Detailed reference on ICAO Search and Rescue (SAR) — the organizational, procedural, and technical framework for aeronautical and joint aeronautical-maritime SAR under Annex 12 and the IAMSAR Manual (Doc 9731). This folder expands the summary in topics/sar.md into per-aspect files so each can be read independently.

Files in this folder#

• overview.md — what SAR is, where it sits in the ICAO framework, and how it relates to adjacent topics (GADSS, Annex 11 alerting service).
• components.md — the structural building blocks: SRR, RCC/RSC, SAR units, alerting posts, COSPAS-SARSAT, ELTs, and communications.
• blocks.md — the emergency phases (INCERFA/ALERFA/DETRESFA) as the operational escalation tiers; SAR operation stages; mermaid phase escalation diagram.
• threads.md — the six functional axes of SAR: organization/SRR, RCC operations, alerting and detection, cooperation and agreements, procedures and IAMSAR, and training.
• modules.md — anatomy of one SAR response: an overdue aircraft escalating from INCERFA through ALERFA to DETRESFA with RCC actions at each step.
• enablers.md — CNS infrastructure, COSPAS-SARSAT satellite segment, ELT standards, procedures, training, legal framework, and inter-agency coordination requirements.
• performance_objectives.md — KPA-keyed performance table and KPIs for SAR service provision.
• timeline.md — historical evolution: Annex 12 editions and amendments, IAMSAR Manual origins, COSPAS-SARSAT milestones, GADSS/LADR integration.
• references.md — consolidated ICAO and authoritative external references for all content in this folder.

Reading order#

Start with overview.md to understand the SAR framework and its place in ICAO. components.md maps the structural elements. blocks.md and threads.md explain the escalation model and functional axes. modules.md provides a concrete end-to-end worked example. enablers.md covers infrastructure dependencies. Use performance_objectives.md for KPA/KPI context and timeline.md for date anchoring. references.md is the consolidated citation list.

Source basis#

Content is grounded in:

• ICAO Annex 12 (Search and Rescue), 9th Edition (Amendment 19, 2024).
• ICAO Annex 11 (Air Traffic Services), Chapter 5 — Alerting Service.
• ICAO Doc 4444 (PANS-ATM), Chapter 9 — Alerting Service procedures.
• ICAO Annex 6, Parts I, II, III — ELT carriage requirements.
• ICAO Annex 10, Volume III — ELT technical specifications.
• ICAO Doc 9731 (IAMSAR Manual), Vols I–III — joint ICAO/IMO SAR guidance (not in local ICAO-Apr-26 library; referenced by Annex 12 normative Note at §283 of local md rendering).
• ICAO Doc 10165 (GADSS Manual) — LADR and OPS Control Directory guidance (not in local library).
• COSPAS-SARSAT system documentation (authoritative source — not in local library): https://www.cospas-sarsat.int/

What SAR is#

Search and Rescue (SAR) is the organized service for monitoring aircraft in distress, coordinating and communicating with those aircraft, locating their crash or ditching sites, and rescuing survivors. In the ICAO framework, SAR is mandated by Annex 12 to the Chicago Convention and is supplemented by joint ICAO/IMO guidance in the IAMSAR Manual (Doc 9731).

SAR is simultaneously an organizational framework (the network of SRRs and RCCs), a procedural framework (the three emergency phases and the SAR operation stages), and a technical framework (COSPAS-SARSAT satellite alerting, ELT specifications, communications requirements). These three dimensions must all be in place for effective SAR service.

SAR is deliberately non-discriminatory: Annex 12 §2.1.2 requires that States provide SAR assistance regardless of the nationality or status of persons in distress or the circumstances in which they are found.

Where SAR sits in the ICAO framework#

SAR is one of the Air Navigation Services established under the Chicago Convention. It is normatively separate from Air Traffic Services (ATS) defined in Annex 11, but deeply interlinked:

1. Alerting service (Annex 11 / Doc 4444) is the procedural bridge between ATC and SAR. ATS units monitor all flights they provide service to for the three emergency phase conditions and notify the RCC using the standard INCERFA/ALERFA/DETRESFA format. Without the alerting service, most SAR responses would not begin.

