What has to be done to replace the trim wheel in my plane?
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Technical Editor:
Changing the trim wheel is easy, but care (and A&P guidance) is needed. The trim is positioned full forward or full aft, and the trim pedestal top cap is removed.
Note that this is the perfect time to re-paint the white indicator needle. Use a heavy-bodied white paint, for best visibility day and night. The brush-in-cap white porcelain touch-up paint is perfect; and it is readily available at most hardware stores.
This is also the perfect time to renew your trim indicator decal, after repainting the top cap with some satin black paint.
Stuff a rag under the roll pin that retains the chain sprocket. The safety wire is then removed from the roll pin. Use a drift punch to tap the roll pin almost all the way out the bottom. Then turn the trim wheel 180 degrees, and use pliers to pull out the pin. Don’t squeeze the pin too hard, and break it. If it isn’t far enough out to enable easy removal, rotate it back down and drift it out a bit more. If you have to pull very hard at all on it, put a small Allen wrench or drill bit inside of it, before squeezing it very hard with pliers. Don’t let it fall into the mechanism below! The rag is there to prevent that; but don’t get the rag caught up in the chain and sprocket, either.
Remove the big cotter pin on the end of the shaft. Have a half-inch drill bit (or other half-inch rod) ready. Use the trim wheel itself to gradually work the shaft out toward the pilot. Be prepared for the spring tension on the trim chain sprocket, as the end of the shaft clears the RH bushing . While using the wheel to hold up the sprocket, after the shaft clears the RH bushing, replace the RH bushing. Then slip the 1/2″ drill or rod through the new bushing, and manipulate it so that it takes up the load on the sprocket, and pushes out the old trim shaft toward the pilot.
Once the sprocket is supported by the temporary rod, remove the old trim wheel, and replace the LH bushing. Then slide in the new trim wheel shaft, pushing out the rod as you go. Reinstall the roll pin, and safety-wire it. Then install the thrust washers and new cotter pin. Put a very thin film of DC4 silicone grease in the spiral groove of the new trim wheel. Take care that the indicator needle reengages the spiral groove in the correct location. If it is ‘off’, just reposition it with needle-nose pliers. Note that this is the perfect time to re-paint the white indicator needle. It is also the perfect time to renew your trim indicator decal, after repainting the top cap with some satin black paint.
Finally. make sure you check for free travel and proper positioning of the indicator, by traversing full forward and full aft trim. The freshly-painted indicator needle should show at the forward and aft limit, as the trim reaches its internal limit stops.