As part of my education as I consider building an RV, I found the following interesting information regarding bolts. It’s from the perspective of motorcycles, but I still learned a few things that I didn’t know. Perhaps it might by useful for others as well.
http://home.jtan.com/~joe/KIAT/kiat_1.htm
http://www.nobugs.org/bike/bolts.html
I have a copy of the RV-9/9A preview plans, and in Section 3 under Torque wrench, it says, “Aircraft nuts and bolds have specific torque values ... that can only be set with this tool. It is very easy to over torque the small AN3 bolts without one.”
I think I understand the need to tighten bolts to at least the specified value. I’m not sure I understand what harm there is in tightening to more than than that value – not that I intend to do so, I just want to understand. Of course I realize that at some extreme tightness, either the bolt or the material it is clamping will fail. Is that the risk?
Part of the reason for my question is the recent issue regarding engine mount bolts on the RV-12. I may be wrong, but it seems like one of the questions was what torque value to use.
My primary ground instructor told us his experience of having his propellor fall off during a cross-country flight at 9,500 MSL, fortunately within gliding distance of an airport:
http://dms.ntsb.gov/aviation/AccidentReports/0yiglyqaqcun0455oyuct5es/U04152011120000.pdf
The probable cause was “inadequate torquing procedures of the propeller attachment bolts”.
So you see why I might have an interest in bolts and “proper torquing procedures”.
http://home.jtan.com/~joe/KIAT/kiat_1.htm
http://www.nobugs.org/bike/bolts.html
I have a copy of the RV-9/9A preview plans, and in Section 3 under Torque wrench, it says, “Aircraft nuts and bolds have specific torque values ... that can only be set with this tool. It is very easy to over torque the small AN3 bolts without one.”
I think I understand the need to tighten bolts to at least the specified value. I’m not sure I understand what harm there is in tightening to more than than that value – not that I intend to do so, I just want to understand. Of course I realize that at some extreme tightness, either the bolt or the material it is clamping will fail. Is that the risk?
Part of the reason for my question is the recent issue regarding engine mount bolts on the RV-12. I may be wrong, but it seems like one of the questions was what torque value to use.
My primary ground instructor told us his experience of having his propellor fall off during a cross-country flight at 9,500 MSL, fortunately within gliding distance of an airport:
http://dms.ntsb.gov/aviation/AccidentReports/0yiglyqaqcun0455oyuct5es/U04152011120000.pdf
The probable cause was “inadequate torquing procedures of the propeller attachment bolts”.
So you see why I might have an interest in bolts and “proper torquing procedures”.
Last edited: