By ShipCalculators.com · Published 9 May 2026

AIS-SART: AIS Search and Rescue Transmitter for survival craft

The AIS Search and Rescue Transmitter (AIS-SART) is the survival-craft locating beacon that broadcasts a casualty’s position over the VHF AIS frequencies 161.975 MHz (AIS-1) and 162.025 MHz (AIS-2) so that any AIS-equipped vessel within VHF line-of-sight can see the survival craft on its AIS receiver, ECDIS or radar overlay within seconds of activation. Mandated as one of the two acceptable survival-craft locating devices under Regulation 6.2.2 of Chapter III and Regulation 14 of Chapter IV of the SOLAS Convention, alongside the legacy 9 GHz radar SART, the AIS-SART is built on the ITU-R M.1371 AIS Class A protocol that drives commercial AIS transponders, transmitting position through AIS Message 1 reports and an AIS Message 14 safety broadcast for at least 96 hours of continuous operation. The device is the subject of IMO Resolution MSC.246(83) adopted in 2007 and tested under IEC 61097-14, layered on the horizontal IEC 60945 envelope and A.694(17) general requirements; the parallel radar SART standard is IMO Resolution MSC.247(83). The AIS-SART is fitted in survival-craft lockers accessible from the deck within 1 minute, contains an internal GNSS receiver for autonomous position broadcast, activates manually or by water immersion, and carries a 5-year battery shelf life plus 5-year service interval. This article maps the AIS-SART regime to the GMDSS overview, the SOLAS Chapter III life-saving appliances framework, the SOLAS Chapter IV radio communications GMDSS regime, the satellite-based EPIRB 406 MHz beacon, the Voyage Data Recorder VDR, LRIT long-range identification, AIS and ECDIS, the Polar Code, the ISM Code, STCW Chapter VI training, the COLREGs Convention and the ISPS Code; ShipCalculators.com hosts the calculator catalogue covering AIS-SART carriage, battery and service-interval tracking, and VHF detection-range geometry.

Contents

Background: traditional radar SART 9 GHz X-band

The original survival-craft locating device under the GMDSS framework was the 9 GHz radar Search and Rescue Transponder (radar SART), introduced through IMO Resolution A.802(19) of 1995 and revised under MSC.247(83) in 2007. The radar SART is a passive responder: when illuminated by a 3 GHz S-band or 9 GHz X-band marine radar within line-of-sight range, it produces a coded reply consisting of 12 narrow pulses swept across the X-band that appears on the interrogating vessel’s radar screen as a distinctive line of 12 dots radiating outward from the SART position toward the screen edge. The geometry allows the rescuing bridge team to obtain bearing and range without any electronic-position handshake.

The radar SART operates on a passive trigger mechanism: it does not transmit until interrogated, giving an operating life of 96 hours in standby plus at least 8 hours of continuous activation when triggered. The technology has two well-known limits: it depends on the rescuing vessel having an operational X-band radar at appropriate range and tuning; and the on-screen response is anonymous, with no identification beyond the spoke pattern itself. These limits motivated the AIS-based alternative.

SOLAS III/6.2.2 + IV/14 mandate

Regulation 6.2.2 of SOLAS Chapter III requires every survival craft on a SOLAS ship to be equipped with a search-and-rescue locating device complying with the IMO performance standards. The carriage scale is at least one device for every survival craft on a passenger ship, at least one for every survival craft on a cargo ship of 500 GT and above and at least one for every two survival craft on a cargo ship of 300 to 500 GT. The device may be either a radar SART under MSC.247(83) or an AIS-SART under MSC.246(83); the two are alternatives, and many ships carry one of each.

Regulation 14 of SOLAS Chapter IV anchors the GMDSS performance-standard regime, requiring all radio equipment carried under Chapter III or IV to comply with IMO performance standards adopted by resolution. Both AIS-SART and radar SART standards rest on A.694(17) general requirements. Application extends through the no-more-favourable-treatment principle in the Paris and Tokyo MoUs, with non-compliance attracting deficiency code 04114.

MSC.246(83) AIS-SART standard 2007

Resolution MSC.246(83) was adopted at the 83rd session of the IMO Maritime Safety Committee in October 2007 as the performance standard for survival-craft AIS Search and Rescue Transmitters, introducing the AIS-based locating beacon as a permitted alternative to the 9 GHz radar SART. The standard defines the operating frequencies on AIS-1 and AIS-2 at 161.975 and 162.025 MHz, the message format using AIS Message 1 position reports plus periodic AIS Message 14 safety-related broadcasts, the transmission interval of approximately one minute when activated, the 96-hour minimum operating duration, the 5-year minimum battery shelf life, the internal GNSS receiver for autonomous position broadcast, the manual and water-immersion activation mechanisms with inadvertent-activation safeguards, the IEC 60945 environmental envelope and the buoyancy and antenna-upright requirements when floating.

The device must be portable so it can be carried into a survival craft by one person, fitted with a lanyard for tethering once activated, with a bright orange or yellow casing and control surfaces operable by a person wearing gloves. The 2007 adoption was the first formal IMO recognition of AIS technology as a survival-craft locating device, and MSC.246(83) remains the operative reference today alongside MSC.247(83) for the parallel radar variant.

MSC.247(83) radar SART 2007

Resolution MSC.247(83) was adopted at the same MSC 83 session in October 2007 as the revised performance standard for survival-craft radar transponders, replacing A.802(19) of 1995. The 2007 revision tightened X-band detection sensitivity, refined the 12-pulse swept response across the 9.2-9.5 GHz X-band, retained the 96-hour standby plus 8-hour active battery envelope, and clarified activation logic, antenna-upright behaviour when floating, IP rating and inadvertent-activation safeguards.

