On September 10, 1987, a Bell 47-G3B2 (registration N1038X) was involved in an aviation accident near Oakley, UT. Investigators recorded the probable cause as: The pilot's failure to maintain adequate airspeed and altitude in a high-density-altitude environment while operating in a confined area surrounded by obstacles, which resulted in a hard landing and substantial damage to the helicopter. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter pilot experienced a loss of engine power during takeoff from a confined area surrounded by power lines. Unable to gain altitude, the pilot attempted to maneuver around the wires but was forced into a hard landing that caused substantial damage to the aircraft.
What happened
The pilot had just taken off from a confined area that was surrounded on two sides by electrical power lines. As he attempted to climb after departure, he reported that his engine revolutions per minute (RPM) began to decrease significantly. In an effort to avoid the nearby wires, the pilot executed a right pedal turn. However, he was unable to prevent a hard landing, which resulted in substantial damage to the helicopter.
The investigation
The investigation noted that the density altitude at the time of the accident was 11,677 feet. This high density altitude condition likely contributed to the aircraft's performance limitations during the critical takeoff phase.
Probable cause
The pilot's failure to maintain adequate airspeed and altitude in a high-density-altitude environment while operating in a confined area surrounded by obstacles, which resulted in a hard landing and substantial damage to the helicopter.