The cause of the crash was engine failure due to compressor turbine blade separation.

Microturbines use just one moving part - a shaft on which a compressor turbine and permanent magnet generator are seated.

The gases are harnessed to drive the turbine wheel of the turbo on the hot side which is coupled to a compressor turbine wheel.

Same as the PT6T-3, except for the single power section contingency ratings and has PT6T-6 compressor turbine components.

This type of deterioration in engine performance parameters is a dependable indicator of progressive gas-flow inefficiencies, compressor turbine damage, and incipient engine failure.

Note, that transferring heat from the outlet (after the last turbine) to the inlet (before the first turbine) would reduce efficiency, as hotter inlet air means more volume and thus more work for the compressor turbine.