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Second prop spinner bulkhead fail in a year

Beav1988

I'm New Here
RV-8 with AEIO-360 (200 hp) with a Hoffman 2 blade composite CS prop. Last year, the spinner bulkhead failed, causing the spinner to wobble and gouge the prop, requiring it to be removed and remanufactured. Got the prop back in June.

Now, 55 hours later, the new spinner bulkhead has gouged in to two pieces - fortunately, I found it as soon as it happened, preventing serious damage to my prop. I don't think I am doing anything unusual inflight. Prop full forward for takeoff, reduced to 2500 rpm for climb and aerobatics, 2400 for cruise. There are no rpm limits published in my prop manual.

Does anyone have any idea why this would happen?
 
Perhaps there isn't enough clearance around the prop holes.

Perhaps you need to have the engine and prop dynamically balanced.

Or maybe the spinner bulkhead is not right somehow.

Should there be a forward bulkhead keyed to the prop hub?

No experience with this but these seem like places to look.

Dave
 
Additional info would be useful.

You are using a prop that very few people use which might be teh reason for very little response.
Is the spinner supplied with the prop by the manufacturer or is it the Van's Aircraft spinner?
 
It would seem to me that your spinner is not mounted "true" to the spinner bulkhead. You are probably experiencing a slight "wobble" which is causing a constant stress on the backplate. I would check the tracking of the spinner. Dynamic balancing is always a good idea, however if the spinner in out of alignment then balancing will not solve the problem.
 
Where & how is the bulkheads failing?
Do you run mags, or EI? If so, locked in timing or what advance curve?
I remember Hartzell having concerns with certain props with EI ignitions & their power pulse resonance.
More info as mentioned would be helpfull.
 
Thanks for all the responses.

- I am running mags, not EI.
- The spinner is custom from Hoffman.
- The bulkhead failed in a perfect circle around the prop mounting bolts, as if cut by a saw, indicative of metal fatigue caused by spinner wobble.

Unfortunately, unlike the Van's spinner, there is no screw attachment to the forward bulkhead - the forward spinner bulkhead is a vinyl/plastic piece that "floats" in the spinner.

Update: I am not the original builder of this airplane, so I was not involved in the decision to put this prop on the airplane. After this second failure and lack of response from Hoffman, I have purchased a Hartzell prop from Van's which ships today.

Once the Hoffman is repaired, I'll likely put it up for sale.
 
Good idea. Right now, I'm going to let Hoffman play this out before I do that, though. I'm kind of hoping that they will do this under warranty since it failed so quickly after manufacture.
 
Unfortunately, unlike the Van's spinner, there is no screw attachment to the forward bulkhead - the forward spinner bulkhead is a vinyl/plastic piece that "floats" in the spinner.

Don't actually need screw attachment to the forward bulkhead, just zero clearance at the interface of the spinner inner surface and the front bulkhead. I've flown a Vans spinner 950 hours with a molded proseal "gasket" on the bulkhead flange. After removing the rear bulkhead screws, pulling the spinner off is like pulling a cork from a bottle.

Vinyl/plastic? Sounds too soft.
 
+1 to DanH. Also - was very careful in alignment to prevent wobble. 200 hr on mine. No issues so far.
 
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Don't actually need screw attachment to the forward bulkhead, just zero clearance at the interface of the spinner inner surface and the front bulkhead. I've flown a Vans spinner 950 hours with a molded proseal "gasket" on the bulkhead flange. After removing the rear bulkhead screws, pulling the spinner off is like pulling a cork from a bottle.

Exactly the same here, around 800 hours. In fact, it was probably your instructions that I followed for the "screwless spinner" (which came out *awesome* is one of the things I like the best about my -7A :) ). It's a good, snug fit and like you say, takes just a bit of pulling to have it "pop" off for servicing. Quite happy with it!
 
You are 100% correct. There was a bit of play between the spinner and the forward bulkhead - Hoffman's solution was to put a rubber gasket/O ring on it. That didn't work too well.
 
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