texts: A320: Why do SDACs supply all three DMCs?

texts:
On the Airbus A320, in the Electronic Instrument System (EIS), there are three Display Management Computers (DMCs):

DMC1 supplies the upper ECAM
DMC2 supplies the lower ECAM
DMC3 is a backup.

There are also two System Data Acquisition Concentrators (SDACs) that acquire system status, process it, and and send system page data to the three DMCs.

Why would it send it to all the DMCs?

The Hydraulic System is displayed only on the lower ECAM which is supplied by the DMC2. Nothing about the hydraulic system is shown on the upper ECAM supplied by the DMC1. So why would SDACs send data to DMC1? I can understand why it would send it to the DMC3 because its a backup but why the DMC1?

Same thing for the Air Conditioning System, Electrical System, etc. None of those systems are displayed on the upper ECAM supplied by DMC1. The only thing displayed on the upper ECAM is engine and MEMO (or emergency stuff in the case of an emergency).

I guess the engine is a system but there is an engine system on the lower ECAM as well. The upper ECAM shows the engine performance and the lower shows the oil, so not the same thing.


texts: What would be the challenges for a pilot taking off into a headwind of just under the clean stall speed?

texts:
If a strong and fairly steady headwind was coming down the runway at just under the stall speed for a clean configuration/weight, what challenges would a pilot face? Or would it be fairly easy? Is this something that happens often?
Edit: This is the video that made me ask.


texts: For supplemental oxygen, what is preferred between masks and cannulas?

texts:
There are two main types of supplemental oxygen devices in light aircraft:

Cannula:

Oxygen mask:

What are the major differences between these two devices? Is one more suitable for specific siutations than another, or is it just a matter of personal preference?


texts: Can lift be increased by increasing the angle of incidence of the wing?

texts: Can the lift of a plane be increased by increasing the Angle of Incidence (angle between the chord line of the main wing and the axis of the fuselage)? Meaning, can more lift be generated while the plane is in a horizontal position (i.e. not pitching nose up or down) if the wings are angled leading edge up.


texts: Why can't runway 18 at Frankfurt Airport accept takeoffs or landings in the opposite direction?

texts:
Runway 18 at Frankfurt Airport is one example of a runway which is numbered on only one side. Aircraft can only takeoff in the 18 direction, and cannot takeoff in the 36 direction, nor land in any direction except in an emergency situation.

What is the reason behind it?

Thomas Römer/OpenStreetMap data [CC BY-SA 2.0], via Wikimedia Commons


texts: What is the procedure to follow for "traffic not in sight"?

texts: What would be the proper procedure to follow, when in the pattern or approaching an airport, if ATC gives you the position of an aircraft and you do not have them in sight? Do you just report "not in sight" and wait to turn base?


texts: Does ATC handle non-regular widebody flights differently?

texts:
Six weeks ago, roughly, a Corsair charter flight landed at Lamezia Terme International Airport (SUF), in Southern Italy. It was a Boeing 747-422, registration F-HSEA. It carried 500 tourists from Liege Airport (LGG), Belgium.

My question: when a flight like this is headed to an airport which is not an usual landing spot for wide-bodies, how does the ATC figure out a wide-body is coming? Do they figure this out by just communicating with the pilots when airborne or do they receive an official note beforehand?


texts: When a Tower and the Approach Control closes who takes over the airspace?

texts:
When a Tower and the Approach Control closes, who takes over the airspace?
and also what about When a Tower, within an Approach Control, closes, who takes over the airspace?


texts: Why does the low voltage warning light not illuminate when the alt switch is on, but the engine is off?

texts:
As part of the pre-flight inspection, one of the checks is to verify that the low voltage light is illuminated when switching just the battery on. This makes sense; there's a low voltage and the battery is being discharged because we're running everything off the battery, and the alternator is not providing any power.

However, as part of the startup - just before ignition - we switch both the battery and alternator switches on. At this point, the low voltage light is not illuminated, despite the alternator not providing power as the engine is not running. This doesn't make sense to me - though we've turned the ACU on, the alternator is not providing power. This seems like something that should trigger the warning light.

I've examined the C152 POH and it shows a basic electrical layout. I'm not sure as to the copyright of the handbook, so I won't post it here. It is available online for those interested, figure 7.7. Unfortunately, this did not help explain the behaviour I'm seeing.

I've reproduced this on two different 152s. Why does the warning light not detect the fact that the alternator is providing no power, or am I completely misunderstanding the function of this light?


texts: Why did flying boats in the '30s and '40s have a longer range than land based aircraft?

texts:
I just learned that until shortly after world war 2, flying boats had a longer range than land based aircraft

In the 1930s, a flying boat route was the only practical means of transatlantic air travel, as land-based aircraft lacked sufficient range for the crossing. (link)

Why was that? I'm not aware of any reason why land based aircraft should have a shorter range than seaplanes.


texts: During airshows, how common is it to fly armed with (inert?) missiles?

texts:
I notices that these three Su-35s were armed with missiles during an airshow. At the 1-min mark, you can clearly see that jet #38 has 2 missiles under each wing as well as a bomb / (spare fuel tank?) and that jet #3 has a missile under at least 1 wing. At 5:25, that jet has 3 missiles. etc.

I assume these are all inert, non-explosive? And used to prove the Super-Flanker is still super-manuverable even when armed?

Is this common practice for all air forces to demonstrate the performance of their best jets even when armed? I've thought of airshows as a demonstration to "the people" where you try to impress them with aerobatics and get them to clap and appreciate how much money is being spent on the air force. Thus, why the weapons?

Of course, if Russia were trying to get Erdogan to switch to the Sukoi family, then you must demo fully armed jets.


texts: What are the requirements for foreigners to join the RAAF as a fighter pilot?

texts: What are the requirements for a foreigner (personally I'm from Cyprus) to join the Royal Australian Air Force to become a fighter pilot?


texts: Are there any locations where I could launch a rockoon with minimal red tape?

texts:
I'm currently working on a research project on hypersonic control surfaces, and as part of it, I'd like to launch a rocket-assisted lifting body from a high-altitude balloon.

Are there any locations in the US where I could do this? The first thought that comes to mind is launching at sea, but recovering a small craft (~ 1 meter wingspan) from the open ocean seems like a logistical nightmare. Ideally, I would prefer to launch over land that can be accessed with relative ease by car or offroad vehicle.

At one point, I read about a section of airspace in Alaska with basically no regulation but I can't seem to find that information now.

Thanks!


texts: When can I proceed inbound in a hold in lieu of a procedure turn when cleared for the approach?

texts:
Let’s say I am holding on a published hold in lieu of a procedure turn but not yet cleared for the approach. Upon receiving approach clearance (say on the outbound leg of the hold) would I have to cross the fix an additional time before proceeding inbound?
I have attached a picture as an example and a red X where the approach clearance is received.


texts: Why does idling RPM increase with altitude in a jet engine?

texts: The Snecma-Larzac 04-C6 idling RPM ranges from approximately 53% on the ground to 85% at high altitude. Why is that?


texts: Is it true that cockpit doors are bulletproof?

texts:
I read about 9/11 and read somewhere that after 9/11 all aircraft cockpit doors were replaced with bulletproof ones.

Is this true?


texts: Is it possible to take PPL lessons in different locations and countries?

texts:
I have been wondering if it is possible to do flight lessons in different locations? For example, I am currently taking my PPL lessons (VRF) in Manchester, UK. I usually travel between countries in Europe and America.

I was wondering if my travels take longer than 2 weeks if it was also possible to take the opportunity to do a lesson in one of them? Or if regulations would made it impossible to do so?


texts: What does Lockheed have to do to mark the end of the F-35's SDD?

texts: What does Lockheed Martin have to do to mark the end, or close out, the System Development and Demonstration phase of the F-35?


texts: How do I determine which radial intercept angle to use?

texts:
I'm studying for the (EASA) Instrument Rating exam and I found several questions about radial intercept angles in sample exams but nothing in the books I've studied and my flight instructor doesn't know of any specific rules either.

Based on the answers, it appears that, depending on the current and desired positions and headings, the intercept angle can be 30°, 45°, a third of the heading difference or a combination of a 90° then 45° turns.

What is the rule to determine which intercept angle to use and where is it documented?

  Sample questions:

  current QDM 330, HDG 060, desired QDM 350, what should be the new heading? (answer: 305 for a 45° intercept)
  current QDM 120, HDG 120, desired QDR 060 after flying over VOR, what should be the heading after flying over? (answer: 040 for a 20° intercept angle, a third of the 60° heading difference between 120 and 060)

Note: I've found this document online that mentions the 45° and 90-45 techniques page 20 but it doesn't cover the other cases.
QDM: magnetic bearing to station
QDR: magnetic bearing from station


texts: What's the difference between the "100 above" and "100" GPWS above callout?

texts: Not all aircraft have both; this one does and can be heard at 1:12:


texts: Why doesn't condensation form on the inside of airliner windows?

texts: If outside the aircraft is pretty cold and inside the cabin the air temperature is different, why don't the windows become fogged up on the inside?


texts: Does a headwind affect the climb gradient?

texts:
When studying for my German PPL exam, I came across this question:

For those that do not speak German I'll try to translate the question, but bear with me as it is kinda picky what I'm trying to get across here:

  During flight on a straight track with constant speed

  headwind will increase the gradient of climb
  headwind will decrease the gradient of climb
  headwind will increase the distance needed to descent 50m
  headwind does not affect the gradient of climb at all

As you can see answer 4 is supposed to be the correct one. I disagree, so I started searching for a reason, yet I couldn't find anything useful. Let me explain my train of thoughts:

I didn't really know the "gradient of climb", I always used the two terms "angle of climb" and "rate of climb". Thus I'm trying to figure out which one the gradient of climb is. Common sense makes me think it is the same as the angle of climb (gradient does just sound like an angle). This opinion is supported by SIDs, which have a PDG (Procedure Design Gradient) that is given in percent, just like the gradient of climb.

Assuming the gradient of climb is indeed the same as the angle of climb, the only way for the "correct" answer to be confirmed is by taking the distance traveled during the climb relative to the air, not to the ground (angle of climb is defined as the height gained divided by the horizontal distance traveled in a certain amount of time). This would mean that it is used with IAS, rather than GS, which in my opinion absolutely makes no sense ("Hey look, that mountain is 10NM away, we are climbing with 600 ft/min. and going 100 KIAS and need 3500ft more to go over the top, we're all good!" - Well, add a tailwind of 25kts, the pilot would still think he's good to go but it'd result in CFIT...).

