texts: During WW1 Zeppelins began their missions with Hydrogen cells at 33% full. How did this provide enough lift to get off the ground?

texts:
During WW1 U Class Zeppelins had hydrogen cells that contained 55,795 cubic meters of gas.

According to Peter Kämpf's excellent, detailed explanation of Zeppelin mechanics they began missions with their hydrogen cells filled with roughly 33% hydrogen.  The rest of the volume contained air.  Because hydrogen expands as air pressure falls starting at 33% allowed Zeppelins to reach high altitudes without rupturing their gas cells.
However given the constants below I'm not sure how 33% hydrogen produced enough lift to get a Zeppelin off the ground.
Sea Level, 0 Meters:
Temp Celsius: 15°
Temp Kelvin: 288.15°
Pressure Pascals: 101,325
Gas Moles per cubic meter: 42.29
Air mass per cubic meter: 1.221 Kg
Hydrogen mass per cubic meter: .085 Kg
55,795 cubic meters of gas cells * 33% full = 18,412 cubic meters hydrogen
18,412 cubic meters of displaced air mass = 22,481 Kg
18,412 cubic meters of hydrogen = 1,566 Kg
Useful lift = 22,481 kg - 1,566 kg = 20,915 Kg
The empty weight of a U class Zeppelin was 25,750 Kg.  That's without fuel, ballast or bombs.  If useful lift was less than empty weight how did it take off?
At 5,000 meters altitude useful lift stays the same because although the hydrogen cells expand and displace more air the atmosphere is less dense and has less mass per cubic meter.  Lift at 0 meters altitude is the same as lift at 5,000 meters altitude.
Another detail I found interesting is that according to Wiki the U Class Zeppelin produced 64,750 Kg of useful lift.
When I plug in numbers at sea level that suggests that the gas cells were filled to the top with 100% hydrogen.
55,795 cubic meters of gas cells
55,795 cubic meters of displaced air mass = 68,126 Kg
55,795 cubic meters of hydrogen = 4,743 Kg
Useful lift = 68,126 Kg - 4,743 Kg = 63,383 Kg
However if the hydrogen cells were filled to 100% it couldn't climb without bleeding hydrogen all the way up.  It should be noted that at 5,000 meters the air is thin and useful lift drops by almost half.
Altitude, 5,000 Meters:
Temp Celsius: -17.5°
Temp Kelvin: 255.65°
Pressure Pascals: 49,586
Gas Moles per cubic meter: 23.33
Air mass per cubic meter: .674 Kg
Hydrogen mass per cubic meter: .047 Kg
55,795 cubic meters of gas cells at 100% full
55,795 cubic meters of displaced air mass = 37,605 Kg
55,795 cubic meters of hydrogen = 2,622 Kg
Useful lift = 37,605 Kg - 2,622 Kg = 34,983 Kg
34,983 Kg of lift is maybe barely enough to stay afloat with fuel, ballast and bombs.
But even if they did it this way when the Zeppelin descended the Hydrogen cells would be mostly empty and would fill with air causing the ship to gain weight and crash.
At 0 meters
55,795 cubic meters of gas cells filled with 66% air = 36,825 cubic meters
36,825 cubic meters of air mass = 44,963 Kg!


texts: Why do new helicopters have rotor blades with swept tip?

texts: Many new helicopers have rotor blades with swept tip. Why? Acoustic? e.g.


texts: When do commercial aircraft tail numbers change?

texts:
Each (large, commercial and most other) aircraft has a registration number, painted or stickered on its hull: the tail number.

I was under the false impression that tail numbers don't change, and that a number identifies an aircraft until it's decommissioned. That's not true, apparently! This article, for example, explains how new owners may want to change numbers when they buy aircraft.

My question: Under what other circumstances do tail numbers of commercial aircraft typically change? Other than changes-of-ownership?

Notes:

I'm not asking about considerations for changing tail numbers during ownership changes. That's covered.
Of course, someone can arbitrarily change a tail number on a whim, but that's probably very rare; I'm asking about somewhat-common situations in which tail numbers are changed.

Motivation: Want to be able to use tail numbers to distinguish different aircraft, but need more information to qualify that assumption. So, I realize different owners may invalidate the assumption; looking to qualify it further.


texts: Do planes return to service after non-fiery crashes?

texts:
A Turkish Airlines flight recently ran off the runway and ended up on its belly in a field. The landing gear were damaged, but the plane didn't burn and the fuselage remained intact.

Are planes involved in this sort of accident repaired and returned to service, or are the planes usually scrapped?


texts: Something I have wondered about recently, since the advent of ICBM's what is the point of long range bombers like the B2? I understand they have longer range and can carry more payload but wouldn't they be easy prey for fighter jets or SAM's? Surely missiles are a much more attractive option. I don't get why the effort and expense goes into bombers?


texts: What is the call for when an enemy air-to-air missile has been fired?

texts:
In a scenario where a large multi-crewed aircraft was being attacked by a fighter that launched an air-to-air missile what would the call be that would alert the pilot that a missile was in the air and potentially tracking them.  I know the term 'Rifle' but I always assumed that meant a friendly missile in the air, is there a specific call for an enemy missile?

Also is there a call for a SAM launch?


texts: Why would a jet engine use cannular combustors if the annular design is superior?

texts: Why are cannular type burners used in aircraft engines if annular type have more advantages over it?


texts: Why are months (e.g. December) used to notate a runway?

texts:
I'm writing a report on runway quality and I've stumbled onto a weird qualifier in the data. I understand that runway 17/35 indicates which direction the runway is facing based on magnetic heading.

  RWY_ID 17/35 17/35 26-Aug 14/32 30-Dec 28-Oct 21-Mar 13/31

What does 21-March mean for example?


texts: Could liquid alkali metal fuels be used for ramjet/scramjet propulsion?

texts:
In particular, I'm thinking about lithium, but sodium could be considered as well.

Lithium has low molecular weight, very high propellant density, and low melting point. At sufficiently high temperatures (above 500 degrees Fahrenheit) it ignites spontaneously in air with explosive force.

A lithium scramjet/ramjet would require an onboard power supply to heat the fuel to liquid and then pump it into the combustion chamber. The idea is that the combustion chamber would need to be hot enough so that the lithium droplets would quickly evaporate and ignite making the mixture hypergolic.

I'm surprised that I have found no current R&D into alkali metal fuels for rocket propulsion(let alone hypersonic propulsion). It seems to me that to make longer range hypersonic flight possible, exotic fuels will be absolutely necessary.


texts: Do airport fire departments have to have airstairs?

texts:
On the video of the JetBlue 292 landing (at 4:27), one of the first emergency vehicles to approach the Airbus is a fire department airstair. I've never seen a fire department with its own airstair. I found a standalone picture of LAX's Stair 80. I don't see a stair among ORD's fire apparatus but DFW and DEN have them. Why do some airports apparently have airstairs but others don't?

The only reference I found from the FAA is a 2012 article about New Large Aircraft (e.g. A380). Relevant passage:

  Several airports are now acquiring mobile air stairs and modifying
  them for ARFF use with hand lines, ventilation equipment and fire
  fighting tools. Some European airports have even acquired customized
  platform vehicles for rapid firefighter access into aircraft. Ideas
  being discussed are various air stair designs, scissor lift catering
  style trucks and modified ARFF vehicles with stairs or ladder that
  will accommodate all sizes of aircraft, including double deck designs.

I found this manufacturer page touting the importance of fire department airstairs. So obviously they exist. Here are my questions:

Does the FAA require fire department airstairs?
What are the primary uses? Getting passengers out or getting firefighters in?


texts: How do turbochargers aid engine performance as density altitude increases?

texts:
How do turbochargers improve engine performance at high altitudes / density altitudes?
Could you also address how this benefit could become a liability at low density altitudes, for example when the density altitude is negative?


texts: Is there a relationship between turbojet engine rpm (N1 & N2) and fuel consumption rate?

texts:
Image Source

N1 and N2 are the rotational speeds of the engine sections expressed as a percentage of a nominal value.

It is similar to the revolutions per minute (RPM) of a piston engine, expressed in percentage instead of in the actual rate of rotation.

They are different because they are characteristic on two-spool engines (see the figure below). The first spool is the low pressure compressor (LP), that is N1 and the second spool is the high pressure compressor (HP), that is N2. The shafts of the engine are not connected and they operate separately.

Image Source


texts: Is is possible to land a midsize commercial plane on an Ford Class aircraft carrier?

texts:
I'm story-boarding a novel. I'm toying with the idea of contriving a situation in which a midsize commercial aircraft is forced to make an emergency landing on an aircraft carrier. I read here that the largest plane to land on an aircraft carrier is a C130 Hercules, which it did as a series of tests. Its maximum weight when performing these tests was 121,000 lbs. At this weight, it required only 460 feet to land. And it did so without use of a tailhook, or any other arresting mechanism. The brand new Gerald R. Ford class carrier is 1,106 feet long. The landing strip on the carrier is somewhat shorter. I couldn't find numbers on this, but from photos, I would estimate that the landing strip is a little more than 800 feet long. Which leads me to my first question:

In an emergency situation, could an aircraft use the full length of the aircraft carrier's deck to land?

Assuming the answer to the above is yes, this means that our commercial aircraft has somewhat more than twice the distance to make its landing than the C130 did. Let us assume that the commercial aircraft is a B737 Classic, weighing aobut 140,000 pounds, just a little more than the C130 did during the tests. This leads me to my main question:

Could a 737 Classic safely make an unarrested emergency landing on a Gerald R. Ford Class aircraft carrier?

By safely, I mean without any passenger death. I expect that any such landing attempt would result in significant damage to the aircraft and the carrier. On one hand, the numbers seem to suggest that if a C130 can do it, so could a B737. On the other hand, I would expect that the C130, as a military aircraft, is more robust than a commercial aircraft, and perhaps able to better meet the conditions required to land on a carrier.

Also, I realize that in an emergency situation it may be safer for the aircraft to make a water landing near the carrier, and then for the passengers to evacuate onto inflatable rafts, finally to be brought aboard shortly thereafter. I will have to invent a situation which requires the plane to land on the carrier.


texts: What are good strategies for the "impossible turn"?

texts:
For reference, I fly a Cessna 172.

I've read about a couple of different strategies for the impossible turn (attempting to turn back to the airport after engine failure at low altitude).

The first strategy is the one I've heard most commonly on aviation websites and videos: that is, essentially, maintain a best glide and try to make the turn as quickly as possible without stalling.  Unfortunately, a slow turn also means you'll have to turn a little more than 180 degrees to get back to the runway.

