Check your CS prop “low pitch” stops

[Taltruda]

I’ve been flying, repairing, and maintaining RVs for a while now, and I observed that most RVs with Constant Speed props aren’t adjusted correctly. They just bolt them on out of the box, maybe set max RPM with the governor screw or worse, the cable length. I just wanted to throw this out there, most pilots don’t even know the prop isn’t adjusted right (or they don’t know there is any such adjustment)

If you get any surging on takeoff, your low pitch stops aren’t adjusted right. You shouldn’t have to throttle in really slow, although that’s a great technique. If you were to advance the throttle quickly, you shouldn’t get any surging or overshoot past rated (2700) RPM. Preferably, you only get 2650 static at under, say, 20 knots. Then as you accelerate, the rpm creeps up as the airspeed approaches liftoff, at which time the governor is able to control it to 2700rpm. Also if your plane falls out of the sky, that’s another sign that the low pitch stops are not set correctly. Once you get them set, the plane glides much better.. if you are flying around with the low pitch stops set too low, and if you have a governor failure, you are risking a massive overspeed. If you were to have an engine failure, your glide will be like a rock.. but set correctly, you’ll have a fighting chance with either scenario.

The last two planes with a Hartzell CS prop took 2 1/3 turns in on the low pitch stop Allen screw. It was night and day easier and enjoyable to fly after that!

 

[Walt]

Agree 100%. I’d venture to same the majority of RV owners never bother to adjust the low pitch stop.
Easy to hear the surging on TO as they jam the throttle forward.
The procedure is in the Hartzell owner manual, but you will have to actually open the book and read it !

 

[Bill Boyd]

Advancing the throttle rapidly on take-off is not recommended for pendulum-counterweighted engines, or so I've been told.

 

[TParker]

As mentioned, the hands on instructions for how to adjust the stop are in the owner's manual for the specific propeller. The owners manuals, however, assume that you're troubleshooting and not integrating for the first time. Manual 193 Volume 2, written to assist with integration on experimental aircraft, provides the explanations of the things adjusting the low pitch can affect, as there are multiple phases of operation where the propeller may be on the low pitch stop, and suggested test procedure for determining the correct setting for the specific aircraft and individual.

 

[vic syracuse]

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

 

[Taltruda]

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

Vic, great video on the Low pitch stops!! You nailed it! Now if only we could get more people to realize that they probably need this adjustment.. a friend of mine recently had a governor go bad, RPM spiked to over 3000RPM.. ugly.. had his low pitch stops been set, he could have climbed normally and flown the pattern with a “fixed pitch” prop..

 

[vic syracuse]

All of you should let me know of other topics that could use a video or a column. Carol tells me I need to do more and that I take it for granted that others understand some of the operational stuff.
Vic

 

[wirejock]

All of you should let me know of other topics that could use a video or a column. Carol tells me I need to do more and that I take it for granted that others understand some of the operational stuff.
Vic

Thanks for that Vic. I've already bookmarked it for very soon.

I would love to see a video from prep, first engine start, through post run check list.

 

[Draker]

It can be tough to diagnose too, if your governor is also adjusted incorrectly. For my first few flights (IO-360-M1B), my governor was set too low, to 2630, and this very low setting seems to have hidden the telltale RPM surge. Once I adjusted the governor to 2680 RPM, I started observing it surging to ~2770 on the takeoff run, which was confirmation that the pitch stop was also set incorrectly. From there, it's just a matter of adjusting it, watching what the max RPM is on takeoff, adjusting again, repeating until you're no longer surging above redline. It's good peace of mind to know that if the governor fails, I have a physical stop preventing the engine RPM from going crazy. Also, being gentle on the throttle during takeoff seems to help too. No need to slam it in for takeoff. I even remind myself in my checklist to "Use GENTLE and SMOOTH motion when opening throttle."

 

[Taltruda]

It can be tough to diagnose too, if your governor is also adjusted incorrectly. For my first few flights (IO-360-M1B), my governor was set too low, to 2630, and this very low setting seems to have hidden the telltale RPM surge. Once I adjusted the governor to 2680 RPM, I started observing it surging to ~2770 on the takeoff run, which was confirmation that the pitch stop was also set incorrectly. From there, it's just a matter of adjusting it, watching what the max RPM is on takeoff, adjusting again, repeating until you're no longer surging above redline. It's good peace of mind to know that if the governor fails, I have a physical stop preventing the engine RPM from going crazy. Also, being gentle on the throttle during takeoff seems to help too. No need to slam it in for takeoff. I even remind myself in my checklist to "Use GENTLE and SMOOTH motion when opening throttle."

It’s actually really easy to set without even flying it.. you set takeoff RPM to around 2650 on the ground. You can hold the brakes, or even allow it to roll a little. You could even apply full throttle down the runway and then throttle back. Have a copilot in the other seat, or video the tach. As for the prop governor adjustment, you can back the high RPM screw one turn off, perform a takeoff, keeping the RPM from going to high with manual adjustment of the blue knob, then in cruise, set the blue knob to 2700, and bring the plane in for a landing without touching the blue knob. Decowl the engine and bring the governor screw in to meet the position of the lever. Done!

