On July 6, 1985, a Bell 47G-3B-1 (registration N7856S) was involved in an aviation accident near Donaldson, MN. Investigators recorded the probable cause as: The pilot's failure to maintain adequate airspeed during the approach, which resulted in insufficient lift, compounded by the engine's inability to produce full power due to a frozen turbocharger wastegate actuating rod. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter sustained substantial damage after an engine failed to produce sufficient power during a go-around attempt, caused by a frozen wastegate actuator.
What happened
The pilot applied power in an effort to level off the aircraft while entering a spray pattern. During this maneuver, the engine did not produce sufficient power to arrest the descent. The pilot then attempted a run-on landing; however, uneven terrain resulted in substantial damage to the helicopter.
The investigation
A post-accident inspection of the engine revealed that the actuating rod for the actuator to the wastegate of the turbocharger was frozen to the housing of the unit. This mechanical failure prevented proper operation of the turbocharger system during the critical phase of flight.
Findings
The primary contributing factor was the frozen actuating rod of the turbocharger wastegate. This condition directly led to insufficient engine power, which prevented the pilot from arresting the descent and necessitated a run-on landing on uneven terrain.
Probable cause
The pilot's failure to maintain adequate airspeed during the approach, which resulted in insufficient lift, compounded by the engine's inability to produce full power due to a frozen turbocharger wastegate actuating rod.
Frequently asked questions
What happened in the 6 Jul 1985 Bell 47G-3B-1 accident near Donaldson, MN?
A helicopter sustained substantial damage after an engine failed to produce sufficient power during a go-around attempt, caused by a frozen wastegate actuator.
What aircraft was involved and where did it happen?
The accident on 6 Jul 1985 involved a Bell 47G-3B-1, registration N7856S, at Donaldson, MN.
What was the probable cause of the accident?
The pilot's failure to maintain adequate airspeed during the approach, which resulted in insufficient lift, compounded by the engine's inability to produce full power due to a frozen turbocharger wastegate actuating rod.
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