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Check your CS prop “low pitch” stops

We just performed this test on our 14. Took 2.25 turns in on fine pitch stop for our Hartzell CS prop to get below 2700 static. This is with an IO-390-EXP. I suspect Hartzell is setting these props up for 200HP, and the additional power needs more pitch.
 
George Costigan said:
I have been flying for a few years (RV-10 with a Hartzell Prop) and I have an RPM of 2580 at full power. When flying at full power and I adjust the Governor it takes some movement before there is a decrease in RPM - it is not immediate. Because of that I thought it was not Governor limited so I adjusted the low pitch stop by 1/2 of a turn with no change on a ground run. My next step is to adjust the Governor and leave the low pitch stop where it is for the moment and once I am able to increase RPM then cycle back to the low pitch stop adjustment. Does this make sense?
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So your static RPM is 2580.. that’s ok, but you will get a little better acceleration at 2600 to 2650 static. The next question I have, are you able to hit 2700 rpm in climb? If not, then your governor needs to be raised. (You do have 1/8 to 1/4 inch before the knob hits the panel, right? You want the engine controls to fully hit their full range before they hit the panel)
I find that a lot of pilots or mechanics try to compensate for the overspeed surge by setting a lower governor setting to anticipate the surge, but that just makes the whole problem worse!
 
georgemohr said:
We just performed this test on our 14. Took 2.25 turns in on fine pitch stop for our Hartzell CS prop to get below 2700 static. This is with an IO-390-EXP. I suspect Hartzell is setting these props up for 200HP, and the additional power needs more pitch.
Click to expand...
Yup.. I find it takes 2 and 1/3 turn to get it about right. Did you fly it yet? It’ll probably get to 2700 just about the time you lift off, and will glide better when you pull to idle..
 
I watched (and summarized for myself, list is below) Vic's video. My question is why does the Governor screw need to be backed out before adjusting the Propellor low pitch angle? It seems that if the target is 2,650-2,700 when adjusting the Propellor low pitch angle, that it can be made without making any changes to the Governor screw. Am I missing something?

Check Low Pitch Blade Stop:
Run to full throttle (flaps up and stick full back)
Move propellor control back, IF immediately decrease in RPM indicates governor is controlling max RPM and an adjustment is required

Adjust Low Pitch Blade Stop:
Cut safety wire on governor adjustment screw
Mark location of governor adjustment screw
Loosen governor adjustment screw lock nut
Back out governor adjustment screw to ensure governor isn't controlling the propellor
To set propellor low pitch blade angle:
Loosen Low Pitch Stop Jam Nut (clockwise to loosen)
Felt pin to mark starting location on hub and hex Low Pitch Stop thread
Make minor adjustment (each turn (IN) of the Low Pitch Stop thread is a 200RPM decrease)
Tighten Low Pitch Stop Jam Nut
Test run engine at full power
Repeat until full power produces 2,650 to 2,700 RPM

Adjust Governor Stop:
When breaking ground on take off should see 2,690 to 2,700 RPM
Loosen governor adjustment screw lock nut
Adjust governor adjustment screw
Tighten governor adjustment screw lock nut
Safety wire governor adjustment screw
Repeat 1-4 until 2,690 to 2,700 RPM is seen when breaking ground on take off)
 
You basically take the governor out of the loop. You want to make sure that the low pitch stop is adjusting your blade pitch so that at full power the prop "consumes" all the power without overspeeding. If you don´t back off the governor adjustment then it could be that the governor is doing it´s thing and push the blades off the low pitch stop at high power and so limits the RPM. The RPM surge is happening when the engine accepts power faster than the governor is reacting. The governor should take over during acceleration (only) on takeoff roll, now the angle of attack on the blades would decrease due to forward speed and so unloads the prop - now the governor is increasing blade pitch to absorb the power and give it a better bite.
 
As SuperCubDriver said, you take the controller out of the loop. But if you know your static RPM is already too high ( >= 2700 for most engines), then you can skip that step and go right to the fine pitch stop adjustment.
 
George Costigan said:
I have been flying for a few years (RV-10 with a Hartzell Prop) and I have an RPM of 2580 at full power. When flying at full power and I adjust the Governor it takes some movement before there is a decrease in RPM - it is not immediate. Because of that I thought it was not Governor limited so I adjusted the low pitch stop by 1/2 of a turn with no change on a ground run. My next step is to adjust the Governor and leave the low pitch stop where it is for the moment and once I am able to increase RPM then cycle back to the low pitch stop adjustment. Does this make sense?
Click to expand...
Since governor adjustments should be tested in flight, I used another method. Before doing run up on ground to full throttle, loosen the jam nut of the governor just enough to allow you to turn the stop set screw out. (maybe 1/4 turn of jam nut). Then back out governor stop several turns. Enough to know for sure your governor is no longer slowing the RPM's down.

