Grumman American Avn. Corp. AA 1B N6550L accident near Hamilton, Ohio

Probable cause

The loss of engine power during takeoff for reasons that could not be determined because postaccident examination revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.

NTSB analysis

About 1 month before the accident, the prior owner of the accident airplane performed a maintenance test flight after an engine replacement. The airplane failed a run-up because of engine roughness. The mechanic/accident pilot who performed the engine replacement felt that the roughness was caused by oil getting by the new piston rings and fouling the spark plugs. The mechanic/pilot cleaned and reinstalled the plugs.

The maintenance test flight was then reattempted, and the prior owner flew in the right seat with the mechanic/pilot as the pilot flying. The prior owner indicated that the mechanic/pilot took the active runway without completing an engine run-up. The takeoff power appeared normal until about 100 ft above ground level, when the engine failed abruptly and without warning. The airplane's nose dropped, and the pilot landed the airplane, stopping it about 30 ft from the end of the runway.

The mechanic/pilot subsequently sent the carburetor out for overhaul. After reinstalling the carburetor, the mechanic/pilot attempted another maintenance test flight, which was the accident flight. Witnesses stated that the airplane took off; they heard the engine stop, and the pilot attempted to circle back to the airport but did not make it. The airplane impacted terrain during the landing, which resulted in substantial damage to the wing and fuselage.

The mechanic/pilot completed an accident report that did not contain a narrative of the accident flight and advised that he did not recall the accident. Further, the pilot did not indicate the date of his last flight review.

A postaccident engine examination revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation. The engine monitor sustained damage; no engine data was recorded for the accident flight.

At the time of the accident, the weather conditions were conducive to moderate carburetor icing at cruise power and serious carburetor icing at descent power. However, the engine was operating at takeoff power; the investigation was unable to determine if the pilot conducted any ground operations during which carburetor ice could have formed.

Thus, a reason for the loss of engine power could not be determined.

Text from the NTSB. Open the NTSB docket for CEN18LA173 for the full record.