Message-ID: <37F4D91B.9B112B69@regandesigns.com>
Date: Fri, 01 Oct 1999 08:54:03 -0700
From: Brent Regan <brent@regandesigns.com>
To: lancair.list@olsusa.com
Subject: RE: LNC2 hydraulic hoses (LNC4)
References: <19990930043129.AAA25865@truman.olsusa.com>
Mime-Version: 1.0

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I don't like field terminated fittings because they depend on good
technique (meaning you should pitch the first few you do) and they imply
that they are not pressure tested and flushed. Also the stress of
twisting the fitting on can fail some of the reinforcing
strands in the
wall of the hose. I really don't like terminating the stainless jacketed
hose because you come away with your fingers looking like a pin cushion.
Why bother when you can get a better product from Skyranch for about the
same $$s.

The D&H hose assemblies are the ONLY choice for LNC4 gear legs.

Aluminum tubing weighs a lot less than hose, 12 grams per foot, less than
half.

Lancair hydraulic systems operate at around 1300 PSI. Should the pressure
switch fail there is an over pressure relief (OPR) built into the pump
that is set to around 1500 PSI. Should that fail, the pump motor will
stall before 2000 PSI. The only way to get burst pressures  is to crash
the airplane causing one of the cylinders to stroke quickly,
producing a
pressure spike. Of course a little spilled bomber blood would be the
last of your worries.

When a hard line ruptures it usually happens along the length of the
tube at some surface defect, like a scratch. The flares will weep but
usually don't fail.

Regards
Brent Regan


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