texts: Why don't hyperbolic navigation transmitters on the surface (e.g. Loran-C) allow altitude measurement?

texts:
I have been reading the following article about radio navigation in general and GPS / GLONASS receiver design:

A homemade receiver for GPS & GLONASS satellites

in which the author states the following about hyperbolic radionavigation:

  Hyperbolic navigation systems were first implemented as ground-based navigation systems [...] Since the transmitters are located on the Earth's surface, the geometry of the problem does not allow a three-dimensional navigation. [...] To measure the altitude, one of the transmitters should be located above or below the user's receiver or at least out of the user's horizon plane.

I do not seem to be able to comprehend why this is the case. Even if the transmitters are located on the surface (e.g. Loran-C), the differences between reception times of signals from 4 transmitters would generate 3 rotational hyperboloids in 3D space, the intersection of which could be above (or below) surface.


texts: Has there been any research on plasma-producing planes?

texts:
Many years ago I read in an expository scientific journal[1] an article about what the future of high speed aviation could be. It said that there were studies on airplanes capable of "plasma-izing" the air in front of them to get better lift and better aerodynamics.

Did they dream this up? Was there real research and, if so, did anything come out of it?

I've tried searching online, but the only things I've found are a bit too technical for me. From what I've been able to understand they are about using plasma generation in place of the control surfaces thus reducing vortices on wings.

[1] (one of those publications aimed at the divulgation of science to everyday people, not just for scientists)


texts: What was the takeoff run distance of a Fw 200 Condor bomber/transport?

texts:
The Fw 200 Condor was a large plane of Germany during WW2. It was used in recon and bomber roles against convoys. Wikipedia lists several specs including max takeoff weight of 24.5 tons and 4 engines producing 895 kW each.

But I could not find takeoff run distance, neither there nor in google. I would like to know how long of a runway was needed for it.


texts: How can the Airbus A380 have such a high lift/drag with a relatively low aspect ratio wing?

texts: The Airbus A380 has a wing with aspect ratio between 7 and 8.  Reference here.  The lift to drag ratio is somewhere between 19 and 20, which is comparable to aircraft with higher aspect ratios and superior to aircraft with similar aspect ratios.  A reference to the lift/drag number is here.  How can the A380 achieve this?


texts:
I am trying to calculate estimated flight time accurately. I calculate the distance with the great-circle distance method. I have some specifications of the aircraft such as max speed, cruise speed, stall speed, rate of climb, takeoff over 50ft, takeoff ground run, landing over 50ft, landing ground.

I tried the most straightforward approach(distance/speed), but the result was not nice. How should I calculate the estimated flight time?


texts: How to find the static stall angle of attack for a given airfoil at given Re?

texts:
For vertical axis wind turbines applications

I'm wondering how one would find the static stall angle of an airfoil at a given Reynold number?

Is it just the critical angle of attach (AoA) where highest lift is achieved or some value beyond that?
Consider the given graph for NACA0012 (for the use of vertical axis wind turbines) at Re of $3\times 10^5$, what will be the static stall angle in this case?

I found some stuff here and there, yet, I couldn't figure out my issue.
The graphed data were taken from this Ref[i].

From Wikipedia:

  In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases. This occurs when the critical angle of attack of the foil is exceeded.

Other related questions: 1 and 2.

[i] Sheldahl, R.E. & Klimas, P.C., Aerodynamic characteristics of seven symmetrical
airfoil sections through 180-degree angle of attack for use in aerodynamic
analysis of vertical axis wind turbines , Albuquergue, NM: Sandia
National Laboratories, Report No.: SAND80-2114, 1980.


texts: How long does a non-ETOPS flight need to be able to fly in an one-engine-out situation?

texts:
Let's say that you're in a 737, mid-cruise in a non-ETOPS situation, and you lose one engine. Are there any FARs governing how long you need to be able to stay airborne? Or is all that's required the ability to continue safely and land at nearest appropriate airport? Are you required by any regulation to be able to fly for an X number of hours before landing?

I couldn't find anything in the FARs about this, only regulations regarding ETOPS and engine out climb. Just want to make sure I'm not missing anything. Thanks!


texts: Do airlines schedule departures based on average environmental conditions of departing airport?

texts:
I have noticed that at Dar es Salaam International (HTDA, Tanzania, Africa) all major airlines (namely KLM, Swiss, Emirates, Turkish) schedule their departures mostly at night starting from 10:00 PM local time onwards.

Besides the fact that they have to match their flights with ongoing connections, I was wondering if they do this because they fly here with big aircraft (A330-300, B777, B737-900ER) and the airport, even though being at sea level, has very high day temperatures throughout the year (30C and higher).

Maybe this helps during takeoff, which in hot conditions could be risky, especially if fully laden?


texts:
Slats can be extended automatically depending on dynamic air pressure. Fly-by-wire systems provide flight envelop protection when flaps/slats are extended but I cannot find any reference of fly-by-wire feature such as auto-retractation/extension of flaps/slats depending on angle of attack or air-speed.

Do systems to automatically retract/extend flaps depending on flight conditions (speed, angle of attack,dynamic pressure,...) exist?


texts: What does the XFR button on the Challenger 300's autopilot panel do?

texts: I'm new to aircraft and currently I'm learning the autopilot system of the Bombardier Challenger 300. I saw the "xfr" button but don't understand what it is for. Can someone explain this to me?


texts: Can the bleed air for deicing the wings of the aircraft be switched on and off for jumbos?

texts: Considering the large surface areas of the wings of the Boeing 747 and Airbus A380, can the bleed air for deicing the wings be switched on and off as needed and if so, is that automatic and where are the sensors to control this (on which parts and why).


texts: How did pilots maintain the Vomit Comet's parabolic trajectory?

texts:
How did the Vomit Comet maintain its free-fall trajectory?  Careful trimming?  Custom autopilot software?  Or just good stick and rudder technique?
Wikipedia, citing references but without substantiation, suggests manual control of at least the throttle. To use an automotive analogy, a trained pilot could correct for which direction the fuzzy dice are hanging from the rear view mirror, by playing the throttle and elevator and spoilers.  But even a legend like Bob Hoover might lose precision doing that dozens of times in a row.


texts: What control surfaces do I need to move to do a roll in a model aircraft?

texts:
Figured that this was the better site to ask than drone SE, but if I'm wrong just let me know.
I'm making a spitfire model and was just wondering how do I do a roll? I have elevator, rudder, and two connected ailerons.
What control surfaces do I move to do a roll?


texts: Is there any book like the "Stick and Rudder" about the helicopter?

texts: I have read the Stick and Rudder, that's really a classic book. Now I want to study the flight theory about helicopters, is there any book like this?


texts: Gas Venting Stations: What's The Big Deal?

texts:
On sectional charts you can see that, through various restrictions, regulators encourage pilots to avoid flying too close to Gas Venting Stations. These seem to be places where natural gas may occasionally be vented into the air (for example from pipelines). I have been unable to determine if the gas is preignited.

Is the principal risk from gas discharge that's being mitigated here:

aerodynamic
explosive/thermal
respiratory
a combination of the above?

Have incidents occurred relating to these risks?

You can find some talk of the risks online but it seems mainly to be in the form of "My mate told me...".


texts: What’s this vortex generator like thing below the wing?

texts:
In Barcelona’s El Prat Airport I saw some ceiling fans and noticed that they have on the lower part of the wings something that looks like a wingtip device or vortex generator.

As far as I understand vortex generators, they prevent the boundary later to detach / move the separation point. But that’s no issue below an airfoil, is it?


texts: Why would a passenger airliner be missing windows in the fuselage?

texts:
On many airplanes (you can take the A330 to make an example), the fuselage is not completely covered by windows. In some cases it is due to the presence of the lateral emergency exit, in some other cases I am not sure about the reason. Usually it's above the wings, so I made my idea but I want to know for sure the real reason!

In the linked video, for example, one windows is missing under the "R" of the "Garuda" logo in the fuselage.


texts: How can an international MRO apply for FAA approval?

texts:
I own a small maintenance, repair, and operations (MRO) shop in Indonesia. We are having trouble with our customers that required us to obtain FAA approval in order to get order from them.

I already tried to ask the Indonesian regulator to help us to obtain FAA approval, but no luck. FAA requires an MRO to maintain at least one N-registered aircraft, and we don't have any in here.

Does anyone have same experience? And how can we proceed?


texts: Why is there a drift value between the IRS position and the FMGC position present even after performing a full IRS alignment on the A320?

texts: I have noticed this many times across my company's fleet of A320's that is even after a full IRS alignment has been completed many a times there is still a drift value present between the FMGC position and the IRS position. Could any help explain as to how this happens ?


texts: What is the most cost effective way of combining an instrument and multi engine check ride?

texts: I have a single engine land commercial without an instrument rating. I am currently completing the instrument rating. Now if I need a single engine and multi engine commercial with instrument ratings, what would be the most cost effective way of going about this?


texts: Someone can explain how WEP (War Emergency Power) worked on the planes of the Second World War? And if it was really effective during a combat?


texts: Is there a radio frequency that is sure to be quiet?

texts:
When flying in beautiful VFR weather, I often search for a quiet frequency so I don't listen to a lot of chatter.

Guard (121.5) sometimes works, but sometimes has "Guard"-ians on it.
("Yer on gaaard")

Many frequencies end up being a distant CTAF that have garbled transmissions.

Short of turning my radio completely off, is there a frequency within the US (or even an ARTCC) that will always be silent, but can easily swap back to a working frequency?

Some have suggested just turning the volume down and back up.
That is functional, but not quite as easy as pressing the XFER button, since the volume may be too loud or too soft after adjusting it.

I like the idea of trying the low-power frequencies that I'm less likely to hear; but I am ultimately hoping to learn of a frequency marked "do not transmit on".


texts: Is there a limit to how large an airplane wing can be?

texts:
There are some agreeably large planes out there, like the C-5 Super Galaxy. But how big can these planes' wings really get?
The heavier the plane, it is usually larger, and with size of the fuselage comes size in the wings (most of the time). But is there a limit to how big you can make your wings?
If you make your wings so big that they're 6 feet thick and an absurd length long, say, for a colossal plane, will those wings provide enough lift? I mean, if the wing gets that big, It not only has to lift the plane, but its own weight then becomes a concern. But, with that weight comes the size. Another issue, is how the aerodynamics work on such a crazy big plane.
The thicker the wing, the more air is contacting the wing. This causes more resistance on the wing at a given chunk than a smaller wing. The question comes from seeing several shows that depict planes so large they're like flying cities, and it just doesn't look realistic to me, the sheer size of those planes.


texts: Is it possible for more than one flight to have the same departure and arrival time slots?

texts:
I'm working with real ATFM data such as the planned departure and arrival times of several flights within a given period of time, and I came across a surprising feature.

