What happened
On 23 April 1999, a Cessna 210L, registration ZS-MNN, was conducting a flight from Maun, Botswana, toward Gabarone, Botswana. The aircraft was carrying four occupants, including a pilot and a commercial pilot acting as a passenger.
During the initial phase of the flight, engine performance and all pre-flight indications remained normal. However, approximately 60 nautical miles from the VOR beacon, the crew heard an unusual noise coming from the engine, which was immediately followed by a loss of power. The crew observed that the oil pressure had dropped to zero, and the propeller pitch mechanism failed to respond to attempts to set it to full coarse.
Recognizing the emergency, the crew declared a "Mayday" to air traffic control and identified their position while preparing for an emergency descent. The pilot successfully executed a forced landing on a road located roughly 110 km north of Gabamente. While the initial touchdown on the roadway was successful, the aircraft encountered a curve in the road, causing the left wing to strike a small tree. This impact caused the aircraft to become uncontrollable before coming to a stop.
The investigation
SACAA AIID investigators examined the mechanical state of the engine and the circumstances of the landing. The investigation focused on the sudden loss of oil pressure and the failure of the propeller pitch control. The inquiry also reviewed the flight path and the impact with the tree during the landing sequence.
Findings
- The primary cause of the engine failure was the failure of the number one connecting rod.
- The mechanical failure led to a total loss of engine power and zero oil pressure.
- The aircraft's deviation and loss of control during the landing were caused by the left-hand wing striking a small tree following the initial touchdown.
- Despite the impact, all occupants were evacuated, though one passenger later sustained a fractured rib.