The question I have is: How is answer 4 the correct one?


texts: In the Philippines' Civil Aviation Regulation Part 7, what does this part mean?

texts:
In the Philippines' Civil Aviation Regulation Part 7 it says

  individual certificate of airworthiness of the first production aircraft under the type certificate

I want to know what does "first production aircraft under the type certificate" means.


texts: Is it possible to estimate the location of aerodynamic center without experimental moment data?

texts:
In airfoils, the aerodynamic center is usually found close to the quarter chord point, but for quick calculations, we assume it lies on the quarter chord.

What I am looking for, is if there is any way to find a rough estimate as to where the aerodynamic center is actually located on a tested airfoil - given only lift and drag data.

The tested airfoil is mounted on the sting on its quarter-chord point, which sits on top of a force transducer. The angle of attack is varied throughout the test.


texts: What's a normal response delay for a paragliding vario?

texts:
I'm a paragliding pilot with P4 licence and I've purchased a 2nd-hand FLYMASTER B1NAV flight instrument for XC flights – mainly for logging the flights (route, distance, max. speed etc). It is an Altimeter-Variometer-GPS combo. As you know, these devices warn the pilot with beeps during climbing and sinking.
I'm using the device for a couple of months but I recently noticed an interesting thing: When I enter the thermal I first feel the climb with my harness and risers. But the device starts to beep with a delay of 1-2 seconds.
Is this normal?
I know it's an old and discontinued product. I've looked into its manual, but couldn't find any info about the delay. I don't want to rate this device as "broken", but I cannot be sure.


texts: Can an ARINC 429 controller set to receive messages on high-speed (100kHz) see 12.5kHz messages?

texts:
I am working with an ARINC 429 controller which is currently set to receive messages at 100kHz. When the transmission line sends messages that are 12.5kHz (standard ARINC 429 low speed) the controller can see them.

Is this normal for an ARINC 429 controller?


texts: I had a discussion and I'm curious on an experienced pilots knowledge.  When taking off, let's say from telluride. You have a tailwind, but when you get off the ground you experience and windshear that turns into a headwind dramatically. What are the hurdles you'll face? At telluride it says to only land and take off on certain runways, so I know this could possibly happen. Also would the lift generated from the sudden increase in headwind cause the AOA to start increasing without you pulling back on the yoke???


texts: How do I get an FAA CPL from an EASA PPL?

texts:
Im looking into getting a PPL, but feel I need some more information since there are a lot of hours involved so I need to expand my idea of the different possibilities. I am from Sweden but work and plan to do the PPL in Italy, and as I understand it there will be no problem getting a PPL in Italy/Tuscany ( anyone heard of the Lucca Areo Flight School ? ) since I can get a PPL anywhere in Europe.

The plan is to move to the States in approx 2-2 1/2  years from now. There I will need to apply for an FAA PPL but will it be possible to continue on to the CPL in the US as a foreigner ?

As I understood from reading the threads I would need a PPL anyhow to do the CPL, and as I'm not 100% sure I'll be doing the CPL, is a step-by-step way preferable?


texts: How to maintain straight and level flight after a climb?

texts:
I'm new to flying and I have this question.

Suppose I'm ascending to 2000 ft. at 67 kts and 2450 RPM. When I reach 2000 ft. maybe the plane wants to keep going up, even after I lower the RPM TO 2200, for example.

How do I make the plane flight straight and level at 2000 ft? With the trim and keeping 2200 RPM, or lowering the RPM to, for example, 2100?


texts: How does ATC maintain separation between aircraft flying at different speeds?

texts:
How are collisions avoided when 2 aircraft are flying same altitude and same direction but have different speed characteristics.

Example a B737 and an ATR are both flying at 25000 feet. 737 will cruise at 850 Km/h whereas the ATR will cruise at 550 Km/h and the 737 is approaching from behind.

How is this type of situation handled by the pilots and ATC?

My question is specific to airliners as I have seen from websites like flightradar there are thousands of planes flying at any given moment and was wondering how this problem is handled.


texts:
What are the advantages/disadvantages of an autobrake system? In particular I am interested in the Fokker 100 system.

Have any studies been done for the F100 autobrakes and the affects that this system has on the landing gears?


texts: What is an airliner's "green dot speed", and how does it vary with weight, and why?

texts:
A related question told us, quoting from an Airbus performance manual,

  Green dot speed (minimum gradient) is a function of weight.

Comments under the question stated that the "green dot speed" increased as weight increased.

So-- what is "green dot" speed?  Does it reference some fixed, optimal angle-of-attack?  Perhaps the one that gives the best L/D ratio (glide ratio)?  If so, it would obviously increase with weight, generally being proportional to the square root of the wing loading.  If this interpretation of how green dot speed varies with weight is not the correct one, then what is?


texts: Would the Concorde have been better off using a tailed delta wing?

texts:
In one of the answers to this question about the Concorde's lack of high-lift devices on its wings, it was pointed out that the Concorde, using a tailless delta wing, wouldn't have been able to use flaps, since there was no horizontal tail aft of the wing to counteract the downward pitching moment that would result from deploying flaps.
On the other hand, a tailed-delta configuration (a delta wing with a conventional tail mounted aft of the wing) would have been able to use flaps, as it would have had a separate elevator further aft with the ability to counteract the flap-generated pitching moment.  A good example of this would be the design for the Boeing 2707-300, which was to use a tailled-delta configuration and would have had some rather impressive flaps, but was cancelled in 1971 before even the two prototypes had been completed.
Given that it would have allowed the inclusion of flaps, would a tailed-delta configuration have been a better choice for the Concorde than the tailless delta they ultimately went with?
Edit: Better in that it would have greatly increased the Concorde's subsonic efficiency and allowed lower-speed (and thus less potentially-tyre-explodey*) takeoffs.
Quoth the linked question:

...The lack of high-lift devices considerably reduced lift at low speeds, requiring the Concorde to take off and land at higher speeds and angles of attack than if it had been equipped with flaps and slats. As well as greatly increasing drag (and thus fuel consumption) during takeoff and landing, this greatly increased the force carried by the main landing gear and the speed at which its tyres had to spin; as a result, if and when a tyre blew out (due to, for instance, a piece of debris left by the previous airplane to use the runway), the results would be much worse than with a tyre blowout on a subsonic airliner.
...[The addition of high-lift devices], along with slightly larger wings and more powerful engines, would have allowed the Concorde B to dispense with afterburners, considerably increasing its fuel efficiency and range.

* It happened a lot before the fatal accident.


texts: What is this star shaped symbol on the tarmac?

texts: This symbol is on the tarmac at Ramona, CA airport.  I've seen it at other small GA airports from Google Earth but I don't know what it is.  Can someone please explain?


texts: At what altitude does a wing become useless?

texts:
At what speed or altitude does an aircraft become more efficient as a rocket then a plane using thrust vectoring instead of the wings to steer? At what altitude did the flight control surfaces of the Space Shuttle become useful again or X-37B is still useful?

Source: http://www.xairforces.net/newsd.asp?newsid=817&newst=7#.XCbNY7hhrwc

Related: https://space.stackexchange.com/questions/33152/could-rockets-launched-from-the-ground-use-wings-in-the-stages

Is GOCE a satellite or aircraft?


texts: How do airplane "life jackets" compare to marine life jackets?

texts:
I have recently taken up boating in addition to being a pilot, and that experience has given me a better understanding of marine life jackets, also called "personal floatation devices (PFDs)". For boats there are four different types of life jackets, Type I, II, III, and IV, with Type I being the best.

On my boat I typically wear an offshore inflatable life jacket which qualifies as a Type II and as backup I usually have a Type I sitting or hanging in the cabin where it can be easily reached. These are big, strong, bulky things. By comparison the "life jackets" I see stewardesses wear when they do the monotonous lecture at the beginning of the flight seem to be extremely small and flimsy. How do these things compare to marine life jackets?

Marine inflatable on the left, airline inflatable on the right.


texts: Why is this unit attached to the main landing gear not a common unit for towing or pushback?

texts:
Less loading is applied to the fuselage with this method compared to towing or the towbarless way. Why is it not really common?

I'd like to detail this. There's my point, wouldn't it reduce cycles of loading to the fuselage, less fatigue resulted. Then we can eliminate shear pin & speed limit such stuff, doesn't it ?

In my opinion. For safety. This is much safe then the towing method.


texts: What is the unit for the oil quantity display in the Airbus A320 ECAM?

texts: Is this image showing 18.5 liters or quart of engine oil?


texts:
If I'm going on holiday with my family on an airliner such as one of the ones listed on this page, then where is the safest place to sit?

The answers to this question seem to imply that the seats at the rear of the plane would be safer:
Why are flight recorders generally located in the tail?
but of course I can think of quite a few things which might make it different for passengers versus the flight recorder.

I realise that flying is statistically a lot safer than driving, so I don't need to be told not to worry about safety - I'm not worrying, I'm just interested in the difference in safety between different seats in the airliner. Because if I get a choice of seats then (ceteris paribus) I can't see any reason not to choose the safer ones.

I'm guessing it might be affected by things like proximity to the exits, and so might be different in different models of airliner. If that's the case then can you tell me what factors affect the safety of each seat? E.g. is it more important to be close to an exit or to be further back in the plane? What should I look for?

Is it different on long-haul versus short-haul? Or are there other differences in the type of flight (and therefore the more typical type of accident) which change the 'safest place to sit'?

A few articles I've found on the topic:
 - Popular Mechanics, 2007 (statistical review: back is safest)
 - Discovery / Channel 4, 2013 (one-off crash experiment: back is safest)
 - BBC, 2014 (expert opinion: no safest place)
 - CAA, 2006 (statistical review of evacuations: exit rows and adjoining rows are safest)


texts: How to start deriving longitudinal equations of motion for an aircraft?

texts:
I hope this is a relevant place for me to ask a math question regarding aircraft design.

I am trying to understand how one would implement a controller to control the pitch angle of an airplane for a small exercise. I understand the control part and its implementation. What I do not grasp is how one acquires the longitudinal equations of motions (which are then used for the control part) which serves as the starting point. What is the starting point or what are the principles used to derive these equations? If I know how to derive these equations for a very simple case, then I know I have to linearize the equations and then apply control theory to it.