After that, do your ground run up at full throttle. Adjust the low pitch stop as necessary to get to 2650 RPM. Once that is achieved, THEN run the governor stop screw back down to the jam nut (this is where it started out) and tighten the jam nut. You will be VERY close to initial governor stop settings. Then go fly to test how close to 2,700 RPM you are getting. Adjust the set screw as needed. BTW, one 360* turn on governor set screw will equate to about 30 RPM's. It took me two test flights. 1st one showed governor was limiting RPM's at 2610 RPM. Turned set screw 3 full turns and re-tested in another flight. It was a perfect 2,700 RPM's on 2nd flight.
 
georgemohr said:
As SuperCubDriver said, you take the controller out of the loop. But if you know your static RPM is already too high ( >= 2700 for most engines), then you can skip that step and go right to the fine pitch stop adjustment.
Click to expand...
Thanks, that is what I was thinking too.
 
I followed Vic’s procedures:

“Check Low Pitch Blade Stop:
Run to full throttle (flaps up and stick full back)
Move propellor control back, IF immediately decrease in RPM indicates governor is controlling max RPM and an adjustment is required”

My static was 2650. It took a couple of full turns of the governor control before any drop in RPM.

I assumed my governor was not limiting my prop per this instruction. Is this an incorrect assumption?
 
I wrote directions on how to to this last year when I adjusted mine. Let me know how these look.

PROPELLER GOVERNOR SETUP


  • Rotate the gov bezel to achieve full cable travel
  • Do a static ground run and adjust low angle stop to achieve a max RPM of 2550-2650
  • Fly the plane, initially taking off at less than max power to prevent overspeed. Check for max RPM on climb out, in cruise, and in a dive. If RPM exceeds 2700, adjust cockpit lever to hold 2700 and leave it there until on the ground.
  • Turn the low angle stop clockwise and keep testing until you can get 2700 max RPM in flight, and no more.
  • Adjust low angle stop to achieve the desired static RPM at takeoff, goal is to hit 2700 RPM as the tail lifts.
  • The governor arm throw may now need to be fine tuned to keep from slightly over-speeding. Fly the plane, and while in cruise adjust the lever to hit 2700 RPM and leave it there until on the ground. Now adjust the governor arm stop screw to match the prop lever position at the in-flight 2700 position.
  • Once adjusted, safety wire all bolts
 
I backed off the Governor Screw one turn and did a full power ground run and still am limited to 2580 RPM, I have previously turned the low pitch adjust a total of 3/4 of a turn without any change. Can the low pitch be that far off and I need to turn it more? Is there a limit before backing off will cause a problem? I tried to call Hartzell to get some guidance but it is after business hours.
 
vic syracuse said:
I see so many airplanes that haven’t had the pitch stops adjusted properly. I know of one RV that overspeed to 3000 rpm’s on the initial flight because they did not set the pitch stops. I even mentioned it in my webinars this past week. Here’s a link to a video I made which should help you:


It’s also on page 113 in the Maintenance Handbook.



Vic
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Vic, I bought an RV-9A some time ago with a CS prop. I’ve never had any issues with RPM (fortunately), but also never knew about the process of setting the low pitch limits. I just watched your video…it was very helpful. Many thanks for the continuing education for RV owners!
 
Is engine monitor data useful for evaluating the prop adjustment? Looking at the EDM data which is captured in 4 fractions of a second, I see the prop increase to above 2700 very quickly for a second then settles down to 2650 for the remainder of the ground roll. The aircraft is a -9A with a O-360, Hartzell prop and MT governor. Here is what the RPM graph looks like with 3 takeoffs and landings around the pattern.

2024-04-19 11_49_49-stream_0416_2055.csv - Excel.png
 
dnickerson46 said:
Is engine monitor data useful for evaluating the prop adjustment? Looking at the EDM data which is captured in 4 fractions of a second, I see the prop increase to above 2700 very quickly for a second then settles down to 2650 for the remainder of the ground roll. The aircraft is a -9A with a O-360, Hartzell prop and MT governor. Here is what the RPM graph looks like with 3 takeoffs and landings around the pattern.

View attachment 61016
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Yes, it can be useful, though you'll want to zoom in a bit closer. What you've shown would tend to indicate that the low pitch stop is set low, and you're getting an overshoot before the governor catches it. The amount of overshoot will vary based on throttle application rate, and how low the stop is set.

A well set low pitch stop for an NA engine would tend to show max rpm less than governing, and a trend of increasing rpm with airspeed increase until reaching governing RPM.
 
dnickerson46 said:
Is engine monitor data useful for evaluating the prop adjustment? Looking at the EDM data which is captured in 4 fractions of a second, I see the prop increase to above 2700 very quickly for a second then settles down to 2650 for the remainder of the ground roll. The aircraft is a -9A with a O-360, Hartzell prop and MT governor. Here is what the RPM graph looks like with 3 takeoffs and landings around the pattern.

