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
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
  • 74k
71 votes
3 answers
18k 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 ...
RoboKaren's user avatar
  • 8,071
19 votes
10 answers
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?
Quora Feans's user avatar
  • 3,681
24 votes
6 answers
10k views

In what way are the Concorde's engines considered efficient?

The Concorde is powered by a bunch of Rolls-Royce/Snecma Olympus 593 turbojet engines. Much has been said about how efficient they are at speed, and the fact that they allow long-range cruise at Mach ...
ithisa's user avatar
  • 1,702
13 votes
7 answers
8k views

What is the fastest possible transatlantic flight today?

I'm working on a novel that, as part of the backstory, requires samples of a biological agent to be flown from Incirlik Air Base to labs across Europe, and then finally from the UK to the US. In the ...
MG1981's user avatar
  • 375
30 votes
4 answers
22k 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 ...
Lnafziger's user avatar
  • 58.9k
13 votes
2 answers
6k views

Why are birdlike airfoils not used?

Here are two airfoils (lets focus on Re 100,000): SD7043-il which is simple to build and has a glide ratio of about 60 e376-il a birdlike and much harder to build if using paper or similar due to the ...
GRASBOCK's user avatar
  • 235
17 votes
4 answers
3k views

Why does the U-2 Dragon Lady not have swept wings?

Swept wings increase the critical mach number for aircraft with otherwise identical wings (Source 1). The U-2 Dragon Lady is limited in altitude by its critical mach number, as it needs more speed in ...
Nelson's user avatar
  • 431
11 votes
4 answers
5k 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 ...
Victor Juliet's user avatar
6 votes
2 answers
5k 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?
user avatar
2 votes
3 answers
6k views

What are some advantages and disadvantages of have the wing on top of the airplane? [duplicate]

Most commercial airplanes have the wings on the bottom of the aircraft to lift the body better, but what about the sugar volt concept that has the wing on the top
Ethan's user avatar
  • 9,349
13 votes
2 answers
3k views

Can ekranoplans (GEV) be more efficient than traditional airliners?

Ekranoplans or Ground Effect Vehicles (GEV) fly low enough to the ground that their wings stay in the ground effect. This increases lift and efficiency. But GEV fly in the lower atmosphere (...
RoboKaren's user avatar
  • 8,071
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
3 votes
1 answer
245 views

How high could modern transonic commercial transport designers reasonably push L/D ratios?

One facet of the evolution of commercial transonic transport design since 1970 years is that L/D ratios (alternatively, the M * L/D) have increased only mildly over time. For example, see the ...
interested22's user avatar

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