----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----Fellow Coupers,
Here is a link to an excellent discussion about the hows and whys of bolt torque.
www.avweb.com/news/maint/182851-1.html
Please read this article before you decide that "pretty tight" is a good way to tighten the wing attach bolts. Pay particular attention to the section titled "The Need to Preload a Bolt".
The friction between the wing attach fittings, not the bolt itself, is what is supposed to keep the wing from moving in relation to the center section. The bolts must be tightened properly to apply enough pressure on the "plates" of the wing attach fittings (the joint) to develop the required friction. If the bolts are too loose, then the load will be "felt" by the bolt as a shear load and the bolts and the holes in the wing attach fittings will wear. As I understand it, after discussing it with a mechanical engineer, if the bolts are torqued properly, the bolts will only "feel" a tension load caused by the torque applied to the nut. If the bolt is too loose, the joint will move, and the bolt will "feel" a shear loading.
Below is a copy of an e-mail that Stefan Fanselow posted to the group some time ago concerning wing bolt torque.
Regards,
Wayne
Alon N5618F
Subj: Re: [COUPERS] wing bolt torques again
Date: 6/29/00 10:14:16 PM Eastern Daylight Time
From: [EMAIL PROTECTED] (Stefan Fanselow)
Reply-to: [EMAIL PROTECTED]
To: [EMAIL PROTECTED], [EMAIL PROTECTED]
Here is a copy of the message I put onto the Coupers forum some time back:
QUOTE
As the one who initiated the discussion on the correct torque value for the
wing bolts, I feel compelled to share with the group the final results of
the discussion here on the forum and of my direct communication with
Univair:
1.) The wing bolts need to be torqued properly, just "tightening them really
well" is not sufficient.
2.) There are no recommended values by the manufacturer, so AC 43.13-16 is
the appropriate source
3.) The large and the small bolts used for the main wing attachment are
indeed shear bolts. The nuts are, however, tension type nuts. This had led
to some confusion during the discussion about whether to use shear- or
tension values.
4.) The proper torque values are 1100-1300 inch lbs for the large bolts/nuts
at the leading edge and 100-140 inch lbs for the smaller bolts/nuts at the
trailing edge. Both values are indeed shear values.
I have (for obvious reasons) only confirmend these numbers for the Mooney
M-10. I am assuming that they are the same for Ercoupes / Aircoupes, but I
urge everybody referring to this information for their own assembly to check
for themselves in case the type of airplane is different.
Safe flying, and have fun.
Stefan in Tokyo
Mooney M-10 Cadet
N9547V
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