One-Quarter Rule - INSIGHT STRIKE FINDER Pilot's Manual

STRIKE FINDER
Figure 21 (p.27), shows a typical storm system likely to be encountered while
in-flight. The presence of storm activity on the display raises the following
questions:
1) How close is the storm to your plane?
2) Are you going to miss the storm on your current heading?
3) How much should you turn to deviate?

One-Quarter Rule

Strike Finder has a unique feature called the One-Quarter Rule that is used
to determine the "required storm avoidance angle". The following section,
explains and demonstrates, how the One-Quarter Rule is used.
Half Range
Storms at the
track, will have an avoidance distance of one quarter of the Display range.
For example, Figure 22 shows the Strike Finder display in the 200 nm range
view. Using this knowledge, in conjunction with the One-Quarter Rule, the
distance at 30-degrees can be interpreted as being 50 nm or one-quarter
of 200 nm, (see Table 2 for One-Quarter Rule distances and "required storm
avoidance angle" for all range view settings, p.29).
Figure 22. One-Quarter Rule Display
28
Ring, 30-degrees from the aircraft's intended
30˚
One-Quarter
Full Range
DIGITAL WEATHER AVOIDANCE
PILOT'S GUIDE