I just finished the break-in on the motor in my concept 30 SR. I am anxious to get it off the ground, but when I try it does something weird (to me anyways). Whenever I get to about half to 2/3 throttle (just before it lifts off) the tail swing around 180 degrees. I thought the gyro was supposed to prevent this. What could be the problem? The gyro is a Futaba FP-G154 rate gyro.

Does it just swing 180 then stop?

If so, then the gyro can't deal with the torque required to accelerate the main blades up to flying speed. Increase the throttle more slowly, and compensate with right rudder. Or, just let it swing, and once it's up to speed, and light on the skids use the rudder to align it the way you want.

While the head is coming up to speed, the tail is also running slowly, so it can't generate enough thrust to compensate for the accelerating main rotor if you increase throttle too quickly. Once the tail rotor is up to speed it can do its job properly in response to commands from the gyro.

If it just keeps on spinning until you let the throttle off, you probably have the gyro reversed. There is a switch on it somewhere labelled NOR/REV. Move it to the other position. A reversed gyro will move the tail rotor the wrong way, adding to any yaw motion instead of stopping it.

Thanks for the reply, I'll give it a try. If the gyro is reversed will it also reverse the rudder servo or not?

The gyro being reversed will not reverse the rudder servo just the way the gyro reacts to an outside influence. To check it on the bench turn everything on and grab the heli by hand and rotate it. The gyro should give the opposite input than the direction you rotated the heli. When I was learning (15 years ago) I had the gyro reversed and after 3 months of learning to hover I was finally able to hover for about 20 seconds (with the gyro reversed). One day I decided that if it was this hard with the gyro I thought I'd try it without the gyro on. Imagine my amazment when I was able to bring it into a hover for over a minute the first time. I finally figured out the problem and switched the gyro reverse switch - duh!

If you have your gyro set to heading hold, it may be that your tail rotor is at full lock before you start increasing the throttle. The tail servo will not recenter when in HH mode; it just sits at the last position it was in before yaw movement stopped. So....if you swing the tail around when carrying the heli to the launch pad, the gyro may go to full lock in an effort to compensate, and just stay there after you set the heli down. Once the tail rotor gains enough speed to create authoritative thrust, it will want to swing the heli around until the gyro catches up and stops it. Bottom line, check Phil's suggestions too, and ultimately, you will find yourself getting used to feeding in rudder as the rotor is spooling up to keep the heli straight. The gyro is not very effective at locking the tail until the heli is up to speed and off the ground.

Re the reverse switch: The servo reverse function on your radio will control which way the transmitter tells the servo to go based upon stick input. The reverse switch on the gyro controls which way the gyro tells the servo to go based upon yaw movement. They are totally separate functions and one does ont inflluence the other. Here's how to check each:

1. Move the stick to the left and check to see whether the tail blade pitch increases or decreases. Note which way the tail rotor spins and whether the stick movement will create the desired thrust direction to move the NOSE in the direction of the stick. If not, use the servo reverse function on your transmitter to change it.

2. Center the tail rotor servo and watch what it does when you move the tail of the heli to the left (nose to the right). It should move in the same direction as it does when you move the stick to the left. If not, flip the reverse switch on the gyro.

Thanks again for the replies. I think the servo is centered and is moving the correct direction, but I'll double check. And I'll try the gyro reversed. I am trying to avert major catastrophe before I get it in the air, and you guys are a big help.

check to see if you have the revo mix reversed this will do it to also too much pitch you should be lifting off at half not 2/3.s. also see if the tail pitch lever is 90* to the boom when at half stick with revo mix turned off and make sure tail blades are not reversed.