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An aircraft in the northern hemisphere is making an accurate rate one turn to the right. If the initial heading was 135°, after 30 seconds the direct reading magnetic compass should read:
  • A
    225°.
  • B
    more than 225°.
  • C
    more or less than 225° depending on the pendulous suspension used.
  • D
    less than 225°.
Rate 1 turn = 3°/Sec.
30 sec of rate 1 turn => 3 x 30 = 90°

Turning in a clockwise direction (to the right) from 135° means that you will turn towards the South. According to the acronym ‘UNOS’, you will overshoot South, which means that if you want to turn towards a given heading you need to stop your turn later (=overshoot). But in this question, there’s no particular heading you want to achieve, as your turn is based on time (30 seconds).

Therefore, you just need to visualize how the compass card is reacting to understand what it should read after 30 sec of turn. The card is lively and is ahead of the turn, which means that for any given angular displacement from your origin, the card will indicate a higher value of magnetic heading. For example, after 20 seconds you have turned from 135° to 195° but the card is not indicating 195°, but rather 215° (it is ahead of the turn and is indicating a higher value as 195° < 215°). In the same way, after turning for 30 seconds, you have in reality reached heading 225°, but since your compass is ahead of the turn, it will indicate a value of let’s say 245° (more than 225°).

Note: The opposite will happen if you make an anti-clockwise turn. The card will indicate a lower magnetic heading while lagging behind the turn.

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