700 or 1,200 feet above ground level used to transition to/from the terminal or enroute environment, and enroute domestic and offshore airspace areas designated below 18,000 feet MSL. Class E airspace does not include the airspace 18,000 feet MSL or above.


texts: For the CFIs, CFIIs, MEIs, and AGIs - How often do you find students that utilize your ratings?

texts:
I am curious. Out of 100 new students that walk into the average flight school, how many only need a standard CFI, how many do instrument training, and how many do multi-engine training? Additionally, how much work does an AGI get? I’m trying to compare the cost of these ratings against how often they will be utilized.
Also, for the sake of data that makes some kind of sense, let’s exclude the recent Covid-19 market activity and go with pre-February 2020 numbers.


texts: During the holding procedure is it required that the pax must have the seat belt on?

texts: Imagine to have to hold at a busy airport before landing for a quite long time (let's say 20 plus minutes), does it requires that the pax must have the seat belt on during the whole holding procedure? Is it required by the Authority or just by the company?


texts: What should a pilot flying IFR in IMC and on final, do if the vacuum system fails?

texts:
Talking about small aircraft here, assuming the pilot is stable and ready to land, they’re flying IFR and the visibility is nonexistent, but that’s alright because he’s currently IFR! But then the vacuum system fails. The pilot loses:

 Attitude Indicator

 Heading Indicator

 Turn Coordinator

With a very poor visibility I can see how this could end up fatal. What is the do’s and don’t here? I can easily see that with every scenario there can be an argument for both “do” and “don’t”. Pilot could go around, but at the same this may not be smart because you don’t know the pitch of the plane, at the same time I see it being okay because you know airspeed.

I can also see a reason to continue on, to try and see if you can visualize the runway and land, seeing you know your altitude, at the same time I can see how that can be disastrous. So what’s the correct way to go about this type of failure in horrible conditions?


texts: How do I calculate the centre of gravity on the lateral (transverse) y-axis?

texts: I have a real issue with determining the centre of gravity for the y axis of an aircraft, especially with selecting the reference/datum point and how to measure the displacement. Please I would really appreciate any form of help I can get.


texts: Are Final Tests always required for LRUs?

texts: Is an aviation component workshop allowed to release a line-replaceable unit (LRU) without going through a Final Test, if the LRU passes the pre-testing procedure and is found to be a No Fault unit?


texts: Difference between Flight path and Route

texts: What is the Difference between a Route and Flight path


texts: Can civil pilots *ever* fly military high-altitude penetration approach procedures?

texts:
Let's say I'm flying some business types in a Gulfstream III (an approach category C aircraft) from Stockton to Palmdale to meet up with some USAF types there (new airplane deal, wooo!).  Can I accept/fly the HI-ILS approach to RWY 25 at KPMD:

or am I only allowed to accept a STAR or vectors to a standard ILS approach to KPMD?


texts: Would this be a dangerous impeller to use for a drone?

texts:
I am considering using a 3D printer to make unconventional impellers for a custom-made drone that I am planning to build. I am concerned that these plastic impellers may explode if their motors' RPMs get too high.

Please see the drawing below.

This drawing is showing two views of an enclosed centrifugal blower impeller with forward curved blades and the bottom plate of the impeller has holes in it. I am thinking that the high static air pressure that will be created within the impeller will generate a good amount of lift for the drone.

This design was inspired after I watched a Youtube video about a drone that uses cross-flow fans for lift:

My concern is that if the motor's RPM gets too high, the static air pressure inside the enclosed impeller will get too high and the impeller will explode, sending plastic shrapnel in all directions.

Because of this explosion risk, would it be advisable that I not use this potentially dangerous impeller?

EDIT

I just want to point out that the blades will be embedded within the enclosed impeller and that the whole impeller is rotated by a motor. The blades will not be part of a separate squirrel cage that will spin within a stationary enclosure that has holes in the bottom of it.


texts: Which companies develop software for airplane systems?

texts:
I am wondering which companies develop software for systems on airplanes?