The second strategy I've heard is not generally mentioned in the typical safety videos (at least that I've seen). A former flight instructor had mentioned that you could complete the impossible turn by pushing the nose down and using the additional airspeed and downward angle to execute an extremely sharp turn that would keep you closer to the runway; when you come out of the turn, you won't have to worry as much about lining back up with the runway.

Strategy 2 is clearly more risky, at least for someone who has not practiced the maneuver, so that could explain why I don't see it mentioned in most safety videos. I was wondering if anyone here had an opinion on either maneuver (or other options) for executing the impossible turn and, if possible, links to literature explaining it.

Thanks in advance.


texts: How did the long loop of tape in a magnetic cockpit voice recorder work?

texts: How was the continuous looping of tape in an old-school mechanical cockpit voice recorder physically implemented? 30 minutes seems like a lot of tape to loop continuously, did it move more slowly than a normal audio tape?


texts: How should one fly the entry procedure to an approach when the hold is not aligned with the outbound course?

texts:
Consider the following NDB DME approach into runway 08 at Jersey (EGJJ):

Let's assume we are coming in from the North and are currently cleared direct to the JW NDB flying inbound on a 180° track. Now we are cleared for the NDB DME approach. How should the entry into this approach be flown:

When reaching the NDB, immediately turn right to intercept the 246° outbound course. This seems to be prohibited by ICAO PANS-OPS because the difference between my inbound course and the outbound course is larger than 30°:

  Unless the procedure specifies particular entry restrictions, reversal procedures shall be entered from a track within ±30° of the outbound track of the reversal procedure. However, for base turns, where the ±30° direct entry sector does not include the reciprocal of the inbound track, the entry sector is expanded to include it.

(ICAO Document 8168, Vol 1 §4, 3.3.3.1)
Enter the hold with a direct entry and immediately follow the Alternative procedure by extending the outbound leg of the hold. This seems to be the best option, but I'm not sure if this would be expected without being explicitly cleared for the alternative procedure.
Enter the hold with a direct entry and after one racetrack when crossing JW fly a course reversal / alignment turn to the left. As far as I understand, this would be the normal procedure if the hold were aligned with (or within 30° of) the outbound course since no course reversal would be required any more. But in this case, it seems weird since there is nothing in the chart about an alignment turn.
Or maybe something else?

Here is what I imagine the options 1-3 to look like:


texts: On a "Visual Approach", do I execute a "missed approach" or do I go around?

texts:
Let's say the weather is a little above VFR minimums (let's say it is 1700ft and 3SM).

The approach controller vectors me on to the final, and then clears me for a visual approach. For some reason (such as bad crosswinds), I feel like aborting my approach.

At this point, am I allowed to "go around" or do I have to execute a missed approach procedure (if so, which one?) unless advised otherwise by tower?

And what if it was an uncontrolled airport whereby I'd have to make this decision myself before contacting approach again?


texts: Which types of aircraft are required to carry ELTs?

texts:
According to regulations and recommendations from the FAA, ICAO or other aviation organisations, what types of aircraft are required to carry Automatic Fixed Emergency Location Transmitters (ELT(AF)) devices? In particular, is it required of commercial transport airliners?

CAA (and I guess other aviation organisations/regulators) group aircraft into several categories:

General Aviation (GA) - personal aircraft etc.
Business Aviation - executive jets etc
Commercial Air Transport / Public Transport - Scheduled passenger airliners etc.

AOPA say

  ELTs are emergency transmitters that are carried aboard most general aviation aircraft in the U.S.

(my emphasis) - note GA, not all aircraft.

CAA refer to ICAO Annex 6

  Aeroplanes - ICAO Annex 6, Part II
  6.12.3 From 1 January 2005, all aeroplanes operated on extended flights over water as described in
  6.3.3 b) and when operated on flights over designated land areas as described in 6.4 shall be
  equipped with one automatic ELT. [i.e. designated KK(ii) in the Air Navigation Order]

  6.12.4 Recommendation. - All aeroplanes should carry an automatic ELT.

But I can't find an annex mentioning ELTs at www.icao.int.

So, I'm not sure whether all airliners are required to carry ELT(AF)s and if so, by whom.


texts: Did WW2-era aircraft have constant-speed or variable-pitch props?

texts:
This is slightly related to my other question on variable-pitch controls.

I want to know if WW2-era aircraft typically had variable-pitch or constant-speed propellers. Variable-pitch lets the pilot adjust the propeller blade pitch. "Constant speed" is the same as variable-pitch, but the engine does it automatically to keep the best performance at various airspeeds. This also lets the engine keep a constant RPM so it can always run at its optimal RPM, also increasing efficiency.

Anyway, were such things seen in WW2? Were they the norm, or the exception? Did single-engine aircraft have them, or were they more common on multi-engines?

I'm interested in all the nations who made aircraft, especially USA, UK, USSR, Germany, and Japan. And I'm interested specifically in the combat aircraft, like fighters and bombers, not necessarily the civilian transports of the era. This will give us a good idea if the extra complexity and weight was acceptable for combat aircraft of the era.


texts: How can an aircraft hover almost vertically?

texts:
(Source: https://fat.gfycat.com/)
The aircraft in this GIF (although being an RC plane) seems to be flying vertically, just meters above the ground. How is this possible? How is it possible to control it in this scenario? Would this be possible with a real aircraft?


texts: What is the difference between flaps and slats?

texts:
I have heard pilots talk about flaps and slats, seemingly interchangeably.

Is there a difference between a flap and a slat or they are the same thing?


texts: Do aircraft owners need to purchase insurance?

texts: As far as I know, most (or all) airplane owners purchase insurance that covers liability, if nothing else. Good idea or not, is aircraft insurance legally required in the US, in the way that automobile insurance is required?


texts: Is there a modern day "replacement" for the de Havilland Beaver?

texts:
Is there a modern day equivalent or replacement for the Beaver's Payload, STOL and floats capabilities? By replacement, I mean that it can fly into the same airstrips under the same weather with the same load.
Is there any modern (still manufactured) airframe that wouldn't leave a seasoned Beaver bush pilot wishing for their old Beaver back?
In all of the time since that plane was designed, has something else has been designed and continues to be manufactured that can be called an upgrade without getting "bigger"? IE, has:

floats
a shorter or the same takeoff and landing roll at the Beaver's
max useful payload
the same or less stall speed with fully extended flaps
a same or less wingspan (negotiable if it's within 2 or 3 feet)

The motivation for the question is that less than 10 years ago, I remember a float plane flight out of Juneau, AK that I was on was flown by a Beaver still running a radial engine. I was amazed that something designed so long ago was still apparently considered  the "best" option for that carrier. Of course, the Beaver is now one of my favorite airplanes, but I am still amazed by the challenge it must be to find parts and maintain an aircraft of that age in the corrosive saltwater environment of SE Alaska.


texts: How are wooden aircraft protected from lightning strikes?

texts: A wooden aircraft is not conductive and if a lightning hits the wood it will instantaneously ignite. How would you protect a wooden aircraft from this occurrence?


texts: Why does the KC-46 use two sensors for MCAS when the 737 Max doesn’t?

texts:
this article states

  The KC-46 has a two-sensor MCAS system, which “compares the two readings,” the Air Force said.

I’m aware that the 737 uses two sensors and always has, but the computer reads them simultaneously based off which pilot is flying the plane. So if the Captain is flying it’s reading data from the left side, correct?

At this point I’m assuming Boeing’s decision to pull data from one sensor was to reduce the workload and make for a earlier introduction?


texts: Why does the 737-300 outflow valve indicator give different readings?

texts:
The 737-300 outflow valve opens and closes in manual mode under AC or DC side. While in DC, the indicator is accurate, but when it's in AC mode it reads open when closed.
Does the outflow valve have separate potentiometers for indicating both AC and DC?


texts: Will Thrust on Rotor (Main) increase with altitude?

texts:
Can some one please let me know,if the thrust required on the rotor head increases with the increase in altitude in an Helicopter or decreases with increase in Altitude?.

Thanks in advance,
Pawan


texts: Flight Plan - Rights of use and distribution to third parties

texts:
Currently we have in mind a meteorological project, specially designed for pilots and aviation professionals, for which, the only thing that we currently lack is to have the flight plans. It seems to be (as Eurocontrol tells us) that flight plan information is only distributed to airlines and air traffic control companies, not to third parties. Therefore, the only thing that remains is for the pilot to provide us with the flight plan.

What use rights does a flight plan have? Is there a problem in which the pilot shares this information with third parties?


texts: Does the wifi uplink antenna affect aerodynamics or efficiency?

texts:
The wifi uplink antenna on airliners seems like a quite aerodynamically inefficient hump, just sticking up into the airflow above the main cabin. If it added even 0.1% more drag, I don't see how it would be financially viable.

(Photo by me, released to public domain)

How much does that big antenna drag? Why not either smooth it out forward and aft or build it into the body of the plane?


texts: What are these strange blades behind the N1 fan in a Boeing 747-8 engine?

texts: It looks like a second fan or something.


texts: How does a U.S. military air traffic controller become a civilian air traffic controller?

texts: If a person is working as a United States military air traffic controller and then they get discharged, do they have to go through additional training and tests to work as a United States civilian air traffic controller? or do they just get hired, without any additional training and tests?


texts: What would happen if ultralights had mountain bike style treaded tires?

texts:
What would happen if ultralights had off road treaded tires?

Mountain bike tires are made for going off road through mud, etc.  They have voids between the tire lugs to clear mud etc.

Why not off road going airplanes?

I assume the reason is, the lugs would catch air and start the tire spinning during flight?

Is this correct?

Or is it just a drag thing?


texts: How do plane landing-gear tyres roll before take off?

texts: How do plane tyres roll? Are they equipped with special engines like cars or are they rolling using the plane flying engines? Or can both methods be found with different constructors?


texts: Why is the APU located in the tail for almost all commercial aircraft?

texts:
I know there are planes whose APU (Auxiliary Power Unit) is located elsewhere, but for the most common commercial jet aircraft (A320, B737, B747, A330,...), the APU is located in the tail.

Is there a good reason for that (place, weight, airflow,...)?


texts: What is the lightest jetliner out there?

texts: What is the lightest commercial jetliner out there? I was thinking of something like a Embraer E170.


texts:
I would like to know if creating a strong back pressure within a propeller duct will enable an aircraft to attain a higher altitude.

Please reference the conceptual drawing below.

This is showing a ducted propeller with the addition of a centrifugal blower/compressor. This hybrid propeller would consist of four parts sandwiched together and then welded in order to make one piece that rotates as one unit.

