alpinelakespilot2000
Well Known Member
There seems to be a contradiction from Van's regarding torque on AN fittings. They post the Aeroquip guide for torque values on their FAQ site (see below). Most of our hard aluminum lines use size 6 fittings. According to the guide, these require 150-195 in-lb. That's what I've started to use.
http://www.vansaircraft.com/pdf/Torque_Spec_Aluminum_Fittings.pdf
However, when I recently did my fuel tank service bulletin, I notice that they specify 110-130 in-lb for the fuel pick up tube, which is also a size 6. That's a very significant difference! In fact, at the extremes of the ranges, it's almost twice the torque!
http://www.vansaircraft.com/pdf/sb06-2-23.pdf
In trying to reconcile this apparent contradiction, one of the main things I wonder is whether the torque for our soft aluminum tubing should be different from the perhaps harder materials used in Aeroquip hoses. Anything to that theory? Or is this just a contradiction we have to live with and make up our own mind about?
Anyway, if anyone could clear this up for me, that would be great. Making up my own rules on fuel lines is too exciting for me!
(FWIW, on the occasions where I can't get a torque wrench on the fittings, I often use one of the alternate tightening strategies, such as hand tight + 1/4 turn or bottom the seats then a certain number of additional flats. Still I'd like to know what the torque values really should be when I do use a torque wrench.)
http://www.vansaircraft.com/pdf/Torque_Spec_Aluminum_Fittings.pdf
However, when I recently did my fuel tank service bulletin, I notice that they specify 110-130 in-lb for the fuel pick up tube, which is also a size 6. That's a very significant difference! In fact, at the extremes of the ranges, it's almost twice the torque!
http://www.vansaircraft.com/pdf/sb06-2-23.pdf
In trying to reconcile this apparent contradiction, one of the main things I wonder is whether the torque for our soft aluminum tubing should be different from the perhaps harder materials used in Aeroquip hoses. Anything to that theory? Or is this just a contradiction we have to live with and make up our own mind about?
Anyway, if anyone could clear this up for me, that would be great. Making up my own rules on fuel lines is too exciting for me!
(FWIW, on the occasions where I can't get a torque wrench on the fittings, I often use one of the alternate tightening strategies, such as hand tight + 1/4 turn or bottom the seats then a certain number of additional flats. Still I'd like to know what the torque values really should be when I do use a torque wrench.)
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