MSC.247(83) runs in parallel to MSC.246(83): the two devices are alternatives under SOLAS III/6.2.2. The radar SART retains operational advantages in heavy radar clutter where the swept-pulse pattern remains visible despite degraded display conditions, and where nearby vessels carry operational X-band radar but no AIS receiver. The AIS-SART has advantages in identification, automatic alarming and integration with ECDIS, as discussed below.

IEC 61097-14 + IEC 61097-1 testing

The international electrotechnical testing standard for the AIS-SART is IEC 61097-14 (Maritime navigation and radiocommunication equipment, Part 14, AIS Search and Rescue Transmitter), providing test methods and pass / fail criteria for type approval against MSC.246(83). IEC 61097-14 covers AIS protocol conformance with ITU-R M.1371, transmit-frequency stability on 161.975 / 162.025 MHz, Message 1 and Message 14 format, the one-minute transmission interval, the 96-hour duration test, the 5-year shelf-life accelerated-aging test, buoyancy and float-orientation tests, manual-activation force and sequence, water-immersion-activation at specified salinities and temperatures, self-test function and inadvertent-activation safeguards.

The horizontal IEC 60945 standard provides the environmental and EMC envelope shared with other GMDSS equipment: temperature cycling -25 to +55 °C for exposed equipment, vibration, mechanical shock, drop test from 1 m, water spray and immersion, salt mist, solar radiation, and EMC immunity and emission limits. IEC 61097-1 provides the parent generic specification for shipborne AIS equipment, against which IEC 61097-14 imposes the AIS-SART-specific overlay. The class-society type-approval certificate is issued under the manufacturer’s IEC 61097-14 plus IEC 60945 test report by an IACS member society, satisfying SOLAS IV/14 and underpinning PSC verification.

Operating frequencies: 161.975 + 162.025 MHz

The AIS-SART transmits on the same two VHF maritime mobile channels that carry standard commercial AIS traffic. AIS-1 is 161.975 MHz (international channel 87B); AIS-2 is 162.025 MHz (channel 88B). Both are allocated by the ITU Radio Regulations within the VHF maritime mobile band as duplex channels reassigned for simplex AIS, with 25 kHz channel spacing and 9.6 kbps GMSK modulation under ITU-R M.1371.

Sharing the standard AIS frequencies is the single most important design decision behind the AIS-SART, because every commercial AIS transponder, every shore-based AIS receiver and every shipboard ECDIS or chartplotter automatically sees the AIS-SART transmission without any additional equipment, software change or operator action. In contrast to the 406 MHz EPIRB (which requires the Cospas-Sarsat satellite chain) or the 9 GHz radar SART (which requires X-band radar interrogation), the AIS-SART benefits from the dense fabric of AIS receivers already in operation across the world’s fleet, shore stations, satellite AIS payloads and aircraft.

AIS Message 14 + Message 1 broadcast

The AIS-SART transmits two distinct AIS message types defined under ITU-R M.1371. AIS Message 1 is the standard position report, identical in field structure to Class A AIS position reports, containing the device’s MMSI (with AIS-SART prefix 970 under ITU-T E.164), the GNSS-derived latitude and longitude, course and speed over ground, navigation status set to a value indicating SART operation, time stamp and position-accuracy flag. The position is acquired by the internal GNSS receiver during the first transmission cycle and updated continuously thereafter.

AIS Message 14 is a safety-related broadcast message carrying a textual payload. The AIS-SART transmits a fixed ASCII string “SART ACTIVE” (or equivalent) at intervals of typically four minutes alongside the more frequent Message 1 reports. The Message 14 payload renders as a safety-message banner on AIS-equipped bridges, providing immediate operator-readable confirmation without requiring MMSI prefix interpretation. The combined stream gives the receiving bridge both the location (Message 1) and the alert text (Message 14) without further inference.

Transmission interval: ~1 minute when activated

The AIS-SART transmission interval after activation is approximately one minute, with the standard specifying eight Message 1 position reports per minute in bursts distributed across the AIS TDMA frame. The TDMA frame on each AIS channel is 2,250 slots of 26.67 ms duration per minute; the AIS-SART claims eight slots per minute on each of AIS-1 and AIS-2, alternating between channels to maximise reception probability.

The eight-burst-per-minute cadence is a deliberate trade-off. It is high enough to give the receiving bridge a position update every 7-8 seconds, low enough that the battery sustains 96-hour operation, and structured so the transmissions are clearly distinguishable from regular Class A position reports (which transmit every 2-10 seconds depending on speed). The Message 14 safety broadcast is transmitted at the longer interval of approximately four minutes to limit overhead while ensuring the alert text reaches the receiving bridge within a typical watch cycle.

Detection range: ~5 nm small ships, ~30+ nm large ships

The detection range of the AIS-SART depends on the receiving vessel’s AIS antenna height because VHF AIS is fundamentally line-of-sight. With the AIS-SART antenna at ~1 m above waterline and a typical 33 dBm (2 W) AIS transmit power under MSC.246(83), the range scales with receiving-antenna elevation:

Small ship (antenna ~10 m): detection range ~5 nautical miles.
Medium ship (antenna ~25 m): ~10-15 nm.
Large ship (antenna ~50 m): ~20-30+ nm.
Coastal AIS shore station (50-200 m elevation): up to 40 nm.
SAR aircraft (altitude 300-500 m): up to 40-80 nm.
Satellite AIS (S-AIS) payload: continental-scale footprint with revisit-dependent detection probability.

