9/11/2023 0 Comments F4 phantom cockpit layout![]() The two piece splitter type thing against the fuselage in front of the intake is what puzzles me. The shock wave reduced intake air to sub-sonic. Based on the speed of the air, these ramps located opposite the probes on the inside wall were positioned to create shock waves as has mentioned by Dosco. Pitot probes were located in each intake on the outer wall (sorry no pictures). The function of these was to control air flow to engines regardless of whether the aircraft was stationary on the ground or flying at Mach II. If you take a look down into the intake of the F4, you will see variable inlet doors or ramps. The F15 intake design was greatly influenced by the problems encountered in the F4 vari-ramp. As the flow distortion travels through the compressor, the FADEC will preferentially close the VSVs and smooth out the flow, thereby precluding stall conditions. Modern engines have VSVs (each ring is independently controlled) and FADECs (full authority digital engine control) that allow very precise engine control and do wonders to prevent compressor stalls. Probably less of a problem in pitch than yaw. Inlet flow distortions were bad in those days due to lack of effective engine control (see #2 above). "Aggressive yaw" control means that the pilot had to worry about vortex ingestion into the engine air intake. Compressor stalls are bad news because if they're bad enough they can break compressor blades, cause flame-outs, etc etc. The splitter functions only to prevent ingestion of the fuselage boundary layer into the compressor face of the engine.the reason for that is to prevent compressor inlet flow distortions which would have caused compressor stalls (the older F-4s (and older aircraft in general) didn't have effective variable-stator-vane (VSV) and/or main engine controls). By changing the angle of the ramp, the shock wave(s) can be controlled, etc etc etc.Ģ. The "shock cone" you're looking for is actually a 2 piece ramp that is formed by part of the splitter (flat) and a flat plate inside the intake. This could mean one of the intakes could get in the fuselage's aerodynamic shadow in some situations ? Has anyone heard of similar instances ?Īny other thoughts, or info, from someone here, on these intakes ?ġ. Aggressive yaw control by the pilot was the only way to prevent flame out" but have no evidence.Īnother interesting point in the letter says " I flew C and Ds and each one had a slightly different config. I suspect these BL control plates could then move to vary the intake-throath ratio. The reader speaks of "splitter vari-ramps" and says that "later F4 had active ramps". ![]() Of course, a vortex generator to keep the engine well fed at high AOA. It was not present on the prototype, and it looks extremely similar to the one seen on the unlucky CF105 Arrow. On the lower part of the control plate, a triangular extension can be seen. I have no info on wether there was also some other form of boundary layer control, such as aspiration. It probably caused a Cd increase in exchange for improved engine efficiency. This plate was obviously there to start a new, thin boundary layer at a short distance from the intake, avoiding the ingestion of the thick layer developing from the nosecone. Even Mig 21 had a variable geometry intake, thanks to a sliding nosecone.Ģ) A big boundary layer control plate. I found no specific info on the internal working of F4 intakes, so I wonder : had they some movable parts I'm not aware of ? Fixed geometry seems strange for such a sophisticated aircraft. Only, F15 air intakes had variable geometry, while it appears F4 ones were fixed. Probably they were 2D shock diffusers, the same principle used in F15 Eagle. These intakes have two features that strike the eye at first :ġ) no shock cone : something very different from, say, contemporary F104 or Mirage. There are many aerodynamicists here, and I think it's an interesting subject. He asked some info about the peculiar air intakes of that plane. I received a letter from a Forum reader who was lucky enough to be a F4 pilot.
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