2. GADSS (Annex 6 / Doc 10165) provides RCCs with real-time aircraft position through the Location of an Aircraft in Distress Repository (LADR). Amendment 19 of Annex 12 makes LADR subscription mandatory for each RCC (§2.3.7). GADSS is the modern complement to COSPAS-SARSAT for large aircraft.

3. Annex 6 (Aircraft Operations) mandates ELT carriage on commercial aircraft (Parts I and II) and specifies that ELTs must meet Annex 10, Volume III specifications. The 406 MHz digital ELT is the primary SAR alerting device for general aviation and smaller aircraft.

4. Annex 10, Volume III contains the technical specifications for ELTs, including the COSPAS-SARSAT frequency bands (121.5 MHz for homing; 406 MHz for digital distress alerting with encoded identity and GPS position).

5. Doc 7030 (Regional Supplementary Procedures) provides regionally specific SAR procedures supplementing the global SARPs of Annex 12.

The SAR-ATS interface#

The alerting service is the most operationally critical interface. Annex 11 §5.1.2 assigns FICs and ACCs as the central collection point for emergency information within their FIR, forwarding to the RCC. The timing thresholds are normative: uncertainty phase if 30 minutes without contact; alert phase if subsequent inquiries yield no news; distress phase when there is probability that the aircraft is in distress. These thresholds from Annex 11 §5.2.1 are mirrored in Doc 4444 §9.2 as the PANS-ATM operating procedures.

The ATS unit does not conduct SAR — it triggers and supports. Once DETRESFA is declared, the RCC assumes operational coordination. The ATS unit continues to pass information and relay RCC actions to the flight if it remains communicable.

SAR and GADSS#

The GADSS autonomous distress tracking (ADT) requirement for large aeroplanes (Annex 6 Part I, Appendix 9) means that from 1 January 2021 new large aeroplanes must transmit aircraft position automatically during a distress condition, without crew action. These transmissions populate the LADR. Under Annex 12 Amendment 19, RCCs must subscribe to the LADR so that GADSS position data is available to inform search area calculation from the first moment of DETRESFA. This reduces the search area size and response time — the primary performance benefit of GADSS for SAR.

SAR as a global public good#

ICAO Annex 12 expresses SAR as a global cooperative obligation. No State can confine SAR strictly to its sovereign airspace: the high seas must be covered under regional air navigation agreements, and States must permit entry of foreign SAR units and accept assistance. The IAMSAR Manual operationalizes this cooperation by providing common procedures, search patterns, coordination signals, and planning tools that work regardless of whether the first responder is military, civil, or commercial, and whether the emergency is aeronautical or maritime.

References#

• Annex 12 (Search and Rescue), 9th Edition, Chapter 1 — Definitions of SAR terms.
• Annex 12, Chapter 2, §2.1.1 — Mandatory 24-hour SAR service obligation.
• Annex 12, Chapter 2, §2.3.7 — LADR subscription requirement for RCCs; GADSS Manual Doc 10165.
• Annex 11 (Air Traffic Services), Chapter 5, §5.1.2 — FIC/ACC as central emergency information collection point.
• Annex 11, Chapter 5, §5.2.1 — Triggers for each emergency phase.
• Doc 4444 (PANS-ATM), Chapter 9, §9.2 — Alerting service operating procedures.
• Doc 9731 (IAMSAR Manual), Vols I–III — Joint ICAO/IMO SAR guidance (authoritative source — not in local library).
• Doc 10165 (GADSS Manual) — LADR and OPS Control Directory guidance (authoritative source — not in local library).

Building blocks of the SAR system#

The SAR system under Annex 12 is composed of six classes of constituent elements. Each is normatively defined in Annex 12 Chapter 1 and governed by SARPs in Chapters 2 through 5.

