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The pilot was making a night visual approach to the end of a strip which was to serve as a helipad. The pad was illuminated by the headlights of a vehicle while lights from a house and shed provided additional peripheral light sources. The pilot reported that there was considerable turbulence adjacent to high ground near the strip. The approach was being flown at an indicated airspeed of 50 knots. While passing over the high ground at a height of about 400 feet, the airspeed suddenly reduced to virtually zero and a large sink rate developed. The pilot attempted to go-around but the helicopter continued to descend until it struck the ground in a near vertical descent. The terrain and wind velocity were such that windshear over the high ground was probable. However, it was considered unlikely that this alone would have resulted in such a severe loss of airspeed. It was possible that the pilot, who had limited night flying experience, had not noticed a decay in airspeed prior to the sudden descent. If this was the case, the conditions were suitable for the aircraft to enter a vortex ring state. The fact that when the pilot increased power and collective the descent continued would also support this conclusion.

Download Final Report
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General details
Date: 04 December 1988 Investigation status: Completed 
Time: 2235 Investigation type: Occurrence Investigation 
Location   (show map):Innamincka Homestead  
State: South Australia Occurrence class: Operational 
Release date: 06 May 1989 Occurrence category: Accident 
Report status: Final Highest injury level: Minor 
 
Aircraft details
Aircraft manufacturer: Bell Helicopter Co 
Aircraft model: 206 
Aircraft registration: VH-CIH 
Serial number: 3031 
Type of operation: Aerial Work 
Sector: Helicopter 
Damage to aircraft: Substantial 
Departure point:Moomba SA
Departure time:2158
Destination:Innamincka Homestead SA
 
 
 
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