What happened
On Tuesday, August 3, 1999, at 13:55, a Robin DR 400-180 R, registration F-GAHH, was engaged in a glider towing operation near the Bailleau airfield in Loinville, France. While flying at an altitude of approximately 200 meters, the pilot of the towing aircraft experienced a violent impact at the front of the engine, followed immediately by intense vibrations. Within seconds, the engine ceased functioning.
In response to the sudden loss of power and the severe vibrations, the glider pilot successfully released the towline. The pilot of the towing aircraft subsequently performed an emergency landing in a nearby field. The aircraft sustained heavy damage during the event.
The investigation
The investigation focused on the failure of the Sensenich model 76 EM 8 S 5 two-blade metal propeller. Examination of the propeller revealed that one blade had fractured at a distance of 370 mm from the hub. Investigators identified a 2.5 mm deep indentation on the trailing edge of the blade, which served as the initiation point for the fracture.
Further inspection of the area surrounding this indentation revealed scratches consistent with the use of a file. This indicated that an attempt had been made to smooth or repair the damage manually.