Grumman Acft Eng Cor-Schweizer G 164A N8598H accident near Five Points, California

Probable cause

Maintenance personnel’s improper reassembly of the engine during overhaul, which led to the failure of the supercharger-blower due to a lack of lubrication and the subsequent total loss of engine power during takeoff.

NTSB analysis

The pilot reported that, shortly after takeoff for the aerial application flight, the engine lost power. The pilot subsequently initiated a forced landing to a field. The airplane impacted the ground and flipped over.

The engine manufacturer's table of limits specified that the minimum side clearance/tolerance between a starter shaft circumference and a starter shaft bushing should be 0.002 inch. However, during postaccident examination, there was no measurable clearance between the starter shaft circumference and the starter shaft bushing, which impeded oil flow to the impeller shaft and bearings and resulted in the failure of the supercharger-blower due to a lack of lubrication. The engine had accumulated 2.0 hours since its last major overhaul, and it is likely that maintenance personnel improperly reassembled the engine during the overhaul.

Text from the NTSB. Open the NTSB docket for WPR15LA194 for the full record.