Linked Questions

59
votes
4answers
29k 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, ...
24
votes
7answers
24k 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 ...
11
votes
5answers
7k 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?
18
votes
2answers
9k 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 ...
25
votes
3answers
2k 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?
15
votes
2answers
5k 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 ...
4
votes
1answer
4k 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 ...
1
vote
2answers
966 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?
11
votes
2answers
4k 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 (...
6
votes
1answer
5k 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 ...
6
votes
3answers
2k 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 ...
8
votes
3answers
742 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?
5
votes
1answer
233 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?
0
votes
1answer
725 views

Is it possible for an airplane to produce thrust from compress air without using fuel? [closed]

Is it possible for an airplane to fly as it compress the atmospheric air during flight?
0
votes
1answer
385 views

Is it possible to create a direct supersonic airflow to a turbofan's afterburner in order to enhance the performance or reduce the fuel consumption?

so I found out that SR-71 Blackbird is using what's called "turboramjet" and I find the idea a bit appealing since they say with such engine, the Blackbird is more fuel efficient at it's top speed. I ...

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