Accident Overview
A Cessna 172G aircraft experienced a loss of engine power during cruise flight, necessitating a forced landing in a grass field. During the landing, the airplane's tail section impacted a fencepost and barbed-wire fencing.
Pilot's Report
The pilot reported that prior to departure, the aircraft had 34 gallons of fuel (31 gallons usable). After the accident, the pilot visually confirmed that both fuel tanks were empty. The elapsed time between the first ATC communication and the pilot's report of engine power loss was 3 hours and 57 minutes.
Fuel Consumption Data
According to the Cessna 172G owner's manual, the published fuel consumption rate at 7,500 feet MSL and 70% brake horsepower (bhp) is 7.8 gallons per hour. The pilot stated that his preflight planning assumed a fuel consumption rate of 6.1 gallons per hour, based on 7,000 feet MSL and 2,300 engine rpm (52% bhp).
Fuel Gauge Anomaly
The pilot informed a Federal Aviation Administration (FAA) inspector that the fuel quantity gauges had become "erratic" during the accident flight, and that he considered them "unreliable."