Steel oil line fittings

I?m close to installing my oil cooler lines. In all of the reading I?ve done about homebuilding, I seem to remember that somewhere it was recommended to use steel fittings on the engine for the oil cooler lines. Has anyone else read this? If so, where? Is this correct?
Also, I?m mounting my carb/FAB. The Lycoming manual shows that the safety method for attaching the carb to the sump is with locknuts in addition to the plain nuts. This is different than the older certified aircraft that I am familiar with (safety wire and castle nuts). The threads on the sump studs are 5/16?18 course threads. All Pal nuts and check nuts that I?ve seen in catalogs are 5/16-24 fine thread. Where have others purchased these locknuts?

Thanks in advance,
Cameron Smith

Oil cooler fittings

Cameron: I think the plans call for regular AN fittings on the oil cooler. But, many builders have posted bad experiences with the aluminum fittings and recommend changing to steel. I went with steel on the two oil cooler fittings for this reason. I am pretty sure that I followed the firewall forward plans for the engine connection. I am sure that someone more knowledgeable will pipe in on this. It's been discussed on various lists and forums several times. Jack

One of the main reasons it's not a good idea to use aluminum fittings screw into aluminum is because of galling that can/will happen while tightening. Not to mention steel fittings are more durable and not as prone to breaking off from vibration, or over tightening to get them to the desired position when using a 45 or 90 degree fitting.

just use steel

Just use steel, and never worry about it. Here, a picture is worth 1000 words:



For more info: http://www.rvproject.com/20040519.html

)_( Dan
RV-7 N714D (585 hours)
http://www.rvproject.com

steel fittings

Cameron, I used steel fittings at the oil supply/return ports on my O-360. I found JIC type fittings in a local hydraulic supply shop. They have the identical flare to AN. JIC stands for Joint Industrial Committee. I recommend steel because the vibration will eventually cack the aluminum fittings.

On the carb, for my throttle body, I used drilled and safety wired nuts.

Jeff Farrar RV8A N4ZJ 750 hrs. Tech Counselor

Steel Fittings

I'm pretty sure somewhere in AC43/regs it says steel fitting are to be used forward of the firewall - then you go buy a $30k Lycoming and it has aluminium AN fittings all over it....? That's where the widespread misuse of Al fittings comes from, I believe. AS mentioned above, I also bought commercial Parker JIC elbows for the oil cooler, and similar steel fittings elsewhere. Cheaper and just as effective.

On a side note, 37? flare fitting are very much out of vogue in the commercial world, like much in aviation they are a remnant of 1930's technology. In critical equipment in the commercial and mining world, they are rarely used, other newer and better fittings are now available. Flared fittings are difficult to do well, especially in confined areas or for a field repair in-situ. The Parker fittings book shows many options that would suit us better in aviation, but many are not available in Al. I have used commercial compression fittings in the fuselage fuel lines where leaky flared fittings were driving me mad.

Any one else have more professional knowledge or experience in this area?