High Prop RPM

[Glen P]

I'm hoping that someone can give me an idea of how to deal with what I saw today.

In the first year of flying my RV7 with IO-360 and Hartzell CS prop, I consistently saw 2660 RPM on takeoff and climb, even after adjusting the governor high RPM screw. From what I've seen on Savvy, that's not uncommon.

On my first flight today, I saw a sold 2700 on takeoff and climb. I didn't understand it but I was happy to see it. On the return flight, I again saw 2700 on takeoff and climb. The issue came on a touch-and-go at destination. On the go, the RPM increased as high as 2784 and was abnormally high for 28 seconds, even as I was reducing the throttle.

Any thoughts? Thanks.

 

[Tommy123]

Cable creep or the beginning of a governor problem.

 

[Full Throttle]

Did you try turning the BLUE knob?

 

[lr172]

I'm hoping that someone can give me an idea of how to deal with what I saw today.

In the first year of flying my RV7 with IO-360 and Hartzell CS prop, I consistently saw 2660 RPM on takeoff and climb, even after adjusting the governor high RPM screw. From what I've seen on Savvy, that's not uncommon.

On my first flight today, I saw a sold 2700 on takeoff and climb. I didn't understand it but I was happy to see it. On the return flight, I again saw 2700 on takeoff and climb. The issue came on a touch-and-go at destination. On the go, the RPM increased as high as 2784 and was abnormally high for 28 seconds, even as I was reducing the throttle.

Any thoughts? Thanks.

Sorry to say, but this needs immediate attention. First, you have a governor that will not respond to full fine adjustment. Possible that someone installed a 2575 designed governor instead of a 2700 version and that is why you couldn't adjust upward, but it could also be a sign of something wrong inside or the speeder spring installed incorrectly. The bigger issue is the gov holding 2600 forever and then one day hold 2700; I would call this a BAD thing nad not a good thing. The fact that it further drifted to 2780 on the same flight is even worse and a secondary confirmation that things are not right inside. Assuming there is no issue with the cable linkage or gov arm connection, this needs immediate attention before you get a major over-speed on a downhill attitude. Remember that the cable or linkage problem cannot push the arm past the fine pitch limit due to the screw that prevents it and during TO, the linkage is fully relaxed.

The fact that all previous attempts to raise RPM above 2600 failed, points to problems INSIDE the GOV vs. a linkage issue. Hate to pour on more bad news, but there is another issue that can prevent the gov from holding the fine pitch limit and that is lack of oil pressure. The Gov pressurizes the oil and sends it to the prop via the nose bearing to move the blades coarser and bring the RPM down. Any issue in that bearing can prevent the pressure getting to the prop. The sudden onset seems to point to a gov issue over a bearing, but that is just a guess.

 

[D-Dubya]

A couple of thoughts...

You might want to set an alarm on your EFIS to alert if the RPM goes over 2700. If you see that alarm, pull the prop back as quickly as possible. You risk doing some damage if an overspeed continues.

And I'm leaning toward a governor issue as well. Assuming your oil pressure was good and there are no other obvious issues, you might need to pull the governor and send it to an overhaul shop. Just for reference, I had to send my governor out for a re-do with less than 20 hours on it. It just quit working no matter where the blue knob was. The prop/governor shop told me that the seals and internals don't like to sit unused for years on end (mine sat for almost ten years from the time of purchase to the first flight...don't judge me ). They took it apart, cleaned it and changed the seals and it's been fine ever since.

 

[BillL]

What brand prop governor is it?

 

[Untainted123]

How did you know?

You didn't mention how you knew what the RPM's are, but you should verify it with a laser tach gun or there are several apps for your phone that can do it acoustically. Verify first that what you are seeing on the gauge is what is actually happening. I would guess if you have an EFIS, it's probably correct, but mechanical gauges and their linkages go out quite often.

