More detail on this person: NTSB
Identification: LAX98FA236 .
The docket is stored in the Docket Management
System (DMS). Please contact Records
Management Division
Accident occurred Saturday, July 18, 1998 in
YUCCA VALLEY, CA
Probable Cause Approval Date: 6/22/2000
Aircraft: Sikorsky CH-54A, registration: N64KL
Injuries: 3 Fatal.
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.
The National Transportation Safety Board
determines the probable cause(s) of this accident
as follows: 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.
This information was last updated 05/18/2016
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