1. Search and Rescue Regions (SRRs)#

A Search and Rescue Region (SRR) is an area of defined dimensions, associated with a Rescue Coordination Centre, within which SAR services are provided (Annex 12 §1). The key properties:

• SRRs must not overlap each other.
• Neighbouring SRRs must be contiguous — no gaps.
• SRRs should, as far as practicable, coincide with corresponding FIRs to align the ATC alerting boundary with the SAR boundary.
• On the high seas, SRR boundaries are determined by regional air navigation agreement, not national sovereignty.
• States may cooperate to establish a single SAR region encompassing more than one State's territory (Annex 12 §2.2.1, Note 1).

The global SRR structure is published in the relevant Air Navigation Plans and in the ICAO SAR Regional Plans for each ICAO region.

2. Rescue Coordination Centres (RCCs) and Rescue Subcentres (RSCs)#

The RCC is the operational hub of each SRR. Annex 12 mandates:

• One RCC per SRR (§2.3.1).
• 24-hour staffing by trained personnel (§2.3.3).
• Proficiency in the language used for radiotelephony communications in the region (§2.3.3); English proficiency recommended (§2.3.4).
• Subscription to the LADR (§2.3.7).
• Up-to-date contact details in the OPS Control Directory (§2.3.6).

A Rescue Subcentre (RSC) is subordinate to the RCC and is established where it would improve SAR efficiency — typically where a large SRR spans a State whose territory falls within another State's RCC jurisdiction (§2.3.2). The RSC mirrors the RCC communications requirements at its own scale.

A Joint Rescue Coordination Centre (JRCC) combines aeronautical and maritime SAR under a single authority — the preferred model where practical (§2.1.6).

3. Alerting Posts#

An alerting post is a facility intended to serve as an intermediary between a person reporting an emergency and the RCC (Annex 12 §1). They are established in areas where public telecommunications would not allow direct notification of the RCC (§2.3.5). Public or private services may be designated as alerting posts. The alerting post receives initial emergency information and relays it to the RCC.

4. SAR Units#

A SAR unit is a mobile resource composed of trained personnel with equipment suitable for expeditious SAR operations (Annex 12 §1). SAR units are designated from public or private services by the State (§2.5.1) and must:

• Know all parts of the SAR plan of operations relevant to their duties.
• Keep the RCC informed of their preparedness.
• Have rapid two-way communication capability during operations.

Elements that do not qualify as SAR units but can participate in SAR operations are designated separately under the plan of operations (§2.5.2). SAR aircraft are a subclass of SAR unit; they must be equipped to communicate on aeronautical distress frequencies, to home on distress frequencies, and — over maritime areas — to communicate with vessels (§2.6.3–2.6.5).

5. COSPAS-SARSAT System#

COSPAS-SARSAT is the international satellite-based distress alert and location system. It is a four-nation intergovernmental programme (Canada, France, Russia, USA) with a global network of ground stations and Mission Control Centres.

The system receives 406 MHz Emergency Locator Transmitter (ELT) signals via three satellite segments:

• LEOSAR (Low Earth Orbit) — Doppler-based location; global coverage with orbital delay.
• GEOSAR (Geostationary) — near-instant alert relay; no Doppler location in polar regions.
• MEOSAR (Medium Earth Orbit) — near-real-time alert relay with GPS-encoded position; provides near-instantaneous worldwide coverage with position accuracy to within 100 m when the beacon has an internal GNSS receiver.

The MEOSAR segment represents the current-generation capability, providing rapid (under 5 minutes) distress alerting with position data to the responsible Mission Control Centre, which forwards to the national SAR point of contact for relay to the RCC.

Annex 12 §3.2.5 (applicable as of 26 November 2026) requires each State to designate a 24-hour SAR point of contact for receipt and acknowledgement of COSPAS-SARSAT distress alert data, ensuring timely RCC notification.

