Reply-To: Sky2high@aol.com
Reply-To: lancair.list@olsusa.com
From: "Scott Krueger" <sky2high@hotmail.com>
To: lancair.list@olsusa.com
Cc: Sky2high@aol.com
Bcc: 
Subject: Lancair LNC2 and Legacy Hydraulic System Problems
Date: Sat, 26 May 2001 07:53:11 -0500
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Message-ID: <F11GtPrPrvCWO6hm8Ua0000593e@hotmail.com>

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The few responses so far have had a common thread but missed the point.  
They all focused on the pump and how Oildyne can fix the problem, service 
the pump, etc.  I have installed a brand spanking new Oildyne pump in my 
320, the same vintage of the one I just received for my Legacy and the 
problem persists.  Let me try to re-state the problem specifically for the 
gear up operation:

1.  The Hi pressure switch must be set higher than the pressure required to 
keep the gear up because extra force is required to overcome gas-spring 
locked over-center links (nose gear 320, all gear Legacy).  Some small leak 
back (cross over, etc.) will occcur whether its because of system ageing, 
manufacturing variance, system construction variance, temperature, day of 
week, phase of the moon, etc.  But, not much leak back occurs since I have 
noted that the gear will remain up for more than three days whilst the 
aicraft sat on jacks.  Even the spring loaded doors didn't come all of the 
way down!  If the master switch is left on, the pressure quickly drops 
enough to have the pressure switch activate the pump for just a blip to 
restore the max pressure.  For me, this occurs every 15 seconds or less.

2.  We are on the third generation of crummy pressure switches -- Lancair 
would be happy to replace my current defective one with another.  Note that 
this "new" type slowly closes the contacts as the pressure builds so that 
electrical static is produced (and heard in the radio) ahead of activating 
the pump relay and which will eventually degrade the contacts.  I know, I 
know.  There are ways to fix the noise by applying another band-aid or I 
could replace the switch and cross my fingers.

3.  The problem is not unique to Lancairs.  My old Skymaster would activate 
the pump in flight every 20 minutes or so.  This was totally acceptable and 
hardly noticeable.  The Skymaster had, arguably, the most complicated 
hydraulic gear system on any aircraft with a very high parts count.  After 
being left alone in the dark for several days the gear leg doors would 
sometime sag down a bit, other times not at all.  There are variances in all 
systems.

The solution to these problems that some of us are having, and others will 
have, lies in the pressure switch.  The most desireable adjustable switch 
would have a dead band of several hundred psi, just like the pressure switch 
that automatically controls your air compressor -- shuts off the pump at 120 
psi, doesn't start the pump again until the pressure drops to 90 or 100 psi. 
  Surely, there is an engineer, scientist, or tinkerer out there that 
perhaps knows a source of such switches.

Help!

Scott Krueger


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