Emerging Regional ADS-C Requirements over Oceanic Airspace

Oceanic surveillance has evolved dramatically—Automatic Dependent Surveillance–Contract (ADS-C) is now enabling aircraft to operate with 30 NM separation, boosting airspace capacity by over 300% and delivering $3 billion+ in global efficiency gains. With automatic position reporting, business jet operators can expect improved routing, fuel savings, and reduced workload in high-traffic oceanic corridors.

What is Automatic Dependent Surveillance–Contract (ADS-C)?

Automatic Dependent Surveillance–Contract (ADS-C) is a surveillance technology that enables automatic position reporting from an aircraft to air traffic control (ATC) over a datalink. It operates on a contractual basis, meaning the aircraft and the ground system agree in advance on what data will be sent and under what conditions. ADS-C is primarily used in oceanic and remote airspace where radar coverage is unavailable.

 

Instead of continuous radar monitoring, ATC maintains surveillance by receiving periodic or event-triggered position reports from the aircraft. These reports include position, altitude, speed, and sometimes future trajectory data, depending on the contract setup. ADS-C is a core component of FANS 1/A (Future Air Navigation System) operations and is closely integrated with CPDLC (Controller–Pilot Data Link Communications) for non-radar controlled airspace.

Why is Automatic Dependent Surveillance–Contract (ADS-C) Important?

ADS-C is critical for several reasons:

 

• Enables surveillance in non-radar environments: Oceanic, polar, and certain remote continental areas lack radar coverage. ADS-C allows ATC to maintain awareness of aircraft positions across these regions.
• Supports reduced separation minima: With accurate and timely reporting, ATC can apply reduced lateral and longitudinal separation standards (e.g., 50 NM lateral, 5-minute longitudinal), enabling more efficient routing and fuel savings.
• Enhances safety and predictability: Automatic updates reduce reliance on manual position reporting over HF voice, minimizing communication errors and delays.
• Integral to Performance-Based Communication and Surveillance (PBCS): ADS-C compliance with Required Surveillance Performance (RSP) specifications is essential for operating in the most efficient airspace corridors, such as in the North Atlantic and Pacific regions.

The table below highlights key aviation datalink types, with emphasis on ADS-C and its automated position reporting:

 

Data Link Type	Use/Purpose	Mechanism	Crew Action
ADS‑C	Automatic position/intent reporting to ATC	On-demand, periodic or event-driven contract over datalink (HF/SATCOM)	No pilot message needed; FMS auto-sends reports per contract
CPDLC	Exchange of ATC clearances, requests, etc.	Two-way text messages between cockpit and ATC	Pilots initiate/respond to messages; logon required
ADS‑B	Surveillance broadcast (aircraft ID, position)	Continuous 1090 MHz data broadcast to any receiver	Automatic (no pilot action); supports ground/air situational awareness
Voice (HF/VHF)	Traditional voice comms for ATC	VHF/HF radio (backup to datalink)	Pilot transmits/receives on radio; manual position reports if ADS‑C unavailable

Key Components of Automatic Dependent Surveillance–Contract (ADS-C)

ADS-C consists of the following major components:

Aircraft Surveillance System (FMS and Transmitting Unit)

• The Flight Management System (FMS) collects position, velocity, intent (next waypoint), and other data.
• This information is sent through the aircraft’s communication unit (usually SATCOM or HF datalink).

Datalink Communication Channel (HF or SATCOM)

• ADS-C messages are transmitted over long-range communication networks such as Inmarsat (J5) or Iridium (J7).
• Ensures connectivity in areas beyond VHF range.

Ground Automation System (ATC Backend)

• Receives, processes, and displays the incoming ADS-C messages.
• Sets up and maintains contracts with the aircraft (e.g., periodic reports every 15 minutes, event-based reports on altitude change).

Types of ADS-C Contracts

• Periodic Contract: Reports sent at set intervals (e.g., every 5, 10, or 15 minutes).
• Event Contract: Triggers when specific events occur (e.g., altitude or route changes).
• Demand Contract: Sent upon controller request.
• Emergency Contract (optional): Automatically sent in declared emergencies, depending on system setup.

ADS-C Reports

• Each report includes aircraft position (latitude, longitude), time, flight level, speed, next waypoint, and estimated time over the waypoint.
• This data is vital for controllers to ensure aircraft separation and conformance to clearances.

Regional Datalink Mandates

ADS‑C/CPDLC equipage requirements differ by region. Below are the key regulatory implementations in major oceanic regions:

North Atlantic (NAT) Region

In the North Atlantic (NAT) high‑altitude airspace, global mandates have been phased in over recent years. Starting in 2013, FANS 1/A was required on core Organized Track System (OTS) routes. By Phase 2B (December 2017), it applied to all North Atlantic Organised Track System (NAT-OTS) tracks between FL350–FL390.