I found out that some flights have the same departure and arrival time slots. Taking into account that each time slot covers 15 minutes, I was wondering: is it possible for more than one flight to have the same departure and arrival time slots?


texts: What do pilots do on a windshear alert after V1?

texts:
What is a pilot taught to do, when a windshear is detected and the planes speed is above V1 and before Vr? I can't think of what is safer.

Rejecting, with the risk of overshooting the runway.
Taking off, with the risk of the windshear stalling the plane and dropping it on the ground. If the height of the aircraft was low it probably would just overshoot the runway. If the aircraft already gained some altitude, it could crash.

As well, are there any differences in procedures if the alert occured

After V1 but before Vr
After Vr


texts: How is the 737 main landing gear protected from weather?

texts:
I really like the 737, it is perhaps my favorite airliner. One curiosity of this aircraft (afaik, it is the only commercial airliner) is that the main landing gear has no cover:

Here is another picture from the inside:

In this situation, how does the aircraft protect the gear mechanism from weather/freezing?


texts: What is a good spin aircraft for someone that is heavy?

texts:
I've been trying to get a spin endorsement for my CFI, but I've been having a problem trying to find an airplane that I can do it in.

I'm 280 built like a linebacker.  I'm not that "fat" just heavy.  Losing weight for me isn't really a realistic option since I'm on a time crunch.

The closest thing I have found is an Xtreme Decathlon Citabria, but the CFI I go up with needs to weight 110lbs or less, and I'll probably have to stop for fuel in the middle of the flight.

I was told maybe a 172P model might work since it's utility class is 2000lbs, but I've not found one anywhere locally to verify this and see if they would be willing to let me spin the aircraft.

I'm in DFW, but I'd like to keep this question as generic as possible since others may want to know what other aircraft options there are.  But if you know of and airplane in the DFW area (or surrounding areas) please let me know.


texts: Is an additional rotor useful on a coaxial rotor configuration?

texts: I can understand coaxial rotors cancelling the need for a tail rotor, however, I am curious as to if the second rotor is needed to actually maintain the same pitch or could be just used to offload the primary disk in a powered auto-rotate capacity?  That would just create more drag I assume.


texts: Why would this A-10 Thunderbolt be flown over rural New Hampshire?

texts:
My mother took this photo on December 29th, 2004 on a hill near Groton, New Hampshire. It appears to be an A-10 Thunderbolt, but it's difficult to tell whether or not it's armed. According to her it circled three times close above the hill before going out of sight.

The hill, as well as Grafton County as a whole, are not very populated, and there are no military bases around the area for hundreds of miles. Newspapers for the area on that day show no information that I can see. Can anyone think of a reason for an A-10 to be flown over this location on this date?


texts: How is the D8 Double Bubble aircraft by NASA so efficient?

texts:
How does the 'double bubble' fuselage cross-section of the "Double Bubble D8" aircraft (developed by MIT for NASA) help improve overall efficiency by around 70%?

Image credit: NASA/MIT/Aurora Flight Sciences


texts: I have this question about a density altitude sum that I can't work out. How do you work out density altitude?

texts: So in this question they give you the QNH of 1025hPa, Temperature -4 degrees celsius and airfield elevation of 3850ft. I worked out the pressure altitude which is 3490ft. And now I can't work out the density altitude. The answer that the test gave me was, the density altitude is 2050ft but they gave no explanation. Can someone please work this out for me?


texts: What kind of heaters are used for heated floor panels?

texts: In some Airbus planes, they have heated floor panels. So, what kind of heaters are being used there?


texts: What is required for a pilot to fly in another country?

texts: What is required for someone who holds a pilot certificate in one country to fly in another country? First, I'm wondering if there are any general rules that would apply to any such situation. Second, for the sake of a specific example, what would be required for someone who holds a private pilot certificate in the U.S. to fly an aircraft registered in the Philippines within the Philippines (assuming that the aircraft type is one for which the pilot is rated in the U.S.?)


texts: Which Navigation Specifications support an RF leg?

texts:
I am studying FAA's rules concerning navigation specifications and the utilization of RF legs in an Instrument Flight Procedure. However, I am having trouble understanding if an RF leg is supported by RNAV procedures (RNAV 1 specifically) or only by RNP procedures. After some search in FAA's IFP coded database (CIFP file), I realised that only SIDs labeled as RNP 1 support RF legs, at least as far as FAA's procedures are concerned. However, an introductory page on FAA's site, concerning RNAV and PBN procedures, includes the RF as a general RNAV leg type.

Am I missing something? Could someone point me in the right direction?

EDIT: I think the question that pretty much sums up my confusion is if it's possible for a SID or STAR with only an "RNAV 1", instead of "RNP 1", requirement to contain an RF leg. Because so far I have only encountered RNP 1 SIDs with RF legs, such as STAYY ONE


texts:
in my radio book i came across this communications.

Control: "Pacific 800 report passing FL 150"

Aircraft: "Pacific 800 Wilco"...
           "Pacific 800 passing FL150".

next.

Control: "Fiji 58 maintain 2500 feet"
Aircraft: "Maintaining 2500 feet Fiji 58"

What is the formal explanation for FL and altitude, cause i am confused both are the same thing.


texts: Is the separation distance between two aircraft approaching an airport the same under CDA and Non-CDA scenario?

texts:
I'm working on a project that investigates Continuous Descent Approach (CDA), the procedure by which an aircraft approaches an airport for landing by descending continuously from cruise altitude with idle or near-idle thrust setting. As a Continuous Descent Operation (CDO), CDA provides operational benefits in terms of fuel burn reduction which reduces emissions as well as noise levels around airports.

In my project, I'm studying CDA operations during high traffic periods with the aim of developing key performance indicators (KPIs) for airports. However, I really need some expert and professional advice from pilots and air traffic controllers (ATC) on how CDA is being coordinated, managed, and conducted between pilots and ATCs. The following questions underscore my point:

If a pair of jet aircraft is approaching an airport, is the separation distance between them smaller, the same, or larger under CDA and Non-CDA scenarios?
Just before touchdown on runway, is the aircraft's approach speed the same under CDA and Non-CDA scenarios?
In general, how many track miles could be used for approaching traffic at a major airport?
In general, is the airspeed during descent different between CDA and Non-CDA scenarios?
Just before touchdown, will the pilot utilize thrust to increase speed or will the aircraft be on its own volition, under CDA and Non-CDA scenarios?


texts: How do airline pilots contact their company while in the air?

texts:
Sometimes airline pilots need to get in touch with their company while in the air, for example diagnosing cautionary messages or reporting a diversion. By what means is the communication channel established?

VHF / HF radio? If that's the case, who allocates the frequencies to each airline?
Satellite phone? (Are all aircrafts equipped with one in the cockpit?)
Something else?


texts: What regulations surround fitting aftermarket fuel tanks inside the cabin?

texts:
Watching the first episode of Dangerous Flights, a ferry pilot has aftermarket fuel tanks fitted inside the cabin of an old Merlin IIB:

What are the regulatory requirements to be able to do this? / How can you get permission to fit extra tanks inside a plane?

Is there anything that needs to be specially considered when designing the tanks and valves etc?

Is this commonplace when ferry flying long-haul?


texts: I want to be an airline pilot. Would becoming a NON-COMBAT Air Force pilot be a good way to become one?

texts: I know that becoming a fighter pilot is highly competitive, making it a difficult route, but would becoming a pilot for an Air Force cargo aircraft or something of the like be a good way to reach my final goal of piloting for an airline?


texts: What is the correlation between RNP level and the CDI indication?

texts:
I got a question regarding the connection between RNP (required navigational performance) accuracy and cdi sensitivity of the HSI.

According to the instrument flying handbook the standard for RNP on route would be 2Nm from the centerline.

So for me this means, that I will be at least 95% of my flight in that corridor (given, if raim  is available all the time)

So let's say I am off by 1 Nm enroute due to inaccuracy.

According to Rnp that would be still ok, however the question now is, what would my CDI show me?

The gps obviously does not know that it is 1Nm off course (if so why would we have such a thing like rnp of 2Nm) so the CDI should be centered even though I am actually 1Nm off the correct course.

If this is true I theoretically could be e.g. 4 Nm off course even though I got only a 2 dot deflection on my HSI given that a full deflection would represent 5 Nm because it is not WAAS capable (2Nm rnp + 2 Nm for the two dots)

Thanks for you help in advance...


texts: How long should I wait after I've gotten off my OCD medication to consult an aviation medical examiner?

texts: Im getting off my OCD medicine in a few weeks and wanted to know how long I should wait til i should consult a aviation medical examiner, any advice on which aviation medical examiner I should consult?


texts: Why is most aircraft livery painted, rather than vinyled?

texts:
I just watched a recent AVWeb YouTube video about vinyl decals. In it the owner of Plane Decal says compared to paint, vinyl offers:

a more flexible choice of designs
a cheaper solution - a GA aircraft costing \$5,500 vs \$20-25k.
a quicker install - 6.5 hours vs 6 weeks

Are these assertions correct? It leaves me wondering why aircraft are painted at all if this is the case? What are the cons?

I'm interested in both GA and commercial perspectives, since Bud mentions they've outfitted both.

Here's the video for those who are interested:


texts: What is a typical fuel temperature entering the burner for different mission flight points of a civil aircraft?

texts:
Is there a target regarding the fuel temperature that enters the turbine engine's combustion chamber and if so does it change with different operation flight points in civil aircraft applications?
Is there an online source you can suggest so that I get a better understanding of the fuel temperature variation in a turbine engine, and specifically what is its condition before entering the aircraft's burner?
Thank you in advance!


texts: How can a 777ER fly from the 9000 ft runway at Bologna (LIPE)?

texts:
How can a 777ER be operated from the Bologna runway which is only 9000ft?