The line-of-sight geometry favours encounters with large container ships, tankers and bulk carriers transiting major shipping lanes with high mast-mounted AIS antennas. The S-AIS layer complements the shipboard layer at the operational expense of revisit times of 30 minutes to several hours.

Battery life: 96 hours minimum operating

The AIS-SART battery must provide 5 years minimum shelf life in standby and 96 hours minimum continuous operating duration at rated transmit power once activated. The 96-hour figure is double the EPIRB’s 48-hour minimum and reflects the operational reality that an AIS-SART is the on-scene homing layer: it must keep transmitting through the entire SAR response window. The cell is typically a lithium-manganese-dioxide primary battery, sealed inside the waterproof casing.

The 5-year shelf life and service interval are aligned, dictating a 5-year replacement or re-service cycle matched to the SOLAS Cargo Ship Safety Radio Certificate cycle. The expiry date is marked on the casing and encoded in the self-test electronics. Battery replacement requires opening the casing, replacing the pack, resealing to maintain the IP rating and re-testing the device. Many operators replace the entire AIS-SART rather than re-service older units, given the modest retail price.

Manual + water-immersion activation

The AIS-SART supports two activation mechanisms required by MSC.246(83). Manual activation is a deliberate user action: the operator removes the unit from its bracket, removes any inadvertent-activation cap or lanyard pull, and presses or rotates an activation control. Manual activation is the typical mode in a controlled abandon-ship sequence where the AIS-SART is carried to the survival craft and activated once embarkation is under way.

Water-immersion activation is an automatic mode triggered by electrolytic contacts that close when wetted by seawater, activating the unit without operator action. This covers rapid-sinking scenarios where the master cannot brief the abandon-ship party. The standard requires the threshold to be deliberate enough to avoid inadvertent activation in heavy weather, with rain-resistant design and continuous-immersion rather than splash-based triggering. Both paths must be clearly labelled in standard pictograms operable by gloved hands, with a separate deactivation procedure so a recovered AIS-SART can be silenced before it adds further false alerts.

Major manufacturers: Jotron, McMurdo, Kannad, Ocean Signal, ACR, Furuno

Principal manufacturers of MSC.246(83)-compliant AIS-SART units under SOLAS type approval include Jotron (Norway, Tron AIS-SART line widely fitted on Scandinavian, North Sea and offshore vessels), McMurdo (UK, Orolia / Safran group, SmartFind S20 AIS-SART line), Kannad Marine (UK / France, also Orolia / Safran, SafePro AIS-SART line), Ocean Signal (UK, ACR Electronics group, rescueME AIS-SART MOB1 and S100 lines), ACR Electronics (USA, AISLink series for survival craft and AIS man-overboard) and Furuno (Japan, AIS-SART models distributed alongside the Japanese-market AIS transponder line). Other manufacturers under type approval include Cobham SATCOM, JRC (Japan Radio Company), Sailor, Weatherdock (Germany), Hangzhou Junda and Zhonghai Communication Equipment (China). Each typically offers a single-unit AIS-SART for survival-craft fitment alongside a personal AIS-MOB variant for individual crew use, with class-society type-approval certificates issued by IACS member societies; modifications to the firmware or hardware typically require re-approval against IEC 61097-14.

Typical price: USD 200-700

Retail price of an MSC.246(83)-compliant AIS-SART ranges from approximately USD 200 at entry level to approximately USD 700 for top-of-the-line units: USD 200-300 entry-level; USD 300-450 typical SOLAS fitments from major manufacturers (Jotron, McMurdo, Kannad, Ocean Signal); USD 450-700 advanced units with chartplotter interface, extended battery, hazardous-area certification or higher IP rating; and USD 250-400 for a related AIS-MOB personal locator (a separate device class). The price point sits substantially below the USD 600-1,500 EPIRB band, reflecting the simpler protocol stack (no satellite chain, no Cospas-Sarsat licensing) and the commodity VHF AIS transmitter at the core.

Lifecycle costs include 5-year battery and service replacement at typically USD 100-250 (often performed by replacing the whole unit), the annual self-test included in the GMDSS radio survey, MMSI registration at typically zero cost, and routine deck-locker inspection. The total 5-year cost of ownership is approximately USD 300-700 depending on service strategy.

Placement in life raft locker (1-minute accessibility)

SOLAS III and the SOLAS LSA Code require the AIS-SART to be stowed in a position from which it can be readily transferred to a survival craft, accessible to crew within approximately one minute from the bridge or muster station. The typical placement is the life-raft locker on an exposed deck, often within the same locker as the life raft itself or in an adjacent dedicated bracket. The bracket must be clearly labelled in IMO standard pictograms, illuminated by emergency lighting, free of obstruction by stores or hose reels, and accessible without keys or tools.

For passenger ships and cargo ships of 500 GT and above carrying multiple survival craft, the standard practice is one AIS-SART per survival craft stowed in or immediately adjacent to that craft’s launching position. For cargo ships of 300-500 GT, the regulation permits one AIS-SART per pair of survival craft stowed centrally. Where the AIS-SART is shared, the pre-departure muster brief and the deck-officer’s safety walkround must confirm the device’s bracket location and condition. PSC inspectors typically check the bracket location and accessibility under deficiency code 04114 alongside the type-approval and battery checks.

