Building, testing and operating an experimental aircraft

Installing the Prop Governor

19 Dec 2014

When I went to remove the governor pad cover on our new Lycoming engine, I expected the preservative engine oil to come gushing out of the ports as soon as the bolts were loosened. It didn’t. At first, I wasn’t sure exactly what this meant, but later we found out the real reason – our engine had no oil.

Removing the Governor Pad Cover Removing the Governor Pad Cover

While the idea of this was vexing, it did make the task at hand a bit simpler. After removing the cover plate, I did some test fitting of the MT governor that Van’s shipped with the firewall foreward kit and then turned my attention to installing the VA-153 governor cable bracket.

Original Safety Wiring Original Safety Wiring

The first order of business was to get a real close look at the original safety wiring that had been done on the stop plate screws. This was first mission-critical item that I’d had to safety wire, and I wanted to do it right.

Cable Bracket Installed Cable Bracket Installed

Dad and I installed the cable bracket so that it would protrude from the installed governor in a roughly level orientaion. The governor mounting pad on the engine is tilted to the right at about 45°, so this took a bit of experimentation.

Control Arm Re-clocked Control Arm Re-clocked

Once the cable bracket was mounted, we loosened –but did not remove!– all six screws on the stop plate, so that the control arm was free to rotate. In our case, the ideal position for the arm was at about the one o’clock position when viewed from the rear of the engine. Since our prop cable was already installed on the firewall, we had to test fit this a few times to get the cable travel we wanted.

I found that the prop cable couldn’t be set to move the control arm on the governor to both stops – it would either hit one or the other. So, we set the cable travel so that the arm would hit the fine pitch (takeoff) stop, and not quite hit the coarse pitch (low RPM) stop. I reasoned that the low RPM stop will never actually be used on a single-engine airplane, since our prop isn’t full-feathering anyway.

Safety Wiring by an Amateur Mechanic Safety Wiring by an Amateur Mechanic

I tightened and re-safetied the stop plate screws, which took several attempts to get just right. I had to experiment with how many turns per inch to give the safety wire pliers to get an acceptible tension. As you can see from the photos, I think all three wire pairs have a different number of turns per inch.

Since our 0.032” safety wire was a slightly heavier gauge than what was originally installed on the governor, I don’t think my wire wraps are quite as pretty, but I’m happy with them for a first attempt, and I think they’re correct and will do the job.

Installing the Prop Cable Installing the Prop Cable

Next we installed the governor on the engine, and set about affixing the prop control cable to the bracket. This is easier said than done with the cable already installed on the firewall, and I think we nearly shredded the rubber dust gasket on the cable end with all of our test-fitting.

Control Arm Safety Wire Control Arm Safety Wire

The stickiest problem we ran into when installing the prop cable was the fact that it was impossible to fit the AN3-11A bolt and associated washers and spacers onto the governor control arm. Since this bolt is inserted from front to rear, it simply wouldn’t clear the edge of the governor stop plate enough to get it inserted into the control arm hole.

The only solution we came up with was to loosen the tension bolt on the control arm and slide the arm almost all the way off its knurled spindle. Only then could we get the AN3-11A bolt to slide in. Once all the hardware was installed, I had to re-safety wire the tension bolt – with the entire assembly installed on the back of the engine.

Prop Governor Installed Prop Governor Installed

In the end everything turned out fine and we got the cable travel we wanted. Any additional tweaking of the RPM settings will have to be accomplished once the engine is running.

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