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  #1  
Old 05-02-2006, 08:14 PM
John Slade's Avatar
John Slade John Slade is offline
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Default IVO Prop alert

Cozy Flyer Larry Hill gave me permission to repost the following email:
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I am flying a Cozy MkIV with a Jabiru 5100 and would like to pass on my recent experience with the IVO Magnum, as I observed from your Web sites that you have started using it . This prop gives my exceptional takeoff and climb performance and cruise speed has been quite good as well. On the last flight, the eighteenth, with under 10 hours total, the prop picked up a small dent from FOD. I removed the prop, fixed the gouge and proceeded to reinstall it. Although the stainless witness tapes were OK I decided to replace one as a corner was slightly loose. When I pulled the tape off I was aghast!. The blade root had a large crack from the centre of the root to the nearest bolt hole, easily visible with the prop still assembled. On disassembly all three blades were found to be 40% cracked across the retaining portion of the root.
My concern is that I followed the IVO torquing schedule, used the tapes, and still came close to a disaster. Your engine setups are of course much different than mine but I thought you should be aware that the witness tapes are not a reliable warning of imminent failure.

Larry Hill
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There were no cracks in my IVO when I took it off for balancing a couple of weeks ago. The Jabiru is an 8 cylinder engine so I'd be suprised if the problem was torque pulses. Maybe it was faulty construction. I've asked Larry to let me know what IVO have to say. I'll report any further information on this.
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  #2  
Old 05-02-2006, 09:14 PM
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Interesting. I had 125 engine hours on my first set of blades before the demise of two in my forced landing. On removal, all blades roots were 100%. These had been off at about 55 hours for testing the paddle blades, then re-installed a couple hours later.

My setup sees a max prop rpm of 2180 rpm. Wonder what rpm this other fellow was using and if this causes any problems. The flat 8 should have a smoother torque delivery than my Sube although it is direct drive.
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  #3  
Old 05-02-2006, 10:31 PM
Nathan Gifford Nathan Gifford is offline
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Yeah, that is depressing news.
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  #4  
Old 05-02-2006, 11:43 PM
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John Slade John Slade is offline
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I asked Larry what he thought the cause was. Here's his reply.....

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I think the short answer is overall unsuitability. There was evidence of working on the engine side of the prop root indicating that it could not handle the power pulses even though torqued to the correct value. There was also some black dust on the inside of the spinner, more evidence that the blade root was slowly being ground down by the constant movement of the blade root in the hub assembly. I suspect that if you do not see any dust( black powder) in the hub/spinner area you will not have a problem.
I was musing why you were sending your prop back for balancing ,then it occurred that you may have had the same problem that I experienced. Initially I had difficulty adjusting the pitch in certain RPM bands. I then balanced the prop dynamically and behold, it worked fine from then on. My guess is that the brushes in the motor can't handle much vibration.

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I've seen no signs of black dust or had any difficulty changing pitch. Maybe the Jabiru has too much vibration from the power pulses even though its an 8.
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  #5  
Old 05-02-2006, 11:54 PM
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Black dust is almost certainly brush dust. This is all over my cowling (tractor). There is no carbon fiber in the IVO to my knowledge as I had a close look at the internal construction on my two destroyed blades. On a pusher, it's quite likely that brush material may find its way into the spinner being downstream.

More telling is evidence of working or fretting of the blade clamping faces. This is universally BAD and failure is just around the corner if this is so.

The IVO and the Jab 5100 may indeed not be good mates. I'm just glad this was discovered on the ground.

What has Keith Spruer's experience been to date with the IVO?
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  #6  
Old 05-04-2006, 04:51 PM
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I just had an E-mail from a customer using an IVO on his Rover V8 powered Bearhawk. 260 flight hours to date. No issues. He says performance and fuel burn are almost identical to his friend's IO-540 powered Bearhawk. He has removed the IVO constant speed controller which he didn't like and just toggles the prop like I do.
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  #7  
Old 05-04-2006, 05:13 PM
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Don't forget that a prop swinging behind a wing in a pusher configuration is exposed to conditions that a tractor prop isn't. I don't think this exposure is insignificant.
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  #8  
Old 05-04-2006, 05:23 PM
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Quote:
Originally Posted by tnt
Don't forget that a prop swinging behind a wing in a pusher configuration is exposed to conditions that a tractor prop isn't. I don't think this exposure is insignificant.
You may indeed be right. As the blades cross the wake on a pusher, the IVO blades, being quite flexible, could be exposed to forces not seen on a tractor installation. This may be more significant that the type of engine is is bolted to.

John and Keith are our pioneers here. Check blades often lads!
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  #9  
Old 05-04-2006, 09:25 PM
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Isn't the power curve on those engines a couple of hundred rpm greater than "normal?" Could be a factor.
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  #10  
Old 05-05-2006, 12:50 AM
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Quote:
Originally Posted by rv6ejguy
John and Keith are our pioneers here. Check blades often lads!
John i feels for ya - gotta get sorda tired of being a pioneer at this point
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  #11  
Old 05-05-2006, 02:29 AM
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Quote:
gotta get sorda tired of being a pioneer at this point
Nah. It's fun in a weird sorta way. Life is full of challenges. Yours are a coming - then we can all feel for you.

By the way, I doubt that Larry's black dust is from the brushes. They're very small and wear slowly. It would take the dust from all of both brushes to show anything on the spinner. More likely it's the gelcoat offthe prop getting ground from blade movement - at least thats my guess.

(Back in Florida and ready for some more pioneering after I get my redrive and prop reinstalled).
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  #12  
Old 05-05-2006, 09:22 AM
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It may be more of an issue with the Cozy, but it seems that planes with auto conversions running through redrives don't have a problem and direct drive aircraft engines are having problems.
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