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CS Propeller Agony

Bayou Bert

Well Known Member
My RV9A "Pearl" now has 13.9 flight hours in Phase I.
From the very first lift off, the prop has surged and was still
doing it yesterday when we flew.
Info on plane
Engine: O-320-D2G with FI
Starting Governor: MT P-860-4 and was not one in the batch with problems.
Prop: Hartzell C2YL-1BF/F7663-4

What has been done so far:
Governor
The governor was a new MT put on the engine when it was build.
When the problem started (first flight) I removed governor and sent to
MT in DeLand, FL. The replaced a spring and polished a shaft and said
the governor met MT requirements.
Re-installed and found no difference.
Then friend had a rebuilt Woodward which was installed.
No change on the RPMs surging.

Prop
Prop was purchased (rebuilt) for a Northwest coast prop shop in 2014.
When problems started, prop was removed and taken to a reputable prop
shop in the Houston area for a quick check. Static balance was off slightly
and corrected then on the bench, air applied and all angles etc checked.
When I left, prop met Hartzells specs.
Since then prop was dynamic balanced with final reading of .05.
The static stops on the prop are set so that at full power on the ground
RPMs show 2650/60. Two tacks, checked to be correct during prop
balance and found accurate.

First chart is the first 50 seconds of takeoff showing MAP in orange and
RPMS in Blue.
Software takes a shot of data twice each second so distance from dot
to dot is one half a second.
Notice the big sag, sure gets your attention on take off.
On All charts, RPM scale on left, MAP scale on right.



Second chart is at 3500' then setting up 25/25, then moving the throttle
around to see RPM response. Notice RPM does not go back to exactly 2500
between moves



Third chart shows later in flight at 2400 RPM and me reducing the throttle and the RPMs going up!



I am now to the point I don't know what to do next. This is taking a bunch
of the fun out of Phase I having to worry about the engine/prop all the
time. This is the first CS prop I have flown behind. The person who has
flown several flight for me is a 30+yr A/P, IA and has thousands of hours
in everything from Cubs to Gulfstreams and he says he never seen one
behave like this one.
Sooooo.....that's the story to this point.
ALL...comments, questions, suggestions more than welcome.
 
It takes a bit of effort, but my recommendation is that you do the leak-down test described in this SERVICE INSTRUCTION

The results of that test will allow you to confirm whether or not the problem is related to the engine or propeller. If not, then you know it is related to the gov.

I have seen this be an engine problem a couple of different times. One was because of a removable plug that was left out of the nose section of the engine case.
Anything that causes oil to leak from the nose bearing section of the engine at a higher rate than is expected can cause propeller / gov. problems.
 
How is your oil pressure behaving? It may be helpful to see how the oil pressure behaves relative to the RPM and manifold pressure.
 
Oil Pressure and RPM

Blue RPM Left Scale
Orange Oil Pressure Right Scale



I don't see a problem here but I am not trained in CS stuff.
 
Fine pitch stops

Bert

The first thing that stands out to me is the fine pitch stops need coarsening up. You shouldn't be able to get anymore than 2650 static rpm. This is causing the surge on takeoff, as the governor is not quick enough to catch the over speed. The props I've setup all required about 1 1/2 turns to coarsen.
If you go too far it's ok but you'll notice the rpm will increase slightly during the takeoff.
To check the static you either need to open the throttle rapidly to see the maximum rpm before the governor has time to catch up or adjust the governor speed to 2700 rpm then keep adjusting the fine pitch stops, on the hub,so that max static is 2650.
The second graph isn't that unusual. On my setup which has an MT governor and Hartzell prop, the rpm will change slightly if I increase or decrease Manifold pressure. More importantly if say you set 22 inches and 2400 rpm then increase or decrease the speed does the prop maintain approx 2400?
I think sometimes we get too hung up on a few rpm difference. Modern instruments are far more accurate than the old gauges where a needle was approx 100 rpm now we get excited about 10-20 rpm difference.

