[alpinelakespilot2000]

Doing the final torque inspection of all my fuel and vent lines...

In Van's publication on torquing aluminum fittings (see below), "alternate tightening method one" using the flats method suggests tightening the fitting by hand until "it bottoms the seats" and then tighten further the amount of flats shown on the chart. How do you know when the seats have "bottomed"? How is this different than "alternate tightening method two" in which you tighten by hand and then rotate an additional quarter of a turn?

(I'm not sure how alternate method #2 could be consistent from one builder to another because it depends on how strong our hands are, but I can see how alternate method #1 might work, if I only knew how to recognize the bottoming of the seats.)

http://www.vansaircraft.com/pdf/Torque_Spec_Aluminum_Fittings.pdf

Thanks.

 

[Toobuilder]

Tightening tubing by "counting flats" was pretty common even in military aircraft until not long ago. The best way to know when it is "bottomed" (ergo, where to start), is generally found by feel, and is indicated by a sharply rising torque value. If the tube is straight on the fitting, not cross threaded, and the flare is not oversize and dragging on the nut, it should be easy to feel when it is bottomed out - it simply gets tight real fast.

 

[Experimental Chaos]

snug

If everything is straight and not cross threaded you can tighten by hand, then ?snug up? with a wrench (I know, I know, what is ?snug up?) then back off with the wrench, when you come back to seated point in the torqueing sequence the point where the torqueing effort increases will be quite distinct, tighten the appropriate amount from that point. After a few fittings it all becomes second nature.

 

[Sig600]

So you take it down as tight as you can by hand, then give it another 1/4 turn with a wrench, and thats it?

Is torque-seal acceptable for use on aluminum fuel fittings to tell if they back off at all?