Accident Overview
The airplane impacted a sign located on the Interstate's divider during a forced landing following a loss of engine power while in cruise flight. The pilot had initially reserved a Cessna 172 equipped with 50-gallon fuel tanks and planned the trip with that airplane in mind. His passenger called to ask if his friend could accompany them. The pilot stated that he would have to get back with him after checking the weight and balance. He reworked his weight and balance calculations and determined that they would be 66 pounds over gross with full fuel, golf clubs, and an additional person.
Preflight and Fuel Planning
The pilot went to the airport to check on the airplane and see how much fuel was on board. Upon arrival, he saw that the accident airplane, which had 40-gallon fuel tanks, had just returned from a flight. He talked to the pilot about how the airplane handled and what the fuel level was. The pilot who had just returned stated that it was running fine and he had flown about 1 hour 50 minutes. The pilot recalculated the weight and balance and found that the accident airplane would be within limits with his two passengers and their baggage. He estimated his trip time would be 3 hours with a fuel burn of 6 gallons per hour. The pilot subtracted the 2 hours of flight time from the previous flight, in addition to his own 3-hour trip time, and calculated he would have 1.6 hours of reserve fuel on board at the completion of his trip. He determined that this would be plenty of fuel.
Departure and Flight
Prior to takeoff, the pilot conducted a preflight inspection, which included visually checking the fuel level. The aircraft arrived at the destination after a 1-hour 15-minute flight, and the pilot did not have the airplane refueled. The next day, when they returned to the airport for the return flight, the pilot did not visually inspect the fuel tanks and departed. One hour and 12 minutes later, the engine lost power, and the pilot landed on an interstate highway.
Post-Accident Findings
Post-accident inspection of the airplane revealed that the fuel tanks were intact, but empty, with no other breaches or leakage in the fuel system lines found. Review of the Cessna 172N Pilot Operating Handbook revealed the fuel flow for 65 percent brake horsepower settings at the cruise altitudes would have been between 7.2 and 7.4 gallons per hour.