Yes it’s always best too throttle in slow, and throttle out slow, but for this test, I feel it’s ok (especially non counterweights cranks) to bring the throttle in to about 2500 rpm, then sorta quickly go the rest of the way in. If the low pitch stops aren’t set, you’ll get a little over shoot. If they are set, the rpm will be rock solid

 

[Bill Boyd]

I know this is the CS prop low pitch limit thread and not the Endless Magnetos vs. Electronic Ignition Debate thread, but the CPi2 and perhaps others has a rev limiter value that the ignition will not supply spark in excess of. Set it for 2750-2800 and never have to worry about ever hitting 3000 rpm if the governor packs it in. Not a replacement for properly setting the pitch stop, but a nice backsotop.

 

[Taltruda]

I know this is the CS prop low pitch limit thread and not the Endless Magnetos vs. Electronic Ignition Debate thread, but the CPi2 and perhaps others has a rev limiter value that the ignition will not supply spark in excess of. Set it for 2750-2800 and never have to worry about ever hitting 3000 rpm if the governor packs it in. Not a replacement for properly setting the pitch stop, but a nice backsotop.

No, not the same thing.. if the prop is going so flat that the ignition Rev limiter needs to kick in, then, sure, you wont overspeed the engine, but you also won’t have any power! If this happens on takeoff, good luck not hitting the trees! Having the low pitch stops set correctly is for safety.. it’ll still climb full throttle, you’ll be able to control RPM with airspeed. And if you lose the engine, it’ll glide much better and give you a chance to make it somewhere. The rev limiter isn’t going to help with that.

 

[Bill Boyd]

... if you are flying around with the low pitch stops set too low, and if you have a governor failure, you are risking a massive overspeed.

This is all I was referring to. Agree with all that you have said. I'm pretty sure an EI with rev limiting will not let this particular abuse occur in the event the stops are not set correctly - as they certainly should be for all the other reasons.

 

[TParker]

It’s actually really easy to set without even flying it.. you set takeoff RPM to around 2650 on the ground. You can hold the brakes, or even allow it to roll a little. You could even apply full throttle down the runway and then throttle back. Have a copilot in the other seat, or video the tach. As for the prop governor adjustment, you can back the high RPM screw one turn off, perform a takeoff, keeping the RPM from going to high with manual adjustment of the blue knob, then in cruise, set the blue knob to 2700, and bring the plane in for a landing without touching the blue knob. Decowl the engine and bring the governor screw in to meet the position of the lever. Done!

You can set both to a good initial setting without flying. Fine the low pitch stop significantly to get onto the governor, and set the governor. Then coarsen the low pitch stop significantly to drag the RPM down below the governor, fine tune from there. Tracking the changes (e.g. 1/4 of a turn) to the pitch stop with the resultant RPMs makes it pretty quick. Adjust from there based on other characteristic behavior in flight.

This is all I was referring to. Agree with all that you have said. I'm pretty sure an EI with rev limiting will not let this particular abuse occur in the event the stops are not set correctly - as they certainly should be for all the other reasons.

An EI rev limiter will prevent you from overspeeding the prop/engine by adding power, but you could still overspeed it with airspeed in the same way your EFI rev limiter on your car won't save you if you drop it into second gear on the highway.

Also worth considering, in the case of an EI rev limiter, that you may want to overspeed the prop by adding power. An oil to increase pitch constant speed prop with the low pitch stop set for 25-50 RPM below rated at static with a governor failure or oil supply failure can still be finer than the finest takeoff/climb fixed pitch prop you've ever flown. In an emergency situation, given the choice between overspeeding the engine/prop and not maintaining flight and going into the trees, overspeed the prop/engine to stay in the air; this may require flying below the best glide airspeed to achieve a good combo of thrust/airspeed/rpm.

If you have a rev limiter, I recommend giving serious consideration as to what you have it set to and the instances in which it could be activated. Another example of why setting the low pitch stop is something that should be a deliberate choice; you can mitigate this failure somewhat at the expense of initial takeoff and climb performance by increasing the low pitch setting.

 

[Bill Boyd]

You can set both to a good initial setting without flying. Fine the low pitch stop significantly to get onto the governor, and set the governor. Then coarsen the low pitch stop significantly to drag the RPM down below the governor, fine tune from there. Tracking the changes (e.g. 1/4 of a turn) to the pitch stop with the resultant RPMs makes it pretty quick. Adjust from there based on other characteristic behavior in flight.


An EI rev limiter will prevent you from overspeeding the prop/engine by adding power, but you could still overspeed it with airspeed in the same way your EFI rev limiter on your car won't save you if you drop it into second gear on the highway.

