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denis r-e a écrit:...
même si j'ai été surpris d'apprendre que le MIG 25, annoncé à Mach 3,5) était limité à Mach 2,8 parce qu'au delà ses réacteurs s'emballaient et étaient bons à mettre à la casse ...
The engine provides massive thrust and high performance at altitude, but at a cost. At dry thrust the engine could produce 7,500 kilograms force (73.5 kN, 16,500 lbf); with afterburners the output is 11,200 kilograms force (110 kN, 24,700 lbf). This allowed speeds of up to mach 3.2 in the Mikoyan-Gurevich MiG-25 (which used two engines). However, at speeds above mach 3, the force of the engine sucking fuel through the pumps overwhelmed the pumps' ability to limit the flow. At this point, the engines effectively became ramjets, as air began to bypass the low pressure compressors, accelerating out of control until the pilot could regain throttle control through using firewalls or compressor stall, or the tanks ran dry. However, a more probable series of events would be the eventual destruction of the engine as the suction force of the compressors began to pull various engine parts through the ignition chamber and turbines. The engine also suffered from huge fuel consumption issues, especially at low altitudes (which is consistent with most turbojet engines). This was also a limiting factor in the engine's role in aircraft, as the Mig 25 had a maximum combat radius of 744 miles (without using afterburners and operating at optimum altitude and in optimum atmospheric conditions). The engines did give excellent performance at high altitude though, with good fuel consumption and speeds at 80,000 ft, which was considerably better than any Western aircraft at the time (early 1960s). The MiG-25 was able to supercruise. The R-15BD-300, in short, was known for ease of maintenance, performance, and good monitoring systems for both pilots and engineers.
A MiG-25 was tracked flying over Sinai at Mach 3.2 during this period. The MiG-25 oversped its engines, which led to their destruction.
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