 

By Phase 2C (January 2020), the mandate extended to all NAT airspace at FL290 and above. Today, virtually all aircraft operating between FL290–FL410 in NAT High-Level Airspace must be ADS‑C/CPDLC equipped, with very limited exceptions (e.g., for specific SAR or medical flights).

Additionally, NAT airspace adopted Performance-Based Communications/Surveillance (PBCS) standards:

• RCP 240 is required for CPDLC
• RSP 180 is required for ADS‑C

As the FAA states, “CPDLC compliant with RCP 240 is required to fly the most efficient routes in the NAT.”

In practice, NAT-compliant flight plans must:

• Include ADS‑C and CPDLC codes (e.g., “R”, “J5” or “J7”)
• Use “SUR/RSP180” notation for PBCS compliance

Regulatory documents such as NAT Doc 007, ICAO Annexes 10 & 11, PANS-ATM (Doc 4444), and NAT Ops Bulletins define the operational framework. All procedures are aligned with the ICAO GOLD Manual.

Pacific & Asia–Pacific Region

In the Pacific/Asia–Pacific region, there is no unified oceanic-wide ADS‑C mandate, but FANS 1/A equipage is strongly recommended, particularly on long-haul and transoceanic routes.

Many FIRs in this region promote ADS‑C use for separation in remote (Category R) airspace. ICAO’s Asia/Pacific Seamless ATM Plan explicitly recommends ADS‑C and CPDLC for supporting Performance-Based Navigation (PBN) separation in remote areas.

Notable operational details include:

• In U.S. Pacific Ocean airspace (KZAK Oakland FIR) and Anchorage FIR, ADS‑C/CPDLC use is only permitted with approved SATCOM networks:
  • J5 (Inmarsat)
  • J7 (Iridium)

The FAA Pacific AIP states:

“The use of CPDLC and ADS‑C in [Oakland FIR] is only permitted by Inmarsat and Iridium customers. All other forms of data link connectivity are not authorized… If J5 or J7 is not included… the LOGON will be rejected.”

• The same SATCOM coding requirement applies in New York Oceanic (Greenland) airspace.

Operators must ensure correct equipment codes are filed in the flight plan to enable logon and datalink clearance delivery.

Indian Ocean & Southern Pacific Corridors

In regions such as the Indian Ocean and Southern Pacific, ADS‑C is commonly used on preferred airways, though no blanket mandate exists. Operators flying routes like:

• Middle East ↔ Australia
• Asia ↔ Africa

often operate under RNP-10 navigation with ADS‑C contracts via HF or SATCOM, enabling 50 NM lateral separation.

Asia-Pacific States, through Asia/Pacific Air Navigation Planning and Implementation Regional Work Group (APANPIRG) guidance, define appropriate flight plan entries and recommend FANS 1/A equipment for operational efficiency.

In all cases, operators are advised to check:

• Relevant AIPs
• Regional NOTAMs
• ICAO documentation

 

to verify ADS‑C and CPDLC requirements for each Oceanic FIR they plan to traverse.

Regulatory References

The procedures and requirements for oceanic ADS‑C operations are spelled out in ICAO and national publications:

 

Document/Standard	Content Summary
ICAO Doc 10037 – Global Operational Data Link (GOLD)	Global guidelines for FANS 1/A procedures (flight planning, equipment codes, logon, message formats). Chapters include ADS‑C contract types, CPDLC uplink/downlink, normal/contingency cases.
ICAO Annex 10 (Vol IV), Annex 11 and PANS-ATM (Doc 4444)	SARPs for communication and surveillance, including ADS‑C/CPDLC usage and phraseology (Annex 10) and separation minima (Annex 11/Doc 4444).
NAT Ops Bulletin 2017-004 (Rev.2) – FANS 1/A SEI (Jun 2022)	North Atlantic guidance for operators on CPDLC/ADS‑C. Affirms that FANS datalink (CPDLC and ADS‑C) is used in NAT, and advises to follow GOLD (Doc 10037) flight crew procedures. Includes special emphasis items for NAT region FANS ops.
FAA Advisory Circular 91-70 (recent version)	U.S. guidance for oceanic/remote ops. Note that RCP240/RSP180 equipment is required for optimal NAT tracks, defines ADS‑C contracts, and gives crew procedures (e.g. logon 10–25 min prior).

Flight Operation Example – Pacific Route (Pilatus PC‑24 over Oakland FIR)

Let’s consider a Pilatus PC‑24 operating a business flight from Honolulu (PHNL) to San Francisco (KSFO) via the Oakland Oceanic FIR (KZAK). This route involves extended segments of non-radar Pacific airspace, where FANS 1/A+ compliance—including ADS‑C and CPDLC capability—is required for optimal routing and ATC separation.

