Turn Coordinator: Understanding Roll & Turn Rates

[rajeshmarndi]

how does the miniature airplane in the turn coordinator in airplane is able to show both roll rate and turn rate.

I mean it could either show roll rate or turn rate, how could it tell both roll rate and turn rate from one indication( miniature airplane)

 

[LostConjugate]

It looks to me like it is two different devices.

 

[cjl]

I think it just works based on perceived net acceleration. If the perceived net acceleration is straight down (relative to the aircraft), the turn is coordinated.

 

[rajeshmarndi]

ignore the center ball, it only give quality of turns.

 

[LostConjugate]

ignore the center ball, it only give quality of turns.

So the center ball isn't what shows you your rate of turning?

 

[Delta Kilo]

It's supposed to show turn rate, reacting to roll rate is a secondary effect. So it overshoots a bit when rolling into and out of turn. The markings correspond to one "standard turn" which is 3 degrees/sec (180deg turn in 1 minute). The balance ball underneath is to show the direction of the g-force, the same as bubble in a spirit level. Unless you intentinally doing sideslip, the ball should be in the middle. The pilot would enter a turn and then count required number of seconds while maintaining turn rate with ailerons and keeping the balance ball in the middle with rudder pedals.

It's all here: http://en.wikipedia.org/wiki/Turn_coordinator

 

[K^2]

Basically, the answer is that the gimbal for the gyro is at an angle, so both roll and yaw produce torque around the gimbal, which is represented by the change of the angle of the little airplane on the coordinator. If the gimbal was horizontal, the coordinator would only respond to yaw (which is the case in turn-and-slip indicator), and if the gimbal was completely vertical, the coordinator would respond to rolls only.

 

[rajeshmarndi]

K^2: yes the rotor axis is tilted 30 deg upward from the longitudinal axis, i understand if it the axis is horizontally placed it react to yaw movement , but how does it allow to sense roll movement when the axis is raised.

also i do not understand how to know if it is a roll or a yaw from the instrument. Isn't that it need two instrument for this, as they are not the same things.

i only know that, initially it shows roll rate and when the bank angle is established, it shows rate of turn, but do not grasp it.

 

[K^2]

Gyroscopic effect. If you try to turn the gimbal in the way that affects gyro's plane of rotation, the gyro rotates around the gimbal. Since the gimbal is tilted, both yaw and roll will result in this.

You never really need to know both roll and yaw rate at the same time. If you are rolling, your yaw rate is rapidly changing.