Also worth considering, in the case of an EI rev limiter, that you may want to overspeed the prop by adding power. An oil to increase pitch constant speed prop with the low pitch stop set for 25-50 RPM below rated at static with a governor failure or oil supply failure can still be finer than the finest takeoff/climb fixed pitch prop you've ever flown. In an emergency situation, given the choice between overspeeding the engine/prop and not maintaining flight and going into the trees, overspeed the prop/engine to stay in the air; this may require flying below the best glide airspeed to achieve a good combo of thrust/airspeed/rpm.

If you have a rev limiter, I recommend giving serious consideration as to what you have it set to and the instances in which it could be activated. Another example of why setting the low pitch stop is something that should be a deliberate choice; you can mitigate this failure somewhat at the expense of initial takeoff and climb performance by increasing the low pitch setting.

Trevor - thanks for this. I'm learning new things that I need to know.

I didn't appreciate that windmilling was "efficient" enough to drive an engine way past redline with the ignition off (i.e. in rev-limiting mode) - having heard stories of engine-outs where pilots had to point the nose steeply downhill just to get enough rpm to try a restart.

I do have a rev limiter in the SDS system, set to whatever value Ross said to use - honestly don't remember what it was.

 

[riseric]

you wont overspeed the engine, but you also won’t have any power! If this happens on takeoff, good luck not hitting the trees!

Agree that a correctly set governor is very important !!!

As for the EI rev limiter, in the trees ? Maybe, maybe not... it depends

Here's a video (turn the sound on) of my first flight take-off.
There's an extra (normal sounding) one at the end of this post.

Full prop and full throttle of course.
During the ground run, everything is fine. Just after wheels up and accelerating, the engine started to studder.
I confirm that a short span of time goes by (startle factor) before realizing something's wrong.
No flaps, 80 - 90 KIAS, I then judged I had not enough time to decelerate, flare, land and brake with the remaining runway. There's a ditch, a road, power lines and trees at the end of the 3000' runway. The airspeed was above 90 and holding and I was climbing so I pressed on, knowing that a highway is parallel just on the right.
At 500 AGL and still climbing, I started to turn to join a low downwind overflying the highway , I reduced the throttle gently, checking if it would change something. No change.
But as soon as I reduced the prop speed, bam, there's the great sound of a properly growling engine !!!

I left the RPM at 2600, set the MP at 26", climbed to 3000' and orbited the field for a while, monitoring all engine data. All was well.
After landing, I could not replicate the issue, the static RPM being 2650.
Dowloaded the engine data, it showed that at 2680 RPM the engine dropped to 2640 before increasing to 2680 and back down to 2640 again and again and again...

The EI rev limiter was set to 2700 RPM. I know that I checked that value before first flight but can't say if I input that number or if it was factory set.
So to "protect" the engine, the ignition cut just 20 RPM before.
Luckily, the "cuts" were very brief, robbing me of some power but leaving enough for me and the airplane to see another day.
The rev limiter was reset to 2750 and the issue was resolved. The governor is doing its job, maxing out at 2700.

My girlfriend and 2 other friends were witness to the mishap. They did not appreciate... until they heard me overfly the field with the engine sounding proper.

Afterthoughts: I had no time to stress in those few seconds, I just flew the airplane, evaluated what I had in front of me, planned a return.
I'm glad and lucky the engine still produced enough power to keep the speed and still climb.
When the RPM was strong and steady, I felt confident to stay above the field, climb, orbit and check things out. I could then recollect myself, although I didn't realise it at the time.
Inflight, I thought about a briefly blocked injector, a temporary fouled plug, a wrong mixture/fuel map setting, but never the rev limiter.
Because the engine was running fine, and considering break-in, I did not move the prop lever forward to maximum for all the remaider of the flight. 2600 RPM was mighty fine for 40ish more minutes.
If I had increased the prop speed, I would have reproduced the misfire but I doubt I would have understood the cause. The data told the story.
Maybe an immediate landing/hard braking could be made successfully, I'll never know.
I plan on measuring the start/stop distance of a similar takeoff at a longer runway.
I now know that if the governor fails, the rev limiter will do its job, cutting off the ignition at 2730 or so.
Although I have no surges, I will check the stops.
Despite thourough planing, checking, preperation and contingency plans, s**t can happen.

Here's a video 3 days later, doing Transport Canada's gross weight climb test. Much better

Fly safe !!

 

[Bill Boyd]

Great story, Eric! Thanks for sharing.

One question occurs to me: was this incident more benign than it sounded/felt at the moment? I would think (please correct me if I am wrong) that the actual performance you got from the aircraft was what it would have been at 2640 rpm without the rev limiter activating? Seems like 2640-2680 rpm should have given you very acceptable takeoff and climb performance, similar to a FP prop, disregarding the pucker factor from the unexpected pulsing. Did you have any after-firing from the spark cutting out? I don't hear any in the video but it would not have surprised me.

