Cessna 180 N1621C accident near Mitchell, Oregon

Probable cause

The pilot’s lack of understanding of the airplane’s fuel system, which resulted in a loss of engine power due to fuel exhaustion.

NTSB analysis

The single engine airplane experienced a loss of engine power during flight and the pilot performed a forced landing in rugged terrain. Examination of the airplane wreckage revealed minimal evidence of fuel. The airplane had a modified fuel tank system through a supplemental type certificate (STC). The STC changed the fuel capacity of the two fuel tanks from 30 gallons to 28.2 gallons each. The installation information for the STC noted that to determine the usable fuel for the airplane, the airplane’s type certificate data sheet (TCDS) should be referenced and the unusable fuel amount listed therein should be subtracted from the new total fuel capacity. The TCDS for the airplane stated that 5 gallons of fuel were unusable, which made the new total usable fuel capacity on the airplane 51.4 gallons. As a part of the STC, the airplane flight manual (AFM) and the fuel selector valve placard were to be updated with the revised usable fuel quantity. This action was noted on the FAA Form 337 for the STC installation. The pilot had purchased the airplane several years prior to the accident and the previous owner told him that all of the fuel (56.4 gallons) was usable. The pilot reported that there was no AFM supplement for the STC included in his paperwork, and that he did not ever look at the quantities indicated on the fuel selector valve placard in the cockpit due to its location between the seats. Examination of the recovered airframe and engine components revealed no evidence of preimpact mechanical malfunction.

Text from the NTSB. Open the NTSB docket for WPR10LA001 for the full record.