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How do afterburning turbofan or turbojet planes prevent or minimize the risk of a flameout at nearspace altitudes such as Fedotov's Mig-25M that went higher than 115K ft (35 km) two times? At these altitudes the MiG's engines were shut down already (the plane was floating on inertia like a suborbital spacecraft), but they must have been shut down quite high anyway, 80 or 90 thousand feet perhaps. Is there a way we can get to know accurately the highest possible altitude for a particular jet engine to run? Is there a way for the pilot to know when they could shut the engine down before it does on its own in a flameout?

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    $\begingroup$ you seem to have created multiple accounts. Be aware that if you lost access to an account, you can ask for it to be merged to your current one. $\endgroup$
    – Federico
    Jun 7, 2022 at 12:14
  • $\begingroup$ @Federico Thank you but I don't really care. I'm unregistered. A new account forms when posting anything on another SE or when deleting the browser's cookies. $\endgroup$
    – Giovanni
    Jun 7, 2022 at 12:34
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    $\begingroup$ I am just mentioning in case you are not aware. registering allows you to keep the reputation and access to old posts you have made, in turn giving you access to more tools. You are more than welcome to ignore that if you wish. $\endgroup$
    – Federico
    Jun 7, 2022 at 12:50

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The engine flamed out on the way up. Inertia alone carried the Ye-155M to its record altitude. Its high speed and its high supersonic load factor of 5 allowed to fly a zoom climb where the pilot pulls into a vertical climb at an altitude which still supports a pull-up maneuver (which requires a flight speed near the airplane's top speed of Mach 3 for best results). This page lists the maximum altitude for sustained flight of the Ye-155M at 24,200 m.

The engine, a R15BF2-300, started life in 1958 as the power plant of several unmanned, supersonic reconnaissance airplanes (R15K, used on Tu-151 and -153 Yastreb). For this purpose it was of rather simple design with only 5 compressor stages and no bleed air for turbine cooling. Later it was upgraded for manned airplanes like the Ye-150 family, being the only low-cost solution to a high-altitude supersonic reconnaissance airplane. For the record-setting Ye-155M a sixth compressor stage was added, turbine temperature increased and reliability improved.

You might ask why so few compressor stages were sufficient for high altitude operation. The reason is supersonic flight: Most compression is from ram pressure in the intake, so the engine does not have to add much compression on top - or if it would, compressor exit temperature would be too high to add much energy from combustion before turbine entry temperature is exceeded.

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  • $\begingroup$ Years ago read Igor Belenko's story about his defection to Japan with a Mig 25, "Mig Pilot". He ended up flying for one of the US majors, American Airlines I think. $\endgroup$
    – John K
    Jun 7, 2022 at 21:15
  • $\begingroup$ @JohnK you surely mean Viktor Belenko, right? $\endgroup$ Jun 8, 2022 at 9:26
  • $\begingroup$ Yes Igor was some other guy lol. $\endgroup$
    – John K
    Jun 8, 2022 at 12:14

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