Comparison to EPIRB (different technology)

The AIS-SART and the 406 MHz EPIRB are complementary, not competing, and SOLAS requires both on the typical SOLAS-class ship. The EPIRB is a satellite distress alerter transmitting on 406 MHz through the Cospas-Sarsat space segment to alert a Rescue Coordination Centre (RCC) anywhere in the world within less than 10 minutes with ±100 m GPS-encoded position accuracy. The AIS-SART is a VHF on-scene locator transmitting on 161.975 / 162.025 MHz to AIS-equipped vessels within VHF line-of-sight, providing the bridge-team-readable position and textual alert banner driving the local SAR response.

The EPIRB initiates the response by alerting the RCC and tasking SAR assets; the AIS-SART guides responding ships and aircraft to the survival craft within VHF range. Neither alone is sufficient: an EPIRB without an AIS-SART or radar SART leaves SAR responders searching by visual and radar means once they reach the alert position; an AIS-SART without an EPIRB has no global alerting capability. SOLAS mandates the EPIRB under IV/7 and the survival-craft locating device under III/6.2.2 as separate carriage items. The two chains are technically independent, providing redundancy against single-system failure.

SAR chain: SART then ship AIS then ECDIS then bridge then diversion

The operational SAR chain triggered by an activated AIS-SART runs through five stages. Stage 1: AIS-SART activation by manual or water-immersion trigger; the unit acquires GNSS position within typically less than 30 seconds and begins broadcasting AIS Message 1 + Message 14. Stage 2: nearby ship AIS receiver detection: any AIS-equipped vessel within VHF line-of-sight processes the position report; the AIS receiver flags the 970 MMSI prefix as a SART, triggering audible and visual alarm.

Stage 3: ECDIS display: the AIS Message 1 stream feeds the bridge’s ECDIS, where the SART appears as a distinctive symbol (typically a red square or octagon with a ‘X’ marker under IEC 62288) at the casualty position, with a track history as the survival craft drifts. The ECDIS computes the bearing and range from own ship, raises a CPA / TCPA alarm if the SART is on a near-collision relative track, and displays the Message 14 banner (“SART ACTIVE”). Stage 4: bridge alert: the OOW receives audible and visual alarms from the AIS unit and from ECDIS; standing orders require immediate notification of the master. Stage 5: ship diverts: under the SOLAS V/33 obligation to render assistance, the master proceeds at maximum safe speed to the SART position, reports to the responsible RCC, and either takes survivors aboard directly or coordinates with SAR assets dispatched by the RCC.

Relationship to PLB Personal Locator Beacon

The Personal Locator Beacon (PLB) is a Cospas-Sarsat 406 MHz device similar in technology to the EPIRB but registered to an individual rather than a vessel. The PLB transmits the same 406 MHz Cospas-Sarsat distress message detected by the same satellite space segment and routed through the same MCC / RCC chain. The PLB is not SOLAS-mandated under either III/6.2.2 or IV/7, and it should not be confused with the AIS-SART: the PLB is a satellite distress alerter for individuals; the AIS-SART is a VHF locating device for survival craft.

Some flag-State or operator regulations require crew to carry PLBs in addition to the ship’s EPIRB and AIS-SART; this is more common in offshore-supply, expedition-cruise and commercial-fishing fleets. A typical PLB has a 24-hour operating duration, is registered to the individual rather than to a ship MMSI, and is detected by the satellite chain that does not see the AIS-SART. The two devices serve different audiences and use different frequencies; they are complementary in the same way that the EPIRB and AIS-SART are complementary at the ship level.

Relationship to AIS-MOB Man Overboard

The AIS Man Overboard (AIS-MOB) beacon is a closely related device class operating under ITU-R M.1371 on the same 161.975 / 162.025 MHz AIS frequencies, designed for personal use by individual crew or passengers as a man-overboard locator. The AIS-MOB transmits the same AIS Message 1 position report and AIS Message 14 banner as the AIS-SART, with a different MMSI prefix (972) distinguishing personal MOB beacons from survival-craft SARTs.

The AIS-MOB is not the same regulatory category as the survival-craft AIS-SART. The AIS-MOB is governed by IEC 61097-14-2 and operator-specific or flag-State requirements rather than by the SOLAS III/6.2.2 carriage mandate. Many manufacturers (notably Ocean Signal and Weatherdock) offer combined product families that include both an AIS-SART for survival craft and an AIS-MOB for individual crew, sharing the same RF stack and battery technology but differing in the pre-programmed MMSI category, the activation logic and the casing form factor. On a typical SOLAS ship, the AIS-SART covers the SOLAS-mandated survival-craft locating function while AIS-MOB units may be issued to crew for individual MOB protection over and above the SOLAS minimum.

Built-in GPS for position broadcast

The MSC.246(83) standard requires every AIS-SART to incorporate an internal GNSS receiver providing autonomous position fixing, typically tracking GPS as the primary constellation with optional GLONASS, Galileo or BeiDou support. The receiver must acquire a fix within typically less than one minute under cold-start conditions, with the position included in every subsequent AIS Message 1 broadcast. The internal GNSS distinguishes the AIS-SART from typical Class A AIS transponders that depend on an external GNSS feed routed through the bridge.

