Grumman G164 N8741H accident near Riverdale, California

Probable cause

The partial loss of engine power due to the failure of the engine's supercharger-blower.

NTSB analysis

During a spray pass the pilot detected a "hot smell," which prompted him to pull up out of the field to check his engine gauges. As everything appeared normal the pilot returned to the field to continue spraying operations. Upon re-entering the field the pilot reported that "…the engine changed sound." After pulling up out of the field a second time the pilot revealed that the engine began to slow down, followed by the emission of smoke from the exhaust system. The pilot made a successful forced landing in the field he was spraying; however, due to the wet field conditions it nosed over on its back, which resulted in substantial damage to the airplane. A post accident teardown examination revealed that the engine had failed as a result of a supercharger-blower failure. It also revealed that foreign object material was detected in the engine; however, it could not be determined if this was causal to the engine failure. The manufacturer recommends an overhaul time of between 600 to 1,000 hours for engines operated in aerial application operations. At the time of the accident the engine had accumulated a total of 835.27 hours since its most recent major overhaul.

Text from the NTSB. Open the NTSB docket for WPR09LA373 for the full record.