Governor adapter plate
Update: This is required reading for all Cardinal owners with a -D engine, and should be for other aircraft types with a -D Lycoming as well (Maule, Mooney, ...) as they share the same issue.
Some owners have recommended that this page be printed and inserted into aircraft logs or maintenance papers in hopes that everyone replacing the governor be certain to know about this critical detail!
There have been a few situations where a Cardinal has lost a great deal of oil shortly after departure after the prop governor was changed. Here are pictures of the governor plate and gasket along with a little information about this issue and how to guard against it.
Note that only the -D engine (with the dual Bendix mag, not the separate magnetos) is affected by this issue. The engine with separate magnetos is not affected by this issue. The affected aircraft (those with a single 'combo' mag unit) include the later years of the Cardinal RG, but not the very early ones or those which have been converted back to the older engine.
How big of a problem is this? Since CFO has been in operation (1997) we have seen this issue come up as an in-flight issue at least a dozen times. Our estimate is that for a period of time, half dozen airplanes a year are put together without the proper spacer and gaskets (update: now fewer since the SAIB has been published, we've been talling the story for 15 years and owners are paying attentiont to this.. good work owners!) How many of those fly depends on how well we get the word out. As an average across time, perhaps 1-2 Cardinals a year have experienced an in-light engine failure as a direct result of this problem.
This page was originally written in 1998 and has been modified to add the many stories which have unfolded from this issue. You will find those stories at the end of this page. Perhaps most compelling is the story of Carl Johnson who had a very bad day due to this issue. You can read the whole story at this page.
As word gets out about this issue it is more frequently being detected on the ground rather than in flight. Unfortunately it is often the operator who detects the issue. In many cases these pilot-owners find that they need to strongly insist on further research and bring in their own documentation before well-meaning mechanics accept the requirement for this spacer/adapter plate.
Our friends at the FAA have been looking into this situation, contacted us in mid August as part of their research and on 11/9/2005 published SAIB NE-06-08 on this issue. We applaud this effort! This also led to clarification of one remaining mystery.
(Note: Early versions of this document identified one affected airframe as the 'Cardinal R-6', a small typo which should be Cardinal RG. The FAA updated the on-line SAIB and was able to catch this before printing, so only folks who pulled an early copy from the web site will see this issue.)
As part of the research done for this SAIB we learned that the critical attribute of the plate is it's thickness. The length of the shaft protruding from the governor is such that it can bottom out in the spline inside the engine, causing the bolts to torque up due to shaft bottoming rather than sealing the gaskets. In this situation the gasket will leak, a little at first, then eventually blow out and dump the oil.
So while for many years we thought the problem was that certain ports were uncovered, in fact the problem is in the bottoming of this shaft. It's good to finally know the whole story. Curiously, at least one mechanic was of the opinion that more gaskets made things better. If you have sharp eyes you can see three gaskets in the picture above. Turns out he was right!
Once you've read about the story, check out
the mechanic's viewpoint. (membership required) (For the non-members reading this, the link leads to a rather sad story from a mechanic who didn't know about this plate until a certificate action was brought against him for failing to install one, leading to a crash. He set out to find the information he was suppose to have known and did find it, but the references were remarkably obscure and difficult to track down. The eventual impact to his A&P license was still unknown at the time he shared his story with us.)
Let's run this down from the owner's perspective. This story starts with a dawning realization that there has been a problem, edited for brevity...
From: rick dobbins
Subject: recent accident
Hi fellow Cardinal drivers
My partners and I recently purchased a 1975 177RG
N2679V. I have been enjoying this site and have really
gotten some useful tips on the nature of the Cardinal.
On Sept. 5, I was enroute to Saint Simons
Island, Georgia from Atlanta when I lost complete oil
pressure followed by complete engine failure and had to
execute an emergency landing. I was very fortunate in
walking away without a scratch.
I just got back
from the initial engine inspection with the FAA and my
insurance company where we tried to determine the reason
for the engine failure. The week before
the last flight we had the prop governor overhauled. My
A&P did a test run up as did I before the flight.
very conscious of watching the oil pressure gauge during
initial start up, taxi, normal run up and climb out. 15
minutes into the flight I noticed very low oil pressure
and alerted Atlanta approach (I was on flight following)
that I had a problem.
soon started to sound rough and I declared an emergency. I was 10
miles from Covington, GA airport when the problem arose
and was within 2 miles of the field when the engine tore
lose. I was a glider at that point and put it in the
During the initial inspection, the case was found to
have several cracks in it as well as a hole the size of
a fist below jug #1. There was about a quart of oil left
in the sump - full of metal. We took the #1 & 3 jugs off
and found #3's connecting rod to be discolored. Bits and
pieces of metal were all over the inside of the engine.
The prop gov. was removed and its shaft was locked up
with metal all around the screen area.
Could the prop gov. be at fault?
It is hard for me to believe that this was
just a coincidence.