For example, how are the left and right hand sides of eq. 4.70 from pp. 164 of the following book book is derived?

I will appreciate a simple explanation of the above case.

Edit:

I am attaching two screen shots of two sets of equations from two sources. Links to the books are included below. Both sources state these are longitudinal equations of motion although their general form differ from each other.
I think I got to understand one point: these equations were derived considering translation motion on the x and z planes and rotation about the y axis (so stated in the first book) Thereafter, I don't understand the procedure.

1st set of equations from book 1:

second set of equations from source 2:

    book1: pg. 164 of Morris, Introduction to Aircraft Flight Mechanics: Performance, Static Stability

    source 2: pg 3 of this online note


texts: How do helicopter pilots practice auto rotation?

texts:
How do helicopter pilots practice auto rotation, and specifically, the landing phase?

Timing the flare as ground is approaching seems critical to a successful auto rotation landing. Yet I can't figure out how this can be practiced safely.


texts: Can foreign pilots get an FAA ATPL and work for a US-based commercial airline?

texts: Could a non-US citizen come to the US, receive flight training, earn an FAA CPL and be hired by a US-flagged airline? Are there any specific rules regarding the employment of foreigners as pilots for a US-based commercial airline? For the sake of example, an Iranian flying for a US-flagged carrier?


texts: Aircraft wing stress design for 4 engine aircraft

texts: Can anyone tell me how aircraft wings are designed for mounting the engines. My area of self study is a typical engine on the A380 weighs 8000kgs and it’s weight is forward of the wing. As the wing stays the same angle of attack no matter whether the engine is installed, under power or at idle I cannot understand why there is no turning force on the wing. With this 8000kgs weight hanging out on the outboard engine where the wing is thinnest then why does it not have a twisting effect on the wing. I can understand how the wing can be stressed to allow for when an engine is installed but if you look at the wing profile it’s unchanged whether the engine is mounted or not.


texts: Did the Space Shuttle boat tail used in the transport configuration save fuel?

texts:
During the testing phase as well as during transport of the Space Shuttle on top of a 747, a boat tail was used:

Source

Here I found that this was mainly to reduce the turbulence that would strike the tail of the 747, thus increasing yaw authority.

However, I can also imagine that the boat tail would reduce the base drag of the Space Shuttle, thereby reducing the fuel penalty of carrying the Space shuttle.

Is there any research that shows that the boat tail also reduced the drag, rather than just providing a cleaner flow to the vertical tail?


texts: What is this US Navy airplane seen at Westover AFB?

texts: This Navy aircraft was at Westover AFB in either 1987 or 1990. Type unknown.


texts: I have a European EASA license - what do I need to do to be allowed to fly in the US?

texts:
I own a PPL(A) license following JAR-FCL. Recently, this license has been exchanged for a European EASA license.
My training was on a motor glider (TMG), I do not have ratings for SEP, but TMG and Ultralight only.
In Germany I will have to fly a one hour test on an SEP to get the rating (plus about 5h for training).

What do I have to do in the US to get the rating?


texts: When does a passenger plane leave the cruising phase?

texts:
I have Flightradar24 data here. Which are in the following structure.

latitude    longitude   altitude    lastUpdate      velocity
....
49.34240    8.77556 19650   2018-11-01 09:38:09     415
49.35040    8.77490 19550   2018-11-01 09:38:15     414
49.35617    8.77442 19475   2018-11-01 09:38:20     414
49.37045    8.77308 19275   2018-11-01 09:38:24     412
49.38132    8.77208 19125   2018-11-01 09:38:30     411
49.38964    8.77132 19025   2018-11-01 09:38:34     410
49.39796    8.77054 18900   2018-11-01 09:38:39     409
....

This is data for a specific flight. My goal is to split the flight in two parts.

Pt 1: Airborne -> Exit cruise time / start Approach
Pt 2: Approach Start --> Touchdown

Well, I am not to deep into aviation. My naive approach would be:

  If the flying altitude has dropped continuously over the last k
  points, then the first timestamp is the approach start.

Now I ask myself, in what period of time does a passenger plane leave the cruising phase?

This is different from the pilot calculating the top of descent explained here: What is a rule of thumb for when to begin a descent?

How much ft altitude does an airplane usually lose when it comes out of the cruising phase? And how long does he need for that?

The background is that I want to understand how long a passenger plane usually takes to land at a specific airport from the approach phase. Optimally, I then see that on days when the airspace over the airport is fuller on other days, times, the approach phase takes much longer. Or do you think there are other factors playing an important role? Or is the approach not so correct. Maybe it would be better if I do not look from Approachphase, but from the time where a certain radius was reached. 80km before arrival?


texts: Why doesn't F-15 have a protruded cone at its rear like what the Su-35 has?

texts:
Why doesn't F-15 have a protruded cone-like structure at its rear like what the Su-35 has?

Left one is Su-35. Right one is F-15.

This is Radar Warning Receiver.

Where is F-15's RWR?


texts:
The FAA gives one requirement for the autopilot in the following FAR...

  FAR §25.1329 Flight guidance system.

  (j) Following disengagement of the autopilot, a warning (visual
  and auditory) must be provided to each pilot and be timely and distinct from all other cockpit warnings.

Why is an auditory alarm necessary when the autopilot disengages?

Was there a particular accident where the pilots ignored visual warnings?


texts:
I noticed this recently on Google Earth located on the southwest corner of KLAX in Playa Del Ray, CA.

Upon examination, I'm guessing the facility is used by firefighting crews for practice putting out jet fuel fires on an aircraft on the ground.  I'd also venture a guess that the smaller fuselages to the right are probably used by the LAPD SWAT team, federal sky marshals or other LE organizations for doing anti-hijacking and other anti-terrorism training.

But what's with all the taxiway paint markings around the red fire aircraft?  Do airport paint crews go out there to test their equipment?


texts: What's this sound? - Dogfight between F14 & MiG23

texts:
The following video features real-life audio of a CAP "dogfight" between two F14 Tomcats and two Libyan MiG23's in 1989.

(YouTube uploader: TopGunMilitary)

The audio isn't the clearest but between 6.29 and 6.34 during the fight a electronic interference kind of sound can be heard.

I have heard similar noises to this in other videos cockpit videos, what is it? My current suspicion is that it is some kind of "jamming" signal from the F14's as I believe the pilots in the recordings talk about one of the MiG's firing a missile.

Any opinions would be more than welcome

EDIT:

This is another video displaying the same noise at 1.37:

(YouTube uploader: BongHitBrian)


texts: Carbureted Rotax engines have no mixture control, how do they handle less dense air?

texts: Rotax engines have no mixture control, yet they don't seem to have any more problems than other engines at altitude. How do they handle the lower air density in order to not get a too rich a mixture?


texts: Why was the Junkers Ju 87 not upgraded with a jet engine?

texts:
Given that the Stuka dive bomber was famous during ww2 for its dive bombing attack but as we all know it was easily shot down by enemy fighters because of its slow speed especially during the later war years when the Germans lost air- superiority.

A simple solution would be to replace the piston engine in the Stuka with a jet engine instead and the problem would be solved.

Why didn't the Germans thought of this solution?


texts: What is the most critical data to measure for a predictive maintenance model for a drone?

texts:
I'm looking at making a predictive maintenance model for a drone (quadcopter mainly but can include others)

I'm wondering what is the most common causes of failure due to "overflying". (not including crashes etc) and how I would quantitatively measure it.

eg. I've read that one mode of failure is rotor malfunction is one of the most common causes of faults and so I would therefore use a vibration sensor (positioned near the rotor?) to measure it.

Are there other common failure modes? And what data can we collect from a drone that would help mitigate those?

Any help much appreciated!!

Kindest regards

Jonathan


texts: What does the solid black star symbol on this VNC chart mean?

texts:
On the Canadian VNC there are symbols, the meaning of I can't quite figure out. In the Nanaimo aerodrome there are several "star" symbols. The unfilled one shows the location of the aerodrome beacon. What do the other solid black star symbols mean?

The one circled in red reads "S2 Fl R 209". Based on my knowledge of marine lights I thought that it could describe a red flashing light. The star symbol, being in an aerodrome could mean "limited hours" but even then, I'm not able to make sense of the rest of the description.

What does the solid black star and "S2 Fl R 209" mean?

EDIT: According to the CFS, the solid star is a hazard beacon light. Not sure how to decode the text.


texts: Is it possible to (electronically) disable an ejection seat?

texts:
I'm currently reading "2034: A Novel of the Next World War" and my question may have minor spoilers:
One part of the plot comes into motion, when a F35E (the E is probably fictional) is hacked and maneuvered into a hostile airspace. The pilot wants to escape the inoperable F35 by activating the ejection seat, however, the hacker also made the ejection seat inoperable.
Now I'm wondering if this would be possible. Can ejection seats be deactivated? And if yes, why? I wasn't able to find something about this, which may indicate, that this is a bad idea to begin with. I found this answer and I would conclude, that there are indeed systems which can manipulate the behavior of an ejection seat, but nothing about completely disabling it.


texts: Is it possible to disengage only one axis of a two-axis autopilot?

texts:
Take GFC700 for example, when autopilot (or flight director) engaged, the lateral mode falls into

ROL, HDG, GPS, VOR, VAPP, LOC, BC, ...

and the vertical model has to fall into

PIT, ALT, FLC, VS, VPATH, GS, GP, ...

When disengaged (or temporarily by CWS), a pilot has to hand-fly both axes.

I am wondering if this is universal across all autopilot systems. Is there any autopilot that I may engage one axis and hand-flying the other. e.g. The autopilot only holds altitude and I may roll the yoke without any counter pressure. Are there regulations or purely from technical consideration?


texts: What is the difference between a MEL, MMEL, KOEL and Equipment List?

texts:
When we are determining what equipment must be operational for an aircraft to be considered airworthy we are presented with different kinds of equipment that could be installed on the airplane.

What is the difference between these different types of equipment lists?

Minimum Equipment List (MEL)
Master Minimum Equipment List (MMEL)
Kinds of Operation Equipment List (KOEL)
Equipment list

I would like to have answers for all the different aviation authorities.  US, EASA, Canadian, etc.


texts: How can using split throttles help when landing twins in crosswinds?

texts:
In General Aviation light twins, when landing in heavy crosswinds, what are some considerations to using asymmetric (or Split) throttles to induce a sideslip, to align the fuselage with  the ground track and the runway centerline instead of rudder?