The internal-GNSS architecture is essential to the AIS-SART’s operational concept: once activated, the unit is autonomous and does not rely on the casualty vessel’s power, navigation feed or AIS data port. The GNSS antenna is integrated into the casing, oriented for sky visibility when floating upright, and the receiver continues to update the fix as the survival craft drifts. The typical AIS-SART fix is approximately ±10 m for a well-conditioned GPS solution, more than sufficient for SAR vectoring.

Lifetime: 5-year battery + service interval

The AIS-SART lifecycle aligns with the SOLAS Cargo Ship Safety Radio Certificate five-year cycle. The standard specifies 5-year minimum battery shelf life and a recommended 5-year service interval for full re-test, battery replacement and re-certification. The expiry date is marked on the casing and encoded in the self-test electronics; a unit with an expired battery or expired service date is non-compliant under SOLAS IV/14 and attracts a PSC deficiency under code 04114.

Service is performed by the manufacturer or by an authorised service agent under the manufacturer’s quality system; the typical service includes battery pack replacement, casing reseal to restore IP rating, AIS protocol conformance retest, GNSS receiver functional check and self-test calibration. The cost of service is often a substantial fraction of the cost of a new unit, and many operators choose to replace the entire AIS-SART at the 5-year mark rather than re-service the existing unit, particularly where firmware revisions for newer SOLAS amendments motivate a full replacement. Annual self-test under IV/13 is mandatory regardless of the 5-year cycle and must be recorded in the radio log.

AIS Class A protocol always

The AIS-SART operates under the Class A AIS protocol as defined in ITU-R M.1371 and extended for survival-craft use in IEC 61097-14, regardless of the AIS class fitted on the parent vessel. Class A is the commercial-shipping AIS protocol mandated under SOLAS V/19 for ships of 300 GT and above, with 9.6 kbps GMSK modulation, Self-Organising TDMA (SOTDMA) slot-management and full message-set support including Message 14.

The reason for the Class A choice is consistent priority handling at receiving stations. Class B is the lower-cost variant used on fishing vessels and leisure craft under the SOLAS V/19 threshold, using Carrier-Sense TDMA (CSTDMA) which yields to Class A traffic. An AIS-SART operating under Class A is always treated with Class A priority, ensuring its position reports are heard even on heavily loaded channels in busy ports. The MMSI prefix 970 triggers the receiver’s automatic alarm logic, distinguishing the SART from regular Class A traffic. The protocol stack is implemented at the AIS-SART’s typical 33 dBm (2 W) RF output, balancing range against battery duration.

AIS-SART symbology in ECDIS

ECDIS systems compliant with IEC 62288 display the AIS-SART using a distinctive symbol that distinguishes the SART from regular AIS targets. The standard symbol is a red square or octagon with a ‘X’ marker rendered larger than the standard AIS triangle, with flashing or pulsing animation to draw bridge attention. The symbol is positioned at the reported latitude and longitude from AIS Message 1; alongside it, the ECDIS displays the MMSI, the position-accuracy indicator, the Message 14 banner (“SART ACTIVE”) and a track history as the survival craft drifts.

The ECDIS alarm logic combines an audible alarm with a visual alarm (flashing symbol plus alert banner). Many systems also raise a CPA / TCPA alarm treating the SART as a target requiring collision-avoidance attention, logged separately from regular AIS-target alarms. The OOW must acknowledge the alarm explicitly; standing orders require notification of the master and immediate action under SOLAS V/33. The combination of ECDIS symbology, AIS-unit audible alarm and radar AIS-overlay alarm provides triple-redundant bridge alerting.

2024 IMO GMDSS modernisation review

The GMDSS Modernisation Plan, adopted by IMO MSC at its 98th session in 2017 and refined through 2024, addressed the long-running concern that the 1988 GMDSS framework rested on technology that had been substantially superseded. Principal changes affecting the satellite-service framework are the recognition of Iridium as a GMDSS satellite-service provider under IMO Resolution MSC.428(98) and the acceptance of the Iridium Certus maritime safety service in 2020.

For the AIS-SART, the modernisation programme has been largely confirmatory: MSC.246(83) has stood up well, and the device is retained as one of the two acceptable survival-craft locating devices under SOLAS III/6.2.2 alongside the radar SART. The 2024 review has considered options including a second-generation AIS-SART with improved GNSS receivers, encrypted authentication to reduce false alerts, VDES integration with higher-data-rate channels, and longer battery life. No successor standard has been adopted as of 2026; MSC.246(83) remains the operative reference.

5G-based emergency systems future

A longer-horizon proposal under discussion at IMO and ITU concerns the use of 5G mobile-network infrastructure as a future complementary maritime emergency layer along coastal corridors, where 5G coastal towers and emerging non-terrestrial network (NTN) layers extend mobile-network coverage offshore. A 5G-capable maritime emergency device could complement the AIS-SART by transmitting on 5G New Radio frequencies, exploiting high data rate, low latency and precise positioning through 5G small-cell triangulation.

The proposal sits alongside VDES-based emergency messaging (using new VHF Data Exchange System channels), satellite-IoT emergency layers (Iridium short-burst data, Globalstar CMC) and direct-to-cell satellite messaging (SpaceX Starlink, AST SpaceMobile). None has yet reached the stage of an IMO performance standard, and the 161.975 / 162.025 MHz AIS-SART under MSC.246(83) and the 9 GHz radar SART under MSC.247(83) remain the operative SOLAS-mandated devices through at least 2030.