Atlanta, Georgia N2679V
We wrote Rick a note and suggested that this was the normal failure mode for 'no adapter/spacer plate'.
From: rick dobbins
Subject: recent accident-prop govenor
I called the A&P who did the initial breakdown on
Tuesday for the insurance company under the supervision
of the FAA and confirmed that there was no plate
installed along with the gasket! The gasket #MS914401
was present but no plate. |
My A&P insists that there is no documentation in the
engine or airframe manuals that says a plate is required,
and that there was no plate when he took the governor
off the engine.
However I have a copy of Lycoming's service instruction
# 1438 dated July 9, 1987 stating that ALL 4 & 6 cyl.
dual mag engines with rear mount govenors must have this
[It's a trap... the plate can look like a discardable
gasket upon disassembly, and unless you have the service
bulletin (or the SAIB) there's no data that points out that the plate
belongs. Every -D engine owner owes it to himself and
his airplane to become savvy and involved on this issue
whenever the governor is removed/installed. Paul]
Rick Dobbins 177RG N2679V
The images along the right side of this page show the governor base plate between
it's two gaskets under an installed governor on an IO-360A1B6D
installed on various later model Cardinal RGs. The pictures are taken from near
the area of the oil fill tube. Note the oil filter above the
governor and the prop oil line in the lower right corner in the picture above. If you're sharp you may notice that one of the aircraft in these pictures actually has *three* gaskets installed!
If you are having trouble seeing the plate just look for the shiny metal edge. This plate can be usually seen through the oil filler door with the cowl in place. (You will need a flashlight.)
From: marc (firstname.lastname@example.org)
Subject: Prop governor gasket-a problem!
I have had this problem and have made it my business to
remove and install my own governor anytime! I received
an overhauled engine from the shop with the governor
plate missing and the gaskets incorrectly placed! Dumped
the oil on start up test!
This is a common error with
A/Ps unfamiliar with D engines as the Lycoming manuals
and parts book do not show it and neither does the Cessna
parts book! Only the service letter guides.
More stories below...
Clarifications from the Webmaster:
There are a lot of different prop
governors on the market, a lot of different engines
and a lot of different props. They fit together in various
combinations, but there are so many possible combinations
that manufacturers take advantage of any possible similarities
to reduce the required number of models.
For instance, a governor may work the same on several different
engines, but the oil may come from a different location on the
governor pad in each of these engines. This is compensated for in the design of the governor, which
will have several ports to accept oil from different locations
on the pad.
But what happens to that alternate port when on the engine that doesn't use
it? If the designers are lucky it comes up against a flat, empty spot on the
pad and is effectively closed off. If not, some form of adaptor is required
to assure that oil goes only where it should.
Note that in the pictures above the gasket has a large passage just
above center, at the top of the gasket. Note that the plate, pictured
below, does not.If you forget the plate, whatever hole that gasket hole lines up with
does not get blocked. As you can see in these photos, the plate helps with
closing off certain ports and opening others.
The lower image to the right, without the hold in the upper center, is the spacer plate. It is .040 thick and is made of steel.
Turns out in the Cardinal, and other aircraft with this engine/governor combination, there is an additional issue for compatibility: the depth of the hole where the governor spline slips in. The shaft is just a bit too long for the hole it fits into, and can bottom out in that hole.
Thus this plate adds not only oil flow control but also a little thickness to the assembly. Without that additional thickness, depending on the stack-up of tolerances in the assemblies, there is a good chance that the mounting bolts will torque down on the bottomed-out shaft rather than with pressure on the gasket. This allows the gasket to leak, a little at first, then more as the high pressure oil blows out the uncompressed gasket material.
This explains why this issue may not show up at first, or may result in just a slight oil weep at the governor base. Once the gasket blows out, the excellent oil pump which is the governor will quickly remove all oil from the engine, resulting in in-flight engine failure.
I know this was an issue of some interest for me when I overhauled my own engine, and it would have been easy to forget that plate on reassembly. As the stories on this page attest, this is one area where the pilot should take a personal interest. The last 200 engines he worked on may not have required this plate.
Keith Peterson, Webmaster.
Here's a testimonial from a satisfied reader:
Keith, We finally have 7555v back flying after having the engine overhauled
by Jewell (Holly Springs, MS). The engine turned out great.
However, (thanks to the Cardinal web site) we discovered a humongous oil leak at the prop
governor. Guess what?? no plate was installed on the governor!!
An excellent way to check for leaks in this area is to set 2400 rpm (on the ground) and
then pull the prop back to 2000 rpm. This will increase the oil pressure in the gov. to almost maximum and, as in our case, will cause a real flood at the mounting pad if all is not correctly installed.
[Webmaster's note: Read on for stories of people who flew for many hours without the plate before suddenly losing their oil. Depending on the tolerance stackup, an installation without a plate may leak immediately or only eventually. His point is a good one, though: Normally there is little oil pressure going to the prop on the ground. Only during high-power prop cycle does substantial pressure exist, and full pressure will occur only in flight.]
