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