What happened
On the morning of August 7, 1984, a Cessna 402, registration 5Y-AMS, departed Mombasa on a scheduled flight plan involving stops at Ukunda, Amboseli, and Fig Tree Camp before returning to Mombasa. After an initial takeoff from Mombasa, the aircraft landed at Ukunda to pick up additional passengers, bringing the total number of occupants to eleven.
During the flight leg toward Amboseli, the pilot contacted Nairobi Centre at 0442 to report an estimated arrival time of 0ESS. However, the aircraft failed to arrive at its destination as planned. At 0601, the aircraft struck Marwa Hill near Sultan Hamud. The impact caused a post-crash fire in the port engine area that destroyed the aircraft. All eleven occupants were killed in the accident.
The investigation
The investigation examined the flight's progress, the pilot's credentials, the aircraft's maintenance history, and the meteorological conditions at the time of the accident. The aircraft was found to have been maintained according to an approved maintenance schedule, and the pilot was properly licensed and rated for the aircraft type.
Investigators analyzed the flight's tracking and communications. Evidence suggested that the aircraft had drifted approximately 8 degrees to the starboard of its intended track while flying above the cloud layer. This deviation went undetected by the crew. Consequently, after passing the estimated time of arrival for Amboseli, the pilot began circling the area to locate the destination. During these maneuvers, the pilot attempted to descend through gaps in the cloud cover and drizzle to identify landmarks.
Findings
- The weather conditions encountered along the flight route were significantly worse than the forecasts available to the pilot.
- Marginal Visual Flight Rules (VFR) conditions were prevalent across much of the route.
- The pilot was unable to maintain a known position due to the lack of visual references.
- The primary cause of the accident was the inability to maintain a known position and terrain awareness while attempting to navigate through low cloud and poor visibility.