NTSB Factual Report

The pilot stated he was planning to conduct skydiving flights. The airplane owner assisted the pilot in fueling the airplane from a local fuel truck. The pilot used a ladder and started refueling the right wing with the owner manning the pump. While they were refueling the airplane, the owner asked the pilot if he was getting any fuel because the fuel meter was not running. They looked at the airplane's right main fuel tank and it appeared to be full. The pilot then climbed down and went to the left main fuel tank and added what he believed to be 10 gallons of fuel. The pilot thought he had 37.5 gallons of fuel on board when he departed.

The pilot flew four skydiving flights without refueling. On the last flight, after the skydivers left the airplane, he initiated a descent and the airplane experienced a total loss of engine power. The pilot knew he could not make it back to the airport and made a forced landing to a gravel area. The airplane collided with a gravel mound and nosed over inverted, causing structural damage to the airframe. The airplane had been operated for 1.9 hours since the fueling. Examination of the wreckage did not reveal any preimpact mechanical malfunctions, nor did the pilot report any. The examination also did not reveal any evidence of usable fuel.

Additionally, examination of the airplane rubberized bladder type fuel cells located on the inboard bay of each wing panel revealed the snap fasteners to prevent the collapse of the flexible cells were not installed and wrinkling of the bladder was noted. The fuel bladders were replaced about 5 years prior to the accident.

NTSB Probable Cause

A loss of engine power due to fuel exhaustion. Contributing to the accident was the improper installation of snap fasteners to the rubberized type fuel cells which resulted in wrinkling of the fuel bladders and incorrect fuel quantity for the flight.