What happened
On December 30, 1999, a Rockwell Intl S-2R, registered ZS-LOA, departed from Runway 24 at Parys Aerodrome. Shortly after lifting off and initiating a left turn, the pilot reported hearing an unusual winding sound, followed by engine backfires. Within seconds, the engine lost power completely.
In an attempt to manage the emergency, the pilot tried to land on the adjacent grass runway. During this maneuver, the right wingtip and the landing gear struck the ground. The aircraft subsequently entered a ground loop, coming to rest approximately 30 meters from the initial point of impact. There were no injuries to the pilot.
The investigation
SACAA AIID investigators examined the engine components to determine the source of the power loss. The investigation focused on the supercharger assembly to identify why the engine failed so abruptly after takeoff.
Findings
Technical analysis revealed that the supercharger impeller (Part No. 12788) failed, which led to a significant loss of engine power. The investigation established that the failure originated from the deformation of the carrier ring (Part No. 47033). This deformation created excessive play on the impeller shaft. Because the impeller rotates at seven times the engine's RPM, this instability caused the impeller to make contact with the inlet casing. The resulting friction and metal shaving against the casing induced metal fatigue, eventually causing several impeller vanes to fail.