Accident Overview
The airplane was substantially damaged during a gear-up forced landing after takeoff. The pilot reported that the preflight and engine run-up were normal. After being cleared for takeoff, he advanced the throttle to 1,270 pounds of torque before releasing the brakes, and everything was normal. Upon reaching 85 knots, he rotated, achieved a positive rate of climb, and retracted the landing gear. Just after the wheels were up, the engine shuddered with a very substantial loss of power, described by the pilot as "like a car that was hitting on half its cylinders." The pilot brought the power back to idle and focused on returning to the runway. After touching down, he pulled the emergency fuel cutoff. The airplane traveled straight ahead, crossed a taxiway, and came to rest about 100 yards past the taxiway. The pilot then shut off the battery and exited via the rear door.
Aircraft and Engine Information
The airplane had a total of 183 hours since new. The pilot reported having a propeller overspeed warning during the flight previous to the accident flight. The tach generator was replaced after that incident. The removed tach generator was tested and no discrepancies were found.
Investigation Findings
A tear-down inspection on the engine failed to reveal any malfunctions or failures that would have resulted in the loss of power. Both the primary and overspeed propeller governors were removed from the engine and tested. Visual inspection of the primary governor revealed lockwire on the airbleed system reset-eccentric screw was non-standard for Woodward, and the torque sealant had been removed. Visual inspection of the overspeed governor revealed the inside of the speed setting hex screw did not contain any torque sealant, and the sealant on the outside threads of the screw was cracked near the base of the screw and the housing.
Bench testing of both governors revealed the overspeed governor was set to a lower RPM than the primary governor. Therefore, the overspeed governor would have been controlling the system. Manufacturing flight test documents indicate four occasions when the maximum reverse RPM was adjusted. Flight tests conducted with the governors calibrated to the settings at the time of the accident were performed, and data from those tests indicate the propeller RPM was limited between 96-97% and that changes in RPM stabilized within seconds.