Questions tagged [aircraft-performance]

Aircraft performance covers areas such as the amount of runway required to takeoff or land and how fast an airplane can climb or descend.

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Is a winglet better than an equal span extension?

Is there indisputable evidence that a winglet improves performance over an equal span extension? Please note: I am only interested in L/D improvements. Winglets do improve roll performance, that is ...
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53 votes
2 answers
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Can the Airbus A380 safely fly with two engines out on the same wing?

I know twin-engine jets can safely take off and fly with one engine out (i.e. all thrust only on one side). Of course quad-engine jets are also able to fly safely in case one engine is out. But is ...
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42 votes
6 answers
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Do airplanes need brakes in the air?

A few days ago I flew on a Boeing 737-900ER. Luckily I was sitting just beside the left wing, seat 26B. I observed that the spoilers were activated (opened) just after the pilot spoke on the Passenger ...
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41 votes
5 answers
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Is it possible for an SU-25 to fly high enough to shoot down a Boeing 777?

A common theory from pro-Russian netizens surrounding the MH-17 tragedy is that it was a Ukrainian SU-25 ground attack fighter plane which shot down the civilian airliner. However, MH-17 was flying at ...
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41 votes
8 answers
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Why would a glider have water ballast? If it is trying to stay aloft without an engine, wouldn't it be better to be as light as possible?

So I was looking at the description of a ASW 27 B glider and ran across this statement: Two water tanks in the wing plus a further 35 liter tank in the fuselage enable the ASW 27 B to carry more ...
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41 votes
9 answers
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Why was the boat mounted this way on the underside of the wing on the "Landseaire" flying yacht?

After seeing the below image of the "Landseaire" flying yacht here I was curious to know why the small boat mounted to the underside of the plane was mounted the way it was. At least to me (and @Dave ...
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36 votes
8 answers
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What happens if you exceed the maximum speed on a C172?

The airspeed indicator has a red marking that means: "never exceed this speed" ($V_{NE}$, around 160 KIAS). Why can't you exceed that speed?
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36 votes
4 answers
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What do winglets do to increase aircraft performance?

It seems like a lot of the newer airliners have winglets or wing fences. How do they improve aircraft performance?
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36 votes
1 answer
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Do the Mt. Everest rescue helicopters have modified engines to operate at high altitudes?

There are so many climbers on Mt. Everest today that there is now a helicopter rescue service there. They operate rescue up to 21,000 + ft. Because this is essentially stationary service it seems that ...
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35 votes
3 answers
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What are the effects of the Boeing 787's very flexible wings?

I recently came across this picture of the Boeing 787 series aircraft's incredible wingflex: I suppose this is a consequence of using very light CFRP wings, but how does the wingflex itself improve ...
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34 votes
7 answers
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Why are jet aircraft never designed with a slower cruise speed?

All jet airliners have a cruise speed between Mach 0.82 and Mach 0.85. At those speeds the aircraft are flying at their maximum subsonic speed. Any greater cruise speed would only be ...
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33 votes
1 answer
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What is the operating altitude of jetliners?

I am performing a science project, and this involves knowing the average operating altitude at which commercial passenger airplanes (jetliners) fly. I am trying to find minimum operating altitudes and ...
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33 votes
4 answers
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How does the mounting location of a jet engine affect aircraft performance?

Different jet airplanes mount the engines in different ways. For example: Under the wing To the fuselage How does the engine location affect aircraft performance? Is one better than the other?
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32 votes
9 answers
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Why are dirt and bugs on an aircraft so bad?

It's noted in many POHs to keep your aircraft clean all the time, but is there a reason to this? Dirt hardly add any sort of weight to the aircraft, bugs are extremely small and other things such as ...
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31 votes
4 answers
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How does wind affect the airspeed that I should fly for maximum range in an airplane?

I have heard that wind affects the actual airspeed that I should fly for maximum range in an aircraft. I understand that wind will not affect the airspeed that I should fly if I am looking for ...
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30 votes
9 answers
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Can a large passenger aircraft recover from a stall?

In fighter aircraft, we know that they have good enough of maneuverability. But in case of a passenger airplane, if a stall happens is the aircraft maneuverable enough to recover from it?
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29 votes
2 answers
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In WW2 aircraft, where were gun cameras mounted, and did they suffer performance penalties?