I am a software engineer major and I would love to work with planes in some way. I am not sure if that would be more of an electrical engineering position or not, any input would be greatly appreciated.


texts:
Waypoint names are not unique. Why ?

This is unnecessary (it would be possible to use unique names only).
It introduces potential for confusion.

So why are duplicate waypoint names permissible and used ?
I don't see a good reason for that.


texts: Why would it be logical to call clearance delivery prior to CTAF during an instrument approach?

texts:
I am quoting this directly from the FAA's Instrument Procedures Handbook publication.

  "The communication strip provided near the top of FAA approach charts gives flight crews the frequencies that they can expect to be assigned
  during the approach. The frequencies are listed in the logical order
  of use from arrival to touchdown."

Here is the communications strip from the plate in the prior page:

Never once have I been trained to contact clearance delivery prior to CTAF during the execution of an instrument approach procedure, much less any time other than when I am trying to get my initial IFR clearance.

Why is this listed before the CTAF?  Would a tower or ground frequency not be more appropriate and would it not be more appropriate to have it in logical order as the last frequency, not the second-to-last?


texts: What is the exact purpose of the string attached between front fuselage & the tail section of the transport aircraft's?

texts:
]2 228]3]3

Usually I got to notice a string attached between front fuselage to rear tail section of the transport aircraft's, what exactly might be the purpose or function of it? But comparatively, I don't find to see on commercial aircraft like Boeing 747, 737, A380 etc. why is that so!


texts: Where is the aerodynamic center for an A320?

texts:
Aerodynamic center, aka the Center of Lift or Center of Pressure. I would like to know where this is for an A320 airplane.

Sadly I don't know how to estimate aerodynamic things. I can do it for the center of mass, but when it comes to aerodynamics, I cannot simply find the geometric center of multiple arranged bodies, each one assumed to be uniform density. If anyone knows a trick or method of estimating the aerodynamic center, please let me know.


texts: Does aeronautical experience ever expire?

texts: Do the hours of flying with instructor or solo ever expire? I have my 50 (yes, 50) year old pilot's Flight Log with CFI entries for 20 hours dual and 1 solo. Do I have to start over, or would some of them count for PPL license?


texts: Why do some commercial aircraft have no landing gear cover?

texts:
The B737 has no cover on its landing gear, as may be seen in this picture. Doesn't this increase the air drag?

Almost all other airliners have doors that close off the rubber of the wheels, for example this B787.

Why doesn't the B737 have a cover on its landing gear?


texts: What is the correct name of this aircraft subsystem in English?

texts:
I would like to know what the correct name of this aircraft susbsystem is in English:

(Source)

name: пилотажно навигационный комплекс
+/- literally translated it could be something like: flight navigation system.

I am looking for some sort of blockdiagram of this system of either an F-35 (my favorite) or otherwise a boeing airplane. A blockdiagram which components are used and how they communicate with each other. E.g.:

(Source)

Could anybody suggest me some good places to look for?


texts: What is the daytime visibility from within a cloud?

texts: I ask this question from the context of formation-flying, such as during WW2. What is the visibility in a typical cloud during daytime? Can you lose your wingman right away? Were you at serious risk of mid-air collision when this happened?


texts: Why is the Cumulonimbus cloud formation so dangerous?

texts:
I once heard my pilot friend say that it's really dangerous to fly near any Cumulonimbus cloud formations... Something about that it could drag the plane into it.

Cumulonimbus :

Why is it so dangerous?
How is it created?


texts: In EASA, what is Panel 12? Is this just the same as Panel 10?

texts:
IN EASA safety approval guidance, particularly CM – SWCEH – 001
Development Assurance of Airborne Electronic Hardware, the entity charged with making sure that a system meets applicable requirements and guidelines (especially concerning safety) is called "Panel 10."
However, in section  5.2 "Background" there is a list of panels, and there, Safety is listed as Panel 12.  (Immediately after this list comes most of the assurance-related material, which extensively speaks of Panel 10.)  Yet no other mention of Panel 12 is made in this document.
Is this just a typo, where they meant Panel 10, not Panel 12?


texts: Which was the last Boeing crash that didn't send its black boxes back to the US?

texts:
I couldn't find an answer online, so I am asking the community.

