Accident Overview
The airline transport pilot was conducting a cross-country aerial observation flight in a multiengine airplane. According to the pilot, while on the final leg of the traffic pattern, he reduced the power levers for landing and heard the right engine sound as if the propeller was moving toward the beta position. When he increased engine power, the sound ceased. However, as the airplane neared the runway and power was again reduced, the sound returned and the airplane began to yaw to the right.
Pilot Report
The pilot applied left aileron and rudder inputs to maintain alignment with the runway centerline, but was unsuccessful. Over the runway, he reduced the engine power to idle, and the yaw continued. He then applied full power in an attempt to perform a go-around, but the airplane yawed about 30 degrees off the centerline, touched down in the grass, and impacted trees before coming to rest.
Postaccident Examination
Examination revealed that the right wing, right engine, and right propeller assembly had been separated by impact. The right engine propeller was found about 50 feet forward of the main wreckage in the feathered position. Maintenance records showed that the right propeller had been overhauled and reinstalled two days before the accident, accumulating 9 flight hours since then. Testing of the right propeller governor showed it functioned without anomaly, but the speed settings were improperly configured. Additionally, the beta valve travel from the neutral position was out of tolerance. While this could have allowed oil pressure to port to one side of the spool and change blade angle, it could not be determined whether this occurred during the accident landing. Impact damage prevented examination of the propeller governor control linkage, leaving it unclear whether it was inadequately installed or rigged, which could have led to propeller movement into beta. The investigation was unable to determine why the right propeller moved toward beta as power was reduced, as reported by the pilot.