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Date: Thu, 24 Sep 2009 22:06:47 -0400
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Subject: Re: LNC2 Gear Up & Down Problems
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Lorn,

This post is not to say that there is not a better way to plumb this - 
Lancair clearly felt that way because the Legacy is plumbed differently, 
and I for one would like to understand what your "fix" does.  However, I 
do know from hard experience that if the right pieces are installed the 
original schematic does work fine.

If the original LNC2 (200/235/320/360) gear plumbing was followed, there 
are typically only two issues which can cause problems:

1)  Some pumps were delivered with the spool valve installed backwards.  
This can be corrected, and there are files on this site you can download 
with pictures. 
2)  You may have the WRONG PUMP.  I'm less clear on the cause of the 
second issue - whether they changed the pump specification later or if 
some people simply ended up with an incorrect pump model.  Irrespective 
of the cause, some people have the wrong pump assembly for the job.  
Some symptoms of this include, but may not be limited to:
  a)  The pump stops several times for a few seconds during the 
retraction phase
  b) Sometimes putting the gear handle down (or, less frequently, up) 
does not result in the pump moving the gear until you "burp" the 
pressure relief valve (this one has caused several gear-up mishaps, 
myself included)
  c)  The pump retracts the gear, but does not hold it up tightly during 
flight (the gear "sags" partially out of the wells)

I spent months during my repair time attempting to track down a fix to 
my existing pump.  In theory all of the pump parts are replaceable, and 
since the main casting is common to all of their models (they just put 
different screw-in gizmos in different holes and torque them to 
specified tensions) they should be able to turn almost any pump into any 
other.  In practice they refuse to do this, insisting that you buy a new 
pump - not even letting you use the perfectly good electric motor from 
your old pump (although you can keep that as a spare).

In any event, ever since I had the correct pump installed retraction and 
extension have worked quickly and flawlessly each and every time.


Best regards,

Bill


Lorn H Olsen wrote:
> <div class="moz-text-flowed" style="font-family: -moz-fixed">I have 
> determined that the problem is caused when the hydraulic pressure at 
> both switches is high enough that not only does the pump not run but 
> also high enough that when the dump valve is opened the pressures are 
> still not relieved to be below the pump run setting. eg. If I fly high 
> and the temperature on the ground, after landing, is 60 degrees 
> farenheight more than the temperature in flight, the gear won't go up 
> on the next flight.
>
> An EE friend of mine, after seeing our hydraulic system schematics, 
> talking to Lancair and talking to Oildyne, has come up with 3 
> solutions to the gear not going up and/or coming down. I am out of 
> town and haven't had the chance to see the solutions. Would anyone be 
> interested in a kit that solved the problem for $200 to $400.
>
> -- 
> Lorn H. 'Feathers' Olsen, MAA, ASMEL, ASES, Comm, Inst
> DynaComm, Corp., 248-345-0500, mailto:lorn@dynacomm.us
> LNC2, FB90/92, O-320-D1F, 1,615 hrs, N31161, Y47, SE Michigan
>
> </div>
>