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Ideas on pitching a prop

NinerBikes

Well Known Member
I currently have my prop pitch set at 71.4 degrees, the Factory Van's setting, and I see about 4900 rpm static, and about 4975 on take off at 1000 ASL at full 1320 gross, at 75 kts, Vy, and a 650-700 fpm climb rate at 28C Thursday evening.

I still feel my prop is over pitched. I'd like to see around 5150 to 5175 at 75 kt's and closer to 900 fpm.

I guess I am trying to see how much pitch needs to be taken out of the adjustable props to see my 5150 rpms, from the 71.4 degree setting that is there? Or should I call Sensenich for recommendations?

How much rpms might you gain with a change in pitch from 71.4 degrees to a more shallow bite of air like 72.0 degrees, at climbing speeds of 75 kts 1000 feet above sea level?
 
I don't have my aircraft logbooks with me so this is from memory. At my last annual condition inspection, I set it to 71.4. I was only getting about 4900 on the takeoff roll. I then set the pitch to either 71.9 or 72.0, I don't remember which and not I get between 5150 and 5200 on the takeoff roll.
 
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RPMs

I had my prop pitched shallow at first, was getting around 5100 RPM static and was too lazy to redo it.
My experience was that it was too easy to over-speed the engine in cruise If not paying attention, especially with the original throttle cable and springs that would creep forward on you.
 
I think I am just going to leave it alone for now, get more samples on cooler and warmer days, and see if cooler days increase my rate of climb, and or climb out at 80 kts instead.

AP buddy also suggests we look inside the muffler for displaced or broken baffles, from the old Cessna days, but I think at 196 Hrs, kind of unlikely, but worth a look see inside. I haven't heard of any mufflers dying yet on RV-12's here.

Engine just feels down on power compared to Bob's 2015, and he sees 5175 RPM at 75 kts climb out, same airport, with both of us in it. Carbs were synched by an AP from Lockwood, motor feels smooth, no vibrations until you get down to about 3800 -3900, very light and in a narrow range.

Also cleaned, washed, air dried and re-oiled the air filters. Surprised how much dirt came out of them in the wash. Just trying to eliminate as many variables as possible.
 
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OK,

Repitched prop this morning with Van's tool. 2012 build RV-12 with Sesenich prop.

Leveled plane to 0.0 on the Longeron with digital level.

We inserted a 1/4" thick x 1/4" x 2" strip of black high density foam with adhesive on back, on the inside of the Van's prop pitch tool, which greatly stabilized the hold of the tool on the propeller blade, and made the line up of the black and white in the sight hole much, much more stable. it now keeps the little tang stop on the bottom side of the device pressed firmly against the bottom side of the propeller.

We also add a piece of white tape with a straight line of ink at the shank of the prop, near the slot in the hub, as a witness index mark to see how much has been added or subtracted, pitch wise.

Changed the pitch from 71.4 to 72.0, again, this is on MY plane. Temps were 25C elevation about 980 ft.

Static rpms were 5020 rpms at full throttle

75 kt climb out showed about 4980 to 5000 rpm.

Full throttle at 3500 ft, with a density altitude at about 5100 ft showing, straight and level, showed 5720 rpms.

Plane is 775, 215# pilot and 12 gallons of fuel were in the tank. Fully dressed with wheel pants and fuselage, step , and wheel pant fairings.

https://youtu.be/dCcQWGH88Jc

This was the sound of the engine RPM's when I bought it in SC, note the very shallow take off angle from near sea level in SC. About 4800 rpm, with a cruise climb type of take off, very shallow. https://youtu.be/SMPIuDBEcdQ

RAW data logs. https://flightaware.com/live/flight/N72DJ/history/20200720/1721Z/KWHP/KWHP/tracklog

Flight. https://flightaware.com/live/flight/N72DJ/history/20200720/1721Z/KWHP/KWHP

Will take a month or more of lessons with it this way, probably try to solo and then see how it does with just me in it.

