Q: On a recent pre-annual inspection of my “sweet” flying Champ I noticed the plastic tips on the alternator (see photo below) missing from most of the fins. I think the missing tips have been gone long ago, but no problems at all.
I can’t find any recalls, ADs, or even specs on alternator problems. Is this a condition likely to fail an annual?
Enjoy reading your column and General Aviation News.
Paul Sieber
A: Paul, thanks for including that good picture of your alternator. It certainly shows the problem well.
My guess is that it probably won’t meet the standards to be acceptable during an annual inspection.
It looks like possibly one of those cable ties got caught in the alternator and it wouldn’t take much to knock those fan blade fins off.
This may have happened during a rough flight when the ignition wires were being shaken, allowing the cable tie to contact the alternator.
If your aircraft were being operated in an experimental category, I don’t think this would be an issue.
The IA signing off the annual will have the final say.
On a Champ, with a low electrical load and what looks like a 60 amp alternator, I don’t think it’s a problem to have some of the cooling fins missing. A load of more than about 30 amps would cause internal heating that may affect the diodes. There should be a scat hose to provide cooling air, from the rear baffle.
You can find a replacement cooling fan and have the mechanic replace it. These alternators were derived from a 1960’s Ford alternator and parts are readily available, including the brush block assembly and diode module.
If the alternator has more than 1,000 hrs on it, it would be wise to check the field brushes for wear, as long as it’s apart.
No such thing as failing an annual. If something is found you have to pay to have it fixed. If you choose not to…then the plane is not airworthy and cannot legally be flown. If you choose to fly it anyway then you risk losing your ticket.