Witness Observations
Witnesses reported that the airplane had been refueled prior to departing on an instructional flight. Shortly after departure, during the initial climb, a witness observed the airplane in a steep turn, followed by the nose dropping, and the airplane entering a spin before impact. A flight instructor familiar with the accident airplane type also saw it prior to impact and stated that he thought the wing flaps were extended approximately 20 to 30 degrees.
Wreckage Examination
During the wreckage examination, the wing flap indicator was found damaged and read about 28 degrees down. The flap actuator jackscrew measurement equated to flaps extended about 30 degrees. A separate electrical supply was connected to the flap motor, bypassing the internal electrical circuits, and the motor was energized. The jackscrew successfully raised and lowered the flaps.
The fuse for the electric flap motor was removed from the instrument panel. Beneath the fuse holder, the instrument panel was marked: "FLAPS SLO-BLO." The fuse had the markings: "BUSS AGS 10" on the side. Examination of the fuse revealed that it was blown (nonfunctional).
Operational Considerations
The operator's manual states: "Note: A special 'SLO-BLO' fuse protects the wing flaps circuit. If this fuse is replaced, care should be taken to assure that the replacement fuse is of the proper type and capacity. A 'SLO-BLO' fuse is identified by an integrally mounted spring encircling the fuse element." Additionally, the manual calls for a SLO-BLO fuse rated for 15 amps. On flap operation, the manual notes: "Flap deflections of 30 and 40 degrees are not recommended at any time for take-off."
An examination of the engine did not reveal any preimpact mechanical anomalies that would have prevented normal operation. The gross weight of the airplane was estimated to be approximately 1,770 pounds, or about 170 pounds over the allowable gross weight.