Rallylancer122
Well Known Member
I'm having an issue with a Mccauley prop holding the proper RPM. To recap the issue:
1. First takeoff of the day, the governor works fine. As speed increases the prop comes off the pitch stops (2660-2680 ish?) and goes to 2700. It holds it there pretty nicely.
2. Subsequent takeoffs (basically once the oil comes up to about 140-150 or more) once the prop comes off the pitch stops the governor will pull it down to 2600 or so. Sometimes it will surge up between 2600-2650ish.
3. On climbout and cruise and I’ll see approximately 30 rpm fluctuations, random but constant from wherever I set the rpm.
4. Once in cruise it will settle down after about 15 minutes and I’ll see a less than 10 rpm fluctuation. (At this point you can’t hear it anymore, but you can see it on a digital tach. For all I know they always did this and we just didn’t know it with old analog tachs.)
The governor was overhauled in 2018. In 2020 I bought the airplane and noticed the issue. I sent the governor in to the OH shop, they bench checked it, said it was fine and I reinstalled it. The issue remained, and I largely lived with it until now. Either it’s gotten worse lately or I’m just sick of dealing with it. So I sent it to another shop who felt it was the speeder spring. They checked it, couldn't find anything wrong, changed the speeder spring anyway, charged me a ton of money, and...no change once reinstalled on the plane.
The first shop felt it was the prop. It's got less than 1000 hours OH, but calendar wise it's been 15 years or so. However its tight, doesn't leak a drop, and is otherwise in good shape. I pulled the dome, cleaned out the crud, and put in a new oring...no change. The governor has about 300hrs on it since OH.
Any thoughts here? I really don't want to just shotgun this and send the prop in unless I can determine for sure that's where the problem lies.
1. First takeoff of the day, the governor works fine. As speed increases the prop comes off the pitch stops (2660-2680 ish?) and goes to 2700. It holds it there pretty nicely.
2. Subsequent takeoffs (basically once the oil comes up to about 140-150 or more) once the prop comes off the pitch stops the governor will pull it down to 2600 or so. Sometimes it will surge up between 2600-2650ish.
3. On climbout and cruise and I’ll see approximately 30 rpm fluctuations, random but constant from wherever I set the rpm.
4. Once in cruise it will settle down after about 15 minutes and I’ll see a less than 10 rpm fluctuation. (At this point you can’t hear it anymore, but you can see it on a digital tach. For all I know they always did this and we just didn’t know it with old analog tachs.)
The governor was overhauled in 2018. In 2020 I bought the airplane and noticed the issue. I sent the governor in to the OH shop, they bench checked it, said it was fine and I reinstalled it. The issue remained, and I largely lived with it until now. Either it’s gotten worse lately or I’m just sick of dealing with it. So I sent it to another shop who felt it was the speeder spring. They checked it, couldn't find anything wrong, changed the speeder spring anyway, charged me a ton of money, and...no change once reinstalled on the plane.
The first shop felt it was the prop. It's got less than 1000 hours OH, but calendar wise it's been 15 years or so. However its tight, doesn't leak a drop, and is otherwise in good shape. I pulled the dome, cleaned out the crud, and put in a new oring...no change. The governor has about 300hrs on it since OH.
Any thoughts here? I really don't want to just shotgun this and send the prop in unless I can determine for sure that's where the problem lies.