PCC Presentation

Hi,

According to http://www.standardcirrus.org/, Knauff did not find it
difficult to get the stabilizer hooked up improperly, nor did the
NTSB. I discussed this with the NTSB investigator. Unless one knows
what Tom describes in the link, and instructs the assistant, things
can happen. There is also a sight glass installed on the top.

Unfortunately, I had the experience of watching the accident occur and
the aftermath. The individual who did the check was NOT instructed on
anything other than to observe movement. I spoke with one experienced
glider pilot who had owned a std. cirrus and never heard of the
potential problem.

The point is, know your manual and any quirks associated with the
glider, instruct your helper in the proper PCC procedure and have
someone double check your critical assembly. And, I sure hope no one
ever takes off having automatic hookups and not performing any of the
checks. Trust nothing to chance.

NTSB Identification: NYC02FA159. The docket is stored on NTSB
microfiche number DMS.
14 CFR Part 91: General Aviation
Accident occurred Saturday, August 10, 2002 in Hilltown, PA
Probable Cause Approval Date: 12/30/03
Aircraft: Schempp-Hirth Standard Cirrus, registration: N47SS
Injuries: 1 Fatal.
The glider was being towed by an airplane for takeoff, when it was
observed to bounce hard on the runway twice, then it assumed a steep
nose up attitude. The tow rope broke, and the glider impacted the
ground in a near vertical descent. The C-hook on the stabilator push
rod, was found in front of, and not connected to the roller bearing on
the stabilator. The pilot's flight experience was over 3,000 hours
with about 84 hours in gliders. He had accumulated 28 hours in the
accident glider, including 17 flights. This was the first glider the
pilot had operated, that he was required to disassemble for storage
and reassemble for flight. Witnesses reported the pilot experienced
difficulty with the assembly process. A view window was located on top
of the stabilator to check for proper engagement of the C-hook, and
the AFTER ASSEMBLY checklist called for it to be used to check for
proper assembly. A witness reported the pilot moved the control stick
in the cockpit and observed movement of the flight controls, but he
was not observed to actually check the view window for proper
assembly. A check of another glider of the same make and model found
it was possible to lock the stabilator in place on top of the vertical
stabilizer, with the C-hook in the same place as found on the accident
glider. In this configuration, the control rod that held the C-hook
was pressed against the roller bearing and held in place by friction.
However, the incorrect assembly was visible through the view window on
top of the stabilator, and when the stabilator was held in place, it
was still possible to move the cockpit control stick abut 1 inch
forward or aft, with no corresponding movement on the stabilator.

The National Transportation Safety Board determines the probable
cause(s) of this accident as follows:

The pilot's improper pre-flight, and failure to follow procedures in
the flight manual to determine that the stabilator was properly
connected prior to flight, and which resulted in a loss of control
while under tow, and uncontrolled impact with the ground.


Chip F.

A witness reported the pilot moved the control stick
in the cockpit and observed movement of the flight controls, but he

I had the opportunity to discuss this in detail with Tom Knauff and the owner
of the Cirrus on which the replicated the failure mode.

The flight control would move correspondingly with the stick movement because
the weight of the elevator kept the C-hook and the elevator in contact. IF
either one of the team (PIC at cockpit or assistant at control surface) had
done a proper PCC, it would have been evident either while applying resisting
pressure while moving the stick in full deflection or from doing a jiggle test.

The assistant in this case is a licensed glider pilot.

I was the field manager that day, and hope never to experience something like
this again. To this day, I still see most people there doing a simple prayer
hand PCC. Go figure.

Jim Vincent
CFIG
N483SZ
illspam