Then possibly re pitch, as necessary, as the climb rate at 75 kts still feels a bit anemic. Want to wait a bit for some cooler weather and lower temperatures to test it out, instead of the heat and hmidity of July and August.

Control wise, it's a very steady, stable and great flying plane. Just feels, still, a little anemic on the climb rates in FPM and in RPM's. Got to get over that torque hump and into the HP portion of the power band. 5150 to 5175 seems to be the sweet spot with full throttle climbs at 75 kts.
 
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Not that this helps or maybe it does.
2018 Rv12.
my Numbers.
71.4 pitch,2 people ,full tank,i get 900 FPM at 3000 ft elev in 75 degree weather..by myself I can maintain 1150-1200 FPM with 10 Gallons of fuel.5080 static,around 5150 on climb @75knts.
I have wheel pants,and all usual legal speed mods.
Tried a 72 pitch and had too much RPM,so went back to 71.4
 
Not that this helps or maybe it does.
2018 Rv12.
my Numbers.
71.4 pitch,2 people ,full tank,i get 900 FPM at 3000 ft elev in 75 degree weather..by myself I can maintain 1150-1200 FPM with 10 Gallons of fuel.5080 static,around 5150 on climb @75knts.
I have wheel pants,and all usual legal speed mods.
Tried a 72 pitch and had too much RPM,so went back to 71.4

I am beginning to think that with my S/N being 120212, and finished in 2012, that perhaps Sensenich made some improvements or modifications to the later production props in the pitch, such that 71.4 degrees with the pitch device Van's supplied on later models isn't accurate on the earlier versions of the props from 2008 -2012 production, though I can't confirm it. I just know my prop doesn't do well with a pitch setting of 71.4 like the newer RV-12's do.

Either that, or I somehow have a very anemic 912ULS Rotax, motor. How the prop behaves at cruise, at elevations above 7500 ft, once you get up there, is great. I won't be the least bit surprised if the Van's measuring device ends up needing 72.6 to 73.0 degrees to get the engine making the rpm's and climb rate I want at 75 kt's Vy on take off from 980 ft. Plane should make over 900 ft minute with my instructor only weighing 120 # and well under gross with near a half tank of fuel.

I guess I am looking for input from people with early serial number builds or that bought the prop before 2013 or 2014 or so.
 
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I have a 2010 RV-12, SN 120230 so the same prop as you. I've played with prop pitch quite a bit, from climb-like-a-banshee to cruise-like-a-rocket. Don't be afraid to experiment, but there is no single setting that will make you happy with both climb and cruise. That's the nature of a fixed pitch prop.

There are *many* other threads on this subject, I suggest searching for and reading them. Roger Lee has rules of thumb for propping a Rotax 912 that lots of people seem to follow:
https://vansairforce.com/community/showpost.php?p=876817&postcount=3
 
The angle settings quoted are misleading because when you get close to the sweet spot you get down to tenths of a degree adjustment. It is easy to miss “level” by tenths of a degree. I adjust mine by tenths of an inch from as found and don’t worry about the absolute value of the blade angle. Big thing is to match the left and right blade angle each adjustment.
 
Latest adjustment today was to adjust the pitch to 72.8, adding 0.8 degrees less "bite". Temp was 26 C, Altimeter 29.95.

RPM's at 75 kt climb rate with 14 gallons of fuel and pilot at 215 was at 5150 rpm. At 2500 ft elevation level flight and 5200 rpm, manifold pressure was 24.7 .

I consider that a good bit of progress. Will fly it for a bit more before considering any more fine tuning.

A little magnetic square level, maybe 3' x 3" that is good down to 0.05 degrees was bought for $23 on Amazon, as shown by Scott in another thread. It fits and sticks perfectly on the steel "T" prop pitch setting device that Van's sells, works a charm. I measured the old setting then added 0.80 degrees pitch to that setting, and called it good, so my climb rate should be improving, a fair amount.

When I bought the plane, it was at 4800 rpm at a 75 kt climb rate, and a very anemic FPM climb rate.
 