I recently took the Emirates flight and the aircraft was full. I suppose that it was close to max weight. According to wiki the required runway at max load is 10000ft so what is the trick behind this?


texts: What is the effect of sudden extreme temperature change on brake disks of large aircraft?

texts: What is the temperature of brake disks at maximum altitude of a jumbo like a 747 and airbus A380 for say a 10 hour flight.  Does the temperature drop below zero and what is the effect on the metal material used on the disk from the sudden change in temperature from one extreme, below zero degrees celcius to over 700 degrees celcius when braking?


texts: Is it correct to say "the up-elevator position decreases the camber of the elevator"?

texts:
Aft movement of the control column deflects
  the trailing edge of the elevator surface up. This is usually
  referred to as the up-elevator position.
  The up-elevator position decreases the camber of the elevator (my emphasis)
  and creates a downward aerodynamic force, which is greater
  than the normal tail-down force that exists in straight-andlevel
  flight. The overall effect causes the tail of the aircraft
  to move down and the nose to pitch up. PHAK 6-5

This is an excerpt from PHAK on the elevator. Do you agree with the statement "the up-elevator position decreases the camber of the elevator"? I've always thought the camber of control surfaces indicates their curvature, which is designed by aircraft designers or controlled by pilots using high-lift devices, and it is the angle of attack that that changes when pilots give control inputs. So isn't it more correct to say "The up-elevator position decreases the angle of attack of the elevator"?


texts: Are the Boeing MCAS and Airbus Alpha Protection systems the same?

texts:
I have a little question concerning MCAS from Boeing and Alpha Protection from Airbus.

I think these two systems are the same, if I'm wrong please tell me.

If the two 737 MAX crashed because of the pilots not knowing how to behave when the MCAS behaves wrong, isn't it possible that the same could happen to A321 pilots?

I remember a Lufthansa flight (Airbus) in which the sensors froze and the pilots also didn't know how to behave. They turned the sensor off after talking with the technicians.


texts: Is it possible to 'derate' a plane as a safety measure?

texts:
Assuming a type of plane has a technical issue that must be fixed related to its flight behavior, could the plane be derated to add safety margin (instead of banning it).

What I have in mind is having longer runway requirements, lower airport T, higher air pressure, softer rate of climb, lower take off weight, etc.

Could this work technically? Legally?

This is inspired by the recent crashes of Boeing 737 MAX-8s, but the question is about types in general.


texts: Why does CFR §91.215 part (b) list specific areas for transponder operations?

texts:
Why does part (b) list individual sections where transponder operations are required when part (c) states that transponder operation is required in all controlled airspace? All sections listed in part (b) are part of controlled airspace anyhow? Similarly, the AIM says that transponder operation is required the moment the aircraft starts moving until the time it stops moving (a simplified interpretation).
Am I missing some subtleties?
Details:
CFR §91.215:
Part (b) contains sections that specify precisely where transponder operation is required. For example:

(1) All aircraft. In Class A, Class B, and Class C airspace areas;
(2) All aircraft. In all airspace within 30 nautical miles of an
airport listed in appendix D, section 1 of this part from the surface
upward to 10,000 feet MSL;
(4) All aircraft in all airspace above the ceiling and within the
lateral boundaries of a Class B or Class C airspace area designated
for an airport upward to 10,000 feet MSL; and
(5) (i) In all airspace of the 48 contiguous states and the District
of Columbia at and above 10,000 feet MSL, excluding the airspace at
and below 2,500 feet above the surface; and
(5) (ii) In the airspace from the surface to 10,000 feet MSL within a
10-nautical-mile radius of any airport listed in appendix D, section 2
of this part, excluding the airspace below 1,200 feet outside of the
lateral boundaries of the surface area of the airspace designated for
that airport.

Then part (c) says:

(c) Transponder-on operation. While in the airspace as specified in
paragraph (b) of this section or in all controlled airspace, each
person operating an aircraft equipped with an operable ATC transponder
maintained in accordance with §91.413 of this part shall operate the
transponder, including Mode C equipment if installed, and shall reply
on the appropriate code or as assigned by ATC, unless otherwise
directed by ATC when transmitting would jeopardize the safe execution
of air traffic control functions.

The AIM says:
AIM Section 1:

4−1−20. Transponder Operation a. General

Transponder and ADS-B operations on the ground. Civil and military aircraft should operate with the transponder in the altitude
reporting mode (consult the aircraft's flight manual to determine the
specific transponder position to enable altitude reporting) and ADS-B
Out transmissions enabled at all airports, any time the aircraft is
positioned on any portion of the airport movement area. This includes
all defined taxiways and runways.

Transponder and ADSB Operations While Airborne. Unless otherwise requested by ATC, aircraft equipped with an ATC transponder
maintained in accordance with 14 CFR Section 91.413 MUST operate with
this equipment on the appropriate Mode 3/A code, or other code as
assigned by ATC, and with altitude reporting enabled whenever in
controlled airspace.


texts:
While reading the FAA presentation on Part 135 Airworthiness Requirements, on slide 7 where it discusses maintenance, the list includes

  inspection, overhaul, repair, preservation, and the replacement of parts, but excluding preventive maintenance

I am sure that the other regulatory bodies have their own, similar lists.

I know that an aircraft overhaul is one of the major processes involved in (especially commercial) aircraft maintenance. What exactly is meant by overhaul? What is done to an aircraft when it is overhauled? And finally, why is it so important for an aircraft?


texts: How long can the stop in a stop-and-go be?

texts:
When a pilot is cleared for a stop and go, how long does this allow them to be stopped on the runway?

I'd like to know if there is a limit in regulations or at least guidance for this.


texts: Why didn't government regulators prevent MH17 from flying the route it took?

texts:
Why wasn't MH17 prevented by government regulators from flying the route it took?

MH17 wasn't the first case of governments or combatants downing commercial aircraft: Iran Air Flight 655 and Korean Air Lines Flight 007 come to mind.

I find it hard to believe that if an area had an unacceptably high risk for aircraft, that it would be up to the individual airlines to decide not to fly that route, rather than governments being flown over, or the source or destination countries, flat-out forbidding it unless there's no alternative.

Was military aircraft (such as Ukrainian Air Force Ilyushin Il-76 and other incidents mentioned in the Background section of Wikipedia's article on MH17) being shot down in the area a new phenomenon, with regulators not acting fast enough to deal with this new information?


texts: We have several spectacular and amazing videos of aircraft, flying high in the sky.  How are these videos filmed, at great altitudes?


texts: Why is the air traffic control profession so commonly perceived as "stressful"?

texts:
In my experience, almost every time the topic of air traffic control (as a career) comes up in conversation, someone makes a remark like

  Air traffic control - isn't that a very stressful job?

Notwithstanding the fact that this point could be debated, surely there are many other "stressful" jobs which don't receive this kind of response.

My question is this: How did the "stressful" air traffic control job become such a common perception?


texts: If an aircraft is not IFR-equipped nor the pilot IFR rated, is it possible to get a border country to grant access from their CAA authority?

texts:
This could also apply to neighbouring countries that are just over water like UK-France, Canada-US (Lakes).

Basically, a VFR flight only with permission granted from that country (if that's possible?).

And if so, then how would it work?

(Obviously you'll need: en route charts, passport, aircraft papers, PPL license.)


texts:
I was wondering if anyone can help me identify either of these drop tanks?  The one in front in the top photo measures about 11' long.

(Source of second photo-- this related ASE question)


texts: Is there any data repository of discontinued commercial routes?

texts:
Is there any way of knowing - for example by referring to an existing data repository or something similar - what commercial routes were operated from a given airport in a given year?

This would be a list of all commercial routes that have been discontinued.


texts: What is the maximum safe bank angle of a 747?

texts:
This question arose during the comments of another question, linked for the curious:
What does it take to turn a 747 around 180 degrees?

Because the discussion was interesting, (and to avoid congesting the comments of another user's question), I reposted it here.

Does anyone know the answer to this? Official sources/experience are preferred, but I'll take what I can get.

  If I was at altitude and suddenly realized we were about to cross into airspace that might get us shot down, I would, smoothly, do 3 things simultaneously: (1) start the nose down to around 25 degrees down, (2) start a roll to a bank angle of 60-80 degrees, and (3) start the power back to idle. At the same time, I'd ask the first officer to deploy the speed brakes, which would give me great roll response. –  Terry

To which I replied:

  80 degrees of bank would be a bit excessive no? 60 might be reasonable for an emergency turn, but certainly no more in a 747? (G-forces aside) –  HCBPshenanigans

Terry's reply:

  I was thinking of a range because, in an emergency turn, hitting an
  exact degree of bank would be hard. I would, however, not want to go
  beyond 90 degrees because of the possible disorienting nature for the
  flight crew. At 60 degrees, approximately 87% of the wings lift would
  be turning the airplane. At 80 degrees, about 98% of the lift would be
  turning the airplane, so the lesser bank would sacrifice 11% of the
  turning force. I would expect to lose a lot altitude in the turn. I
  can't think of a reason not use 80 degrees. Pax comfort would be a
  non-issue. –  Terry

My most recent response:

  Idk if you are a real 747 captain (there are quite a few on here), but
  iirc many 747 crashes have happened because when the aircraft banks so
  hard that it loses that much vertical lift, it is very difficult to
  recover from. In addition, some flight systems might malfunction under
  these rather extreme conditions. 60, hell even 70, is much steeper
  than it seems. I seem to remember seeing an episode of that old Air Disaster show about just this. –  HCBPshenanigans

Edit: What kind of difference would the difference between 60 and 70 or 80 degrees of roll make in time to turn 360 degrees?


texts: How could a failed left wing cause a roll to the right?

texts:
The crash of Continental Express flight 2574 in 1991 (see also this question) was caused by faulty maintenance to the de-icing boot on the left horizontal stabilizer. This became detached in flight, leading to violent movements of the plane which caused the left wing to fail and the right wingtip to detach.  Ultimately, the horizontal part of the T-tail detached and the plane crashed.

The NTSB report says (page 34, with essentially the same statement repeated on page 37):

  The airplane then rolled to the right at a roll rate exceeding
  160 degrees per second. The Safety Board believes that the lift produced by the
  intact right wing produced the extreme roll.

The report also says that the initial failure of the left stabilizer caused a 10–15° roll to the right, which makes sense: the loss of downforce from the stabilizer meant the left side of the plane was generating more net lift than the right. But how would the subsequent failure of the left wing produce a roll to the right? The natural assumption would be that, with the right wing generating lift and the left wing not, the plane would roll to the left.