The real question is how frequent it is for a Boeing crash not to send the black boxes back to the USA, and a reply to title's question would be a good basis for the real answer.

My feeling was the black boxes were sent back to the US for analysis (maybe I watched too match Mayday).

Article(s) mention that sending the data recorders to the USA would be to allow a party with a vested interest to be a judge in its own case, but this, I imagine, could be the case in older incidents too - but my feeling that wants the Boeing black boxes to be sent back to US invalidates the article's argument.


texts: Can a non-US citizen (or entity) own an N-registered aircraft?

texts: Distantly related to this question, but can a non-US citizen (or corporation) own an N-registered aircraft?


texts: What is being depicted w.r.t. AoA in this video?

texts:
I was looking at this video of the AF447 crash simulation and at about 4:45 the angle of attack diagram shows a few things I don't understand (frame above).

I get the orientation of the airplane, pointing a few degrees above the horizon, but what does the green line represent in layman's terms? Is that the direction the plane needs to go for the wings to generate lift?

Also, I see the red line has to do with the warning, but how does that play into it as well?


texts: When to disconnect the A/P on approach in an airliner?

texts:
I've looked at the other question asking about when to disconnect the AP on an airliner and I get that it's very situational depending on the pilot and conditions.

I've found I'm too reliant on the autopilot for an auto land in my PC flight simulator. I've been trying to practise manual landings but I'm suffering badly from when I do manage to stay on course with the runway of doing 600-900 fpm landings or floating way too long and I know this isn't down to getting my flare right.

Are there any tricks to improve my landings? I've been trying to start disconnecting the autopilot once I'm on the glide at around 2000ft but I'm finding I'm ending up not lined up with the runway. The only way I usually land well is if I disconnect at around 200ft and even then I usually land hard.

Is it common for pilots to fly in manually the full glide or is it a lot more common the only fly the last few hundred feet manually?


texts: What aircraft are these, and why are these engine sizes so different?

texts:
These glamorous vintage images were once famous in magazines and used by airlines to advertise their products, and yes, flight attendants clothing was like this! Old and more relaxed times, though flying was for the rich.

Left: Canadian Pacific, 1968.
Right: Pacific Southwest -  San Diego Air and Space Museum Archive, likely end of 60s too.

With a flight attendant showing the scale, it's pretty clear that the size of the engines are completely different; they are likely of different designs (turbojet/turbofan) in spite of being of the same period. What are theses engines, and the aircraft that used them? Why so different choices (what did that change for the airlines)?


texts: Can an amateur-built aircraft ever be used for commercial activities?

texts: There are some non-recreational activities, such as aerial photography, wildlife observation, environmental monitoring, etc., that seem well-suited to certain amateur-built aircraft.  The open-cockpit Lockwood AirCam, which I understand was specifically designed with back-country nature photography and videography in mind, is just one example.  Yet FAA regulations relating to airworthiness certificates appear to make no allowance whatsoever for an amateur-built experimental aircraft to be used for non-recreational/non-educational purposes.  Am I misreading the regulations?  Is there a legal way to use a homebuilt airplane for, say, commercial aerial photography?


texts: What are the regulations on flying UAVs over people on the ground?

texts:
We are considering a project related to drones and in my discussions with people I heard that flying UAVs overhead people (crowds or otherwise) is banned. I also heard this is the case for the USA and EU. I searched and couldn't find the related detailed explanations anywhere.

I would be grateful if somebody could shed some light and point me in the right direction.


texts: What material is used for the floor panels in the main cabin for Boeing 747-400?

texts:
Just conducting some research into materials used in construction for Boeing 747-400 and Douglas DC-3.

