DG-1000T loses its sustainer propeller to a coupling bond failure
A DG-1000T lost its sustainer propeller in flight when the drive coupling failed; the departing propeller lightly damaged the fuselage and left wing, and both occupants were unhurt. The pilot had deployed the sustainer to gain height when a loud bang and an overspeed warning signalled the propeller had gone. He closed the throttle, shut off the ignition, retracted the engine and landed safely. The coupling had separated through its rubber element: the drive-side surface roughness needed to bond the rubber to the aluminium had not been achieved, and there were no inspection criteria for the finish. The manufacturer has changed the coupling.
- Sustainer deployed to climb: On a local flight the pilot deployed the DG-1000T's sustainer engine to gain height.
- Propeller detaches in flight: A loud bang and an engine overspeed warning signalled the propeller had detached from the drive.
- Coupling bond had failed: The drive coupling had separated through its rubber element; the surface roughness needed to bond it to the aluminium had not been achieved, with no inspection criteria.
- Engine stowed, safe landing: The pilot closed the throttle, shut off the ignition, retracted the engine, confirmed control and landed safely.
- Minor airframe damage: The departing propeller lightly damaged the fuselage and left wing; both occupants were unhurt. The manufacturer has changed the coupling.