In Figure 4-40, when the aircraft begins its turn to the left,
the magenta trend indicator elongates proportionally with the
rate of turn. To initiate a half-standard rate turn, position the

Figure 4-40. HSI indicator (enlargement).

indicator on the first tick mark. A standard rate turn would
he indicated by the trend indicator extending to the second
tick mark. A turn rate in excess of standard rate would be
indicated by the trend indicator extending past the second tick
mark. This trend indicator shows what the aircraft's heading
will be in 6 seconds, but is limited to indicate no more than
24° in front of the aircraft, or 4° per second. When the aircraft
exceeds a turning rate of 25° in 6 seconds, the trend indicator
has an arrowhead attached to it.

Trend indicators are very useful when leveling off at a specific
altitude, when rolling out on a heading, or when stabilizing
airspeed. One method of determining when to start to level
off from a climb or descent is to start leveling at 10 percent
of the vertical speed rate prior to the desired altitude.

As the aircraft approaches the desired altitude, adjust the
pitch attitude to keep the trend indicator aligned with the
target altitude. As the target approaches, the trend indicator
gradually shrinks until altitude stabilizes. Trend indicators
should be used as a supplement not as a primary means of
determining pitch change.