Executive summary
After leaving Milford Sound with a full load of passengers to fly to Queenstown, the engine of ZK-FTL had begun to run less smoothly than normal so the pilot returned to Milford Sound. Following discussion with engineering staff, and ground running checks, the pilot took off for a test circuit. In the circuit the engine again ran roughly, and on late downwind stopped completely. An area of dry riverbed provided the only option for a forced landing. The nosewheel was torn out and the propeller, lower forward airframe, and engine structure were damaged in the landing on the boulder strewn surface. A defective fuel control unit was the most likely source of the problems experienced.
Related Recommendations
Engineers be made aware of the accident circumstances to stress the desirability of identifying the cause of an apparent, recurrent, engine problem before authorising a test flight.
Pilots in command be advised of the need to consider full the consequences of a repetition of an engine fault before conducting a test flight following a reported engine malfunction.