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The owner of an ASW-20 arrived at
the airport one spring morning and began to prepare for a local soaring
flight. The weather looked promising with high, scattered clouds, light
winds and good visibility forecasted for the remainder of the afternoon.
The commercial pilot had owned the glider for less than one year although
he had flown the aircraft frequently during that time. The glider was
itself notable, being serial number 20001, the first of the ASW-20 series
gliders produced by Schleicher.
After completing the assembly, the pilot positioned the aircraft for take-off,
the last of a group of gliders flying that day. While waiting for the
tow aircraft to return, the pilot and a close friend, a former partner
in the glider, completed a check of the flight controls. After the tow
aircraft returned, the towline was connected and final preparations for
take-off were completed.
Shortly after beginning the take-off, the glider was observed to lift-off
much sooner than normal. Immediately after leaving the ground, the glider
began an uncontrolled climb to a pitch attitude of approximately forty-five
degrees. A witness stated that he was becoming increasingly concerned
for the safety of the tow pilot as the position of the glider began to
force the nose of the tow aircraft down. The pilot of the tow aircraft
then released the towline and the glider began a slow reduction of pitch
to a level flight attitude. The witnesses then observed the wing flaps
of the glider being deployed as the aircraft continued to slow to a speed
approaching a stall. The glider then pitched down to a forty-five degree
angle and impacted the ground. The pilot of the glider was fatally injured
in the accident.
During a post-accident investigation of the flight control system, investigators
determined that the elevator control push rod was disconnected from the
elevator at a quick-disconnect fitting in the vertical stabiliser. There
was no damage noted to the elevator bell crank or the terminal end of
the elevator control push rod. Control continuity was established for
the remaining primary and secondary flight control systems.
How to prevent similar occurrences
At the conclusion of its investigation, the National Transportation Safety
Board determined the probable cause of the accident to be:- The failure
of the pilot to attach the elevator control rod to the elevator, resulting
in a loss of pitch control and subsequent ground impact. Additional factors
were the failure to complete a positive control check and the lack of
clear guidance in the assembly procedures. Although the National Transportation
Safety Board was very direct in assigning the probable cause of this accident,
it is equally important to determine how the error went undetected by
the pilot and most important, how to prevent similar occurrences.
Prior to take-off, the pilot of the ASW-20 enlisted< |
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