Accident Mbb BK 117 A-4 N951AM,
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ASN Wikibase Occurrence # 296321
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Date:Thursday 26 December 2002
Time:14:40 LT
Type:Silhouette image of generic BK17 model; specific model in this crash may look slightly different    
Mbb BK 117 A-4
Owner/operator:Rocky Mountain Holdings
Registration: N951AM
MSN: 7071
Year of manufacture:1983
Total airframe hrs:6498 hours
Engine model:Garrett-AiResearch LTS101-650B1
Fatalities:Fatalities: 0 / Occupants: 3
Aircraft damage: Substantial
Location:Albany, New York -   United States of America
Phase: Unknown
Departure airport:Albany, NY (NK64)
Destination airport:
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
The helicopter was positioned on the hospital rooftop helipad facing in a southerly direction. After the medical crew boarded the helicopter, the number 1 engine was started. As the main rotor blades began to turn, an unexpected gust of wind traveling over the rooftop caused the blades to flap excessively. The pilot then heard a series of thumps, and aborted the start. Inspection of the helicopter revealed that one of the main rotor blades had come in contact with the left vertical stabilizer, damaging the tail boom, main rotor blades, and the left vertical stabilizer. On November 30, 1990, the helicopter manufacturer issued service bulletin SB-MBB-BK-30-103, which called for a triangle section to be cut out of the stabilizer fin assembly, in an area where a potential strike from a main rotor blade could occur, and replaced with a foam core insert. The operator did not apply the service bulletin to the accident helicopter. The winds reported by the pilot at the time of the engine start were from 340 degrees at 14 knots, gusting to 24 knots.

Probable Cause: The inadvertent encounter with a downdraft during engine start, which flexed the main rotor blades and subsequently damaged the tail boom assembly. A factor related to the accident was the failure of the operator to comply with a service bulletin.

Accident investigation:
Investigating agency: NTSB
Report number: NYC03LA033
Status: Investigation completed
Duration: 1 year and 6 months
Download report: Final report



Revision history:

13-Oct-2022 19:10 ASN Update Bot Added

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