Cessna R182 N1835R accident near Worland, Wyoming

Probable cause

The pilot's decision to operate an airplane with unreliable fuel gauges and the worn fuel cap seal that allowed fuel to siphon from the left wing fuel tank, which ultimately resulted in a total loss of engine power due to fuel exhaustion.

NTSB analysis

The commercial pilot reported that, about halfway through the planned pipeline surveillance flight, the engine experienced a total loss of power and he performed a forced landing to a dirt road. A postaccident examination revealed that both fuel tanks appeared to be empty; the left wing fuel tank cap seal appeared to be worn, and the left wing exhibited fuel staining aft of the fuel cap, consistent with fuel siphoning from the tank in flight.

The airplane was fueled the preceding night, and the pilot had assumed the fuel tanks were full upon departing on the first flight of the day. The airplane was flown 2.7 hours on the morning of the accident before it was refueled. The pilot did not recall visually confirming the fuel level following that refueling. An additional 4.1 hours of flight time elapsed from the time the airplane was refueled until the accident. According to the pilot, the airplane's fuel gauges were unreliable. To compensate, he had adopted the practice of completely filling the fuel tanks during each refueling, tracking the intervening flight time, and calculating fuel burn based on the airplane's average fuel consumption rate. Two days before the accident, an individual refueling the airplane informed him that the left fuel cap seal was torn. A new fuel cap seal had not yet been installed.

Although the amount of fuel lost through the cap could not be quantified, the unreliable fuel gauges did not allow the pilot to monitor either the normal fuel consumption nor alert him to the potentially abnormal rate of consumption due to the siphoning fuel. In addition, the pilot failed to verify the amount of fuel onboard before departure, which further rendered his method of tracking fuel consumption inaccurate.

Text from the NTSB. Open the NTSB docket for CEN17LA356 for the full record.