# How are gyros used on a turn indicator?

So I understand how precession works, and that gimbals are used to isolate the gyro from outside rotation, however when a yawing motion is applied to the gyro, it'll essentially translate to a rolling (horizontal) motion on the gimbal to turn the indicator.

Since the gyro maintains its plane of rotation, would it be acceptable to say that if I applied force to a gyro, the precession from the gyro would be displayed on the gimbal not the gyro, since it has to maintain its plane of rotation?

To summarize, I'm just wondering how a gyro's precession affects the gimbals or how it affects the instrument if it doesn't affect the gimbals.

Thank you!

The picture given is not complete, it is missing several components. Unlike the other two gyros, the turn coordinator is not allowed to remain rigid in space while the gimbal moves freely around it. The plane of rotation is forced to change with changes in the heading, because of this it does not use a full gimbal. It has one axis other than the gyro core. The housing applying force to the gyro causes precession. In other words, the gyro would like to remain fixed in space but the housing applies force as the aircraft changes heading and bank angle. The resulting precession is restricted by springs.

The higher the rate of change in heading the more torque is generated by the gyro attempting to precess. This force can be measured by the change in spring length, indicated as movement on the gauge. By tilting the free axis up from zero pitch, changes in bank angle will also cause precession. With 90 degrees or a vertical axis the instrument would only precess with changes in bank, angles between 0 and 90 provide a varying mix of the two signals.(Angling the axis down will cause bank to react in the opposite direction, usually this is not desired.)

• Suggestion -- maybe try to be more clear about the fact that "turn rate indicator" and "turn coordinator" are generally not used interchangeably. Change second sentence to "turn rate indicator". Then when you talk about tilting the free axis up from zero pitch to sense roll as well as yaw, note that this is the main thing that distinguishes a "turn coordinator" from a "turn rate indicator". Lousy name, turn "coordinator", because it tends to imply that it has something to do with detecting sideslip, when in fact the slip-skid ball is present on both types of instruments... Oct 27, 2020 at 9:29