Linked Questions

67
votes
5answers
37k views

What determines the maximum altitude a plane can reach?

What factors determine the maximum altitude for a plane? Is it limited by wing design, engine thrust, and so on? Is there a formula by which one can calculate the maximum altitude a plane can reach?
67
votes
10answers
85k 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 ...
67
votes
3answers
14k views

Are we at peak speed efficiency for jet airliners at Mach 0.85?

The cruising speed of large jet airliners has not increased in the past four decades. The 747 cruised at Mach 0.85 and the new Dreamliner 787 also cruises at Mach 0.85 even though it was designed 40 ...
37
votes
4answers
17k views

Why do private jets such as Gulfstream fly higher than other civilian jets?

I heard in a TV show that private jets such as Gulfstream can fly at about 50,000 ft, higher than other civil jets. Is it an aerodynamic reason (lighter aircraft to be sustained in a less dense air) ...
34
votes
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 ...
31
votes
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 ...
24
votes
4answers
5k views

Why are heavy flaps better than just a bigger wing?

Flaps increase lift during landing and T/O. But when retracted, they do nothing. The space needed to stow the common fowler flaps can't be used for anything else - fuel or structure. Extended flaps ...
23
votes
6answers
9k views

Why then don't aircraft fly even higher, for even greater efficiency? [duplicate]

After reading various superb QA on here I now see that (basically) aircraft are more efficient per passenger-mile, at higher altitudes. Why don't we go even higher, than current typical airliner ...
17
votes
3answers
5k views

Can high-bypass turbofans cruise at high altitude?

They have talked for years about re-engining the B-52 with something more modern than its TF33-P-3/JT3D turbofans, which are fairly low-bypass (1.42:1 for the JT3D). Modern engines are much higher ...
15
votes
3answers
6k views

What are the limiting factors for high altitude planes (e.g: U2 or SR71) preventing them from going higher?

I'm curious as to why planes like the U2 Dragon Lady and the SR71 Blackbird couldn't fly higher. What physical constraint set their operational ceiling? Pilots wore spacesuits, so that wasn't the ...
14
votes
3answers
3k views

Why were the windows on the Concorde about the size of a hand?

I just saw a comparison between the 787 and Concorde windows. I could be wrong but it almost seems like a hand could cover the majority of the window.
10
votes
2answers
7k views

What is Tropopause height, and how is it determined?

I have seen the term "Tropopause height" used in a flight navigation plan. What is it and how is it determined?
9
votes
2answers
2k views

What is the one-engine-inoperative maximum range flight configuration?

I was talking with a friend about what things would happen if you experienced engine problems in cruise. We were wondering the following: What things would need to be changed to arrive in the optimal ...
9
votes
1answer
4k views

What engine power setting is used during cruise?

I am trying to work out what engine power setting is used during the cruise phase of commercial flights but I can't find anything about it in the usual spots. Anyone have any idea what percent of ...
7
votes
1answer
1k views

Based on this fuel flow chart, why isn't it more optimum to remain at an intermediate altitude rather than climbing?

I am having a bit of confusing as to why people say planes gets more efficient as they fly higher. Because on a typical long haul flight the Fuel Flow of the aircraft will obviously be much more that ...

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