comdtinst m2400.1f - US Coast Guard Response Boat-Medium

CHAPTER 2. SEARCH AND RESCUE
A. General.
1. Initial Communication. Initial communications between
vessels or aircraft in distress and the mobile units
proceeding to their assistance is normally made on the
frequency used by the vessel or aircraft making the distress
call. In the case of merchant vessels equipped for
radiotelegraphy, the initial contact frequency would normally
be 500 kHz. In the case of small vessels voluntarily
equipped with radiotelephone, such as fishing vessels and
pleasure craft, the inter-ship frequencies (see Circuit L2.2)
should be tried after attempts to call these vessels on 2183.4
(2182) kHz and 156.8 MHz have been unsuccessful.
2. Initial Contact. The initial contact frequencies allow the
mobile search and rescue units to establish communications
with aircraft or vessels in distress. After communications
have been established, the selection of a frequency for
handling traffic between the vessel or aircraft in distress
and the rescue units proceeding to assist is the
responsibility of the unit in distress or the station which
has transmitted the distress message for the unit in distress,
except when the control of distress traffic has been
delegated to another station. Communications should be
shifted to available working frequencies as soon as
practicable, except when it is not possible to do so because
of a lack of common frequencies. For communications involving
only Coast Guard units regular Coast Guard frequencies should
normally be used. In any event, due regard must be given to
the guard requirements on the calling, distress and emergency
frequencies.
3. Aircraft. The first transmission of an aeronautical distress
message is on the frequency in use for normal communications
with the aeronautical stations at the time of the incident.
For that reason, search and rescue craft proceeding to the
assistance of the aircraft must establish communications on
that frequency. It is necessary that search and rescue craft
obtain pertinent frequency information from the controlling
surface radio station, whether it be an International Civil
Aviation Organization air-ground control radio station or a
controlling military radio station. That frequency normally
will be used for establishing initial communication as well
as for handling ensuing communications between the distressed
aircraft, assisting mobile craft, and the controlling surface
radio station. When a mobile search and rescue unit is within
line of sight range of a distressed aircraft the initial
contact frequency would normally be either 121.5 MHz for
civil aircraft or 243 MHz for military aircraft.
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