Was surfing around and found this little note on another forum. It applies to a Zenair but struck a note with me. Every time I go to retorque my GSC 66" adjustable pitch prop, the bolts are loose. The prop was just inspected and overhauled by GSC. My torque wrench is calibrated, etc, etc.

Anyway, here's the topic:

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Our CH601HD Zodiac with a Rotax 912S 100 HP engine has a 68-inch, 3-blade
GSC wooden prop. In our installation, there is a prop flange extension.
The prop is held on by 6 1/4-inch bolts (3 through the aluminum blade
roots), and by 6 5/16-inch bolts onto the flange extension. GSC Systems
says use 100 inch pounds of torque for the 1/4 inch bolts, and 140 for the
5/16; these values are critical. Normally, with a washer under both the
head and the nut, one holds the bolt head stationary, and torques the
nylon lock nut; these nyloks are the preferred nuts recommended by GSC.
Because of the design of the prop flange extension, it is not possible to
get the torque wrench onto the nuts. Thus, one holds the nut stationary,
and torques the bolt head. THIS IS NOT THE SAME THING. My son Peter
(co-builder of our aircraft, and a professional mechanical engineer) knows
from practical experience that putting the torque wrench on the bolt head
can undertorque the nut by possibly 20-30%, or even more. It stands to
reason: the bolt shaft (or grip) inevitably experiences some friction in
passing through the parts being bolted together on the way to the nut.
There is a little part called a "crow's foot" to overcome this difficulty,
which goes over the nut, extends radially outward for about an inch, and
has a square hole for attachment of the torque wrench. It happened that I
had always torqued the prop bolts on our aircraft. In setting out to
retorque the bolts yesterday because the weather is now turning cold,
Peter realized right away that there was a problem. I had never used a
crow's foot (I did not know of their existence!). I'm guessing that many
others using this Rotax/GSC prop installation were also unaware of this
problem. What have others done about this? Were they aware of the
problem?

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Anyone else run into this problem?

Chris
Model 2, 582
Sioux Falls, SD