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

9. Fatigue. Degradation of detection performance during a search
can be significant. The sweep widths given in Appendix D and
Volume II are adjusted for a normal amount of crew fatigue.
If search crews are excessively fatigued, sweep width should
be further reduced by 10 percent.
D. EPIRB/ELT Sweep Widths
1. The detection range data obtained from various sources may be
tabulated as maximum, average, or minimum ranges:
a. Maximum detection range - range at which a target is
first detected which is the maximum of a series of such ranges
taken on the target.
b. Minimum detection range - range at which a target is
first detected which is the minimum of a series of such ranges
taken on the target.
c. Average detection range - range which is the average
of a series of ranges at which a target is first detected.
2. The following guidelines, listed in order of preference, are
recommended for developing an EPIRB/ELT sweep width:
a. When minimum detection range is known: W = (1.7) x
(minimum detection range).
b. When average detection range is known: W = (1.5) x
(average detection range).
c. When maximum detection range is known: W = (1.0) x
(maximum detection range).
d. When no detection range is known: W = (0.5) x
(horizon range), using horizon range table (Table 5-8).
3. If search aircraft VHF/UHF antennas are located on top of the
aircraft or in the tail, the sweep widths determined by these
rules should be reduced by 25 percent.
4. Sweep width should be cut in half if searching in mountainous
regions.
E. Radar Sweep Widths
1. Radar is primarily used for maritime search. Most aircraft
radars available for SAR would be unlikely to detect typical
search objects on land except for metal wreckage or vehicles
in open desert or tundra. Sweep width depends on the type of
radar, height of eye to the horizon, environmental clutter and
noise, radar cross section of the target, radar beam
refraction due to atmospherics, and sensor operator ability.