Possibly relevant is that the left wing failed but didn't detach from the plane: the plane crashed right-way-up with the left wing folded under the fuselage and the inboard portion of the right wing.


texts: How do I "sightsee" in a class Bravo airspace?

texts: There are some good sights to see inside of class Bravo airspace. What is the best way to plan and communicate to ATC that my intention is to fly into the airspace to see some specific landmarks?


texts: Why do wing tip vortices tend to be most dangerous when there is a light quartering tailwind?

texts:
I understand how wing tip vortices be effected under a headwind or crosswind. However, what are the differences in effect between tailwind and light quartering tailwind?

Why is it most dangerous when there is a light quartering tailwind?


texts: Why does the Eurofighter Typhoon has a long arm canard vs the close coupled canard of Dassault's Rafale or JAS-39 Gripen?

texts:
Rafale and Gripen are quite similar but the Eurofighter Typhoon has the canards far forward. I've been told that this was due to the shape of the air intake.
Apparently the Typhoon's air intake was designed to work in combination with Thrust Vectoring Control. This feature was never implemented so I believe the canards may be less effective than other aircraft, in terms of performance, (specifically turn/pitch rate).
Am I totally wrong?


texts: What is the drag (or $C_D$ vs $C_L$) of the Airbus A320 in cruise flight?

texts:
Is there any website or data-sheet that I can find drag of airplane for cruise conditions. $C_D$ vs $C_L$ graph is also acceptable.

To be more specific I am searching drag values of A320 in cruise flight.


texts:
Or said in another way, does packing lighter on a trip actually make a dent in one's co2 emissions?

According to The carbon independent site,

  CO2 emissions from aviation fuel are 3.15 grams per gram of fuel [38] , which gives CO2 emissions from a Boeing 737-400 of 115 g per passenger km.

What it does not talk about, however, is the weight of the passengers and their luggage.  Any write-ups on that?

What are the average per-passenger-kilogram carbon emissions of common commercial passenger aircraft per kilometer?


texts: Need help identifying planes, near Toronto


texts: What is the mathematical relationship between Specific Excess Power and an aircraft's acceleration at a given point on an E-M diagram?

texts: If an aircraft is on the x-axis of an E-M diagram plot (zero turn rate) where the Specific Excess Energy (Ps) = 800, we understand this to mean that the aircraft has the potential to either instantaneously gain 800 ft/sec of altitude OR instantaneously accelerate.  If an acceleration rate is desired, this could be determined by converting the 800 ft gained (h) as potential energy to kinetic energy using an equation V = SQRT {2 x g x h}.  Substituting the variables, V = SQRT {2 x 32.2 x 800} yields 227 ft/sec gained each second (or acceleration of 227 ft/sec^2)  However, this is an unusually high amount of acceleration for even a high performance jet accelerating in straight, level flight (7 g's).  There is something clearly wrong with my logic/math but I can't figure it out.  Can someone offer the correct derivation?


texts: Are there any rules requiring hands/feet on the controls at all times?

texts:
Are there rules that require one of the pilots in a large commercial aircraft to have positive physical control of the yoke/joystick at all times?

And the same question for the rudder actuators, if any (pedals)?


texts: Is it possible to fly with throttles staggered?

texts: Does the autothrottle realign the throttle lever positions? If the throttle is staggered, does it mean that there is an issue on the engines?


texts: Do helicopters need a class B entry clearance when air / hover taxiing?

texts: You're a helicopter pilot at a class B airport. You'd like to taxi to another parking spot. The ground controller could either give you a hover taxi clearance or an air taxi clearance, depending on the situation. Either way will get you off the ground and (technically) gets you to enter the class B airspace. Would you need to obtain a class B entry clearance prior to requesting your taxi clearance?


texts: Symbology on standard terminal arrival (STAR) charts: T-ended vs arrow-ended lines?

texts:
I was looking at the STARs at KPHX. The ARLIN FOUR arrival here has T-ended lines between the BLYTHE VOR and SCOLE, and between SCOLE and CALIE fixes. It also has arrow-ended lines between CALIE and HYDRR, and between HYDRR and PAYINT.

What does the difference in symbology mean?

At first I thought it indicated a different MEA, but then I looked at the DSERT TWO arrival here, and I see the T-ended lines between SHOCK and BUSTD, and between BUSTD and YOLOW, and the MEAs on both the neighboring segments is the same (9000).


texts: What was used instead of the failed engine when ferrying the Air France Flight 66 aircraft back?

texts:
After engine 4 failed in Air France Flight 66, the airliner (an Airbus 380) landed at Goose Bay in Canada. I am aware that following that, the failed engine was removed and then something "nonfunctional" was installed in its place "to balance the weight". This looks like a strange story to me:

What was this "non-working replacement" and where did they get it? It still needs to have the required weight, shape and mountings. Was it quickly manufactured? The source referenced by Wikipedia even calls it a "spare engine". Did they install the engine intended for a different airliner?
In general if the goal was just to have a non-operational engine on the wing, why not leave the failed no. 4 engine where it was? Or was there a risk of it falling to pieces during the ferry flight?


texts: How do aircraft differentiate between missile locks?

texts:
I have explored many similar questions such as:

How does a Missile Lock Work?
How is a missile lock detected?

In reading there respective answers, I have learnt about the multitude of detection mechanisms employed, but one question lingers and remains unanswered:

How would an aircraft differentiate between the multiple missile lock signals it would likely be receiving?

In a dogfight scenario (although they can occur over a large distance) a single aircraft may well detect the signals emitted by either the missile as part of an "Active Radar Homing" mechanism, or from the launcher itself as part of "Passive Radar Homing", regardless of whether the aircraft is the intended target, presumably causing every aircraft in the area to be notified to the single missile lock.

I don't pretend to be well versed on the subject of aerial warfare, yet I consider it nonsensical that every aircraft in the engagement be notified to the missile lock of a single aircraft as it would distract the pilots, all of whom would be required to ensure that they are not the targets.


texts: Tonight's fireworks got me wondering:  With all of the firework displays happening at the same time, how do they keep aircraft away from them?  Is there any risk of collision or blinding the pilots?  Is there anything that pilots need to do differently when fireworks are in the area?


texts: How are temperature differences handled in a jet engine?

texts:
Given the graph in this answer, the temperature are quite high inside a jet-engine, even greater that many metal's melting point. I understand high core temperature are efficient.  A jet engine is designed to work for several hours at those high temperature.

Moreover, starting the engine (i.e. going from ambient temperature everywhere inside the engine to more than 1500°C in the combustion chamber while not significantly changing the temperature at the first low pressure compression stage) may be quite stressful for material.

My question is in two parts:

How is the high temperature handled, especially in the combustion chamber and the high pressure turbine? I read somewhere that the turbine can be cooled by air flowing inside the blades but I cannot find the reference. I also wonder where this cooling air comes from.
How is the stress on material due to temperature changes (between full thrust and shut down, and maybe when changing thrust in mid-flight) handled?


texts: What does a numbered dot mean on a sectional chart?

texts:
What does this point (125) mean on a Sectional Chart?

Is it the field elevation, or just the highest elevation on the area?


texts: Is there an advantage to combining trim function with yoke?

texts:
SUMMARY: What if the yoke didn't require constant pressure, as is the case with the current "trim" function?
In all cases that I know of, airplanes have had the yoke (which you need to apply constant pressure on) and trim (which you don't) separate. The yoke is used to short inputs, such as a roll or a pitch down, and the trim is used to maintain the aircraft in a specific attitude, given the changing nature of center of lift and gravity.
But I do not understand why it is necessary for them to be separate. Trim can do (almost) everything a yoke can. Would it be a good idea to combine the two?
Some advantages:

simplification
Safety; fast reaction to sudden trim changes (such as part of wing or empennage breaking off)

Some drawbacks:

trim does not center itself, so there's that inconvenience
increase chance of wild maneuvers if left unattended while deflected


texts: Explain how the infrared flame detector work?

texts: For fire detection systems, such as for engine fire detection, how does the infrared flame detector work?


texts: Do aircraft always have the right of way on the ground? Or must they yield to police/fire/ambulance?

texts: I know FAA said aircraft always have the right of way over ground vehicles. What if a police car, ambulance or fire truck needed to pass?


texts: Is it possible to control the inlet Mach no. of the engine during flight?

texts:
While calculating the off design conditions of the engine, we need to know the off design characteristics, such as inlet additive drag. In the book Mechanics of Flight, by Warren F. Phillips, its expression has been derived as a relation between free stream and inlet Mach no. Further while calculating the drag,in one of the example (2.6.1), the inlet Mach no. has been assumed constant at 0.6 whereas the flight is accelerating from Mach 0 to its design Mach no.

This implies that the inlet Mach no. has been somehow achieved as 0.6 even at takeoff, is it practically possible? If not, then how is the drag actually calculated during flight with varying free stream and inlet Mach numbers?


texts: How to calculate service ceiling and absolute ceiling in PA-44 Seminole?

texts: I am hard to understand to calculate service ceiling and absolute ceiling in PA-44 Seminole. Is there anyone know how to calculate it in the condition(T/O weight: 3599.24 L/D weight: 3354.44 PA:2329 Temp:20)


texts: What is the "8900" that the FAA uses for guidance?

texts:
The 8900 is sometimes quoted as a reference when trying to determine FAA policies.

What exactly is it and where can it be found?  Is it regulatory in nature?


texts: What is the difference between the WSUSnn IDs used in convective SIGMETs?

texts:
When NOAA issues a convective SIGMET, it falls under one of three bulletin IDs: WSUS31, WSUS32, or WSUS33. Below are three examples from the current forecast.
WSUS31:
WSUS31 KKCI 020455
SIGE
CONVECTIVE SIGMET 24E
VALID UNTIL 0655Z
PA
FROM 30NNW JST-20SE EWC
LINE TS 25 NM WIDE MOV FROM 24025KT. TOPS TO FL340.

OUTLOOK VALID 020655-021055
AREA 1...FROM 130SSE ILM-210ENE TRV-TRV-SAV-130SSE ILM
WST ISSUANCES POSS LT IN PD. REFER TO MOST RECENT ACUS01 KWNS
FROM STORM
PREDICTION CENTER FOR SYNOPSIS AND METEOROLOGICAL DETAILS.

AREA 2...FROM 70NNE
ASP-ECK-DXO-CLE-BUF-SYR-BKW-VXV-MSL-TTH-TVC-70NNE ASP
WST ISSUANCES POSS. REFER TO MOST RECENT ACUS01 KWNS FROM STORM
PREDICTION CENTER FOR SYNOPSIS AND METEOROLOGICAL DETAILS.

