A fuel line question

pczar3 · #1 05-18-2011, 08:07 PM

Well, I find myself with a question that I just don't quite know how to answer. I changed my bulkhead fitting on my VSB -6A to steel and changed the line on the firewall side to stainless with steel fittings. Because the fuel line on the -6A from the electric fuel pump to the bulkhead is down by your left foot I decided to switch that over to stainless as well. So now the question. I have enough to run stainless to the fuel selector valve but currently have aluminum fittings in the valve. Can I use the stainless tube with steel fittings on the aluminum fittings I have in the fuel valve? Do I have to change them out to steel as well? If not, what do I use for a torque value? I guess I'm only looking at a few more dollars from ACS to buy the steel fittings but I was just wondering.

Thanks,
Paul

pczar3 · #2 05-19-2011, 08:29 AM

Hi everyone... any help?

Thanks, Paul

SHIPCHIEF · #3 05-19-2011, 08:52 AM

I'm no expert, but I don't think you would want to use stainless flared tube in an aluminum fitting. Stainless Steel is hard and could leave a permanent impression in the aluminum fitting seal surface. Getting a good seal can be a problem at these joints, especially after it has been taken apart and put back together a few times? The torque required to seal them might be high for aluminum? Test for leaks carefully.
Maybe do a Google search about it, and check an aircraft hardware manual?

TS Flightlines · #4 05-19-2011, 09:07 AM

Stainless nuts on aluminum AN fittings is no issue---been used in aerospace for years. Most of your teflon hoses use stainless, or CRES nuts with aluminum fittings. Be careful to have good, clean threads, and dont overtorque the nuts, as you can damage the flare on the fittings. But---issues. My .02 cents worth.
Tom

fehdxl · #5 05-19-2011, 10:27 AM

Quote:

Originally Posted by TS Flightlines

Stainless nuts on aluminum AN fittings is no issue.

But Paul's situation is different: stainless line, aluminum nut, and aluminum fitting.

As I understand the crux of your issue Paul, is, will the stainless line form around the aluminum fitting? Right?

Sorry I don't know the answer though.

-Jim

TS Flightlines · #6 05-19-2011, 10:44 AM

Steel nuts on aluminum fittings. for those imperfect sealing fittings, Spruce and others have "Del seals"--little copper flares that fit on the male adapter, and are pressed on the female flare of the hose or tube end.
Stainless nut are the same thing. Again---my .02 cents
Tom

DanH · #7 05-19-2011, 04:21 PM

I'm with Tom.....we assemble steel hose ends to aluminum fittings all the time.

BTW Paul, my -8 has a stainless hard line with steel nut beginning at the AFP fuel pump's aluminum outlet fitting. The line Z-bends to a steel bulkhead fitting.

TS Flightlines · #8 05-19-2011, 06:37 PM

Hey Dan--you opted for steel nuts and not stainless? Any particular reason?
Also---I wonder how much interest there would be to offer stainless bulkhead fittings, especially like AN832, and AN833? About the same weight as steel. Any thoughts??
Tom

pczar3 · #9 05-20-2011, 06:26 PM

I thought it was possible because a lot of folks have a stainless line forward of the fuselage (me included) that must transition to an aluminum line on the inside of the fuselage. I just didn't want to start chasing all the fittings to change them all because of the aluminum fitting with Steel and Stainless steel junction. To answer one post I was asking about using aluminum AN fittings with stainless tubing and a steel nut.
Thanks again,
Paul