What happened
On 15 April 2003, a Cessna 172M, registration ZS-MSS, departed from Wonderboom Aerodrome (FAWB) as part of a scheduled training flight. The aircraft was operated by a commercial pilot accompanied by a student pilot, intending to fly to the Pretoria General Flying Area #1.
During the initial climb and subsequent turn onto the cross leg, the aircraft's engine began to lose power. This sudden loss of thrust necessitated an immediate forced landing in a field located north of the aerodrome. Despite the emergency nature of the descent, there were no injuries to the occupants, and no damage was sustained by the aircraft or any surrounding property. Weather conditions at the time of the incident were reported as fine.
The investigation
The investigation focused on the mechanical state of the engine and the maintenance history of the aircraft. While the pilot held a valid commercial license and was properly rated for the type, investigators noted that the aircraft had exceeded its maintenance interval, having flown 81 hours since its last periodic inspection (MPI).
Findings
Technical examination of the engine revealed that the throttle linkage had become dislodged from the carburettor. This failure was directly attributed to the linkage not being properly secured during a previous maintenance session.