| Inlet Spike | |
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At Mach 3.2 cruise, over 80 percent of the thrust created comes from the inlet, only 20 percent from the engine. The purpose of the inlet spike was to control and position the supersonic air from entering the engine. The sharp pointed movable spike was locked in its full forward position at subsonic speeds. As speed increased, the spikes unlocked above 30,000 feet at 1.6 Mach and moved aft into the throat of the inlet on a programmed schedule, depending on Mach number. The faster you flew, the further aft they traveled, approximately one and five-eighths inch per 0.1 Mach. |
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Each spike was moved by a large hydraulic actuator, to a maximum travel of 26 inches aft into the inlet. The hydraulic spike actuator had to be able to withstand air pressures exceeding 15 tons under certain air flow conditions. To show the pilot the precise position of each spike as it moved aft into the inlet, a spike indicator in the cockpit had needles for each inlet. As each spike slowly moved aft, their conical shape increased the captured air stream area by 112 percent and reduced the throat area by 54 percent. |
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| © Copyright Richard Graham | |
