Mailing List flyrotary@lancaironline.net Message #28736
From: Finn Lassen <finn.lassen@verizon.net>
Subject: Re: [FlyRotary] Re: Question for Tracy - was: Off Topic "Switch Placements"
Date: Fri, 23 Dec 2005 23:53:25 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Assuming input to chip is high-impedance, a couple of resistors on the board a factor 10 higher than the pot in parallel with the pot making input to chip mid-range when wiper disconnects. Wouldn't handle the + or ground disconnect, though. More fancy current sensing devices on + or ground side to tell controller that a wire is disconnected is probably overkill.

Finn
 
Tracy Crook wrote:
Good question Perry.
 
  Answer would depend on the exact nature of the 'open' .  Open at ground end, hot end, or wiper.   Answers in order:  mixture goes full rich, full lean, wanders around at last set point.  The pot used is a high rel part rated for 500,000 cycles but of course anything can fail.
 
Most pot failures are 'dead spots' where the wiper goes open at a certain spot (usually near where it is used the most).  Mixture will drift at this point and proper pilot response would be to move mixture to a slightly richer setting, land, get the pot replaced before flying again.  Thanks for the mental nudge, I need to add this to the instruction manual.
 
   I have pondered various fail safe strategies for this scenario (for example, make the B controller fixed at midrange mixture) but so far have not been satisfied with any of them.  Anyone have other ideas to be considered?
 
Tracy
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