Mailing List lml@lancaironline.net Message #69847
From: Chris Zavatson <chris_zavatson@yahoo.com>
Sender: <marv@lancaironline.net>
Subject: Gear Down...INOP
Date: Fri, 25 Apr 2014 13:47:40 -0400
To: <lml@lancaironline.net>
Chris,
 
Why don't we just agree to disagree. I believe in redundancy and it looks like you don't.
 
The pressure pulse you're talking about will subside (glad you agree) and as it does, because the cylinder is only partially extended, the cylinder will continues to extend, the low switch will close again, and enable the pump to continue . . . No, the damage has NOT been done.
 
The only way the switch will stay open (the pressure stays high) is if there is a physical obstruction preventing the from moving down any further (like when it is full down).
 
Learn to live with the fact that you're not the only one that knows a thing or two about airplanes.
 
Wolfgang
======================
Wolfgang,
It is unfortunate that you do not have a Lancair and cannot go out and observe what we are discussing. The extension failure has been observed by many.  The pressure interaction is clearly visible if one has pressure gauges installed in the panel.  It caught your friend Lorn Olsen off guard and he had a gear up landing because of it.  Damage was definitely done.  The photo he posted of his pressure gauges after the landing very clearly showed the state of the hydraulics during this failure mode.  And no obstruction had to magically appear in his lines to get it there.  Your module will not catch this failure mode.  One switch is open, one is closed, yet the gear is only partially extended.
Advocating not correcting a known problem is dangerous.  Attempting to use a patch to correct a problem is not redundancy. When the patch cannot detect a known failure mode it provides a falls sense of security.

Chris Zavatson
N91CZ
360std
www.N91CZ.net
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