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Are there aerial vehicles which have multiple inlets with air ducts (shaped in S-forn) , which all lead the air to one single turbojet engine?

I have not enough space to put just one inlet area on my vehicle, so I thought about using inlets, located at the sides.

I think it is really difficult to combine the air of all inlets so that there is a uniform air flow in front of the turbojet - because I don't have much space inside my vehicle.

Besides, I think is is really challenging when it comes to some maneuvers, where the flow sometimes will not flow through one of these inlets.

What do you think and do you know any vehicle from history?

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    $\begingroup$ Aren't almost all single-engine, multi-intake fighters fit this criteria? F-35, almost all Mirage's, Gripen, HAL Tejas, etc etc? $\endgroup$
    – DeepSpace
    Commented Mar 22, 2021 at 17:14
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    $\begingroup$ And the A-4, F-104, F-105, F-106, F-20, U-2, ... $\endgroup$
    – Fred Larson
    Commented Mar 22, 2021 at 17:46

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It’s common on military fighters. For instance most single engine fighters eg F-35, JAS-39, J-18, etc. will have a pair of inlets on either side of the fuselage feeding these single engine. Some aircraft will have auxiliary air intakes eg B-2, F-117, F-22, MiG-29/35, SU-27/30/33, etc. to provide additional air on takeoff or other high power settings or to provide protection against FOD ingestion.

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Quite a few planes fit your description of multiple (two) inlets for a (single) turbojet. The latest would be the F-35, other (as mentioned in the comments are numerous: JAS gripen, most Mirages, BAe Hawk, F-104 Starfighter etc.

I would say, without much thinking, that single intake jets with body mounted single engines are actually more rare. Even with a single intake, the air rarely has a straight path to the engine. Take F-16 for example, the air has to flow around front landing gear bay, and with MIG 21, the damn pilot sits in the way of a straight airflow.

The airflow to the compressor does not have to be absolutely uniform, the flow of air will quickly equalize across the compressor stages. The first stage might experience some extra stresses from uneven flowfield, but as the widespread use of multiple intakes shows, these stresses can be mitigated to more than acceptable levels.

As for maneuvers that would block airflow to the engine from one inlet: I don't think such maneuvers exist. A fighter jet can do a tail slide, and it's engine(s) keeps running. Even if the plane is going backwards.

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    $\begingroup$ Airflow is an issue mainly at supersonic speeds. It was a problem for the Sr-71. In too sharp turn or side-slip at cruise speed (M3.2) the shock wave from the shock cone (the sharp spike in the middle) would shift off the inlet lip, causing sudden drop in air flow and consequently engine thrust (called ‘inlet unstart’). But I don't think it affects any aircraft slower than M2. $\endgroup$
    – Jan Hudec
    Commented Mar 23, 2021 at 10:05
  • $\begingroup$ Oh, true, but I think it's safe to neglect past mach speeds here 😃 $\endgroup$
    – Jpe61
    Commented Mar 23, 2021 at 12:52
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    $\begingroup$ Darn pilots, always getting in the way! Also, "inlet unstart", what a lovely euphemism... $\endgroup$
    – FreeMan
    Commented Mar 23, 2021 at 18:33
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If you're designing a civilian aircraft, take a look at Diamond D-Jet.

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