The purpose of the compressor is to create a strong back pressure within the duct which should enable the propeller to produce more thrust/lift and should enable the aircraft, particularly a helicopter or drone, to attain a higher-than-normal altitude. I believe that the merging of the airstream from the propellers with the airstream coming out of the compressor is what will create the strong back pressure throughout the duct.

I think one key application for this type of 'pressurized' ducted propeller would be high-altitude rescues such as rescuing stranded mountain climbers, or reaching an airliner that went down up in the mountains above the reach of most helicopters.

Will creating a strong back pressure within a ducted propeller enable an aircraft to attain a higher altitude?


texts: Why use a single engine plane instead of a multi engine one for a long range flight record?

texts:
Tupolev ANT-25 was designed specifically for setting flight range records. In 1937 two flights from Moscow, Soviet Union to USA via the North Pole happened - one covered 9130 kilometers and finished in Vancouver, Washington and another covered 11500 kilometers and finished near San Jacinto, California.

ANT-25 had a single V-12 piston engine. This sounds kinda not very redundant - should a single engine fail while the plane was crossing Arctic there was good chance the flight would end there and maybe the crew would not be rescued because simply reaching there would be problematic.

Why was a single engine airplane selected for this specific task where reliability was very important?


texts: What is allowed with the new EASA SPL license?

texts:
Are you allowed to fly for profit with SPL? If I have understood correctly, SPL is to LAPL(S) as CPL is to PPL, but with no extra requirements over LAPL(S), but I have problems believing this.

Assuming I have understood the rules correctly, I can upgrade my MGPL to LAPL(S)+TMG and therefore to SPL+TMG with no extra effort. After doing the conversion and flying PIC for 75 hours, I would legally be allowed to ask the passengers to pay for my flights. This seems to be too far from the current rulings that I have trouble believing this.

SPL = Sailplane Pilot License
LAPL(S) = Lightweight Aircraft Pilot License (Sailplane)
CPL = Commercial Pilot License
PPL = Private Pilot License
TMG = Touring Motor Glider


texts: What is the difference between Vno and Va

texts:
What is the difference between the maximum structural cruising speed (Vno) and the manuevering speed (Va)?  Can you also please explain how these speeds are calculated?

I do understand that Va is set to where the wing will stall before the plane will go over its G limit but what does Vno mean?


texts: What is Class F airspace, and why is it not used in the US?

texts: I've read that ICAO defines Class F airspace but the FAA has chosen not to use the airspace class in the US. What is the ICAO definition of Class F airspace and how does it differ from other airspace classes? What countries use Class F airspace? Why does the FAA only use A-E and G?


texts: What are the procedures to get a revoked mechanics certificate reinstated?

texts:
At one point I held a mechanic's certificate. However due to poor judgement it(the certificate) was revoked due to a narcotics conviction.

How can I get it reinstated? Is there refresher classes?


texts:
Today, I flew on a commercial airline European flight. Upon arrival, as I was walking from the airplane to the arrivals gate (across tarmac, no jetways), a yellow car labelled "Airside inspection" sped up to the plane with blue lights and sirens wailing.

An officer ran out and blocked people from exiting the plane (some had already gotten out and were allowed to leave). Then, other two people in orange jackets followed him into the plane.

Google searches for airside inspection don't produce a lot of material, but from what I could understand these people are charged with checking that the runways etc. conform to safety standards.

What reason would they have to approach a plane, sirens on, and block the passengers?


texts: Why can't ramjet diffusers be stacked to achieve a good overall pressure ratio?

texts: The problem with ramjets is that they only gain efficiency similiar to turbojets at speeds above mach 2. However, ramjets can operate at speeds of a few hundred km/h. Why therefore cant ramjet diffusers be stacked, analogously to compressor stages in a turbojets to achive a high compression ratio and efficiency at low speeds?


texts: Does the 787 gust alleviation system make a more comfortable ride or for a more stable aircraft?

texts:
The 787 active gust alleviation system, similar to the system used on the B-2 bomber, improves ride quality during turbulence.

Ride quality in a B2 bomber means a more stable weapons platform.

Ride quality in a 787 means passenger comfort.

(I must add that I have never flown in a 787.)

Is the 787 more comfortable than a normal plane of similar size?


texts:
What is this sheet on a Super Étendard ?

As seen on


texts: Are there any heavy lift jets (like Stargazer) with zoom climb (like Ye-66A MIG-21)?

texts: Are there any intercept jets (that can zoom climb like 1961 April 28 113,891ft Ye-66A Mig-21 Turbojet) built for heavy lift?  I see the Stargazer and Stratolaunch as really slow heavy lift vehicles that cannot zoom climb.  I saw one article about using an F15E as a rocket lifter.  Is it silly to dream of a purpose-built large jet that could carry a large payload (like a Pegasus rocket) and zoom climb to a high altitude (100,000ft) before releasing its heavy rocket payload?


texts: Why are the 737's variable-speed generator drives so unreliable?

texts:
The 737 Classic has two different possible styles of engine-driven generators, distinguished by the generator's drive mechanism: the constant-speed drive (CSD) and the variable-speed constant-frequency drive (VSCF).
The original VSCF drives were very unreliable, failing roughly three times as often as the constant-speed drives.  A 2001 modification programme by Boeing and the generator manufacturer improved this somewhat, but the generator drives remained unreliable enough for VSCF-equipped 737s, even those with modified drive units, to be subject to stricter limitations than other 737s (the United Kingdom's CAA requires them to remain within 45 minutes' flight time of a suitable airport, even if only one of the generators is VSCF-driven and the other has the reliable constant-speed drive; I don't have information on whether other regulatory authorities have similar limitations for VSCF-equipped 737s).
Why are the 737's variable-speed constant-frequency generator drives so much less reliable than the same aircraft's constant-speed drives?


texts: Was there an incident when Airbus autopilot wasn't letting the airplane land?

texts:
I'm trying to track down a story about an incident involving an Airbus airplane my father told me about 25 years ago, when he was working at a Boeing supplier.

Reportedly, what happened was the airplane's autopilot was set to bring them in to a certain airport, and the pilots noticed that it was descending too early.  So, they took over the controls, lined up manually, and at about a hundred feet up, the autopilot wouldn't let them descend further.  So, they did a go-around, tried the approach again, and the same thing happened.  At this point, they diverted to another airport and landed without incident.  Turned out that the airplane's database had an incorrect position for their destination: the plane thought they were overshooting the runway, and wouldn't let them perform what it saw was an off-airport landing.

Was this based on an actual incident, or just one of the "Airbus airplanes don't let the pilot fly" stories circulating among Airbus competitors?


texts: Is it difficult for a GA aircraft to escape a thunderstorm?

texts:
I live in the midwest, and I'm getting ready to start working on my PPL.  For some reason I find myself really nervous about getting into the air and suddenly seeing a line of thunderstorms rolling in from the southwest.  In my mind it feels like a fast moving front would be difficult to escape...

But I wonder if my fear is wholly unjustified.  So I thought I'd ask:

If I'm in a GA plane (like a Cessna 172) and I see a thunderstorms forming to my southwest (lets say 20 miles away),  how much time, in general, am I going to have to get on the ground before the storm gets to me?  If I turn away from the storm, and start looking for an airport, will I be able to put distance between me and the storm to buy time to get on the ground?

Just to clarify before I get a lot of "that's what preflight briefings are for", this questions assumes there was a preflight briefing.

But thunderstorms have this tendency to show up unannounced where I live (or at least it feels that way to me), and that's what this question is about. What do I do when a thunderstorm, that I wasn't aware was going to be there, suddenly shows up on the horizon headed right for me?


texts: How can I get General Aviation flight data on smartphone and/or tablet?

texts:
Is it possible to in-flight receive navigation data on an electronic device (like smartphone and/or tablet) present in the cockpit?
I refer to General Aviation aircraft and navigation data like airspeed (not groundspeed), GPS and AHRS data.


texts: What determines the maximum ground speed of hot air balloons?

texts: I am wondering how the ground speed of hot air balloons is controlled. The wind is obviously going to have a large influence upon the ground speed, but apart from wind effects, do hot air balloons have the ability to control their ground speed? If so, how? Is there a maximum limit to the ground speed of a hot air balloon? What factors contribute to this speed limit?


texts: How long after the last departure shall the airport stay open for an emergency return?

texts:
For how long after the last take off for that day, will an airport stay open for emergency return of that last departed aircraft? Where can I find that recommendation?

To clarify: an airport needs to be closed during the night due to work-in-progress on a runway, so it can't stay open 24/7 for emergency landings.


texts: Where can aircraft carriers carry out air operations?

texts:
I'm interested in any military or civil airspace regulations about where aircraft carriers are allowed to launch and retrieve aircraft.

For example, are fixed wing aircraft allowed to take off from an aircraft carrier while it is docked in port?

I would imagine (though could be wrong) land-based ATC and airspace conflicts have to be managed, amongst other issues.


texts: How can I work out Sea Level Pressure from QNH?

texts:
I am a little confused, is the QNH the current pressure at Sea Level? Therefore putting it into the altimeter will give your current altitude on the ground in pressure altitude relative to current sea level?
If not could someone please advise me on how to back calculate sea level pressure given the QNH and ground temperature.


texts: What coming changes might render current IFR equipment worthless in the foreseeable future?

texts:
I'm shopping for my first aircraft.  I have found a very well cared for 172 that is VFR.  I also found an IFR-certified 172 that is higher time and cosmetically is showing its age.  I inquired about the expense of updating the VFR plane to IFR and the seller mentioned that due to some upcoming changes in IFR requirements even a plane that is IFR rated today may require a substantial investment to keep it IFR.

I've done a lot of searching and can't find anything to substantiate that statement.  The closest thing I found was an article from the AOPA way back in 1997 where the FAA had proposed rule changes that would have made a lot of (then) IFR compliant GPS units non-compliant.

What, if any, regulatory changes are on the horizon that might render the IFR certified equipment I buy today worthless tomorrow in the context of IFR?


texts: What's the effect of air density and temperature in the range of aspirated reciprocating-engine airplanes?

texts: Reciprocating engines give more power with less revs when the aspirated air has a higher density. Wings also give the same lift at less airspeed when the air has a higher density. Drag is higher, too... And for any thermal engine, efficiency is higher the colder is the 'cold reservoir' (for an internal combustion engine, the outside air). What's the combined effect of these variables (density and temperature) in the airplane range if the engine is an aspirated ICE?


texts:
Could someone please explain the concept of the boundary layer momentum thickness and its difference to boundary layer thickness calculation? Some explanation about the application of the boundary layer momentum thickness is also much appreciated.

