----- Original Message -----
From: "David Carter" <dcarter@datarecall.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Thursday, March 04, 2004 12:26 PM
Subject: [FlyRotary] Aluminum AN fittings - Safety (was Re: [FlyRotary] Re:
ready to start?


> Paul,
>
> You mentioned "aluminum 1/4 NPT to -6AN adapter".  It is my understanding
> that there is a real risk in using aluminum fittings on engines due to
lack
> of "fatigue life" robustness of aluminum, compared to steel AN fittings.
> There have been cases of these aluminum fittings eventually breaking off
> where they are threaded into the engine block.
>
> It is my understanding, from reading the "lists" and articles in Kitplanes
&
> Sport Aviation, that steel fittings are preferred over aluminum - that
> aluminum can actually be considered a safety hazard.
>
> David

I suspect that in case of an engine with lots of vibration such as an
Lycoming that steel AN fittings are a prudent option.  Most folks I know
flying rotaries use Aluminum fittings and as yet, I have not hear of one
failing.  But then that might be because only Tracy has any considerable
number of hours yet. In some cases - like fittings to radiators -  there is
little choice but to use aluminum fittings.  Something to keep our ears open
to anyone who has had bad experience with aluminum fittings.  Needless to
say any fitting whether steel or aluminum should have minimum stress from
hose/tubing attached to the fitting.


Ed Anderson