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ASN Wikibase Occurrence # 38298
Last updated: 7 December 2021
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Date:18-JUL-1998
Time:16:25
Type:Silhouette image of generic S64 model; specific model in this crash may look slightly different
Sikorsky CH-54A (S-64A)
Owner/operator:Heavy Lift Helicopters
Registration: N64KL
MSN: 64-051
Fatalities:Fatalities: 3 / Occupants: 3
Other fatalities:0
Aircraft damage: Written off (damaged beyond repair)
Category:Accident
Location:Yucca Valley, CA -   United States of America
Phase: En route
Nature:Ferry/positioning
Departure airport:Blythe, CA (BLH)
Destination airport:Apple Valley, CA (APV)
Investigating agency: NTSB
Narrative:
While in cruise flight, a main rotor blade separated. The helicopter exploded in flames and crashed. The green blade had failed an AD directed BIM check the evening prior to the accident. The crew chief recharged the blade with nitrogen and allowed the helicopter to remain parked overnight. The next morning he checked the BIM and found it had retained its charge. The crew of the accident aircraft, who were accompanied by the company's chief pilot in a second aircraft, made the decision to continue to fly the helicopter to its destination. There were several cellular calls both to and from the operator on the evening before the accident. A new exclusive-use contract for both aircraft was already in effect. The maintenance history of the green blade contained an unspecified minor repair after a reported overhaul. The operator stated that, at no time, had it performed any maintenance or repair to the blade. After the blade's mating fracture surfaces were examined, it was found that a hole had been drilled from the underside into the spar. The hole terminated at a conical point that is consistent with a drill bit. Fatigue banding could be seen in the immediate vicinity of the hole. Striations near the conical point, typical of fatigue, were seen with a SEM. The drill hole was under a blade pocket and had not been visible during previous inspections. There is no prescribed inspection/maintenance procedure short of removing the blade pockets that would have revealed the hole. Blade pockets are condition items. Stop-drilling cracks in blade pockets to prevent crack propagation is an authorized military maintenance procedure. Drilling into the spar as part of the process is not authorized. CAUSE: An in-flight main rotor blade spar separation as a result of the pilot-in-command's decision to continue to fly the aircraft after it had failed an AD directed BIM check. Factors were the failure of the operator's chief pilot to maintain proper supervision over the operation of a company aircraft with a known grounding deficiency and the improper repair to the main rotor blade by unknown persons, which damaged the blade's spar.

Sources:

1. http://www3.ntsb.gov/aviationquery/brief.aspx?ev_id=20001211X10621&key=1
Ex CH-54A Tarhe 68-18449 US Army


Revision history:

Date/timeContributorUpdates
24-Oct-2008 10:30 ASN archive Added
24-Dec-2009 12:29 TB Updated [Cn, Other fatalities, Source]
26-Dec-2009 07:33 TB Updated [Aircraft type]
19-Mar-2011 09:30 TB Updated [Time, Source]
21-Dec-2016 19:23 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]

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