On April 5, 1999, a Bell 206L-1 (registration N255AL) was involved in an aviation accident near Shawnee, OK. Investigators recorded the probable cause as: The improper flare during an autorotation by the pilot-in-command. A factor was the loss of engine power for an undetermined reason. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter sustained a severed tailboom after the main rotor blades struck it during a hard landing. The incident followed an unexplained loss of engine power while the aircraft was at 400 feet AGL.
Incident Overview
The main rotor blades of a helicopter struck and severed the tailboom during a hard landing. The hard landing occurred after the helicopter experienced a loss of engine power. The aircraft had departed from an airport and climbed to approximately 400 feet above ground level. The pilot then turned the helicopter downwind and leveled the aircraft. After setting 'cruise power,' the engine 'spooled down.' The pilot performed an autorotation to a muddy, grassy field and landed hard.
Engine Examination
Following the incident, the engine was test run. The test revealed that the fuel scheduling was incorrect, as the turbine outlet temperature would exceed the maximum allowed. After replacing the fuel control unit, the engine was 'found to meet new engine performance at all guarantee test points.' The fuel control unit that was removed was functionally tested and operated within service limits.
Cause Determination
The reason for the loss of engine power could not be determined.