What happened
On the morning of 29 January 2017, a Falcon 402 with registration ZU-SWL departed from Runway 11 at Wonderboom Aerodrome (FAWB) for a positioning flight to Rustenburg. The flight was intended to move the aircraft to its home base following a 50-hour maintenance inspection.
Shortly after the aircraft became airborne, the pilot retracted the landing gear and adjusted the propeller pitch lever to the climb RPM setting. At this moment, the engine power began to decay, and the Gemini Engine Parameter Display Screen transitioned from green to red, signaling a potential exceedance of engine parameters. The pilot experienced a physical drop in power as the N1 turbine speed fell to approximately 70%.
In response to the power loss, the pilot declared a Mayday and elected to perform a forced landing on the grass clearway ahead on the extended centerline of the runway. During the descent, the pilot attempted to lower the landing gear; however, the gear failed to lock into position. Upon touchdown, the landing gear collapsed, causing the aircraft to come to rest on its lower fuselage. While the pilot escaped without injury, the aircraft sustained substantial damage.
The investigation
The investigation examined the sequence of events following the engine power decay and the subsequent landing. Investigators noted that the aircraft, a non-type certified amateur-built design, was powered by a Walter M601 turboprop engine. The investigation confirmed that the pilot was a commercial pilot with the appropriate type rating, though this was his first flight on this specific aircraft type since a previous accident involving a similar aircraft in December 2016.
While the pilot had activated the fuel boost pumps immediately following the power loss, the exact cause of the engine's power decay could not be definitively determined, partly because the substantial damage to the aircraft prevented a functional engine test run. The investigation also confirmed that weather conditions were clear and did not contribute to the incident.
Findings
- The primary cause of the accident was an unsuccessful forced landing resulting from a loss of engine power.
- The engine parameter display indicated a possible exceedance of operating parameters, which coincided with the pilot's observation of decaying engine power.
- The landing gear was not fully extended and locked at the time of impact, leading to the collapse of the gear and subsequent fuselage damage.
- The pilot's previous involvement in an accident with a similar aircraft type shortly before this flight was noted as a contributing factor.