What happened
The aircraft was operating as the third flight of the day when the pilot completed a service order for 32 gallons of fuel. Instead of refueling the aircraft, the pilot placed the service order on a bench just inside the open hangar doors. The order was later discovered on the hangar floor, indicating the plane had not been refueled.
While flying over the Grand Canyon at an altitude of 7,500 feet, the left engine quit. The pilot reported that the fuel quantity gauges indicated empty. He attempted to head for the canyon rim and cleared it by approximately 500 feet above ground level. After advising his company of his intent to either make the airport or land in a clearing, the right engine also quit.
The aircraft made a forced landing, which resulted in the collapse of the landing gear.
The investigation
Post-accident examination revealed that the right main, left main, and left auxiliary tanks were empty. The right auxiliary tank contained only 5 gallons of fuel.
Findings
The pilot failed to refuel the aircraft during a service stop, leading to fuel exhaustion. This resulted in the loss of power from both engines and a subsequent forced landing.