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
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.
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.