Accident Overview
On July 31, 2018, at about 2300 Alaska daylight time, a Cessna 185 airplane, registration N185KB, sustained substantial damage in an accident near White Mountain, Alaska. The private pilot and three passengers were uninjured. The flight was operated as a personal flight under Title 14 Code of Federal Regulations Part 91.
Flight and Maneuver
The pilot reported that earlier that day, he had fueled the airplane with 55 gallons, resulting in 84 gallons of usable fuel for the 120-mile round trip. The flight to the destination was uneventful. On the return flight that evening, the pilot proceeded toward the coast to avoid rising inland terrain and low clouds. The pilot-rated passenger in the front seat reported that, while maneuvering toward the coast, the pilot performed an "up down" maneuver for his sons in the rear seats. The pilot accelerated the airplane and gently pulled and pushed the nose over so that the occupants could experience momentary weightlessness.
Engine Power Loss and Forced Landing
About 45 seconds to 1 minute after the maneuver, the pilot noticed that the propeller rpm had reduced from 2300 to 1920 rpm. He advanced the propeller control lever forward with no response. He then pushed the throttle and mixture controls full forward, also with no response. Activating the auxiliary fuel pump switch did not restore full engine power. The pilot subsequently performed a forced landing to terrain. The passenger stated that the landing appeared normal, but during the landing roll, the airplane nosed over onto its back. The left wing, both lift struts, vertical stabilizer and rudder, and fuselage sustained substantial damage.
Post-Accident
The occupants egressed from the airplane, and the pilot called a family member. However, diminishing visibility prevented rescue that night. The occupants sheltered inside the airplane with one sleeping bag and some survival equipment and were rescued the following morning. The pilot and passenger each stated that they regretted not having more sleeping bags, rain gear, and a hand-held aviation VHF radio on board.
Examination Findings
Examination of the airframe and engine revealed no anomalies with the exception of one exhaust valve, which exhibited green crescent signatures consistent with exposure to excessively high temperatures. There was no sign of valve failure, such as fractures or restricted movement of the valve. All fuel samples were clear, and fuel was present in the fuel lines to the engine.