I just found out that in a DC-3 the floor panels in the main cabin and companionway are of plywood.

As such, I tried to find the information with regards to Boeing 747-400, but was unsuccessful.

I was hoping someone could provide me with information with regards to the material of the floor panels in the main cabin and companionway of Boeing 747-400.


texts: What is the difference between point-to-point and low-cost airlines?

texts: In describing major airlines, are "point-to-point" and "low-cost" synonymous? Or is this an over-generalization?


texts:
I know that DC power is essential for avionics and that in medium and big airplanes AC (28 V, 400 Hz) is used with DC (28 V).

Small airplanes have a starter-generator that provides DC, but do they have an inverter too, to provide AC? If yes, then why use AC, and in which systems? And when is AC 26 V used?


texts: Are bigger and / or heavier aircraft more resistant to crosswind compared to smaller / lighter aircraft?

texts: When watching heavy crosswind video compilations, I noticed heavy aircraft like the A380 an B747 have a more stable approach compared to the B737 or A320 where the plane banks left and right on approach more frequently.


texts: Why do newer commercial aircraft have their wingtips curved up?

texts: Lately I've seen a lot of aircraft that have the wingtips curved up.  What is the reason for this?


texts: Why are magnetic headings used for designating runways?

texts:
Runways are numbered based on compass heading. Why?

Does this help pilots in locating the runway, even in today's GPS age? Or are there some other technical reasons behind this?


texts: What body creates legally binding aviation regulations in Europe?

texts:
Currently trying to get general picture of aviation organisations in Europe. At what stage do regulations get the status of a law?

ICAO issues SARPs, they are certainly not a law. Then, on the basis of SARPs, EASA issues legislation. Still, EASA is not a regulatory body.

Consider PART FCL, for instance. Does it have the force of law, or is it just a guidance for the local CAA to issue a regulation, which will be considered as law only for that specific country?


texts: What are the effects of crosswind on takeoff?

texts:
What is the specific aerodynamic effect which requires one to hold into-wind aileron to keep the wings level during takeoff in a B737? (i.e. dihedral or sweep)

Subsequently, what is the aerodynamic reason for having to increase that into- wind aileron input immediately after Takeoff.


texts: How many US airman's certificates are revoked, roughly, per year?

texts:
There is a lot of literature devoted to FAA enforcement (see https://www.aopa.org/training-and-safety/pic-archive/faa-enforcement/faa-enforcement)

What is the threshold for revocation? The thing that specifically got me interested was a near collision runway video - assuming it wasn't an ATC/taxing instructions error, would this type of thing be sufficient? I'm also interested in what the appropriate penalty would be for that


texts: Do "Civil Aviation Regulations" and "Aeronautics Bulletins" still have any legal authority today?

texts:
This is a history of the FAA from their site.

In the U.S., we had the original set of aviation laws known as aeronautical bulletins back in the 1920's and 1930's. Later (in 1938) we had the Civil Aviation Regulations (CARs), created by the Civil Aeronautics Authority (CAA), added to them.

I am curious if those laws were actually repealed or simply made redundant by today's regulations and whether or not there were additional laws not seen in the FARs today but which did exist in the CARs and Aeronautical Bulletins.


texts: Although VOR stations follow magnetic north, do VOR's on a chart follow true north?


texts: What do airline pilots eat on a flight, and when?

texts:
Do airline pilots eat while flying or do they wait until they are back on the ground?
If they do eat, do they get the same food that is served to the passengers or do they bring their own meal?


texts: Why do airlines over-estimate/over-calculate flight times?

texts: A specific example I'm referring to is Cathay Pacific's CX138 flight between Sydney and Hong Kong. This flight is scheduled to be 9 hours & 40 minutes long (departing SYD at 22:20 local time and arriving HKG at 05:00 local time) but in reality from Flightradar24 data, as well as having been on the flight, it seems that this flight consistently arrives around 03:45 to 04:00 average, which is a very early arrival. So why is the scheduled flight time so over-stated ? (Ironically, other CX flights between SYD & HKG at other times of the day have shorter scheduled flight times)


texts: Can a helicopter carry a large airplane?

texts:
I saw on YouTube a helicopter carrying an airplane.

