| � |
| � |
 |
IAMSAR Manual
|
 |
� |
| � |
|
Communications
2.8 Vessel-Aircraft Communications
|
2.8.1 Civil vessels and aircraft may need to communicate with each other if either is in an emergency situation or performing SAR services. Since these occasions are infrequent, civil aircraft may be reluctant to carry additional equipment for these purposes; incompatible equipment makes communications difficult.
2.8.2 The aeronautical mobile service uses amplitude modulation (AM) for VHF telephony while the maritime mobile service uses frequency modulation (FM). Except for SRUs, most small vessels normally cannot communicate on 3023 and 5680 kHz, or on 121.5 and 123.1 MHz.
2.8.3 The following frequencies may be used between vessels and aircraft when compatible equipment is available.
(a) 2182 kHz. Many vessels, especially fishing vessels, and nearly all ships, are equipped to use 2182 kHz. Some transport aircraft can transmit on 2182 kHz, and aircraft designated for maritime SAR operations are required to carry this frequency. Aircraft may have difficulty calling up vessels on 2182 kHz, as vessels normally guard this frequency through automatic means and are alerted when the radiotelephone alarm signal is transmitted.
(b) 4125 kHz. This frequency may be used by aircraft to communicate with ships for distress and safety purposes. All ships may not carry1his frequency (most SOLAS ships and many other vessels do). If an aircraft needs help from a ship, SAR authorities can notify ships in the vicinity of the situation and ask them, if practicable, to set up watch on frequency 4125 kHz.
(c) 3023 and 5680 kHz. These are HF on-scene radiotelephony frequencies for SAR. Designated SAR aircraft and most civil aircraft carrying HF equipment can operate on these frequencies; they may also be used by vessels (nearly all SOLAS ships) and coast radio stations engaged in co-ordinated SAR operations.
(d) 121.5 MHz AM. This is the international aeronautical distress frequency. All designated SAR aircraft and civil aircraft carry equipment operating on 121.5 MHz; it may also be used by maritime craft. All aircraft are required to guard this frequency, flight-deck duties and equipment limitations permitting.
(e) 123.1 MHz AM. This aeronautical on-scene frequency may be jointly used by aircraft and vessels engaged in SAR operations.
(f) 156.8 MHz FM. This is the VHF maritime distress and calling frequency (Channel 16fcarried by most ships; civil aircraft do not normally carry radios that can use this frequency, but some aircraft that regularly fly over water do, usually in portable equipment. Designated SAR aircraft should be able to use this frequency to communicate with vessels in distress and assisting vessels.
2.8.4 Once alerted, RCCs can often help aircraft make arrangements for direct communications with vessels, or provide a message relay. An aircraft in distress over an ocean area can be expected to contact an ATS unit about the situation on the frequency being used for air traffic control purposes. If ditching at sea is likely, the A TS unit will immediately advise the responsible RCC, which can alert ships in a position to assist and arrange an escort aircraft or other appropriate measures.
2.8.5 Regardless of whether the ship or the aircraft needs help, RCCs can sometimes enable communications between them by asking the ship(s) to establish a listening watch on 4125 kHz if possible, or on 3023 kHz otherwise. The aircraft will attempt to establish communications on 4125 kHz, and if unsuccessful will try on 1021 kHz.
2.8.6 If the threat of ditching subsides, or the vessel no longer needs aid, all alerts must be cancelled immediately. |
| � |
2.9 Survival and Emergency Radio Equipment |
2.9.1 Aeronautical and maritime survival radio equipment also operates on 121.5 MHz, a frequency which can be used for alerting, homing, and on-scene communications, depending on equipment design.
2.9.2 The ultra-high frequency (UHF) 406 MHz is reserved solely as an alerting frequency for some El Ts, EPIRBs, and PlBs. l-band is used for Inmarsat-E EPIRBs.
2.9.3 2182 kHz, 121.5 MHz, and 156.8 MHz may be available for use in vessel and aircraft survival craft.
2.9.4 Many civil aircraft world-wide, especially operating over ocean areas, carry a 121.5 MHz ELT for alerting and homing. SAR aircraft should be able to home on this frequency to help locate survivors. Many ELTs also alert and provide homing signals on 243 MHz to take advantage of military aircraft capabilities. An increasing number of ELTs use 406 MHz alerting signals with one or both of the other two frequencies used for homing. 406 MHz satellite ELTs offer coded identities and other advantages which can reduce SAR response time by up to several hours over what would be possible with non-coded ELTs. Use of these 406 MHz ElTs, Inmarsat-E, or equivalent equipment should be encouraged, and use of ELTs which alert primarily on 121.5 or 243 MHz should be discouraged.