 

[TParker]

I didn't appreciate that windmilling was "efficient" enough to drive an engine way past redline with the ignition off (i.e. in rev-limiting mode) - having heard stories of engine-outs where pilots had to point the nose steeply downhill just to get enough rpm to try a restart.

It's dependent on several factors, but prop pitch and airspeed are chief among them. Fixed pitch props on certificated aircraft have a requirement (§23.33, Amendment 63 or earlier) to not overspeed by more than 10% at aircraft VNE and closed throttle. In general, reduce the propeller pitch and the airspeed at which the prop will overspeed lowers as well. So in the case of a governor malfunction or oil supply issue on a CS prop, with a low pitch finer than most fixed pitch props, the prop is going to overspeed from windmilling at airspeeds less than VNE. It probably wouldn't overspeed at all at a normal approach speed and closed throttle, but probably would overspeed a good bit from a failure at cruise speeds. And a little bit of added power goes a long way to increasing the amount of overspeed. In the case of some other type of failure, like fuel starvation, at too low of an airspeed the prop won't extract enough energy to turn the engine and it will come to a halt, but above the minimum airspeed required to extract enough energy to overcome the engine, it'll rotate at some RPM as a function of airspeed up to the governor set point at which point the governor will begin to regulate the blade angle to maintain RPM.

 

[Taltruda]

Agree that a correctly set governor is very important !!!

As for the EI rev limiter, in the trees ? Maybe, maybe not... it depends

I think you are missing the point.. on takeoff, you shouldn’t be in the governor range.. a correctly set low pitch stop is what will be limiting your takeoff RPM. If you are being controlled by the governor, that’s a problem. If you had properly adjusted low pitch stops, and you were to raise your governor limit to say 2800, you would still only see 2650 max on initial takeoff until you built enough airspeed. It definitely sounds like your prop rpm going from 2680, to 2640 and back means you are on the governor, and I would bet that your plane would benefit from proper adjustment.

How does your plane fly in the pattern? Can you close the throttle and glide to a normal landing? Or are you flying a power on approach? With properly adjusted pitch stops, the plane will glide so much better.

if I had a rev limiter, I would set it to 2950.. high enough that I should never hit it, but low enough to prevent a mand prop inspection.

 

[riseric]

Great story, Eric! Thanks for sharing.

One question occurs to me: was this incident more benign than it sounded/felt at the moment? I would think (please correct me if I am wrong) that the actual performance you got from the aircraft was what it would have been at 2640 rpm without the rev limiter activating? Seems like 2640-2680 rpm should have given you very acceptable takeoff and climb performance, similar to a FP prop, disregarding the pucker factor from the unexpected pulsing. Did you have any after-firing from the spark cutting out? I don't hear any in the video but it would not have surprised me.

Bill,
I really don't think the engine was producing power as if it was turning normally at 2640 - 2680 RPM.

I spent some time this morning extracting data from that period of flight. Here's what I found:
Data was recorded twice per second. Precision is therefore limited.
On average, between each high and low RPM, there's a 1 or 2 second variation. A 45 second sample shows a low of 2645 and a high of 2683.
Sometimes the variation/pulsing was only 4, and sometimes 35.
Basically, I would presume that the ignition only fired 50% of the time.
Depending on which cylinder was firing/should fire, that would account for the variations in pulsing frequency.

Remember that this was my first flight in this first flight of this RV. I was very cautious for takeoff, advancing power very gradually, not wanting to be bitten by P-factor/torque.
Throttle was shyly advanced to 27,6 only.
Wheels up at 70 KIAS
Pulsing started at 82 KIAS
Manifold pressure was pulled back to 24,5 shortly after wheels up. Probably the startle made me do that unconsciously.
Initial climb rate with that MP at 88 - 90 KIAS was 654 ft/min.
Curiously, a minute later MP was increased to 26,3 with speed 90 - 94 KIAS but rate of climb decreased to 210 ft/min.
I can only speculate that at different MP's, the ignition cuts are of different lenghts/intervals, affecting power output.

I then leveled off at ~700 AGL, keeping ~92 KIAS, reducing the MP to 14 -15. That's when I started to diagnose stuff I guess.
10 seconds later, RPM was reduced to 2600, no more pulsing, then to 2500, steady.
About a minute later MP was increased to 24 - 25, RPM steady, speed increased to more than 150 KIAS in a shallow climb.

Total pulsing time: 1 minute 40 seconds
It seemed a lot longer than that...

 

[riseric]

I think you are missing the point.. on takeoff, you shouldn’t be in the governor range.. a correctly set low pitch stop is what will be limiting your takeoff RPM. If you are being controlled by the governor, that’s a problem. If you had properly adjusted low pitch stops, and you were to raise your governor limit to say 2800, you would still only see 2650 max on initial takeoff until you built enough airspeed. It definitely sounds like your prop rpm going from 2680, to 2640 and back means you are on the governor, and I would bet that your plane would benefit from proper adjustment.