The third graph I'm not sure about. How rapidly are you closing the throttle? It looks like the governor is trying to compensate but over shooting.

I hope this makes sense

Peter
 
Gov line to prop?

It would take very little time to remove that line and verify no obstructions there or in the prop inlet.

From the above I would think one could rule out the governor itself since you've had same results with two different ones.

Might also be good to verify crank plugs are proper. More work tho...

Good luck,

Jerry
 
It would take very little time to remove that line and verify no obstructions there or in the prop inlet.

From the above I would think one could rule out the governor itself since you've had same results with two different ones.

Might also be good to verify crank plugs are proper. More work tho...

Good luck,

Jerry

I was going to suggest this too. A kink in the line? any kind of obstruction? Too small a diameter? Do you have the approved Lycoming stainless steel line?
The other item to check seriously is what Scott suggested -- look at the arrangement of plugs in the nose of the crankshaft. If you are confused about what plugs should be in or out, get an A&P to help you.
 
Prop

Not only check the oil line but the fittings at both ends for restrictions. I doubt if the crank plugs are the cause unless the rear plug is leaking.
Excessive clearance on the front main bearing could cause this issue. I have seen this on a newly overhauled engine.
All other alternatives should be eliminated first as a front main bearing problem is a complete engine teardown.
 
Prop Surging

This engine has the rear crank plug installed and for now has the flexible oil line installed (also approved)

Don Broussard

RV 9 Rebuild in Progress
 
Prop Surging

When I was a young mechanic the older mechanics would claim that a flex line could cause prop surging, due to elasticity I presume. In the years since I have seen numerous aircraft with the flex line and have converted and flown some myself. Don't know if it was a urban legend. I have not come across anyone that has experienced prop surging caused by a flex hose, but believe it might be possible. I have the hard line that we will try a some point in the trouble shooting process.

Don B
 
Gasket?

Not based on experience or anything, but did you double check the gasket so the holes and bleeds are in the right place.

It seems like either high flow demand (chamber leak) or restricted flow to the prop, slowing the response. The graphs have the time so broad it is hard to see the synchronization, or offset, of a single event.
 
All Gasket Holes Aligned

I checked alignment every time I have removed and installed
a governor on the engine.
The one thing I have not done is remove and check the flex hose
from gov to prop.
I plan on doing that in the morning.
 
Not based on experience or anything, but did you double check the gasket so the holes and bleeds are in the right place.

It seems like either high flow demand (chamber leak) or restricted flow to the prop, slowing the response. The graphs have the time so broad it is hard to see the synchronization, or offset, of a single event.


A couple more data points for you smart fellas that are helping troubleshoot.

Gasket only goes on one way, the screen goes into the cavity in the gov base and the holes in gasket are symmetrical so even if you could put it on backwards the oil passages would not be blocked.

This prop is not sluggish or hyper, it exhibits a very normal response time when moving the prop control in flight. I think that means oil supply line & fittings will be found to be unrestricted. Both governors have exhibited varying sluggish response time.


Don Broussard (Bert's Assistant)

RV 9 Rebuild in progress
 
Try this?

Any friends nearby flying the same setup, RV with 320/360/CSP? If so ask them to ride along and see what they say. Is it possible it's all normal?

Just thinkin'

Jerry
 
Thanks Jerry

Yep been done. I did transition training in a 6A (360/CS) owned by
CFII friend. He then flew with me in 9A under the APP and was very
bothered by prop behavior. Nothing like the 6A prop. In 6.5 hrs in
6A never felt or heard anything like mine.

Next step is gather tools etc and do the pressure check on the
prop oil circuit per Lycoming.
My stomach already in knots.
 
Bert,
I know how frustrating it is to not be able to nail down a problem. Keep in mind that it is MECHANICAL and there will be a solution somewhere. don't (if this is possible) let it keep you up at night and get your stomach acids churning. The positive side of this is that you will be an inspiration to all who read VAF when you post how you discovered and eventually cured your problem, (and you will). I read these posts daily because we are about to launch our 14 in the next month or so and hopefully we won't experience any of the myriad of problems I read about. Again I say, it is mechanical and not a health issue so don't make a health issue out of the problem. Feel free to ask any of us who have had an unexpected diagnosis and the fixes involved to the human aspect of flying. Keep the posts coming.
 
