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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57
votes
5answers
13k views

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 ...
31
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4answers
19k views

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 ...
10
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2answers
19k views

How can I calculate the fuel consumption of an Airbus 320-200 at various loads?

I want to know: What is the fuel consumption of an Airbus A320-200 - 180 Seats, at 100% load factor for a distance of 2000 km? What is the fuel consumption of an Airbus A320-200 - 180 Seats, at 80% ...
34
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4answers
29k views

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?
25
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2answers
6k views

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 ...
42
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8answers
21k views

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 ...
37
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4answers
35k views

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?
17
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2answers
8k views

How is minimum runway length related to V1?

1) Is $V_1$ used to determine minimum runway length? How is $V_1$ calculated? 2) If it is used to determine the minimum runway length, and for example we have a runway of 8000 ft and my airplane's ...
16
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2answers
6k views

Why would maximum fly-time (endurance) not coincide with max L/D operating point?

This question is motivated by another SE Aviation answer where @Peter Kampf writes the following two useful bits of information: Aircraft like to fly near their optimum L/D ratio, where drag ...
12
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2answers
3k views

Under what conditions can the maximum angle of climb be achieved for jet and propeller aircraft?

I know that the maximum angle of climb is reached at maximum specific excess thrust (S.E.T.) for jet airplanes, or minimum drag or maximum $\frac{L}{D}$. Is this true, and if yes, is this valid also ...
16
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2answers
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Why can't model aircraft be used to discover spin and stall behavior of manned aircraft designs?

I was reading some literature on stalls and spins (which are almost always preceded by a stall) of aircraft when a thought hit me. Why can't a model aircraft (1/4 scale of manned aircraft) be used to ...
11
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2answers
2k views

How much fuel is burned to carry the trip fuel?

For rockets, there is a rule of thumb that says for each kilo of fuel put into orbit, 7 kilos is needed to get it there. For long and ultra-long flights, it feels intuitive that some very significant ...
6
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3answers
4k views

Why are the top speeds for jet engines higher than for propellers?

I realize turbines are more efficient than piston engines, but if that were true, then why don't turbo-props reach jet speeds?
19
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3answers
32k 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 ...
20
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10answers
6k views

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?
7
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2answers
12k views

Where is the spanwise flow? How does the span wise flow point the air towards the wingtip?

If you search Google for span wise flow, the first result under the pictures tab is a image of a wing with the span wise flow at the trailing edge: (Source) If you look at some other photos you ...
8
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3answers
18k views

What is the difference between Assumed Temperature and Derate takeoff thrust?

Airlines like to avoid a full thrust takeoff as it increases the wear on the engine. There are two methods to achieve this: Assumed Temperature and Derate. In the Assumed Temperature method, the ...
34
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7answers
8k views

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 ...
17
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2answers
6k views

Why is max endurance different for jet and props?

Max endurance speed is not the same for gliders, propeller planes (also for turbo prop, right?) and jet planes. While for for jet planes max endurance is at the minimum drag speed ($V_{md}$), for ...
11
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2answers
5k views

How (and why) does engine thrust change with airspeed?

I'm interested in how the thrust of a turbofan engine is affected at higher airspeeds (TAS). I know (I believed) that engine thrust(at constant N1) was relatively constant like in the following graph (...
24
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5answers
5k views

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 ...
4
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2answers
411 views

Would an accurate weight of a loaded aircraft be helpful?

If a commercial aircraft's actual weight at takeoff is accurately known (instead of being estimated), can this help with use of thrust, optimal altitude, etc and therefore fuel savings, emissions etc.?...
35
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3answers
48k views

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 ...
7
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3answers
2k views

What is the relationship between power and fuel efficiency?

We were having a discussion in our ground school that power will make the plane ascend or descend and that you use the stick for speed, forward for higher speed and back for slower speed. So does that ...
10
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3answers
8k views

How does the efficiency of a piston aircraft change with altitude?