Is this possible, I mean is the maximum load compatible with the mass of this aircraft?


texts: What things can a passenger look out for, to indicate an emergency?

texts:
As a passenger with a keen interest in aviation, I'd like to think I'd be eagle-eyed enough to spot a problem that the pilots mightn't be able to see, from where they're sitting (for example, an engine sputtering or ice on the wings).

What things can we look out for, sat in the cabin, that might ultimately save a plane?


texts: Why don't airports use arresting gears to recover energy from landing passenger planes?

texts:
An average plane has 50t of mass and a landing speed of approx. 250 (lets be conservative) 200 km/h. Thus its kinetic energy at landing is about 75 MJ or 21 kWh.
The plane catches the wire attached to a pneumatic or hydraulic system, which will decelerate the plane and harvest its kinetic energy. The built up pressure in the system can be released via some kind of turbine to convert the pressure (potential energy) to electricity. Lets say the system has 50% efficiency. Leading to 10kWh harvested energy, per landing.

The airport in Hamburg, Germany is just average. Not large and not small. They had 150 000 flight movements in 2017. Lets say half of them are big planes and 1/2 were landings. That is 37,5k landings per year. Lets say 2/3 could use the arresting gear system:
This would provide a cumulative 250 MWh of harvested electricity per year. This is equivalent to the electric energy consumption of 100 two person households in Germany.
In Germany 1kWh electricity costs about 30 euro cents (including tax etc). An airport could save 75000 euro per year when harvesting this energy and use it, instead of buying it from the net.
I can't imagine, that such a harvesting system would not pay down after a couple of years.

Why there are no systems like this in the aviation industry?

Con:

You need to refit thousands of planes with a wire catching System
System has to be safe in case of a go-around
???


texts: Are jets deliberately excluded from the "Complex airplane" definition?

texts:
A jet aircraft seems for sure very complex as such. But, referring Wikipedia, a "complex aircraft" (as legally defined) has:

A retractable landing gear
Flaps
and A controllable pitch propeller

And there is no propeller in a jet.

What are the reasons of defining "complex aircraft" so that it does not cover jets? Are these reasons other than historical?


texts: Can an APU be designed to also provide emergency thrust in the event of a double engine failure?

texts:
Commercial airliners seem to be moving towards twin jets with incredibly powerful 100,000+ lb thrust engines becoming available for use.  Would it be possible to design the APU to provide enough thrust to push an aircraft to a nearby runway in the event they
both fail as a safety measure?


texts: Is there a difference between altitude and flight level?

texts: I came across a question in Quora asking the difference between altitude and flight level. One of the answers said that anything above the transition altitude is referred to as a flight level. So suppose an aircraft is flying at 35,000ft, it is flight level 350. Is this correct? Can we not refer to altitude as flight level below 18,000ft (the transition altitude)?


texts: Is there any effect that contributes to roll stability even in the absence of sideslip?

texts:
Is there any physical dynamic-- involving high wing placement, "pendulum" effect of CG far below wing, or anything else-- that contributes to roll stability in a way that is NOT dependent upon the aerodynamic forces generated by sideslip?

For the purposes of this question, "roll stability" is defined as a tendency to roll towards wings-level, or a reduced tendency to roll toward a steeper bank angle.  Perhaps a better term might be "spiral stability".


texts: Can you receive traffic advisories without a specific destination or intention?

texts: I’m wondering if it is possible to call up the local approach facility and ask them for flight following even if you are just doing sightseeing or something. Do you need to tell them your intended route, altitude, and destination? How would you ask them for flight following without a specific destination?


texts: Triple engine failure; which would you choose to keep left?

texts:
It is well known that planes with two engines must be able to land with one engine inoperable for their certification, and that four engine planes with two inoperable.

