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ASN Wikibase Occurrence # 225692
Last updated: 1 June 2019
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Date:04-MAR-2018
Time:23:24
Type:Silhouette image of generic BK17 model; specific model in this crash may look slightly different
Messerschmitt-bolkow-blohm BK 117 B-2
Owner/operator:Air Methods Corporation
Registration: N1174U
C/n / msn: 7146
Fatalities:Fatalities: 0 / Occupants: 3
Other fatalities:0
Aircraft damage: Substantial
Category:Accident
Location:Sheboygan, WI -   United States of America
Phase:
Nature:
Departure airport:Fond du Lac, WI (FLD)
Destination airport:Sheboygan, WI (SBM)
Investigating agency: NTSB
Narrative:
Before departure on the air ambulance flight, standard flight control and hydraulic transfer checks were performed with no anomalies noted with the flight controls. The helicopter’s hover, departure, and cruise were normal. During his approach to the hospital, the pilot started a slow descent using the collective and performed the before landing checks; all systems were normal. However, when attempting to decelerate from cruise speed, the pilot noticed restricted cyclic control movement, about 1 inch in any direction, with normal collective and yaw control movement. He then chose to abort the descent and execute a precautionary landing at a nearby airport.
During the short flight to the airport, the pilot cycled the hydraulic test switch twice with no change noted to his flight controls. During the approach to land, the pilot held the cyclic trim switch aft in an attempt to gain additional aft cyclic authority. With continuous cyclic pressure against the aft stop, the pilot was able to slow the helicopter to 80 knots on final approach. The helicopter touched down near the runway centerline, skidded about 500 ft, exited the runway surface, and came to rest upright. The helicopter sustained substantial damage to the main rotor blades and fuselage structure.
Postaccident examination of the helicopter’s flight control system, including the trim system, did not reveal any evidence of malfunctions or failures that would have precluded normal operations. The cyclic trim was found in the full forward and left position. The flight control dual hydraulic pack was functionally tested on the helicopter and at a repair facility with no anomalies noted. Thus, the reason for the restricted cyclic control movement could not be determined.



Probable Cause: The restricted cyclic control movement for reasons that could not be determined because postaccident examination and testing of the cyclic control system did not reveal any evidence of mechanical malfunctions or failures that would have precluded normal operation.

Sources:

NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20180306X93227&key=1

Accident investigation:
cover
  
Investigating agency: NTSB
Status: Investigation completed
Duration: 1 year and 2 months
Download report: Final report


Revision history:

Date/timeContributorUpdates
01-Jun-2019 07:29 ASN Update Bot Added

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