Rear prop spinner
 

1973 T337G, P-model, SN P337000063. N3CU.

The rear prop spinner has developed a 1/4" crack in the radius cut-out that accomodates the prop root, just aft of where the backing plate ends.

This will be the second rear spinner I've had to deal with in the last 8 months.

What causes cracks? Is there a way to prevent them?

What is the most effective way to deal with a cracked spinner? Is there a repair that is worthwhile?

Thanks for any response.

GJ Humphrey
NH

You may want to check out getting your props dynamically balanced. Some IO-360's have some nasty vibrations imbedded in them.

Thanks, Ace. Good advice. Wish I'd done it before my spinner cracked!

At the moment, I'm leaning towards having the spinner welded. This is by far the least expensive option, but in the long run maybe it's not the best. Worth a try, it seems to me.

Welding is not an approved repair on a McCauley spinner. We had a Cessna 414 get a red tag on the door handle by an over zealous FAA inspector doing a ramp check on another plane, and saw it.

I have seen positive and negative results from welded spinners. One failed in flight, and spun down the leading edge in flight, causing a bunch of sheetmetal damage. Others just plugged along.

Remember, if its not an approved repair, your airworthiness certificate (block 13) is not valid, and your insurance will be at risk.