Wed, Dec 21, 2011
Worker On The Ground Pulled Lifting Line Bringing It Into
Contact With Rotor Blades
The Civil Aviation Authority (CAA) of New Zealand has released
its preliminary report in a helicopter accident in November which
was shown live on New Zealand television.
YouTube Frame Capture
According to the report:
"The helicopter operator was
engaged by the rigging contractor for the purpose of erecting the
25 meter (82 foot) tall tower for the Auckland Christmas tree
located at Auckland’s Viaduct Harbour.
"The plan was for two lifts to be
conducted. "The first lift was to raise the tower from the
horizontal into the vertical position using the Kevlar lifting
line, the tower pivoting on two bolts in the base. Then, once in
the vertical position, two more bolts were to be inserted into the
base corners and three temporary cable stays would be applied to
hold the tower in place. The lifting line would then be released
from the helicopter’s hook and removed from the tower by a
rigger. The second lift would follow to position the
‘star’ ornament onto the top of the tower.
"The first lift proceeded well,
until it came time to release the lifting line from the helicopters
hook. The pilot then descended the helicopter toward the ground.
The pilot was in radio communication with the rigging supervisor
who was standing underneath the helicopter. When the helicopter
hovered at approximately five meters (16 feet) above the ground,
the rigging supervisor was seen to jump up and grab the lifting
line which was sagging below the helicopter.
"The act of pulling downwards on
the lifting line to release it from the helicopter’s hook
instantly tightened the lifting line, which was still attached to
the top of the adjacent tower, and the strop came into contact with
the main rotor blades. The force of the impact of the main rotor
blades on the lifting line caused massive out of balance forces
within the helicopter’s rotating components, which resulted
in the loss of the structural integrity of the helicopter whilst in
flight. The helicopter then fell to the ground. All parties managed
to escape without injury."
TV New Zealand's ONE News reports that the pilot, Greg Gribble,
said he had no idea why the rigging supervisor, Scott Anderson,
grabbed the line during the procedure. For his part, Anderson told
ONE News that Gribble should not have been hovering below the mast.
He also said that the CAA had not spoken to him about the
accident.
Gribble said that there had been a very detailed plan in place
for the operation, but "unfortunately, it didn't go that way."
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