Thank you in advance.


texts: Degree of motion terminology for special aviation movements

texts:
I perfectly understand yaw, pitch and roll. I'm wondering what a few special terms are for other unusual movements, such as those executed by a helicopter, drone or even perhaps something like a Harrier jump jet.

If "climb" refers to a straight up vertical motion along the z-axis, what is the name for the opposite? One might think fall, but I believe (keep me honest) in aviation, a "fall" is akin to a crash-landing type scenario, where the vehicle is out of control. Another word might be descent, but to me, that implies a downward change in pitch so that the vehicle gradually starts to lower its altitude over time and distance; instead I just want the opposite of a helicopter "climb"
I understand yaw means a change in left/right direction of the vehicle, but what motions describe a 90 degree, perpendicular change in motion to the left or right? Meaning, vehicle doesn't yaw, pitch or roll, it just "slides" 90 degrees to the left or right?

Any ideas as to what the correct terms are here?


texts: How is combustion directed in one direction in a jet engine?

texts: The answer here explains how jet engines work. During the BOOM phase air expands, however, the expansion would be in both direction, say toward the turbine blades as well as towards the compressor blades. Why is it that the compressor blades are not affected by this, because the blow could actually cause the compressor blades to rotate in the reverse direction?


texts: Why are there no Mach 4+ fighter planes?

texts: Why are there no Mach 4+ fighter aircraft?  It seems that such aircraft would have massive advantages when it comes to being able to fire longer range missiles and evade return fire.


texts: How are aircraft wings protected against flutter - aerodynamic oscillations that can break bridges?

texts:
It's a well known fact bridges can break due to self-amplified oscillations creating excessive loads on their structure, by resonance (galop). It happens from time to time. The Tacoma-Narrows bridge catastrophic failure is popular, but there are modern and less known stories about wind/rain creating a problem which needed to be solved after the bridge opening.

US Tacoma-Narrows bridge collapse in 1940, source (video)

A wing and a bridge roadway have similarities, and they are both exposed to a transverse wind.

Several aircraft in flight with flutter, source (video)

How are wind/rain/resonance-created oscillations (flutter) managed in airplane design? How are these effects tested in flight?


texts: Why are on-board computers allowed to change controls without notifying the pilots?

texts:
Recently we've had the 737-MAX debacle, where it increasingly appears that the MAX on-board MCAS system repeatedly would issue nose-down events, leading to the Lion Air crash, and possibly another

  On the Lion Air flight, when the MCAS pushed the jet’s nose down, the captain pulled it back up, using thumb switches on the control column. Still operating under the false angle-of-attack reading, MCAS kicked in each time to swivel the horizontal tail and push the nose down again.

Apparently there is a notification light for MCAS that was an optional package but will now be required.

It reminds me of two other incidents that lead to crashes

Air France 447 A330 - A frozen pitot tube caused the computer to switch to Alternate Law 2, which meant that the computer would no longer prevent dangerous flight inputs. While not the same as the MCAS issue, it lead to confusion of the cockpit crew (who had been making maximum nose-up inputs while at TOGA power), and thus the plane crashed due to stall. It was noted that there was nothing direct to alert the pilots that the switch had occurred.
Scandanavian Air 751 MD81 - Ice accumulated on the wings. When the plane took off, the ice fell off, striking the engines. The pilots noted the engines were surging and reduced the throttle, but an auto-throttle system not disclosed to the pilots kept increasing power back to full, thus causing engine failure and a crash landing.

Has anyone ever stated why aircraft systems are allowed to make changes without notifying the pilots? Is it something that just hasn't been a large enough problem to address until now?


texts: Is lift greater at the wing root of an horizontal wing,just like it's greater on a tapered wing?


texts: Could an airplane dock with a set of wing extensions while airborne?

texts: I figure there are limitations to wingspan while on the ground but could we engineer wings that stay aloft or get towed to allow a plane to 'dock' with them in order to fly higher/longer/more efficiently?


texts: Why is Heraklion airport a 'captains only' airport?

texts: I was recently watching "EasyJet: Inside The Cockpit" and it said pilots need 4 shoulder stripes to land at Heraklion International Airport, “Nikos Kazantzakis” (IATA: HER, ICAO: LGIR), but it didn't explain why they need the extra experience. Could someone please explain?


texts: Are there any safety hazards when testing the F-16's fire control radar on the ground?

texts: What are the procedures for ground testing an aircraft's fire control radar - for the F-16 or any other aircraft - and are there safety hazards associated with exposures to humans?  Most importantly, for a pregnant woman?


texts: How is a propeller diameter for given application determined?

texts:
let's say I need 1000 N of thrust for a given aircraft and flight velocity. I have available a fixed pitch propeller with a given shape, and thus given performance to advance ratio curves. Let's say the propeller diameter is 2m.

Now, what would determine if this is the best diameter for the application on hand? What if the blade shapes were scaled up to 4m? Wouldn't this generally be better for efficiency as the RPM would decrease and the air acceleration required would be lower? Other than practical factors like clearances, stability, etc., what aerodynamic reasons are there to stop increasing the diameter at a certain value?


texts: What are the options for renting an aircraft in the Caribbean with an FAA certificate?

texts: I've been looking for places to rent planes in the Caribbean, and haven't been able to find anything that wasn't charter service. Does anyone know of any pilot resources or specific rental or flight schools in the Caribbean, specifically the southern Caribbean?


texts: Why are critical flight computers redundant?

texts:
At least in airliners, the truly critical computers are redundant. Typically three identical copies of the autopilot computers run in parallel and compare results; if one computer disagrees with the other two, its output is ignored. The system allows some processors to be faulty while maintaining the operation of the overall system.

But why? I've never heard of microprocessors suddenly failing. Sure, there could be manufacturing errors, but those would have been caught at the factory. Perhaps the program (and its proof) is wrong, but it would be wrong in the same way across the processors. Similarly, bad input would cause bad output across all three computers. What kind of errors does this redundancy protect against? Do microprocessors sometimes just do math wrong?

If a microprocessor is overheated or overloaded and spontaneously fails, I would expect it to stop doing anything and produce no output. To deal with this kind of failure, you'd want to have a backup processor, but you wouldn't need to compare the outputs of three computers—any output produced would be assumed correct, so you'd be happy to directly use the output of any processor that was producing output.

Related: The answer to What is the purpose of multiple autopilots? simply says "redundancy" before going into how this is achieved.


texts: Where is the airspace not covered by primary Radar?

texts:
Most ATC in the world rely primarily on secondary radar to know where planes are. This requires that the transponder on the plane works correctly.

This means that maintenance and deployment of primary radar is no longer a primary concern for airspace regulation. It becomes at best a secondary backup system before they need to pull out the flight progress strips and airways charts.

Where are the spots that is not covered by primary radar? I understand that some military ships have primary radar and can act as a mobile radar during operations.


texts:
Recently I started flying a model aircraft, admittedly a kindness for a motor stuck onto a piece of foam, and have noticed that it either bobs, for lack of a better term, like something afloat on water might when depressed or that it skips, for lack of a better term, like a stone thrown across the surface of a pond might.
In the first case the motorized foam is at cruise at constant speed at some height when I force it into a dive it seems to "bob" back up to it's original height when I stop giving it the input to dive. I suspect I'm observing a little Newtonian mechanics here trading potential energy for kinetic energy during the dive and that this gets converted back as it "bobs" up again.
In the second case when the motorized foam is at cruise at constant speed at some height it tends to undulate. This is exacerbated if I increase the angle of attack(?) such that in the extreme, where it stalls, the motorized foam goes into a cycloidal "swoop". Each "swoop" starts with a stall where it'll "flip over" and dive down and gaining speed as it does so, the gain in speed results in the nose "picking up" resulting in a "swoop" back into a near vertical "climb", at roughly the same height as when it first stalled it'll stall again and repeat the process.
Do larger scale aircraft, that is anything with at least a human on board, behave in this manner as well? In the case of "bobbing" do pilots use this in any way to their advantage e.g. does it help them maintain altitude or is it helpful in some way during dire situations? (My imagination can't help but wonder if there was ever a pilot who forgot to throttle down on decent, intending to land, who found they simply "bobbed" back up to their pre-decent altitude?)
In the case of "skipping" I can't imagine passengers being very agreeable to such a motion, especially not the stalling swoop variant, but I'm fairly certain I've felt a plane undulating slightly on a flight before. Do pilots have to constantly fight such undulations or do they reduces/eliminate this through proper trim?
Note:
I'm not talking about wing in ground effect, I observe this when the motorized foam is at roughly tree top height. The veldt I fly in comprises of knee high grass so I doubt I'll observe this until I fly over a lawn or something.
Note:
If it's relevant motorized foam is shaped like a flying wing; in case aircraft with tails behave differently.
Note:
I've certainly observed that the wing tends to "pitch up" in proportion to its speed above a certain speed; this is most noticeable in the cycloidal "swooping". Initially I thought this was a CG thing or that the motor was off center and generated a moment force but I see this is already discussed. It's more likely my trim is off.
Update

Update :
I phugoid it out, I believe, stuck a coin under the battery (rotating it made it poke out like an Adam’s apple) and I trimmed the trim to something slim. Did the glide test and she stays level as a lake wafting gracefully from the skies like Dumbo with his trunk out, tail tucked and his C.G. Is under his chin ! Thanks all for the helpful hints and the epoxy related non-confessions. (When the coin is worth more then the model I’ll fork out for an upgrade. Till then I’ll wait for the back of this cold front)


texts: Why did Concorde have a 8000 ft airport elevation limit?

texts:
According to the Concorde Flying Manual Volume II(a) - 1 Operating Limitations - page 01.01.02 the take-off and landing airfield altitude is minimum -1000 ft and maximum 8000 ft. Why is Concorde limited to a maximum airfield altitude of 8000 ft, excluding Concorde from airfields like El Alto International at 13,323 ft?

My initial thoughts were either maximum braking action limitations for rejected take-off or maximum tire speeds, but unfortunately the manuals linked above do not mention max tire speed or brake energy limits.
Update: As @gwally pointed out, Concorde did fly to Bogotá, Colombia with an airfield elevation of 8363 ft two times, in 1974 and 1975. So it seems the 8000 ft maximum airfield elevation seem to be a certification limit or operational limit, and not a performance limit of Concorde.


texts: Is moving payload masses during flight to restore mass centering, or to avoid having to trim, a useful approach?

texts:
Note: Title was previously "Movable big missiles/bombs/tanks under fighter jets: conceivable?"