Before Departure:

Dispatch and flight planning teams must ensure the aircraft’s equipment codes are properly filed. For this airspace, the flight plan must include:

 

• “R” in Item 10a (for RNP-10/ADS‑C capability)
• “J5” or “J7” in Item 10a (for Inmarsat or Iridium SATCOM)
• Appropriate PBN and SUR entries in Item 18 (e.g., SUR/RSP180)

 

Failure to include J5/J7 results in rejected logon attempts in the Oakland FIR.

Pre-Oceanic Entry (In-Flight):

Approximately 20 minutes before the boundary entry into Oakland Oceanic, the crew reviews data link readiness. According to FAA Pacific guidance, logon to ADS-C/CPDLC should occur 10–25 minutes before FIR entry, unless otherwise instructed.

 

Using the aircraft’s FMS or communications control display, the crew initiates logon to Oakland Oceanic (KZAK). The connection is established via SATCOM (J5 or J7 path), verified by successful acknowledgment from the ground ATC system.

Contract Establishment:

Once connected, the Oakland controller initiates an ADS‑C periodic contract, typically requesting position reports at 15-minute intervals. In addition, an event contract is issued to trigger reports on:

 

• Reaching a new waypoint
• Climbing/descending through a flight level
• Deviation from the cleared route

 

The PC-24 automatically begins transmitting ADS‑C position reports as per the contract, relieving the crew from manual HF position reporting duties.

Active ADS‑C Phase:

While in Pacific non-radar airspace, the PC‑24 transmits:

 

• Automatic periodic reports
• Event-driven updates

 

If a clearance revision is needed (e.g., change of route or level due to turbulence), ATC can uplink it via CPDLC. The message appears on the cockpit display and, once reviewed, is acknowledged digitally by the crew. This process improves clarity and reduces voice channel congestion.

Contingencies:

Should the ADS‑C link be lost temporarily (e.g., satellite shadow or equipment issue), the crew follows the contingency procedure as outlined in the regional AIP:

 

• Switch to HF voice reporting if required
• Notify ATC via CPDLC or HF of link status

 

If an abnormal situation occurs—such as a medical diversion—the crew can issue an emergency ADS-C message, depending on system capability, or send a CPDLC “PAN PAN” or “EMERGENCY” status message to ATC.

Post-Oceanic Exit:

Upon re-entering radar-controlled airspace near the U.S. mainland, the ADS‑C contract is terminated either automatically or by controller command. The aircraft resumes standard VHF comms, and data link usage transitions back to an optional/redundant role.

Operational Benefits:

For business jets like the Pilatus PC‑24, using ADS‑C/CPDLC:

 

• Eliminates the need for routine HF voice calls
• Reduces crew workload during long oceanic segments
• Improves clarity and auditability of ATC instructions
• Allows full compliance with RNP-10 and PBCS separation

 

The end result is a smoother and safer transoceanic experience, critical for high-performance business operations across long Pacific routes.

FAQs

1. When exactly should our crew initiate the ADS-C/CPDLC logon before entering oceanic airspace?

Crews should initiate the logon 10 to 25 minutes prior to entering oceanic airspace, unless a specific FIR requires otherwise. Early logon ensures the contract is active before entering non-radar zones and avoids delays in surveillance or CPDLC communications setup.

2. What happens if ADS-C or CPDLC fails mid-flight over oceanic airspace?

If either link fails, crews must revert to voice procedures using HF or SATCOM as published in the applicable AIP or contingency procedures. The controller should be notified via alternate means. Oceanic clearance conformance must still be maintained unless otherwise instructed.

3. Are aircraft flying below FL290 required to have ADS-C in oceanic airspace?

No, ADS-C and CPDLC mandates typically apply at and above FL290, particularly in NAT and Pacific high-level airspace. However, some FIRs may recommend datalink use below FL290 depending on airspace classification and traffic density.

4. Does ADS-C transmit weather or turbulence reports automatically?

No. ADS-C only transmits position, altitude, velocity, and intent data per contract settings. Weather or turbulence must be reported manually via CPDLC free text, voice, or using other automated systems if equipped (e.g., AIREP or meteorological uplinks).

 

At Just Aviation, we support business flight operators with expert compliance solutions for evolving global navigation mandates. We understand that why flight & planning route planning is more crucial lies at the heart of safe and efficient operations. From route planning to ADS-C readiness, our team ensures smooth, safe, and regulation-aligned operations in every oceanic region. Trust Just Aviation to keep your fleet connected and compliant—wherever your missions take you.