What happened
On 04 April 2005, at approximately 1330Z, a Macdonald Douglas 369E helicopter, registration ZS-RFJ, crashed into a residential home in the Lakefield area of Benoni. The aircraft, operated by the South African Police Services (SAPS) for crime prevention and patrol duties, was performing a routine flight following several previous sorties throughout the day.
While the aircraft was executing a left-hand turn at an altitude of roughly 800 feet, the engine experienced a sudden surge and a subsequent loss of power. The impact with the roof of the house was severe, destroying the aircraft and causing substantial damage to the building's structure and contents. The crash resulted in one fatality and two serious injuries among the three occupants on board.
The investigation
SACAA AIID investigators examined the wreckage and the engine components, including a metallurgical analysis conducted in both South Africa and the United States. The investigation focused on the engine's turbine assembly and the pilot's recent flight history.
Technical inspections of the engine revealed that an airfoil had fractured and separated from the second-stage turbine wheel. Metallurgical experts determined that the fracture was caused by high-cycle fatigue. Additionally, investigators noted that the diameter of the second-stage turbine wheel was below the minimum allowable specification, and evidence of rubbing was found on the tips of the turbine blades.
Findings
- The primary cause of the accident was a turbine blade failure that triggered an engine surge and a total loss of engine power.
- The loss of power caused the helicopter to enter a left-hand turn that the pilot was unable to recover from.
- A contributing factor was the pilot's limited experience on this specific aircraft type.
- The pilot's flying license was not valid at the time of the accident because her medical certificate had not been submitted to the SACAA.
- The operator's management of personnel training records was found to be inadequate.
- The investigation noted that the pilot's understanding of flight procedures over built-up residential areas was insufficient.