LAX99FA225 · Cessna 402A

The airplane collided with two school buses during a forced landing on a city street. During a straight-in approach for landing, the pilot lost all power on his left engine. After switching to the left auxiliary tank the engine did not restart. About a minute later all power was lost on the right engine. No attempt was made to switch to the right auxiliary tank because the pilot felt the airplane was too low and he concentrated on making a forced landing on a city street directly in front of the airplane. After touchdown, the airplane's wing tip main fuel tanks collided with the front ends of two approaching school buses. The two main fuel tanks were ruptured in the accident and found empty. Only residual fuel was found in the lines, with 1 quart of fuel recovered from the left auxiliary tank and 4 gallons from the right auxiliary tank. Investigators could not determine the exact fuel load onboard before the first departure that morning; however, based on refueling records, the airplane would have had no less than 122 gallons. During the first leg of flight, a high cylinder head temperature reading led the pilot to make a precautionary landing at an airport just over halfway to the original destination; the total elapsed time at this landing was 1.3 hours. The pilot was then told to reposition the aircraft back to the point of departure. He said he relied on a preplanned flight plan provided by company dispatchers, and he did not recompute the fuel required for the return. No fuel was added before the return flight. The elapsed time on the return flight was 1.2 hours for a total of 2.5 hours. The pilot said that for both legs of the flight he set a fuel flow of 18 gallons per hour per engine (which is above the red line gage limit); the performance charts show that the proper fuel flow setting was 13.35 gallons per hour per engine. Even at the high fuel flow of 18 gph, investigators computed that the airplane should have had a minimum of 12 gallons at the time of the accident, and this fuel remains unaccounted for. The pilot said that at some point during the two legs he switched to his auxiliary tanks until the gauges read 2 and 5 gallons, and then switched back to his main tanks. He could not specifically recall how long he had been flying on the mains when he switched tanks, or on which leg the switch occurred. To avoid unwanted venting of fuel overboard, a specific fuel tank use sequence must be used. The engine driven fuel pumps supply 50 percent more fuel than is required to the metering valves for each engine, with the excess fuel returned to the corresponding main tank. The auxiliary tanks should not be selected until the main tanks have been used for at least 60 minutes so that the mains have room for the returned excess flow from the auxiliary tanks. No evidence of leakage or staining was found around the wing filler caps. Staining found on the pavement around both buses could not be differentiated between fuel and a fire suppressive agent. After the accident, both engines were started and test run with no anomalies noted.

Verbatim NTSB analysis and probable cause from the NTSB dataset