by Bill Casey » Mon Feb 27, 2017 12:41 am
I was having problems with my tachs in my PA-39, so at last annual I replaced them with Horizons P-1000 Digital Tachs. Also removed the old tach drive cables.
These are very accurate devices. So accurate that you get frustrated trying to sync the engines down to the last RPM, which you can't. After while you just let them drift around and are happy if they are within 20 RPM. With the old tachs you would never have known anyway.
A big benefit of these tacks is that they are monitoring the magnetos all the time. If they sense a difference between the mags they will turn a indicator from green to yellow. If bad enough the indicator turns red.
A mag that checked out fine on a run-up was showing a yellow indicator from time to time. Turns out it had a bad coil and I would not have known until complete failure with the old tachs. A field overhaul of the mag solved the problem.
-Bill