 

[kiwipete]

Correct setup

Glen

A few things to check.
1) does you prop cable have a little throw left at full fine? ie make sure it doesn’t hit the stop in the cockpit before the stop on the governor and check that the prop cable is in fact hitting the stop on the governor.
2) did you set the prop fine pitch stop. Check the Hartzell manual- this is done to give a max static rpm of approximately 2650 at zero airspeed and stops the prop overspeeding if the throttle is opened rapidly.
3) check the cable security at both ends to make sure nothing has shifted or has excessive play.

Does the prop rpm come back as soon as you adjust the prop lever? Waiting for it to reduce using the throttle may in some situations mean a large reduction in power before the rpm reduces.

Regards Peter

 

[graywoodworking]

Make sure the low pitch is set correctly for the prop. Then if the governor fails the engine and prop won't over-speed. Vic Syracuse had a good article on this and he has a YouTube video as well.

 

[BobTurner]

Make sure the low pitch is set correctly for the prop. Then if the governor fails the engine and prop won't over-speed. Vic Syracuse had a good article on this and he has a YouTube video as well.

This is true only if the aircraft is not moving. See previous post.
But yes: First check the fine pitch stop.

 

[Glen P]

Thanks for the comments, guys. I really appreciate the effort.

BillL - It's an mt-propeller governor.

Full Throttle - I initially pulled the throttle because in another life I flew S2's with great big radials and pulling throttles before pitch was ingrained in me. I need to overcome that.

lr172 - It would normally give me 2660, not 2600. Actually, looking back at Savvy uploads, it would typically be somewhere between 2660 and 2670. Trust me, I am taking this seriously.

D-Dubya - Great idea. I'll do it.

Untainted 123 - Yes it's an AFS 5600 and I believe I'm getting good data.

kiwipete - Yes I'm checking cable connections. The feel when pushing/pulling wasn't as smooth as it could be. I think that might be related to the end of the bolt that connects the cable rod end to the governor arm fowling with a bolt head on the governor at full fine. Today I resolved that with an extra washer under the bolt head. That smoothed out the cable movement. No I haven't made any changes to the low pitch stop.

graywoodworking - I just watch Vic's video. Thanks for pointing that out.

I called Hartzell tech support today. His first thoughts were high elevation or high temperature effects. (Not a factor here.) When I told him that I had adjusted the governor high rpm screw last year in an attempt to increase RPM, he said he thought that could be the root of the problem. Based on his comments, I reversed the change I made last year and flew. Throughout takeoff, climb and several throttle and pitch cycles, the RPM never increased beyond 2740 and it was very easy to achieve accurate, steady RPMs. I'll make an additional adjustment tomorrow to see if I can nail 2700.

Thanks again

 

[kiwipete]

Glen

All the props I’ve set up on RV’s needed 1 1/2 turns in on the fine pitch stop. Please read the Hartzell manual.

Regards Peter

 

[Mikeyb]

I was terrified and agonized over the overspeed limit when I first flew my composite CS Hartzell and IO 360. The low pitch stop was set to 2780 RPM and the governor would regulate at 2690. The only time it would go to 2780 was for one second on a go-around or throttle-up. I didn’t notice it until I looked at the log file.

The way I read it is that a momentary overspeed as defined as less than 3 seconds that is less than 10 percent (2970 RPM) require no action. Mine was a 3 percent overspeed of 1 second.

https://www.lycoming.com/sites/defa...20Engine%20Inspection%20after%20Overspeed.pdf

Hartzell says my prop can go to 110% for 20 seconds. See pic.

One correction of the stop limited it to 2690.

 

[BobTurner]

……because in another life I flew S2's with great big radials…..

Wow, memories! In 1969 I had a summer job at Quonset point NAS where they overhauled S2’s. Not only radial engines, but vacuum tube avionics that got their power from a hydraulically driven generator!

 

[Glen P]

Wow, memories! In 1969 I had a summer job at Quonset point NAS where they overhauled S2’s. Not only radial engines, but vacuum tube avionics that got their power from a hydraulically driven generator!