WSUS32:
WSUS32 KKCI 020455
SIGC
CONVECTIVE SIGMET 30C
VALID UNTIL 0655Z
MI WI LS
FROM 30SSE YQT-40SSE DLH
LINE TS 30 NM WIDE MOV FROM 27050KT. TOPS TO FL310.

OUTLOOK VALID 020655-021055
FROM TTH-MSL-ELD-LFK-DLF-TCC-GCK-RZC-TTH
WST ISSUANCES EXPD. REFER TO MOST RECENT ACUS01 KWNS FROM STORM
PREDICTION CENTER FOR SYNOPSIS AND METEOROLOGICAL DETAILS.

WSUS33:
WSUS33 KKCI 020455
SIGW
CONVECTIVE SIGMET...NONE

OUTLOOK VALID 020655-021055
TS ARE NOT EXPD TO REQUIRE WST ISSUANCES.


texts: What is the relation between velocity and rate of pitch?

texts:
I saw the answer to airspeed and rate of turn but this I think isn't what I want. I've seen it many times that aircraft will pitch up much slower when at higher speeds particularly fighter aircraft. What is the mathematical relation of these two characteristics if any?

I am trying to make a game about fighter aircraft and want to find a realistic solution to this problem.


texts: What charts do I need flying VFR between KPRC and KLAS?

texts:
Some friends and I are going to fly up to Vegas from college to watch the Red Bull air races in a few weeks.  And after looking at the charts, I realized I am in a pretty unique situation.

The Phoenix sectional ends just short of Vegas - so normally I would buy a Vegas sectional.  However, the KLAS TAC extends just into the Phoenix sectional.

Should I buy the Vegas sectional as well, or can I just use the KLAS TAC once the Phoenix sectional ends?


texts: Does this web page really correctly depict the angle that is called "incidence" in the French language in the aviation context?

texts:
Does this web page really correctly depict the most common usage of the term "incidence" in the French language in the aviation context, in the context of speaking of an entire aircraft and not just an isolated part such as a wing section in a wind tunnel?  Is the label "incidence" really attached to the correct angle?

I am referring specifically to the second airplane diagram, i.e. the first diagram that shows an airliner.   Note that the text above the diagram uses the phrase "en croisière" which is a reference "cruising", presumably horizontal, flight.  The line x-x' appears to represent the longitudinal axis of the aircraft, so it appears that the angle labeled "incidence" represents the angle between the flight path/ relative wind and the longitudinal axis of the fuselage, not the angle between the flight path/ relative wind and the chord line of the wing, which would clearly be a larger angle.

In fact the text above the diagram explicitly states "L'incidence est définie par rapport à l'axe de l'aéronef et non de la voilure.", which translates to something like "The incidence is defined relative to the axis of the aircraft and not of the wing."

Shouldn't the angle labeled "incidence" be the angle between the flight path/ relative wind and the chord line of the wing rather than the angle between the flight path/ relative wind and the fuselage?

Or is it just a matter of arbitrary convention, meaning that either usage would be equally appropriate?

(One way to concisely answer this question might be "The correct usage of 'angle d'incidence' in the French aviation context is exactly identical to the English-language usage of 'angle of attack' (or replace with other appropriate angle as needed) as noted in this ASE answer (give link)."  Not all ASE answers have given the same perspective on the most correct usage of this term.)

Note that the angle labeled "angle de calage" is the angle that is called "incidence" in American aviation usage and some or most (but not all) British aviation usage-- the angle between the chord line of the wing and the longitudinal axis of the fuselage.  This question is not about whether or not the diagram uses "angle de calage" correctly in the context of French aviation terminology-- it clearly does.

Bonus question-- in the French aviation context, is the term "angle d'attaque" used to mean something different than "angle d'incidence"?


texts: Why does this B-52 carry a payload only on its right wing?

texts:
Here is a picture of a B-52 located at the Pima air and space museum.

Source:(www.airplaneexhibits.com)

As you can see in the picture on the right wing next to one of the engines there is some kind of missile carrier, but the left wing has no missile carrier. Wouldn't the weight of the aircraft be very unbalanced with a missile on the right side, but no missile on the left side. I have noticed this in a lot of pictures of B-52's where they are carrying a missile on the right wing, but no missile on the left one.


texts: How does a pilot select the correct ILS when the airport has parallel runways?

texts:
How do you not mess up ILS on parallel runways? There are many airports with ILS and parallel runways, how do you select which ILS for the runway you want?

For example there are RWY 22L AND 22R and both of them have ILS enabled. How does the pilot know on which ILS he is flying?


texts: Where does fuel from the boost pumps go before engine start?

texts:
For example let’s take the PT6A-27.

In every video related to engine start I see, the fuel boost pump is turned on, and then the fuel pressure goes up.

Example:

My question is: where is that fuel going if the condition lever is still at the idle cutoff position? Don’t you flood the engine?


texts:
In a comment to an answer regarding instrumentation complexity, an "energy variometer" was mentioned, labeled in knots. What does this dial actually show, and how does it work?

The image accompanying the answer in the linked comment was this, with the energy variometer shown at the top left. Don't get distracted by the legs. :)

As it is labeled with +- knots, I would assume it is showing rate of change in airspeed (i.e. acceleration), but calling it an "energy variometer" suggests that it is a combination of altitude and airspeed in which case it would show positive when entering updrafts (or when being towed) which is obviously useful for a glider. Either way it would be interesting to know how it works.


texts: How much would it cost for a large airline to switch engine manufacturer for their planes?

texts:
I am trying to understand how much of a hassle and cost it would be for a large civil airline, who already had lots of installed Rolls Royce engines on its fleet, to switch over to GE engines on new planes they have ordered. For example if they opted for the RR Trent 1000 on a 787 initially but then changed new orders of 787's to have the GEnx-1B.

Very intangible I know, but would it be fair to say that switching would require some difficulty including:

retraining of pilots
changing maintenance schedules
additional uncertainty over performance and fuel efficiency

Alternatively, I could be wrong, and the airline will likely just switch to the GE if it thinks it can gain a small fuel burn advantage, in which case RR's back book of engines does not mean clients will opt for the RR engine choice going forward.


texts: When landing a modern Jet such as the Boeing 737, what is the primary source for descent? The elevators or gravity(from reduced airspeed) or a combination of both? Is the glide path angle of descent a series of step downs where the Jet levels out in steps as its descending? In computer generated simulations , it appears as though the plane stays level throughout the entire descent and I'm wondering if that's actually what happens and if so how it is controlled?


texts: Why do some turbofan blade have forward swept tips?

texts:
I notice that in Trent700  engine fan blade there is no curve extension at the tip unlike in other engine's fan blades such as the GE90 ,T900 etc.

What are the purpose of it?

Trent 700 without forward swept blade tips

Engine with forward swept blade tips


texts: Why are piston engines for aircraft rarely diesel powered?

texts:
Why hasn't diesel caught on much for aircraft engines?  The list of diesel aircraft engines on Wikipedia is very short.

The reason I see mentioned is their poorer power-to-weight ratios. (e.g. What are the advantages/disadvantages of diesel/Jet A-1 piston engine?)

I knew this was true in the past but is it true even today? Does anyone have values comparing the power-to-weight rations of typical diesel vs gasoline engines, say for automotive use?

Also, doesn't the better efficiency, especially at higher altitudes compensate for the poorer power-to-weight ratio by allowing lesser fuel and more payload?

50 years ago diesel engines for automobiles were uncommon too but in the last decade they have been steadily making headway in the car market. Do the same developments translate to the aircraft engine  selection too?

Other than weight, are there any other disadvantages of diesel?


texts: Why do aircraft on Flight Radar 24 jump around randomly sometimes?

texts:
I use Flight Radar 24 on my iPad to track friends/families flights when they are traveling (not paranoia, just curious).  I've noticed that, quite often, their plane will jump from one location to another, or jump backwards down the flight path, or zoom forward, or any other number of motions that I assume the plane isn't actually making.  (My personal favorite being when they miss the runway on touchdown and the plane disappears.  If that actually happened as often as Flight Radar 24 made it look like it was happening...)

What makes the planes do this on Flight Radar 24?  Why can't it just track the planes correctly?


texts: Why not use flaps in take off from High Density Altitude airport?

texts:
Why can we use flaps in short field take off but not in high density altitude airports?

Why can't they be used in high density altitude to shorten the take off distance as in short field take off?

Why short field take off with flaps doesn't apply to high density altitude airports?


texts: Why don't commercial airplanes carry Earth-observing instruments?

texts:
Governments and private companies spend hundreds of millions of dollars to send Earth-observing satellites to capture imagery or scan the terrain with lasers or radars.

Meanwhile, commercial planes are constantly flying around the world, and even if they do not offer global coverage, they could still carry Earth-observing instrumentation with almost no additional cost. I'm sure the data they could provide would have many scientific and commercial applications. In some cases they could be even better than satellite observations due to much shorter revisit times, less atmospheric influence and shorter round-trip times for laser and radar signals.

For example, some satellites like IceSat and IceSat-2 were designed to repeat laser altimetry observations over the same ground tracks over and over. With much interest in Greenland, the icefields in Yukon/Alaska and Antarctica. Again, in this case, commercial flight could provide very good coverage of the first two areas of interest at a fraction of the cost.

I'm a glaciologist working on the Patagonian icefields, where the persistent cloud cover renders most of the images captured by Earth-observing satellite useless. I'm evaluating the possibility of contacting authorities and airlines to collaborate in a project to put instrumentation on the planes that overfly the icefields several times a day. However, I'm sure that I'm not the first with this idea of putting instruments on commercial planes. Thus, I'm surprised that no commercial airplanes carry Earth-observing instruments.

Therefore my question:

Is there any insurmountable technical or legal limitation to equipping commercial airplanes with Earth-observing instruments?


texts: How come diverterless supersonic inlets haven't been discovered much earlier?

texts:
DSI's seem like such an absolutely elegant solution to a problem that has, so far, been solved in a truly overly complicated way.

So, if I'm not missing out on some important small speck of knowledge that complicates DSI's way, way more than being a bump to subsonicize air (of course a slight bit more than that, but you get the idea), then I feel like it is justified for me to get the well-known "this stuff is way too easy to be true"-feeling.