How does your plane fly in the pattern? Can you close the throttle and glide to a normal landing? Or are you flying a power on approach? With properly adjusted pitch stops, the plane will glide so much better.

if I had a rev limiter, I would set it to 2950.. high enough that I should never hit it, but low enough to prevent a mand prop inspection.

Tom, thanks for your input.
My pulsing was definitely caused by a too low rev limiter setting. Without changing anything else, increasing the rev limiter up 50 RPM solved the issue.
Check the video, by the sound it doesn't seem a rapid pitch change by the governor. More a popping on - off sound.
Doesn't mean the governor is correctly set. I will check and adjust the low stop if needed.
To date, I never observed surging, even when advancing throttle quite rapidly.
Explain how can a governor limit be set at 2800 but only see 2650 on static RPM ??? I'd like to understand.

I do approach with power, full fine and 2000 rpm, makes for a Cessna type gliding approach. If I cut to idle, I have to be a lot closer on downwind !!!
Consider I have a 3 blade prop, it brakes.

 

[moespeeds]

I set mine up when I got my Whirlwind 300 thanks to Tom's help. The method I used was to do the static run and adjust the stop down to about 2600, then test fly and gradually open it up so I could get 2700 by around 50 kts on takeoff. Governor is set at max travel, so the low pitch stop is 100% governing RPM at takeoff power. It took around 2-3 full turns of the nut for me to get there.

It's worth noting that this makes a very noticeable difference in glide ratio (seat of the pants, but before adjusting the 3 blade prop had me dropping like a rock). This reason alone made it worth the time I took to tinker with it. It is for sure a safety of flight issue.

 

[Mike S]

I would suggest that if you make any large changes in prop angle, that you verify the spinner openings are still clear of the prop at low pitch.

 

[Taltruda]

I would suggest that if you make any large changes in prop angle, that you verify the spinner openings are still clear of the prop at low pitch.

Adjusting the low pitch stops actually limit blade travel. Basically you are preventing the prop from going too flat.

 

[Taltruda]

Tom, thanks for your input.
My pulsing was definitely caused by a too low rev limiter setting. Without changing anything else, increasing the rev limiter up 50 RPM solved the issue.
Check the video, by the sound it doesn't seem a rapid pitch change by the governor. More a popping on - off sound.
Doesn't mean the governor is correctly set. I will check and adjust the low stop if needed.
To date, I never observed surging, even when advancing throttle quite rapidly.
Explain how can a governor limit be set at 2800 but only see 2650 on static RPM ??? I'd like to understand.

I do approach with power, full fine and 2000 rpm, makes for a Cessna type gliding approach. If I cut to idle, I have to be a lot closer on downwind !!!
Consider I have a 3 blade prop, it brakes.

to answer your question on how rpm will only go to 2650, when your gov is set to 2800.. what you are accomplishing when you set your low pitch stops is you are restricting the prop from going super flat. Basically, you are making the prop maintain some AOA that it can’t go any flatter. Just like a fixed pitch prop doesn’t let your rpm go above 2200 rpm statically. Then as you build up speed down the runway, the oncoming air (relative to the chord line) changes, reducing the prop AOA and allows the prop to “unload” and increase its rpm. Then around liftoff, the rpm should creep to about 2700, where the governor can then adjust blade angles and maintain a governed rpm setting. Message me, and we’ll talk on the phone if you are interested. My who.e point of making the initial post is that there are so many planes out flying and they don’t even realize that their setup isn’t right. After you perform the low pitch stop procedure, it’ll glide better and be safer in the event of an engine or governor failure. You should be able to go to idle from a normal downwind and glide pretty good, making a normal landing without the plane falling out of the sky.there is still some braking but not as extreme.

 

[Swingwing]

Thanks for that Vic. I've already bookmarked it for very soon.

I would love to see a video from prep, first engine start, through post run check list.

plus 1 on a first start video!

 

[rv8ch]

Great story, Eric! What's amazing is that I had almost exactly the same experience on my first flight. Some details were slightly different since I have a Hartzell 2-blade. The takeaway is that setting the prop low speed stop, and setting the prop controller is extremely important, and I honestly don't recall it being discussed much before my first flight.

Since the only way you can set the prop controller and low speed prop setting properly is to fly, it should be briefed on the first flight to ensure that the pilot knows that full forward on the blue knob might be greater than 2700 or whatever max prop speed you want.

My GRT EFIS was shouting at me that the prop was going past 2700 but it took me a good 10-15 seconds to see/hear it. Those were a very exciting few seconds!

I did full power static thrust tests on the ground, with the aircraft tied down, but adding the forward velocity of the aircraft got me slightly over 2700.

I think the additional emphasis on this will help other builders.

 

[RV8RIVETER]

Nice thread Tom. A lot less info on the subject 10 years ago.