Example: lateral weight distribution in fighters

Fighter-bombers jets are small and lightweight in proportion to the under wings load (including payload but also external tanks) they carry which means most stuff can't be placed right below the body of plane and heavy payload (very big missiles and bombs) ends up relatively very far from the center of mass.

(Although some designs have a bay to hide payload, the bay is small compared to the maximum possible load of other fighter and they still have the option to carry under the wings.)

So here is a (possibly unworkable) idea:

Is it conceivable to mount heavy load on movable arms that can move weight left or right to adjust mass centering:

at under wing load installing time?
during fight?

The heavy load, including external tanks, would be automatically moved to preserve mass balance.

Example: longitudinal balance for cargo planes

The idea here is to move the fret of a cargo plane in the longitudinal axis, to adjust balance and minimize trim.


texts: Does Clearance Delivery operate in the same way for airports in Bravo, Charlie and Delta airspace?

texts:
Something tells me that Clearance Delivery might offer different instructions at airports within Bravo, Charlie, and Delta airspace, e.g. if I take off VFR from KLAX vs from a class Delta out in the middle of nowhere.

Can someone give me some guidelines on what might be similar or different? I'm guessing that Clearance Delivery might give me a heading, altitude, and a departure frequency in a class Bravo. In class Delta, I might get an altitude (stay below 2500' AGL) to remain inside of the Delta?


texts: How can a passenger tell if a flame-out / engine failure has occurred?

texts:
Reading this page, a retired American Airlines pilot quotes:

  We tell passengers what they need to know. We don’t tell them things that are going to scare the pants off them. So you’ll never hear me say, ‘Ladies and gentlemen, we just had an engine failure,’ even if that’s true.

Given this, how can an observant passenger sitting over wing (seeing most likely very little of the engine), determine if a flameout or shutdown has occurred from observation?

This is applicable to an aircraft not unlike the Boeing 737 (which I fly on often).


texts: Would tubofan aircraft benefit from adjustable fan blades?

texts: Would turbofan aircraft benefit from adjustable fan blades as do turboprops? Propeller aircraft adjust their propeller size, i.e. shorter propeller for cruising at maximum design altitudes where the air is thinner for efficiency, and a longer propeller where the air denser for increased thrust used for increasing altitude at early stages of flight. Would turbofans benefit from this when flying at maximum altitude for efficiency? If not why not?


texts: Is there a formula to calculate ground distance traveled given rate of climb and true airspeed?

texts:
I'm looking for a formula to calculate the horizontal distance (guess it is the Ground Distance) passed during the phase of ascent (or descent), having the rate of climb in ft/min and the TAS in knots. I did not found a clear answer about this question. I think it may concern with the Climb Gradient.
Refering to the image below, I'm trying to calculate d, having:

h = 11200 ft
RoC = 1250 ft/min
TAS = 75 kn

ClimbGradient = (RoC / TAS) * 6000 / 6076,12 = (1250 / 75) * 0.9874 = 16.45%
d = h / (ClimbGradient * 100) = 11200 / 1645.78711 = 6.80525 nm

Is this correct calculation? I will update this question with the correct formula in other case.


texts: Are the communications between captain and flight attendants standardized?

texts:
Premises

For usual communications between pilots and ATC, a specific phraseology is followed.
In case of an an unexpected event (e.g. a sick passenger), flight attendants and pilots can communicate through intercom.
Pilots (particularly the captain) can speak to all people in the cabin (including flight attendants) through the public address system.

Questions

Do the communications made between the cockpit and the cabin (thanks to the public address system) follow a specific phraseology to deliver information to flight attendants?
Are there some messages following a specific phraseology that trigger a reaction among the flight attendants (e.g. preparation for flying across turbulence), but passenger may think the message is address to them?

I think of the coordination of the preparation of the cabin for the different flight phases (taxiing, taking off,...) or indication of the strength of turbulence (implicating the flight attendant may not begin to move carts along the cabin).


texts: How can engine positioning affect flutter tendency?

texts:
I understand that moving the engines towards the wingtips would increase flutter tendency, but are there any other positioning options which could affect flutter?

How about moving the engine position forward, or backward on the wing. What about the twist of the wings, & the set angle of attack on the ground. Do these have to be considered when positioning an engine on the wings of the airplane?

Also, what about rear mounted engines. What should be considered here to reduce flutter tendencies of the stabilizers?


texts: When a typical commercial airliner flies overhead, what is the actual noise we are hearing?

texts:
We're all familiar of the sound planes flying quite high overhead and you hear a faint drone, even when planes are lower to the ground you hear them scream at a slightly higher pitch, but what exactly are you hearing?

I would guess it's either the sound of the fan blades spinning extremely fast or the noise of the air (thrust) being forced out the rear of the engine?


texts: Is a light aircraft still usable after a successful airframe parachute deployment?

texts:
Some light aircraft now have airframe parachutes. If a pilot does have to pull the chute on a Cirrus (for example), is the aircraft flyable or at least repairable after landing or is it a write-off? What G forces are involved in the impact?

I realize that there are lots of possible variables here, but let's assume that the parachute deploys correctly and in plenty of time for a stabilized descent; touchdown is in 'ideal' conditions, i.e. on level, unobstructed ground; and impact forces are as described in the Cirrus CAPS guide:

  The airplane will assume its touchdown attitude to optimize occupant
  protection. The airplane will descend under the canopy at less than
  1700 fpm and ground impact is expected to be equivalent to dropping
  from a height of 13 feet (about 4 meters). The airframe, seats and
  landing gear are all designed to absorb the impact energy.


texts: How is a stalling speed not affected by airspeed?

texts:
A question from the aerodynamics section of the FIA written:

Which action will result in a stall?

Incorrect answer: Flying at too low an airspeed

Correct answer: Exceeding the critical angle of attack

I could be flying in straight and level flight and if I slow down below stall speed the airplane will stall. So how can it be said that flying at too low an airspeed will not result in a stall?


texts: What radio frequencies are used for intercom in formation flying?

texts:
What radio frequencies are used for air-to-air intercom in formation flying? I assume there is a difference between military and civil aviation (e.g a group of GA aircrafts flying as a formation).

I found a couple of civil UNICOM frequencies here (e.g. 122.8 MHz, 122.975 MHz, ...). 122.750 MHz (Aviation Air to Air Communications) seems to be what I am looking for (correct?). But what if there is more than one team?

I also wonder if in military or professional formations (aerobatic formations) something outside the Very High Frequency (VHF) Aviation Band is used (to provide better quality, e.g. digital communication).

In this article I can see lot of military frequencies, but not telling me what to use for military formation flying.


texts: What is the function of the holes in splitter plates?

texts:
Do the holes in splitter plates reduce the boundary layer, or do they serve a different function such as acoustic/vibration damping?

  Many splitter plates have a series of holes drilled into the surface closer to the engine side of the intake. Suction is applied to these holes, further reducing the boundary layer.

This bit is from Wikipedia, it's marked Citation Needed, and I'm unable to corroborate it.

Taking the Eurofighter example:

(Source)

If it is true, does it only work at supersonic speeds? The way I see the channel above the intake is that it is diffuser shaped. So a reduction in pressure above the intake would only work at supersonic speeds, is that correct?

A similar system can be [barely] seen on the F/A-18E.


texts: Is it safer to have an airplane inspected twice a year?

texts:
According to the Nall report and as voretaq7 explained here, around 11% of fatalities in general aviation are due to mechanical failure and maintenance issues.  Although these numbers are relatively small (about 25 per year) they are a danger that even a very cautious pilot would seem to have little control over.

So, if annual inspections were performed twice a year, does the data suggest  it would impact these numbers significantly?  Please include references to studies and their implications.


texts: What is the legal interpretation of rest for FAA Part 135 operations?

texts:
14 CFR 135, Subpart F contains the rest requirements for Part 135 operations.

The rest requirement for 1 and 2 pilot unscheduled crews (typical) comes from:

  135.267(d)
  Each assignment under paragraph (b) of this section must provide for at least 10 consecutive hours of rest during the 24-hour
  period that precedes the planned completion time of the assignment.

What does the FAA consider rest and what actions by the company will interrupt the required rest?


texts: What would the "wings level" button most likely do if activated in the event of a flat spin?

texts:
If an aircraft equipped with a wings level button (such as the TBM 930) entered a flat spin, would pressing it accomplish anything productive?

I am aware that the purpose of the button is to return the aircraft to straight and level flight if the pilot becomes uncomfortable with the vehicle's orientation. However, what I am unsure of is whether this system can control both the engine and control surfaces in a manner that would be potentially helpful in a seemingly unrecoverable situation.


texts: Why are there two IRS switches on the 737NG?

texts: I've noticed in some videos,that there are two IRS switches on the 737NG. Why is that so and what is the primary purpose of IRS? Also, what is the alignment of the IRS mean?


texts: What is the maximum theoretical lift of a plane as a function of engine power and surface of the wings?

texts:
Maximum theoretical lift of a plane as a function of engine power and surface of the wings?

I know that the maximum static thrust of a propeller turned by an engine of power $P$ can not be greater than:
$$Thrust_{max}=\sqrt[3]{2\pi(\frac{D}{2})^2 \rho P^2}$$
where $\rho$ is the density of the air and $D$ the diameter of the propeller.

I am looking for a formula that gives the maximum theoretical lift of a plane which flies horizontally. After half a page of demonstrations I have found a relation:

$$Lift_{max}=\sqrt[3]{2S \rho P^2}$$
but I am not sure if it is correct ($S$ is the total surface of the wings).

Update 1

Two examples that show the formula for max lift gives lifts smaller than the loaded weight of the plane. I do not know why.

1) Cessna 172: Gross weight - $1,111kg$, Powerplant - $160 hp$, Wing area - $16.2 m^2$

$Lift_{max}=(2 * 16.2 m^2 * 1.2 kg/m^3 * (160 hp)^2)^{1/3}=837 kgf<1,111kgf$

2) de Havilland DHC-6 100 Twin Otter: Gross weight - $5,246kg$, Powerplant - $2*579 eshp$, Wing area - $39 m^2$

$Lift_{max}=(2 * 39 m^2 * 1.2 kg/m^3 * (2 * 579 hp)^2)^{1/3} = 4,198 kgf<5,246kgf$

Update 2

I have tried a different demonstration that stars from the known relations:
$$Lift={0.5 \rho S C_L V^2}$$
$$Drag={0.5 \rho S C_D V^2}$$
$$Power=Drag * V$$
By eliminating the speed of the plane, $V$, the lift result as being:
$$Lift = \sqrt[3]{2S \rho P^2 \frac{C_L^3}{4 C_D^2}}$$
It appears that this new lift can be greater than $\sqrt[3]{2S \rho P^2}$ as long as $\frac{C_L^3}{4 C_D^2}$ does not seem to be restricted to always remain less than 1.

