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  #1  
Old 01-05-2011, 06:50 PM
DEWATSON DEWATSON is offline
 
Join Date: May 2007
Location: Quincy, Florida
Posts: 680
Default MT prop governor surging

I now have 12.1 hours on my airplane. At about 10 hours the propeller started surging at takeoff power. I've read gobs of information here, but I wonder if there is an update. The propeller governor is a MT P-860-4. It calms down once airborne and set to 2450 RPMs and acts fine until the next takeoff. There's always a problem to solve, I guess.

David Watson
49FD
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  #2  
Old 01-05-2011, 06:59 PM
AltonD's Avatar
AltonD AltonD is offline
 
Join Date: Sep 2005
Location: Dothan, Alabama
Posts: 1,496
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Hey Dave, you rekon it is the oil temp?

On another subject, how are your oil temps now?
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Alton DeWeese
N526RV RV7A Tip Up, IO360 180 W/Hartzel BA prop.
Flying ~1000+ hours since Aug 28, 2010
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?The secret of getting ahead is getting started. The secret of getting started is breaking your complex overwhelming tasks into small manageable tasks, and then starting on the first one.?

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  #3  
Old 01-05-2011, 07:05 PM
bcondrey bcondrey is offline
 
Join Date: Jan 2005
Location: Bellevue, NE
Posts: 555
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Check the revision level - some of those, not all, below revision F has the surging issue. This is a known issue that MT acknowledges and they will take care of you if that's the case.

Bob
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  #4  
Old 01-05-2011, 07:10 PM
DEWATSON DEWATSON is offline
 
Join Date: May 2007
Location: Quincy, Florida
Posts: 680
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Yes, I think it might be. It doesn't do it on the first flight of the day.....only after the engine is heat soaked. What is the cure? Temperature is now running about 207. Switching the oil cooler lines is all that I've done so far. You were right!!!!!

I'll be up to visit sooner or later. I'm looking forward to meeting you.

David
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  #5  
Old 01-06-2011, 02:18 AM
kiwipete kiwipete is offline
 
Join Date: Oct 2007
Location: Birmingham United Kingdom
Posts: 471
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David

As Bob pointed out check the serial number of the unit. If it ends in a letter less than f then you'll need to return the unit to MT to be updated.
Once I sorted mine out it's been fine.
Another thing to check is the fine pitch stops on the prop, as per the hartzell manual. So when you open the throttle quickly the prop won't overspeed before the governor has time to work.

Peter
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  #6  
Old 01-06-2011, 02:18 AM
Andy Hill's Avatar
Andy Hill Andy Hill is offline
 
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David...

Worth ensuring the MT governor is a modifed one. But it is not the whole story... It is a fairly common problem, and usually "caused" by the builder not setting up the static RPM of the Prop (Fine Pitch Stop).

If a Hartzell, you'll know if you've done this by taking off the spinner, and adjusting the Hex screw/bolt on the front of the hub. Many (including us!) forgot / did not realise we had to do this. The Hartzell manual has you do this via a tie down and full power runs... this is quite dramatic IMHO. An alternative approach which I prefer, is on every takeoff during the test phase, establish both the static RPM (maybe initially via an aborted takeoff i.e. full power, note max RPM achieved, idle, coast to a halt) v Headwind, and then governed RPM in the early climb.

Setting the static RPM too low e.g. 2600RPM will only cost you 5%? 10%? thrust/power for the very early takeoff roll - by 20K-30K it will have increased to ~2700RPM i.e. the governor setting.

The surging is caused by the governor's inability to limit the RPM to 2700 as you smartly set takeoff power - you set the static RPM to initially do that like a FP prop, and then as IAS increases, the governor can cope with slowly altering the blades to maintain 2700RPM.

My suggestion would be to set static RPM to 2600-2650, and governor RPM to 2670-2700. The latter - refine the governor RPM and your EFIS "overspeed death is upon you warning lights / bells / whistles" far enough apart you do not routinely trigger them

Andy
RV-8 G-HILZ
RV-8tors
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  #7  
Old 01-06-2011, 06:38 AM
DEWATSON DEWATSON is offline
 
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Location: Quincy, Florida
Posts: 680
Default Prop surge

Andy,

I have a Hartzell blended airfoil propeller that I bought from Vans. The prop governor is a MT and the part # is P-860-4. The serial number is 07G044-D. I've never seen the RPM exceed 2650 static. It will rev up to about 2760 when it surges on takeoff when the oil temperature is up.

