NTSB Identification: CHI90DCD02.
The docket is stored on NTSB microfiche number 42306.
Accident occurred Saturday, August 25, 1990 in WALL LAKE, IA
Probable Cause Approval Date: 12/14/1992
Aircraft: BELL 47G-2, registration: N90529
Injuries: 1 Uninjured.

AFTER REFUELING & RELOADING THE HELICOPTER WITH A SPRAY SOLUTION AT A FIELD SITE, A TAKEOFF WAS INITIATED IN CALM WIND CONDITIONS. THE PLT RPRTD THAT THE LOCATION REQUIRED HIM TO TAKE OFF UPSLOPE. HE STATED THAT THE RPM DROPPED SLIGHTLY, BUT REMAINED IN THE GREEN ARC DURING THE UPSLOPE PORTION OF THE TAKEOFF. AS THE HELICOPTER CROSSED A FENCE & THE TERRAIN STARTED SLOPING DOWNHILL, THE HELICOPTER FLEW OUT OF GROUND EFFECT. THE PLT RPRTD HE LEVELED THE HELICOPTER, THEN BEGAN A SLIGHT DSCNT TO INCREASE RPM & AIRSPEED. HOWEVER, THE ROTOR RPM DECAYED & JUST BEFORE TOUCHDOWN, THE HELICOPTER YAWED 90 DEG TO THE RIGHT. AFTER TOUCHDOWN, THE HELICOPTER ROLLED OVER. DENSITY ALT WAS ESTD TO BE 3216 FT.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

THE FAILURE OF THE PILOT TO MAINTAIN ROTOR RPM DURING TAKEOFF. THE HIGH DENSITY ALTITUDE AND UPHILL TERRAIN WERE FACTORS.

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