Accident Overview
On April 29, 2017, at approximately 1015 Pacific daylight time, a Yakovlev Yak 52 airplane, registration N132MD, experienced a total loss of engine power during a local personal flight. The pilot executed an off-airport forced landing in a field near Porterville, California, resulting in substantial damage to the aircraft. The airline transport pilot sustained minor injuries, while the one passenger was uninjured.
Flight Details
The flight originated from Porterville Municipal Airport (PTV) at 0935 under visual meteorological conditions. No flight plan was filed. The purpose of the flight was to practice a mass formation flight. The pilot separated from a larger formation of four aircraft to land, but shortly after separation, the engine began to run rough and intermittently. Unable to maintain level flight, the pilot detached from the four-airplane formation.
Pilot Actions
The pilot reported that 29 gallons of usable fuel remained at the time of the issue. He checked the magnetos, ignition switch, generator, and battery, all of which indicated normal operation. Despite these checks, engine power continued to diminish. At an altitude of about 500 feet above the ground, the pilot elected to land in a vineyard. During the landing, the airplane touched down, came to an abrupt stop, and nosed over, coming to rest inverted.
Postaccident Examination
A postaccident examination of the airframe and engine was conducted by a mechanic and a Federal Aviation Administration inspector. The spark plugs were removed and showed signatures consistent with normal wear and operation. The engine was rotated by hand, and thumb compression was established in all cylinders. The oil screen was removed and found clear of debris. The fuel tanks were empty, and the fuel system was continuous throughout. The fuel screen contained small pieces of unknown fabric, as well as a small amount of metal shavings from an unknown source and a small chunk of metal found in the fuel intake and inlet screen.
Carburetor Inspection
The carburetor was removed and examined. The throttle plate moved freely from stop to stop. The fuel metering section was heavily damaged and fracture separated; the needle valve moved freely. No signs of corrosion were present. The fuel inlet screen was clear of debris except for the small metal shavings and chunk of metal. The origin of the metal pieces was not determined.