I was told that this technique allows the aircraft to track down the runway centerlines with fuselage aligned with the runway without as much bank angle into the crosswind as would be required with symmetric thrust using cross-controlled rudder and opposite aileron alone.

I was thinking that the need for bank into the crosswind is due to the  need to compensate for the sideslip force (from the yaw due to downwind rudder) which would otherwise (without the bank) turn the aircraft downwind.

But it seems to me that using asymmetric thrust to induce the same sideslip would produce the same tendency to turn if the wings were not banked into the crosswind to compensate. Why not??


texts: Is LHV or HHV used for calculating the thrust of a jet engine?

texts:
Lower and Higher Heat Values (LHV or HHV) seem to have multiple definitions based on things I can't figure out.

What I want to know is, which one is appropriate to use for calculating the thrust from a jet engine? I'm thinking of large commercial turbofan engines like on the 747 or A380.

Also, since water vapor seems to have something to do with it, what about jet engines that run on hydrogen like the experimental Tu-155? Should we use LHV or HHV to calculate thrust in those engines?


texts: How do the vortex created by wing tips affects the lift?

texts: I’ve been reading about how improve the aircraft performance and I found that for low aspect ratios, the vortex created by the wing tips decrease the lift generated by the wings. Why is this happening?


texts: Does the dihedral effect happen during coordinated flight?

texts:
I have researched some about dihedral effect due to a question that I had, and I discovered that my question is essentially already answered, here and here, collectively.

This has led me to a new question because the information talks about slips.

If an airplane is flown in perfect coordination during a turn, does the dihedral effect still work to level the wings?


texts: Can hood time in a glider be logged as simulated instrument time for FAA IR purposes?

texts: I need to build my simulated instrument time toward IR. Can flying under the hood in a glider (with an instructor/safety pilot...) be legally counted as simulated instrument time in the same way would be the case had it been an ASEL?


texts: Is it practical to integrate turbofan or ramjet engines into an airliner wing?

texts:
The de Havilland Comet had turbojet engines integrated into its wings, such that its nacelles were mostly flush with the wings like so:

(wikimedia.org)

I recognize that turbofan engines are significantly larger in diameter than most turbojets, making the Comet's arrangement impractical for most modern airliners, but would it still be possible to integrate the engine nacelle with, say, the bottom of a wing while maintaining good aerodynamic characteristics on the wing? Would ramjet engines, owing to their lower profile, be more practical to integrate into a wing than turbofans?


texts: Has anyone successfully solo'd a helicopter with no actual flight experience?

texts: Especially at low speed, such as during takeoff, while hovering, and while landing, helicopters are famously difficult (impossible) to control for someone with no experience. Is there a documented instance of any person ever successfully taking off, hovering, and landing a helicopter with no actual flight experience? It must all be in one flight, first time--someone teaching themselves over multiple short flights / hours does not count.  Simulator use is OK and does not count as actual flight experience for the purposes of this question.


texts: Can IATA code for an airport be more or less than 3 letters?

texts: I got an exercise where IATA codes are involved - exercise's specification says those codes can be 2-4 letters. After a few minutes of research I see that those codes should be 3 letters, so can IATA code for an airport be more or less than 3 letters?


texts: How long can a commercial airliner fly at 90deg roll?

texts: For how long can a commercial airliner fly at a 90deg roll angle ? Or can it at all ?


texts:
Is there a place where past METARs are logged?

Suppose I want all the METAR for a given airport from October 1st to October 15th 2015. Where can I find them?

If it matters, I'm looking in particular for METARs from French airports.


texts: Does EASA (or other regional/national aviation safety authority) have a confidential "close-call" reporting system?

texts:
Not being a pilot, learned about the ASRS from this site. Have any aviation safety authorities in other countries attempted to emulate the ASRS and to what degree was it successful? After all it was introduced in 1976, which is quite a while ago.

I'm mostly interested in European airspace, although examples from other countries/regions are welcome.


texts: Would installing 6 engines on an Airbus A380 and or Boeing 747-800 achieve a shorter take off distance?  Would that result in excessive acceleration and harmful or uncomfortable G-forces? Would the extra thrust and leverage exert excessive force on the wings?  How about braking,would the braking be shorter if all engines were fitted with thrust reversers


texts: Where can I find nice animations of flutter?

texts:
Where can I find nice flutter animations/videos (other than YouTube) to add to a presentation without violating Copyright regulations ? It can either be for wings as well as blade arrays.

Are you aware of any OpenSource database on this topic ?


texts:
Is it better to shut down the engine(s) or leave it (them) running when a gear up landing is imminent?

I noticed that the pilot in this video chose to shut down his engine before touching down during a  gear up emergency landing.  However, in Pilot Operating Handbooks, the recommendations seem to be mixed.  For example, the Cessna 210 POH, Page 3-11 says:

  Touchdown -- SLIGHTLY TAIL LOW.
  Mixture - - IDLE CUT-OFF.
  Ignition Switch -- OFF.
  Fuel On-Off Valve -- OFF (pull out).

On the other hand, the POH for the Piper Arrow III PA28R-201, Page 3-14 recommends shutting down the engine before touching down:

  3.lSb Gear Up Emergency Landing (3.Sd)
  When committed to a gear up landing, CLOSE the throttle, move the
  mixture to idle cut-off, and shut OFF the ignition, battery master (BATT
  MASTR), and alternator(ALTR) switches.Turn OFF the fuel selector valve.
  Seat belts and shoulder harness should be tightened. Touchdown should
  normally be made at the lowest possible airspeed with full flaps.

What is the reason for this variation?  Is there some advantage to touching down one way vs. the other?

I've have noticed this question:

  How to execute a gear up landing on aircraft with low propeller?

However, I do not believe this question duplicates that one. While consideration of the propeller would be one factor in deciding whether or not to shut down the engine, it certainly would NOT be the only one.


texts: How many flying mileage a pilot should have per year in order to keep his licence valid?

texts:
Please let me know if possible
Thank you very much


texts: Is there any free source for current airline schedule data?

texts:
I am looking for a free database with complete and accurate airline schedules, especially for major European carriers.

I know there is https://openflights.org/data.html but I find the accuracy of the data very low or at least heavily outdated.

Can you point me to some other, free sources?
It can even be a website one could copy content from, not necessarily a csv or an API.

This is for academic use only. Maybe some paid sources have other policy for non commercial use?


texts: What is the difference between ICAO Annexes and Documents?

texts:
I have gone through many ICAO and aviation related sites, but I still can not understand the basic difference between annexes and docs.

What is it?


texts: Why did the RAAF procure the F/A-18 despite being purpose-built for carriers?

texts: Why did the Royal Australian Air Force (and others) procure the F/A-18 despite being purpose-built for carriers?


texts: Is the waves and signal dangerous for human at the airports?

texts: Waved like VHF , UHF and other themes like radio or something ....


texts:
Leading Edge Root Extensions were first used in Northrop F-5A/B Freedom Fighter, which first flew in 1959. After that, many fighter air-crafts have used it, some of which are mentioned after the question. The reason behind using such extension is delay of stall at very high angles of attack. How does the use of Leading Edge Root Extension help in increasing stall angle?

Northrop F-5A/B Freedom Fighter

author unknown, public domain (source)

Sukhoi Su-27

photo by Dmitriy Pichugin, GFDL 1.2 (source)

McDonnell Douglas F/A-18 Hornet

photo by LCPL John McGarity, USMC, public domain (source)


texts: Why are some US STAR fixes/waypoints included in FAA's legacy files but not in FAA's published STAR procedures?

texts:
I have noticed that some US STAR procedures include (slightly) different number of waypoints, depending on which source material is consulted. Take for example the CAMRN4 STAR and its corresponding description from the legacy files provided by FAA. In the legacy files, the reporting point GAMBY is mentioned between KARRS and CAMRN, whereas in the published information it is omitted.

S0095  NW N3905438W07448012SIE     SIE.CAMRN4   CAMRN FOUR
S0095  R  N3924521W07427171BOTON K6   S0095  R  N3934583W07416141HOGGS
K6
S0095  R  N3940336W07410055PANZE K6
S0095  R  N3950271W07359096KARRS K6
S0095  R  N4000222W07352083GAMBY K6
S0095  R  N4001023W07351398CAMRN K6
S0095  AA N4043436W07324483FRG
S0095  AA N4038237W07346433JFK

Is there a reason for this or have I misunderstood something?


texts: How should I log total hours flown in different countries?

texts:
Let's say you have an EASA-style logbook with European flight time, and then, you start flying in the USA, so you buy an FAA-style logbook and begin logging hours for your flights in the USA.

I don't think it is a good practice to mix foreign hours, since if both logbooks are still open you can have inaccuracies and inconsistencies in the transferred hours.

The question is: is it mandatory to bring your flying hours from the European logbook to the "AMOUNT FORWARD" section in the American logbook, or is it optional?

What is a good practice if you have multiple foreign logbooks?


texts: Why are civilians not allowed to fly demilitarized US fighter jets?

texts: I have seen it is possible to fly demilitarized Russian fighter jets in the US. Why is it impossible to fly American demilitarized fighter jets?


texts: Can I choose whether hobbyist or Part 107 rules are more advantageous when flying a UAV for fun?

texts:
According to the FAA's UAS getting started page, if I'm flying a drone for fun within a 5 statute mile radius of an airport, I need to contact the airport and any air traffic control tower before flying. As a Part 107 pilot, I can fly a drone in class G airspace up to 400 ft AGL (or over a structure) without having to contact anyone.

I have a current Part 107 remote pilot license. To me, this makes my ability to fly a drone more flexible.

If I want to fly for fun within 5 miles of an airport and the airspace is class G, I can decide I'm flying as a Part 107 remote pilot and then I don't have to contact ATC or the airport.
If I want to fly for fun within a surface non-class-G area, I can decide that I'm a flying as a hobbyist and contact ATC and the airport if I'm within the 5-mile airport radius, no airspace authorization necessary. This is a no-go if ATC says no, but otherwise a lot faster than applying to the FAA for a waiver to fly in controlled airspace.

In either case, I would ensure that I'm not anywhere near other air traffic, and that I fly safely.

When I'm flying for fun, can I pick and choose as to whether I fly as a hobbyist or a Part 107 pilot?


texts: Has this Google Maps imagery of 4 planes on a runway been tampered with?

texts:
The image below is of Google Maps (30 May 2018) of Amsterdam Schiphol's Aalsmeerbaan (36R).