Update 3

Using the formulas for $C_D$ an $L_{max}$, suggested to me by Peter Kampf and mnunos, I have made some evaluations.

$$C_D = C_{D0} + \frac{C_L^2}{\pi\cdot AR\cdot\epsilon}$$

$$L_{max}=\frac{1}{2}\cdot \sqrt{3\pi AR\epsilon}\cdot \sqrt[3]{\frac{P^2\eta^2\rho S}{4 \sqrt{C_{D0}}}}$$

For the assumed values: $\eta=0.7$, $\epsilon=0.8$, $C_{D0}=0.03$, $\rho=1.2\: kg/m^3$ and the data taken from the Cessna 172 general characteristics: $P = 160\:hp$, $S=16.2\:m^2$ and $AR=7.32$, I get:
$$L_{max,\:\eta=0.7}=2199\:kgf$$
However, only $57.451\:hp$ are necessary for lifting $1111\:kg$ (horizontal flight), the rest up to $160\:hp$ can be used for climbing.

From the relation:

$$m_{plane}gV_{climb} = \eta(160\:hp - 57.451\:hp)$$

I get $V_{climb}= 4.913\:m/s$ which is significantly greater than the rate of climb 3.66 m/s the Cessna 172 has.

It seems that working with $C_{D0}$ and $\epsilon$ gives only a quite rough estimate of the max lift. Without knowing the actual $C_L=C_L(C_D)$ little can be said about the real maximum possible lift of a certain plane.

Update 4

The maximum theoretical thrust of an ideal helicopter propeller having the diameter identical to the wingspan, $11\:m$,  of a Cessna 172:

$$T_{max,Diameter\:prop=11\:m}=(2 * pi * (11 m / 2)^2 * 1.2 kg/m^3 * (160 hp)^2)^{1/3} = 1 509.95\:kgf$$

is considerably smaller than the max lift of the plane,  $L_{max,\:\eta=0.7}=2199\:kgf$, I calculated in Update 3. Is such a result logical?  Does it have an explanation?


texts: How to replace two propellers on the same aircraft reaching the time limit?

texts: When both propellers of the aircraft reach the time limit (60 month) and need to be replaced, can both propellers be replaced at the same time and perform only one flight test to reduce time on ground or should they be replaced one at a time just for safety or to investigate any discrepancy that may arise?


texts: Can someone describe the numbering system used by the military and how it has changed over the years?  I know that there are fighter aircraft such as the F-15, F-16, F-22, etc but why are there aircraft numbered like the F-117?  and why is the B-2 a B-2 when we have had B-17s in the past?


texts: What does a white diagonal line mean on an Airbus ECAM DU?

texts: When my A321 powers up, the lower ECAM DU shows only a diagonal white line. What does it mean and what would be the fix?


texts: Is "takeoff distance" measured over the ground, or to a point in the air?

texts:
I read that takeoff distance was the distance for which the airplane is on the runway, as well as the distance for which it ascends to 15 meters off of the ground.
Does it get measured as the hypotenuse of the "triangle" the airplane makes, or as the projection of its movement onto the runway, which is a purely horizontal distance?


texts: Is it currently feasible to glide airliners from cruise level to ILS glideslope (CDO)?

texts:
Is this possible for some airports to perform full continuous descent operations (CDO), gliding at idle thrust from top of descent to glideslope interception.

(source: Lubo Mitev's Blog)

LAX and UK airports seem to allow some CDO, maybe not from ToD.
What is the current status of such experimentations?
Is this something that could/should be extended to a lot of (or all) commercial planes?


texts: Would climbing onto fighters placed on display cause damage?

texts:
The question is about any more or less modern plane similar to Su-27 in its fuselage design. It's not uncommon to install retired planes as monuments. Here's one example in Eastern Europe (image from this post on some local Reddit equivalent):

The shot shows a retired Su-27 which had its engines and electronics removed and was installed on a pedestal somewhere in a city. It's not uncommon for locals to climb both such pedestals and the planes - youngsters do this for lulz and also to make photos of themselves. Standing and sitting on wings or behind the canopy are typical examples.

I guess this is not very good for the airplane fuselage. Not only will paint get damaged but also the fuselage may be mechanically damaged - mostly metal sheets might be bent.

I know that it's possible to accidentally fall from a plane, especially when it's wet because or rain or melting snow, but let's ignore that in this question. I'm only asking about what's good or bad for the plane.

How bad for such a plane is climbing it by an unprepared person (who doesn't know where exactly it's safe to step)?


texts: How thick is the skin of an aircraft like the Airbus A350 or Boeing B777?

texts:
We can evaluate how thick walls are by looking at door or window frames, however that isn't representative of an aircraft fuselage, which appears to be very thin:

Airbus A350 XWB forward fuselage, source

How thick (thin!) is the fuselage?
Do some areas have a thicker skin for some reason?
What about glass, doors, wings, floors, and other elements than the walls?

(I'm talking about the aircraft skin itself, not stringers or other structural stiffeners.)


texts: Is there a best number of wheels per bogie?

texts:
I understand the need of having more wheels when the aircraft is designed to be heavier. The number of wheels per bogie and the number of bogies differ from an aircraft to another. For example, there are some main landing gear compositions (from the lightest to the heaviest aircraft):

A320/B737: two 2-wheel bogies
A330/A340/B767: two 4-wheel bogies
DC10/MD10: two 4-wheel & one 2-wheel bogies
B777: two 6-wheel bogies
B747: four 4-wheel bogies
A380: two 4-wheel & two 6-wheel bogies

Given those examples, I guess the maximum number of wheels per bogie is 6 and thus given the number of wheel of the B747's main landing gear, it could have been composed of fewer bogies with more wheels on each (e.g. three bogies: two with 6 wheels and one with 4 wheels). So I wonder if there is an optimal number of wheels per bogie, and if for a given number of wheels it is better to add bogies with fewer wheels per bogie.


texts: What are the main differences piloting Boeing vs. Airbus aircraft?

texts:
What are the main differences in flying a Boeing vs an Airbus aircraft?

Ignoring cosmetics, e.g. nose/window shape (see How can I tell apart an Airbus from a Boeing?)


texts: Are direct law command gains monitored for correctness when flight control computer is in normal mode?

texts:
This question is specific to Bombardier C-Series aircraft which  has three modes: Flight control computer normal mode, FCC Direct mode and REU direct mode:
(I am not sure if other aircraft have an intermediate mode before switching to alternate law)

Control law gains are computed for both FCC normal and FCC direct mode even if the computer is in normal mode. Direct mode commands are outputted when the switch happens from normal to direct.

Fly By Wire Flight control computer switches from normal law to alternative law under certain conditions (when minimum required sensor set is lost for instance).
So I assume the control laws are also switched from normal to direct.
Are the direct mode control gains computed and monitored when the flight control system is under normal law?


texts: How safe is the Boeing 737-800 in high winds?

texts:
I'm not good with flying. However, on Wednesday morning I'm flying from Gatwick to Bergen, Norway, traveling alone with two young children.
I'm trying desperately to not show my kids how afraid I am of flying - with families in two countries we have to do this all the time. So I have to be mentally prepared for this: the forecast is showing high winds.
Around the time of take-off (10:50) it shows 16-18mps, SSW.

As far as I've been able to understand, this is at the limit of what a Boeing 737 can take?

Basically: Will we be safe? How can I know? Will it be bumpy? What will happen? Should we cancel?

Can you help me understand?


texts: What are the differences between porpoise; bounced; and nose-pointed-down landings?

texts: I have read some articles, and to tell the truth, I could not clearly see the differences. I would like to know if there are differences or not.


texts: Pilot Jobs, where to find one? How to land one?

texts:
I have just finished doing my commercial license in US and hold an FAA multi single IR and are converting to my Australian license, what are the job prospects like for a low time pilot in Australia i am not sure weather to go back to the US and train to get a CFI job over there. Just a little lost with my aviation career at the moment and in need of some guidance.
PS I am really not fussed who or where I fly, I just want to fly and get paid for it.


texts: Is there any particular reason for the cockpit of the 747 being on the upper deck?

texts: The cockpit of the 747 is on the upper deck, but the cockpit of the A380 is situated on the lower deck. Is there any reason (be it engineering or anything else) for the location of the cockpit?


texts: Why are vectors used for sequencing rather than speed control?

texts: Why would ATC generally issue vectors instead of simply issuing speed reductions to aircraft? It'd seem more efficient to have aircraft flying less track miles, so is there any reason that speed control is worse than giving vectors to aircraft?


texts:
The following question is from the FAA PAR (Private Pilot, Airplane) exam :

The load factor on an airplane increases with :
(A) Any moderate change in pitch attitude, increase in weight, and steep turns.
(B) Increase in weight, an increase in power, and any moderate pitch changes.
(C) Increase in weight, steep turns, and abrupt changes in airplane attitude.

The correct answer is supposed to be (C).
All of the answers say that load factor increases with an increase in weight. However, load factor is inversely proportional to weight by definition.
What am I misunderstanding?
Edit: I think it is supposed to say "load" instead of "load factor" but it was not written that way.


texts: Who was the first black person (in the world) to go airborne in an aircraft?

texts:
Who was the first black person in the world to go airborne in an aircraft?

Surprisingly, google fails me in this so I don't think it falls under the closeable category of trivial trivia.

(I do not use the term "African American" because the answer might not be an American. I don't use "African" either because there are white Arab Africans. I suppose Sub-saharan African? But then there are black Africans on the north coast of Africa too. So I don't know what the term is that's both accurate and politically correct.)

Closest I've found so far:

Bessie Coleman was the first black woman to hold a civil pilot license, but I could not find a date for her very first airborne event, either as a passenger or pilot.
Eugene Bullard was one of the first black pilots, as was Ahmet Ali Çelikten and Emory C. Malick according to wikipedia. I could not find dates for their very first airborne events either.

My question is about any such person to be airborne in an aircraft. Obviously this could be a passenger, not a pilot. Edit: and it could be an employee too. I don't know how the personnel was organized back then, but maybe some cargo handler went along with some flights.

