where to find torque for AN924 bulkhead nut?

[IowaRV9Dreamer]

I can't find the torque setting for the AN924-4D nut that holds the bulkhead coupling on to the fuel tank end rib. I can find torque values for the nuts that hold the flared tubes to the coupling, but not the nut that hold the coupling to the bulkhead....

OK - I've figured out that it is a 7/16x20 thread, so the standard thread table calls for 450-500 in-lbs for a "standard" nut or 270-300 in-lbs for a "shear-type" nut. I wonder what kind of nut this is?



Thanks for any help,

[az_gila]

Originally Posted by IowaRV9Dreamer

I can't find the torque setting for the AN924-4D nut that holds the bulkhead coupling on to the fuel tank end rib. I can find torque values for the nuts that hold the flared tubes to the coupling, but not the nut that hold the coupling to the bulkhead....

OK - I've figured out that it is a 7/16x20 thread, so the standard thread table calls for 450-500 in-lbs for a "standard" nut or 270-300 in-lbs for a "shear-type" nut. I wonder what kind of nut this is?



Thanks for any help,

Dave... my FAA AC 65-9 Mechanics Handbook gives 40 to 65 in-lbs for all alum. -4 fittings.

The wording used is - "Alum. Alloy Tubing, Bolt, Fitting or Nut"

So the nut gets the same torque as the flare fitting... makes sense if it's all aluminum.

Steel fittings get 135 -150 in-lbs

AC 43.13 gives 50 - 65 in-lbs... but talks specifically about AN-818 nuts only.... but gives the exact same 135 - 150 for steel...

Aim for 55 and you'll be OK....

gil in Tucson

[IowaRV9Dreamer]

Originally Posted by az_gila

So the nut gets the same torque as the flare fitting... makes sense if it's all aluminum....


AC 43.13 gives 50 - 65 in-lbs... but talks specifically about AN-818 nuts only.... but gives the exact same 135 - 150 for steel...

Aim for 55 and you'll be OK....

gil in Tucson

Thanks Gil - I hadn't thought of that. I guess what's bothering me is that the torque on the flare nut is probably lower so you won't flatten or break off the flare (so 50-65 in-lbs), but I had thought that the torque on the bulkhead nut would be higher (more like the numbers in the AC43.13 torque table - 270-300) to hold it to the bulkhead so it wouldn't rotate.