It shows 4 planes on the runway and a fifth that's about to land. When you zoom in, all planes seem identical.

Has this image been tampered with or could there be an explanation for this?


texts: What is the tablet/application being used in this 737?

texts:
In this video (marker 2:32), you can see that the captain has a tablet mounted to his left with some sort of application open in it. It looks like an iPad (though I could be wrong), but what I'm mostly wondering is what that application is he has open, and what it's being used for?

Just to make peoples lives as bit easier, here's a screen cap from 2:32:


texts: How do airlines and airport exchange data?

texts:
I was just waiting for a flight, when the airline’s app sent me a push notification; my gate was changed to 12 in the same moment that the airport notified passengers about that the gate was changed to 15. So I started wondering how airlines and airports exchange this information?

Is it a central IT system? Run e.g. by IATA? Or do the alliances (star alliance etc) have central systems for that and they connect to airports? Or are there individual contracts between airlines and airports they go to? Does everyone use the same protocol / standard? Or is it more chaotically?

Additionally, flightradar24 recently started including gate & baggage belt information in their service – do they get it (likely) from the airports? Or do the airlines provide that data? Or how does that work?


texts: How does the Boeing 787's Cabin Air Compressor work？

texts: How does it work in normal, overheat and over-pressure conditions? What is the function of the variable diffuser actuator?


texts: Why don’t aircraft undergo contaminated-runway landing-distance and rejected-takeoff certification testing?

texts:
All aircraft have to undergo testing to determine how much runway they need in order to safely land and come to a stop, or to safely reject a takeoff.

They do not, however, have to undergo this testing on anything other than a perfectly clean, dry runway.  Instead, to get landing/RTO distances for contaminated runways, they multiply the dry-runway distance by some arbitrarily-determined factor (precisely which factor depends on what the runway is contaminated with - water, slush, ice, wet snow, dry snow, sand, Teflon, Jet A-1, ping-pong balls, whatevs), and then everyone hopes that this actually gives them enough of a margin for landing on contaminated runways.

Why not simply run landing-distance and rejected-takeoff certification tests on contaminated runways, as well as on dry runways, and directly measure how far it takes to stop on a wet or icy or whatever runway?


texts: How much does a drag chute system weight?

texts:
How much weight does a drag chute add to a plane?

Let's take the Tu-114 as an example. This plane has a loaded weight of 68.1 tons (I could not find a max landing weight figure). I could not find how much it's drag chute system weighs.

One purpose of this question is to compare it to thrust reverser systems. I have a separate question on that.


texts: On modern commercial airliners, how much of the flight could be fully taken care of by the auto pilot?

texts: If one wanted to, how large part of the flight could a modern commercial airliner do completely on its own? That is, if the pilot only was allowed to set things up and then leave the cockpit, from where (taxiing, take off, et cetera) and for how long would the airplane be able to handle things itself before things went out of hands?


texts: Why does Boeing 737 use 2 Inertial Reference Systems (IRS) and GPS?

texts:
According to this website the Boeing 737 aircraft use 2 IRS and 2 GPS: IRS L & IRS R. Why? Apparently they are totally independent of each other.

Could somebody explain a little bit why they need 2 separate GPS and 2 separate IRS?

Follow-up question: this same website states: "POS INIT is used to enter the aircraft position into the IRS's for alignment". What is meant by "alignment"?


texts: How much bigger could you realistically make the Antonov 225?

texts:
The Antonov 225 is the largest cargo plane in the world. But how much bigger could you REALISTICALLY make it if money wasn't a problem? Could it be say twice as wide? Carry twice the weight?

What materials and physics constraints are engineers up against? Is there a limit on today's materials to make a larger cargo hold or wings that could stand the bending moments of more engines and fuel in the wings? Would runways not be able to stand any extra weight than the 225 can already carry?


texts: Does the Boeing 737 MAX use electro-hydraulic actuators?

texts: I know the B747-8 uses electro-hydraulic actuators as does the 787, but what about the 737 MAX?


texts: Why don't all GA aircraft have yaw dampers?

texts: Why don't they have yaw dampers if they are always "suffering" from adverse yaw?


texts: Why barotitis, but only during descents and sometimes?

texts:
I experience barotitis only during SOME (not all) descents. During takeoffs, my ears feel different, but I feel no pain.

Is the cause pilot's skills, rate of descent, or aviational?


texts: Why do commercial pilots always engage reverse thrust even if it is not necessary?

texts:
Most of the time the usage of reverse thrust is not needed. I wonder if it's an authority (e.g. FAA) requirement to land safely.

Obviously, in bad weather conditions or when the runway is contaminated, the brakes might not work as effectively and thus R/T may be required to land safely. However, in most of other situations the aircraft can brake OK. Given that it would probably be more efficient to land without using R/T, why don't airlines routinely do so?


texts: Cessna 172 steering system and torque link purpose

texts:
How does the Cessna 172 steer while taxiing? Is it by using differential braking (braking one wheel at a time)?

Are there any connections between rudder or toe brake and nose landing gear related to steering?

What is the purpose of torque link in front of the oleo strut?

Does the nose wheel even turn?


texts: How do I say these situations, according to the runway's status?

texts:
There is an accident on the runway, for example, the aircraft is disabled on it, so, the runway is_________.
The runway is flooded, or there is oil spill on it, so, the runway is______.
Closed? Unserviceable?


texts: Are any agile (aerobatic) private jets produced?

texts:
If you look at the car industry there are luxury comfort brand like Rolls Royce or Bentley but super expensive racing cars are probably even more popular. They offer limited comfort, are not practical, almost not usable on normal roads, not very reliable and offer terrible fuel consumption. But still everybody dreams about them and a lot of companies try to manufacture.

Business jet can offer luxury and comfort but what to do if you want some excitement or performance? Why are there no jets with massive after burning engines with thrust bigger than weight that can climb straight up and do several G? Something like a cross-breed between a Gulfstream and an F15? Maybe it's good business case to manufacture something like this?


texts: Why are some modern military trainer aircraft so bulky?

texts:
Modern military trainer aircraft are a lot wider and bulkier than the previous generation. Especially the canopy looks oversized.

You can see this in the Boeing/Saab T-7 Red Hawk, Alenia Aermacchi M-346 Master (developed from the Yakovlev Yak-130) and Hongdu JL-10.
Development for these aircraft was started in the late 90s / early 2000s. All of these aircraft have a secondary light combat role. They are supersonic capable.
The seating position is staggered, probably so that both pilots (or student / instructor) have good visibility. This might explain the enlarged canopy. The wider cockpit is likely more comfortable and enables longer missions as well.
Additional avionics and increased fuel capacity may explain the overall increase in volume.
There seem to be some underlying reasons for these designs, but they are unclear to me.
What prompted these changes in the designs?


texts: What is a two- or three-mile base exactly?

texts:
I frequently hear the tower instruction

  Report a two mile base for runway 5

What is the intention of that instruction? I realize that under these circumstances that we're not looking for pinpoint precision, but still it would be nice to know.

For the record, I'm not asking what a base is (or the fact that "left" is implicit), but what two miles are we talking about? Two miles straight line distance from the threshold? A base to a two mile final? On the base leg, two miles from the centerline? (I'm pretty sure the last one isn't it, but hey, I've been wrong before)


texts:
I'm trying to find a 1959 C172 tail number N7393T.
It was my grandfather's and the last registered record of it was near Glendale AZ.  It was deregistered in 2015 and I found out that since it cannot be reregistered for 5 years it may have a new tail number. Any tips on tracking and finding this plane would be helpful.


texts: What is the best route for my 18 year old son to become a pilot with a major airline?

texts: What is the cheapest and most effective way for my 18 year old son to become a commercial pilot with a major airline?


texts: How would fighter jets make contact with a previously hijacked aircraft?

texts: For example, a plane is hijacked but civilians regain control, they know how to change the plane's frequency but no procdeures - i.e. dont know guard frequencies. There are fighter jets alongside who do have contact with ATC. What could the jets/ATC do to let them know what frequency to use?


texts: What is the physical scale of the turbulence that affects large passenger planes?

texts:
What magnitude of displacement of air in turbulence conditions is large enough to affect (i.e. be noticeable in) an airliner?

Are there any minimum limits, so that even fiercely turbulent air below a certain displacement is not noticeable?


texts:
Right now (28 May 2020, 0910 UTC) this Partenavia P-68 is repeatedly flying, alternately, northbound and southbound over Rome, Italy, in regular straight paths about 45 km long, some 400 meters apart. Flightradar24 gives for it just the model (no callsign, not anything). Yesterday morning it was doing the same, for at least six or seven runs.

What might it be doing? Is this the same kind of flight as in this other question? I can't say, since the flight pattern is somewhat differen: for one, the parallel paths there are some 4-5 km apart, while in this case they are less than 0.5 km.


texts: Is skin friction also pressure drag looking at microscopic level?

texts:
Roughness in boudary layer is taller than height of air which is not moving ,feel oncoming airflow in boudary layer, at front side must be high pressure at rear low pressure etc,so net force is to the right,this is classical pressure drag for roughness "object"...
If roughness height is taller than height of air with zero velocity,than  visocus/skin friction is also pressure drag at microscopic level?


texts:
So it's been about a decade since I got my private pilot cert and almost as long since I got to fly. My map reading is a little rusty.

I'm trying to fly my drone at a local park and it's warning me that I'm in Class D airspace. I've marked on the map where the park is.

If I'm reading this correctly, then I should be in Class G airspace up to 700ft AGL

Am I missing something or is this probably just a bad GPS signal on start?

I'm not getting repeated warnings so I think it's a bad signal but I figured a prudent pilot would check.


texts: Are there any aircraft with powered landing gear?

texts:
My student asked me a question this morning.  It was:

  A car drives by turning its wheels against the Earth. An airplane taxis by rolling on its wheels while the engines push against the air.  Are there any airplanes that taxi by turning their wheels, like a car?

I assume the answer is no for reasons of weight, complexity, and so on, but it's dangerous to say never.  Are there in fact any airplanes that fit her description?

