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Prop governor problem


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I have a 67C with a prop governor issue I can't make sense of. (at least that's what I think it's going to be)

 

Everything is normal around 2450 and up, but anything I try to get below that just drops well below 2000. Even just the slightest tickle of the control does this. 

I'd expect most failure modes would show themselves in the prop speeding up....

 

Ideas?

Edited by chriscalandro
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My idea would be to call in the help of a bonafide prop guy...

We might have one of those guys around here somewhere...

Sending a signal to @Cody Stallings....

Sounds like a governor challenge of some sort... possibly affecting the control valve and fly weight operations...

PP thoughts only, not a mechanic.

Best regards,

-a-

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Sounds like maybe a Sticking pilot Valve or a speeder spring has lost its tension(or broke).

Something at a certain spot is allowing the oil to flow ungoverned to the Propeller.

Anyway you look at it, I would wanna get that fixed ASAP.

Also, when the gov takes control of the Propeller to said RPM, are you seeing a drastic drop in engine oil pressure that sustains?

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I ran it up on the ground today, oil pressure normalizes when the rpm gets to where it decides it wants to go. 

 

I have a call into Texas aircraft prop and accessories who gave some reasonable estimates for replacement and overhaul. 

(800/1700)

 

I'm thinking I just go with replacement and be done with it. I think the downtime mixed with the odds of it being serviceable being questionable make the decision easy...

 

The important bit is that everyone says prop governor and not something else. Most likely a flat spot in the flyweight or bad springs. 

Edited by chriscalandro
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37 minutes ago, chriscalandro said:

I ran it up on the ground today, oil pressure normalizes when the rpm gets to where it decides it wants to go. 

 

I have a call into Texas aircraft prop and accessories who gave some reasonable estimates for replacement and overhaul. 

(800/1700)

 

I'm thinking I just go with replacement and be done with it. I think the downtime mixed with the odds of it being serviceable being questionable make the decision easy...

 

The important bit is that everyone says prop governor and not something else. Most likely a flat spot in the flyweight or bad springs. 

This was my exact line of reasoning when I decided to just put a PCU5000 in. Shop swapped out the governors, no downtime, and I was able to sell my old one as a core and recover $175 for it.

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53 minutes ago, carusoam said:

The PCU5000 seems to be the modern replacement... for many.

PP thoughts only, not a mechanic...

Best regards,

-a-

Shop didn't have the parts to build an A1 so PCU5000 it is. Mechanics round here are busy and getting one for a day is twice as easy as getting one for two days separated by a week!

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  • 2 weeks later...

For what it's worth, we shipped our ancient Edo-Aire governor to Truespeed Aero Governors in Van Nuys this week for IRAN (we were referred to them by LASAR).  When they found it un-economical to repair, they recommended the McCauley over the PCU5000.  They're starting to get some PCU5000s in for overhaul and apparently there is a wear component (some sort of "pin") that is only available from the manufacturer, at a cost of over $700.  They expect McCauley parts to remain available for the forseeable future, at lower cost.

EDIT: the "pin" I reference above is actually an idler arm, and the story is slightly complicated, see my follow-up post below: https://mooneyspace.com/topic/28821-prop-governor-problem/?tab=comments#comment-486152

 

 

Edited by Vance Harral
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Have fun swapping out the studs @chriscalandro.  I did it in the Alabama heat of July last year and damn near got heat stroke.  Hope you are in a warm spot this time of year or have access to a heated hangar.   Mistakes to avoid: putting studs in wrong side out, putting studs in too far.  

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Old is off, new is on. I definitely almost put the studs in wrong side out. 

My problem now is that it came with an angled piece to mount the cable, and with that I can't come up with a configuration that covers both stops. None of the documentation shows this angled bracket. I'm pretty sure I'm better off without it but that means I need to take the mount for my cable back off to fit the bolt on the cable through...

 

A project for later in the weekend...

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On 1/21/2019 at 2:26 PM, Skates97 said:

This was my exact line of reasoning when I decided to just put a PCU5000 in. Shop swapped out the governors, no downtime, and I was able to sell my old one as a core and recover $175 for it.

So you like the PCU 5000? Was talking to Prop shop yesterday about overhauling mine or just upgrade...

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  • 2 weeks later...
On 1/29/2019 at 6:42 PM, Vance Harral said:

For what it's worth, we shipped our ancient Edo-Aire governor to Truespeed Aero Governors in Van Nuys this week for IRAN (we were referred to them by LASAR).  When they found it un-economical to repair, they recommended the McCauley over the PCU5000.  They're starting to get some PCU5000s in for overhaul and apparently there is a wear component (some sort of "pin") that is only available from the manufacturer, at a cost of over $700.  They expect McCauley parts to remain available for the forseeable future, at lower cost.

I was contacted by the folks at Truespeed today with a clarification to my statement about a "pin" wearing on the PCU5000.  Truespeed says:

The component in the PCU5000 which you referred to as a pin is actually an idler stud. In this type of governor, this stud also serves as the relief valve body. The idler bearing which is in the idler gear, turns on this stud and eventually there is wear on the stud. So, unlike in other governors where an authorized Repair Station would remove and replace a stud when it is worn, the PCU5000 manufacturer specifies that the governor must be returned to the factory and they would replace this stud. Naturally this is not a free service, and there is a substantial cost for this, not to mention the additional time and freight that would be involved.
 
All governors have their pros and cons. In the end, when the time comes, it is up to the owner to decide which governor to go with, but this choice should be made with a reasonable knowledge of what to expect when it is time for repair or an overhaul. A good governor repair station should be able to advise their customers about this.

I sincerely appreciate the follow-up from the shop on this.  Truespeed carries the PCU5000 and they think it's a good governor, arguably best in class for those who don't mind paying a little more for new vs. an overhauled McCauley or Hartzell.

On a related note for those interested, our overhauled McCauley governor is installed and working well after about two hours of test flying.  However, we did run into a bit of a snafu during installation.  Our installation uses bolts rather than studs to attach the governor, and the housing of the McCauley differs from that of the Edo-Aire in such a way that it's difficult to get the bolts inserted - the head of the bolt interferes with the governor housing on the way into the mounting hole.  Seems like there's always some complication when you don't replace exactly like-for-like, not even when the replacement part is on the TCDS.

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