Grumman G-164A N7395 accident near Pelham, Georgia

Probable cause

A partial loss of engine power for undetermined reasons which led to a forced landing in unsuitable terrain.

NTSB analysis

Approximately 2 weeks before the accident, significant unplanned maintenance was performed on the radial engine of the aerial application airplane. The activity included the removal of seven of the nine cylinders to remove fragments of piston rings, a piston skirt, and a broken governor drive gear from the engine case. Six of the removed cylinders were re-installed, and one cylinder was replaced with an overhauled cylinder and a new piston. The airplane was test flown, returned to service, and utilized for several days. On the day of the accident, one witness said that the engine was making "popping" noises before it crashed. The airplane touched down in a small clearing, but nosed over and collided with shrubs and trees. The accident site was located between the field being sprayed and the owner's airstrip. The pilot was fatally injured. Post-mortem toxicology revealed evidence of recent use of several over-the-counter, and one prescription, medications, but these medications are not typically associated with impairment. An autopsy revealed the presence of severe coronary artery disease and heart enlargement. The pilot’s physique and heart enlargement also strongly suggested that he may have suffered from obstructive sleep apnea, a condition associated with increased accident risk, but the circumstances of the accident were not consistent with impairment or incapacitation. Post accident examination of the engine revealed internal damage consistent with the engine being operated with one or more loose metallic items inside the engine case, but the damage could not be directly associated with the engine power loss. Several piston ring fragments were recovered from the engine case, but it could not be determined whether they were vestiges of previous problems, or were portions of the rings recently installed. No specific engine failure cause or mode was identified during the investigation.

Text from the NTSB. Open the NTSB docket for NYC08LA245 for the full record.