Grumman G-164A N8923H accident near Hopewell Township, New Jersey

Probable cause

A partial loss of engine power while maneuvering at low altitude due to a failure of the airplane’s supercharger.

NTSB analysis

The pilot was performing an aerial application flight over a nursery. As he pulled up at the end of a pass, he crossed over an area of trees and heard a “loud bang.” He attempted to maneuver the airplane to land in an open field; however, the airplane “ran out of altitude and airspeed” and impacted the ground, which resulted in substantial damage to the fuselage and wings.

Postaccident examination of the airplane’s vintage radial engine revealed that when rotating the propeller, the drivetrain would rotate freely, and no binding was noted. All the engine cylinders were intact. The supercharger impeller was intact, but further examination revealed that it was not rotating when the propeller was moved by hand. The rear accessory/diffuser housing was removed to expose the supercharger impeller and no damage was noted on the external impeller blades; however, the rear splined impeller shaft ball bearing spacer and supercharger impeller splines were found to have sheared, allowing the impeller to freewheel. Based on this information, it is likely that the failure of the supercharger resulted in at least a partial loss of engine power, and that the failure occurred while the pilot was performing a low altitude maneuver. The pilot was subsequently unable to recover from the resulting loss of airspeed before the airplane impacted the ground.

Text from the NTSB. Open the NTSB docket for ERA22LA297 for the full record.