BTW the definition I'm using for "aircraft" is any heavier-than-air thing flies via lift. So no hot-air balloons and no dirigibles. But rotary-aircraft and gliders are okay. I think they had experimental ones very early in aviation history.


texts: Do FDRs & CVRs (black boxes) have an in-service life span?

texts:
Do Flight Data Recorders (FDRs) and Cockpit Voice Recorders (CVRs), aka black boxes, have an in-service life span? Is it necessary to replace them over time?

If so, are there any regulations governing their maximum life?

Note: The suggested duplicate asks specificly about post-crash lift time. This question is about in-service lifetime.

After a crash, does the information stored on flight recorders have expiration dates?


texts: What is the tailhook on naval aircraft made out of?

texts:
What is the tailhook that enable naval aircraft to land on aircraft carriers, it must be made out of a strong metal to not bend or 'snap' under the force of the thrust that the plane is expelling, as they land then put thrust to full.

Image Source—PACIFIC OCEAN (Dec. 22, 2011) Landing signal officers supervise the arrested recovery of an F/A-18C Hornet on the flight deck aboard the Nimitz-class aircraft carrier USS Carl Vinson (CVN 70).


texts: What are the specific number of passengers and conditions required to select HI, NORM, or LOW on the pack flow knob?

texts: On the Airbus A320 there is a pack flow knob and you can either select HI(120%), NORM (100%), or LO (80%). You choose which one according to the number of passengers and ambient conditions. Obviously If you have a full flight and it is hot outside you would choose HI. Or if you have very little passengers and it is cold or even raining outside you would select LO. But is there a specific number of passengers when you would select HI or LO, or is there a specific temperature, or both?


texts: How to balance the cargo on a plane with the wings further aft?

texts: For example on an MD-88, is the center of gravity on the back of the plane because the empennage, wings and engines are located there? So they would have to put most of the cargo on the back of the plane?


texts: Can new technology help planes dodge turbulence?

texts:
With so many technological advancements happening in the aviation industry, will it be possible for airlines to smoothen the effects of turbulence, as turbulence cannot be eliminated?

The following news indicate the same:

Smooth talk: How Qantas is ironing out the bumps

Feathers in flight inspire anti-turbulence technology


texts: What are the spiky things on the back of the Antonov-225 vertical stabilizers?

texts:
On the Antonov-225's split vertical stabilizers, there is a 'spiked' structure pointing directly rearwards (as you can see below). What is the purpose of these two structures?

source


texts: Did the DC-9 ever use RATO in revenue service?

texts:
While reading the NTSB report on the crash of ALM Flight 980, I came across this interesting tidbit:

  ...  The fuel charts used for the study made allowance for a higher consumption rate than the standard DC-9-30 series aircraft.  This was the result of a fuel audit by the Douglas Aircraft Company on ONA aircraft and was due to jet assisted takeoff fairings installed on those aircraft.  [Pages 7-8 of the paper report; pages 12-13 of the PDF file of the report.  ONA = Overseas National Airways, who operated the flight on behalf of ALM.  Emphasis added.]

Did these DC-9s ever actually use RATO during revenue operations?

EDIT: "Revenue operations" here means "any flight conducted for monetary compensation".


texts: Which agency issues private pilot certificates?

texts: With which agency would you apply if you wanted a private pilot certificate? Is it FAA (Federal Aviation Administration), NTSB (National Transportation Safety Board), or ICAO (International Civil Aviation Organization)?


texts: What does the "visibility" number mean on an approach plate?

texts: In the profile view in an approach plate, there is a visibility number next to the MDA or DA. What does it mean? Is it limitation to use the approach?


texts: How is a flight routed from the last waypoint of a STAR to final?

texts: If you look at a flight plan on FlightAware, the last code will be a STAR. Take a flight into JFK, for example, that uses LENDY6: the last waypoint of LENDY6 is the LGA VOR/DME at FL190. If the plane then lands on 04R, how does it get routed to final? Are there any documents that show this routing?


texts: How many flights can be made under EASA permit to fly?

texts: I understand the permit to fly is valid for 14 days, but how many flights can be made in that time?


texts: Is it possible to divert a plane to a distant airport?

texts:
Some years ago I have spotted that an Eurolot flight from Amsterdam to Gdansk, diverted close to final approach to a distant airport on the other side of Poland:

Is this another example of Flightradar24 bug and it is more than possible, that this particular flight actually landed in desired destination airport? Or are there any business or operational rules or some special situation, that would judge diverting a plane to a distant airport, while having at least 5-6 other airports closer "on the track"?

For me -- layman -- the answer is: No, there are no such reasons and airplane is always diverted to the nearest airport, that is able to accept it (taking plane type, weather conditions etc. into account). But, I'd like to get some expert confirmation, if there are no exceptions from this rule of thumb?

EDIT: In my opinion, we're dealing with a quite different situation here than in previous question (and that's why I didn't merged both questions into one). Mainly, because:

flight path IMHO is clearly suggesting a diversion, not an error in Flightradar24 and
plane's vertical speed is suggesting, that plane is actually landing in the moment, this screenshot was captured, and since I was living in Katowice for over 30 years now, I'm pretty sure, that there was not direct flight on AMS->KTW route, neither by Eurlot nor by any other airline and neither at the moment of capturing this screenshot nor right now.

So there actually was no other flight between Amsterdam and Katowice that Flightradar24 could mistakenly taken as this one.


texts:
This video says (at 25:06) that you should do it as soon as possible.
but I just learned in class that you should wait for an ice build up then turn it on vs just turning it on. This would prevent an ice bridge to form:

But in the clip it says modern de-ice boots don't have the problem mentioned in the picture.


texts:
According to Wikipedia, only single-engine aircraft with an MTOW no greater than 12500 pounds are required to demonstrate the ability to recover from a spin, and not large or multi-engine aircraft.  This seems backwards to me, as it would seem to be far more critical for an airliner with potentially hundreds of people on board to be able to successfully escape from a spin than it would be for a small GA aircraft where only the pilot's life is at stake, and not anyone else's.

Can someone explain this seeming contradiction?


texts: How is the quadrantal rule applied to VFR flights in Hungary?

texts:
I'm looking for a clear explanation for this quadrantal rule question (it applies to Hungary):

  A VFR pilot is cruising, en-route in level flight, above the transition level of FL035. His magnetic heading is 355°, and he sees that by having allowed for 8° of starboard drift he is exactly on track. What would be an appropriate Flight Level for the pilot to choose in accordance with the Quadrantal Rule?


texts:
I've seen the position of Second Officer being advertised for some short-haul airlines, but I don't entirely understand what roles and responsibilities they have on the flight deck.

I know a second officer exists on long-haul flight, which allows for crew to take rest breaks through the duration of the flight. So what do they do on short-haul flights? Are they still under line training?


texts: Why did a circular paper aeroplane of larger diameter fly further than one of a smaller diameter?

texts:
http://www.10paperairplanes.com/how-to-make-paper-airplanes/07-the-ring.html
I am not an expert at this- just a high school student, so please explain this in fairly simple terms. Thank-you very much in advance!


texts: What aircraft has this pattern of white strobe lights?

texts:
Just two nights ago, my brother and I noticed a weird flashing light in the night sky out in the countryside.
We regularly observe by naked eye aircraft flying by,  as well as satellites,  and this was not like anything we'd seen before.

It was only white light (no red, no green) , with the following sequence:

 *            _______          _______

Flash   <-1sec->  strong light  <-1sec->   dim light

The lines above the second and third lights attempt to show the fact that they faded gradually, while the first flash was like a camera flash, sudden and strong.

Every 3 seconds the cycle repeated.
The source of the lights seemed to be the same, i.e the same strobe light. Besides, the aircraft was pretty far away or small: with binoculars, it wasn't possible to discern any other strobe lights or a structure of any kind.

We first noticed the light above Ursa Major, it moved towards Cassiopeia and gradually faded away either because it moved away from us or because of the strong moonlight of that night.


texts: Airbags in aircraft - is that just a military thing?

texts:
The Bell OH-58D (a military helicopter used by the USA) has an airbag to make life better in the event of a crash.

I had never heard of such a thing in an aircraft before and I wondered if this unique to the Bell OH-58 and, if not, whether civilian light aircraft come with such an option ?


texts: Can I get a medical after having had a seizure eight years ago?

texts:
In 2010 I had a seizure (as of this writing that would be 8 years ago.)

I was a CFI/Commercial Multi pilot, and the FAA took away my medical. I have never piloted since, though I've missed it tremendously.

At the time I was told that I could not obtain a medical again unless it was after 6 years being seizure free with 2 off medication. I have been off medication for 1 year and have had no problems.

I recently got a battery of tests (EKG, MRI, CAT Scan/CT Scan) etc and found no seizure activity.

Have the rules changed in nearly a decade for this? Should I see an AME or would it be a waste of time? I know there is a pilot shortage now, so I'm wondering if it has gotten more lenient.


texts: What should a pilot do when flying in the vicinity of parachute jumpers?

texts: There are several airfields nearby where parachuting activities routinely take place. How far away is considered to be a safe distance from the airfield when flying past it en-route to another destination? Are there any particular frequencies to monitor besides the airfield frequency? How would I know parachuting is happening besides any NOTAMs?


texts:
What trimotor is this model?

(own work)


texts: Were there any instances of aerial combat between helicopters?

texts: Were there any cases in history where two attack-helicopters like AH-64 and MI-24(for example) were involved in an air fight between each other?


texts: Emirates has this feature on many of its A380s. From what I've read, the feature decreases the amount of runway an aircraft uses after landing. It also helps the aircraft achieve a certain exit way. Is this feature unique with only Aibus aircraft? How is it set up on an aircraft and how does BTV work?


texts: What is the largest aircraft (by max takeoff weight) in which all engines are in the tail?

texts:
The largest one I'm aware of is the Il-62, with a whopping 4 turbofans at its tail. Max takeoff weight is 165 tons.

I actually don't care how many engines there are, as long as all are at the tail. I don't care what kind either, turbofans, turbojets, anything. Don't care if it's military or civilian.

Edit: Airbreathing engines only. The space shuttle and buran don't go above 109 tons anyway, but the criteria here is max takeoff weight and those rockets "take off" far too differently than airplanes.

I googled this of course, but predictably these kinds of "what's the biggest" questions with specific conditions attached are not well-known. I'm hoping someone will know of an example bigger than 165 tons.

