242 – Your Airplane’s Alternator: Neglected or Well-Cared-For?

Airplane Owner Maintenance - By Dean Showalter

In this podcast episode, we’re talking about alternator maintenance!

Here’s the alternator I removed from a Beechcraft Bonanza to inspect the drive coupling and the brushes… note the brush assembly in the lower right side of the photo:

The brushes had plenty of length left, but they needed a good cleaning due to carbon dust that had collected from normal brush wear. Check it out:

After a good cleaning, the brushes looked great and were ready to reinstall.

Another thing (and perhaps more important) I wanted to check on this alternator is the elastomer drive coupling:

There have been numerous cases where these drive couplings have come apart and caused serious engine damage and / or failure.

Since it had been nearly 500 hours since this alternator was removed and inspected, I wanted to verify the drive coupling’s condition.

I performed the following: (Reference Continental M-0 manual.)

• Verified no slippage at 140 inch pounds.
• Verified proper coupling attach nut torque.
• Installed new cotter pin.
• Cleaned off old gasket and installed alternator with new gasket.

If you have a belt driven alternator, it’s important to keep the belt tensioned properly and in good condition.

How about you?

Do you have a plan for proactive preventive maintenance on your airplane’s alternator?

If not, you may be interested in listening to the audio for this episode, and then make a plan that best fits your situation.

It’s certainly a good idea to check alternator brushes each 500 hours.

And for gear driven alternators, it’s probably wise to check the drive coupling at a shorter interval than that. There have been too many stories of these couplings coming loose and / or coming apart, and if we can prevent that, it’s always a good thing!

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For some additional discussion on this topic, here’s some interesting info I found on the Pilots of America site:

When to Overhaul / Replace Alternator

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