What happened
On 6 December 1994, a Piper PA31-350, registration 5Y-SMR, departed Wilson Airport in Nairobi, Kenya, en route to Kigali, Rwanda. The aircraft was operating as a public transport flight, carrying two passengers and cargo. Shortly after departure, the pilot contacted Nairobi Approach to report technical difficulties while passing 7,500 feet above sea level.
While the pilot was navigating toward the "Golf-Golf" (GG) NDB, the aircraft struck the Ngong Hills from a southerly direction. The impact sequence began when the aircraft hit vegetation, causing the loss of the left engine. The aircraft then struck a perimeter fence and a high-voltage transmission pylon, which severed electricity lines. The resulting contact with live power lines ignited a fire, and the aircraft subsequently rolled down the hillside. There were two fatalities among the crew and passengers.
The investigation
The investigation examined the flight's trajectory, the meteorological conditions, and the air traffic control (ATC) clearances provided. Investigators reviewed the pilot's experience, noting that while the pilot was properly licensed, he had limited hours on this specific aircraft type. The investigation also analyzed the weather at the time of the accident, which involved rain and very low cloud ceilings.
Furthermore, the investigators scrutinized the ATC instructions given by Nairobi Approach. The controller had cleared the aircraft to the "GG" NDB at flight level 100. Investigators looked into whether the altitude provided in the clearance was sufficient to clear the terrain of the Ngong Hills, which reach elevations of approximately 8,000 feet.
Findings
- The primary cause of the accident was terrain impact while the aircraft was maneuvering toward the "Golf-Golf" NDB.
- The subsequent fire was triggered by the aircraft striking high-voltage electricity power lines.
- The air traffic clearance provided to the aircraft failed to account for the high terrain along the prescribed flight path.
- Prevailing weather conditions, specifically low visibility due to rain, made it impossible to safely navigate the area unless flying above 9,100 feet ASL.
- The pilot possessed limited experience on the aircraft type, and the investigation noted that assigning such a flight in poor weather was not prudent.
- The aircraft had been properly maintained according to approved schedules.