It certainly does sound like inadequate flow, for some strange reason. It could be something as simple as vibration of the line at certain RPMs. I will be curious to see what it turns out to be. I am sure you will bottom it out eventually.
 
Prop

You seem to be running out of possibilities. Even though you say you checked the hose I would replace it with a hose made by a reputable hose shop. It is possible you have a flaw in the hose that you missed on a visual inspection.
 
You seem to be running out of possibilities. Even though you say you checked the hose I would replace it with a hose made by a reputable hose shop. It is possible you have a flaw in the hose that you missed on a visual inspection.

What is the volumetric flow through these lines? If it is high enough, there is a possible failure mode in which the inner liner of the hose delaminates. Then when liquid flows past it a local low pressure area can suck the liner inward and actually obstruct flow. When flow is removed, the "bubble" goes back to normal and is very difficult to visually detect. I have seen this happen with hoses and also with rubber lined piping systems.

If there isn't much flow in this line, this failure mode would probably not apply because the local pressure would not drop low enough.
 
Not a High Flow Rate

The flex hose I have, that runs from governor adapter to the
prop, is a SS rated at 1500 psi. It too is new with 14 hrs of operation.
The leak down test by Lycoming requires the governor to be removed.
Then a plate is bolted on in place of governor. It has been tapped so
the same gauges you check the compression with can be hooked to
the plate. This allows your to pressure the prop circuit. The procedure
call for 40 psi on first gauge from compressor. The specs showing amount
of leak down on second gauge are 6 to 35 psi. Anything inside that range
is considered good.
Based on these numbers I would say the flex is more pressure than flow.

Plate for governor is being made and I hope to be able to do the
procedure Friday morning.
 
The flex hose I have, that runs from governor adapter to the
prop, is a SS rated at 1500 psi. It too is new with 14 hrs of operation.
The leak down test by Lycoming requires the governor to be removed.
Then a plate is bolted on in place of governor. It has been tapped so
the same gauges you check the compression with can be hooked to
the plate. This allows your to pressure the prop circuit. The procedure
call for 40 psi on first gauge from compressor. The specs showing amount
of leak down on second gauge are 6 to 35 psi. Anything inside that range
is considered good.
Based on these numbers I would say the flex is more pressure than flow.

Plate for governor is being made and I hope to be able to do the
procedure Friday morning.

Good to hear, Bert. I made a crude plate to cycle my prop in place. It should be easy to perform the test.
 
The flex hose I have, that runs from governor adapter to the
prop, is a SS rated at 1500 psi. It too is new with 14 hrs of operation...

I think that the issue that 1001001 and others are trying to raise is that there are a variety of failure modes in flexible hoses besides bursting. I've also seen flaps of rubber get cut off of the ID while fitting the ends that later cause intermittent problems.

Thanks, Bob K.
 
I think that the issue that 1001001 and others are trying to raise is that there are a variety of failure modes in flexible hoses besides bursting. I've also seen flaps of rubber get cut off of the ID while fitting the ends that later cause intermittent problems.

Thanks, Bob K.

That's the idea. An additional failure mode related to the one I mentioned above is that if the inner liner of the hose becomes delaminated, it can kink and obstruct flow even when the outer part of the hose is smoothly curved and appears undamaged.
 
Hose

That's the idea. An additional failure mode related to the one I mentioned above is that if the inner liner of the hose becomes delaminated, it can kink and obstruct flow even when the outer part of the hose is smoothly curved and appears undamaged.

That is exactly what I was suggesting. At this point I would be trying a different hose. Try to find a hose that is rated 3000# even though the pressure in the governor line is way below that.
 