Class society type-approval: DNV, LR, ABS, BV, NK, RINA, KR, CCS, RS, IRS

The class-society type-approval of the AIS-SART is issued by an IACS member society on behalf of a flag State, in the same framework as the EPIRB. The IACS societies are DNV (Norway), Lloyd’s Register (LR) (UK), ABS (USA), Bureau Veritas (BV) (France), ClassNK (Japan), RINA (Italy), Korean Register (KR), China Classification Society (CCS), Russian Maritime Register (RS) and Indian Register of Shipping (IRS). Each maintains a type-approval programme covering the IEC 61097-14 plus IEC 60945 envelope.

The certificate is the primary evidence of conformance to MSC.246(83) and satisfies SOLAS IV/14. It identifies the specific model and revision of the AIS-SART plus its bracket and accessories, the IMO performance standard, the IEC testing standards and the 970 AIS-SART MMSI category prefix. Modifications to firmware, battery type or RF stack require re-approval. Recognised non-IACS societies include Polski Rejestr Statkow, Croatian Register of Shipping and Turkish Lloyd, alongside national flag-State authorities operating their own programmes against the same IMO and IEC standards.

PSC inspection: validity + battery + MMSI + service log

Port State Control (PSC) inspection of the AIS-SART is a routine element of visits under the Paris and Tokyo MoUs. The inspector typically checks the physical presence of the AIS-SART (and / or radar SART) in its bracket per the carriage scale of SOLAS III/6.2.2; the type-approval certificate verifying MSC.246(83) and IACS approval; the battery expiry date; the 5-year service due date; the annual self-test record in the radio log; the configured MMSI on the device (970-prefix SART category); bracket location and accessibility for transfer to the survival craft within one minute; and physical condition including casing and antenna integrity.

Deficiencies are recorded under code 04114 (“Search and Rescue locating equipment”) with action codes ranging from minor (rectify before next port) to detention. Common deficiencies are expired battery, lapsed service date, missing type-approval label, mis-configured MMSI, obstructed bracket, missing self-test entries and missing certificate. AIS-SART deficiencies typically appear in the top 50 deficiency codes by frequency in the annual PSC reports of both MoUs.

Tokyo MoU + Paris MoU deficiency code 04114

The Paris MoU (27 European and North Atlantic States) and the Tokyo MoU (21 Asia-Pacific States) operate the principal PSC regimes outside the Mediterranean and other regional MoUs. Both use the harmonised IMO PSC deficiency-code system with the AIS-SART-related code 04114 (“Search and Rescue locating equipment”, covering both AIS-SART and radar SART). Related codes are 04101 (“VHF radio installation”), 04102 (“Satellite EPIRB 406 MHz”), 04103 (“Inmarsat ship earth station”), 04104 (“MF/HF radio installation”) and 04105 (“DSC system”). The codes are listed in IMO Resolution A.1138(31) Procedures for Port State Control 2019.

Action codes range from 17 (rectify at next port) through 17 + RO (recognised organisation to verify rectification) to 30 (detention). An expired battery or service date typically attracts action code 17 (rectify within 14 days); a missing or non-functional AIS-SART on a passenger ship or a SOLAS cargo ship of 500 GT and above attracts action code 30 (detained until rectification). Where the carriage scale requires multiple AIS-SARTs and only one is non-compliant, the PSC officer typically applies a graduated approach reflecting the partial deficiency.

False activation rate and handling

False-activation rates for the AIS-SART are substantially lower than the ~95 per cent false-alert rate observed for 406 MHz EPIRBs, principally because the AIS-SART does not trigger an automatic global SAR response. An AIS-SART transmission is received only by AIS-equipped vessels and shore stations within VHF line-of-sight; there is no satellite chain escalating the alert to an MCC and RCC unless a receiving vessel chooses to relay it. False activations typically self-resolve at the local AIS receiver level: a bridge officer notices the SART symbol on ECDIS, contacts the apparent originator by VHF or AIS Safety Message, and confirms whether the activation is genuine.

Common causes of inadvertent activation are water-immersion sensor wetting during heavy weather or deck washing, manual activation during maintenance or self-test with the user unaware that full activation has occurred, and disposal of obsolete units without battery deactivation. Bridge handling protocols are: attempt VHF and AIS Safety Message contact with vessels in the area, plot the SART track to determine whether it is drifting (likely genuine) or stationary at a known service-yard or landfill (likely false), inform the responsible MRCC, and record the event in the deck log. Crew training under STCW VI must include the AIS-SART handling sequence.

STCW Chapter VI training requirement

Regulation VI/2 of the STCW Convention and the corresponding STCW Code Part A require seafarers nominated to operate survival craft and rescue boats to hold a Proficiency in Survival Craft and Rescue Boats other than Fast Rescue Boats certificate, with training covering the operation of survival-craft locating devices including the AIS-SART. The syllabus mandated under STCW Chapter VI Part A, Section A-VI/2 covers knowledge of MSC.246(83) and MSC.247(83), identification of AIS-SART and radar SART, manual and water-immersion activation, deactivation, battery and expiry checks, transfer to the survival craft within one minute, and post-rescue handling and false-alert avoidance.

Training is delivered by STCW-approved training providers as part of basic safety training and renewed at five-year intervals through refresher courses. Practical assessment includes a hands-on activation drill (typically with a training-mode unit) and a knowledge test on the SOLAS / STCW framework. The master and chief mate are additionally responsible under the ISM Code Safety Management System for ensuring that the deck team’s familiarisation training covers the actual model of AIS-SART carried, with reference to the manufacturer’s user manual filed in the bridge documentation set.

