> The switches fail due to dirt on the contacts. I have heard of persons
> dismantling the switches and cleaning the contacts in order to avoid a high
replacement cost. Not allowed on a Public Cat aircraft of course.
If you look for microswitches with IP67 rating these are sealed against dirt,
vapour and moisture ingress so you won't then need to worry about cleaning
contacts.
Another option is to do the job with an electronic pressure sensor. The
mechanical version depends solely on the fact that the airflow is keeping the
vane raised, when the airflow ceases at the stall the vane drops and makes
the switch. In effect it is a crude, but effective pressure switch. I would
think that a small tube mounted at the correct angle to leading edge with an
electronic pressure sensor at the other end and an appropriate circuit would
give the desired result. Once you have the tube in the correct position then
the electronic version has a benefit in that you can easily alter the
sensitivity of the system with the turn of a potentiometer.
Tony
#272 ZK-TSK
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Tony Krzyzewski tonyk@kaon.co.nz
Managing Director Ph 64 9 358 9124
Kaon Technologies Fx 64 9 358 9127
Auckland
New Zealand
Networkers visit www.kaon.co.nz
Aviators visit www.kaon.co.nz/europa/272index.html
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