Tell us about gyros and wander.
Due to it’s rigidity, the spin axis of a perfect gyro should continue to point in a fixed directio. Any movement away from this direction is known as Gyro Wander.
Real Wander occurs when the gyro actually moves relative to a fixed point in space. It may be real drift or real topple. It is caused by frictional forces giving unwanted precession. Max error allowed is 4 degrees per 15 minutes, or 16 degrees per hour.
Apparent Wander occurs when the spin axis of a gyro appears to change direction to a earthbound observer, such as when the earth rotates. Apparent wander also occurs when the gyro is transported across the earth west or east. This is known as Transport Wander.
Transport wander is when flying a great circle (curved path) the gyro thinks your trurning when your not. Straight line on a sphere can seem curved.
Apparent Drift = 15 x sine of the latitude / hour
Apparent Topple = 15 x cosine of the latitude / hour
- There are four types of gyros:
- Space Gyro – Two gimbals, freedom of movement about 3 axes.
Tied Gyro – Two gimbals, freedom of movement in 3 planes but controlled by an external force. Directional Gyro (DI)
Earth Gyro – Two gimbals, freedom of movement in 3 palnes but controlled by gravity. Artificial Horizon.
Rate Gyro – One gimbal, freedom of movement about 2 axes, 1 of which is the spin axis. INS platforms make use of rate gyros. Turn Co-ordinator.
- Earth Rate : 15 x sin mean lat
- N: - S: +
- Latitude Nut: 15 x sin Latitiude of setting
- N: + S: -
- Transports Wander EAST: N - S +
- Transport Wander WEST: N + S -
Real Wander: As in operating manual