Comparison to radar SART (operational tradeoffs)

The choice between AIS-SART and radar SART under SOLAS III/6.2.2 reflects different operational scenarios. The AIS-SART has advantages in identification (MMSI plus Message 14 banner give an unambiguous textual alert), in automatic alarming (AIS receivers and ECDIS raise audible / visual alarms without operator interpretation), in integration with bridge electronics (position appears on ECDIS, on radar AIS overlay and on the AIS unit display), in range to large vessels (line-of-sight to 30+ nm with elevated antennas), in detection by satellite AIS, and in battery duration (96 hours operating versus 8 hours active for the radar SART).

The radar SART has advantages in performance under heavy clutter (the swept-pulse pattern remains visible despite rain, sea returns or display saturation) and in operation in the absence of AIS receivers (any X-band radar within range will see the response). Many operators carry both across the survival-craft fleet for dual-technology redundancy. The decision is operational rather than regulatory; SOLAS accepts either or both.

Formula, assumptions, and limits

Formula

The principal numerical envelope is set by IMO MSC.246(83) and ITU-R M.1371:

f_{\text{AIS-SART}} = 161.975 + 162.025 \text{ MHz (AIS-1 + AIS-2 channels)}

T_{\text{transmission interval}} \approx 1 \text{ minute when active}

T_{\text{battery, operating}} \geq 96 \text{ hours}

T_{\text{battery, standby}} = 5 \text{ years}

d_{\text{detection, small ship}} \approx 5 \text{ nm}

d_{\text{detection, large ship}} \geq 30 \text{ nm}

T_{\text{accessibility from deck}} \leq 1 \text{ minute}

\text{MMSI prefix} = 970 \text{ (AIS-SART category)}

The line-of-sight VHF detection range to a receiving antenna at height $h_r$ metres above the waterline, with the AIS-SART antenna at $h_t \approx 1$ m, is approximately $d \approx 2.07 \cdot (\sqrt{h_t} + \sqrt{h_r})$ kilometres under standard atmospheric refraction, giving the small-ship and large-ship figures above when $h_r$ is 10 m and 50 m respectively.

Derivation

The 161.975 / 162.025 MHz AIS frequencies were selected through ITU World Radiocommunication Conference frequency management to reuse the existing AIS infrastructure: every commercial AIS receiver and ECDIS sees the AIS-SART transmission without modification, multiplying the deployment leverage of the SOLAS AIS-SART carriage requirement many-fold compared to a hypothetical dedicated-frequency SART. The 96-hour operating duration was chosen to exceed realistic SAR-response timeframes for offshore casualties (typically 4-48 hours from alert to on-scene assistance), with margin for delayed responses in remote areas. The 5-year shelf life and service interval are aligned with the SOLAS Cargo Ship Safety Radio Certificate cycle. The eight-burst-per-minute cadence balances position-update granularity against battery-duration loading. The 1-minute accessibility-from-deck requirement reflects realistic abandon-ship timelines for SOLAS-class vessels with rapid evacuation requirements under SOLAS III/21.

Assumptions

The envelope assumes the AIS-SART is correctly installed in an unobstructed deck-locker bracket, the battery is within its 5-year shelf life and within the 5-year service interval, the device has been tested at the most recent annual self-test and the test record is in the radio log, the MMSI is correctly programmed with the 970-prefix SART category, at least one AIS-equipped vessel is within VHF line-of-sight (typically 5-30 nm depending on receiving-antenna height) within the 96-hour operating window, the GNSS space segment provides usable position-fixing in the operating area, and the bridge of the receiving vessel has functional AIS receiver, ECDIS or chartplotter and an attentive watchkeeper.

Worked example

Consider a 200,000 GT VLCC at 5° N 65° E in the Arabian Sea encountering an engine-room fire that escalates to abandonment. The second mate carries the AIS-SART from its bridge-wing locker to the lifeboat embarkation deck within 45 seconds, well within the 1-minute requirement. The unit is activated manually before lifeboat launching; the internal GNSS receiver acquires a fix within 25 seconds, and the unit begins transmitting AIS Message 1 + Message 14 at the eight-burst-per-minute cadence. A passing container ship of 80,000 GT with AIS antenna at 48 m elevation, transiting 25 nm to the south, receives the first AIS Message 1 within 90 seconds; the AIS receiver alarms, the ECDIS displays the SART symbol with the “SART ACTIVE” banner, and the OOW notifies the master and informs the responsible MRCC by Inmarsat-C. The container ship diverts at maximum sustained speed, arriving on scene approximately 2.5 hours after alert; the AIS-SART continues to broadcast throughout. A separate Cospas-Sarsat alert from the ship’s EPIRB has reached the MRCC in parallel, providing complementary global alerting; the AIS-SART provides the on-scene homing layer.

Edge cases and limits

Principal edge cases are antenna obstruction by ship structure or life-raft canopy, GNSS signal blockage in heavy rain preventing position acquisition for the first several minutes, salt-water bridging of inadvertent-activation safeguards causing nuisance alerts, capsize inverting the AIS-SART antenna, polar conditions reducing battery capacity below the -25 °C IEC 60945 baseline, congested AIS channels in busy ports, coastal terrain shadowing reducing practical VHF range, satellite AIS revisit gaps of 30 minutes to several hours, and bridge-team failure to acknowledge AIS-SART alarms dismissed as nuisance alerts during port departures. MSC.246(83) does not require encrypted authentication of the SART signal, so spoofed transmissions are technically possible.