Path Forward

If the engine passes the leak down test Friday, then based on Bob, Dave and Jim's post on the the flex hose,
the flex line will be removed and a solid SS line installed. Don B aka Cajunwings has one for his O-320/CS
he's not ready to use yet on his 9 rebuilt.
I will then go and fly the same profile, as best as I can, that I used to made the charts.
Then if that does not solve the problem, Don has offered his prop, same as
mine, to try and finally nail down my prop as the problem.

My spinner will not fit Don's prop. If I try Don's prop, does anyone see any problems
flying without the spinner?

First goal, pass leak down test Friday.
 
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Prop problem

I have a friend that had CS prop problem that was traced to the large thrust/crankshaft bearing. It was not perfectly installed or shifted and when the fixed pitch prop was replaced with a CS it caused rpm problems. I guess that is what the leak down test is for.
 
Thrust Washers

My 0 320 with Lycoming case does not have thrust washers. Some of the clones do.
Front main bearing clearance, rear plug integrity and thrust clearance can all affect leakage.
 
Test Update

Shot of Test Plate I had friend make. It is bolted on in place of the
governor.


I made a bunch of mistakes on the test. First I didn't have any help.
I didn't tighten the bolts that hold the plate enough. So when I was
warming the engine I could not see the plate. Oil everywhere. I did put
a flare fitting at the gauge port and ran tubing up above and installed
gauge where I could see it from the cockpit. The 100 psi gauge rapped out
against the stop indicating way over 100 psi. Bought from Grainger and it is
a 100 psi.
Warmed oil to 110 degrees and all cylinders just over 300. But after
shut down and cleaning all the mess up found second mess up. I should
have removed the plug for the prop circuit and installed the female side
of quick connector for the test gauges. Soooo, but the time I FINALLY
connected the gauges and added air, the engine had cooled a good bit.
When I first applied the 40 psi, the gauge on the prop circuit when up to
almost 40 psi while it was pushing oil out of the transfer line and other
areas. It then settled down around 30 psi which indicates a good test.
Lycoming said it should be between 6 and 35 psi.
Still not sure why pressure on gauge was so high if true.
BUT...as I just left the air running, over time of about 20 minutes
the pressure on the prop circuit declined to below 6 psi. If I moved the
prop around, it would go back above 6 psi then go back down. Lycoming
does not give a time factor on the test. I assume the air cooling down
the bearings etc reduced the back pressure...right?

So today, if I can beat the coming storms, going to go back and
1. Check plate for tight once more.
2. Leave quick connect installed with hose removed. Can't think of any
reason not to do this since there should be no pressure on that circuit.
3. Install another cheap gauge but 0-200 psi this time, just to see.
4. Warm to 110 degrees oil temp.

Then immediately on shut down hook up gauges and apply 40 psi to
prop circuit. AND see what new gauge shows for oil pressure.

We'll see.
 
2nd Test Update

This is shot of remote pressure gauge reading at the governor
test plate.


No leaks on plate, warmed engine to oil temp of 112 degrees.
Surprise was the pressure on the remote gauge. The pressure after
engine start was 190 psi. Normal EFIS pressure showed 78 psi.
After engine was warm EFIS showing 64 psi and remote gauge showing 110 psi.
Was able to put test on within 10 minutes of shutdown and pressure was in
the 20 psi area. Then as cool air purged system the pressure went down
to around 6 psi. So next step is to discuss pressure reading and test with
Lycoming on Monday.
In the mean time, I am going to remove prop and check the crank from
the prop end. Just to make sure the plug, tube and all is secure.

Update after discussion with Lycoming.
 
I've been following your agony online Bert, and I can't help but think they told us about this problem at Lycoming school....but I'm not at home to consult my notes, and they crammed so much into our heads in four days of service school, I just can't recall the details. I do think, however, that if this is that case, it was not good.... (Split case to fix).

Perhaps Condor will remember.
 