The reason I ask is because I'm curious just how much engine weight can be put at the tail and still have a conventionally-shaped aircraft. I'm a little surprised at the Il-62, actually. Sooner or later, to keep the center of mass ahead of the center of drag, the wings have to move more and more back until suddenly you have a canard config where the wings almost operate like a delta where the ailerons are also elevons and maybe even flaps.


texts: What is this flying boat being restored at the Udvar Hazy Center?

texts:
I am fortunate to live ~20 minutes from the Smithsonian Steven F. Udvar-Hazy Center.  At the back of the Museum is there restoration hangar, surrounded on two sides by a second level glass enclosed observation walk which allows guests to look in on what is being restored.  Because these aircraft aren't actually on display, I was not able to figure out what type of plane this is:

I was originally thrown off by the wings in the background, clearly embossed with the German Iron Cross, but I don't think the flying boat in the foreground is German.  Can anyone identify the plane in the foreground?

Here's a link to the original photo, in case you want to get a closer look.


texts: Does an aircraft's nose landing gear extend on take off?

texts:
Something I noticed while flying - while on takeoff it feels as if the plane is tilting upwards even though the plane is clearly still on the ground with all sets of landing gear.

Does the nose gear extend immediately upon acceleration to perhaps generate more lift? Or maybe it's just an illusion caused by the acceleration. (I've only noticed this on large aircraft - like for example: Airbus A320 or Boeing 737.)


texts: Why do almost all overwing exit slides open over the trailing edge of the wings, and almost none over the leading edge?

texts:
Almost all narrowbody jetliners, and many widebodies as well, use overwing exits to augment their evacuation capabilities; to escape the aircraft, a passenger or crewmember in the exit row pops the hatch next to their seat, and then everyone else1 chases them out onto the wing.
At this point, depending on the aircraft, they may simply slide down the flaps to safety, or a slide might inflate if the wings are too high above the ground.  Either way, though, they’ll be going over the trailing edge of the wings if it’s a land evacuation;2 even if the aircraft has multiple overwing exits per side (common among the larger jetliners), or if there’s a tail-mounted engine waiting to gobble up trailing-edge evacuees (like with the Fokker 70), everyone going out on the wings still evacuates off the trailing edge.
I know of only a few airliners with overwing exits that specifically direct evacuees over the leading edge of the wings, and two of these are very special cases:

The Concorde’s wings extend for most of the length of its fuselage, so it would be essentially impossible to fit enough exits in without having some going over the leading edge.
The Il-62 has a set of engines so close behind the wings that even the emergency-exit designers realised it would be a bad idea to send evacuees over the trailing edge (also, its overwing exits don’t have slides - instead, you have to slide down a rope over the leading edge of the wing).
The DC-10/MD-11 family has overwing evacuation slides that go over the leading edge of the wing, as do some A310s, making these, so far as I am aware, the only subsonic airliners without engines right behind the wings to use leading-edge overwing exits.

For low-slung narrowbodies, where you slide down the flaps to get to the ground, the predominance of trailing-edge overwing exits is excusable, as the flaps are on the trailing edge of the wing; however, even for large narrowbodies and widebodies with inflatable overwing evacuation slides, the slides still overwhelmingly open rearwards, over the trailing edge.
Why are overwing exit slides leading off the trailing edge of the wings so much more common than ones that go out over the leading edge?

1: I exaggerate slightly; some of the passengers will likely lock themselves in the lavatories or run up and down the aisle(s) screaming like chickens with their heads cut off, and one or two might even use the exit doors at the front and/or rear of the plane.
2: Ditchings work somewhat differently, and some aircraft do call for occupants to fall off the leading, rather than trailing, edge in this case.


texts: Why do larger aircraft need two or more static ports?

texts:
Some background information:
"Static pressure is the measurement of the ambient barometric pressure at the aircraft’s CURRENT location AND CURRENT Altitude.
The Static Port is located in a position on the aircraft that will not be affected by air flow as the aircraft moves through the air. This is typically on the side of the fuselage but can also be on the back side of the Pitot Tube or any other number of locations, it varies by the aircraft. Again smaller aircraft will typically have one Static Port, larger aircraft with redundant systems will have two."

After reading through that paragraph, I am wondering as to why smaller aircraft typically have one static port, whilst larger aircraft have two or potentially more static ports.


texts: What is the biggest airplane that does not need a paved runway?

texts: Since we don't need a control tower for instrument landings I was wondering what else that is thought to be needed could be skipped. I know some small general aviation is done on grass runways and I was wondering what is the biggest airplane that does not need a paved runway? Examples of manufacturer-approved usage or regular (e.g. daily or weekly) usage are preferred.


texts: What is this tube in a jet engine's air intake?

texts: I have long been wondering what is the official name of this little air intake tube located in front of the fan blades and its intended functions. I did search it on google but it was in vain. I guess that it may be a pitot tube installed inside a jet engine for gauging the airspeed of the engine intake air.


texts: Circled in red above, I suspect that's a high-lift device meant to improve handling at takeoffs and landings, but I don't know for sure really. What is its name and uses?


texts: What is the best reliable weight/power ration achieved by a pre-1911 plane?

texts:
From the article "DAYTON BOYS EMULATE GREAT SANTOS-DUMONT" that appeared on December 18, 1903, it can be calculated that the apparatus, which took off one day before, flew 700 lb / 16 hp = 19.84 kg / hp.
Are there planes, built by others, before say 1911, that came close to this performance?
1903-12-18, “Dayton Boys Emulate Great Santos-Dumont”, The Dayton Daily News, Ohio, US, December 18, 1903, p. 8.

DAYTON BOYS EMULATE GREAT SANTOS-DUMONT
TESTS HELD IN SECRET ON THE CAROLINA COAST.
Kitty Hawk, N. C., Dec. 17. We have made four successful flights this
morning, all against a 21-mile wind. We started from the level, with
engine power alone. Our average speed through the air was 31 miles.
Our longest time in the air was 57 seconds.  ORVILLE WRIGHT.
The above telegram was received by Bishop Milton Wright of this city last
evening from his sons Wilbur and Orville Wright, who have been for
several months at Kitty Hawk on the coast of North Carolina
experimenting with a flying machine, announcing the complete success
of their invention which they call the “Wright Flyer.”  Thursday
morning they made four successful flights against a wind of 21 miles
an hour, starting from a level and going at the rate of ten miles per
hour, which would be equal to a rate of 31 miles per hour in a calm.
No power was used in starting the flight except two aerial propellers
driven by a powerful but light gasoline engine. The landings were all
made easily and without injury to either the machine or operator. The
Wright brothers have been carrying on experiments for the past six or
seven years, and have built three previous machines for gliding by
means of which they attained proficiency in the control of their
apparatus. This year is the first time they have attempted to drive
their machine by power.
THE WRIGHT FLYER. The “Wright Flyer” is a true flying machine. It has no gas bag or balloon attachments of any kind, but is supported by
a pair of aero-curves or wings, having an area or 510 square feet. It
measures a little more than 40 feet from tip to tip and the extreme
fore and aft dimension is about 20 feet. The weight, including the
body of the aviator, is slightly over 700 pounds. The machine is
driven by a pair of aerial screw propellers placed just behind the
main wings. The power is supplied by a gasoline motor designed and
built by the Messrs. Wright in their own shop. It is of the four-cycle
type and has four cylinders. The pistons are four inches in diameter,
and have a four-inch stroke. At the speed of 1200 revolutions a minute
the engine develops 16 brake horse power, with a consumption of
little less than 10 pounds of gasoline per hour. The weight, including
carburetter and fly-wheel, is 152 pounds. The wings, though apparently
very light, have been tested to more than six times the regular load,
and it is claimed for the entire structure that it is a practical
machine, capable of withstanding the shock of repeated landings, not a
mere toy which must be entirely rebuilt after each flight.
The dispatch from Norfolk, Va., published in the morning dailies
contains much that is inaccurate and was based on imperfect or
unauthentic information. The credit for the success of the “Wright
Flyer” is jointly due to both Wilbur and Orville as the invention has
been the result of their joint labours.


texts: What categories/classes is a Ground Instructor able to instruct on?

texts:
Under §61.215 Ground instructor privileges, it says

  (a) A person who holds a basic ground instructor rating is authorized
  to provide—

  (1) Ground training in the aeronautical knowledge areas required for
  the issuance of a sport pilot certificate, recreational pilot
  certificate, private pilot certificate, or associated ratings under
  this part;

  (2) Ground training required for a sport pilot, recreational pilot,
  and private pilot flight review; and

  (3) A recommendation for a knowledge test required for the issuance of
  a sport pilot certificate, recreational pilot certificate, or private
  pilot certificate under this part.

But it doesn't say anything about what kind of category and class the ground instructor may instruct on. Is a separate GI rating required for each category and class? or is there one GI rating that covers all categories and classes?


texts: What are the popular algorithms or softwares used in identifying or track flights by ATC?

texts: Just curious to know about the algorithms /software used by ATC for tracking flights in real time.Can it be classified under ERP ?If no under which category does that fall ?


texts: Why don't passenger aircraft use the trijet configuration anymore?

texts:
As a kid I distinctly remember seeing aircraft like the bright blue KLM MD-11 having the prominent third engine on the tail.

https://commons.wikimedia.org/wiki/File:KLM_MD_11_AMS.jpg

However, I don't think I've seen a plane in the past few years (besides maybe a few smaller private jets) that has a engine on the tail - let alone a trijet configuration.

What's with their disappearance?


texts: Is making faster military fighters even practical?

texts: I was curious after reading a book on Cold War plane development about the Soviet ideology of making increasingly powerful jets that could break Mach 3 and so on. With the advent of BVRAAM's such as the Meteor and lasers that are already being scaled down, what are the advantages to increasing the top speed or cruise speed of a fighter jet?


texts: How much distance do I need between quadcopter propellers to avoid issues?

texts:
For a given propeller size (say 5"), what is the minimum clearance needed between propellers to ensure that not only do they not hit each other (easy to calculate), they also don't interfere too much with each other (i.e. tip vortices, airflow, etc.)

For example consider the following design: an X-shaped quad-copter where the propellers are at the end of each tip of the X - and the X across the diagonal (max distance from the center of the propellers) is 180mm - then 5" propellers will only have .279mm of clearance between them - now assuming that mechanically there are no vibrations/imperfections/etc. that cause them to run into each other, what else is there to avoid in terms of airflow? if they were raised such that two diagonal propellers are lower/higher than the others, would there be any issues? does it depend on the propeller pitch, or if it's a 2-blade or 3-blade propeller?

P.S. - I am unsure of the tags, please adjust as necessary


texts: What is this cylinder covered in threaded studs and what is it for?

texts:
I can't figure out what this is.  It looks like each post is threaded, but why is a mystery to me.  My guesses include a grounding post, a bolt/nut testing stand that's not actually in an aircraft, or a super metal black box .
What is it and what does it do?