Now, suppose you had a four engine plane with 3 engines inoperable, and only one remaining. In terms of the greatest likelihood of survivability of this incident, is it at all favourable to have the engine closest to the body of the plane active, or the one further out?

As far as I can see it, there are two main ways to tackle this; one is by looking at incidents where triple engine failure occurred (which is very rare) and seeing whether it makes a difference.

The other approach is how does it affect the controllability and maneuverability of the aircraft theoretically or based on testing depending on if one has the jet engine closest to the body active, or the one further out on the wing. It may be that the difference is negligible, but I'd be curious if there can be some argument made to favour one option.

There would be other variables to take into account, so to narrow it down a little more, I am considering only jet engines, on aircrafts used for commercial flight.


texts: How can we physically define reynold number variation in terms of characteristic length?

texts:
How can you define it physically that
greater the characteristic length in
$Re=\frac{\rho v L_c}{\mu}$
greater the Reynolds number.
Like on wing surface $Re$ is higher than the horizontal tail surface (MiG 29).


texts: Where does an FMS wind information comes from to calculate V approach?

texts: To calculate the V approach the FMS is using a wind either taken by the ADIRS or inserted on APPR PERF page. At first I will say that it takes the wind inserted by the crew, but I am not completed sure about this assumption since the MINI FUNCTION on A320 will need as well wind info taken by ADIRS to be able to cope with sudden loss of headwind / increase tailwind.


texts: How do jetliners age (major or notable checks and part replacements)?

texts:
As commercial airliners can be (and are) operated for many years (or even decades), I've started to ponder - how do they actually age? Or - in other words - what are major or notable maintenance-related events (checks/replaces) during airliners' service life and how often do they happen?

While there are many parts that come and go every $x$ hours of flight or $n$ takeoff/landing cycles that are hard to list, my first guess was the engines or on-board computers, but then I thought about the fuselage. I assume that they are designed to withstand whole service time, but at the same time material fatigue seems to be unavoidable, and this holds for many other parts.

If that's possible, I'd especially like someone elaborated on Boeing 737NG and/or Boeing 747 (differences between the two - or lack thereof - might be especially intriguing), but any small to long range airliner will work.

If that question needs fixing/clarification, I'll be really happy to do so!


texts: What is the origin of the "Pickle" switch for release of ordnance?

texts: I am looking for proper proof of the theory that it is called so due to the Norden sight of the B17, which was said to assist the bomber in putting a bomb into a pickle jar, and hence it stuck.


texts: Which airports have the highest fuel upload?

texts: Which airports consume the most fuel for aircraft refueling, and how much fuel do they use?   I was able to find that "Heathrow uses about 20m litres of fuel a day", but it isn't easy to find figures for other airports.


texts: How many LRUs are there in modern aircraft like a Boeing 747 or an Airbus A380?

texts:
I work in the Avionics industry. I always wonder, how many Line-Replaceable Units (LRUs) are present in modern aircraft like A380 and Boeing 747.
I understand that number of LRUs varies from customer to customer. I just want to know in general how many LRUs present in an Aircraft.


texts:
So I understand how precession works, and that gimbals are used to isolate the gyro from outside rotation, however when a yawing motion is applied to the gyro, it'll essentially translate to a rolling (horizontal) motion on the gimbal to turn the indicator.
Since the gyro maintains its plane of rotation, would it be acceptable to say that if I applied force to a gyro, the precession from the gyro would be displayed on the gimbal not the gyro, since it has to maintain its plane of rotation?
To summarize, I'm just wondering how a gyro's precession affects the gimbals or how it affects the instrument if it doesn't affect the gimbals.
Thank you!


texts: There are a few parts to the control system for an aileron in a light aircraft, such as the rods, bellcrank, cables, chains etc. What are the main reasons for aileron failures and what parts wear the most during their time?