Tail spinning and tail wag

Tail problems are the most common helicopter complaint I've dealt with. The good news is that the causes are few and predictable, and most are cheap to fix.

Why the tail matters

The main rotor tries to spin the body in the opposite direction. The tail rotor pushes against that, and the gyro adjusts the tail many times a second to hold the heading. If any part of that chain is weak or wrong, the tail can't keep up. The full picture is in how an RC helicopter works.

Spinning on take-off

The helicopter pirouettes as it lifts, usually always in the same direction.

Check in this order:

1. Gyro direction. With the motor disarmed, swing the tail by hand one way. The tail rotor pitch (or tail motor) should correct the other way. If it's reversed, the gyro makes the spin worse. Reverse it in the gyro or flybarless unit settings.
2. Tail motor (small helicopters). A worn brushed tail motor can't make enough thrust. If the spin has got worse over time, this is the likely cause.
3. Tail belt or drive. A slipping or stripped belt, a broken tail gear, or a stripped torque tube gear. Turn the main rotor by hand: the tail should turn too, without slipping.
4. Tail linkage. The tail pitch slider and pushrod should move freely across the whole range. Binding stops the gyro from correcting.
5. Tail servo. Check it moves smoothly and quickly. See RC servos explained.
6. Tail blades. Mounted the right way round and undamaged.

Tail wag

The tail flicks quickly from side to side in the hover or at the end of a turn.

• Gain too high. By far the most common cause. Lower the tail gain a few points at a time until the wag stops.
• Slow or sloppy tail servo. A servo that can't keep up makes the gyro overshoot.
• Binding linkage. Stiff movement causes the same overshoot.
• Vibration reaching the gyro or flybarless unit. Check the mounting pad and the blades.

Tail drifts or blows round in wind

• Gain too low. Raise it in small steps.
• Rate mode instead of heading hold. Check the gyro mode.
• Worn tail parts with too much slop.

Coaxial toys that rotate

Coaxial toys have no tail rotor; they turn by speeding one rotor up and slowing the other. A slow constant rotation is usually one motor weakening. Adjust the rudder trim; if it keeps getting worse, the motor needs replacing.

After a crash

Tail parts are among the first to break in a crash: tail blades, the tail boom, the belt, the slider and the servo. See after a crash: checks and repairs. For other faults, use the RC helicopter troubleshooting guide, and see gyros and flybarless units for gain settings. Back to the RC helicopters hub.