GYRO

A gyro acquires significance only when it starts moving/ revolving.

A non rotating gyro is of no importance.

FORCE – creates a linear movement.

TORQUE – creates a rotating movement.

RIGIDITY – is the reluctance of the gyro to move, or when the gyro axis continue to point in the same direction, even when the plane on which it is mounted is made to rotate.

PRECESSION – is the tendency of the gyro to move. It is opposite of the Rigidity.

Precession will cease when the direction of the applied force and the direction of rotation of the gyro coincide.

Gyro wander

  1. Real Wander – occurs due to gyro wear, turbulence etc.
  2. Apparent Wander – occurs due to the rotation of the Earth, and the movement of A/c on the Earth.

Drift in horizontal plane is called DRIFT and can be calculated to be as 15.04 sine lat/ hour

Drift in vertical plane is called TOPPLE and can be calculated to be as 15.04 cosine lat/ hour

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HORIZONTAL AXIS GYRO

At Poles Max DRIFT No TOPPLE

At Equator No DRIFT Max TOPPLE

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VERTICAL AXIS GYRO

At Poles No DRIFT No TOPPLE

At Equator No DRIFT Max TOPPLE

Axis North/South No TOPPLE

Axis East/West Max TOPPLE

In Northern hemisphere due to gyro drift the gyro readings will decrease in relation to magnetic compass.

In Southern hemisphere the gyro reading will increase in relation to magnetic compass.

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ARTIFICIAL HORIZON- EARTH Gyro- Vertical Axis Gyro

DIRECTIONAL GYRO INDICATOR-Tied Gyro- Horizontal Axis Gyro

TURN AND SLIP INDICATOR- Rate Gyro- Horizontal Axis Gyro

INERTIAL NAVIGATION SYSTEM/AUTOPILOT- Ring Laser Gyro/Space Gyro

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GYROSCOPE

A gyroscope has 2 properties.

  1. Rigidity – Rigidity is the reluctance of gyro, to change the direction of its spin axis. The principle of Rigidity is based on Newton’s First law of motion which states that a body continues to remain in state of rest or uniform motion unless an external force is applied to change that state. Magnitude of Rigidity is directly proportional to the speed of the wheel, faster it spins, the greater the rigidity it acquires. It is also proportional to the moment of inertia of the wheel. Rigidity is the reluctance to move.
  2. Precession – Precession is when a force is applied to a spinning wheel that force does not act at the point of application, but it acts at a point which is 900 from it in the direction of the spin. In order to precess a gyro we must over come its rigidity. The higher the speed, the greater the force required to precess it. Similarly the larger the moment of inertia, the greater the force required.

Precession is the tendency to move.

Rigidity is the reluctance to move.

Precession is the tendency to move.

Gyro Wander is deviation of the gyro axis from its set direction and is termed as Gyro Wander.

Gyro Wander is of 2 types.

  1. Real Wander ­- Real Wander is due to wear in gyro, turbulence, friction etc. These errors are not constant, they vary with time.
  2. Apparent Wander – Apparent Wander is due to the movement of Earth because gyro always point at a fixed point in space, but the Earth is moving, it appear to us that gyro has changed direction.

Apparent wander in horizontal plane is Drift.

Drift is 15.04-cosine latitude per hour.

Apparent wander in vertical plane is Topple.

Topple is 15.04 Cosine latitude per hour.

Horizontal Axis gyro

At Poles      Maximum Drift No Topple

At Equator   No Drift Maximum Topple

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Vertical Axis gyro

                         At Poles      No Drift No Topple                           

At Equator   No Drift Maximum Topple