Linked Questions

49 votes
3 answers
44k views

Why are the Boeing 737 nacelles odd shaped?

Why is a Boeing 737 NG engine not completely round in shape? It seems to be flat at the bottom and round at the top and sides. Earlier Boeing 737 versions (100 and 200) seem to have a more rounded ...
Srikanth's user avatar
  • 591
34 votes
6 answers
10k views

Why do we never see high-bypass turbofan engines sharing the same nacelle on large airliners and similar aircraft?

I'm talking about this sort of thing (this is the fictional airplane from Casino Royale), rather than two (or more) engines per wing in individual nacelles: If we ignore the weird 'drop tanks' on the ...
mdunsmuir's user avatar
  • 451
27 votes
4 answers
39k views

Why do turbofan blade tips exceed the speed of sound while prop tips should not?

It seems that the tips of the fan of a turbofan engine can and do break the sound barrier: The GE-90 has a fan diameter of 3124 mm and a rotational speed of 3475 RPM. Their circumferential velocity ...
FreeMan's user avatar
  • 16.4k
17 votes
5 answers
12k views

Why do most military aircraft use different engines than commercial aircraft?

Why do most military aircraft and helicopters use different engine technology (fighters, B52, U2, etc) than most commercial aircraft? [I removed the use of axial terminology]
jwzumwalt's user avatar
  • 11.5k
29 votes
2 answers
11k views

What are those hatches on the engines of a B-2 that are open during takeoff?

I just watched this drool-inducing video of Northrop Grumman B-2 Spirit, And noticed that there are a couple of hatches near each engine, which were open: I initially thought they were open for some ...
sampathsris's user avatar
20 votes
2 answers
26k views

Why do military turbofan engines use a low bypass ratio?

I know that the most civilian engines use a high bypass ratio which is good for fuel economy and noise reduction. What prevents military engines from using the same technology instead of opting for ...
Anarach's user avatar
  • 393
3 votes
4 answers
11k views

Why are the Boeing 747-8 engines on the wings spread apart? [duplicate]

I ask this because the Boeing 747-236 had the engines close together while the 747's have them spread apart. Does it have anything to do with the amount of thrust of the aircraft? Look at how spread ...
Ethan's user avatar
  • 9,359
15 votes
3 answers
3k views

Do nacelles around aircraft engines help in reducing the engine sound?

I know that the nacelles around the aircraft engines are actually a housing and are generally lightweight and have may components like inlet cowl, fan cowl, etc., but do they help in reducing the ...
NitinG's user avatar
  • 6,889
16 votes
1 answer
11k views

What is the purpose of the inlet doors of the Pratt & Whitney JT3D?

I have a question about the 707 Engine Inlet Doors, according to Wikipedia the Pratt & Whitney JT3D inlet doors purpose is to provide additional air. Is the thrust higher on more air intake? And ...
TesterMen Tester's user avatar
9 votes
1 answer
7k views

How does a supersonic jet engine differ from a subsonic jet engine? [duplicate]

All jet engines have the same method of air flowing into the engine, which is compressed and ignited. What can engine designers do to make an engine design create more thrust? For example, what is ...
Ethan's user avatar
  • 9,359
5 votes
2 answers
2k views

How does a subsonic jet engine intake design ensure correct air intake?

I think I understand that inlets are there to slow down the airflow and increase the pressure to stop the compressors stalling?. If this is the case, I don't understand how the nacelle or intake ...
Zak's user avatar
  • 105
6 votes
1 answer
306 views

Does the stream of engine thrust act as a good drag shield against the nacelle?

Taking a look at the typical large engine of a commercial plane, it looks rather unstreamligned. Nacelle drag is significant IIRC. However, then I suddenly remembered these engines produce a large ...
DrZ214's user avatar
  • 17.8k
0 votes
1 answer
290 views

Why are inlet vanes used instead of variable geometry inlets to prevent compressor surge/stall?

Jet engine core axial compressors (that of subsonic turbofans anyway) are designed to keep air flowing the right way at max RPM(or close to it). Below that, the airflow slows more and more, and ...
Abdullah is not an Amalekite's user avatar