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07-06-2011, 10:31 AM
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Join Date: May 2005
Location: Canby, Oregon
Posts: 1,786
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Prop speed reduced with Alt.
My constant speed IO320 powered RV9A max speed is reduced with alt.
At takeoff (179 ft) FULL in on everything my RPM is 2720. By the time I reach 8000 ft and level off (still FULL in on all controls) I am only turning 2670.
Is this to be expected?
Should I adjust something?
I don't normally run at full RPM except takeoff, but I was doing some speed testing and noticed this.
Kent
__________________
Kent Byerley
RV9A N94KJ - IO320, CS, tipup
AFS 3500, TT AP, FLYING....
Canby, Or
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07-06-2011, 10:51 AM
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Join Date: Mar 2005
Location: Dallas area
Posts: 10,762
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One of two possibilities...
You're either running out of power. (Doubtful)
Or the fine pitch stop on your prop or is adjusted improperly.
__________________
Mel Asberry, DAR since the last century.
EAA Flight Advisor/Tech Counselor, Friend of the RV-1
Recipient of Tony Bingelis Award and Wright Brothers Master Pilot Award
USAF Vet, High School E-LSA Project Mentor.
RV-6 Flying since 1993 (sold)
<rvmel(at)icloud.com>
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07-06-2011, 11:37 AM
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Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,668
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Quote:
Originally Posted by Mel
You're either running out of power. (Doubtful)
Or the fine pitch stop on your prop or is adjusted improperly.
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If your fine pitch stop was misadjusted (had the blades at to much of an angle) you would not make 2720 RPM on TO.
I would try pointing the nose down a bit to gain a little airspeed when you at 8K ft, if the RPM comes up then you probably are running out of juice.
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Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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07-06-2011, 11:52 AM
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Join Date: Jan 2008
Location: Ashland, OR
Posts: 2,561
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somewhat normal
I find that as the engine oil warms up, the max RPM drops a little. On my WW 200RV prop, first takeoff of the day will generate 2680. If I'm shooting circuits, by the 3rd takeoff, I'm getting 2640 or so. Kevin Horton reported similar on his blog, so I think this is somewhat normal.
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Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet"
Hobbs 625
LS6-15/18W sailplane SOLD
bought my old LS6-A back!! 
VAF donation Jan 2020
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07-06-2011, 12:15 PM
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Join Date: Mar 2007
Location: Sonoma County
Posts: 3,821
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Quote:
Originally Posted by kentb
By the time I reach 8000 ft and level off (still FULL in on all controls) I am only turning 2670.
Should I adjust something?
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Yes, the mixture should be adjusted. The motor is running rich and causing a decrease in power. |
07-06-2011, 01:39 PM
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Join Date: May 2005
Location: Canby, Oregon
Posts: 1,786
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whoops.
Quote:
Originally Posted by gasman
Yes, the mixture should be adjusted. The motor is running rich and causing a decrease in power.
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Your right Gasman. I had pulled mixture to get 100 ROP.
Kent
__________________
Kent Byerley
RV9A N94KJ - IO320, CS, tipup
AFS 3500, TT AP, FLYING....
Canby, Or
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