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ASN Wikibase Occurrence # 35962
Last updated: 3 December 2021
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Type:Silhouette image of generic S64 model; specific model in this crash may look slightly different
Sikorsky CH-54A (S-64A)
Owner/operator:Siller Brothers, Inc.
Registration: N9125M
MSN: 68-18455
Fatalities:Fatalities: 1 / Occupants: 3
Other fatalities:0
Aircraft damage: None
Location:Elko, NV -   United States of America
Phase: Standing
Departure airport:Tooele, UT (YVY)
Destination airport:Yuba City, CA (O52)
Investigating agency: NTSB
While the aircraft was shutting down, the flight engineer exited the aircraft, and gave the pilots the signal that the droop stops had engaged. He then climbed up on a stepladder next to the tail boom as the main rotor continued to coast down to a stop. A minute or so later, the two remaining crewmembers heard a 'thump.' The pilot-in-command (PIC) asked the copilot to go outside and find the source of the noise. When he walked toward the rear of the aircraft he found the flight engineer laying across the top of tail boom with a massive head injury. The main rotor of the Ch-54A is fully articulated. The rotor system employs a series of main rotor blade droop stops. As the rotor rpm slows, centripetal force is reduced and the droop stop springs pull the stops back into ground stop position. During spool down it can take 20 seconds or more for the first through sixth stop to move into the ground stop position. The visual strobe effect, caused by the turning rotor head, can make it appear that all the stops are in place when one or more stops still have not yet been fully repositioned. Winds were gusting up to 14 knots at the time of the shutdown. Gusting winds during shutdown can cause a slow turning rotor blade to suddenly flap down independently of the remaining blades.

Probable Cause: the flight engineer's decision to climb a step ladder that put him in close proximity to the still turning main rotor blades. The gusting wind was a factor in the accident.



Revision history:

24-Oct-2008 10:30 ASN archive Added
25-Dec-2009 10:48 TB Updated [Cn, Operator, Other fatalities, Source]
26-Dec-2009 07:33 TB Updated [Aircraft type]
19-Mar-2011 09:24 TB Updated [Time, Source, Narrative]
19-Mar-2011 09:25 TB Updated [Source]
19-Mar-2011 09:27 TB Updated [Source]
21-Dec-2016 19:22 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
14-Dec-2017 09:40 ASN Update Bot Updated [Cn, Operator, Source, Narrative]

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