To actually ask the question: Are DSI's really as easy of a solution as they seem right now?


texts: Do emergency services helicopters fly VFR when leaving base?

texts:
I've recently been watching an interesting documentary on helicopter paramedic teams. As you all probably know, their job consists of a lot of sitting around doing nothing before a scramble and then a short (or not-so-short) flight out to the middle of nowhere and back again. On the (UK) documentaries I've seen, the aircraft are usually based at reasonably large commercial airports, physically located close to the fixed-wing runways.

In order to find the guy lying injured in the field and help him out of asystole, they have to rapidly launch from a presumably busy airspace, and get there ten minutes ago. Do airports have procedures that allow them to always assume an "exit route" is always okay, under some ceiling? Do they have to get take off clearance as other private aircraft would? I understand that they get given priority ATC clearance when in controlled airspace, but quite often their target call-to-takeoff times are less than two minutes, and it seems unlikely that the nearby 777 on FA would be done that quickly.

What happens if it's not possible to be VFR entirely on route? I have seen cases reported where difficulties are encountered due to fading light halfway through treating a patient --
meaning that the pilot is worried he can't take off again. It seems rather odd that, if a pilot was able to land in a field comfortably with good visibility, he can't ask for a route to be cleared, file a flight plan, and go to hospital IFR.

For that matter, how do police helicopters chase the bad guys at night in zero visibility?

Disclaimer: I've never set foot in a helicopter in my life, but have a single-digit number of hours in light aircraft -- sick people are more my forte.


texts: What was the first jet-powered supersonic aircraft?

texts: Just to clarify: I am explicitly not referring to the Bell X-1, or any other early experimental supersonic aircraft that were rocket-powered. I'm curious as to the first supersonic aircraft powered by an air-breathing jet engine, as well as (if possible) the technological innovations needed to transition from rocket-powered to air-breathing supersonic flight.


texts: Do pilots reject takeoff if aircraft doors are not properly locked down?

texts:
This particular incident, the pilot rejected takeoff "due to a aft door indication".

My questions are:

Is it a such serious situation so as to reject take-off?
If the pilots had taken off, could the crew have secured the door on their ascent?


texts: In a piston aircraft, how much noise is generated by the engine, and how much by the propeller?

texts:
I've been reading quite a few articles lately about how noise complaints from GA airports across the country.  One of the common suggestions to fix the issue is to simply use an electric engine instead of a gas powered one.

Leaving aside other practical concerns (batteries and weight for example), would this actually significantly reduce the amount of noise a GA aircraft makes?  I'm told a lot of the noise actually comes from the propellor itself, not the engine.

So, in essence:  How much of the noise from a GA aircraft is made by the engine, and how much is the propeller?  And does the percentage change depending on the phase of flight?

Note: I am not asking for subjective answers here.  My hope is that someone actually has a decibal break down of how much noise comes from the engine, and how much from the propellor.  Yes, I know it will vary by craft.  An average would be fine, or perhaps numbers from a popular GA craft (like a Cessna 172 or Piper Cub, for example.)


texts: What is the difference between a POH and an AFM?

texts: Some aircraft come with a Pilot Operating Handbook and some come with an Aircraft Flight Manual.  Why the different name, and is there a difference between them?


texts: Would failure to put on an oxygen mask during loss of cabin pressure result in death?

texts:
I was trying to explain to someone why the cabin is pressurized (no one wants hypoxia) and that led to discussion about the emergency oxygen masks available on airliners.

If a person didn't put on their oxygen mask, would they be able to survive the lack of oxygen while making an emergency descent to a safe altitude? Would they sustain severe brain injury?


texts: Did the Germans ever use captured Allied aircraft against the Allies?

texts: I have noticed that during WWII the Germans captured quite a few P-47s, P-51s, Spitfires, and other Allied aircraft. I know that they tested them extensively but wanted to know if they ever used them against Allied aircraft.


texts: Is ear protection necessary for General Aviation aircraft?

texts: What would happen if someone flew a brand new Cessna Skylane/Caravan or a Robinson R22 without using earplugs or headphones? Would they get hearing damage or it would be just a little bit loud where communication with co-pilot need constant yelling? How serious ear damage is?


texts:
Can somebody please identify the second aircraft. I tried reverse search but no use :C.
I'm trying to win a boeing 777 model :D


texts: What is the difference between the Flight Control Systems of different F16 models?

texts:
it is mentioned that the F16 A/B variants had an analog FCS, while the C/D version introduced a digital FCS starting from block 40.

Can somebody elaborate on the differences between them and point me to some reference?


texts: What are good tips for flying across Tejon pass?

texts:
I will be flying from Northern California to Southern California this weekend for the first time in a C172SP (KPAO to KFUL). My planned altitude is 9500 feet. I had a talked with my former instructor about this flight. We had gone over the flight plan and he told me his tips on flying this route including using extreme caution when flying over the Tejon pass (by Gorman VOR) because of its strong turbulence.

Has any of you flown this path before can possibly give me some tips? Anything is appreciated especially tips about passing the Tejon pass.


texts: Why is the CG envelope wider when the aircraft is heavy?

texts:
I mean, the same aircraft, but empty or on MTOW. According to MAC, those limits are the same, but the indexes are different. So if I understand that correctly, the CG can be more forward when the aircraft is heavy.

E.g., this Boeing 747 (and all 747s I have seen had an envelope like this), page 20, Report on the serious incident at Oslo airport Gardermoen on 21 September 2004 involving flight KAL520 Boeing 747-400F registered HL7467 operated by Korean Air.


texts: What's the possibility of a commercial airplane crashing due to a computer error?

texts: In line with this great question, what's the possibility of a commercial airplane crashing due to a computer error? Or are there already known cases of this? As a passenger, should you be worried about this possibility happening to you someday in the future?


texts: What regulations support European vs USA traffic pattern entry?

texts:
While reading another Stack Exchange question I became aware that Europe approves several more "standard" (for training purposes only, but encapsulates European maneuvers)  traffic pattern entries than the US. AC90-66A.pdf dated 1993 once authorized more than the Europeans but is superseded by date (2016) to the information in the "Airplane Flying Handbook (FAA-H-8083-3B) Chapter 7 (2016)".

Of course we follow ATC at controlled airports and are not held to any specific pattern at uncontrolled. Most pilots try to be considerate and consistent when possible, and predictable for safety reasons.

Similar but different StackExchange questions include...

Is a full traffic pattern required when there is no traffic at an untowered airport?

How is a traffic pattern oriented, entered and exited?

The illustration below shows an overlay off approved entries. The US is in red per FAA-H-8083-3B, and Europe in blue. Note the US approves a circle to the outside of the downwind that Europe does not. Europe acknowledges a straight in (don't we all do this?) but the US does not apparently acknowledge a straight (perhaps discouraged for safety reasons) - at least not in the latest 2016 FAA-H-8083-3B?

Does ICAO or another regulating authority offer any recommended International standard that the FAA is ignoring?


texts: Did Biplane pilots turn off their engines before landing?

texts: I read or heard one time that radial engine biplane engines were turned off just before touchdown because if the throttle was used, the torque could cause the wing of the plane to contact the ground and a lot of pilots were killed just landing biplanes. Is that true?


texts: Could an electric airliner be aerotowed to cruise altitude by an electric "tug" aircraft?

texts: The low energy density of batteries make electric aircraft need a high ratio of battery to payload. Take off and climb to cruising altitude could account for a substantial fraction of the energy required for a short haul flight. The point of aerotowing would be be to have less battery (and maybe motor?) requirement and more payload in the towed craft for cruise and landing whilst the tug aircraft could return to the take-off point. There would be the downside of needing to handle the tug landing of course.


texts: Are the replacement satellites for Iridium going to provide surveillance coverage?

texts:
Iridium satellites are to be replaced using SpaceX rockets.

Will the new LEO satellites be used for continuous tracking of commercial flights?


texts: What is this flyer in a 1911 short film?

texts:
In the very first instants of the 1911 comedy short film Robinet aviatore (or Tweedledum Aviator) by Michel Fabre, which can be watched here, on the background some kind of flyer can be seen.

Does someone have a clear idea of what kind of flyer is that? A Wright one?


texts: Is a 40-year-old person too old to start an ATC career?

texts:
My wife:

is 40 years old
is a mother of two (able to do five things simultaneously / in the same time)
has been working as an English and French teacher for her whole career (19+ last years)
has very little to do with airline industry (being a passenger and low-level enthusiast)

I think that this is enough (especially point 2. and 3.) and I'd like her to at least try to become an ATC (i.e. enroll for a preliminary English test).

She is reluctant saying that she:

is too old
have very little or no technical background / education / experience

to pass even first tests, not mentioning becoming a professional ATC.

Can anyone judge which one of us is right or at least provide some source of information, based on which such judgement can be done? I.e. to formulate an answer (similar to this one) on unique challenges and limitations for starting a career as an ATC at 40 years old?

It is possible in the country where we live (Poland). The original limitation (26 years old) was raised to 35 years old some 10-15 years ago and then 40 years at most. And now the age barrier is lifted completely.


texts: Measuring speed and altitude from personal phone midflight

texts: Given that there is no need now for one to swith off their cellphone midflight, inflight wifi is now  a norm and common, Is it possible for me to measure the velocity and altitude of an aircraft using my personal car GPS speed indicator or cellphone app in the case of speed and altitude as a passenger?


texts: What questions should I expect during an EASA skill test?

texts: I have my skill test in few days. I'm lost on what are the questions that will be asked during the oral part of the atpl skill test.


texts: A modern replacement for DH.82's Gipsy Major engine

texts: While I deeply appreciate any vintage aircraft that is powered by their original engines, I was wondering if there are any modern replacement engines available for the de Havilland Tiger Moth aircraft with Gipsy Major engines installed that require no or minor modifications of either the aircraft and/or the engine itself?


texts: Is there a maximum horizontal acceleration for passengers?

texts:
Are there any regulations regarding the maximum acceleration forces that passengers should experience during takeoff/flight/landing?

Or what would be considered to be an acceptable horizontal acceleration? 0.5g? 1g?

I am contemplating how to achieve very good STOL characteristics for a small  commuter aircraft while still maintaining a high wing loading.


texts: What does "airspace above 14,500 MSL is controlled with few exception" mean?

texts:
I was reading Cessna IFR Training program and came across this line that airspace above 14,500 MSL is controlled with few exceptions.

