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04-24-2016, 06:50 PM
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Join Date: Jun 2007
Location: new iberia la
Posts: 768
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Prop Surging
When I was a young mechanic the older mechanics would claim that a flex line could cause prop surging, due to elasticity I presume. In the years since I have seen numerous aircraft with the flex line and have converted and flown some myself. Don't know if it was a urban legend. I have not come across anyone that has experienced prop surging caused by a flex hose, but believe it might be possible. I have the hard line that we will try a some point in the trouble shooting process.
Don B
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04-24-2016, 07:09 PM
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Join Date: Sep 2007
Location: Central IL
Posts: 5,516
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Gasket?
Not based on experience or anything, but did you double check the gasket so the holes and bleeds are in the right place.
It seems like either high flow demand (chamber leak) or restricted flow to the prop, slowing the response. The graphs have the time so broad it is hard to see the synchronization, or offset, of a single event.
__________________
Bill
RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
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04-24-2016, 07:20 PM
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Join Date: Sep 2012
Location: Prairieville, LA
Posts: 221
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All Gasket Holes Aligned
I checked alignment every time I have removed and installed
a governor on the engine.
The one thing I have not done is remove and check the flex hose
from gov to prop.
I plan on doing that in the morning.
__________________
Bert 
RV-9A ?Pearl?
Working on Instrument ticket
Donation Done for 2020
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04-24-2016, 08:01 PM
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Join Date: Jun 2007
Location: new iberia la
Posts: 768
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Quote:
Originally Posted by BillL
Not based on experience or anything, but did you double check the gasket so the holes and bleeds are in the right place.
It seems like either high flow demand (chamber leak) or restricted flow to the prop, slowing the response. The graphs have the time so broad it is hard to see the synchronization, or offset, of a single event.
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A couple more data points for you smart fellas that are helping troubleshoot.
Gasket only goes on one way, the screen goes into the cavity in the gov base and the holes in gasket are symmetrical so even if you could put it on backwards the oil passages would not be blocked.
This prop is not sluggish or hyper, it exhibits a very normal response time when moving the prop control in flight. I think that means oil supply line & fittings will be found to be unrestricted. Both governors have exhibited varying sluggish response time.
Don Broussard (Bert's Assistant)
RV 9 Rebuild in progress
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04-25-2016, 08:53 AM
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Join Date: Sep 2012
Location: Prairieville, LA
Posts: 221
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Oil Transfer Line and Fittings
I checked all this morning and all is clean and open.
Nothing anywhere.
__________________
Bert 
RV-9A ?Pearl?
Working on Instrument ticket
Donation Done for 2020
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04-25-2016, 11:45 AM
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Join Date: Jan 2005
Location: Sherwood, Oregon
Posts: 981
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Try this?
Any friends nearby flying the same setup, RV with 320/360/CSP? If so ask them to ride along and see what they say. Is it possible it's all normal?
Just thinkin'
Jerry
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04-25-2016, 12:49 PM
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Join Date: Sep 2012
Location: Prairieville, LA
Posts: 221
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Thanks Jerry
Yep been done. I did transition training in a 6A (360/CS) owned by
CFII friend. He then flew with me in 9A under the APP and was very
bothered by prop behavior. Nothing like the 6A prop. In 6.5 hrs in
6A never felt or heard anything like mine.
Next step is gather tools etc and do the pressure check on the
prop oil circuit per Lycoming.
My stomach already in knots.
__________________
Bert 
RV-9A ?Pearl?
Working on Instrument ticket
Donation Done for 2020
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04-26-2016, 06:41 AM
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Join Date: May 2005
Location: Florida
Posts: 774
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Bert,
I know how frustrating it is to not be able to nail down a problem. Keep in mind that it is MECHANICAL and there will be a solution somewhere. don't (if this is possible) let it keep you up at night and get your stomach acids churning. The positive side of this is that you will be an inspiration to all who read VAF when you post how you discovered and eventually cured your problem, (and you will). I read these posts daily because we are about to launch our 14 in the next month or so and hopefully we won't experience any of the myriad of problems I read about. Again I say, it is mechanical and not a health issue so don't make a health issue out of the problem. Feel free to ask any of us who have had an unexpected diagnosis and the fixes involved to the human aspect of flying. Keep the posts coming.
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04-26-2016, 01:26 PM
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Join Date: Dec 2009
Location: Montreal
Posts: 1,456
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It certainly does sound like inadequate flow, for some strange reason. It could be something as simple as vibration of the line at certain RPMs. I will be curious to see what it turns out to be. I am sure you will bottom it out eventually.
__________________
Scott Black
Old school simple VFR RV 4, O-320, wood prop, MGL iEfis Lite
VAF dues 2020
Instagram @sblack2154
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04-26-2016, 03:58 PM
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Join Date: Apr 2008
Location: Lake Havasu City AZ
Posts: 2,393
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Prop
You seem to be running out of possibilities. Even though you say you checked the hose I would replace it with a hose made by a reputable hose shop. It is possible you have a flaw in the hose that you missed on a visual inspection.
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