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Old 28th Feb 2011, 23:28
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FE Hoppy
 
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CF34s fitted to the e-jets have an overspeed protection function which will flame out and relight an engine who's N2 goes beyond the normal limit by approx 2%. As the FADEC uses N2 as a control input the overspeed is an indication of the fadec failing to control the engine. If the engine overspeeds 3 times in 30 seconds the fadec shuts off the fuel and signals an engine failure.

Better secure it than let it overspeed to destruction.

Gas turbines can flame out for lots of reasons but loss of oil will normally lead to a seizure if the engine is left to run. That can be quite dramatic too. I vaguely remember an engine detaching itself due to a seizure. Which is why we shut them down for low oil pressure usually.
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