Simviation Forums

Does anyone know why subsonic jet engine intakes are almost always round when looking at them from the front, while supersonic jets are kind of square?

I don't belive there is anything like that, and I can think of some pretty fast jets with round intakes (F-16, F/A-18A/B/C/D, SR-71). It might be because it is easier to increase or decrease the size of the intakes to limit airflow when it is square.
Or it could be just for design reasons.
I think the Valkyret would look cool with square intakes, kind of like a squished SU-27.

The only other item to consider is that high Mach aircraft tend to have some sort of boundary layer splitter, or suction device (like the plate found in front of the intake of an F-18A/C). This helps direct airflow into the engine while slowing it down to subsonic speed, so that the engine doesn't surge. Moving shock cones, like on the SR-71, likewise have the same effect. Aircraft with square inlets (F-14, F-15) have interior moving ramps in their intakes. So, anything goes, as long as there's some means to slow the air entering the engine.

Blackbird had round engines and intakes so did the EE Lghtning.

Ok then.  Guess I

Hi Harold,

Maybe "suge" isn't the appropriate term but it's like a hiccup. You have it pretty much correct in that the air has to be slowed upon entering the engine compressor, only to be spat out again at high speed. Here's a link that explains it better than I could.

http://en.wikipedia.org/wiki/User:Snipe ... onic_Inlet

Maybe some of these applications could help Harold?

http://www.fsworld.co.za/index_files/aeronautics.htm