What happened
On 20 March 2011, a Thruster T600N 450, registration G-CCUZ, was conducting a training flight from Wickenby Airfield in Lincolnshire. Shortly after departing the airfield, the propeller and hub assembly became detached from the aircraft. Following the separation, the pilot performed a successful forced landing in a nearby field. There were two people on board the aircraft, and neither sustained any injuries.
The investigation
Investigators examined the aircraft and determined that the propeller flange had separated from the crankshaft. The inspection of the hardware revealed that all screws used to attach the propeller flange to the crankshaft had failed. Analysis of the components showed that several of these mounting screws had fractured some time prior to the final separation of the propeller.
Records indicated that this was not an isolated incident for this specific aircraft type. The investigation noted two previous propeller attachment failures involving similar engines: one on aircraft G-EVEY in October 2009 and another on G-CBWJ in August 2010. Both prior incidents were attributed to fatigue failures of the mounting screws.
Findings
- The propeller and hub assembly separated from the engine due to the failure of the screws attaching the propeller flange to the crankshaft.
- All screws responsible for securing the flange to the crankshaft had failed.
- Evidence indicated that some screws had undergone fatigue fracturing well before the actual detachment occurred.
- This incident follows a pattern of similar fatigue-related failures on other Thruster T600 aircraft using Jabiru 2200A engines.