Regulatory basis

The framework is anchored in SOLAS III/6.2.2 (carriage of survival-craft locating devices), SOLAS IV/14 (performance standards for radio equipment), SOLAS IV/13 (maintenance) and SOLAS V/19 (parent AIS carriage requirement). The IMO performance standard for AIS-SART is MSC.246(83) of 2007, with the parallel radar SART standard at MSC.247(83), both layered on A.694(17) general requirements. The IEC testing standards are IEC 61097-14 (AIS-SART specific), IEC 61097-1 (parent generic AIS specification) and IEC 60945 (general). The AIS protocol layer is defined in ITU-R M.1371 with frequency allocations under the ITU Radio Regulations. The PSC framework operates under IMO Resolution A.1138(31) with deficiency code 04114.

Common errors

Treating the AIS-SART as a satellite distress alerter: the AIS-SART is a VHF on-scene locator with no satellite chain; the 406 MHz EPIRB is the satellite distress alerter. SOLAS requires both.
Using the AIS-SART instead of the radar SART: SOLAS III/6.2.2 accepts either, but they have different operational profiles. Many ships carry both for redundancy.
Misconfiguring the MMSI: the AIS-SART must use a 970-prefix SART category MMSI, not a regular ship MMSI. Misconfiguration breaks the AIS-receiver alarm logic.
Mounting the bracket beyond 1-minute accessibility: SOLAS requires the device to be transferable to the survival craft within approximately one minute; bracket placement must respect this.
Confusing the AIS-SART with the AIS-MOB: the AIS-MOB is a personal man-overboard beacon (972 prefix) and is not a SOLAS-mandated survival-craft device; the AIS-SART is the survival-craft device under III/6.2.2.
Allowing the 5-year service interval to lapse: the AIS-SART must be re-serviced or replaced at the 5-year mark; lapsed service is a PSC deficiency under code 04114.
Treating the annual self-test as optional: the annual AIS-SART self-test is mandatory under SOLAS IV/13 and must be recorded in the radio log.
Assuming the AIS-SART broadcasts to satellites by default: most AIS-SART transmissions reach satellite AIS payloads only opportunistically; the primary detection layer is shipborne AIS within VHF line-of-sight.
Disposing of an obsolete AIS-SART without deactivating the battery: like the EPIRB, retired AIS-SARTs in landfill can produce nuisance AIS alerts. Deactivate the battery or return the unit to the manufacturer.
Failing to test the actual model carried during STCW VI training: drills with a generic device leave the deck team unfamiliar with the controls of the actual model, increasing the risk of activation delay or error in a real emergency.

References

The principal source for SOLAS Chapter III Regulation 6.2.2 carriage of survival-craft locating devices and SOLAS Chapter IV Regulation 14 performance-standard regime is the IMO consolidated text of the International Convention for the Safety of Life at Sea, 1974, as amended, with III/6.2.2 setting the carriage scale, IV/13 supplying the maintenance regime, IV/14 the performance-standard requirement and IV/15 the radio-log record. The IMO performance-standard lineage is set out in two principal MSC 83 instruments adopted in October 2007: IMO Resolution MSC.246(83) for survival craft AIS Search and Rescue Transmitters and the parallel IMO Resolution MSC.247(83) for revised survival-craft radar transponders, layered on IMO Assembly Resolution A.694(17) of 1991. The international electrotechnical testing standards are IEC 61097-14 (AIS-SART specific), IEC 61097-1 (parent generic AIS specification) and IEC 60945 (general environmental and EMC envelope). The AIS protocol layer is defined in ITU-R Recommendation M.1371 with frequency allocations on AIS-1 at 161.975 MHz and AIS-2 at 162.025 MHz under the ITU Radio Regulations, and with operational reporting in ITU-R Report M.2285 on maritime survivor locating systems. The MMSI category-prefix scheme is governed by ITU-T Recommendation E.164, with 970 designating AIS-SART devices and 972 designating AIS-MOB personal beacons. Class-society type-approval is operated through the IACS member societies (DNV, Lloyd’s Register, ABS, Bureau Veritas, ClassNK, RINA, Korean Register, China Classification Society, Russian Maritime Register of Shipping and Indian Register of Shipping) for the principal manufacturers (Jotron, McMurdo, Kannad Marine, Ocean Signal, ACR Electronics, Furuno, JRC, Cobham SATCOM and Weatherdock). Port-State-control enforcement is operated through the Paris MoU and Tokyo MoU under IMO Resolution A.1138(31) Procedures for Port State Control 2019, with AIS-SART and radar SART deficiencies under code 04114. The GMDSS modernisation framework is supplied by the IMO MSC GMDSS Modernisation Plan adopted at MSC 98 in 2017 and the recognition of Iridium through IMO Resolution MSC.428(98) and parallel MSC.526(106) updates, with the 2024 review confirming MSC.246(83) and MSC.247(83) as operative through at least the end of the decade. The STCW training-and-certification framework is supplied by the STCW Convention Regulation VI/2 and the STCW Code Part A Section A-VI/2 syllabus on Proficiency in Survival Craft and Rescue Boats, supplemented by IMO Model Course 1.23. The SAR coordination framework is supplied by the IMO SAR Convention 1979 and the IAMSAR Manual jointly published by IMO and ICAO. The complementary 406 MHz satellite distress alerting framework is operated by the International Cospas-Sarsat Programme under the 1988 Programme Agreement, technically independent of the AIS-SART VHF chain but operationally complementary in the SOLAS dual-layer carriage regime.