Below is from the Instrument Flying Handbook, talking about a turn and slip indicator. Is it me, or is this confusing:
How is it that a standard rate turn is when the need lines up with the doghouse AND when it is deflected one needle width from the center alignment mark?
The dial of these instruments is marked “2 MIN TURN.” Some turn-and-slip indicators used in faster aircraft are marked “4 MIN TURN.” In either instrument, a standard rate turn is being made whenever the needle aligns with a doghouse. A standard rate turn is 3° per second. In a 2 minute instrument, if the needle is one needle width either side of the center alignment mark, the turn is 3° per second and the turn takes 2 minutes to execute a 360° turn. In a 4 minute instrument, the same turn takes two widths deflection of the needle to achieve 3° per second.
How is it that a standard rate turn is when the need lines up with the doghouse AND when it is deflected one needle width from the center alignment mark?