Linked Questions

69 votes
10 answers
94k 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 ...
Jae Carr's user avatar
  • 24.2k
42 votes
8 answers
32k 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 ...
Lnafziger's user avatar
  • 59k
52 votes
4 answers
12k 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 ...
mins's user avatar
  • 75.3k
30 votes
6 answers
5k 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 ...
Ethan's user avatar
  • 9,359
19 votes
3 answers
30k 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. ...
spike.y's user avatar
  • 487
10 votes
4 answers
8k 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 ...
Trebia Project.'s user avatar
19 votes
2 answers
29k 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 ...
Jae Carr's user avatar
  • 24.2k
11 votes
2 answers
3k views

How have engineers managed to increase commercial airliner wing aspect ratios over time?

Over time, the wing aspect ratios of commercial airliners have increased. For evidence ,see the following data: 1980s: Boeing 747-400: 7.91, Boeing 757-200: 8.0 Boeing 767-300: 8.0 Airbus A310: 8.8 ...
interested22's user avatar
11 votes
4 answers
4k 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 ...
Selva's user avatar
  • 741
16 votes
2 answers
12k 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?
fooot's user avatar
  • 73.4k
8 votes
2 answers
5k 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 ...
Manu H's user avatar
  • 16.5k
5 votes
2 answers
5k 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 ...
DrZ214's user avatar
  • 17.8k
4 votes
2 answers
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?
lemonincider's user avatar
  • 7,565
4 votes
2 answers
2k 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 ...
YAHsaves's user avatar
  • 1,211
5 votes
2 answers
708 views

Are we on the "wrong boat" with eliptical spanload all these years?

In this video AL Bowers (former NASA chief scientis) talk how bell spanload solution can reduce OVERALL DRAG by 60%(11% reduction in total aircraft drag due to spanload, elimination of the tail ...
ROTOR's user avatar
  • 177

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