WPR12LA356

The pilot stated that shortly after taking off for the aerial application flight the engine began to run rough. Because he could not maintain altitude and was concerned about clearing a set of power lines in front of him, the pilot partially dumped the airplane’s aerial application load. After the airplane cleared the power lines, the pilot attempted to land on a road; however, during the touchdown the airplane veered off of the road and into a ditch. A postaccident fire consumed the airplane. A postaccident examination of the engine revealed that the No. 2 cylinder exhaust rocker boss housing had separated from the cylinder, which prevented the cylinder's exhaust valve from opening and resulted in the loss of engine power. Maintenance records revealed that the cylinder had been inspected in accordance with the time interval specified by the applicable Federal Aviation Administration airworthiness directive (AD). The AD specifies a 100-hour recurring inspection requirement; the engine had accumulated 91 hours since its last inspection.

On August 14, 2012, about 0620 Pacific daylight time, a Rockwell International S-2R, N8468V, was substantially damaged during a forced landing following a loss of engine power after takeoff near Royal City, Washington. The certified commercial pilot received minor injuries. The airplane was registered to Royal Flying Service, Inc., and operated under the provisions of 14 Code of Federal Regulations Part 137. Visual meteorological conditions prevailed at the time of the accident and no flight plan was filed. The local flight originated from a private airstrip about 1 minute prior to the accident. In a statement provided to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the pilot reported that just after taking off with 325 gallons of liquid fungicide, he detected a rough running engine. The pilot stated that not being able to maintain altitude and in order to clear a set of wires in front of him, he partially dumped the load, cleared the wires, and then attempted to land on a paved road. After touching down, the airplane veered off of the road and into a ditch, where it caught fire and was consumed. A Federal Aviation Administration (FAA) airworthiness aviation safety inspector performed an onsite inspection of the accident airplane. The inspector reported to the IIC that his inspection revealed that the number 2 cylinder exhaust rocker boss housing had separated from the cylinder, which prevented the exhaust valve on the cylinder from opening, creating the loss of engine power. No other evidence of engine damage or malfunction was noted. The FAA inspector's review of company maintenance records indicated that all required inspections had been complied with, including FAA Airworthiness Directive (AD) 99-11-02, which addresses inspection requirements for the accident airplane's cylinder type. The AD specifies a 100-hour recurring inspection requirement; the engine had accumulated 91 hours since its last inspection.