Gyros and flybarless units

A gyro is a sensor that detects rotation. In an RC model, a gyro feeds a small computer that corrects any rotation you didn't ask for, far faster than your thumbs could. Gyros are why modern RC helicopters are so much easier to learn than the ones from twenty years ago, and why beginner planes can now rescue themselves.

Tail gyros: rate mode and heading hold

A helicopter's main rotor tries to spin the body the opposite way. The tail rotor counters that, but the torque changes every time the throttle or pitch changes. A tail gyro senses the body turning and corrects the tail rotor instantly.

• Rate mode resists rotation but lets the tail drift slowly, like the old mechanical gyros.
• Heading hold (also called heading lock) remembers where the tail was pointing and returns it there. This is the normal mode on modern helicopters.

From flybar to flybarless

Older helicopters had a flybar: a weighted bar across the rotor head that acted as a mechanical gyro, damping the rotor's response so it was stable and controllable. It worked, but it added parts, drag and setup work.

A flybarless unit (FBL) replaces the flybar with three-axis electronic gyros that sense the helicopter's movement and drive the swashplate servos directly. The result is a crisper, more efficient and more precise helicopter, and stability modes that weren't possible before. The trade-offs for buying and reviving older models are in flybarless vs flybar helicopters.

Common flybarless units

UK prices checked October 2026, from Model Helicopters UK where listed.

Align's own GPro and 3GX units are no longer sold; Align now supplies the Microbeast PLUS in its combos.

Stabilisation and rescue modes

Beginner helicopters and planes use the same gyros, plus an accelerometer, to know which way is level:

• Self-levelling (stability) mode limits how far the model can tilt and brings it back level when you let go of the sticks.
• Altitude hold uses a barometer (and on some scale helicopters an optical-flow sensor) to hold height.
• Panic recovery or rescue flips the model upright and levels it at the press of a switch.
• GPS on some helicopters adds position hold and return home.

These modes make learning far easier, but they can hide bad habits. See gyro-stabilised RC planes for when to turn them down.

Setup that matters

1. Mounting. The unit must sit flat and square to the frame on the supplied pad, isolated from vibration, with its cables free so they can't tug on it.
2. Orientation. Tell the unit which way up and which way round it is mounted.
3. Servo centres and swashplate level. Done with the unit's setup menu, as described in swashplate levelling.
4. Cyclic and collective limits. Many units ask for a reference cyclic pitch figure: different makes ask for different values, so follow the manual.
5. Correction direction. With the helicopter powered but the motor disabled, tilt and turn it by hand and check the swashplate and tail correct the opposite way. A reversed direction makes the helicopter flip instantly on take-off.
6. Gain. Start at the recommended value and adjust in small steps.

Symptoms of a wrong setup

More on tail faults in tail spinning and tail wag.

Plane stabilisers

Plane systems such as Horizon's AS3X and SAFE, FMS Reflex and Arrows Vector work the same way but correct the ailerons, elevator and rudder. AS3X-type systems smooth out gusts while leaving the plane fully controllable; SAFE-type beginner modes add angle limits and self-levelling.

How the servos behind all this work is covered in RC servos explained. For the rest of the electronics, see the Electronics hub.