View attachment 61016
Click to expand...
Looks like you can’t maintain 2700 rpm in the climb? Raise your governor setting be backing out the screw on the governor.. and adjusting the cable so the blue knob isn’t bottoming on the panel before the governor hits the stop. Then to get rid of the surge, adjust the propellor low pitch stops to provide 2650 static. If you can’t maintain 2700 in the climb, you are not using the full 180 hp..
 
TParker said:
Yes, it can be useful, though you'll want to zoom in a bit closer. What you've shown would tend to indicate that the low pitch stop is set low, and you're getting an overshoot before the governor catches it. The amount of overshoot will vary based on throttle application rate, and how low the stop is set.

A well set low pitch stop for an NA engine would tend to show max rpm less than governing, and a trend of increasing rpm with airspeed increase until reaching governing RPM.
Click to expand...
Thanks for the feedback. Here is the data zoomed to 28 seconds of the takeoff role and climb. The RPM is on the left vertical axis and MP and fuel flow is on the right. It does look like the prop is overshooting and stays at 2670 in climb.

2024-04-19 21_48_31-stream_0416_2055.csv - Excel.png
 
dnickerson46 said:
Thanks for the feedback. Here is the data zoomed to 28 seconds of the takeoff role and climb. The RPM is on the left vertical axis and MP and fuel flow is on the right. It does look like the prop is overshooting and stays at 2670 in climb.

View attachment 61059
Click to expand...
If you can’t dial in 2700 while you are climbing, you also need a governor adjustment
The governor adjustment screw is about 25 rpm per revolution. Just make sure your prop cable allows full forward
 
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I just did this on my 8 today. Night and day difference in the glide. Before, there was so much braking effect I was landing with the prop control back to keep from dropping like a rock and also not using full flaps. Now it glides like it should. Also, no surge on takeoff. I did as Tom suggested and it took exactly 2 1/3 turns and is now at 2600 static. As soon as it gets moving the RPM increases up to 2680 and the governor kicks in.

Had I had a governor failure before, I’m quite certain it would have gone 3100+ RPM and would not have climbed well at all. This took all of fifteen minutes or so to do.
 
If you are going to run your birds up to 2650 rpms, I would tie down the tailwheel really, really well. Seen a couple of airplanes on the nose from this sort of monkey motion. Makes for a bad day. If you think the nose draggers can't do it, I've seen that one too. So please be careful and responsible. Engine parts are getting harder and harder to find these days. Turn around for OH's could be 6 mos to 1 year. These planes are light with a lot of power so run ups need to be taken with extreme caution and good countermeasures in place.
 
Aden Rich said:
If you are going to run your birds up to 2650 rpms, I would tie down the tailwheel really, really well. Seen a couple of airplanes on the nose from this sort of monkey motion. Makes for a bad day. If you think the nose draggers can't do it, I've seen that one too. So please be careful and responsible. Engine parts are getting harder and harder to find these days. Turn around for OH's could be 6 mos to 1 year. These planes are light with a lot of power so run ups need to be taken with extreme caution and good countermeasures in place.
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Stick back, tail tied down, flaps up, and chocked.
My tail still lifted. FWIW

However, it would not have gone over on the nose as long as the stick is full back. I was expecting it, but still unnerving.
 
The guy that finished off my Rocket/F-1 EVO airplane was doing these run ups with no tail tie down and went right over on it's nose. In Germany of all places. I had to help him get his engine (that I built) back to the states for a rebuild. Ended up being a gorgeous airplane but man, what a downer day getting that call. I forgot to mention that torque loves to flip planes over as well. Big props, light airplanes. Seen a C206 with a brand new engine doing full power run ups on the ramp and then I heard this god awful noise from my hanger and peeked around the corner and it was on its nose/back. Back in the hanger it went for another 6 mos....... :(
 
JonJay said:
Stick back, tail tied down, flaps up, and chocked.
My tail still lifted. FWIW

However, it would not have gone over on the nose as long as the stick is full back. I was expecting it, but still unnerving.
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Flaps up, stick back, brakes held, if the tail starts to rise, release the brakes!! I would not chock it, because it removes an option for you to release the brakes. Heck, you could even do it on the runway and perform a takeoff with the check. If you don’t want to split your attention, either bring a passenger to video the tach or set up a GoPro aimed at the panel.
I thought some people were concerned about full power runup pulling on the tail tiedown.. I just do it in the runup area and if the plane starts to roll, I throttle back. Easy. Never had the tail lift with the stick back as long as the flaps are retracted.
 
I did a very small number of sustained full-power runups on the ground, pre-first-flight to ensure I was getting proper static RPM. Used heavy duty ratchet straps to tie both gear legs to the ground, as high up on the gear against the fuselage I could go. Since I have the -A model, I wrapped a third strap between the gear legs, to keep the main straps from sliding down the legs. Even strapped down like this, the thing bucked around like a horse. Pretty scary. I probably wouldn't do it again.

 
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