6. Emergency Locator Transmitters (ELTs)#

ELTs are the aircraft-side component of the COSPAS-SARSAT alerting chain. Annex 12 cross-references to Annex 6 for carriage requirements and Annex 10 Vol III for technical specifications. Types defined in Annex 6 Part II:

• ELT(AF) — automatic fixed: permanently attached, auto-activated by impact.
• ELT(AP) — automatic portable: rigidly attached, auto-activated, removable.
• ELT(AD) — automatic deployable: auto-deployed and activated by impact or hydrostatic sensor; also manually deployable.
• ELT(S) — survival: removable from aircraft, manually activated by survivors.

The digital 406 MHz signal encodes the aircraft's 24-bit identifier (from ICAO registration) and, for GPS-equipped beacons, the position. The 121.5 MHz signal provides the homing frequency for on-scene SAR aircraft.

ELT frequency note: Until 25 November 2026, the ELT frequencies specified in Annex 10, Vol III are 121.5 MHz and 406 MHz. As of 26 November 2026, the specification is 121.5 MHz and 406.0 to 406.1 MHz, with the COSPAS-SARSAT 406 MHz channel assignment plan contained in Cospas-Sarsat Document C/S T.012.

7. SAR Communications Network#

Each RCC must maintain rapid, reliable two-way communications with (Annex 12 §2.4.1):

• Associated ATS units.
• Associated RSCs.
• Direction-finding and position-fixing stations.
• Coastal radio stations capable of alerting and communicating with surface vessels.
• SAR unit headquarters.
• All maritime RCCs in the region and adjacent aeronautical/maritime/ joint RCCs.
• A designated meteorological office or watch office.
• SAR units.
• Alerting posts.
• The COSPAS-SARSAT Mission Control Centre serving the SRR.

This ten-element communication fabric ensures the RCC can receive distress information from any source and coordinate response across all relevant services.

References#

• Annex 12, Chapter 1 — Definitions: SRR, RCC, RSC, SAR unit, alerting post.
• Annex 12, Chapter 2, §2.1.1.2 — Basic elements of SAR services.
• Annex 12, Chapter 2, §2.3.1 to §2.3.7 — RCC establishment, staffing, LADR.
• Annex 12, Chapter 2, §2.4.1 — RCC communications network requirements.
• Annex 12, Chapter 2, §2.5 — SAR unit designation.
• Annex 12, Chapter 2, §2.6 — SAR equipment; ELT references to Annex 6 and Annex 10 Vol III.
• Annex 12, Chapter 3, §3.2.5 (as of 26 November 2026) — 24-hour SAR point of contact for COSPAS-SARSAT.
• Annex 6, Part II, §2.4.12 — ELT carriage requirements for general aviation aeroplanes.
• Annex 10, Volume III — ELT technical specifications (authoritative source — not further expanded in this library).
• Doc 9731 (IAMSAR Manual), Vol II — Mission coordination procedures (authoritative source — not in local library).
• https://www.cospas-sarsat.int/ - COSPAS-SARSAT programme: MEOSAR status, MCC directory, C/S T.012 channel plan.

The escalation model#

SAR in the Annex 12 framework does not use the ASBU Block (B0/B1/B2/B3) vocabulary. The analogous structuring axes for SAR are:

• Emergency phases — the three normative states that govern the escalating level of RCC response, triggered by ATS units.
• SAR operation stages — the five internal workflow stages the RCC and SAR units progress through from first notification to conclusion, as described in the IAMSAR Manual.

These two axes are orthogonal: the emergency phase governs the threshold for action, while the operation stage governs what the RCC is doing at any moment during the response.

Emergency phases#

INCERFA — Uncertainty Phase#

Definition. A situation wherein uncertainty exists as to the safety of an aircraft and its occupants (Annex 12 Chapter 1).

Trigger (Annex 11 §5.2.1(a)).

• No communication received within 30 minutes of the time communication should have been received, or from the first unsuccessful attempt to establish contact — whichever is earlier; or
• Aircraft fails to arrive within 30 minutes of ETA last notified to or estimated by ATS.

RCC action. Upon INCERFA the RCC cooperates closely with ATS units and other relevant agencies to speedily evaluate incoming reports (Annex 12 §5.2.1). The RCC does not yet mobilize SAR units but gathers all available flight plan and position information.