What does it really mean? Class A doesn't start until 18,000 ft, and although Class E is controlled, it is legal to fly in and out of this airspace without talking to anyone, additionally it also doesn't require communication or navigation equipment. So I have following questions.

If I am away from radar coverage area but inside Class E and flying VFR at 15,500 MSL, is that controlled or uncontrolled, if controlled then controlled by who?
Did they mean to say that as you recall class E is controlled?
What is the real world example of airspace above 14,500 ft MSL but uncontrolled?


texts: Where does ice collect first on a wing in flight and why?

texts: I've seen some reports that say ice forms on the back half of the wing and on the outside edge of the wing (the part furthest from the body) before it will form anywhere else.  I'm wondering if this is true?  Where does ice first form on a wing (in flight) in icing conditions?


texts: Why do all fifth generation fighters (J20, F22, SU57) use Trapezoid wings?

texts: It seems that trapezoid wings are used by all fifth generation fighters (although the wing of J20 looks quite like delta wing), but why? What made a trapezoid wing so attractive? Why don't they use other forms, like the swept wing on SU27?


texts: What kind of damage would low-level supersonic flight inflict?

texts:
I was watching a video about "The Big Stick" aka Project Pluto, a nuclear powered SLAM. In the video (I couldn't find the exact video) it said that after deploying its weapon payload a SLAM could fly over its target country as a "vengeance weapon", causing destruction with it's sonic boom for weeks and an altitude of just a few hundred feet.

What kind of damage would a mach 3 flyby at 200 feet cause?

I'm interested in both building damage and possible human injury.


texts: Why aren't larger airliners such as the A380 more efficient than smaller ones?

texts:
A recent Washington Post article, titled "Five myths about air travel" noted:

  The difficulty is that economies of scale don’t always work for airlines, because planes generally don’t increase in per-passenger efficiency as they grow larger. In fact, many of the most efficient planes of today are the smallest ones. At a transatlantic distance, a 525-seat Airbus A380 has an efficiency of 74 miles per gallon (mpg) per passenger, while the brand-new 168-seat Boeing 737 MAX 8 reaches 110 mpg per passenger.

This seems counter-intuitive. All other things being equal (and transatlantic distances would equalize many of them) -- shouldn't the larger plane should be more efficient?

This whole article notes the "myths about air travel" and I have to admit that I'd always believed that larger planes were more efficient per passenger mile.

Perhaps there is something unique to the the A380 and 737-Max 8 that makes the comparison incorrect? Is it related to aircraft utilization rate or percentage of seats filled -- although these wouldn't be a factor in the mpg per passenger metric?

Note: I am not interested in crew or ground staffing efficiencies realized by a mega plane. Just fuel.


texts: Airliner - "barking dog" after take-off and before landing

texts:
I've always wondered what is that noise. It sounds like a barking dog or an air drill.
Sometimes you hear 4-5 "shots" but last time I flew the noise went on from before take-off to long after we were in the air.

It looks like they are tightening something. Am I correct?


texts: Why is KLAX and KSEA depicted class D in IFR low enroute chart?

texts:
I was looking at ifr low enroute chart and just figured out that KSEA and KLAX are depicted as class D.
Aren't they Class B airports? why do they have D mark?


texts:
The discipline of Flight Test Engineering has existed since at least 1903, but when did engineers identify their work, distinguish their work from other disciplines, under terms that would mark it as Flight Test Engineering?

This may take the form of someone who first used the term flight test engineer or flight test engineering.

Google demonstrates a history of the terms:

Image credit

NATO describes the history of its flight test organization this way:

  Soon after its founding in 1952, the Advisory Group for Aerospace
  Research and Development (AGARD) recognized the need for a
  comprehensive publication on flight test techniques and the associated
  instrumentation. Under the direction of the Flight Test Panel (now the
  Flight Vehicle Integration Panel) a Flight Test Manual was published
  in the years 1954 to 1956. This original Manual was prepared as four
  volumes: 1. Performance, 2. Stability and Control, 3. Instrumentation
  Catalog, and 4. Instrumentation Systems. As a result of the advances
  in the field of flight test instrumentation, the Flight Test
  Instrumentation Group was formed in 1968 to update Volumes 3 and 4 of
  the Flight Test Manual by publication of the Flight Test
  Instrumentation Series, AGARDograph 160. In its published volumes
  AGARDograph 160 has covered recent developments in flight test
  instrumentation.


texts: Is lift/drag the same as coefficient of lift/coefficient of drag?

texts:
I see it being used interchangeably (for example by Airfoil Tools Fusion360 AddIn), so can I just pick an airfoil from the airfoiltools database with a certain CL/CD for my aircraft and assume L/D is the same?
An example airfoil from the database: clarky-il
(I know there is induced drag as well, which is not calculated in the databse)
I know the formulas, so it makes sense to me. Just want to verify there is not something I am not aware of, in case I want to calculate the lift depending on the angle of attack.


texts: Has color vision deficiency ever contributed to any incidents in aviation history?

texts:
I would like to know if there are any official reports pointing Color Vision Deficiency (CVD) as a major contributing cause of an air accident/incident. Not only related to flying but also maintenance or ATC for instace.

So far, I have only come across with FedEx flight 1478, in which a CVD F/O misjudged the PAPI lights. However, the report does not point how severe was the F/O's deficiency (all crew survived the accident). And more important is that the Captain and Flight Engineer (with normal color vision) could neither detect the wrong glidepath.

My final goal is to research the topic of color-blindness in aviation with real case instances and hopefully draw some conclusions about the actual impact of this disease in aviation for candidate's medical certification.


texts: Can I become a pilot if I have a medical/dental problem?

texts: Can I become a pilot if I have a dental problem (I don't have 6teeth I have artificial one)  and I broke my chin bone I have a steel plate there and I really want to become a pilot is this okay? can I still become pilot as I don't have any other defect in my body ?


texts: What are the relative efficiencies of the various stages of a counter rotating propeller?

texts:
After going through the CFD results of a drone project I am involved in, I noticed that the data shows significantly increased (+10%) thrust generation at the second stage of a counter-rotating, 2-stage, ducted fan. Both stages use identical airfoils and spin at the same rpm. They also have low solidity, meaning they look more like propellers than airliner fans, as the blades take up a small proportion of the disc area.

Generally, propellers are less efficient when the incoming airflow has a high velocity, so I would expect, in any N-stage fan using otherwise identical stages, for the N stage to produce less thrust than the N-1 stage, but apparently I am missing something.

In a previous answer here Peter Kämpf mentioned that the first stage of the Kuznetsov NK-12 turboprop pre-swirls the flow to improve thrust creation conditions at the second stage. How does this process work? Does it require a specific design of the stages to work in tandem?


texts: When pilots check in with a different controller, how to reference flight level?

texts:
When pilots check in with a different controller after they are handed off, how do they report their current altitude in flight levels if they are in level flight or a climb / descent? I feel like saying "level flight level" could be misunderstood.

Can pilots omit the "flight level" phraseology in the examples below?

"(ATC Facility) Baron x-ray five x-ray sierra level flight level two-five-zero... " (level flight @ FL250)

"(ATC Facility) Baron x-ray five x-ray sierra flight level two-five-zero climbing flight level three-two-zero..."

"(ATC Facility) Baron x-ray five x-ray sierra flight level two-five-zero descending flight level two-zero-zero..."


texts: Why don't airliners use light strips on physical controls (yoke/stick, throttle and trim) to indicate who has control - pilot or flight computer?

texts:
I've watched a lot of Air Disasters episodes about crashes where pilots thought auto-pilot, auto-throttle, auto-trim were "in control" but they weren't (or vice-versa) due to some innocuous pilot action - like bumping the go around setting. See: https://en.wikipedia.org/wiki/China_Airlines_Flight_140
From a Human Factors engineering perspective, it seems that it should always be obvious who has control of the various flight controls. One simple option is to put light strips on each physical control (yoke/stick, throttle, trim) to indicate who "has control" - the pilot or the flight computer.  If the throttle levers light strip is green, auto-throttle has control.  If the light is off, the pilot has control of the throttle. This may seem a bit simplistic for normal aircraft operations but in times of high stress such a simple system might make a difference - preventing a crash.  Lights like this would of course need to adjust to the ambient light so they're not glaring during night yet visible in bright daylight.


texts: What might a pilot mean by "uncontrollable"?

texts:
The air safety reports from FlyDubai aircrew leaked to the Guardian contain some alarming stories about crew rostering, tiredness and duty times, but another one caught my eye, a description of an encounter with severe clear air turbulence on a flight from Moscow to Dubai (search for 511 VKO-DXB):

  Aircraft was uncontrollable at time for 10-15 seconds every now and then. Total duration probably around one and half minute.

What does the pilot mean by uncontrollable? That the aircraft wasn't responding to commands and the crew were helpless passengers, at the mercy of the weather, and that everyone survived simply because it didn't go on long enough to tumble the plane out of the sky? Or that it was just being a bit difficult?


texts: What happens to #2 if a formation flight violates a FAR?

texts:
In a formation, it's generally accepted that the lead pilot is responsible for safety of flight and navigation.  #2 is, colloquially, responsible for not hitting lead.  That is to say, in close formation, you never take your eyes off lead.  In many situations, #2 may not even be in radio communication with lead or monitoring ATC frequencies and his overall situational awareness will be degraded.

If lead, who is responsible for navigation, takes the flight into protected airspace (i.e, flies into Class C airspace without first establishing two-way radio communication) would both pilots be violated, or just lead?

For clarification:

The regulations governing formation flight are pretty sparse.  FAR 91.111, 91.146 and 91.153 are the only mentions of formation flying in the regulations.  There is no requirement for communication during the flight - 91.111 just requires that all pilots agree to operate in formation.  It is not unusual in a formation flight for lead to be on one frequency (talking to approach), and the wing to be monitoring another (or not monitoring at all).  Most communication is done via hand signals.  I do know that ATC treats formation flights differently - they effectively treat it as one aircraft (ATC Manual 2−1−13).  If the flight is cleared to land, both aircraft a cleared to land - #2 does not need to acknowledge.  Hence the question who is responsible if the flight (a single aircraft in the eyes of ATC), violates an FAR?


texts: 1.VRB02KT: Is it varying more or less than 180°? 2.VRB03KT: Is it surely varying more than 180°?

texts:
Based on the following ICAO Annex 3 criteria for the use of the abbreviation VRB (not FAA, which is different and evident):

when the total variation is 60° or more and less than 180° and the wind speed is 3 kt or more, such directional variations shall be reported as the two extreme directions between which the surface wind has varied

when the total variation is 60° or more and less than 180° and the wind speed is less than 3 kt, the wind direction shall be reported as variable with no mean wind direction; or

when the total variation is 180° or more, the wind direction shall be reported as variable with no mean wind direction"

I bring up the following QUESTIONS

Based on these criteria, is there a way to identify if a variable 2KT wind is varying less or more than 180° when the indication is just VRB02KT?

