intake lip

Ramjets try to exploit the very high dynamic pressure within the air approaching the intake lip.

A detached normal shock wave forms just ahead of the intake lip and 'shocks' the flow down to a subsonic velocity.

As the flight Mach number increases, the conical shock wave becomes more oblique and eventually impinges on the intake lip.

Consequently, the intake capture area is less than the intake lip area, which reduces the intake airflow.

Variable geometry intakes, such as those on Concorde aircraft, vary the ramp angle to focus the oblique shock wave/s onto the intake lip.

The resulting flattened nacelle bottom and intake lip yielded the distinctive appearance of the Boeing 737 with CFM56 engines.

Ideally, the oblique shock wave should intercept the air intake lip, thus avoiding air spillage and pre-entry drag on the outer boundary of the deflected streamtube.

The engine intakes had fixed rectangular geometry and fuselage splitter plates, plus a set of spring-loaded auxiliary inlets behind the intake lip for increased airflow in ground running.

At zero airspeed (i.e., rest), air approaches the intake from a multitude of directions: from directly ahead, radially, or even from behind the plane of the intake lip.

This resulted in several changes including the addition of a tailcone, sharpening the radar nose profile, thinning the intake lips, and reducing the cross-sectional area of the fuselage below the canopy.

From another point of view, like in a supersonic nozzle the corrected (or non-dimensional) flow has to be the same at the intake lip, at the intake throat and at the turbine.

Overfuelling the combustor can cause the normal shock within a supersonic intake system to be pushed forward beyond the intake lip, resulting in a substantial drop in engine airflow and net thrust.

As the Lightning accelerated through Mach 1, the shock cone generated an oblique shock positioned forward of the intake lip; known as a subcritical inlet condition, this is stable but also produces inefficient spillage drag.

Former North American F-86 Sabre pilot Jerry Noel Hoblit recalled being in awe of the F-105's size after seeing it for the first time; he could not manage to reach the air intake lip even with a running jump.

The TSR has a number of interesting technical features: the engine air intakes feature fixed shock cones which are supplemented by additional air-intake doors behind the intake lips and four-petal airbrakes similar to those on the Republic F-105 Thunderchief.

However, if the engine is throttled back, there is a reduction in the corrected airflow of the LP compressor/fan, but (at supersonic conditions) the corrected airflow at the intake lip remains constant, because it is determined by the flight Mach number and intake incidence/yaw.