What needs to be done? Does the governor need to come off and sent back to MT for inspection. I'll check the fine pitch stops on the propeller tonight and make sure that's not the problem. I checked them when I installed the propeller but I'll check it again.

As Alton said, it only does the surging when the oil is hot.....never on the first takeoff of the day. When the oil teperature is hot though, it will surge back and forth until I do something about it. I have been decreasing the throttle setting and pulling the prop governor back to make it quit.

Thoughts....
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  #8  
Old 01-06-2011, 07:06 AM
Andy Hill's Avatar
Andy Hill Andy Hill is offline
 
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Hi David...

Quote:
I've never seen the RPM exceed 2650 static
Sitting on the runway, pointing into wind, brakes off, smartly select full power and watch for absolute Max RPM before, say, 20K... is that your judge of Max RPM? If so, then it seems right. However, since it is relatively quick/easy, I'd back that off to nearer 2600RPM and see if it helps.

We got our Governor in ~2007, as a B. As per advice here we sent it back, and it came back as an -E, and it did surge a bit on touch and go's, overshoots etc. Reducing the Static RPM cured it. The advice in 2007 was that the -B were the problem, and that a -C or -D would solve it. That advice now seems to be you need a -F ! (Our -E is fine).

Overall - have a play with Static RPM, unless you operate out of a 300' strip, setting it a bit too low won't be a safety issue. If it solves it great, if not, maybe look at modifying/changing the governor, but that will take sometime...

I've test flown a few C/S RVs, and the RPM governing is often a bit suspect, but lowering the static RPM seems to help, even when logic says it should not

What engine have you got? And have you ever setup the static RPM? I find invariably they are supplied too fine for 180HP...

HTH?
Andy
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  #9  
Old 01-06-2011, 07:32 AM
SkywayCaptain's Avatar
SkywayCaptain SkywayCaptain is offline
 
Join Date: Jan 2008
Location: Sheridan, IN
Posts: 94
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Quote:
Originally Posted by DEWATSON View Post
Andy,

I have a Hartzell blended airfoil propeller that I bought from Vans. The prop governor is a MT and the part # is P-860-4. The serial number is 07G044-D. I've never seen the RPM exceed 2650 static. It will rev up to about 2760 when it surges on takeoff when the oil temperature is up.

What needs to be done? Does the governor need to come off and sent back to MT for inspection. I'll check the fine pitch stops on the propeller tonight and make sure that's not the problem. I checked them when I installed the propeller but I'll check it again.

As Alton said, it only does the surging when the oil is hot.....never on the first takeoff of the day. When the oil teperature is hot though, it will surge back and forth until I do something about it. I have been decreasing the throttle setting and pulling the prop governor back to make it quit.

Thoughts....

I have the same prop and governor combo and had similar problems. Adjusting the low pitch stop to a higher angle fixed it. Here is how I adjusted mine.

Run up at full power and note the static rpm (should be 2700 rpm or so depending on your engine specs). Shut down. Take off your spinner and adjust the stop to a coarser angle then run up at full power again. If the RPM is the same then keep increasing the low pitch stop (I think this is turning the stop clockwise, it says in the prop manual) until the static RPM is slightly less than redline (50-100 rpm).

Goodluck
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Drew Cook - K9QV
Sheridan, IN
RV-7 N673AC
Superior IO-360 Horizontal Induction
Hartzell C/S Blended Airfoil
IFR Steam gauges
TruTrak Digiflight IIVS
500 Hours on airframe
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  #10  
Old 01-06-2011, 08:48 AM
DEWATSON DEWATSON is offline
 
Join Date: May 2007
Location: Quincy, Florida
Posts: 680
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Andy and Drew,

I set the propeller stop (checked it) when I was doing the first engine runs. It turns static at about 2650 (tied to a tractor....not moving down the runway). For the first 10 hours, I had no problem with the prop wandering up and down. It will now, and will exceed 2700 and then come back to 2560, etc. It has started doing this in the last two hours. The engine has 192 horsepower according to Americas Aircraft engines. It is an IO 360 paralell valve engine.

I'll reset the stop to 2600 RPM. I have plenty of power and this won't be unsafe at all.....I operate out of a 2000' strip. If this doesn't correct the problem, I guess I need to contact MT and see what they suggest?????

David
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