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Prop Pitch Setting and Zeroing to Canopy Deck

Tacco

Well Known Member
The KAI says to calibrate your level to the canopy deck then measure the prop pitch. I did this and got it set to 71.4 as recommended.

Today after a test flight I was chasing down a slight vibration. I measured the prop pitch at 67.1 on both blades.

Then I remembered that I used to righ side of the canopy deck to set the blades, today I used the left side.

Measured the canopy deck sides and sure enough there is a 4 degree difference!

Don?t know what to make of this, just putting it out there. I?m thinking the important thing is that the blades are within .1 degree of each other and that ?71.4? is a relative thing ?
 
perhaps the gain in weight makes the difference? Fuel on the right side, you added to it...? Just guessing.
 
Maybe you level is of by 2?

Steve

Rotate your level 180° ( the same end of the level forward )

Maybe you level is off by 2°

if so recalibrate your level

It is hard to believe longerons are 4° different. Your readings may be different if you are parked on a large cross slope.

The prop pitch should be 71.4° from level or 18.6° from plumb when the longerons level ( 18.6° from plane of rotation )

You must add or subtract from the angle if the longerons are not level.

Joe Dallas




The KAI says to calibrate your level to the canopy deck then measure the prop pitch. I did this and got it set to 71.4 as recommended.

Today after a test flight I was chasing down a slight vibration. I measured the prop pitch at 67.1 on both blades.

Then I remembered that I used to righ side of the canopy deck to set the blades, today I used the left side.

Measured the canopy deck sides and sure enough there is a 4 degree difference!

Don’t know what to make of this, just putting it out there. I’m thinking the important thing is that the blades are within .1 degree of each other and that “71.4” is a relative thing ?
 
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Measured the canopy deck sides and sure enough there is a 4 degree difference!

This isn't possible. The RV-12 is CNC punched and self-jigging. The holes line up and the airframe is true and straight. There can’t be anywhere near 4° mismatch in the longerons otherwise the canopy would never close properly. My guess is your technique with digital level needs improvement.

Follow instructions on KAI PAGE 47-07 exactly and use tools as described. Technique and repeatability are key to good outcome. When blades are set correctly you will achieve very close to 5150 rpm in initial climb with full power. This will translate to near 115 knots @ 5500 rpm and throttle will be pulled back about 1” from wide open throttle at this cruise setting. 71.4° is starting point. Set blade pitch to achieve above results.

If you are still having difficulty, I can make a more detailed step-by-step set of instructions for setting blade pitch.
 
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Ok here is what I think is going on...

My level is a little too long to position exactly fore and aft due to rivet interference on the canopy deck. Therefore, I angle it slightly to fit aside the rivet line and sit flat. When I bent the longerons, it is possible that they are out of plane laterally, e.i. twisted. I?m pretty sure the outside edge follows the top edge of the fuselage skin, not sure the inside edge does.

On my way to the hanger today to check this out and will let you know.
 
I have found that contrary to Vans procedure on zeroing first on longerons, that for my plane and procedure it does not then reference to the 71.4 requested and could allow you to get a degree off. After searching for the right pitch, to be repeatable I found it best to do all based upon true level. Probably repitched flat and coarse a half dozen times and am not back to 71.4 for all around performance.
 
Joe had it right. The level is off. If I set it on the deck and zero it, then rotate it 180, it measures 4.4 degrees. Weird.

Lesson learned, important to maintain level?s orientation when taking the level from the deck rail to the prop. Just as the KIA mentions.
 
Steve

I think your you aircraft may have a 2.2° slope on the deck rail

You need to calibrate on a known level surface.

There should be instructions on how to calibrate your level.

Joe



Joe had it right. The level is off. If I set it on the deck and zero it, then rotate it 180, it measures 4.4 degrees. Weird.

Lesson learned, important to maintain level’s orientation when taking the level from the deck rail to the prop. Just as the KIA mentions.
 
My level is a little too long to position exactly fore and aft due to rivet interference on the canopy deck. Therefore, I angle it slightly to fit aside the rivet line and sit flat.

Steve -

To make the rivets on the canopy deck a non-factor, I place a thick piece of flat aluminum directly on the canopy deck then set my level on the flat aluminum. This allows my level to clear the aforementioned rivet heads.

Happy flying,
 
Steve

I think your you aircraft may have a 2.2? slope on the deck rail

You need to calibrate on a known level surface.

There should be instructions on how to calibrate your level.

Joe

Actually, no. You want to zero the level on the longeron. Use the copilot side because that is the side of the prop you will measure prop blade. The pitch angle is the difference of blade angle as compared to reference angle of longeron. Airplane need not be level...
 
Yes Jim your statement is correct

I was trying to clear up the 4.4° difference of his longerons and keeping the level with the proper end not to add or subtract from the angle.

When you zero the level on the longeron and rotate the level 180° the true angle of the longeron is 1/2 the angle shown.

If you properly calibrate the level and rotate the level the angle should read the same.

Then you can see that the longerons are not 4.4° different

Using the pilot side is ok however the side closest to the true line of thrust will get you to the most accurate angle.

The target of 71.4° is not 100% correct if the longerons are not in perfectly in line with the line of thrust.

The 71.4 is close enough as a starting point and may need to be changed for the best rate of clime or for the cruse speed.

My View

Joe Dallas

Actually, no. You want to zero the level on the longeron. Use the copilot side because that is the side of the prop you will measure prop blade. The pitch angle is the difference of blade angle as compared to reference angle of longeron. Airplane need not be level...
 
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Ok guys, here?s the deal. Bad level. It has an orientation bias in it that can?t be calibrated out. It?s ok to use if you change orientation but if you?re unaware, it can be confusing.

My canopy decks are within a decimal place of each other. Fortunately I did not change the orientation when I initially set the prop and it?s spot on.

I bought an ?AngleCube? for use going forward and highly recommend it. Works really well with the Van?s prop tool. Advertised accuracy is .2 degrees but relative measurements are probably more accurate.
 
Going to have to go through this on my 2012... I'm seeing 4900 rpm static at full throttle and brakes on at 1000 ASL.

What should my rpms be at full throttle? Prop seems to be pitched for cruise, seems much slower to get up to speed to rotate and take off, compared to my friends N836BL.
 
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You will want to pitch prop such that full throttle initial climb (1000MSL) is 5100-5150 RPM. This should allow going over red line RPM in cruise with throttle pushed almost all the way in. With this pitch setting you will see 900/1000 FPM climb and ~115 KIAS cruise. Throttle position at 5500 RPM cruise is about 1-1/4" out from panel. Engine is very happy when pitched properly...
 
Jim is correct, my numbers match his, about 5100-5150 climb out and about 5650 WOT level with a 71.4 pitch...5500 is 115kts
 
I'm flying solo a lot now with COVID. RPM in climb are similar solo/dual. Climb rate reduces with added weight.
 
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