2.9.5 Passenger ships, regardless of size, and cargo ships of 300 gross tons and over must carry radar transponders operating in the 9 GHz band and have to be outfitted with a radar capable of operating on the 9 GHz band.
2.9.6 Passenger ships, regardless of size, and cargo ships of 300 gross tons and over must carry at least two portable survival craft VHF transceivers, and cargo ships of 500 gross tons and over must carry at least three. If they operate in the 156-174 MHz band, they will use Channel 16 and at least one other channel in this band. Portable DSC equipment can transmit on at least one of the following frequencies: 2187.5 kHz, 8414.5 kHz, or Channel 70 VHF.
2.9.7 When carried aboard vessels or other craft, EPIRBs can send signals on one or more of the frequencies 406, 243, and 121.5 MHz or in the L-Band. EPIRB signals indicate that a distress exists and facilitate location of survivors during SAR operations. For this to be effective, searching craft should be able to home on the signals intended for this purpose, or on the alerting frequency itself (which will be non-continuous if it is 406 MHz). Many EPIRBs and EL Ts use the dual 121.5/243 MHz frequencies either for alerting or homing. |
| � |
|
|
2.10.1 Cellular telephones work well for point-to-point conversations within range of supporting cellular networks, and some cellular telephones can shift to satellite communications when they are moved outside terrestrial cells However, these popular, inexpensive, and multi-purpose devices have limitations in emergencies involving SAR Here are some limitations about which SAR authorities should make cellular telephone users in the aviation and maritime communities aware, so they are less likely to abandon use of radios:
- use of a VHF radio in a distress situation for a MAYDAY call not only alerts SAR personnel, but other boats, aircraft or stations within range, often enabling faster assistance from a variety of closer potential rescuers;
- the user must know or look up any needed telephone number if they want to use a cellular telephone for that purpose;
- radio signals can be used effectively to help locate survivors using either land or mobile DF equipment, but cellular telephones require close time-consuming co-ordination with service providers to identify the cell from which a call was placed (usually a 10-15 mile radius);
- VHF radios allow receipt of safety advisories, while cellular telephones do not;
- battery-powered cellular telephones are good for only a limited amount of talk time before batteries need to be changed or recharged; - cellular telephone service providers can deny service to selected cellular telephones without advance notice (eg" for late payment of fees); and
- in disaster areas, cellular systems quickly become saturated with callers, making calls to others in the same area nearly impossible
2.10.2 When receiving an alert via cellular telephone, SAR personnel should obtain the following information
- caller's complete cellular telephone number;
- caller's cellular service provider;
- roam number if needed to recall the user;
- other means of available communications; and
- an alternative point of contact
2.10.3 The caller might be advised to ensure the phone is left on to receive further communications, or agree on a communications schedule. The caller might also be advised that the cellular number may need to be broadcast if an assistance broadcast is made. (Caution should be used in actually broadcasting the number, since this would enable anyone for any reason to call and tie up communications.)
2.10.4 Cellular service providers may be able to provide some of the following help in finding the position of lost or disoriented callers, but the help may not be easy to provide and will involve time delays:
- call trace to the receiving cell while the call is connected, and an estimate of maximum range from the tower;
- approximate position based on assessment of signal strength at several cell sites;
- cell location of the last call placed by the caller; and - notification when a call is made from the user's number (useful in overdue cases). |
| � |
2.11 Special Circumstances |
2.11.1 It helps to have more than one means of communication to account for special circumstances.
2.11.2 Sometimes rescuers on-scene must communicate with each other and survivors by unaided voice or portable radios, especially if survivors are entrapped, other emergencies like a fire or oil spill are also being responded to on-scene, or large numbers of survivors are being rescued or triaged. For these cases, it may be important to:
- plan ahead for how responders from different organisations on-scene will be able to communicate with each other; and
- when practicable, keep noisy helicopters and non-essential aircraft away from the immediate site until they are actually needed.
2.11.3 Emergency plans for aerodromes should include guidance on how multi-agency, multi-jurisdictional communications will be managed and carried out when authorities besides those at the airport must respond to an emergency. One suitable all-risk methodology used in some States is called the Incident Command System (Section 1.12). |
| � |
| � |
|
|
� |
