Linked Questions

61 votes
4 answers
39k views

Why can't jet engines operate with supersonic air and how do they slow it down?

Typically jets cannot operate when intake airflow is supersonic relative to the engine. Why is this so? Also, why are scramjets able to use supersonic air? To slow down the air to subsonic speeds, ...
Dylan's user avatar
  • 1,115
27 votes
7 answers
33k views

Why are adjustable area jet engine nozzles mostly limited to military use?

It seems that only jet engines with afterburners use adjustable area nozzles (this means adjusting the area of the nozzle but not necessarily the direction). This includes most fighter jets, as well ...
fooot's user avatar
  • 73.4k
20 votes
2 answers
12k views

How is supercruise achieved?

Wikipedia article tells that supercruise is a condition when an aircraft can achieve velocities above Mach one without using the highly inefficient afterburners. But still, there are not a lot of ...
Victor Juliet's user avatar
11 votes
5 answers
10k views

Can a convergent nozzle be used for a supersonic jet engine?

Can a supersonic fighter incorporate a convergent nozzle or does it always have to be a convergent-divergent nozzle?
abdulhaseeb's user avatar
25 votes
3 answers
4k views

Why are turbofan inlets leaned/angled forward?

(Image Source: Wikipedia) Seeing that everything is radially symmetric (apart from the nacelle mount, naturally), I wonder why the inlet (the front part of the nacelle) is usually skewed?
Pavel's user avatar
  • 909
17 votes
2 answers
10k 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 ...
curious_cat's user avatar
  • 8,454
13 votes
2 answers
11k 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 (...
Darjan's user avatar
  • 1,157
9 votes
3 answers
6k views

Why is thrust available constant with speed for turbojet engines, when it varies with speed for turboprop engines?

Similarly, why is power available (nearly) constant with speed for a propeller engine, while it varies for a jet engine?
Nirmal's user avatar
  • 319
5 votes
4 answers
1k views

Why weren’t large, high-power radial engines built to take advantage of the Meredith effect?

Most aircraft piston engines fall into two general categories:1 Radial engines (radials for short2) have their cylinders radiate out from the crankshaft in a star pattern; they tend to have a blunt, ...
Vikki's user avatar
  • 28.4k
4 votes
1 answer
7k views

What advantages would a triangular shaped spy plane have over a an SR-71?

This is a picture of the supposed SR-72 Aurora. What kind of advantages would this have over the SR-71, in terms of its triangle design? Paper airplanes have the same shape, and fly really well. The ...
Ethan's user avatar
  • 9,349
1 vote
2 answers
2k views

Why wasn't a scramjet used for the Concorde?

Why didn't Concorde use a scramjet engine for supersonic flight, but it is used in the Airbus and Skreemr hypersonic flight concepts to achieve supersonic speeds?
kcihtrak's user avatar
  • 431
6 votes
3 answers
4k views

How does turbofan engine performance depend on speed and density altutude?

I am looking at a simulation engine (jsbsim). Their turbine engine simulation requires a function, given by table, of thrust at Mach number and density altitude. Engine definitions generated by their ...
Jan Hudec's user avatar
  • 56.3k
6 votes
1 answer
7k views

How does compression ratio change, if at all, from sea level to higher altitudes?

As I understand it, compression ratio is the max pressure inside the engine divided by the ambient air pressure. This is for turbojets and turbofans. Sea level pressure is about 100 kPa. An altitude ...
DrZ214's user avatar
  • 17.8k
6 votes
1 answer
2k views

Why is thrust said to be constant over speed for a jet engine?

I'm just interested in some basic facts regarding flight. On reading the rather "low level" book "Understanding Flight, David F. Anderson, Scott Eberhardt), I recently came up to the ...
MichaelW's user avatar
  • 251
5 votes
1 answer
279 views

Is a subsonic scram-jet reasonable?

By placing a de laval nozzle at the inlet, can the resulting supersonic airflow allow a scram jet to operate efficiently?
Steve Csosz's user avatar

15 30 50 per page