In a message dated 3/29/2005 10:42:20 AM Central Standard Time, Dastaten@earthlink.net writes:

<< Can I run AL tubing to AL fittings from an AL block to the AL PSRU or again, should it be steel for safety (or convention's ) sake. I'm really not HUNG UP on AL. I just don't want to have to buy ANY part more than once...and I'm getting ready to go buy parts.
 
Dave
 >>

Where there is no relative motion between the mounting points and the tubing, aluminum tubing is acceptable. Keep in mind Murphy works 24/7 on ways to screw up your life. There are miles of soft aluminum tubing in large aircraft. Soft tubing full of oil seeks out resonant frequencies and 4th and 16th harmonics of those frequencies. The longer the run between supports, the lower the frequency that will affect the piece. If it cannot move, it cannot fatigue.

Lynn E. Hanover