Rear engine power loss during flight

[Learjetter]

Originally Posted by Jhogan0101

Tim, i also fly a 337B! SN 661!…..
It might also be a good idea to put gauges on your fuel system.
You want to measure metered and unmetered fuel.
You will need this continental adaptor. Continental Tee MS 51523B4
Attached is a chart showing what the numbers should be.
Third row down
https://ibb.co/VL1kXN5

Concur. My avionics shop built a very precise test rig with inline AN pressure transducers to digitally measure the metered and unmetered fuel flows, The rig is housed in a small Pelican case and you can read the displays in the cockpit, making it a one-man job. I do this every annual on my NA G model. Have also done the local twin baron. If you are near central OK, we’d be happy to help you out with yours.

Essentially, you hook up the rig and run the motor at a few select power settings and record pressures. Shut down, adjust as necessary, and run it again. The Continental M-0 manual explains all the steps pretty well. If everything is working normally, a few runs gets the fuel metering and idle speed dead on perfect.

LJ

[Tim Wang]

Today I did a ground run test on the rear engine. The battery charge level was good and there was no problem on the start up. Run up checks as usual were completed without issues. I waited for the engine and the oil temperature to get warmer running the engine around 1800 rpm's. As I moved the prop lever to cycle the prop a drop in rpm's appeared however returning the lever to "fine" pitch didn't change the rpm's as expected and it stayed at the lower rpm reading. I moved the prop lever again to cycle the prop and the rpm's would drop even more once the prop lever moved further towards the "coarse" position and no return to the high rpm setting. Moving the prop lever only caused a drop in rpm's and no increase in rpm's. GOVERNOR fault.
In discussing the matter with my AME, a governor fault fits with my situation since the oil would be thicker at the start of my flight making the seals in the governer work as normal, but as the flight progressed the hotter oil got thinner and the seals inside the governer failed to move the oil around. Since the front prop is pushing air towards the rear prop this would cause the prop to twist to a coarser pitch. The subsequent drop in rpm's would then cause me to increase power to the front engine which leads to forcing more air towards the rear prop, twisting the blades more causing more rpm drop and the cycle continues until the engine quits or shut down. This wouldn't have happened on a side by side engine configuration without a front engine pushing air causing the rear prop blades to twist when a governor fails. Since the run up checks found no issue with the governor there wouldn't be a reason to suspect a problem with this part.

Cheers.

[Jhogan0101]

You could always swap front/rear governors, same part number.
Heres the gaskets youd need TEMPEST® AA9144 FAA-PMA Prop Governor Gasket

[Tim Wang]

Thanks for the information about the gaskets I may need it. Would anyone have the part# for the actual rear prop governor? One repair shop in Canada has provided a quote to overhaul my governor of $2000.00. Checking around for perhaps a better price.

[Jhogan0101]

Woodward Prop Governor 210443D

[Tim Wang]

Hi jhogan, thanks so much for the assistance. BTW I own serial#650.

[mshac]

Here's a used one on Ebay for cheap: https://www.ebay.ca/itm/284792413069