During WW2, some aircraft had gun cameras that activated whenever the guns fired, so that people on the ground could evaluate performance and help with kill ratios and other statistics. These were ...
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28 votes
2 answers
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Why does camouflage make some planes fly slower?

Why does camouflage decrease some airplanes' speed? I have noticed that some planes fly slower with camouflage than without it. For example, when the RAF applied camo on the P-51 Mustang, they noticed ...
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27 votes
3 answers
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Why don't we see business jets with wingtip fuel tanks anymore?

There is something I miss from the Learjet 35 (one from FS95/98) that I don't see any more: Fuel tanks on the wingtips! What happened to the wingtip integrated fuel tanks in the business jet industry?
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27 votes
4 answers
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What is the maximum safe bank angle of a 747?

This question arose during the comments of another question, linked for the curious: What does it take to turn a 747 around 180 degrees? Because the discussion was interesting, (and to avoid ...
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Did the F-8 have a stall speed of 1.6x its landing speed?

Wikipedia says that the F-8 was to have a landing speed of no more than 100 mph (160 km/h) This web page says that the F-8 did have Stalling speed 157 mph. The two don't explicitly discuss ...
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26 votes
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Why are planes slower at higher altitudes?

On many flight simulators, I have noticed that planes tends to get slower with increasing altitude. For example, I can reach 1100 knots just above the sea level in Google Earth flight simulator(F16), ...
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25 votes
4 answers
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Does temperature affect takeoff performance?

A few days ago, a Copa flight from Porto Alegre to Panama was delayed from noon until 12:30 AM. The company explained that the high temperature (about 40 degrees Celsius) would require a longer runway ...
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25 votes
2 answers
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How do insects decrease aircraft performance?

Is it true that insects hitting the fuselage could decrease aircraft performance and increase fuel consumption? Insects are small in mass. I think even a large amount of them accumulate on the ...
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24 votes
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How does gas turbine efficiency compare with supercharged piston engines?

If an aircraft mounted the exact same propeller on a supercharged piston engine and a turbine, and flew under identical conditions at the same pitch and rpm, how much more fuel would the turbine use (...
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24 votes
5 answers
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How do modern helicopters tackle Vortex Ring State?

According to the wikipedia page : Air vortices can form around the main rotor of a helicopter, causing a dangerous condition known as vortex ring state (VRS) or "settling with power". In this ...
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24 votes
1 answer
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What is a whip stall?

I was reading 14 CFR 23.3, which discusses airplane categories. In normal and commuter categories, stalls (except whip stalls) are allowed. The regulation, however does not define "whip stalls." What ...
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Why would an airplane pilot choose to intentionally use more runway than required for a takeoff?

An assumed temperature takeoff intentionally requires a pilot to use more runway than would be normally required. Why would someone want to do that instead of getting off the runway in the minimum ...
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23 votes
2 answers
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Why is the ratio maximum range speed/maximum endurance speed the same for any airplane?

It seems counter-intuitive that the ratio of speeds for maximum range and maximum endurance is always the same, $3^{0.25} = 1.316...$ for any heavier-than-air aircraft, regardless of its mass, size or ...
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23 votes
3 answers
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How do aircraft land on snow?

It is very common today for planes to land on snow (for example, in Antarctica). How are planes kept in control with so little friction against the ground? What is the procedure to perform this kind ...
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22 votes
6 answers
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What is the minimum stopping distance for a 747-400?

Im looking at purchasing disused 747-400: The aircraft will be stripped of all seats and other non essential items. The aircraft will be then flown to my property in Victoria, Australia and perform ...
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22 votes
7 answers
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Why do most single propellers have a clockwise rotation?

Why do most single propellers have a clockwise rotation (seen from the pilot's point of view)? There are though multi-engine planes that have each propeller rotating different directions, but in the ...
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21 votes
7 answers
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How does a fighter jet perform good and quick maneuvers with such small wings?

Fighter jets like the F-16, F-15, etc. have wings smaller than the length of the fuselage and can perform great maneuvers very quickly while an airliner with a long wingspan takes a lot of time to ...
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21 votes
4 answers
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What is the minimum turning radius of an SR-71?

What is the minimum turning radius of an SR-71 at Mach 3.2 and an altitude of 80,000 feet? I have heard that if an SR-71 were to cross the Pacific coast over San Francisco and pull a hard turn to ...
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21 votes
3 answers
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Who decides how fast commercial aircraft fly: the pilots or ATC?