Turbine aircraft are more fuel-efficient, per mile, the higher they fly and this is for two reasons: drag depends mostly on indicated speed, but the same indicated speed corresponds to higher true ...
9
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2answers
4k views

Which aircraft endure the highest Max Q's (aerodynamic pressure)?

What are the highest aerodynamic pressures encountered in any aircraft? And does this limit the maximum speed of any aircraft at certain altitudes? Broadly, 'how fast can you go [at a given altitude]?'...
6
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2answers
4k views

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

Figure 10-5 of the FAA's Pilot's Handbook of Aeronautical Knowledge shows: I didn't think $L/D_{MAX}$ coincided with $D_{MIN}$. Is this Figure accurate?
5
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4answers
2k views

Are we changing the angle of attack by changing the pitch of an aircraft?

For example: if I pitch the airplane up, but also increase power and am able to maintain the same speed, then no, the AoA hasn’t changed, although it may have varied in the transition between one ...
15
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2answers
23k views

What is the difference between rate of climb and climb gradient?

I am currently trying to study aircraft performance and I have some difficulties distinguishing between rate of climb and climb gradient. Can someone explain what are the differences between the two ...
12
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2answers
14k views

What are Runway Declared Distances?

Perusing through the A/FD in the United States I see that some runways have declared distances while others do not. What is the meaning of: TODA TORA ASDA LDA
8
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3answers
3k views

Why is stall speed listed in a POH?

In this comment on this question about stall warning systems, it was stated that: You can stall at any airspeed (see this question and this one) and in any attitude, only the AoA is important ...
7
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2answers
13k views

What determines the “acceleration” and “thrust reduction” heights?

Thrust reduction height is the height at which automatic thrust reduction from takeoff thrust to climb thrust happens. And acceleration height is the height at which you start accelerating the plane ...
29
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9answers
38k views

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?
27
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4answers
20k views

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 ...
11
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4answers
4k views

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

How does the 'double bubble' fuselage cross-section of the "Double Bubble D8" aircraft (developed by MIT for NASA) help improve overall efficiency by around 70%? Image credit: NASA/MIT/Aurora Flight ...
7
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1answer
4k views

How can we determine the maximum camber and thickness for airplane wings?

I want to know if there are any standard factors for determining maximum wing camber and thickness for heavy and light airplanes? I'm using an optimization process to find the best wing shape to ...
18
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6answers
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?
21
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7answers
35k views

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 ...
6
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3answers
5k views

Why is managing CG (centre of gravity) important?

Why do people have to worry about CG? Is it primarily due to fuel penalty, or take-off and landing performance, or is it mostly just to keep the aircraft from tipping over during loading and unloading,...
10
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2answers
4k views

How does the position of vortex generators on engine cowlings affect flight?

I know what vortex generators (VGs) do. My question is: How come some aircraft have VGs on both sides of the engine, whereas other aircraft have them on the inside only? For example, in this picture ...
4
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1answer
8k views

How does altitude affect the speed of sound?

I read once that the speed of sound decreases as altitude increases. I wonder if that's true and, if so, are the pressure waves made at high altitude lesser than the ones at low altitude because of ...
3
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2answers
255 views

Can lift be equated to how much air is moved?

The explanation for lift that I find easiest to visualize is that air is deflected downward by the wing. This downward action causes an equal and opposite reaction of an upward force against the plane,...
25
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3answers
37k views

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), ...
53
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2answers
28k views

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 ...
20
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2answers
3k views

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 ...
21
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4answers
7k views

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 ...
6
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2answers
23k views

What is the purpose of flutter testing?

All I am aware of is that flutter testing involves the aircraft shaking violently. How is a flutter test performed and what is its purpose?
4
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1answer
1k views

What is the effect of airflow speed on separation?

We know that in real viscous flow, boundary layer exists around the airfoil and there will be a separation point which flow starts to separate from the back of the airfoil( velocity gradient equal ...
27
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3answers
10k views

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?
18
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7answers
7k views

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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