What happened
On 27 May 2009, a Cessna TU206F, registration ZS-MKG, was conducting a geographical survey flight over the Bethal and Kriel regions. The aircraft, operated by Fotogramensura (Pty) Ltd, departed from Wonderboom Aerodrome with a pilot and a camera operator on board. After approximately two hours of flight, the pilot requested descent to return to base, but suddenly observed a sharp drop in engine oil pressure.
Shortly after the pressure drop, the engine began running roughly, accompanied by loud thumping noises and smoke entering the cockpit. At an altitude of approximately 3,000 feet, the pilot elected to shut down the engine and declared a Mayday. While attempting a forced landing in a ploughed field, the aircraft struck a 40cm-high embankment at the edge of a mine service road. The impact caused the nose wheel to detach and the aircraft to bounce. Upon the second impact with the soft soil, the nose gear strut dug into the ground, causing the aircraft to nose over and come to rest in an inverted position.
Both occupants sustained minor injuries. The pilot suffered a head laceration, while the camera operator sustained a leg injury caused by a camera breaking loose from its floor mount during the impact.
The investigation
SACAA AIID investigators examined the wreckage and the engine, a Teledyne Continental TSIO-520-M. The teardown inspection revealed an uncontained engine failure. Specifically, investigators found a hole in the crankcase aligned with the No. 4 cylinder. The investigation also reviewed the aircraft's maintenance records, noting that the engine had been subject to a 50-hour inspection approximately 32 hours prior to the accident.
Findings
- The primary cause of the accident was an unsuccessful forced landing following an in-flight engine failure.
- The engine failure was driven by a mechanical breakdown involving the seizure of the big-end bearings on the No. 4 and No. 5 connecting rod hardware.
- The aircraft's impact sequence was exacerbated by the collision with an embankment, which led to the loss of the nose wheel and the subsequent inversion of the aircraft.
- The pilot's decision to attempt a landing in the identified field was deemed adequate, as the accident was primarily caused by the unexpected obstacle of the road embankment.