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08-15-2016, 05:46 PM
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Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 2,247
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Quote:
Originally Posted by rvbuilder2002
And the other exception is density altitude.
This time of year the density altitude can easily be 3000-4000 ft higher than pressure altitude. Something to keep in mind as it will have an influence on engine power and propeller thrust.
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Scott, the PAP makes no mention of adjusting for DA when setting the pitch for the desired static RPM. Would it be a factor? I checked yesterday and, as you predicted, found my static RPM at full throttle was a bit low -- like 4700, if I recall correctly. The field elevation is 1050, but DA this time if year can be over 3000 on a hot day. Should I do the check & adjustment early or late when it's cooler, or does it matter?
__________________
Dale
Omaha, NE
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)
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08-15-2016, 08:46 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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The PAP check is to confirm that the pitch setting is in the ball park. It is not meant as an absolute for every one (though it will probably be fine for a lot of people that aren't interested in fussing with the pitch setting). Particularly for a first flight when most people new to the airplane have no idea what to be looking for.
RV-12 pilots may (and many do) make small adjustments from that value to tailor performance to fit how they fly the airplane. Some even do it seasonally if their local temps swing between extremes of hot and cold.
I.E., if someone flys out of primarily higher altitude airports in the mountains and isn't as concerned about all out cruise speed because the never venture very far (particularly into the flat lands) they will probably want a pitch setting that is a bit flatter than average, and vice versa for someone that flys mostly from low altitude airports in the flat lands parts of the country.
My comment about density altitude was meant to convey that even if you use in flight performance (like rpm value at WOT at 6500') if you simply use 6500 indicated (pressure) altitude, the result you get can be quite different between a cold winter day at that altitude and a hot summer day at that altitude.
__________________
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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08-17-2016, 07:47 PM
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Join Date: Jun 2009
Location: Dayton, OH
Posts: 838
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OK-- I've searched Van's on-line catalog Where
do I find tool-00002??
Wayne 120241
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08-17-2016, 09:30 PM
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Join Date: Jan 2016
Location: santa rosa CA
Posts: 90
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I called Vans and they sent me the tool, it was like $8 and they sent it quickly (if you're talking about the prop pitch tool that they sell).
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08-20-2016, 12:30 PM
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Join Date: Jan 2016
Location: santa rosa CA
Posts: 90
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After adjusting the pitch, I cannot describe to you just how much smoother my plane is running! What a huge difference.
Gained some performance too!
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08-20-2016, 07:58 PM
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Join Date: Jan 2011
Location: Clearwater, Florida
Posts: 398
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Quote:
Originally Posted by Chrysopelea
. . . "I remember I think.
4960 static on the ground, and I think 5640 flying WOT at 127 knots True Airspeed are the numbers I believe.
Again, smooth as silk, and no pitch movement after the lesson." . . .
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Quote:
Originally Posted by Chrysopelea
. . . "After adjusting the [prop] pitch, I cannot describe to you just how much smoother my plane is running! What a huge difference.
Gained some performance too!" . . .
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I think you've nailed it.
Besides a good carb synch and prop balance, trimming the ground adjustable propeller to 5600-5650 RPM, at wide open throttle setting and the desired average cruise altitude (DA) . . that is the key.
Glad it is where you want it now.
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08-20-2016, 11:12 PM
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Join Date: Jan 2016
Location: santa rosa CA
Posts: 90
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I feel like I nailed it as well.
From all the data I've gathered here, and the performance of the plane, and numbers all matching what others say is the "sweet spot'', plus, I got 127 TAS knots, so I'm really happy with the new blade settings.
Now if they'll just stay put!
I'm checking prop pitch after every flight as part of my post flight check.
On my last PRE-flight check, I noticed my coolant level was a little lower than normal. I marked the level on the expansion bottle.
After the flight, there were drips on the ground, and the level was 1/4" lower than my mark, so I knew i had a leak.
A very nice friend and I took the cowling off and quickly located the leak. The clamp for the tube exiting the head was Not placed just in front of the bulge in the metal tubing, it was too far forward and actually up in the bent area of the metal tube. Simply sliding the clamp back into it's proper position fixed the issue, and I also placed a regular hose clamp on the extra rubber behind the oem clamp for extra insurance. Not too tight so as to bite into the hosing, just enough to add some extra insurance.
Mechanic said this wasn't too rare of an occurance, and he'd seen it before. Total coolant loss was only a cup or 2 after an hour lesson.
This is I'm sure why a good pre-flight check is so important!
Plane's back together now and ready for my next lesson.
Last edited by Chrysopelea : 08-20-2016 at 11:15 PM.
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08-21-2016, 06:43 AM
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Join Date: Dec 2011
Location: Hackettstown, NJ
Posts: 459
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I posted on here somewhere else a recent failure of the rubber coolant line between the header tank and the overflow bottle - about 250 hours of use. Its going to happen with rubber hoses so the suggestion to do a good inspection every time the cowl is removed for oil changes is a good one. (unfortunately, you don't need to change the oil that often in a Rotax using MOGAS)
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08-21-2016, 09:48 AM
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Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 2,066
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Quote:
Originally Posted by Chrysopelea
I feel like I nailed it as well.
From all the data I've gathered here, and the performance of the plane, and numbers all matching what others say is the "sweet spot'', plus, I got 127 TAS knots, so I'm really happy with the new blade settings.
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That?s a very fast airplane.
Van?s performance numbers are
Top Speed 135 mph
Cruise (7500? @ 5500 rpm) 131 mph
Cruise (7500? @ 5000 rpm) 116 mph
Van?s numbers must be TAS because altitude is given. So it looks like the 12 tops out at 135 mph at 7500? WOT.
Your 127 knots TAS is 146 mph. Somehow you?re cruising speed is about 10 mph over top speed. Just say?n?.
__________________
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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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08-21-2016, 10:16 AM
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Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 2,247
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127 is fast. I'd want to run a GPS course to see how close the airspeed calibration is. I don't think it's impossible by any means, though.
I have some tweaking to do on mine, but it's not unusual to see 123 kt TAS at 5500-7500 MSL. I know there's a little more to be had with some more aerodynamic cleanup. Given the minor speed gains, I'm much more interested in cutting the fuel burn at 115 or 120 kt than I am in trying to wring out another couple knots of top speed. Those two goals just happen to coincide.
__________________
Dale
Omaha, NE
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)
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