Jet engine shapes

[lovejoy0120]

Why are engines on some commercial aircraft shaped a bit like a half-barrel and others aren't ?

Thanks

[heathfield]

The 'half-barrel' ones are 'turbofan' engines, using a far bigger front-end fan. This makes the engine seem short, but only because of the much increased diameter.

[Clanad]

In addition to heathfield's uniformly accurate information, you'll notice the bottom front half of the wing mounted engines on Boeing 737 aircraft are seemingly flattened rather than full round. This is to achieve the design required ground clearance when the landing gear struts are compressed during landings...

[BillyNoMates]

And to reduce the possibility of FOD - (Foreign Object Damage) I.e. the ingestion of debris which could damage the engine.

[lord molly]

wing mounted jet engines are usually turbo fans, and appear like oil drums in designs. other jet engines are more powerfull, and are for high-preformance aircratf, usualy turbo jet engines or ram jet engines. they are not used commercially as they are only efficient when in small size. they als produce an awfull ammount of noise, so not accepible for passenger travel

[Clanad]

Actually, turbo-jet engines are the standard of the airline industry. The most popular engine, until the last several years has been the axial flow Pratt and Whitney JT8D. The turbo-fan engine is, in reality, a turbo-jet engine with a shrouded "propeller" for added performance... As lord molly does correctly identify, the ram jet engine isn't used commercailly for various reasons, including his/her examples. However, an extremely unique engine developed by Pratt was the J58 for the SR-71 Blackbird military, Mach 3.5 capable. surveillance aircraft. It was, in effect, a ram-jet engine inside of a turbo-jet engine...