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My numbers;

1320#
4200' MSL
75 KTS
5090 RPM
25.8 INHG
650 fpm climb
83 f OAT
with wheel fairings

Opinions?
 
At 4200 ft, I'd say your prop is pitched right where I'd want it, or very close to it. The 83F OAT is the kicker, was that at 4200 ft elev? It's 28C, it's bumping your density altitude up to about 5800 ft.

Your climb rate is good in FPM, at that temp, which is what I was wanting to improve on my plane. It should be even better, once things start cooling off, or if you fly very early in the day.
 
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When I bought my plane, once at it's new home, at 1020 ft elevation, at 75 kts, climb rate was low at 500 fpm @ 1320#, and engine rpms were at 4800 rpm.

Adjusting to factory specs at 71.4 improved things a bit, as did 72.0, and so my total known added to factory spec on this 2012 is 1.4 degrees, pitched now at 72.8.

I will fly it for a while longer and see how it does for rpms for climb out and climb rate, on various weather conditions, as well as climb rates in fpm.

I'm either almost already there, or very close to where I'd like it to be.
 
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I have my prop pitched at 72.0. I am wondering how many RV-12 owners have pitched their props differently than the recommended 71.4?
 
My next "test" will probably be to run the tank down, land with about 3 to 4 gallons left, and fill up with some 100LL to see if that affects the RPMS and HP the motor makes, compared to the Costco 91 octane Mogas all the time.
 
It won’t help it to make more power,maybe less.

Correct... Octane does not make power. 100LL may even have slower flame propagation. As long as engine does not exhibit detonation (knock) everything is Jake. You absolutely do not want detonation in an airplane engine. Airplane engines are very likely built and will self-destroy with detonation. Spark advance is set pretty conservative to help prevent this problem.
 
Flew at about 6000 ft today, manifold pressure looks good, 23.0 inches, RPM's look good at full throttle, about 5650 in level flight. TAS indicated at 120 kt's where it should be.

Got a 9:20 am start, air temps probably 75F, at 1320# and climb rate is now at 750 -800 FPM. RPM's dropped a bit at full gross weight on climb out, about 50 or so.


Getting there. Will probably try to remove another 0.4- 0.5 degrees. This engine needs the 5200 rpm's to get the good factory specified 900 fpm climb rates.

Sampled the Costco fuel purchase yesterday for Ethanol. 0%, none added, in the 91 Octane stuff. So that was good news, too.
 
After reading the post from Roger Lee that was referenced in this thread, I did a WOT test today. At 2,000 MSL it was 5,700 rpm. At both 3,500 and 4,500 msl it was 5,650 rpm. This is in the area he suggest.

I also get between 5,180 and 5,200 on the initial takeoff run. So my prop is set at 72.0 and it appears to me it is set about right.
 
After reading the post from Roger Lee that was referenced in this thread, I did a WOT test today. At 2,000 MSL it was 5,700 rpm. At both 3,500 and 4,500 msl it was 5,650 rpm. This is in the area he suggest.

I also get between 5,180 and 5,200 on the initial takeoff run. So my prop is set at 72.0 and it appears to me it is set about right.

I'd like to see 5150 to 5200 rpm once at a Vy 75 kt take off slightly above the runway. I usually rotate at 55kt, level off a bit to slowly get out of ground effect. get to 65-70 kts 20 ft above the runway, then ease back on the stick to a steady 75 kt climb rate. You can feel the acceleration quite well between about 60 kts and 75 kt where the prop really starts to bite and stops stalling, there will be a brief rpm drop when it does so with enough airspeed.

Of course, I never get to see this when PIC, only when I am in the passenger seat. Too much more important stuff going on, on take off.

The performance of my plane at takeoff has transformed the whole plane, from takeoff to cruise elevation. What was once anemic feels pretty healthy right now, with the prop pitch adjustments. No longer does it climb like a Cessna 172. My fuel MPG might be a little worse, or a little better, too soon to tell, yet.
 
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