Turn and Slip Indicator (TSI)

Wg Cdr Rajagopal

Turn and Slip Indicator

Index

Introduction to Turn and Slip Indicator

  • Turn and slip indicator consists of a turn indicator and a slip indicator
  • Turn indicator has a horizontal rate gyro which measures rate of turn
  • Horizontal rate gyroscope measures rate of turn around the vertical axis
  • Turn indicator has lower rotor speed to use the property of precession
  • Low RPM reduces rigidity and increase precession
  • Slip indicator is a pendulous device indicating balance during turn
  • Turn co-coordinator is an advanced form of turn and slip indicator

Rate of Turn Indicator

  • Turn indicator has a single gimbal rate gyro with one degree of freedom
  • Spin axis of gyro is aligned to the horizontal axis of aircraft
  • The gimbal is attached to aircraft using calibrated springs
  • The frame turns with only yawing movement of the and not due to bank
  • Torque during turns creates a secondary precession to bring equilibrium
  • At equilibrium, the spring tension is proportional to the rate of turn of aircraft
  • The tension of calibrated spring at equilibrium measures the rate of turn

Failure Warning Device

  • Speed variation causes false indications due to incorrect rate of precession
  • Slow down of rotor speed over indicates faster rate of turn
  • Speed up of rotor speed under indicates slower rate of turn
  • Electrically driven rate gyro has a red flag signifying power failure warning
  • Turn indicator has lower rotor rpm to use the property of precession
  • Low RPM reduces rigidity and increase precession

Slip Indicator

  • Slip indicator indicates state of balance during turns
  • The indicator has a solid ball in a sealed liquid filled curved transparent tube
  • The ball experiences the same centrifugal force as that of aircraft
  • The weight of ball and centrifugal force produces a resultant force
  • The resultant force and the lift are exactly opposite to each other
  • In a balanced turn, this force acts exactly along the vertical axis
  • Slip indicator shows a balanced turn by the ball in the centre or bottom

Interpretation of Slip Indicator

  • Resultant force is a vector addition of gravity and centrifugal force
  • Turn is balanced if the ball is in the centre
  • The resultant force lie in the aircrafts vertical plane
  • Turns with insufficient bank will displace the ball outside of the turn
  • Aircraft and ball are skidding outside the turn
  • Turns with excessive bank will displace the ball inside of the turn
  • Aircraft and ball are slipping inside the turn

Turn Coordinator

  • Turn coordinator is specifically designed to execute a rate one turn
  • Rate one turn means a turn of 180 degrees per minute
  • Turn coordinator has a rate gyro inclined at 30 degrees to longitudinal axis
  • The instrument is sensitive to bank as well as to yaw
  • Actuating pin transmits information to display much faster

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