The assist was on and had flown several times ( Maybe 10 Flights) without issue. Switch it on, stabilization was fine, but no tuning was carried, then around five minutes into the flight loss of turbine control about 20% thrust, which then meant flying to flame out, no effect by disarming or turning it off. On the previous loss of control flights, trimming the engine off failed to shut off the turbine, other channels were normal. After landing the turbine software does not initialise the HDT. The turbine pump has to be stopped by pulling the power.