Edits in response to comments:

She was thinking of "normal" airplanes, not airplane/car hybrids.
Peter Kämpf's link is the kind of thing she was thinking of.


texts: What would happen if the entire blade on a turbojet engine went supersonic?

texts: I have seen that when a blade tip goes supersonic, there are vibrations and lower efficiency. If the entirety of the blade was to go supersonic, would it be more efficient?


texts: What happens if I cross the ADIZ line without a flight plan and no clearance or contact with ATC?

texts:
I'm on a flight to/from the Caribbean on a single engine Cessna and I crossed the ADIZ (Air Defense Identification Zone) line.  I haven't filed a flight plan, I don't have clearance from ATC, and I'm not in contact with ATC.  I do have mode c transponder active on ALT and code is 1200 (VFR) and my altitude 6500 ft MSL.

The ATC would see the aircraft, its altitude, and its velocity.  Based on this flight data, ATC would most likely conclude this was an ignorant or lost pilot or lost drone, and no threat posed.  Have there been any instances where military or coast guard air craft were actually sent for  interception of such small and slow aircraft?  What are the statistics on this?  What would the fines and penalties be?  I'm assuming this would apply more when entering the US ADIZ than exiting.


texts: Is the maximum lift-drag ratio found at minimum drag?

texts:
Figure 10-5 of the FAA's Pilot's Handbook of Aeronautical Knowledge shows:

I didn't think $L/D_{MAX}$ coincided with $D_{MIN}$. Is this Figure accurate?


texts: What is a Flight Director, and how does it differ from Autopilot?


texts:
Do general aviation non-towered airports have to submit any types of logs to the FAA regarding total number of take-offs and landings in a given year?

I'm trying to figure out how busy a small airstrip near a property might be, I'm not having any luck getting the airstrip owner on the phone.

Thank you!


texts: What is the preferred way to slow down an airliner on a long runway?

texts:
EDIT: Another way to phrase the question is, given an extra long runway, does it make sense to substitute mechanical braking (which is the primary way to slow down in a typical situation) partially or completely with something else, to reduce brake wear / roll down the runway faster?

Consider an airliner landing on a very long runway (e.g. Boeing 737 landing on 12,000 feet+). The pilots are planning to vacate the runway near the end, so there is a lot of distance to spare.

Ignore noise procedures, and assume there is no traffic behind to suggest an early exit. What would be the preferred way to slow down the aircraft in this scenario?

Light application of reverse thrust only, no brakes?
Light application of brakes only, no reverse thrust?
Moderate braking until below a certain speed (e.g. 80 knots), then "coast" the airplane down the runway?

(This question addresses the primary means to slow down after a typical landing, while this question is about an idealistic case where there is plenty of braking capacity to spare.)


texts: Why are even drone flights prohibited due to the earthquakes near Mt Keilir, Iceland?

texts:
A "swarm" of over 20,000 earthquakes has rocked Iceland in the past 10 days — and it could spark a volcanic eruption links to this tweet by Almannavarnadeild ríkislögreglustjóra; The National Commissioner Of The Icelandic Police, Department of Civil Protection and Emergency Management:

Earlier today a tremor pulse was detected south of Mt Keilir, in the Reykjanes Peninsula, SW Iceland. No eruption has yet been detected but due to risks related to volcanic activity, all traffic near Keilir and Mt Fagradalsfjall is prohibited, including drone flights.

I can certainly understand large craft and especially those containing people, but why might Civil Protection and Emergency Management prohibit even drones that could be used to obtain scientific data on Mt. Keilir including changes in the mountain's appearance which might indicate an eruption was imminent?

Source


texts:
How do I read charts like these?

I don't know how to read it, or where to get started on IFR departures and approaches. I can talk to ATC and fly VFR, but I am still unable to fly IFR and would really like to start.

What else do I need to know to start on IFR?

What are fixes, airways, and routes? How do I plan a route myself?


texts:
I just saw a photo of the Pipistrel Apis motor-glider, and it got me wondering: How can it safely land with only 2 wheels total? To me it seems that falling to the side would be inevitable, and with wing fuel tanks, that could be terrible. In all the pictures, it's resting on (one of the) wingtips.

Are the wings/wingtips reinforced for landing & supporting the airplane on the ground?


texts: Are Dreamliner windscreens periodically replaced irrespective of damage?

texts: Does Boeing have a statute that commands that the windscreens are changed for new irrespective of no signs of damage or fatigue, and if so, what are the intervals, for safety reasons?


texts: What is the relation between geodesic airframe and geodesic curves?

texts:
That is certainly a beginner question but I cannot find the answer anywhere.

The Wikipedia page on geodesics says that they are the shortest path between two points on a geometric object (surface, manifold,...). It also  mentions geodesic airframes as a real-life application. However, the linked page about geodesic airframes does not seem to deal with geodesic curves. It is mostly about about a structure made by triangles or other polygons. A related question explaining why geodesic frames are no longer in use is answered only with this point of view.

Hence, my question: are geodesic frames related to geodesic curves? If yes, in what way?

My intuition is that geodesic curves are used to design the shape of the "perfect" frame (with respect to some constraints), and that the polygonal structure is an approximation of this perfect shape.


texts: Did Wolfgang Langewiesche ever change his mind about rudder pedals?

texts:
I get the feeling that if aviation was a religion and had a holy book, that book would be Stick and Rudder.  Mostly because it's often spoken of with great authority by people who have never read it.

Well, I'm reading it right now.  And let me tell you, Wolfgang has got some opinions.  Here's one of them, from Chapter 11.

  The important thing to understand about the rudder pedals is that they are unnecessary; like your wisdom teeth, they serve no very good purpose but can cause much trouble.  The airplane needs no rudder pedals.  It should have no rudder pedals.  In all probability it will have no rudder pedals 10 years hence.

I have to give him credit: he put his money where his mouth was.

However, the fact that it's now 2014 and rudder pedals are still very much in vogue makes me wonder:  Did Wolfgang Langewiesche ever change his mind about rudder pedals, or did he go to his grave defiant to the end?


texts: How to find runway Centerline spacing on airport diagrams?

texts: I know that airport diagrams show the exact position of airport runways in DMS (degrees, minutes, seconds) and therefore could use trigonometry to find how far apart runway centerlines are from adjacent parallels, but is there a more accurate way to find runway centerline spacing on these diagrams?


texts:
How are the 4-digit squawk codes assigned to individual flights?

This answer indicates that there should be a "correct" one. How does ATC know what is "correct" and what is "incorrect"?


texts: Can a Kline-Fogleman airfoil be used for engine turbines?

texts:
I am currently working on the Kline-Fogleman airfoil for NACA 23015 variant at Reynolds number 208800 with the configuration of the backward facing step of 50% thickness at 50% chord on the bottom surface of the airfoil. The KF airfoil gives higher L/D ratios for all pre-stall AOA and it also stalls at a slighty higher angle than conventional variant of the same series. The highest L/D value from Ansys Fluent was 22.45 at 9deg AOA as compared to conventional NACA 23015 at 9deg AOA being 19.74. I want to know if the KF variant of this airfoil profile can be used in turbine blades of a gas turbine engine and if it will produce higher power output or efficiency. Will it cause any problems due to turbulence and the number of blades and stages?

Also, are there any other applications of KF airfoils other than RC planes?


texts:
A few weeks ago I finally finished all of my USPA A license requirements. My instructor signed off the final things and even the card but forgot to put the stamp itself on the form.

I was about to send the form off to get my A license card but am hesitant without the stamp. Do I need the stamp to have it processed? More importantly, will I be able to use my paper form as the temporary A license without the stamp?

I normally wouldnt have an issue just going back to see him, but I am overseas for several months and really wanted to jump when I take leave.

I'm hoping to find an instructor or someone with personal experience with this... Thanks!


texts: How long have commercial aircraft been continuously in the sky?

texts:
In 2018, it's obvious that at any moment of the day, there is at least one (and in fact many) commercial aircraft in the sky. In 1908, this was not true.

Which was the last year there might have been a moment with no commercial aircraft in the sky? Please argue for your estimated year.


texts: What is this board given to world war II pilot?


texts:
Does the phrase ".78/280/250" have a standard meaning to an airline pilot, in the context of a long descent?

Specific context-- the table in this answer-- Is the descent performance of the PMDG 737-800 accurate?


texts: What is the exception applicable to basic VFR weather minimums in FAR 91.155?

texts:
Question applies to operating an Airplane.

The part 91 regulation regarding Basic VFR weather minimums in Class G airspace states (in the FAR 91.155 chart):

For aircraft other than helicopters:

Day, except as provided in 91.155(b): 1 statute mile and clear of clouds.

When I refer to 91.155 (b) I don't see any exceptions pertaining to airplanes operating in Class G airspace during the day.  The exception noted for airplanes only pertains to night time.

Is there some reason this regulation indicates that an exception does exist for daytime operations?


texts: What is the effect of the Load Factor on wing Structures?

texts:
I am quite confused with the definition of Load factor and how it applies to the wing structures of an aircraft.

For example, you have an Aircraft being subjected to a Load Factor of 2 and whose total mass is 5000kg and wings + fuel mass is 1500kg, and are asked to calculate the Inertia Loading of Said wings.

Would you multiply the weight of the wings by 2? Or does Load factor only affect the lift and not the weight?


texts: I was barely able to get a shot of this plane so it's not great quality. I was hoping someone could identify it for me. I've never seen one like this.


texts: Where to download a specific flight route before the flight?

texts:
Is it possible to download the flight route before the flight?

I'm interested in a table (or something similar) containing the following data:

Timestamp | Coordinates | Human readable location
————————-—+————————————-+—————————————————————————
                       ...

This would be quite helpful, so I can follow the airplane progress during the flight, without having internet connection.

Where can I get that from?


texts: How many aircraft can an ATCo control simultaneously, on procedural and radar service?

texts: Aispace is separated in sectors, and each one has its own frequency. What's the airspace capacity for procedural and radar services, for a single sector?


texts: What is the proper procedure after a bird strike in a single engine plane during takeoff?

texts:
First, let me set this up and then ask a general question.  I'm just trying to give some context as to why I'm asking.

I'm working on my private pilot license and was practicing with my PC simulator (X-plane) this weekend.  I was flying a Mooney m20j out of John Wayne (KSNA, which has two runways, 16R/1L 16L/1R).  I took off from 16R and at about 300AGL I encountered a bird strike and my engine died (though my windshield was intact).

I was just about at the end of the runway so I declared an emergency (yeah, I've been talking to myself...) and said I was going to turn the plane around and land on 1R (so, the parallel runway in the opposite direction.)  I was kind of panicking and had no idea what to do, this was just the first thing that sprang to mind.

