JP 3-50 National Search and Rescue Manual Vol I - US Navy

Figure E-1. Aircraft SRU Crosslegs
6. Aircraft searching time
a. Unless winds are calm or perpendicular to the
searchlegs, times for flying the two directions will be
different. The searchlegs will usually be designated
"downwind" and "upwind". The formula for computing times
required to fly one half of each searchleg is given in pars.
C3, C4, and C5.
b. Times t1, t2, and t3 are given to the aircraft before
beginning the pattern. If radar contact with the aircraft is
lost during the search, these times may be used to determine
time to turn for the aircraft.
7. Pattern timing
a. The aircraft and vessel should restart their elapsed
time clock or stopwatch every time the aircraft passes over
the vessel. The second half of each searchleg is timed by
both the aircraft and vessel. When the computed time (t1 or
t2) has elapsed, the aircraft should start its turn onto the
crossleg.
b. In the CSC pattern, the aircraft uses this timing
procedure to determine its own time to turn. The vessel may
use the timing required for the aircraft to fly from overhead
to overhead as a check on the aircraft's completion of full
searchlegs on both sides of the vessel. The timing is t1 + t2
+ t turning or t1 + t2 + 60 seconds.