…and 1500 psi hydraulically powered windshield wipers.

 

[Glen P]

After an additional 2 turns of the governor high rpm screw, I flew today. My EFIS displays RPM to the nearest 10 but after uploading to Savvy, I see that the RPM was in the range of 2684 to 2701 throughout my takeoffs, climbs and high power full fine level flight segments. If I can find a spot to tie down the tail, I'll follow up with a static RPM check for good measure. I also set an EFIS aural warning at 2730 RPM "just in case".

 

[Bavafa]

Glen

A few things to check.
1) does you prop cable have a little throw left at full fine? ie make sure it doesn’t hit the stop in the cockpit before the stop on the governor and check that the prop cable is in fact hitting the stop on the governor.
2) did you set the prop fine pitch stop. Check the Hartzell manual- this is done to give a max static rpm of approximately 2650 at zero airspeed and stops the prop overspeeding if the throttle is opened rapidly.
3) check the cable security at both ends to make sure nothing has shifted or has excessive play.

Does the prop rpm come back as soon as you adjust the prop lever? Waiting for it to reduce using the throttle may in some situations mean a large reduction in power before the rpm reduces.

Regards Peter

Plus one for these steps and comment.

It is not uncommon if your governor is adjusted for 2700 RPM and then see slightly higher RPM on a go-around for a short duration. The governor will take a half a second or so to catch up to control the RPM. This is why it is good and important to setup the mechanical stop which is the center nut/bolt on the prop. You probably only need a 1/4 to half a turn on that.

 

[Draker]

Plus one for these steps and comment.

It is not uncommon if your governor is adjusted for 2700 RPM and then see slightly higher RPM on a go-around for a short duration. The governor will take a half a second or so to catch up to control the RPM. This is why it is good and important to setup the mechanical stop which is the center nut/bolt on the prop. You probably only need a 1/4 to half a turn on that.

Good reminder. After my earlier prop governor drama, I never went back and adjusted my pitch stop on the prop. I've always had to slowly increase power, otherwise the prop would surge to ~2740-2760 for a half a second or so until the governor caught up. Very easy job. My prop manual describes how much to turn it per x00 RPM you want to adjust.

 

[Taltruda]

I would second (or third) that the better way to address this issue is to start with the low pitch stop under the spinner. The hartzell manual and whirlwind manual describe the adjustment. Just using the RPM screw on the governor should be your last step after adjusting the prop. If you make the prop governor control the takeoff RPM, you’ll get surging and reduced glide when you power back to idle..

Basically you back off the governor screw so the governor isn’t limiting the RPM. Then after removing the spinner, loosen the 9/16 nut in the center of the prop, and turn the Allen head screw clockwise (Hartzell). One full turn is 200 RPM, or each 90 degrees is about 50 RPM. Put the spinner back on (so you don’t damage the tabs behind the blades from centrifugal force) and check your max RPM statically in the runup area. ( make sure you have flaps retracted, as it could lift the tail). You want the prop to be limited about 2650 statically. Then go fly and adjust your blue knob to 2700 at cruise speed. Leave the knob there while you land, then adjust the governor screw to just touch the lever.

 

[AlexC]

Make sure the low pitch is set correctly for the prop. Then if the governor fails the engine and prop won't over-speed. Vic Syracuse had a good article on this and he has a YouTube video as well.

Exactly. This should have been done prior to first flight.

 

[Glen P]

Make sure the low pitch is set correctly for the prop. Then if the governor fails the engine and prop won't over-speed.

I did the static RPM check today and got 2681 to 2686. I called Hartzell tech support for feedback because I had read somewhere that you should aim for 2650 to <2700. He said you should aim for >2650 and in his opinion 2680 is "perfect". Hearing that, I decided not to tweak the low pitch stop.

Thanks again for the very useful comments.