Any gas turbine engine, large or small, P20 to GE 90, which is not behaving correctly needs to be thoroughly examined by a professional, manufacturer or authorised service agent, not the “experts” on RCU.
That extremely high tailpipe temp. might have led to turbine “creep” which could, in turn, lead to turbine failure.
The consequences of a malfunctioning engine could be dangerous or even catastrophic. Ask GE , P &W or RR, they've all had their serious failures.
That engine is not in good health, even sounds rough after start.
Last edited by David Gladwin; 12-11-2020 at 02:14 AM.