The commercial pilot was conducting an agricultural application flight in the Grumman G164. While maneuvering the airplane about 300′ above ground level, the engine experienced a partial loss of power.
Unable to maintain altitude, he pilot conducted an emergency landing to a field near Juliaetta, Idaho, during which the plane landed hard and nosed over, coming to rest inverted.
Post-accident examination of the engine revealed that the No. 2 cylinder head exhibited a circumferential crack of its barrel between the cooling fins.
The FAA had previously issued an airworthiness directive (AD) to address cylinder head cracking on the accident model engine. The AD required periodic visual inspections for cracks in the cylinder heads at specified intervals of time in service (every 100 hours for the Grumman).
According to the engine maintenance logbooks, the AD was last complied with about 35 hours before the accident. The previous inspections to this were sporadic, indicating that neither maintenance personnel nor the owner were regularly complying with the AD.
Probable cause: A partial loss of engine power due to a crack in the No. 2 cylinder.
NTSB Identification: WPR16LA082
This March 2016 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.