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

813 Weather Conditions
Weather conditions must be evaluated before SRU dispatch. Clouds,
especially thunderstorms, create turbulence and reduced visibility.
Inadvertent entry into clouds should be avoided. Air currents are
unpredictable and may cause cloud formations to shift rapidly. Since
it is hard to judge distance from cloud formations and cloud movement,
low-hanging clouds and scud should be avoided.
814 Aerial Sightings
In timbered mountainous areas, search objects will often be
obscured by terrain, covered by snow, or otherwise extremely difficult
to locate. The only visible clue to a crash site may be broken tree
tops or a reflection from a broken fuselage or windshield. Anything
that appears out of the ordinary may be a clue. Personnel may be
impossible to see unless they signal or move into an open area. In
these cases, the SRU may prove effective as a loud hailer platform.
820 AIR/GROUND SEARCHES
Prerequisites for a safe and effective mountain search are thorough
preparation and constant aircrew vigilance. Full attention of one pilot
should be dedicated to flying. Only highly experienced pilots should be
permitted to fly mountain searches. Certain precautions and procedures
should be observed in planning and executing a SAR mission.
A. Extreme caution should be used when searching canyons and
valleys. Pilots should maintain adequate terrain clearance and "exit"
plans ahead of the SRU. They should know which way to turn at all times
in case of an emergency, and should be aware of power lines and other
hazards to low-level flight. Searches should be flown close to one side
of a canyon or valley so the entire width may be used if a 180 degree
turn becomes necessary. Aircraft should not enter any valley too narrow
to permit a 180 degree turn.
B. Areas of possible severe turbulence should be identified.
Pilots should determine turbulence and downdrafts before descending to
search altitude or flying close to a mountainside. Wind direction and
air currents in mountainous areas may vary greatly. If turbulence is
encountered, the pilot should take immediate steps to keep from
exceeding SRU structural limits.
1. While turbulence is often associated with thunderstorms, up
and down drafts may be encountered in clear air. In
mountainous terrain, any surface wind will be diverted by
natural obstructions and possibly create hazardous flying
conditions.
a. Orographic turbulence is proportional to wind
velocity and dangerous if severe. Updrafts occur on the
upwind side of slopes and ridges, and downdrafts on the
downwind side. The amount of downdraft depends on the