C/S v's F/P

Confirm your engine type - the D2G is fixed pitch only. Apparently the crank does not have the required oil feed

from Vans site:
Experimental O-320 160HP( Fixed Pitch Only ) Part Number = EA XO-320-D2G RT
 
Confirm your engine type - the D2G is fixed pitch only. Apparently the crank does not have the required oil feed

from Vans site:
Experimental O-320 160HP( Fixed Pitch Only ) Part Number = EA XO-320-D2G RT
 
My guess is after 20 minutes the oil between the front main journal and the front main bearing blew out from the air pressure. That would account for the drop over time to below 6 PSI. This would not occur on the engine while it is operating because pressurized oil is continually replaced to the bearing.
 
FYI -http://www.vansairforce.com/community/showpost.php?p=316281&postcount=5

Even though the supply has pressure, does it have flow? See link.
 
Prop Removed

I removed the prop yesterday. Wanted to see config of my crank
and retrieve the numbers from the crank.
Prop end of my crank does not look like others I have seen on the forum.
There is no step down inside the crank, same bore from lip to the plug.


Then I don't have the tube running across the crank but just a hole in
the side of the crank. I measured and it is in line with the inlet oil
from the governor.


So today discussion with Hartzell and see what they have to say about
my setup.

Any comments, suggestions etc, appreciated.
 
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View Sec 11 page 14 of the RV9 construction manual:

0-320-D2A 160 2700 100 100L 8.5:1 Same as D1A but with fixed pitch prop and 3/8 attach bolts.

0-320-D2G 160 2700 100 100L 8.5:1 Same as D2A but with Slick Mags, 7/16 instead of 3/8 prop bolts
 
Just an observation . .

But without that tube, it might have a hard time (if impossible) purging the air from the cavity. That would provide a large delay in response with it's compressibility and very mismatched to the mechanical dynamics of the system. Much more extreme than a hose. Also, the pressure to activate increases with rpm, changing the governor pressure balance point with the flyweights. I estimate the pressure at about 3-3.5 psi at 2700, so that is probably not as big a factor as purging.


I will be interesting to hear what the factory has to say. Speculation withheld.
 
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Engine Build

The engine started life as a D2G and was removed from a 172
with 1100 hrs for a bigger engine.
The engine was built by an noted engine builder in Atlanta.
The build log states that the engine was converted to CS.
It states:
The Crankshaft is a O320D2J overhauled by Rick Romans.

So not the stock crank.
 
im no expert on lycoming numbers, but i was under the impression that only -1 and -3 cranks were constant speed cranks, and that -2 cranks were fixed pitch only.

bob burns
N82RB
 
could the engine have been one that had the drain line in the left hand side of the case (internal) which has to be plugged to use that case for constant speed operation. see attached paper, and that drain was not plugged during the conversion?

http://eci.aero/pdf/04-4.pdf

bob burns
 
Tough Right Decision

Yesterday, after much discussion between Don (Cajunwings) and
Aircraft Specialties, the decision was made to pull the engine.
This really hurts at this stage of getting to finally fly and learn.
I will start pulling the engine today for transport across the swamp
to Don's shop. Could build a shuttle there if needed.
The crank goes to Aircraft Specialties to see what kind of deal we
can make with them for the correct CS crank. We will be especially
checking to see if the drain hole on the left case half is plugged.

As hard as it is to do, pulling the engine is the right thing to do. I committed
to building the plane right and not skimping or short cutting.

Updates as when I know more.
 
Yesterday, after much discussion between Don (Cajunwings) and
Aircraft Specialties, the decision was made to pull the engine.
This really hurts at this stage of getting to finally fly and learn.
I will start pulling the engine today for transport across the swamp
to Don's shop. Could build a shuttle there if needed.
The crank goes to Aircraft Specialties to see what kind of deal we
can make with them for the correct CS crank. We will be especially
checking to see if the drain hole on the left case half is plugged.

As hard as it is to do, pulling the engine is the right thing to do. I committed
to building the plane right and not skimping or short cutting.

Updates as when I know more.

