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

These patterns are variations of the Creeping Line Pattern. If the
only available surface craft is a boat or larger vessel untrained in
directing or coordinating aircraft, the CSC pattern is used. If the
surface craft is a Navy vessel or a Coast Guard cutter, trained in
directing or coordinating aircraft, the CSR pattern is normally used.
E. Search Pattern Vessels
1. Vessel heading and track. The vessel track will normally be
the direction of creep specified in the SMC SAR action plan.
If an ocean current set is present, vessel heading should be
corrected to ensure the desired search track.
2. Vessel speed. The vessel speed (Vs) is adjusted so that the
time required for the aircraft to fly along one complete
searchleg and one crossleg is equal to the time required for
the vessel to advance on crossleg.
3. Aircraft headings and speeds. After the vessel search speed
has been determined, the aircraft wind-corrected headings and
groundspeeds are computed. Most aircraft navigational
computers can quickly provide the wind-corrected headings,
groundspeeds, and times required to fly searchlegs. The
aircraft pilot should be given the necessary information to
allow a check of vessel computations.
4. Aircraft turn diameter. The formula for aircraft turn
diameter (par. C2) is predicated on the aircraft making
standard rate turns (3 degrees heading change per second).
Unlike a surface vessel, aircraft do not experience a
noticeable difference between advance and transfer during the
first 90 degrees of turn. An aircraft starts its turn one-half
turn diameter before the end of the searchleg, and rolls
out of the turn one-half turn diameter down the new searchleg.
The searchleg length equals the straightaway plus one full
turn diameter (L = y + TD), and the crossleg equals the
straightaway plus one full turn diameter (S = x + TD).
5. Aircraft crossleg time
a. The vessel should precompute the time required for
the aircraft to fly the straightaway distance of the crossleg.
This information is included in one of the early advisories
passed to the aircraft after arrival.
b. The aircraft requires 30 seconds to execute a 90
degree standard rate turn. Since the aircraft will be making
two 90 degree turns on each end of the crossleg straightaway
in any creeping line pattern, all maneuvering onto and off of
crosslegs requires 60 seconds plus t3. See Figure E-1.
E-2