I was asked
to travel to Sequim, Washington to perform the intial test flights
on a beautiful new Rotorway Exec 162f. The builder had incorporated
all of the safety modifications that are on this web site and
his construction was flawless.
the intial test hovers and made a few minor adjustments. Once
I was satisfied that the helicopter was ready, Richard joined
me (following the ballast weight change) in the cabin. Richard
was just completing his third hour of hovering. The helicopter
was flying perfectly with no unusual tendencies. We were in a
stationary hover with about a 2.5 ft. skid hight when all of a
sudden our heads slammed into the cieling of the helicopter.
no sinsation of rotating about the longitudinal axis of the helicopter
because the helicopter rotated so fast that it turned nearly inverted
in the time it takes the main rotor blades to make one half of
a revolution around the rotor plane (about 1/13 of a second).
We felt the helicopter fall back onto its side and we immediately
climbed out of the broken windscreen opening.
awhile for us to process what had just happened but between the
NTSB, the FAA, and ourselves, we pretty soon discovered the sequence
of events that led to this crash.
retreating main rotor blade was nearing the tail boom the top
skin of the blade suddenly delaminated from the blade structure
and curled up destroying all lift on that blade. The advancing
blade was nearly in the forward position of the rotor disc when
the retreating blade delaminated. The forward blade was now the
only blade that was producing lift and it immediately slammed
up so hard that it bent the main rotor shaft and snapped the bottom
skin and spar of the retreating blade.
Due to gyroscopic
precession, the tremendous upward force that the forward blade
exerted on the rotor mast was "felt" 90 degrees in the
direction of rotation- to the right. This tremendous force rotated
the helicopter about its longitudinal axis nearly 180 degrees
where the skids never touched the ground and the main rotor swashplate
hit the ground first.
blade with the broken bottom skin and spar continued only 180
degrees to the forward position held onto the rotor hub only by
the small brass counter-balance rod on its leading edge.
sequence of photos pretty well tells the story.
photo shows the dirt inbeded in the main rotor hub from hitting
the ground when the heliciopter inverted. The flat plate on top
of the rotor hub is a device used for fine balancing of the rotor
system. Note that these blades are not Rotorway blades but were
made by the Safari company.
helicopter came to rest on its side and the upper skin of the
rotor blade in the foreground shows where it delaminated from
the blade spar.
photo shows the bottom skin and spar of the delaminated blade
completely separated from the main rotor and held on only by the
brass balance rod.
photo shows the rotor blade spar that snapped under the incredible
forces applied to it when the upper skin delaminated.
above shows the helicopter after we recovered it and moved it
to the hangar. The lower surface of the delaminated blade is in
the foreground and the upper skin is shown still attached to the
blade root end.
is to always use the stock Rotorway main rotor blades on these
helicopters. This could have easily been a double fatality.