Primary finding
Probable cause
A partial loss of engine power for reasons that could not be determined because postaccident examination did not reveal any anomalies that would have precluded normal operation.
Investigator assessment
Analysis narrative
The private pilot reported that, after a preflight inspection and engine run-up revealed no anomalies, he and a passenger departed, circled a nearby mountain, then descended to an altitude about 750 ft above ground level. Shortly thereafter, the engine experienced a partial loss of power. The pilot attempted to restore engine power, but was unsuccessful, and he elected to land the airplane on a dry wash. As the airplane touched down, the right main landing gear sank into the dirt, and the airplane made a sharp turn to the right. The airplane impacted a tree and came to rest nose down. The atmospheric conditions at the time of the accident were not conducive to the formation of carburetor icing. A postaccident engine examination and test run revealed no anomalies that would have precluded normal operation; therefore, the reason for the loss of partial engine power could not be determined.
Source record
Factual narrative
On March 2, 2016, about 1600 mountain standard time, a Piper PA-22-150 airplane, N4356A, executed a precautionary landing onto a sandy wash following a partial loss of engine power near Fountain Hills, Arizona. The private pilot and passenger were not injured; and the airplane sustained substantial damage to the wings. The airplane was registered to, and operated by, a private party as a 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. The local flight originated from Phoenix-Mesa Gateway Airport (IWA), Phoenix, Arizona at about 1540. The pilot reported that after a normal preflight and run-up, he took off and circled a nearby mountain before descending to about 750 feet above the ground at a 2,400 RPM. As they followed a nearby river, the engine started to sputter and decrease to about 900 RPM; the pilot increased and decreased the throttle several times, but the engine never went above 1,200 RPM before it decreased again. He observed that the oil pressure was low; therefore, he attempted to switch fuel tanks, turned on carb heat, ensured the mixture was full rich, but the engine never responded. The pilot elected to land the airplane onto a dry wash. When the airplane touched down, the right main landing gear sunk into the dirt and the airplane made a sharp turn to the right. The airplane rolled along the dirt, impacted a tree, and came to rest nose down. During a postaccident examination by a Federal Aviation Administration Inspector, the engine cowling was removed and no visual anomalies were noted with the engine. The propeller and spinner were removed; and a test run propeller and temporary fuel tank were installed. The engine was started and operated normally; slowly, the power was increased to 2,400 RPM and the oil pressure was normal. After operating for a short time, the power was decreased and the engine was shutdown. There were no anomalies noted that would have precluded normal operation.