Background
The accident flight was the second of three scheduled flights for an aircraft tasked with providing proficiency and currency training for an FAA inspector. The flight instructor (CFI) and the FAA inspector conducted a preflight inspection and engine runup before taxiing to the sod runway (Runway 13) for departure.
Flight Sequence
During the takeoff roll, the FAA inspector noticed the engine was not developing full takeoff power and informed the CFI. According to the inspector, the CFI reached overhead to adjust the mixture control and instructed the inspector to continue the takeoff. As the airspeed approached 60 knots, the inspector was instructed to rotate the aircraft for liftoff.
A witness near the departure end of the runway observed the airplane become airborne and noted a reduction in engine RPM shortly after liftoff. Subsequently, the aircraft settled and collided with trees approximately 700 feet beyond the end of the runway.
Investigation
An examination of the aircraft and engine failed to reveal a mechanical problem. The wind at the time was reported from 290 degrees at 7 knots.