Good idea Bert.

The last engine I saw this happening with was missing the plug which was also discovered after using the pressure test procedure I referred you too.
In that case, the prop wouldn't ever change pitch at all so I don't think that is your problem (but it will be good to be able to confirm). I think it is likely because of an incorrect crankshaft.
 
Bert, I just wanted say thanks for taking the time to share what's going on and your thought process as you go through this. This is all really useful.
 
Ya same here. Sorry to learn at your expense but it will save some guys from buying the wrong crank in the future. You had no choice but to pull the engine. Thank you for posting and I hope you get back in the air soon.
 
Update and Findings Exactly Nothing

The engine was pulled and Monday we tore it down.
First surprise and I understand rare was the two through bolts
that go through the case. My two were threaded into block and
did not rely on press fit in the middle. FYI


Then it was on to the accessory case to see if there was a blockage
causing the high pressure (190 on startup) at the governor supply.
Nothing found. Vernatherm was way off the seat, so no oil being forced
to the cooler. The channel that runs from oil filter return to the engine
pressure regulator has the EIS pressure tap on it. Yet at startup the pressure
on the EIS was 80-90psi....normal. So thinking restriction between EIS
pressure and return from filter...clean.
So called Airwolf. I have the Airwolf remote oil filter system. We were told
the normal back pressure across filter is very small and if I had a
Champion 108/109 filter it has a bypass. I use Tempest (which has a
12-14psi bypass) and was told Champion was the only filter they tested
and recommend. I have not figured a way yet to test filter back pressure.
So at this point no smoking gun.
Here is shot of my accessory case labeled with flows


Crank is at Aircraft Specialist being evaluated so we can figure what the
net cost to me will be for a crank with the cross tube.
One thing I noticed, it appears the area inside the crank from rear plug
to the lip where prop attaches appears to be smaller on the cross tube
crank than the one I had with just the single hole in the wall. I was
wondering if the smaller volume of oil will respond to governor inputs
faster than the larger area?
That's it for now.
As usual, all comments, recommendations appreciated.
 
Tempest

I've always used the Tempest 48109 filters on the Airwolf remote filter setup with no problems.

Vic
 
The engine was pulled and Monday we tore it down.
First surprise and I understand rare was the two through bolts
that go through the case. My two were threaded into block and
did not rely on press fit in the middle. FYI


Then it was on to the accessory case to see if there was a blockage
causing the high pressure (190 on startup) at the governor supply.
Nothing found. Vernatherm was way off the seat, so no oil being forced
to the cooler. The channel that runs from oil filter return to the engine
pressure regulator has the EIS pressure tap on it. Yet at startup the pressure
on the EIS was 80-90psi....normal. So thinking restriction between EIS
pressure and return from filter...clean.
So called Airwolf. I have the Airwolf remote oil filter system. We were told
the normal back pressure across filter is very small and if I had a
Champion 108/109 filter it has a bypass. I use Tempest (which has a
12-14psi bypass) and was told Champion was the only filter they tested
and recommend. I have not figured a way yet to test filter back pressure.
So at this point no smoking gun.
Here is shot of my accessory case labeled with flows


Crank is at Aircraft Specialist being evaluated so we can figure what the
net cost to me will be for a crank with the cross tube.
One thing I noticed, it appears the area inside the crank from rear plug
to the lip where prop attaches appears to be smaller on the cross tube
crank than the one I had with just the single hole in the wall. I was
wondering if the smaller volume of oil will respond to governor inputs
faster than the larger area?
That's it for now.
As usual, all comments, recommendations appreciated.

The crank case should also be looked at.
I think some cases have a passage that needs to be blocked with the installation of a threaded plug when a constant speed is used (this is a different plug than the one in the crank shaft) but this would only apply to old engines. If your is relatively new production, disregard.
 
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No Hole

Scott, that hole you mention is on the left side of the case midway
on the 4" front main bearing. The prop governor pressurized area.
My case had no hole, not even on that had been plugged
 
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