I started the turn and quickly realized I was sliding sideways towards the ground, so I leveled out the plane a bit and ended up making a short approach on a taxiway, which I managed to land (though that may be down to the simulator being a bit forgiving and not me, really.)  So the plane survived...

So I've got two questions, the first a little specific (though I'll try to generalize it) and the second nice and general so it applies to a wider audience.

Is the process I described a good approach to a bird strike during take off?
In review, I feel I probably would have been better off just landing straight ahead on a road or open field, but I thought I'd ask.
What is the best way to deal with a bird strike or incident on takeoff that fails the engine?
I'm particularly interested in situations where the plane is about at the end of the runway - if it happens right as you take off you can just put it back down, and if you're much higher up you have a lot of options because you can glide for a while.  But right at the runways end, when you have very little altitude and no more runway...  What's the proper procedure?


texts: Why did the crashed TAM Airlines Flight 3054 veer off the runway only near the end?

texts:
For the accident, why did the aircraft veer off the runway near the end of the runway, instead of the moment it touched down (where the left engine went into reverse thrust and the right engine powered up to climb throttle)?
The aircraft managed to maintain a (relatively) straight path for most of the runway length. I thought asymmetrical thrust that significant would immediately send it off course


texts: What are "secondary precessional forces" that apply to boomerangs in flight?

texts:
note: This question is about the aerodynamics of boomerang flight and how it differs in microgravity environments. Some background information available here in Aviation SE: Are frisbees and boomerangs technically gliders? and in Space SE: How does one throw a boomerang in space? Does it return?

Professor and former astronaut Takao Doi is apparently the fourth person or the third person to throw a boomerang in space and the first to throw one specifically designed to work in microgravity.
The Space-Toys.com article says:

Finally, on March 18 2008, Japanese astronaut Takao Doi took a three bladed boomerang (supplied by Yasuhiro Togai) aboard the Space Shuttle Endeavor on a mission to install equipment on the International Space Station. The boomerang that he threw was the only space boomerang that was specifically designed for space flight. The photo of the boomerang that Maurizio supplied to me show that the blades are recessed to the rear, as you would find in a Fast Catch boomerang. This is the optimal design for a space boomerang because when the blades are shifted to the rear, the secondary precessional forces that cause a boomerang to lay over in flight are retarded. The Japanese team of Yasuhiro Togai and Takao Doi deserve credit for making and throwing the first [multibladed] boomerang that was optimized for use in microgravity conditions.

What exactly are the "secondary precessional forces" referred to in the article?

Takao Doi in a space three-point stance throwing a returning boomerang aboard the ISS:


texts: Why is the AWACS' rotodome located at the back and over the aircraft?

texts:
Browsing this website, I found this question dealing with torque due to the huge piece in motion, and its answers also speak of drag.

The rotodome is located above the aircraft and at the aft of the aircraft. For me it would have been logical to put this huge mass as closely as possible to the CG for stability reasons. For this aircraft, the CG is located close to the main gear, a little in front of them. When I look at an AWACS, I can see that the rotodome is located well behind the main gear.

AWACS image courtesy of airliners.net

Moreover, it seems logical to put the rotodome under the aircraft. Its mission is to observe airspace under the aircraft to detect hostiles flying low enough to avoid detection by ground radar. By mounting the rotodome above the fuselage, the aircraft's wings may disturb the radar mounted above them.

This position is also shared with other airborne radar such as the A-50 or the E-2C.


texts: Which Airbus models have exterior LED lights? (Taxi, Landing, Rotating Beacon)

texts: I know that the Boeing 737 MAX has LED'S. Which Airbus models also have LED external lighting?


texts: Why doesn't the plane accelerate/move forward when it's at rest, if the propeller is spinning?

texts:
I'm having difficulty seeing the difference between a stationary plane and a moving one.

When you start the engine in the C172, the blades on the prop are spinning - but the plane doesn't move at all.
When taxiing out, it feels like the forward motion is being provided by the wheels - like in a car.
When taking off, you can audibly hear the change with the throttle increases.
In cruise, the plane almost looks the same from the inside as when it's on the ground (i.e. prop spinning). Which is where the weird psychological block is for me - the plane feels stationary even though the horizon/backdrop is moving towards you, and i get that fear kick in that it could drop because there's not enough momentum.

I'm trying to understand what the propeller is doing in each of these stages: rest, taxi, take-off, and cruise - as well as how the plane is pushed forward with thrust, if it can just sit there and not move with the prop spinning away.

My question(s): what's happening with the engine, throttle, and propeller that provides the thrust, and/or forward momentum? Does the plane stay stationary when you turn the engine on because there isn't enough RPM to draw it forward, or will it automatically pull forward and the brakes are just being held on? Does the plane accelerate in proportion to the prop RPM? What's different with the prop when stationary, compared to when it's taxiing or taking off?


texts: Could the Boeing 747's 'hump' be improved aerodynamically?

texts: Couldn't the Boeing 747's aerodynamics be improved by extending the hump further back, or sloping it back more gently? Wouldn't this make it more aerodynamic and therefore fuel efficient and faster?


texts: Why does Beijing's new Daxing airport have so few gates?

texts:
There is a lot of press about the Daxing airport, touting that it will be one of the largest in the world in terms of passenger capacity. The images of the terminal build are indeed beautiful.

But when I look at this image, taken from Wikipedia, there doesn't seem to be a ton of gates:

I couldn't find an authoritative number of how many gates it will have, but this website says it will have about 80. This matches what I see in the image above.

By comparison, Ohare and Hartsfield–Jackson have about 190 gates, JFK 130 gates, Schiphol Airport 165.

Why is this? In the Beijing Capitol Airport right now, there are not enough gates, so when I land there, they have us deplane on the tarmac and take a bus to the terminal. Why didn't they build 200 gates if this is to be the largest airport, by passenger volume, in the world?


texts: By what scale is Latitude and longitude calculated on aircrafts?

texts:
If we travel by 1 metre on any side how much of longitude and latitude changes?

Since the flight is travelling so fast latitude and longitude changes quickly so how do they calibrate it?

PS:Is there any formula related to this?


texts: Will an airliner with a quieter cabin have a quieter cargo hold?

texts:
I am aware that this question is on the border of travel and aviation but nobody on the travel side of the fence seems to be able to answer it. Apologies if it is regarded as off-topic for this site.

The question and answers on Are cargo holds pressurised these days? provide some good info on pressure and temperature management in airliner cargo holds but none on noise management.

As part of the process of emigrating my wife and I will be taking our cats with us on an 11 hour flight. I have travelled the route regularly on both A380 and Boeing 747 services. My experience is that the passenger cabin of the A380 is significantly quieter.

Will the experience for the animals in the hold be similarly quieter, or is noise in the passenger cabin separately and specifically managed?


texts: Is there any difference between "EMERGENCY LANDING" and "FORCED LANDING"?

texts: Emergency landings and/or forced landings are stressful situations, but talking about meanings, are they the same, please?


texts: Is there a way for an aircraft to tell a ground station when the gear is down?

texts: Is there any way that someone on the ground can be informed if the landing gear is down? It could be an ACARS message sent to the ground center, or a specific light (sequence) from the aircraft that someone can see visually, or something else. If there is nothing today, is there something that could work in future for all aircraft?


texts: What is the maximum crosswind component for large airliners?

texts: For smaller aircraft like Cessnas, the demonstrated crosswind component is something like 12 knots but they can land up to 20 to 25 knots. For bigger jets, such as the Boeing 737 and 777, what is the maximum crosswind component?


texts: Is Touring Motor Glider included in the term "aeroplanes"?

texts:
The EASA definition goes as follows:
‘Aeroplane’ means an engine-driven fixed-wing aircraft heavier than air, that is supported in flight by the
dynamic reaction of the air against its wings.
‘Aircraft’ means a machine that can derive support in the atmosphere from the reactions of the air other
than the reactions of the air against the earth’s surface.

To me a TMG could go under that definition but not sure though...
Basically I'd like to know whether the 15 hours that are needed to go from LAPL(a) -> PPL(a) can be done on TMG
https://www.caa.co.uk/General-aviation/Pilot-licences/EASA-requirements/PPL-SPL-BPL/PPL-(A)-requirements/


texts: Would a slower speed and lower altitude reduce fatal incidents?

texts:
If it became plausible to fly commercial aircraft much lower in the future (due to developments in technology and airway regulations permitting it), say at a standard height of 5,000ft, but with a slower speed - would that prevent / greatly reduce fatal incidents?

In other words, if an aircraft goes down at 5,000ft and 150mph, it's more likely to have survivaility vs 30,000ft at 500mph.


texts: How is the the turning error of an aircraft magnetic compass calculated?

texts: I have a major exam in school tomorrow and I still don't get how to get the turning error of an aircraft magnetic compass. For example, if given an initial heading of 120 degrees and final heading of the Northern and Southern hemisphere, how to calculate the overshoot and the level off? I know the UNOS and ONUS but still don't get the concept of it. Please help me.


texts: Does the FAA advise or require pilots to wear eyewear designed to protect them from lasers?

texts:
With several instances of pilots being subjected to laser lights being shone on them, I wonder if the FAA is actually doing something about it.

It's easier said than done to stop people on the ground from shining their laser lights. Maybe a preventive strategy is better. With a host of eyewear available which minimise the risk of laser light, I am curious as to what the FAA and other similar authorities are doing about it.


texts: To my knowledge, bypass air produces 80% of total thrust. But I don't understand to how it does that. By accelerating the air, by increasing the speed or increasing the pressure of the air? Is it doing this by Bernoulli's principle or something like that?


texts: last 747 flight path, was this hand flown? How was this communicated with ATC?

texts:
Elal's last 747 flight made this nice path of a 747, how was this done?
Could this be entered into the computer and flown? or was this hand flown

The path looks quite neat

Also what is the ATC procedure for such a maneuver?


texts: Do pilots ever intentionally takeoff or land downwind?

texts: Is there a reason a pilot would takeoff downwind or land downwind? Is it legal to do this?


texts: EASA Form 1 for LRU removed serviceable from Engine during Engine Shop-Visits

texts:
Is it allowable for an EASA 145 approved maintenance organisation of a commercial airline to remove and release a component as Serviceable with an EASA Form 1?
To make it more specific, is it allowable for an engine MRO to remove an LRU/component from an engine undergoing a shop-visit and then release it on an EASA Form 1 as Inspected/Tested stating that the component was removed after visual inspection (Block 12 remarks)?


texts: Why are FDRs and CVRs still two separate physical devices?

texts:
Given the histories of flight data recorders and cockpit voice recorders, I somewhat understand their origins as two separate physical devices. Given their separate tracks of development, regulatory requirements, and storage mechanisms, it stands to reason that they historically existed as two separate "things".

