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Converting Constant Speed to Fixed Pitch, how?

RudiGreyling

RudiGreyling

Well Known Member
Hi Guys,

I am looking for references, literature, pictures and or website of people that have succesfully converted a Constant Speed engine to Fixed Pitch application.

I have purchased a brand new XP-360 configured for Constant Speed, i.e. hollow crank, but will intitially run it it for 1/2 its live as a Fixed Pitch.

I believe it requires the removal of one crank plug and pluging it at another location. I'd like to see/read how exactly it is done...

Thank you in advance.
Kind Regards
Rudi
 
Lycoming Service Instruction #1435, Part I.
To go from C/S to F/P you basically must either remove or punch a hole in the rear plug. Then insert a new front plug. You also should remove the external oil line and plug those holes.
 
I hope this isn't a stupid question but, when reverting back to the c/s configuration, how do you replace that back plug that now has a hole in it?
 
joeboisselle said:
I hope this isn't a stupid question but, when reverting back to the c/s configuration, how do you replace that back plug that now has a hole in it?
Click to expand...
It's not that difficult. The rear plug is smaller than the front one and the tube is off-center. You can get the rear plug out and replace it with a new one. Or if the rear plug has a removable "pipe" plug, you simply screw in a new one.
 
Gil,
You ARE correct. Teflon tape is NOT recommended! At least by no one I know. I certainly wouldn't use it. There are too many acceptably sealers out there that don't have the potential for contamination.
 
Another Option:

If your engine already has a governor drive pad installed and the external oil line from the side of the pad to the front of the engine is in place, all you have to do is install a plug in the front of the crank shaft. Any oil that collects in the hollow front part of the crank can drain back thru the line to the pad from where it drains in to the sump. The drive pad must have an appropriate cover on the aft side to allow for this to work properly. My Lyc came with it in place. This way no pressure build up will occur in the nose section and removal of the rear plug is not necessary. When you get ready to install the c.s. prop, you remove the front plug. I ran my O-360 A1A from Van's like that for a couple of hundreds of hours with a fixed pitch before I installed the constant speed.

Martin Sutter
building and flying RV's since 1988
 
Be Careful! Not all prop gov drive pad covers will provide this function. Some are capable and some aren?t, so be sure to check The one that you use, must have a groove machined to connect the hole in the mount pad that would supply gov oil pressure to the prop tube, to the center of the drive pad. Without this groove you will not vent the oil pressure that can build up in the nose bore of the crankshaft and will likely blow the front plug from the crankshaft at some point in time.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
 
I had to modify my factory new O-360-A1A to allow the use of a fixed pitch. Mine came ready to run constant speed (after removing the front plug). I followed the Lycoming service instruction (can't recall the number) which requires piercing or removing the inner plug and then re-installing the front plug. I just punched a hole in the rear plug with a long punch. The service instruction also says to remove the governor oil line, plug the hole where it comes out of the front of the engine and remove the governor drive pad and cover with a plate. Since I thought I might want to later go back to a constant speed prop I wondered if it was OK to just leave the governor oil line in place. That way I'd have my baffles and other plumbing already set up to make changing easier. I called Lycoming and asked if this would cause any problems. They told me that other than having a couple of fittings that could conceivably leak and having a little excess weight, this wouldn't hurt anything.

I didn't learn until after the fact that, as noted by Mahlon above, a better approach would have been to get the proper type of governor drive cover plate (with some kind of groove that allows draining excess pressure from the prop chamber). This way I wouldn't be faced with the challenge of replacing the inner plug.

But after flying a couple hundred hours with my 3-blade Catto, I doubt if I'll ever want to convert back to constant speed configuration.

FWIW.
 
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