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03-08-2014, 03:36 PM
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Join Date: Mar 2011
Location: Scranton Pa
Posts: 34
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What's limiting my RPM?
I have a new Lycoming 0-320, Catto three bladed prop (specified for my 9a with 160 hp engine) one Slick Mag and one P_Mag. The engine reaches a maximum of 2410 rpm full rich while burning 11gph. TAS is less than 140 knots without pants and fairings. (About 20 knots less than I'd expect)... I've checked throttle and mixture linkages for full range of travel. I plan to call Catto to ask about the pitch of the propeller but is there anything else I should be looking at?
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03-08-2014, 03:55 PM
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Join Date: Jan 2005
Location: Round Rock, TX
Posts: 3,778
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You will be very surprised what correctly installed fairing and pants will do.  What Gen prop do you have and what is the pitch?
__________________
Reiley
Retired N622DR - Serial #V7A1467
VAF# 671
Repeat Offender / Race 007
Friend of the RV-1
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03-08-2014, 04:16 PM
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Join Date: Sep 2010
Location: Charlotte NC
Posts: 1,166
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Between pants and fairings and leaning to best power I suspect your numbers will improve quite a bit.
George
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03-08-2014, 04:19 PM
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Join Date: Jun 2005
Location: Cedar Park, TX
Posts: 3,152
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Sounds just about right to me. Please don't bother Craig before you are in the final configuration that you are going to fly with, including pants and fairings.
__________________
Scott Card
CQ Headset by Card Machine Works
CMW E-Lift
RV-9A N4822C flying 2200+hrs. / Cedar Park, TX
RV8 Building - fuselage / showplanes canopy (Done!)
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03-08-2014, 04:43 PM
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Join Date: Mar 2011
Location: Scranton Pa
Posts: 34
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Leaning
Adjusting the mixture yields no higher rpm. Would you expect the addition of pants and fairings to bring rpm up by 300 - 400?
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03-08-2014, 04:49 PM
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Senior Curmudgeon
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,408
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What Scott said.
Quote:
Originally Posted by scard
Please don't bother Craig before you are in the final configuration that you are going to fly with, including pants and fairings.
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Quite right, get it all finished before looking at changing the prop.
__________________
Mike Starkey
VAF 909
Rv-10, N210LM.
Flying as of 12/4/2010 
Phase 1 done, 2/4/2011
Sold after 240+ wonderful hours of flight.
"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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03-08-2014, 05:03 PM
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Join Date: Aug 2007
Location: Wichita Falls, TX
Posts: 2,182
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Double check the ignition timing on both mags. Also check your tach accuracy against a handheld digital tach.
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Neal Howard
Airplaneless once again...
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03-08-2014, 07:30 PM
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Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,271
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Check your static is correct by running a GPS box and copare the TAS indicated to TAS from the GPS box. You could have a big error.
If your RPM is definitely right you might have a dog of a prop. I wonder about Jamie Lee's RV7A, it is slow too with a 3 blade Cato.
Others get a good result? So who knows. I have had timber laminate props that measure the same for pitch on a jig, yet one to the other are daylight and dark. We could never work out why.
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______________________________
David Brown
DYNON Authorised Dealer and Installer
The two best investments you can make, by any financial test, an EMS and APS!
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03-08-2014, 07:40 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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The rule of thumb is 10 knots for the gear leg fairings and another five for the wheel pants.
Fairings and other tweeks may add another five.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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03-08-2014, 08:26 PM
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Join Date: Sep 2006
Location: Townsend, Montana
Posts: 3,179
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Quote:
Originally Posted by jimevison
Would you expect the addition of pants and fairings to bring rpm up by 300 - 400?
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Quite possibly. Your prop is designed for a 160hp RV9. With no fairings or pants you have significantly more drag. ie...you're not flying a RV-9 profile.
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Retired Dam guy. Life is good.
Brian, N155BKsold but bought back.
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