WW 200RV owners question

Hello I would like to post a question to all of those who have the 200RV prop and IO-360 angle valve engine. Trying to compare engines hp using static rpm with the same prop. What is your max RPM initially on take-off roll (or ground run if you did one) with no governor control? Did you...

vansairforce.net

 

[Taltruda]

Nice thread Tom. A lot less info on the subject 10 years ago.

WW 200RV owners question

Hello I would like to post a question to all of those who have the 200RV prop and IO-360 angle valve engine. Trying to compare engines hp using static rpm with the same prop. What is your max RPM initially on take-off roll (or ground run if you did one) with no governor control? Did you...

vansairforce.net

Nice thread! I read your post, I would say you nailed it back then!

 

[riseric]

Thank you Tom for your help.
I sure never heard about checking and adjusting the low stops before this thread. I'm one of them bolting on the prop and governor and GO!
Love this site and the people here, thanks again Doug.
Thank you Vic for the video, very informative.
And thank you EFIS data !!!
After checking a random flight, comparing KIAS and RPM, I notice a peak of 2720 RPM at 38,4 KIAS.
Then 2684 - 2690 afterwards.
Looks like a low stop adjustment is in order. And after that, a slight governor tweek.
I understand now the difference between low stop and governor adjustments. 2 different animals.
Fun work coming up on the RV !!
Can't find which way to turn the big nut in my MT manual. It says that there are nuts but not which way, left/right or in/out to adjust.
Quote:
"Outside the hub are two check nuts with which the low (high) pitch
stop can be adjusted."
And elsewhere:
"Low and high pitch stops are adjusted during manufacture, ac-
cording to the requirement of the aircraft/engine combination.
Low pitch stop can be adjusted by varying the check nuts. High
pitch can only be adjusted in a service station."
The MT service manuals are only available to service centers...

Can anyone guide me here? I'd like to increase pitch/blade angle (lower static RPM)

 

[Taltruda]

Thank you Tom for your help.
I sure never heard about checking and adjusting the low stops before this thread. I'm one of them bolting on the prop and governor and GO!
Love this site and the people here, thanks again Doug.
Thank you Vic for the video, very informative.
And thank you EFIS data !!!
After checking a random flight, comparing KIAS and RPM, I notice a peak of 2720 RPM at 38,4 KIAS.
Then 2684 - 2690 afterwards.
Looks like a low stop adjustment is in order. And after that, a slight governor tweek.
I understand now the difference between low stop and governor adjustments. 2 different animals.
Fun work coming up on the RV !!
Can't find which way to turn the big nut in my MT manual. It says that there are nuts but not which way, left/right or in/out to adjust.
Quote:
"Outside the hub are two check nuts with which the low (high) pitch
stop can be adjusted."
And elsewhere:
"Low and high pitch stops are adjusted during manufacture, ac-
cording to the requirement of the aircraft/engine combination.
Low pitch stop can be adjusted by varying the check nuts. High
pitch can only be adjusted in a service station."
The MT service manuals are only available to service centers...

Can anyone guide me here? I'd like to increase pitch/blade angle (lower static RPM)

Found this on a fly Husky forum..

“What you could try in increasing low pitch stop.
Remove spinner, remove safety wire between the huge jam nuts on the dome.
Unjam the nuts. Tighten the rear nut 1 turn, jam and safety nuts again.
Do not run engine without spinner, the small blades behind the propblades will bent.”

 

[riseric]

Found this on a fly Husky forum..

“What you could try in increasing low pitch stop.
Remove spinner, remove safety wire between the huge jam nuts on the dome.
Unjam the nuts. Tighten the rear nut 1 turn, jam and safety nuts again.
Do not run engine without spinner, the small blades behind the propblades will bent.”

Yeah, I saw that too yesterday. But it doesn't say which propeller model.
So I finally found in the troubleshooting section of my propeller's manual the way to do it.
Quote:
"Reduce pitch with the check nuts on the piston guide.
Turning loose nut by ¼ turn will increase rpm by ap-
prox. 100 rpm. This is only applicable for non-counter-
weighted propellers!"

For me, it will be to tighten the nut to increase pitch.

 

[kiljoy]

Yeah, I saw that too yesterday. But it doesn't say which propeller model.
So I finally found in the troubleshooting section of my propeller's manual the way to do it.
Quote:
"Reduce pitch with the check nuts on the piston guide.
Turning loose nut by ¼ turn will increase rpm by ap-
prox. 100 rpm. This is only applicable for non-counter-
weighted propellers!"

For me, it will be to tighten the nut to increase pitch.

So I attached a digital level to the tip of one of the blades on myt MT. Its not a flat surface but I got it more or less level to the apex of the curve. Adjusted 1/8 turn (what MT says should be ~50rpm) in to see if that takes my prop from 2700-2650. It changed the angle from 5.31º -> 5.48º. The rain has stopped for a bit, will run it up today to see if that was enough of an adjustment.

