Prop governor (PCU5000 ATH-1) adjustment vs. prop fine pitch stop adjustment

[DXB]

I'm working with a fresh O360-A1D overhaul. I had the 12 year old Hartzell Scimitar resealed and painted at the same time. It makes it to about 2640 static rpm, which is normal I think.  However RPM at takeoff / climb isn't any faster than that.  JPI digital tach.  The PCU5000 governor was carefully installed with the cable pushing to the full stop of the arm on the governor.

Is this a governor adjustment or a prop fine pitch stop adjustment to get to 2700?  If the former, how is it done?  I've been searching for PCU5000 manuals online but have come up blank. Can someone supply one? 

BTW, behavior was pretty similar before overall and prop reseal....engine overall was a good albeit costly experience in general - will post a full pirep later.

[EricJ]

Sounds like the governor high speed stop adjustment, but, like you say, that's not bad.   My new governor works about like that and so did the old one (neither is a PCU).

[47U]

1 hour ago, DXB said:

Is this a governor adjustment or a prop fine pitch stop adjustment to get to 2700?  If the former, how is it done?  I've been searching for PCU5000 manuals online but have come up blank. Can someone supply one?

https://cdn.prod.website-files.com/648893d6ed845c1087937b37/648893d6ed845c1087937c06_INSTALLATION-GUIDE.pdf

Here’s a screenshot…

[DXB]

38 minutes ago, 47U said:

https://cdn.prod.website-files.com/648893d6ed845c1087937b37/648893d6ed845c1087937c06_INSTALLATION-GUIDE.pdf

Here’s a screenshot…

Exactly what I needed.  The drawing is a bit inscrutable, so I'm adding a pic here for reference.  I suppose if rpm doesn't increase with this adjustment, the fine pitch stop on the prop is limiting...?

[47U]

11 minutes ago, DXB said:

I suppose if rpm doesn't increase with this adjustment, the fine pitch stop on the prop is limiting...?

Presumably… if an adjustment on the governor high rpm stop doesn’t get you to 2700.  Adjusting the limit stop is a counter-clockwise turn on the stop (screwing it out) resulting in more travel on the arm, so I think you’ll get there.  Otherwise, that’s maybe a question posed to Cody Stallings… 

[EricJ]

Usually one is hesitant to adjust the fine pitch stop on the prop, since it is usually a last resort and probably indicates something else is wrong.   It is possible to do, though, and is allowed to do.   It's usually worth exhaust all other possibilities first.  The high-pitch stop usually only affects ground operation, since it will be expected to come off the stops and start governing during the takeoff roll. 

The high-rpm stop on the governor will likely correct it, and if it doesn't, triple or quadruple check your rpm measurement standard.   You should already be using an accurate optical tach or similar.   Mechanical tachs have a fair amount of tolerance in what they indicate, and some electronic tachs and others also may have tolerances at or near the amount of error you're indicating, which is less than 2.3%.

 

[Pinecone]

Needing to adjust the low pitch stop may also indicate that your engine is not producing full rated power.  Like a static RPM check with a fixed pitch prop.

So I might get a prop shop involved to see if it is set to what it should be.

[DXB]

11 hours ago, Pinecone said:

Needing to adjust the low pitch stop may also indicate that your engine is not producing full rated power.  Like a static RPM check with a fixed pitch prop.

So I might get a prop shop involved to see if it is set to what it should be.

Kinda what I suspected as the same thing was happening when I found metal in the filter before overhaul.  Now the engine is just off the test stand making full power after overhaul, and the behavior is nearly identical, so my money is on the governor setting. I had the prop resealed at the same time by a good shop, and I doubt they set the low pitch stop too high.

[A64Pilot]

Easy to rule out the pitch stop, if it’s the pitch stop she won’t get the RPM on the ground but easily will in the air, especially at higher speeds.

If I were getting 2640 I’d be tempted to leave it alone if the governor were a pain to adjust, mine in fact turns about that now and as I only have the stock tach, it might be 2700 or even 2600, who knows, they aren’t super accurate.

Edited November 22, 2024 by A64Pilot

[Pinecone]

Get a digital tach off Amazon and check the actual RPM.

The problem with low RPM is that your engine is not making rated power during takeoff.  So all those nice tables in your POH are no longer valid.

 

 

[PT20J]

My governor was about 2660. I tweaked it because it bugged me, but according to the Lycoming IO-360 power charts, 40 rpm is only about 3 hp. On a McCauley governor, on turn of the screw is about 25 rpm.

[Ragsf15e]

46 minutes ago, PT20J said:

My governor was about 2660. I tweaked it because it bugged me, but according to the Lycoming IO-360 power charts, 40 rpm is only about 3 hp. On a McCauley governor, on turn of the screw is about 25 rpm.

One annoyance with my edm-930 is that it flashes a red warning if my rpm hits 2700 as that’s the “redline”.  Luckily my prop generally hits around 2660-2680 usually, but I dislike getting warnings from something that’s actually a good thing (2700 rpm) during takeoff.  They should have better logic built in.  
 

What does your g3x do?

[PT20J]

1 hour ago, Ragsf15e said:

One annoyance with my edm-930 is that it flashes a red warning if my rpm hits 2700 as that’s the “redline”.  Luckily my prop generally hits around 2660-2680 usually, but I dislike getting warnings from something that’s actually a good thing (2700 rpm) during takeoff.  They should have better logic built in.  
 

What does your g3x do?

The G3X EIS is highly configurable for gauge ranges and alerts. It has lines (red, yellow, green, cyan, white), ranges (red, yellow, green, cyan, white) and range + alert (red, yellow).

Only the yellow range + alert and red range + alert will generate annunciations. I connected the red range + alert and yellow range + alert to the PMA 450B so that yellow will annunciate an audible MASTER CAUTION and red will annunciate an audible MASTER WARNING in addition to displaying a message on the G3X PFD. (The connections are just active low outputs designed to operate an external lamp, but the PMA 450B will sense them and provide the voice annunciation).

On the tachometer, I marked the instrument as specified in the POH, but did not set any alerts. I figured any significant overspeed would be pretty easily detectable and wanted to avoid spurious alarms. 

[PT20J]

3 hours ago, PT20J said:

The G3X EIS is highly configurable for gauge ranges and alerts. It has lines (red, yellow, green, cyan, white), ranges (red, yellow, green, cyan, white) and range + alert (red, yellow).

Only the yellow range + alert and red range + alert will generate annunciations. I connected the red range + alert and yellow range + alert to the PMA 450B so that yellow will annunciate an audible MASTER CAUTION and red will annunciate an audible MASTER WARNING in addition to displaying a message on the G3X PFD. (The connections are just active low outputs designed to operate an external lamp, but the PMA 450B will sense them and provide the voice annunciation).

On the tachometer, I marked the instrument as specified in the POH, but did not set any alerts. I figured any significant overspeed would be pretty easily detectable and wanted to avoid spurious alarms. 

The fact that the yellow range and yellow range + alert can overlap is something I found useful on some gauges. For example the lower yellow range on the oil pressure gauge is 25 - 60 psi. And the lower redline is 25 psi. It's permitted to dip into the yellow arc during idle and my engine goes down to about 55 psi at low idle when the oil is warm. So I set the yellow arc to  25 - 60 psi and and the yellow + alert to 25 - 50 psi. 

[phxcobraz]

I still have the factory governor on my C and only make about 2640 as well. I had it adjusted a few years ago, as it was initially only making 2500 when I bought it. They got it to 2640 at basically the end of adjustment of the high speed stop adjustment.

I figured 60rpm off was close enough and I haven't messed with it since.