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What is the difference between the attitude indicator and the turn rate indicator?

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Aircraft Systems

What is the difference between the attitude indicator and the turn rate indicator? What in the gyros makes the turn coordinator indicate a standard rate turn even if the bank is 45 degrees and speed is low?

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2 Answers



  1. Gary Moore on Jul 27, 2010

    Take a look at Chapter 3 of the Instrument Flying Handbook – http://bit.ly/9nGY7u

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  2. Steve Pomroy on Jan 14, 2011

    Hi Student Plot.
     
    The short answer to your question is that the attitude indicator represents position, while the turn coordinator indicates rate of change of position.  Not surprisingly, this corresponds to the two fundamental ways to use a gyroscope.  The first is as a position-indicator.  The second is as a rate-indicator.  The different type of information is tied to the way the gyros are mounted.
     
    Position gyros (like the attitude indicator and the directional gyro) use gyroscopes that are mounted in gimbals so that they can remain in a constant plane of rotation — which is enforced by the gyroscopic inertia of the gyros.  As the aircraft rotates, the gyro maintans it’s orientation, and the aircraft rotates around it.  The result is that the relative positions (orientation) of the aircraft and the gyro changes.  through linkages, the new orientation of the aircraft (relative to the gyro) can be displayed on the face of the instrument.
     
    Rate gyros (such as the one in the turn coordinator) work differenctly.  Rather than maintaining a constant plane of rotation, rate gyros are mounted so that they are forced to rotate with the aircraft in a diretion that takes the gyro out of it’s original plane of rotation.  When this happens, gyroscopic precession kicks in and the gyro will try to rotate perpendicular to the aircraft’s rotation.  This precession is constrained by a spring.  But the faster the aircraft rotates in the original direction, the stronger the precession gets.  The stronger the precession gets, the further the spring will stretch, and the further the gyro will displace relative to the aircraft.  This displacement is then displated as a rate on the instrument face.
     
    Cheers,
    Steve
    http://www.flightwriter.com

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