 

[riseric]

So, I tied down the tail of the -8 today and adjusted the low-pitch stops. Increased pitch to 2650 static (1/4 turn did the trick).
I had marked one of the blades and yes, it moved very slightly.
For those who never did this before, don't forget to cycle the prop slightly when full throttle after every adjustment.
So I probably had flatter blades than necessary or useful. (2750 RPM value but restricted to 2700 by the governor)
Next flight due in a week or so, I'll report how I perceive the (new) gliding behaviour.

 

[Denok]

I have a Whirlwind 200rv prop with a Jihostroj governor and I can't find any info anywhere on low pitch stop adjustments. Does anyone know if it's available?

 

[Taltruda]

I have a Whirlwind 200rv prop with a Jihostroj governor and I can't find any info anywhere on low pitch stop adjustments. Does anyone know if it's available?

I checked the 200 manual, and it doesn’t show it, but the 300 series manual shows a bug nut. They say to turn it clockwise to lower static RPM and to aim for 2550 to 2600 static. Then you’ll fly it and if you cannot make 2700rpm in flight, you’ll loosen the governor screw counterclockwise 90 degrees per 50 rpm.

 

[SuperCubDriver]

I have a Whirlwind 200rv prop with a Jihostroj governor and I can't find any info anywhere on low pitch stop adjustments. Does anyone know if it's available?

It is more work to adjust the low pitch stop on the WW200 compared to the Hartzell.
It is best to order at least one extra dust seal as this might be damaged. You have to remove the hub with all these small hex bolts. Note the position of a balance weight you might or might not have bolted on with the hub. When you pull off the hub from the piston some oil will drip so prepare for this with a tray below. Adjustment is done with shims - you have to add shims to adjust the low pitch stop to a greater blade angle. So you possibly need extra shims (easy to make if you have access to a milling machine) and a new dust seal. You might have to do this more than once to get the adjustment right. I made a tool to push down the piston in order to get the snap ring off and add or remove shims. Here are a few pics:

 

[Rockyjs]

Thanks SuperCub!
I have a WW 200RV prop and the owner's manual doesn't have anything for adjusting the low pitch stop. I've reached out to WW.
My prop is smooth, but I have no idea where the low pitch stop is set. Your "homemade" tool is very nicely done.
Any drawing of the pieces? It appears the shims are aluminum ?
Thanks for shedding some light!

Rocky

 

[SuperCubDriver]

Thanks SuperCub!
I have a WW 200RV prop and the owner's manual doesn't have anything for adjusting the low pitch stop. I've reached out to WW.
My prop is smooth, but I have no idea where the low pitch stop is set. Your "homemade" tool is very nicely done.
Any drawing of the pieces? It appears the shims are aluminum ?
Thanks for shedding some light!

Rocky

Rocky,
I have no drawing or dimensions for the tool, sorry. I just measured the distance of two holes and used four metal plates as a holddown. The tool is not required and as far as I can remember the piston can be pushed down by hand. Best is to have two helpers to do this while you remove the snap ring.
And yes the shims are aluminum.

 

[rvanstory]

...most pilots don’t even know the prop isn’t adjusted right (or they don’t know there is any such adjustment)

If you get any surging on takeoff, your low pitch stops aren’t adjusted right. You shouldn’t have to throttle in really slow,

The last two planes with a Hartzell CS prop took 2 1/3 turns in on the low pitch stop Allen screw. It was night and day easier and enjoyable to fly after that!

I just wanted to say THANK YOU for posting this!!! After reading your post, I put it on my "to do" list for the next time I was doing maintenance. Yesterday I performed the test and made the needed adjustments. I found my low pitch settings to be way off! (too high of RPM)

I was AMAZED at how much smoother the plane reacts during takeoff! I always thought the surging was just a result of a more powerful engine (IO-540) than I was accustomed to flying, so I would SLOWLY put the throttle in to full power. Just like in your original post, I had to turn the low pitch allen screw in 2 1/3 turns to achieve 2660 RPM while sitting still at full throttle.

After this, the 1st takeoff was incredibly smooth. I then needed to make an adjustment to my max RPM stop on the governor. On the 2nd test flight I just "put the pedal to the medal" with full throttle instantly. Takeoff was SMOOTH AS SILK!!! I was not expecting the takeoffs to feel so different (smoother and better) when applying full throttle more abruptly.

For others thinking about checking your low pitch settings.... DO IT!

 

[Taltruda]

I just wanted to say THANK YOU for posting this!!! After reading your post, I put it on my "to do" list for the next time I was doing maintenance. Yesterday I performed the test and made the needed adjustments. I found my low pitch settings to be way off! (too high of RPM)

I was AMAZED at how much smoother the plane reacts during takeoff! I always thought the surging was just a result of a more powerful engine (IO-540) than I was accustomed to flying, so I would SLOWLY put the throttle in to full power. Just like in your original post, I had to turn the low pitch allen screw in 2 1/3 turns to achieve 2660 RPM while sitting still at full throttle.

