217 – Does Your Magneto Have Any Broken Teeth?

Airplane Owner Maintenance - By Dean Showalter

I recently removed a magneto from a Piper Cherokee, and my curiosity about why the magneto had failed got the best of me.

I took the mag home, sat down at the kitchen table, put my grandson Spencer on my lap, and took the magneto apart! It was great fun having him help me

Before long, we had the case apart, and it quickly became obvious why the magneto wasn’t working… there were 6 broken teeth on the distributor gear! And 3 of the broken teeth were together in a row, making it impossible for the distributor gear to mesh with the drive gear… this mag was completely dead.

It had been more than 600 hours since the last 500 hour magneto inspection.

I wonder how long it had been since the first tooth broke… we’ll never know.

But it does remind me of the importance of doing 500 hour magneto inspections. For Part 91 airplanes, it’s a recommendation and not a requirement, but in this case, I think the recommendation is a really good one.

You can listen to the podcast episode for more details about the troubleshooting process on the magneto, and here are some other items also included in this episode:

• Some King Air flying this week (I never get tired of the “view from the office!”)

• Our complex ATC clearances we received on the way to the Boston area.
• The annual inspection I’m currently doing on an A36 Bonanza… here’s the overhauled alternator drive coupling I installed because the old one failed the slippage torqe test:

• Our IA renewal seminar at Blue Ridge Community College… it’s always a good time to see friends, learn some things, and satisfy the FAA requirements to keep my IA certificate current.
• And finally, Maria and I are getting very excited about our trip to Hawaii! We’re going to visit John and Leslie Caubble on Maui, and I’ll be working with them on the flight school airplanes at FlyMauiHI.com It’s going to be a grand adventure!

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