I’ve found a fair amount of Lower Landing Gear attach bolts that were loose ,
stretched or broken.
SB 1375A addresses this but I don’t agree that Time Change is the answer.
Current patient had a broken bolt previously.
Had it analyzed and failure due to fretting.
All bolts replaced with AN.
100 hrs later we are finding the nuts loose again.
One is so loose can spin it with fingers but Torque Indicator paint is not broken.
It must be stretched.
Hole measures .250 Bolts .247
Oddly ; some old bolts are fine on other side.
The plan is to install 4 new NAS bolts on the bottom.
Some concerns:
NAS 6604-11 comes in both Shear and Tension with the same p/n
Is the Torque Spec for a NAS bolt the same as equivalent AN?
Friction Torque + Applied Torque = Desired Torque ( Standard 1/4 - 28 torque)?
Or?
This is not the only aircraft with issues like this.
Many years ago a Pawnee was breaking wheel bolts.
Switching to NAS eliminated the problem.
Could the issues be poor hardware? Incorrect torque or other procedure?
stretched or broken.
SB 1375A addresses this but I don’t agree that Time Change is the answer.
Current patient had a broken bolt previously.
Had it analyzed and failure due to fretting.
All bolts replaced with AN.
100 hrs later we are finding the nuts loose again.
One is so loose can spin it with fingers but Torque Indicator paint is not broken.
It must be stretched.
Hole measures .250 Bolts .247
Oddly ; some old bolts are fine on other side.
The plan is to install 4 new NAS bolts on the bottom.
Some concerns:
NAS 6604-11 comes in both Shear and Tension with the same p/n
Is the Torque Spec for a NAS bolt the same as equivalent AN?
Friction Torque + Applied Torque = Desired Torque ( Standard 1/4 - 28 torque)?
Or?
This is not the only aircraft with issues like this.
Many years ago a Pawnee was breaking wheel bolts.
Switching to NAS eliminated the problem.
Could the issues be poor hardware? Incorrect torque or other procedure?