Linked Questions

66
votes
10answers
80k views

Why do jet engines get better fuel efficiency at high altitudes?

I'm told that this is true, but I can't imagine why. It seems like the fact that there is less air would make the engines less efficient... But that probably just shows how little I know about jet ...
41
votes
8answers
19k 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 ...
50
votes
4answers
9k views

Why are many jet aircraft designed to cruise around FL350-370?

If the flight distance permits, the B737-800 will cruise at FL350, the A320 a little bit higher... Flying at FL370. Photo: Live from the Flight Deck by GolfCharlie232 (reframed) Elements such as ...
30
votes
6answers
4k views

Why isn't the wing span of a certain airliner longer with the longer fuselage versions?

The Boeing 737 next generation models (700,800,900ER) all have the same wingspan at 117ft 5 in. Why doesn't the wingspan increase with bigger and longer models? With the 737-900 wouldn't you need a ...
20
votes
3answers
23k views

Why and when to use flaps?

On a commercial airliner, what is the purpose of the flaps? I understand that depending on which direction they move in, they can be used to decrease airspeed, but I don't know when flaps are used. ...
9
votes
4answers
5k views

Are strategic bombers still useful, or are fighters taking over this role?

During the mid 20th century and cold war, armies were having clear distinction between those aircraft designed as strategic bombers and those designed to be fighters for aerial combat. My ...
19
votes
2answers
20k views

How does chord length affect wing design?

In comments on the answer to a question about transonic speeds and control surfaces I came across this comment and I'm having a hard time understanding it. If you increase the chord, lift goes up ...
11
votes
4answers
3k views

Why do airfoil's trailing edges point downward?

The trailing edge of and airfoil is mostly pointing downward. Is there any reason for that? Down wash increases drag and down wash is due to the direction of air pointing down. If the trailing edge is ...
14
votes
2answers
9k views

What is the “area rule”?

The "area rule" states that the supersonic drag on an aircraft is related to the total area on part of the aircraft. What is the exact definition of the rule? Why does this happen?
8
votes
2answers
3k views

Do negative flaps increase glide ratio?

If I understand correctly, gliders uses negative flaps while crossing between 2 thermals, but I don't understand why. For me: positive flaps decrease sink rate but increase drag and thus worsen glide ...
5
votes
2answers
3k views

For a large commercial plane on landing, does the L/D ratio increase, decrease, or not change much?

Consider a large commercial aircraft coming in for landing. The exact part I'm interested in is the flare (where the aircraft noses up yet does not actually go higher above the ground), with flaps ...
4
votes
2answers
1k views

Does extension of flaps 1, 2, 5 or 10 increase descent rates?

Let's say you need greater descent rates than you can get with the full use of the speed brake in an airliner. Does it help to use the above flap positions in getting greater descent rates?
3
votes
2answers
974 views

Are high lift wings bad for faster speeds

I notice a trend in many aircraft designs. If the aircraft was designed to go slowly but have shorter takeoffs/landings they use airfoils with a high lift. However for long endurance flights they use ...
0
votes
1answer
1k views

Is pressure lower than ambient on the pressure (bottom) side of an airfoil? [duplicate]

I've been reading about this for quite some time and thought I understood it. Then somewhere someone mentions that air under the wing has higher velocity than ambient thus a lower pressure than ...
5
votes
1answer
588 views

What makes the loss of a flap track fairing strongly increase fuel consumption on Airbus planes?

Inspired from this question about the loss of a flap track fairing. In the answer by Thunderstrike, a part of the configuration deviation list of an Airbus A320 is linked. In it, it says: One ...

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