- Dassasult Rafale ($Ma \leq 1.8$)
- General Dynamics / Lockheed Martin F-16 C/D Block 30/32 Fighting Falcon ($Ma \leq 2.0$)
Are there any more examples?
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Are there any more examples?
A pitot intake will decelerate supersonic flow in one single, straight shock, while a ramp or cone intake will do this in several oblique shocks. It takes its name from the pitot tube, which in turn is named after the French physicist Henri Pitot who invented it to measure flow speed.
The objective of an air intake is to supply the engine with a uniform flow of air at approximately Mach 0.4 to 0.5. At higher flight speeds as much of the kinetic energy of the flow as possible must be turned into a pressure increase. Doing so efficiently reduces the work of the engine's compressor and increases mass flow, and consequently thrust. A pitot intake will have the lowest mass and complexity of all intake types and is the preferred choice as long as the pressure recovery can be performed efficiently.
A shock is the only way to decelerate supersonic flow. While the flow speed tangential to the shock will not be changed, the normal speed component is reduced downstream of the shock, approximately to the inverse of the upstream Mach number. The bigger the jump, the higher the friction losses in the shock become, the air is heated instead of compressed and pressure recovery suffers. Generally, those losses are acceptable up to a maximum flight speed of Mach 1.6. The lower mass of the pitot intake will make it more attractive, while for higher speeds the deceleration has to happen over several oblique shocks which are triggered by a spike or a ramp ahead of the intake lip.
Therefore, all supersonic jets which were designed to fly at less than Mach 1.6 use a pitot intake for mass and complexity reasons. This includes the smaller US jets (F-100, F-101, F-102, F2Y, F-8, F-16) and their counterparts in the Soviet Union (MiG-19, Yak-27, Yak-38M), Sweden (Saab 32, Saab 35, Saab 37), France (Super Étendard), Egypt (HA-300), Taiwan (Ching-Kuo) or Korea (T-50).
Pressure recovery measurements from the YF-16 (source: "Fundamentals of Fighter Design", RAeS Lecture by Ray Whitford, Cranfield University). The loss in efficiency above Mach 1.2 (left; 1 on the y scale denotes full conversion of kinetic energy into pressure) is readily apparent. This is mitigated by the pre-compression from the forebody at increasing angle of attack (right). The result is higher efficiency just when it is needed most, namely in turning supersonic flight. The same trick is used by the Rafale, and the wing root does this pre-compression in case of the F/A-18 and the Ching Kuo.
Top view of the right XB-70 intake at Mach 3 (source: "Fundamentals of Fighter Design", RAeS Lecture by Ray Whitford, Cranfield University). At Mach 3, a single shock intake would be grossly inefficient. Now a cascade of ever steeper oblique shocks is needed, culminating in a last straight shock. A multitude of moving ramps is required to adjust the geometry for the actual Mach number, and the square geometry, which is required for this flexibility, makes the intake tube much heavier (it is a pressure vessel, after all!) than the round tube of a pitot intake.
Almost all the jet aircraft in the dawn of jet aircraft used the pitot intakes, like the Gloster E.28/39, MiG-15 and F-86A Sabre.
This trend was followed by the second generation supersonic combat aircraft, a good example of which would be MiG-19.
The TF-102A, the trainer version of F-102 Delta Dagger had pitot inlets mounted on the sides below, similar to the Rafale; the single seat version had a different pitot inlet (on the sides) though.
Image from 456fis.org
Also, the F-100 Super Sabre used a pitot inlet.
F-18A Hornet also uses a similar intake. The Taiwanese F-CK-1 Ching-Kuo also has pitot inlets; in fact, the aircraft looks like a cross between F-16 and Rafale.
Image from Wikimedia Commons