A turbo shaft engine is a turbine engine that powers a helicopter, vs a turbo prop engine powers an airplane propellor.
Then a Garrett TPE331-X is a turbopropshaft.
and a PT6-X is a wannabe helicopter engine.........?
The Allison llike the PT6 is a free turbine engine, unlike the Garrett and similar which are fixed shaft turbines.
'tis indeed pressurised and why 4 pax with full fuel is about it.
It may have had a Conitinental TSIO 520 =
Turbo
Supercharged
Injected O-520cu inches when it left the factory but someone, I suspect Soloy has clapped an Allison on it.
The greatest helicopter engine that never made it as a turboprop. Ask a Gomad operator what he thinks of the Allison.
About the only thing that made sense in Check 6 post is that
there is more to this story than the pilot is revealing.