I shudder to think what would have happened if we had flown a 2-3 hr. trip with a leak that size. The Gov. plate was installed free of charge (and with apologies) and now everything is tight and dry.
Thanks again Keith for all the great info.
Update 7/2003: Unfortunately this remains an ongoing point of discussion. Here are a few more stories of followup since this subject was first brought up here:
Carl Johnson had a bad day that appears to have been caused by this issue. You can read the whole story at this page.
From: "Bryan Sieve"
You can ask even tell them about it but it doesn't mean it will get done.
You owe it to your self to personally verify this one! Our story...
Shortly after acquiring our timed out '77 RG in 2002, we had the engine
rebuilt by Crystal Shamrock in Minneapolis (KMIC). At the conclusion of the
overhaul and somewhat recalling the CFO article on the prop governor, I
causally asked the A&P who rebuilt the engine about the prop governor plate
to which he replied it was installed. Satisfied we re-took delivery of our
airplane with its newly overhauled engine and began the break-in process
which used oil pretty much at the stated breakin rate but was otherwise
uneventful except for some new oil staining the hangar floor. However, at
50 hours the engine continued to use oil and there was continued oil
dripping out of the cowl and staining the hangar floor.
Looking for the source of the leak, we personally removed the cowl to
investigate and noticed oil on the bottom of the prop governor. Suspicious,
I re-visited the CFO article, printed it off and brought it to the
attention of the shop. They somewhat snubbingly told me it wasn't needed,
but if it was there in the first place it would have been re-installed.
They then agreed to personally "show" me where it was installed and
otherwise find the source of the leak. Well guess what... NO PLATE! After
expressing my displeasure to them (in many creative and imaginative ways) the
plate was promptly ordered (couldn't locate the original) and installed at
no charge. The oil usage went away and the hangar floor is again dry.
Morale of the story is print the CFO article off (complete with
consequential stories) and bind it into your service manual. Better yet
laminate and paste it onto the firewall for all to see and be reminded of.
Best Regards, Bryan Sieve '77 C177RG N50457 KMIC Minneapolis, MN
Subject: Cardinal bit the dust & adapter plate
To reinforce this to help avoid others having a similar problem, here is my
After replacement of my camshaft my first flight was circling the airport
at 2000 ft for about 30 min. All went well and nothing unusual noted.
The next morning there was a puddle of oil under the plane. The A&P who
installed the engine was baffled but I vaguely recalled something about the
governor on the CFO website. I did not know as much then as I know now, and
did not have a list of items to check on the engine installation. Sure
enough, when I got home and checked the tech section, there it was, the
The very experienced engine rebuilder did not believe me about the adapter
plate until I gave him both the printout from CFO and a copy of the SB.
I hope this gives enough visibility to the issue that everyone checks for that adapter
plate after any engine work that involves the governor and that everyone,
regardless of engine type, stays in the vicinity of an airport on the first
flight (AKA test flight) after major work.
Stories keep coming in... this one since the SAIB hit the streets:
From: Tom Sweeney
Keith, I'm not sure that you're the one to whom to write but I just read the article on the governor spacer and wish I'd known earlier. I have a story too but in a
Mooney. The week after 9/11 IMC over the Virginia mountains I had a complete engine failure. Made a safe landing at New River Valley but got stuck with the $22,000
replacement engine for one that had had only 500 hours. No damage, no insurance, no FAA interest (busy with national security).
I immediately inquired about the governor and no one, no one (I repeat) thought the governor just reinstalled could conceivably be the problem! I spoke with Lycoming
folks several times. No help there either (They did study the engine and simply said it was due to oil deletion – like I didn't know) They did give me a waiver on the
replacement core for which I am grateful but I never felt they were truly forthcoming. Now I have even more reason to wonder. I also believe the mechanic botched the
job as the same problem showed up when he installed a subsequent governor and I caught it. Took the plane to a different shop to fix it but nothing about a spacer there
Normally I always fly VFR after maintenance but due to the first flights after 9/11 no one was allowed to fly except IFR. It only took 55 minutes to lose all my oil. IMC,
multiple altitude, frequency (difficulty even getting acknowledged and only cleared to NDB 2.5 miles from the airport on take off!), and directional changes = missed
engine gauge drop. Nine month hassling Lycoming so no flying then (area Lycoming distributor assured me it was a connecting rod failure and Lycoming needed to own
up to it).
I am grateful to be alive. I hope your website helps save others from all this.
These pages are a collection of the ideas and impressions of the Cardinal pilots who frequent this site. This information is anecdotal, informal and may not be completely accurate. The Cardinal Flyers are not certified mechanics and do not guarantee the accuracy of the contents of these pages. Please research and confirm anything that is referenced on these pages with the experts appropriate to your situation.
As always, the Cessna maintenance, operations and flight manuals, and the advice of a certified mechanic and flight instructor, should be your primary sources of information regarding safe maintenance and operation of your aircraft.
Copyright Cardinal Flyers Online LLC 1997-2020