Sender: <marv@lancaironline.net>
To:  lml@lancaironline.net
Date: Sat, 15 Nov 2008 10:06:56 -0500
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From: "Bill Wade" <super_chipmunk@roadrunner.com>
References: <list-3301419@logan.com>
In-Reply-To: <list-3301419@logan.com>
Subject: Re: [LML] Prop Length for 360
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  You wouldn't have any noticeable vibrations if the prop is balanced 
correctly but that doesn't necessarily mean that there are no problems. My 
understanding is that engine/prop combinations are tested on specific 
airframes and the results may not apply to other setups.

  My Chipmunk was the prototype for a TCM IO-360 engine conversion STC in 
the sixties. Part of that is a custom Hartzell prop. I was able to get a 
copy of the test results and it turns out there's a limitation that centers 
on 2500 RPM due to harmonics that could stress the blades over time. The 
prop itself runs very smooth- when I had it dynamically balanced it required 
almost nothing for weights.

  OTOH my Navion has an STC'd engine conversion that uses a Bonanza FWF 
IO-550 and McCauley prop. I doubt it was tested in the same manner- probably 
they just put it on and made sure it didn't tear the airplane apart. There 
is a recent AD on the prop restricting MP/RPM combinations but that's for 
all installations not just mine. Go figure.

  Hope this helps but now you're probably as confused as I am-  Bill Wade

----- Original Message ----- 
From: <mmcmanus@grandecom.net>
To: <lml@lancaironline.net>
Sent: Saturday, November 15, 2008 7:36 AM
Subject: [LML] Prop Length for 360


> I'm in the middle of getting my Hartzell 2 blade prop overhauled for my 
> Lancair
> 360.  I got a new hub at 50% discount from Hartzell to eliminate the 
> recurring
> eddy current inspection. The prop shop doing the overhaul has issues with 
> the
> blades and they will not issue the formal 8131 (I think) paperwork for the
> overhaul.  The problem is the blade length.
>
> I bought the airplane 3 years ago and it had an overhauled "0" time prop 
> when
> the airplane was built in 2002. The blades are 70" long according to the 
> prop
> shop.  They also say that the Hartzell recommends a 72" blade. But 
> Hartzell
> also allows a 68" blade for the Lyc 360.  They do not however, recommend a 
> 70"
> blade.
>
> The question is, since I've had no problems or vibration issues with my 
> 70"
> blades - should I be concerned? I guess Hartzell's recommendation is based 
> on
> some harmonic resonance or some other vibration related things (which are
> outside my knowledge).  Does my 70" blade length provide cruise or climb
> capabilities that are greater or lesser than a 68" prop.
>
> I'm planning to have the 70" blades reinstalled on the new hub, and the 
> log
> entry will just say the standard overhaul stuff (except the IAW stuff), 
> and it
> will specify "experimental A/C usage only."
>
> Any thoughts?
>
> Thanks,
> Matt McManus
> lnc2 360
> 408 hours total time airplane.
>
>
>
>
> --
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> http://mail.lancaironline.net:81/lists/lml/List.html
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