After this, the 1st takeoff was incredibly smooth. I then needed to make an adjustment to my max RPM stop on the governor. On the 2nd test flight I just "put the pedal to the medal" with full throttle instantly. Takeoff was SMOOTH AS SILK!!! I was not expecting the takeoffs to feel so different (smoother and better) when applying full throttle more abruptly.

For others thinking about checking your low pitch settings.... DO IT!

Thank you for the feedback! I am just as excited for you as you are! That’s why I wanted to bring this up to everybody else who don’t realize what they are missing.. also did you notice better glide at idle? It’s also safer too incase you were to lose the governor or oil pressure..

 

[JonJay]

Also a thanks to you and for Vic’s excellent video. I also was prompted to test this as part of my CI, in progress.
Mine tested ok. I have a slight over speed, 2710,2720, but it is so quick to settle, about 2690’ish almost instantaneously, my EMS doesn’t even catch the data point. I also have a local “expert” who said don’t mess with it. Your instrument error might be that much? (Don’t think so, but). My static RPM is right on with Vic’s recommendations and I made sure the governor wasn’t kicking in, also per Vic’s video.
Good stuff guys.

 

[togaflyer]

So question. Everything has been solid for 6 year. MT prop RPM all good and no surge. But if I wanted to verify I’m on the low pitch stops for the prop, do I back off the governor adjustment before doing the first run up. How would you begin from your current adjustments if all appears good..….. Cant help fixin something that arnt broke I guess.

 

[Taltruda]

Also a thanks to you and for Vic’s excellent video. I also was prompted to test this as part of my CI, in progress.
Mine tested ok. I have a slight over speed, 2710,2720, but it is so quick to settle, about 2690’ish almost instantaneously, my EMS doesn’t even catch the data point. I also have a local “expert” who said don’t mess with it. Your instrument error might be that much? (Don’t think so, but). My static RPM is right on with Vic’s recommendations and I made sure the governor wasn’t kicking in, also per Vic’s video.
Good stuff guys.

What is your static RPM? Should be 2650.. if you are getting 2700 static, then you don’t know if you are being limited by the low pitch stops or the governor.. It’s so easy to adjust, and the extended glide in the event of an engine failure is worth the adjustment. Lots of pilots don’t realize they have a surge because they are gentle and slow to add power, the way you should fly. But for a “test” you could bring up the throttle to about 2000, then apply full throttle quickly and see if there’s a surge. I wonder if your local “expert” is apprehensive about adjusting it because he doesn’t understand it. Is your prop a Hartzell?

 

[Taltruda]

So question. Everything has been solid for 6 year. MT prop RPM all good and no surge. But if I wanted to verify I’m on the low pitch stops for the prop, do I back off the governor adjustment before doing the first run up. How would you begin from your current adjustments if all appears good..….. Cant help fixin something that arnt broke I guess.

You would back off the governor and slowly advance the throttle while holding the brakes.(Make sure the flaps are retracted, area clear of pebbles ect…) if the RPM seems to want to go above 2700, then throttle back and make the low pitch adjustment. You want the static RPM to be about 2550 to 2650. Then you fly it but don’t let the rpm go above 2700,, limit it with the blue knob. Make some high speed runs to verify that the rpm is limited to 2700, then land without pushing the prop full forward on your “Gumps” check. Set the governor screw to just touch the lever.

If your plane has been flying for 6 years, and you know the full RPM is 2700-2710, I wouldn’t change the governor adjustment.. I would just do the static check and make low pitch stop adjustments to achieve 2650 while static. You will notice a better glide once done. Also safer in the event of a governor failure or loss of oil pressure..

 

[rvanstory]

...did you notice better glide at idle?

I didn't try that out. But on next flight, I will pull throttle back and see if I can tell the difference.

 

[rvanstory]

I also have a local “expert” who said don’t mess with it.

I got the same advice. "I wouldn't do it. Your plane flies so well, why would you want to change anything?" So glad I did it anyway.

 

[JonJay]

What is your static RPM? Should be 2650.. if you are getting 2700 static, then you don’t know if you are being limited by the low pitch stops or the governor.. It’s so easy to adjust, and the extended glide in the event of an engine failure is worth the adjustment. Lots of pilots don’t realize they have a surge because they are gentle and slow to add power, the way you should fly. But for a “test” you could bring up the throttle to about 2000, then apply full throttle quickly and see if there’s a surge. I wonder if your local “expert” is apprehensive about adjusting it because he doesn’t understand it. Is your prop a Hartzell?

Static is 2650, ish….
It’s a Hartzellz. I found his comment about instrument “error” interesting, but didn’t consider his input. I haven’t spoken with JPI to see what they say about “instrument error”.
Doesn’t matter.
I followed Vic’s video and advice, checked to make sure the governor wasn’t in play, and feel things are operating exactly as they should.
I’m not afraid of changing things if I felt it needed it.

 

[togaflyer]

Thanks will do the static run and see. Thanks for the info.

 

[George Costigan]

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?