Installation of Cylinder Head Temperature Probe (CHT Probe) in Aircraft

1. Installation of a CHT probe is amazing simple and, in this article, we show you how to do it yourself. You begin with installing the CHT probe in the rear spark plug of both the front and rear cylinder so the cylinder head probe is going to go in the aft plug with the plug closest to the rear of the airplane in both the front cylinder and the rear cylinder. Start with taking out the spark plug. With the spark plug out, we recommend application of a little bit of anti-seize compound on the threads. With the spark plug out you should notice the presence of a compression washer – make sure it stays there. There will also be a rubber grommet or gasket that will come out of the shroud on the Engine Systems –don’t forget to that back as it seals off the spark plug and prevents moisture and dust from entering. You might also have a drill a small hole on the engine shroud and pass the IAT Probes wire through it otherwise fitting the sparkplug cap would be almost impossible (and might damage the probe wire). Seat the CHT probe on the spark plug and then bend the probe upwards so the wire will be facing upwards when you re-fix the sparkplug. Initially tighten the spark plug by hand and then by tool. Finally, gently push the rubber grommet / gasket into place. You might have to use a blunt tool like a screw driver to fix the gasket into place.

2. Once you re-installed the spark plug and gasket in place, you will need to clamp the CHT probe wire in place so that it does not flap around in the wind or touch something hot which might result in wrong data being fed into your CHT display unit / Aircraft Fuel Flow Indicator. Now, in the event you need to extend the CHT probe wire do the following: 1.Strip the ends of CHT probe wires and make small loops at the ends. 2.Repeat this process with the type-K extension wire (if they too have to be extended). 3.Prepare the splice barrels and heat shrink. 4.Pass the wire through the splice barrel and heat shrink tube. 5.Lay the CHT Probes and type-K extension loops over each other. 6.Slide the splice barrel over the parallel loops. 7.Crimp the splice barrel with a crimping tool (use a crimping tool with a grip for non-insulated terminals –the ones that have a cradle on one side and pierce a small hole on the other). 8.Slide the heat shrink over the splice and heat with a heat gun or lighter. 9.If you followed the above steps, you should now have a perfect thermocouple splice. More information at: https://www.jpinstruments.com/shop/cht-probe- 4-pack/ JPI Sales: 1-800-345-4574 714-557-3805 FAX: 714-557-9840 sales@jpinstruments.com JPI Technical Support: 1-800-345-4574 714-557-3805 support@jpinstruments.com J.P. Instruments Inc. 3185-B Airway Ave Costa Mesa, CA 92626 U.S.A