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Thanks Jeff
I think Tracy having selected a quality pot mitigates against failure, but all single point of failure components introduce risk.
I thought my test pilots question was a good one for us to consider.
One of the contractions he flys is a twin jet CriCri whose throttle is a Bournes Pot.
Cheers
Steve Izett
On 17 Sep 2019, at 10:15 pm, Jeff Whaley jwhaley@datacast.com <flyrotary@lancaironline.net> wrote:
Steve, this what-if scenario of the mixture pot failing is not something ever discussed before. What I can say based on experience with the EC2 is that IF the pot failed at full-lean and then Cold Start was selected that the outcome would likely be acceptable; on the other hand, IF the pot failed at full-rich the outcome would not be good.
How can a potentiometer fail ? Given that it is a resistor the most likely scenario is exposure to excessive current and again from experience, the resistor value can end up anywhere from an open circuit to a dead short. Another possibility is the wiper mechanism can fail, leaving you without adjustment and stuck at whatever the last setting was - if you're lucky it should be near the middle and all will be okay.
Jeff Hi there guys.
A friend of mine who is testing our Glasair has asked after the failure modes and consequences of the mixture pot on the EC2/3 controller.
I'm figuring it would go full rich or full lean. Either being a real problem for keeping the engine running effectively.
Not sure what a faulure of the pot to full lean and then selecting Coldstart would yield as far as mixture, I imagine far too rich.
I take it Tracy used quality pots to mitigate this risk factor.
Has anyone discussed this before?
I'd like to be able to give my friend an answer.
Cheers
Steve Izett
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