12.40.12(b) . need for, and method of synchronising the HI with the compass; 

Needs to be aligned with the compass before flight and then realigned every 10 – 15 mins juring flight
– push in and turn the slaving / caging knob to change the HI indication to read the same as the compass
– in the air when conditions are calm and compass readings are steady ensure the wings are level then realign the HI with the compass

12.40.12(a) . advantages of a gyroscopic heading indicator (versus a compass); 

Magnetic compass
– is difficult to read in turbulence,
– is subject to acceleration and turning errors
– is difficult to fly accurately on

Gyroscopic heading indicator
– not subject to acceleration and turning errors
– easy to read in turbulence
– loses alignment due to the earths rotation and friction in the gyro

12.40.12. With respect to the heading indicator (or DGI), explain the:

12.40.10(c) . the pilot checks for serviceability. 

– Check power source of the AI
– Suction gauge should be indicating minimum of 4.5Hg suction
– Make sure receiving power if electrically powered

12.40.10(b) . how pitch attitude and bank angle are displayed; 

Pitch Attitude
– indicated by the position of the centre dot of the miniature aircraft relative to the top of the artifical horizon segment

Bank Angle
– indicated by the relationship of the wings of the miniature aircraft to the line representing the artifical horizon

12.40.10(a) . the basic principle of operation (earth gyroscope); 

– Uses the gyroscopic property of rigidty
– Rotor lies flat – it rotates in a plane parallel with the earths surface and is free to move in the other two planes
– Rotor is controlled in such a way that its axis remains aligned with the centre of the earth

12.40.10. With respect to the attitude indicator (or artificial horizon) explain:

12.40.8(c) . state the function, indication and correct use of the coordination 

– check the gyro rotation – a whirrinhg sound and no failure flags if electrically driven / correct vacuum if pressure driven
– correct indications of the turn indicator and coordination ball in a turn while taxiing – turn L, skid R trun R skid L and

12.40.8(balance) . ball. 

12.40.8(b) . differentiate between the different indications of the turn indicator and turn coordinator; 

Function
– indicates the direction of the g- forces

Indication
– movement of the ball indicates any sideways force (slip or skid)

Correct use
When the ball indicates sideways skip – use same side rudder pressure to centre the ball