What happened
On March 8, 2011, a DeHavilland DHC-6-100, registration N157KM, was conducting a local maintenance test flight at Clayton County Airport (4A7) in Hampton, Georgia. The flight was intended to test the aircraft following the replacement of both Pratt & Whitney Canada PT6A-20 engines with higher-horsepower PT6A-27 models. The flight was conducted under Part 91 regulations, and no flight plan had been filed.
Witnesses observed the aircraft successfully complete two uneventful touch-and-go landings. However, during a subsequent maneuver in the traffic pattern for runway 6, an observer noted the engine noise fluctuating between low and high levels and observed the aircraft struggling to maintain altitude and airspeed. Another witness reported seeing the aircraft yaw to the left with noises consistent with the propeller "Beta" range, followed by a rapid roll to the and a nose-down spin.
The aircraft impacted trees in a wooded marsh area approximately 0.8 miles before the runway threshold. The impact resulted in 2 fatal injuries for the pilot and the pilot-rated mechanic on board.