However, I'm under the impression that the vast majority of the commercial airliners operating today are utilizing solid state memory to store both flight data and cockpit voice recordings. Both devices share many similar requirements in regards to being capable of withstanding extreme heat, g-forces, impact resistance, submersion in water, etc. Both devices are equipped with underwater locator beacons. Even the bright orange color of both recorders are the same!

The Wikipedia article on flight recorders briefly mentions that "the FDR and CVR can be manufactured in one fireproof, shock proof, and waterproof container as a combined digital Cockpit Voice and Data Recorder (CVDR)". However, whenever I read about modern aviation accident investigations--1990s, 2000s, 2010s--investigators are always searching for and analyzing the two separate black boxes. I don't think I've ever heard of an accident that involved a single combined black box, so their usage still doesn't appear to be very widespread.

Why not? Since the only thing I can see that distinguishes a modern CVR from a modern FDR is the type of data being stored, why didn't the integration of these separate devices become the norm decades ago? The best explanation I can come up with is some sort of notion of redundancy, but this doesn't make sense if they're storing two separate sets of data.

Even if a single combined recorder was deemed to be too risky, how hard could it be to just record both sets of data on two identical recorders? At least that way, there's true redundancy being maintained. The fact that "flight data" and "cockpit voice" data are still being stored on two separate physical devices seems rather absurd in this day and age.

It seems about as logical as buying and maintaining two separate external hard drives--one for my music collection, one for my movie collection. It'd be closer to life in the early 90s, when I had a collection of VHS tapes and a collection of cassettes. But now that everything is digital, it makes sense (logically and financially) to just use one device to store both collections. Why isn't it the same with modern-day FDRs and CVRs?


texts: In what direction(s) is any debris typically ejected from a jet engine in the case of failure during flight?

texts:
Has there been evidence of ejected material striking the fuselage or other parts of an aircraft forward of the engine itself?

Which of the various forces acting on rotor blades dominates the trajectory of pieces in the case of a blade failure?

Other than rotor break-up, what kinds of engine malfunction typically cause component separation, and in what direction(s) is material ejected?


texts: Why don't airbus aircraft have raked wingtips?

texts: Most airbus aircraft have sharkfin winglets or blended winglets. Why is it that none of them have raked wingtips like the 777-300ER?


texts: Does it have to be a potential combat situation for a pilot flying on another's wing to be called a wingman. If two aircraft are being flown in formation to a destination simply for the purpose of transportation, would the term wingman be used?  Is wingman used in civilian aviation?


texts: What is the difference between a high bypass turbofan and a low bypass turbofan?

texts:
I see some questions on the site that talk about the relative positives and negatives of a high bypass turbofan (HB) vs a low bypass turbofan (LB).  But I don't see anything explaining what actually makes a turbofan engine HB or LB?  I assume it has to do with the ratio of air that is bypassing the compressor stages and just going through the fans.  But what ratio makes an engine HB v. LB?  And why was that ratio chosen?

Please note: I am not looking for usage cases, I am looking for differences in design specifications.


texts:
Presumably helicopters have landed and lifted off railroad flat cars.

Has an airplane ever been launched from a train?

(my artwork)

F-84 during project ZELL testing (info provided by jwenting)


texts: How many lives would be saved if the airlines turned all the seats around?

texts:
The psychology and history of forward-facing seats has been answered well already here. I ask instead about how bad it is that seats are forward-facing.

For context, I was looking through Wikipedia's list of airline flights that required gliding, and a surprising fraction of the 30 incidents listed were fatal to some, but not all, of those aboard (47%). Averaged across the 30 incidents we get that 25.1% of those aboard died (noting that this average is pretty unscientific, and is subject to sampling and coverage biases; it's still interesting). Even among just incidents with fatalities on average less than half of those aboard died! I generated a scatter plot of the incidents:

This data surprised me a lot! My layman's intuition says that emergency landings should be a lot more bimodal, with basically all landings either being gorgeous US Airways 1549 style happy endings, or blazing fireballs with no survivors, with some very rare exceptions. Based on this intuition, I always figured it was reasonable that passenger seats face forwards; I thought "rear-facing seats wouldn't help that much anyway, edge-cases where it would have made the difference will be the rare exception to the rule".

But is this really true? It seems that maybe many deaths on commercial flights are incidents in this intermediate region, although I don't have the expertise to evaluate if rear-facing seats would help with how people typically die in commercial airline accidents.

Question: As a really rough ballpark, how much safer would commercial airline flights be (averaged across all commercial flights globally) if the seats were rear-facing?


texts: Why are the positive points in a V-n diagram associated with pitch maneuvers?

texts:
For an aircraft with such flight envelope, the flight conditions in point A, C and D are associated with symmetrical pitch maneuvers. So, for the combination of loads factor n and speed V in each of those points represents a symmetrical pitch maneuver, in which there is a certain angle of attack and certain deflexion of the elevator, both different from zero - all other control surfaces wouldn't be deflected. That comes from reports from SAE aero design competition and from Structural Loads Analysis: Theory and Practice, Lomax

I understand the airplane can execute any maneuver so long it is inside the flight envelope, but why are the critical pitch maneuvers those "described" by points A, C and D whereas critical rolling or yawing maneuvers have clearer definitions* regarding the most extreme conditions related to those maneuvers?

*Here's an example from Lomax (nothing like that is said from symmetrical pitch maneuvers)

  Two types  of yawing maneuvers,  as  shown schematically  in  Fig.
  4.1,  must  be considered  for structural design...


texts: Can I get official recordings of ATC audio?

texts:
Is there a procedure in place to request a copy of the audio recording of a specific ATC position over a specific time interval?  How is the request made? What are the limitations of such a request?

For the purpose of this answer, consider that there would be a need for the audio from a controller, which may involve multiple frequencies as well as interphone communication with other controllers.  As such, internet resources that provide recordings of specific frequencies would not be adequate.


texts:
I just watched this video in which the avionics surprised me. It looks like a half Garmin G600, attached on his yoke.

What is that and is it permanently attached to the yoke or is it portable?
Could it be for aircraft that can not be retrofitted? Because there is also something to see what looks like a ADS-B-receiver to me:


texts: Why is this G-AIRMET's valid time earlier than its issued time?

texts: For this G-AIRMET map, why is the valid time earlier than the time it was issued?


texts: What mechanism or design aspect prevents jet blast from escaping the front of a Ramjet or scram jet?

texts:
Enormous air pressures result in the thrust of a Scram jet or ramjet engine, more so the pressure required to drive the aircraft forward at supersonic and hypersonic speeds.  Given that these engines are designed to function without a  fan which sucks air and at those speeds would prevent air from coming in too fast or going back where at came from post being heated.  What mechanism or design aspect prevents jet blast from escaping out the front of a Ramjet or scram jet, resulting in lost thrust and or perhaps negative thrust given that explosive pressure would drive air in any direction that would allow it to escape.

I'm also considering that the air entering the engine does not have that much pressure to prevent this cause if jet blast did exit out at the front, scram jets and ram jets would not be able to produce thrust


texts: What were the typical rotation and landing speeds of the X-29?

texts:
Looking online through all the available literature, I could not find the typical rotation ($V_r$), landing or even stall speed of the experimental forward swept wing X-29 aircraft.

I'm curious to know if the forward swept wing lowered the rotation and landing speeds over a standard F-5 on which the X-29 was based.

Does anyone know?


texts: Will 3D wing has smaller drag than 2D at same AoA and airflow speed?

texts:
We meassure lift and drag for 2D and 3D wing case,we use same airfoil at same AoA and same airflow speed for both case.
Wind tunnel can change test section walls width.

2D wing test:

So first we put airfoil in wind tunnel so walls touch arifoil tips(2D wing),at AoA=15degrees and airflow speed=20m/s  and meassure lift and drag..

3D wing test:

Now we increase walls width so airflow "act" like 3D wing in test section.We use same AoA=15 and same airflow speed (20m/s) over airfoil like in 2D wing- test.
note: AoA=15 is angle between chord line and freestream airflow not angle between chord line and effective airflow at 3D wing

Question is,what will be drag of 3D wing-test compare to 2D wing-test,smaller ,equal or larger?

My logic is that 3D airflow leakage on tips  will decrease overall pressure difference at wing ,so lift will be smaller than in 2D wing-test but drag will be also smaller than in 2D-test,because when you integrate smaller pressure difference over airfoil surface you will get smaller drag as well.

(BUT if we must have SAME LIFT IN BOTH TEST,than 3D wing test will have larger drag,because then we must increase AoA at 3D wing to compensate lift reduction caused by airflow leakage,so now  when we have increased AoA we also have larger drag..)

3D wing will have less drag,drag decrease when AoA decrease,3D wing "feel" effective AoA,so it fly at smaller "AoA" than 2D wing.

how blue-lift can be larger than red-lift,wing at AoA=10 can not produce larger lift than wing at AoA=20 ??


texts: How do banner tow planes coordinate with air traffic control?

texts:
I tried searching with terms I think were correct around the net, but no satisfying results.

I have seem many times small planes circling around when there is some special event going on. They have advertising banners trailing behind them. For busy airspaces like the San Francisco bay area where you just have to glance up to spot a plane, how does this work with ATC?

Do these planes have to stay under certain level that is not controlled by ATC or ATC just allocates them a block of area and declares it off limits for others?

Do they have to declare their intention of circling special event areas given the security concerns and large gathering of people?


texts: What is the flight time limitation for commercial air transport operation in Europe?

texts: What is the maximum hours of flight time that a pilot can work legally in Europe? (daily, monthly and yearly)


texts: How often are drop tanks actually dropped?

texts: I know drop tanks are used to extend the range on many fighter jets, but how often are they actually detached from the plane once empty? A lot of WWII movies and documentaries show tanks being dropped before entering combat, but I'm curious about more modern planes and non-combat conditions. Does the increased air resistance offset the cost of dropping the tank on say, a standard patrol, or are they landed and recovered with the plane and if so, are they re-used or simply scrapped?