Accident Overview
On August 4, 2015, about 0830 Pacific daylight time, a Grumman G-164B agricultural airplane, registration N48452, was substantially damaged during a forced landing due to a loss of engine power. The event occurred near Princeton, California. The airplane was operated by Valley Air Service, LTD. The commercial pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed for the local aerial application flight, which was conducted under 14 Code of Federal Regulations Part 137. No flight plan was filed. The flight had departed Colusa County Airport (O08) about 0800.
Pilot Report
In a telephone conversation with the National Transportation Safety Board investigator-in-charge, the pilot reported that the accident occurred on the second load of the morning while applying a fungicide to a rice field. During a spray run, the engine lost power. Unable to maintain altitude, the pilot executed a forced landing to the rice field he was treating. The airplane nosed over during the landing, resulting in substantial damage to the rudder and the right upper and lower wing panels.
Engine Examination
On August 18, under the supervision of a Federal Aviation Administration Aviation Safety Inspector, the engine was examined by a licensed FAA airframe and powerplant mechanic. The examination revealed that the number 2 cylinder head had cracked and lifted under the cooling fins on the left side of the cylinder. The crack continued across the top and inside of the head to the intake valve seat, which resulted in the loss of power after hot gases entered the induction system. No other anomalies with the engine or the airframe that would have precluded normal operation were found.
Maintenance Records
An examination of the airplane's maintenance records showed that the most recent annual inspection was performed on March 7, 2015. Records further indicated that on March 16, 2015, FAA Airworthiness Directive (AD) 99-11-02, a mandatory 100-hour repetitive visual inspection to prevent cylinder head cracking, was performed at an engine tachometer time of 3,661.4 hours. At the time of the accident, the engine tachometer read 3,728.1 hours, or 66.7 hours since the AD had been complied with.