Cessna Not Turning Max RPM

[superchamp]

My Cessna 182 with the Pponk o-520 is turning 2550 RPM, redline is 2700. I verified tach is correct through entire rpm range with a gun. The prop control is going all the way forward to the limiter on the governor, we turned the governor as far up as it could go, and that only got me another 50 rpm at best. EI Int'l engine monitor shows everything good on all cylinders, no oil burn, and purs like a swiss watch. Prop is the 80 inch 401 Mac, and a Continental governor. I've put about 50 hours on the plane (all on floats) since purchasing this winter, and I am guessing that is all the rpm it ever turned. I just haven't paid any attention since it has been so cold and windy all summer that performance hasn't suffered, now that we have had a few hot humid days I started paying close attention and noticed the RPM isn't going to redline at initial throttle up. Any ideas?

 

[willyb]

Have you checked for full throttle at the carb?Clogged filters,Mag timing?Mixture control correct?Prop pitch stops correct?

Bill

 

[superchamp]

Verified full throttle and mixture control, have not gone as far as mag timing or filters, pitch stops are something we have as a suspect. Also waiting for word from Maxwell and Pponk before digging more. Thanks.

 

[Alaska_Rallyer]

If its not mag timing i would swap the prop gov. Prop govs are expensive so see if someone has one they would loan ya or just send yours out for bench check. Make sure it is the correct PN gov.
Check your carb heat as well.
Will it turn red line once flying???

 

[superchamp]

It will not redline once flying. Hits 2550 right when I go to full throttle and the plane is climbing on to step, then as it is accelerating on step runs about 2500-2525. in the air 2525 seems about it.

 

[mvivion]

I'd have the prop shop verify the pitch stops are properly set on the propeller blades.

MTV

 

[lowlevelops]

If you can't get redline RPM in cruise or descent then I would bet the governor is holding it at that RPM. All of the above suggestions seem viable but if the RPM remains constant in all aspects of the flight then it would seem to be a governor issue.

 

[mike mcs repair]

If you can't get redline RPM in cruise or descent then I would bet the governor is holding it at that RPM. All of the above suggestions seem viable but if the RPM remains constant in all aspects of the flight then it would seem to be a governor issue.

or you burnt up the oil transfer collar on the crank, and prop gov is unable to present enough pressure to prop.....(if that gov/prop combination work that way-- no idea on yours)

 

[xcalibur]

Check for exhaust blockage...........

 

[Alaska_Rallyer]

Hmmm if you have low rpm on the ground and it picks up once you have air speed then i suspect ignition, exhaust, carb, induction all the usual stuff. That does not seam to be the case...
You can measure the blade angle with a propeller protractor or digital smart level. Verify this measurement with a prop shop.
My bet is on the governor. I have had more then a few... ok only two bad one ones but all recently.


mikemcs

or you burnt up the oil transfer collar on the crank, and prop gov is unable to present enough pressure to prop.....(if that gov/prop combination work that way-- no idea on yours)

The propeller with no oil pressure, engine not running, is on the low pitch blade stops. It takes very high oil pressure from the gov to drive the propeller to low pitch or low RPM. sooooo... if the passage in the crank was clogged the propeller would fail to high rpm. I know you know this.
I KNOW if you install the oil transfer plug in the wrong position you can block this passage preventing any oil from getting to the propeller throught the hollow crank. If you happen to do this the prop will still make static rpm, but when you pull that blue knob nothing happens.

 

[mike mcs repair]

mikemcs

or you burnt up the oil transfer collar on the crank, and prop gov is unable to present enough pressure to prop.....(if that gov/prop combination work that way-- no idea on yours)

The propeller with no oil pressure, engine not running, is on the low pitch blade stops. It takes very high oil pressure from the gov to drive the propeller to low pitch or low RPM. sooooo... if the passage in the crank was clogged the propeller would fail to high rpm. I know you know this.

their are some types/brands that work backwards to most..... we learned on a prop change for ferry flight one time.... had heck of a time making engine run and not cough and black smoke.... then we tried pushing prop control in and it flattened right out..... ran fine then....

but that was least of heartburn.... left rear spar/angle was only held on by 3 #8 Pk screws at root.... told him no flaps no mater what!(C-180)

 

[skywagon8a]

Is it possible that the arm on the governor is indexed incorrectly so that it is not being rotated to the max rpm position? The governor does seem to be regulating the rpm.

 

[superchamp]

Thanks for all the trouble shooting guys. I'm gonna print the list out and hopefully fly down to my mechanics tomorrow if the weather breaks. I will post when I get to the bottom of it.

 

[Steve's Aircraft (Steve)]

Sounds like the governor control arm was installed out of index. I believe you mentioned changing the "stop" screw and gained about 25 RPM. Usually, changing the arm index one notch will change rpm by 100 and one full turn on the screw will change it 25 rpm. From all indications, the governor is doing it's job, just not set correctly.

Steve

 

[Crash]

My P Ponked C180 did the same thing. Found out it was a dropped baffle in the exhaust muffler. This was only after it had burnt a hole through the muffler, the muffler heat shroud and then the air intake scoop.

Crash

P.S. Going to the bigger diameter C185 collectors and muffler gained 10 mph, 30 rpm and very real gains out of the hole! Old O-470 exhaust systems on an O-520 just don't cut it!

 

[1954C180]

What is the purpose of those baffles inside the O-470/C-180 mufflers? They're always failing, leading to possible muffler blockage. Barring any compelling technical reason why they should be there, they seem like a detriment to safety....???

 

[aalexander]

The governor does seem to be regulating the rpm.

That's what I'm thinking. If it goes to 2550 when you shove the throttle in and then stabilizes to 2525 on the takeoff run and doesn't get above 2525 once airborne, the system is regulating the RPM to 2525. It's not a low pitch stop, otherwise, once airborne with some airspeed the prop would be off the low pitch stops and would turn up to 2700 rpm.


Ditto with power problems; It would affect the static/low speed runup RPM, but past a certain airspeed, a properly functioning prop governor will turn max RPM regardless of power. If you're not making takeoff RPM at cruise airspeed, it's likely not because of a small reduction in the engine power output.

 

[RobL]

One assumes that the prop governor is reaching the stops:

This cable was found to have come adrift at the swaging near the end (unrelated to the cylinder removal).