Accident Bell 206B N36HF,
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ASN Wikibase Occurrence # 292621
 
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Date:Friday 17 February 2006
Time:09:50 LT
Type:Silhouette image of generic B06 model; specific model in this crash may look slightly different    
Bell 206B
Owner/operator:Helicopter Flite Services
Registration: N36HF
MSN: 1886
Year of manufacture:1975
Total airframe hrs:10800 hours
Engine model:Rolls-Royce 250C20
Fatalities:Fatalities: 0 / Occupants: 1
Aircraft damage: Substantial
Category:Accident
Location:Big Creek, Kentucky -   United States of America
Phase: Unknown
Nature:Ferry/positioning
Departure airport:Charleston-Yeager Airport, WV (CRW/KCRW)
Destination airport:MIDDLESBORO, KY (1A6)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The pilot of the helicopter was en route to pick up passengers, when approximately 16 miles prior to his intended destination, he landed in a field due to deteriorating weather conditions. During a cellular telephone conversation with his employer, it was decided that the pilot should reverse course, land at a nearby airport, or return to the helicopter's base. The pilot took off from the field and attempted to fly directly to an airport, but was again unable to follow his desired course due to weather. As he maneuvered, the weather improved, the ridgelines were visible, and the pilot was able to fly "about 100 feet above the trees, and 200 feet below the clouds" as he approached a field that was crossed by a power line. The pilot said he chose to land in the field because of a "klunking" noise behind him. "As I entered the approach the noise got worse and the aircraft started to vibrate. The vibrations got very bad as I tried to arrest my descent, so I decided that touching down hard was better than shaking apart." Examination of the global positioning system ground track revealed that the helicopter descended at a rate of 1,000 feet per minute during an s-turn across the face of a mountain before it leveled over flat terrain, and slowed below effective translational lift, in the vicinity of the crash site. The crash site was surrounded by rising terrain, in the lee of a mountain with strong winds, and an AIRMET for turbulence was in effect along the route of flight. The helicopter experienced a high sink rate and high levels of vibration prior to ground contact. According to The Good Aviation Practices publication Helicopter Performance, published by the Civil Aviation Authority of New Zealand (November 2002), "Local terrain, trees, and buildings all influence the flow of wind near them. The mechanical turbulence resulting from this disturbed airflow may become very marked in the lee of the obstruction. A gusting wind situation where windshear is likely to be present will require a greater power margin to deal with any unexpected loss of airspeed and sink." Examination of the wreckage and a post accident engine run revealed no preimpact anomalies.

Probable Cause: The pilot's inadvertent settling with power during a descent. Contributing to the accident was mechanical turbulence in the lee of an obstruction in windy conditions.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: NYC06LA062
Status: Investigation completed
Duration: 2 years and 4 months
Download report: Final report

Sources:

NTSB NYC06LA062

Revision history:

Date/timeContributorUpdates
09-Oct-2022 06:56 ASN Update Bot Added

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