Dale Walker
I'm New Here
Anyone know what torque value must be added for the fiber lock nuts on the landing gear attach bolts to comply with the SB.
D. Walker, Pa.
D. Walker, Pa.
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Torque
- Thread starter Dale Walker
- Start date
MacPara
Well Known Member
Dale, could you specify which lock nuts you are referring to?
There are 3 different sizes used on the attach blocks. AN5 on the outboard block and AN3 or 4 (can't remember right now which one) and AN6 on the inboard block. In respect to their sizes they require the torques listed in the torque table in the SB. You would add whatever prevailing torque you measure that is necessary to make the nut turn (freely). If you torque the nut and not the bolt (you torque the nut when the bolt stays put and does not move), the prevailing torque is what you need to overcome the friction from the lock ing feature of the nut. In my case that was below 10in-lbs on all sizes nuts that were used BUT that might not be the case with yours. You really have to check that by measuring - which is why Van's didn't tell you what to add.
There are 3 different sizes used on the attach blocks. AN5 on the outboard block and AN3 or 4 (can't remember right now which one) and AN6 on the inboard block. In respect to their sizes they require the torques listed in the torque table in the SB. You would add whatever prevailing torque you measure that is necessary to make the nut turn (freely). If you torque the nut and not the bolt (you torque the nut when the bolt stays put and does not move), the prevailing torque is what you need to overcome the friction from the lock ing feature of the nut. In my case that was below 10in-lbs on all sizes nuts that were used BUT that might not be the case with yours. You really have to check that by measuring - which is why Van's didn't tell you what to add.
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Dale Walker
I'm New Here
Thanks Mac. I did locate a dial type torque wrench. You are correct, the 1/4 and 5/16 are 10 Inch pounds and I got 20 inch lbs on the 3/8". That is the torque required to overcome just the resistance of the fiber lock.
Dale
Dale
I just torqued everything to the max range and figured the max-to-min margin would handle the locknut running torque. Seems to work. Life is imprecise.
AC34.13 (and I believe, now also added to construction manual Section 5) has specific information for mechanics regarding evaluating and compensating for prevailing torque on self locking fasteners.
Maybe life is precise, Scott! 
