Conflicting Torque Values

[Daniel S.]

Slighly confused here. I'm about to torque the fuel tank AN fittings. the torque chart on Van's site says 270-350in/lb for -8 fittings, AC43-13 (section 9, page 19) sites 230-260 in/lb & The Aircraft Mechanics Handbook sites 150-250 in/lb... Anyone know off hand what is correct for the fuel pick up & vent (-4) line fittings?

Thanks all

BTW I did search VAF & found more conflicting data

[WingsOnWheels]

I assume you are refering to the 3003 aluminum tube connection to the tank fitting:

Those Vans torque values are for hose fittings (like the FWF fuel hose, oil cooler, ect. Now for soft aluminum tube. The standard for the versatube is one flat past seated. More than that will damage the flare.

Edit: After re-reading your post I'm not sure what fittings you are refering to. You mention -8 fitting, but I can't think of any -8 in the fuel system (RV-8 may be different from the -6).

[Daniel S.]

Okay here I go answering my own question ... After doing some research & talking to Van's, here is the skinny. There are 2 different torque values used for AN fittings. Please chime in if you've heard differenly. I hope this might help others who scratch their head when it comes to installing the fuel tank blue AN fittings.

-Torque Value #1. When the junction includes a flared aluminum tube & sleeve, the values are as follows.(When using the AN 818-** nuts)

-4 min 50 max 65
-6 min 110 max 130
-8 min 230 max 260


- Torque Value #2. When using the AN924-** nut. The plain nut usually used for mounting the fitting through the structure. (Bulkhead and Universal Fitting)


-4 min 100 max 140
-6 min 150 max 195
-8 min 270 max 350