Codeword. INCERFA. Formally defined in Doc 4444 as the codeword to designate an uncertainty phase.

ALERFA — Alert Phase#

Definition. A situation wherein apprehension exists as to the safety of an aircraft and its occupants (Annex 12 Chapter 1).

Trigger (Annex 11 §5.2.1(b)).

• Following INCERFA, subsequent contact attempts and inquiries have failed to reveal any news of the aircraft; or
• Aircraft cleared to land fails to land within 5 minutes of ETA and contact has not been re-established; or
• Information received indicates operating efficiency of the aircraft is impaired, but not to the extent that forced landing is likely; or
• Aircraft known or believed to be subject to unlawful interference.

RCC action. Immediately alert SAR units and initiate any necessary action (Annex 12 §5.2.2). The RCC begins active preparation.

Codeword. ALERFA. Formally defined in Doc 4444 as the codeword to designate an alert phase.

DETRESFA — Distress Phase#

Definition. A situation wherein there is a reasonable certainty that an aircraft and its occupants are threatened by grave and imminent danger and require immediate assistance (Annex 12 Chapter 1).

Trigger (Annex 11 §5.2.1(c)).

• Following ALERFA, further unsuccessful inquiries point to probability that the aircraft is in distress; or
• Fuel on board exhausted or insufficient to reach safety; or
• Operating efficiency impaired to the extent that forced landing is likely; or
• Aircraft is about to make or has made a forced landing.

RCC action (Annex 12 §5.2.3 — ten required steps). a) Immediately initiate SAR units under the plan of operations. b) Determine aircraft position, uncertainty radius, and search area. c) Notify and keep informed the operator. d) Notify other RCCs whose help may be needed. e) Notify the associated ATS unit if info came from another source. f) Request all available aircraft/vessels to monitor distress frequencies (121.5 MHz and 406 MHz ELT homing). g) Draw up a detailed plan of action; communicate to directing authorities. h) Amend the plan as circumstances evolve. i) Notify the appropriate accident investigation authorities. j) Notify the State of Registry of the aircraft.

Codeword. DETRESFA. Formally defined in Doc 4444 as the codeword to designate a distress phase.

SAR operation stages (IAMSAR model)#

The IAMSAR Manual (Doc 9731, Vol I and II) describes SAR operations as progressing through five stages. These stages drive internal RCC workflow regardless of which emergency phase has been declared.

Phase-stage interaction#

Emergency phases and operation stages run concurrently. During INCERFA the RCC is in Awareness/Initial Action stages. ALERFA transitions into active Planning. DETRESFA activates the Operations stage. Conclusion is independent of phase — it is reached when the operation ends regardless of the phase at which operations were fully mobilized.

Multi-region coordination#

When the aircraft's position is unknown and may fall within two or more SRRs, Annex 12 §5.2.4 prescribes the rule for designating a coordinating RCC:

• Default: the RCC responsible for the region of the aircraft's last reported position.
• If last position was on the boundary: the RCC for the region towards which the aircraft was proceeding.
• If aircraft had no radio: the RCC for the destination region.
• If COSPAS-SARSAT identifies the distress site: the RCC for that region.

All involved RCCs share information; the coordinating RCC has overall responsibility and notifies all others of developments.

References#

• Annex 12, Chapter 1 — Definitions: alert phase, distress phase, emergency phase, uncertainty phase.
• Annex 12, Chapter 5, §5.2.1 to §5.2.4 — RCC procedures for each phase; multi-region coordination.
• Annex 11, Chapter 5, §5.2.1 — ATS phase triggers and timing thresholds.
• Doc 4444 (PANS-ATM), Chapter 1 — Definitions: INCERFA, ALERFA, DETRESFA.
• Doc 4444, Chapter 9, §9.2 — Alerting service operating procedures including 30-minute rule.
• Doc 9731 (IAMSAR Manual), Vol I and II — SAR operation stages and mission coordination (authoritative source — not in local library).