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Propeller Governor
 | 2011.04.21:
Overview: The prop governor is a mechanical / hydraulic device that
regulates oil pressure to the propeller (which controls the blade
pitch) to attain the RPM selected by the pilot. On the
IO-360-B1B engine, the prop governor mounts to a drive pad on the rear
accessory case (other engine variants mount the governor forward).
The standard prop governor currently sold by Van's is a relatively new
design from MT.
It is reputed among those who've installed it to have problems with
hunting and surging, and has undergone at least half a dozen revisions
over the past few years with limited success in alleviating these
problems. As many other builders have done the past couple of
years, I've decided to use a different governor instead, the PCU5000X
from Aero Technologies. The PCU5000X is the experimental
identical twin of the certified PCU5000, and these are actually a Jihostorj
governor that is final-assembled, certified, and re-branded in the
U.S. These are widely reputed to be the best performing, most
reliable prop governors on the market. I purchased mine from American
Propeller in Redding, CA. My specific variant is p/n
P-520-036/A-866 (this is actually Jihostroj nomenclature), which
specifies oil to increase pitch, 0.866:1 drive ratio, control lever
clockwise for high RPM looking at the head (not the base) of the
governor.
Control cable bracket: Van's standard bracket is
p/n VA-153-PC, and is designed to mount to 3 of the 6 screws on the
head of the MT governor. A similar arrangement will work well
with the PCU5000X governor, but the head dimensions are just ever so
slightly different that the VA-153-PC bracket won't quite work as
is. The inner diameter has to be opened up a bit more, and the 6
head screws are spaced a bit wider apart. Some folks have
elongated the mounting holes to make it fit, but I wasn't happy with
elongating them as much as would be needed. As a first attempt,
I had my neighbor buzz weld the mounting holes shut so that I can
re-drill them in the correct places. But in grinding the weld
flat, too much material was lost around one of the holes. Oh
well. Second attempt, I fabricated a brand new bracket from
stock sheet (0.063" 4130 chromoly, same as Van's bracket).
Came out great.
Mounted the governor to the engine. Then mounted the bracket to
the governor head, adjusted the clocking of the control lever, and
finally tightened down and safetied the 6 head screws.
Below: The prop gov pad on the rear accessory case of the engine, with
the gasket that came with the engine.
Below: The pad with gasket removed.
Below: The gasket that came with the prop gov. Note that it has
extended cutouts and a filter screen.
Below: The base of the PCU5000X governor, with protective plastic cap
over the drive spline.
Below: the PCU5000X governor mounted to the engine.
Below: The bracket I made mounted to the governor, control lever
clocking adjusted, and the 6 head screws are tightened and safety
wired.
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