Message-ID: <000f01bfedd8$e7b6d0e0$ea46fea9@walter>
From: "Walter Dodson" <coy0te@earthlink.net>
To: "LancairList" <lancair.list@olsusa.com>
Subject: Air & electric pumps both fail
Date: Fri, 14 Jul 2000 14:16:21 -0700
Reply-To: lancair.list@olsusa.com
Mime-Version: 1.0

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Interesting discussion here on the two preferences for panel
security/longevity.  The obvious is to keep your partial panel skills up to
snuff.
Vacuum pumps will fail at the end of their life, mostly.  They run at 100%
flat out all the time.  Unused air is dumped overboard.  A GOOD brand NEW
pump is expensive but when installed and maintained properly they seem to
always make "TBO".  System maintenance is the bugaboo...  any little flec of
dirt will crater a pump.  Filter change seems to bring on pump failure, in
many cases, as does other system maintenance.  This due to dislodged dirt,
etc., enetring the pump and causing early failure.
Alternators in aircraft seem to operate between 50-80% load factor.  Much
higher than a car unit during daylight hours.  These units are modified auto
type alternators made for general aviation by: Prestolite, Ford, Delco,
Motorola, Chrysler, TCM, and Jasco.  They are modified with close
inspection, locking devices on fasteners and hi-altude (hard) carbon
brushes, and maybe more...   I have a selection of hi-altitude brushes left
over from my GA shop days for Ford and Chrysler units that are very popular
there.  There are two type systems out there.  The odd man out is the
American Yankee which used the American Motors "B" alternator electrical
system.  It has a reversed ground and if the sheilding around the feild wire
makes ground the alternator will "run away" toasting all radios in "short"
order.
I opt for a mixed panel, ie., half vacuum and half electric.  It is tried
and true, any A&P will understand it and it provides a modicum of safety.
All stand-by systems are valuable to a pilot no matter how simple.  Needle,
ball and airspeed being the first and most obvious.
I am building for a dear old college friend who has average piloting skills
( 1100 hrs Trinidad time) and I want to provide him with the best of all
worlds: familiar, easily repaired and long lasting systems he can count on.
I also believe the resale value of this IV-P will be enhanced, not that it
will ever be sold.
Walter Dodson

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