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04-27-2018, 11:23 AM
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Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 2,065
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Refining Prop Pitch...
I?m trying to find optimum prop pitch for my RV-12/912 ULS/320TT. Most of my flying is below 4000 MSL and airport is 870 MSL grass runway. If I?m going somewhere I?ll flight plan ~ 7000 MSL.
I?ve been adding a couple tenth?s degree pitch and today I have performance listed in table below with one person aboard and half fuel.
Engine is running smooth and seems happy. Temps are all good.
Question - Do you think 4920 rpm is too slow for full power climb?
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__________________
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Jim Stricker
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 622 
LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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04-27-2018, 01:11 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Quote:
Originally Posted by Piper J3
Question - Do you think 4920 rpm is too slow for full power climb?
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I do.
You have likely crossed over to the coarse side of ideal, where additional pitch wont really give you any more speed but will degrade climb.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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04-27-2018, 02:23 PM
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Join Date: Jan 2011
Location: Clearwater, Florida
Posts: 398
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For overall best performance (climb and cruise) the best RPM is 5600-5650, set at wide open throttle (WOT), flown straight and level, at your typical cruise altitude. Here in Florida, that is 3500 ft MSL for me.
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04-27-2018, 04:23 PM
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Join Date: Apr 2007
Location: Madison, AL
Posts: 338
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I agree, way too coarse. I wasted a lot of time way over pitching mine but at that climb RPM I was seeing 128 knots at 5500 with Dynon Betty yelling at me for going too fast. Flattened a lot to about .2 coarser than Van recommends getting about 5080 at 75 knots but I climb after initial about 85 closer to 5200. My SNF trip at 3500' solo I was seeing 120 TAS at around 5360 at 25.4 MP. Hot weather and time will tell on climb performance but for now it appears I gained about 5 knots in cruise for my long cross countries from my initial pitch setting.
At this pitch I'm also getting 5600- 5700 WOT at around 3500', goes to redline above.
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Scott- 2020 donation
New RV-7A N579RV, only 80 hours now without 2020 fly-in destinations
Built RV-12, 328 hours-sold, purchased RV-12 sold, Built RV-9A, 536 hours-sold, Not completed RV-7 sold, Built Kitfox sold
Last edited by scottmillhouse : 04-28-2018 at 09:30 AM.
Reason: added text
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04-27-2018, 05:38 PM
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Join Date: Sep 2006
Location: Windsor, California
Posts: 924
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Over-pitching your prop has the potential to damage your engine. See Figure 1 of ROTAX's SL-912-016R1 at:
https://legacy.rotaxowner.com/si_tb_...912-016-r1.pdf
I use the numbers Driftdown noted above and am happy with the balanced climb/cruise performance.
__________________
David Heal - Windsor, CA (near Santa Rosa)
EAA #23982 (circa 1965) - EAA Technical Counselor and Flight Advisor; CFI - A&I
RV-12 E-LSA #120496 (SV w/ AP and ADS-B 2020) - N124DH flying since March 2014 - 940+ hours (as of September 2020)! 
V AF donation through June 2021.
Last edited by DHeal : 04-27-2018 at 06:01 PM.
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04-27-2018, 10:35 PM
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Join Date: Jul 2009
Location: Coeur d'Alene, ID/Casa Grande, AZ
Posts: 654
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I?ve played around both over and undered pitched....finding Van?s recommended pitch of 71.4 to be dead on for overall performance.
Finding a good digital level was a trip, but once I got one. I can dial in both blades to within .1 degree of each other.
__________________
Ric Dickison
307 (CAB) Phantom
Search and Destroy (Can Tho RVN)
Distinguished Flying Cross Society Member
CH-47 & UH-1H "Driver"
Rotax 9 Series Service IRMT
RV-12 Kit#729 "N312RD" is now a full functioning fun machine!! Thanks Van for fulfilling my dream😎
2018 Dues Paid
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04-27-2018, 11:13 PM
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Join Date: Jan 2011
Location: Clearwater, Florida
Posts: 398
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Quote:
Originally Posted by Phantom30
I?ve played around both over and undered pitched....finding Van?s recommended pitch of 71.4 to be dead on for overall performance.
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Give us some performance numbers.
During straight and level flight, what is the maximum achievable engine RPM, when throttle is wide open?
At that maximum RPM, what is your indicated airspeed?
During the takeoff run, at full throttle, what is your RPM at rotation?
During climbout, at that RPM, what is the climb rate (and airplane weight)?
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04-28-2018, 06:35 PM
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Join Date: Jul 2009
Location: Coeur d'Alene, ID/Casa Grande, AZ
Posts: 654
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Quote:
Originally Posted by Driftdown
Give us some performance numbers.
During straight and level flight, what is the maximum achievable engine RPM, when throttle is wide open?
At that maximum RPM, what is your indicated airspeed?
During the takeoff run, at full throttle, what is your RPM at rotation?
During climbout, at that RPM, what is the climb rate (and airplane weight)?
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Will give info in a few days...as i?m On my way down from Idaho to get plane in Phoenix.
__________________
Ric Dickison
307 (CAB) Phantom
Search and Destroy (Can Tho RVN)
Distinguished Flying Cross Society Member
CH-47 & UH-1H "Driver"
Rotax 9 Series Service IRMT
RV-12 Kit#729 "N312RD" is now a full functioning fun machine!! Thanks Van for fulfilling my dream😎
2018 Dues Paid
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04-29-2018, 05:15 AM
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Join Date: May 2010
Location: Spring Hill Fl
Posts: 734
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Best digital leval
Ric
I would like to know what digital level you used to get them that close.
Thanks
Joe Dallas
Quote:
Originally Posted by Phantom30
I?ve played around both over and undered pitched....finding Van?s recommended pitch of 71.4 to be dead on for overall performance.
Finding a good digital level was a trip, but once I got one. I can dial in both blades to within .1 degree of each other.
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04-29-2018, 06:59 AM
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Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 2,247
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Quote:
Originally Posted by joedallas
I would like to know what digital level you used to get them that close.
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I bought this one ( https://www.amazon.com/gp/product/B006JR8XBG). It claims 0.05 degrees resolution with +/- 0.2? accuracy. Needless to say I was skeptical and ready to return it.
What I have found is that, while I can't speak to its absolute accuracy in every situation, it is dead on at 0 and 90, at least as close as I can test it. More importantly to me, its measurements are perfectly repeatable. The same angle will measure exactly the same, every time.
__________________
Dale
Omaha, NE
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)
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