Page:CAB Accident Report, Mooney M-18 Crash on 7 September 1959.pdf/2

- 2 - one-half miles northwest of the airport he was observed executing "lazy-eight" maneuvers.

At approximately 1430, several persons on the ground saw the Mooney aircraft. They stated that it was proceeding in a southerly direction in straight and level flight. Several stated that they heard a loud sharp crack and saw objects separate from the aircraft. Several others heard the sound and then observed the aircraft in a spin with pieces falling behind it. Immediately thereafter the aircraft crashed one and one-half miles west of the Culmerville Airport. There was no fire.

Several aircraft parts were found back along the flightpath and confirmed the observations that inflight structural failure had occurred. The right side of the horizontal stabilizer was found 2,600 feet northwest of the main wreckage sits; the right elevator was found 1,100 feet northwest; and the fin and rudder, plexiglass, and a piece of right wing plywood were found 550 feet northwest of the wreckage.

The main portion of the aircraft struck the ground in a near-vertical descent. Impact damage indicated it was pitched nose down to a 30- or 40-degree angle and yawed to the left. All components, other than those which separated in flight, were found within a 25-foot radius of the powerplant.

The right wing spar had failed downward from inflight overloads at two points; approximately one foot outboard of the attache point and four feet, nine inches outboard of the attach point. The section between the two breaks was in the main wreckage with the landing gear still attached. The right flap with its hinges had separated from the wing and was bent upward in a "U" shape which corresponded closely with the curvature of the top of the fuselage midsection. The hinge welds on the flap were cracked at impact. One piece of plywood, identified as a portion of the right wing lower surface at and forward of the spar just outboard of the inboard failure, was found 550 feet form the wreckage. The size of this piece, which was originally glued to the spar, was 10.3 inches long but showed bonding of the glued joint for only about 3.5 inches.

Inspection of the right horizontal stabilizer, which separated in flight, revealed that the spar had failed at the right attach bolt in downward overload. A section of the right trailing edge member extending from a point outboard of the inboard hinge to the No. 3 rib had pulled out. It remained attached to the elevator by the middle hinge when the elevator had separated from the stabilizer. The outboard elevator hinge remained with the stabilizer. The glued joint of the No. 2 rib and the trailing edge member had separated with only slight failure of the wood. The lazinsted plies of the middle hinge block were also separated with no wood failure. The rearmost lamination was cracked rearward by the hinge bolt. In addition, the No. 1 rib had separated from the spar with very little wood failure.

The right elevator was found 1,100 feet northwest of the main wreckage area. It was bowed spanwise so that the middle hinge was about two inches lower than the rest and tip. The middle hinge was intact with the portion of trailing edge member mentioned above attached. The inboard and outboard hinges had separated at the upper and lower welds. These welds bad very little penetration.