Mailing List lml@lancaironline.net Message #53288
From: Wolfgang <Wolfgang@MiCom.net>
Sender: <marv@lancaironline.net>
Subject: Fw: Not a good idea
Date: Fri, 23 Oct 2009 09:49:24 -0400
To: <lml@lancaironline.net>
Randy, I'm confused. I'll keep this on a technical focus.
 
Your gear operation modifications include replacing the HI pressure switch, adding a second pressure switch to the LO circuit and doing some re-wiring of the gear circuit.
 
The result is that when flying along with the gear UP and hydraulic pressure happens to build in the LO side, your modification will drive the pump to start LOWERING the gear while the gear switch is still in the UP position. This is alarming! This will of course reduce the pressure in the HI side causing the HI pressure switch to trip which now reverses the pump and drives the gear back up, finally reducing the pressure in the LO side. With the immediate reversing of the motor, surge currents will be excessive and could possibly trip the pump circuit breaker.
 
What manner of experience and/or engineering allows you to consider this operation a good idea ?
 
Additionally, when on the ground, gear down, and the HI side happens to build too much pressure (which prevents raising the gear), your modification is not able to offer any help.
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The fix I developed does not require any re-plumbing, just adding a small module at the existing pressure switches without requiring any tools to install the push-on connectors. When necesssary, it runs the pump in the direction selected by the current position of the gear switch which relieves the pressure in the opposite side. Also, the module is fully symetric and offers help with both HI side and LO side undesired pressure build up.
 
Wolfgang
 
 
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