NTSB Factual Report

HISTORY OF FLIGHT

On March 30, 1997 at 1230 central standard time (cst), a Cessna 140, N77166, was destroyed following an uncontrolled descent into terrain, near Big Lake, Minnesota. Witnesses reported hearing a loud bang and seeing the airplane spinning before it impacted the terrain. The private pilot was fatally injured in the accident. The 14 CFR Part 91 flight was operating in visual meteorological conditions and no flight plan had been filed.

WRECKAGE AND IMPACT INFORMATION

The airplane wreckage was located in a wooded area. The wreckage path was consistent with a near vertical descent through the trees. Most of the aircraft's components were located within 20 feet of the main wreckage. Approximately one quarter mile from the main wreckage pieces of plexiglass which were from the airplane's windshield were found by local residents.

The right wing strut attachment was separated from the fuselage, and the right wing had wrapped around the aft fuselage of the airplane. Both right wing struts were buckled in numerous places. The brace strut for the right wing was not located. The location of the right wing's brace strut attachment to the spar had a portion of what appeared to be the strut attachment bracket, still attached. Both left wing struts had area's which were consistent with a buckling failure. The brace strut for the left wing was still attached to the main strut. Both wings of the airplane showed signs which appeared to indicate a negative G overload of the airplane.

The horizontal stabilizer was still attached to the airplane when the wreckage was found. The upper skin of the horizontal stabilizer was buckled. The spar of the horizontal stabilizer was buckled in compression on the lower surface at approximately the 10 percent span position, on both the left and right sides. The buckled spars appeared to indicate failure during a positive G loading of the airplane. No significant corrosion was found when the interior of the horizontal stabilizer, and the horizontal stabilizer's spar were inspected by the investigator in charge (IIC).

The vertical stabilizer was partially broken loose from its mount, but the vertical stabilizer was still attached to the fuselage.

Both elevators were attached to the horizontal stabilizer. Most of the rudder had separated from the vertical stabilizer. The left aileron was attached to the left wing. The right aileron was partially attached to the right wing. Both wing flaps appeared to be in a retracted position. No signs of any control surface flutter were noted by the IIC.

All flight control cables for the elevator, rudder and ailerons had continuity when checked by the IIC. No signs of any jammed control surface were found by the IIC.

The fuselage had numerous areas of skin buckling present. The cockpit area had sustained extensive crushing. Both plexiglass pieces which pass over the cabin area were shattered. The bulkhead that the wing strut attachment connects to showed many areas which appeared similar to an overload failure. The wing strut attachment bulkhead is located very close to the airplane's windshield.

The propeller signatures appeared to indicate a low power setting at the time of impact.

MEDICAL AND PATHOLOGICAL INFORMATION

An autopsy was performed by the Raminsey County Medical Examiner. Toxicological testing was performed by the Federal Aviation Administration in Oklahoma City Oklahoma. The toxicological testing was negative for all tests conducted.

TESTS AND RESEARCH

The engine was separated from the airframe on March 30, 1997. The gascalator screen, oil screen, and finger screen for the carburetor were all checked for contamination and were unremarkable. The carburetor was removed from the engine and when it was rotated, a sound similar to the float moving could be heard. All rocker covers were removed from the engine. The bottom spark plugs were also removed from the engine and were unremarkable. The engine was then rotated at the crankshaft to check for continuity and compression. All rocker arms moved and all cylinders had compression. The engine's number three cylinder's compression was very weak, until oil was poured into the cylinder through the spark plug hole. All of the ignition leads were cut, and both magnetos produced spark on all of the ignition leads.

ADDITIONAL DATA/INFORMATION

Two witnesses gave statement to the IIC. Both witnesses reported that they heard a loud bang, and then looked up to see an airplane spinning toward the ground. One witness reported that he was wearing ear muffs at the time, and even with the ear muffs on he heard the bang. One witness reported that the right wing was folded, during the descent to the ground, and that he heard many engine power changes before the accident. The other witness reported that he could see definite fuselage distortion, as the airplane was descending to the ground.

A review of the pilot's logbook indicated that eight days previous to the accident the pilot had flown a Waco airplane in Hawaii. The logbook entry for that flight indicated that the pilot had completed many different types of aerobatic maneuvers on that flight. The accident flight appeared to be the pilots first flight following the flight in Hawaii.

NTSB Probable Cause

The pilot's maneuvers which exceeded the design stress limits of the airplane and resulted in structural overload of the horizontal tail followed by a structural overload of the wings.