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AN924-6D vs AN818-6D Torque Values

Meat

Active Member
Patron
Hello All,

I'm installing fuselage fuel lines and looking for some clarity on torque values for the fittings. Specifically I'm looking for torque values for both the AN924-6D jam nut on the AN833-6D 90-degree elbow and the AN818-6D B-nut on the 3/8" flared tubing.

In the Standard Aircraft Handbook, p.203, Table 7-19, it specifies for aluminum alloy tubing, bolt fitting or nut a torque of 75-125 in/lbs for any -6 size hardware. This torque value would seem to apply to ALL aluminum -6D sized hardware

However, in AC43.13, Ch 9 Hydraulic Systems, Table 9-2 it specifically mentions AN818 nuts. It specifies for aluminum alloy tubing a torque of 110-130 in/lbs for a -6D nut. The lower range is significantly higher then the 75-125 in/lbs value in the Standard Aircraft Handbook.

Can anyone shed some light on the correct values for each type of -6D nut? And given the wide torque range each reference gives what initial torque value should I go for on each nut? Lower range? Middle?

Thanks for your time and advice.

Cheers,
Scott
 
B Nut Torque

I don't believe you will find 3003 aluminum tubing torque values in AC43.13.
The 110-130 inch lbs are for certified aircraft work, which uses a much stronger aluminum tubing (5052). I use 110 inch lbs for size 6 B nuts on 3003 aluminum tube as the maximum value. If you're using hoses from a manufacturer, then use their recommended torque. The torque is really referencing the material being squeezed and soft tubing is a lot different than steel, etc.
Here is link to a youtube that explains much of your question.
https://www.youtube.com/watch?v=VGwIrh33CpI
 
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