Rear mount prop governor access

Big Ed

Big Ed

N50247 - '79 Super D
Joined
Jul 20, 2020
Messages
1,938
Location
Tampa, FL
My '78 Decathlon has an AEIO-360-H1A engine, which has a rear mounted prop governor. I need to check the oil inlet screen. Is that reasonably accessible? How?

As an aside, I looked at 3 more recent Decathlons, all ACA vintage from 2000 or later. They all have the governor mounted in front of the left forward cylinder.
 
They went to the front mount governor, I forget when, but the rear mount is a-ok. When I was on the hunt for an engine I asked Pat at ACA about it and he vouched for the rear mount as perfectly fine, just different to work on.

If you're in there working on things would you mind posting a pic of the "dog bowl" and where it's located? That's the metal bowl shaped recess they used in the firewall to let the governor protrude through. I bought ACA's last one when I was out there last year but have to cut my firewall to mount it at some point. Thanks!

Don't know about the screen. Sorry! :LOL:
 
Here's a pic of the dog bowl. I suppose if I pull it off, I'll see the governor and be able to access the screen?

PXL_20211107_162959693 (2).webp
 
Here are two more views. Looks to me like removing the dog bowl would be a PITA. First, the top lip appears to be trapped against the firewall by a horizontal frame member. Second, they used tinnerman nuts instead of nutplates. Third, there is some kind of line, probably oil, coming into the top of the bowl.

However, it also looks like that round cover secured by a single center screw might be a removable access plate. So maybe if I pull that off, I will magically see the oil screen. I'll find a parts diagram of a Woodward governor.

PXL_20210404_212855657 (2).webp

PXL_20210404_212846334 (2).webp
 
Edit: quick scan of photos suggests the line into the top of the dog bowl is the control cable.
 
As best I can tell from research, the "oil inlet screen" is a screen molded into the gasket that mounts the governor to the drive adapter. If that is the case, I am not going to monkey with it.
 
I could see maybe if you had a problem with metal in the engine oil or some kind of a prop control shortcoming that you were investigating but probably not in the course of regular use?
 
Bartman said:
I could see maybe if you had a problem with metal in the engine oil
Click to expand...

This. Engine is making metal. A pinch of very fine iron filings in last several oil changes. This is not a surprise given the history of the engine. I expected to get a few hundred hours before the lifters spalled and the cam lobes started wearing, which is exactly what I got.

My A&P/IA was surprised by the quantity of the most recent change last week. This is the first time I have carefully measured quantity by rinsing the screen in mineral spirits and then straining through a coffee filter. But he did not go so far as to ground the plane, just saying we needed to investigate and that I should start planning for an overhaul soon. I was already there.

I showed the Zephyr guy the metal and he said yep, gonna need an overhaul soon, but it won't fall out of the sky or anything, it will just gradually lose power and climb rate.

I showed the JB Engines guy the metal and he put the fear of God in me. He said that a spalled lifter could lose a chunk from the edge, which would trash the case. He also said that the iron filings would score the crankshaft so it could not be reground, costing me $7K for a new crank. He said I should have my mechanic pull the left rear cylinder and look at the cam lobes before flying it again.

My inclination is to ground the aircraft now, pull off the engine this weekend, and take it to JB next week. That gets it in the queue at his shop, with a good chance of having it back for the fall acro season.

OTOH there are only 3 contests within reasonable flying distance, and one of them is 2 weeks from now in Rome, Georgia. Right now I am flying well, so I think I would have a good chance of placing. I was toying with the idea of trying to make the Rome contest before pulling the engine. But that would involve 6 hours of XC and an hour or two of acro.

Sooooo ... I was researching ways to better quantify how much risk I am at for trashing the engine. Found some sources that suggested inspecting the prop governor screen. If there is metal at the governor, then metal has reached the crank and I should ground the aircraft immediately. If not, then maybe it won't get much worse in 6 hours.

Right now I'm 99% decided to ground the aircraft today and get the overhaul started. But the Sebring trophies sucked, and the Rome trophies look really nice! :unsure:
 
Ok.
The screen in the governor gasket is pretty coarse...it's job it to keep chunks out of the governor gears. If you have iron filings ( little hair type pieces) in a spin on filter you either have a stuck piston ring scrubbing or a camshaft worn past the hardened wear surface and shedding metal. These tiny filings would pass right through the governor screen. The lifters usually make tiny flat chips as they come apart...
In either case if the metal has made an appearance thru multiple oil changes its time to get it worked on; it can only get worse and more expensive from here.
JMPO

Chris
 
Last edited:
new engine is pushing $70,000 and if your parts become unusable you won't easily find replacements. i got really lucky having a case and paperwork plus scoring a new crank for mine. a new engine is probably minimum six months out from now.

there are completed projects out there still waiting on engines, don't let yours get worse.
 
Hiperbiper said:
Ok.
The screen in the governor gasket is pretty coarse...it's job it to keep chunks out of the governor gears. If you have iron filings ( little hair type pieces) in a spin on filter you either have a stuck piston ring scrubbing or a camshaft worn past the hardened wear surface and shedding metal. These tiny filings would pass right through the governor screen. The lifters usually make tiny flat chips as they come apart...
In either case if the metal has made an appearance thru multiple oil changes its time to get it worked on; it can only get worse and more expensive from here.
JMPO

Chris
Click to expand...

great post Chris, thanks for that!
 
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