Once a commercial aircraft is in the cruise phase, who determines the speed of the aircraft? Do pilots have the authority to fly at up to the maximum permissible speed of that plane, or does ATC ...
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20 votes
10 answers
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Why 1st and 2nd class but not fast or slow airplanes?

Why do airlines separate passengers into 1st and 2nd class but do not offer fast or slow connections? Isn't the biggest cost the kerosene? And isn't the cost directly proportional to speed?
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20 votes
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What aircraft could make non-stop transatlantic flights in 1958?

According to Wikipedia: TWA flew to Europe nonstop from O'Hare starting in 1958 The Great Circle Route distance from ORD/KORD to LHR/EGLL is 3953 miles. Other major European airports would have ...
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20 votes
2 answers
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How is supercruise achieved?

Wikipedia article tells that supercruise is a condition when an aircraft can achieve velocities above Mach one without using the highly inefficient afterburners. But still, there are not a lot of ...
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20 votes
1 answer
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How can an Airbus Beluga fly only with two engines and use short runways?

She could land and take off fully loaded on 2000 meters of runway at Hawarden Airport as seen here in this video. At my local airport the runway is 2500 meters long and an Airbus A300 is not allowed ...
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19 votes
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Is it possible to stall a plane so badly that the nose refuses to go down due to lack of airspeed?

So basically, a stall from a high AoA to the point that the entire plane just falls with the rear end pointing straight down? Because if wind is no longer passing over the wings, then this includes ...
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19 votes
3 answers
5k views

What role did the RAT (Ram Air Turbine) play on US Airways flight 1549?

An article in June 2018 Flying Magazine regarding the RAT by a Rob Mark explains that Capt. Sullunberger deployed the RAT for additional power to guide the plane down to the safe ditching on the ...
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19 votes
3 answers
36k views

How high can propeller airplanes fly?

Is there a maximum height a propeller airplane could fly? Some lower bounds for maximum flying altitude: 12,000m (39,370ft): Antonow An-70, produced 1994 12,310m (40,387ft): Lockheed Martin C-130J ...
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19 votes
3 answers
2k views

Can a four-engine aircraft with limited fuel gain extra range by shutting down one of its engines?

I was reading the book Vulcan 607 by Rowland White who examines the details of a British bomber's mission during the Falklands War in 1982. At some point, the author wrote about the fuel shortage ...
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18 votes
3 answers
11k views

Why did the turbojet replace the piston engine?

Many people say that this was because aircraft powered by turbojet engines were faster during WWII. However the Grumman F7F-4N Tigercat, a fighter powered by a piston engine, flew at a maximum speed ...
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18 votes
6 answers
8k views

Why are aircraft tyres not grooved horizontally?

Why are aircraft tyres not grooved horizontally like vehicle tyres? If the tyres are grooved horizontally won't it help in achieving more friction and reduce the chances of veering off?
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18 votes
5 answers
4k views

Why was a Lockheed L-1011 chosen by Orbital ATK for its Pegasus launches?

Not sure whether this fits better here in Aviation, or would be better suited for Space, but since the question is about a terrestrial aircraft, I'll start it out here. The topic of my question is ...
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18 votes
2 answers
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What are the most powerful airplanes that ever flew?

This question What are the least powerful airplanes that ever flew? made me wonder what the most powerful manned airplanes are that ever flew. There are two sensible categories, I suppose: Most ...
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18 votes
7 answers
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Why are older airplanes still in use?

It is normal to see older planes (20+ years) quite frequently. In fact, a few months ago I saw a plane over 50 years old (not in a museum but on a runway, about to take off). Comparing to cars, there ...
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18 votes
4 answers
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How does flight duration affect the hourly fuel consumption in heavy aircraft?

A 15 hour flight across the Pacific obviously requires more fuel than a 7.5-hour transatlantic flight. How significant is the hourly fuel consumption increase due to the additional fuel carried at ...
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18 votes
4 answers
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Why is the nacelle outlet of the tail engine of the L-1011 Tristar lower than the engine itself?

I've noticed that the nacelle outlet of the Lockheed Tristar is situated below the engine itself. It is at the end of the fuselage. The nacelle outlet of the tail engine of the DC-10 on the other hand,...
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