Here are a few things to check with your heli on the bench top before your next flight.

1) Servo direction: When you push the rudder stick to the right, the tail rotor pushrod should move forward. If the push rod moves backwards with right rudder, reverse the servo operation on your transmitter.

2) Proper tail rotor blade neutral: With the rudder stick centered and trim set to center, the square base of the blade roots should be flat and lined up with each other. A picture is worth a whole pile of words here, so please take a look at the jpg I stole from page 59 of the gas construction manual. This position is of course approximate and in flight trim adjustments will be necessary, but it will get you very close. (TR Blade Neutral Position.jpg)

3) Proper bell crank positions: First off with the rudder stick centered and the blade roots lined up as in step 2, the bellcrank on the tail rotor gearbox should be at 90 degrees to the tail boom. Since you are using a piezo gyro, odds are you are using some sort of locking collar on the tail rotor eyelet to secure the eyelet, spider, ect. to the short push/pull rod running through the center of the whole tail rotor. If necessary loosen and adjust the position of the locking collar and eyelet on the short push/pull rod in order to position the bellcrank at 90 degrees with the blades aligned as described in step 2.

Also since you are using a piezo gyro, you most likely should have the servo arm setup at 90 degrees to the tail rotor pushrod as well. The LMH instructions call for a 20 degree offset for the tail rotor servo horn in order for some differential throw. This is fine for the stock Arlton gyro, but every piezo gyro I have seen calls for 90 degree servo arm positioning and no differential. This is how I have my LMH set up and it flys great. Please see pictures. With the servo horn adjusted and the radio rudder stick centered, adjust the tail rotor pushrod to the proper length such that both the servo arm and the tail rotor bellcrank are at 90 degrees. (Servo Horn Position.jpg)

4) Proper tail rotor blade deflection: With everything setup as described above (1,2, and 3) push the rudder stick right and left. Ideally you want the tail rotor blades to rotate through the maximum possible deflection in each direction without binding the servo. Servo bind will occur shortly before the slider hits the tail rotor hub (~ 1mm) and near the same deflection in the opposite direction. Proper setup will most likely involve choosing different servo arm holes, tail rotor bellcrank holes, locking collar and eyelet position, or perhaps a little of everything. If your radio has adjustable servo travel of some sort or another, this process goes very quickly. Just make sure when you are all done that the tail rotor blades return to the position described in step 2 when the rudder stick is centered. Also don’t forget to use tread lock on the locking collar setscrew.

5) Binding: It is important that none of the tail rotor components rub or bind in operation. If during the above steps rubbing or binding is found anywhere in the tail rotor pushrod, bellcrank, short push/pull rod, spider, ect. take whatever steps are necessary to correct it. Odds are once you have made it this far, everything is moving quite smoothly.

6) Gyro: I do not know what you are using for a gyro, but make sure you follow its instructions carefully as far as gyro mounting orientation and servo direction ect. Mounting the gyro on the incorrect axis or upside down will make everything go nuts. Some gyros specify a servo direction and have a reverse switch. Make sure this is set properly. Start with a low gain setting and work your way up once the tail rotor is functioning properly. Eventually you will want to increase the gain until the tail rotor begins to hunt (swings back and forth) in hover, and then back the gain down until hunting stops.

If you find all of that is in order, try another test flight. Make sure to charge up those transmitter and receiver batteries. Increase the throttle until you are light on your skids and try short vertical hops. Use the rudder stick trim to get the heli to hover without spinning about the yaw axis. Some yaw will occur while you adjust the throttle up and down. This is normal and will be greatly diminished once you have the gyro set up properly.

If all of this is in order and you are still having trouble, let us know. The short list above comes from several years of my own tail rotor “learning” experiences and suggestions from the excellent litemachines instruction manual.

For what it is worth,
Spiro