On July 17, 1998, a Bell 47-GB31 (registration N92HA) was involved in an aviation accident near Olathe, CO. Investigators recorded the probable cause as: The pilot's failure to maintain adequate airspeed and power while flying in his own wake turbulence, which resulted in a loss of control due to settling with power. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter crashed during a third aerial application pass after entering its own wake turbulence. Insufficient power prevented recovery from settling, resulting in the main rotor severing the tail boom at high density altitude.
What happened
The aircraft was engaged in an aerial application operation when it entered its own wake turbulence during the third pass. The pilot attempted to dispense a rinse load but found that the helicopter had insufficient power to overcome the resulting settling motion. Consequently, the helicopter struck the ground in a nose-low attitude. Upon impact, the main rotor blades severed the tail boom.
Findings
The accident occurred under conditions where density altitude was computed to be approximately 8,900 feet. The primary factor contributing to the crash was the loss of control due to wake turbulence interaction and inadequate power margin to recover from settling with power.
Probable cause
The pilot's failure to maintain adequate airspeed and power while flying in his own wake turbulence, which resulted in a loss of control due to settling with power.
What happened in the 17 Jul 1998 Bell 47-GB31 accident near Olathe, CO?
A helicopter crashed during a third aerial application pass after entering its own wake turbulence. Insufficient power prevented recovery from settling, resulting in the main rotor severing the tail boom at high density altitude.
What aircraft was involved and where did it happen?
The accident on 17 Jul 1998 involved a Bell 47-GB31, registration N92HA, at Olathe, CO.
What was the probable cause of the accident?
The pilot's failure to maintain adequate airspeed and power while flying in his own wake turbulence, which resulted in a loss of control due to settling with power.
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