Chopper Bill,

I assume the mechanical linkage of the tail rotor is all ok right? You might want to disconnect the tail servo pushrod from the control horn on the tail rotor gearbox and just move the horn by hand a bit to make sure everything is good.

It is also pretty easy to check to see if the servo looks good and the gyro is shot by removing the gyro from the loop. Just unplug the gyro from the receiver and servo then put the servo wire directly into the appropriate connector. Turn on your radio gear and slowly move the rudder stick back and forth. If all is well you should see the servo follow your stick motions slowly and smoothly. If there are any sticky spots, glitches, reduced travel, strange noises, or the like then you probably have messed up the servo.

Often it is possible to strip just one tooth of a servo gear and not even notice the problem. Later on down the road that tooth will most likely find its way into the rest of your servo gears and jam the whole works up at an inappropriate moment, like when you are showing off in front of the boys… Go ahead and take apart the tail rotor servo. I would do this after any crash involving the tail rotor (or that seems to affect its operation) and this only takes a few minutes. It very well could be your gyro, but a set of gears for the servo are relatively cheep and they may ALSO be messed up anyway

Take the servo off the crutch. Take the servo horn off of the servo, holding onto the horn as not to back drive the servo gears. Take the four little screws out of the bottom of the servo case. The servo case will have three sections. You can keep the bottom and middle sections together if you want by holding them between your two fingers while you pull off the top. The bottom and middle contain the motor and electronics and will need no servicing. If you want to take a peek in there feel free, just don’t tug the short wires out between the controller board and the motor. Once you have the top off you should see the gear train. There will be a “large” final gear that goes through the outer case and is normally attached to the servo horn. Pull this one off carefully trying not to send the rest of the gears flying. You will notice that this last gear fits onto its notched shaft in only one orientation. This provides the position information for the feedback loop on the controller board. All of the other gears will slide off of their shafts very easily. You can easily keep track of which gears assemble in which order in the little gear train by lining them up neatly in a row as you take them off. When all of the gears are off, take a look at each and see if there are missing teeth. Normally, if there is a problem, the teeth will shear off of the large final output gear or the one before it. If teeth are sheered off, they will be floating around in the top portion of the servo case. It is important to get all of the little bits out and have everything spic and span so debris will not jam the gears up. If all the gears look good, great start reassembling. If some are messed up, order yourself a replacement metal gear set and you will essentially never have a problem with them again. Upon reassembly just put the gears back in the reverse order you laid them out. When it is time for that final gear, make sure it lines up correctly with the little notched shaft and press it on. This is often easiest if you gently turn the notched shaft to some easily repeated 90 degree orientation to the case sides and then put the gear on over that. If the final gear does not press on, it is probably not lined up. With the last gear on hold the whole case together, being careful not to have any wires poking out of the bottom section, and put the four bottom screws back in. The whole thing will probably take about 10 minutes including time spent poking around for your own amusement. You could probably do this in 5 minutes pretty easy.

Best of luck tracking down the problem. I am sorry if it is the gyro as those things are expensive. You may want to take a good look at your gyro mounting location and see if there is a more secure solution. There may be a better place to put the gyro, or perhaps the little gyro table could be more securely attached. In any case, being able to avoid the same damage in the future would be very nice I imagine If it is any help, which I doubt, I put my gyro right where the electric guys have the electric motor. It is very protected in that corner and has never come loose in flight. Perhaps there is some other place up front that would work for your crutch.

For what it is worth,
Spiro