Inlets Most modern passenger and military aircraft are powered by gas turbine engines, which are also called jet engines. There are several different types of gas turbine engines, but all turbine engines have some parts in common.
All turbine engines have an inlet to bring free stream air into the engine.
The inlet sits upstream of the compressor and, while the inlet does no work on the flow, there are some important design features of the inlet as described on a separate slide. As shown in the figures above, inlets come in a variety of shapes and sizes with the specifics usually dictated by the speed of the aircraft. On a typical subsonic inlet, the surface of the inlet, from outside to inside, is a continuous smooth curve with some thickness from inside to outside. A subsonic aircraft has an inlet with a relatively thick lip. The inlet lip is sharpened to minimize the performance losses from shock waves that occur during supersonic flight.