On September 16, 1992, a Bell 47-J2A (registration N291FW) operated by Ruggles, Don C. was involved in an aviation accident near Booneville, AR. Investigators recorded the probable cause as: THE PILOT'S FAILURE TO MAINTAIN ADEQUATE ROTOR RPM DURING AUTOROTATIVE LANDING. FACTORS WERE FUEL EXHAUSTION, THE PILOT'S IMPROPER FUEL CONSUMPTION CALCULATIONS, AND THE PILOT NOT REFUELING THE HELICOPTER. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During a power line observation flight, a helicopter experienced a power loss. The pilot initiated an autorotation but failed to maintain rotor RPM, causing the main rotor blades to sever the tailboom, resulting in a hard landing.
Accident Sequence
The pilot had flown the helicopter on a power line aerial observation flight for approximately 3 hours and 8 minutes when a power loss occurred. He initiated an autorotation to an open field. During the flare, he failed to maintain adequate rotor RPM, and the main rotor blades severed the tailboom. The helicopter subsequently landed hard.
Fuel Considerations
The owner of the helicopter drained a small amount of fuel from the tanks and stated that he was certain that lack of fuel caused the forced landing. The pilot reported performing a calculated fuel consumption check two days before the accident, which he indicated showed a fuel burn rate of 13.7 gallons per hour, or 3 hours and 47 minutes of flight time. He used a stopwatch in the cockpit to account for flight time.
Manufacturer Specifications
The manufacturer states that the fuel system holds 47.5 gallons of usable fuel, the engine's fuel burn rate is 19 gallons per hour at cruise, and lists the maximum cruise time as 3 hours and 18 minutes with the engine leaned.