If it were varying less than 180° but at least 60° or more, would it be possible to measure its mean direction and direction range despite its low intensity of just 2KT? E.g. 15002KT 110V200.
If not, it brings me back to my first question, what is the actual variation of a VRB02KT, less or more than 180°? Could I just answer impossible to specifically tell, but it is surely 60° or higher, otherwise the mean direction would be possible to measured, even at only 2KT. E.g. 15002KT

If the wind intensity following a VRB indication is 3KT or more, can I assume it is varying more than 180°? Since this excessive variation in direction (not the relatively low intensity of 3KT) is the reason why the station can't measure the mean direction precisely.

E.g. VRB03KT would mean varying by more than 180° (not 60° or more, and less than 180°) with an intensity of 3KT (which would be strong enough to provide feasible conditions for measuring the mean direction, if it wasn’t for its excessive variation in direction above 180°).


texts: Does an aircraft like the Airbus A-320 have external sensors to detect damage to the aircraft?

texts:
I read a news item recently . According to the article, the wingtip of an Airbus A-320 collided with the left wing of an A-330 while on the taxiway at Mumbai airport. The A-320 (VT-IFP) experience a damaged sharklet. The collision was observed by a passenger and then shared with the aircraft staff (flight attendants I guess) who informed the captain. The plane was led to a hangar, passengers de-boarded and sent on other plane/s by the airline.

What I want to know is: aren't there any sensors which can detect an impact and give/share that information to the pilot? I do understand that the airplane takes a lot of jerk and movement during takeoff and landing as well as during turbulence.

But when damage as such as the one described above happens, why isn't there some automated system that could inform the pilot instead of having to rely on a passenger's keen eyes?


texts: Can the 787 mini navigation display be controlled independently from the ND?

texts:
Some aircraft, e.g., the Boeing 787 have the option to display a "Mini Navigation Display" on the left Outboard Display Unit, right under the Primary Flight Display:

(image source)

Is the information shown there a copy of the "normal" Navigation Display on the Inboard Display Unit (possibly with a limited set of information?), or can it be fully customized by the pilot independently of the other ND? (I'm not talking differences between left and right side PFDs/NDs, but I'm talking only one side, e.g. the left side only).

With "copy of normal ND" I specifically mean ALL updates to the ND via the EFIS control panel are reflected on both the ND and the mini ND. This would include wx, airports, range, modes (plan, arc, rose), etc.

In case of independent controls, how can the pilot customize the mini ND?


texts: How far ahead will ATC issue runway crossing clearances at controlled FAA airport?

texts:
In past years it was common to get a taxi clearance that would include all required runway crossings. This was true even if there were several runway crossings over a long distance.

Now it seems that ATC has limits on how far ahead they can issue runway crossings. What are the ATC limits on taxi clearances that include runway crossings?


texts: What is the difference between types of propeller?

texts:
I have been noticing almost every Multirotor vehicle uses a single thin double-bladed propellor on each axis. And yet clearly, there are some that do not fit the norm.

Can someone explain what the effect of each of these changes would do to a normal quadrocopter?

1) Adding more Propellors.

2) Adding more Blades on each Propellor.

3) Replacing all Blades with Wider Blades.

4) Making the angle of each blade steeper.

5) Replacing propellors with Contra-rotating propellers

6) Spinning Propellors faster


texts: What are the specifications for the CFE738-1-1B?

texts:
I'm designing an aircraft for fun, and I've selected a CFE738-1-1B as the engine. It's never going to fly outside of X Plane, but it's still fun, so I'd like to make the X Plane version as realistic as possible. This means that I need to know a bit about this engine (it's used in the Falcon 2000, so any Falcon 2000 pilots, not including anything after the 2000 like 2000EX, you would be very helpful). What I need to know and haven't been able to find on the internet is the following:

Minimum N2 to avoid a hot start.
Length of time it takes from beginning of engine start to idle fuel flow.
Time from idle throttle to max throttle.
Time for N1 to spool up to max from idle.
Thrust curves.
SFC at half thrust at 0 and 40,000 feet.
Fuel flow at flight idle.

Any help much appreciated (Don't feel obligated to answer all of these in the same post)!


texts: Why don't piston engines require as heat resistant materials as jet engines?

texts:
Piston engines often get away with using aluminium as their heat exposed material, while even the early jets required inconel to operate.
Is that because the combustion takes only, for example, half of the time for two stroke engines hence half the temperature?
Still compression ratio of a typical two stroke is twice higher than early jets, while the melting point of aluminium is more than twice lower so it doesn't add up, as if there was another reason for their higher heat durability


texts: How does a weak shock-wave boundary-layer interaction create wave drag (other than through direct shock losses)?

texts:
I'm trying to understand the physical cause of wave drag, beyond the simple statement "the presence of shockwaves increases the drag".

As far as I understand, in the case of a weak BLSWI (so without separation), the drag increase is due to:

Direct shock losses (momentum deficiency of freestream flow through shockwave)
A change in the state of the boundary layer due to the compression waves in side the BL

But how exactly does the second point work? If the BL becomes thicker after the SW, wouldn't that mean that the drag decreases because the velocity gradient and therefore the shear stress decrease?

I feel like I'm missing some tiny aspect...

Edit: I've found the following statement in this report, which maybe explains my problem better:

  The
  increase
  in
  drag
  occurs
  directly
  because
  of
  the
  wave
  drag
  associated
  with
  the
  presence
  of
  shock
  waves.
  However,
  the
  drag
  also
  increases
  because
  the
  boundary
  layer
  thickness
  increases
  due
  to
  the
  sudden
  pressure
  rise
  on
  the
  surface
  due
  to
  the
  shock
  wave,
  which
  leads
  to
  increased
  profile
  drag.
  Lynch
  has
  estimated
  that
  at
  drag
  divergence
  the
  additional
  transonic
  drag
  is
  approximately
  evenly
  divided
  between
  the
  explicit
  shock
  drag
  and
  the
  shock
  induced
  additional
  profile
  drag

Why does the increase in BL thickness cause more drag? Shouldn't the velocity gradient at the wall reduce, leading in less shear stress? Or should I see it in a way that the already turbulent BL "takes up more energy in its vortical structures" from the flow, due to the increase in thickness?


texts: What is "airspace underlying a Class B airspace area designated for an airport"?

texts:
For the purposes of airspeed restrictions within airspace, the FAA regulations list the following area description (emphasis mine):

14 CFR 91.117 (C)

  No person may operate an aircraft in the airspace underlying a Class B airspace area designated for an airport [...] at an indicated airspeed of more than 200 knots (230 mph).

Should we understand the described airspace to be any and all airspace underlying a Class B where that specific Class B is designated for an airport? Or, should we understand the described airspace to be any and all airspace designated for an airport (Class C, D, or E) which is underlying a Class B?

Are there letters of interpretation or other regulations which clarify the grammatical ambiguity of this regulation?


texts: How many pilots are required in an Airbus A380?

texts: Is it possible for one single person to fly, maneuver and land an Airbus A380 by him/herself?


texts: What is meant by Manual Tuning of ADF/NDB using BFO?

texts:
As NDB transmission is either N0NA1A(requires BFO to be turned on for Manual Tuning, Identification and Monitoring) or N0NA2A(BFO turned on only for Manual Tuning).

My question is what exactly is meant by Manual Tuning and how does BFO help in Manual Tuning of ADF/NDB.

Thank you

How (and when) to use the BFO button on an ADF? This post explains when to use it, But I want to understand the concept of Manual tuning and Why N0NA2A needs the BFO turned on for Manual tuning?


texts: Has there ever been a plane not controlled from the nose?

texts: Has there ever been an airplane where the pilot, or cockpit were not located near the nose of the airplane?


texts: Why don't plane wings start at the front of a plane and end at the back?

texts:
This is what some people think the SR 72 will look like.

If a plane wing was attached to the whole fuselage, couldn't it have a shorter wing span? If it had a shorter wingspan it would be less of a lever so could be less strong and therefore lighter. I don't mean a blended wing.


texts: Was John F. Kennedy Jr.’s accident airplane equipped with an autopilot?

texts: JFK Jr.’s crash was attributed to failure to maintain control due to spatial disorientation. Could this be explained by his Piper Saratoga N9253N having no autopilot?


texts: Is it enough for crossing/ascending/descending IFR-flights to adhere to the separation minima?

texts:
The separation minima in Europe are in general 5NM lateral or 1000ft vertical. If the safety distance is too small, there is a conflict (loss of separation). When both aircraft are on the same track, the adherance to the minimal separation is relatively easy. But if two trajectories cross the same point horizontally, for example over a beacon, the adherance to the separation minima seems not that easy anymore. The same is true for ascending or descending flights which burst through different flight levels.

Is the adherence to the separation minima for IFR flights enough to avoid airborne conflicts for crossing/ascending/descending flights, too?

If not, what is the minimum distance between two flights in space and time, that precludes all the different possible conflict types [page5]? For example there are local conflicts, which occur, when two aircrafts cross a given point from different directions in under 4 minutes.

This questions refers to the european airspace at best. See the linked question How much is the minimum safe distance between two planes in-flight?


texts: What does it take to turn a 747 around 180 degrees?

texts:
Assume that a 747 is flying at cruising altitude and speed. If the pilot decided (for a presumably good reason), to turn the plane 180 degrees,

How quickly could the turn be completed?
How wide would the turn radius be?
How much altitude would be lost, if we're not assuming a level turn?

EDIT: I learned something new from both of the great answers below. I accepted the one that was easier to follow. Since both answers assumed a level flight, I have added a #3.


texts: What is the difference between RVR and visibility?

texts: What is the difference between Runway Visual Range (RVR) and visibility? Looking at the definitions, both RVR and visibility tells the pilot whether they have enough visibility to land on the runway or not? Are they measured using different instruments or is there something else that I missed out?