Strumble HMU is no longer be available for use from 1st November 2023.

Welcome to the North Atlantic Central Monitoring Agency (NAT CMA)

The NAT CMA was established in 1985 by the ICAO North Atlantic System Planning Group (NATSPG) to support the preparation and introduction of RVSM in the North Atlantic (NAT) Region, and thereafter to provide data-based assurance of continuing system safety and integrity. It has been operated by the United Kingdom on behalf of NATSPG since inception, being based in London until 2004 and subsequently in Prestwick, Scotland.

The CMA is one of thirteen Regional Monitoring Agencies (RMAs) around the world which serve their ICAO Planning and Implementation Regional Groups, their associated States, ANSPs and aircraft operators. Currently the CMA maintains State Registration and Operational Approval records for aircraft registered in five designated States (Norway, Iceland, Ireland, Portugal and Bermuda), Operational Approvals granted by other States for aircraft registered in these five States, and assists those States in overseeing operator compliance with height monitoring targets in accordance with ICAO Annex 6 (Operation of Aircraft) requirements. It supports the RMA community by maintaining a combined database of aircraft registration, operators and RVSM Approvals incorporating regular revisions of data from other RMAs into a common system.

To monitor compliance with the RVSM Minimum Navigation Performance Specification (RVSM MASPS) the CMA processes and reviews aircraft height keeping performance to determine altimetry system error (ASE) and issues height monitoring results to operators. To do this the CMA uses recorded data from the Height Monitoring Unit (HMU) at Strumble (Wales) on the basis of individual operator requests but also utilises the data continuously recorded of aircraft passing the HMU site within RVSM levels.

The CMA also receives, reviews and records operational safety occurrence reports from ANSPs and aircraft operators across the North Atlantic Region, in support of regional safety groups and other stakeholders. The resultant records provide data to support regional risk assessment – technical and operational risk analysis and performance measured against established Target Levels of Safety, and trend data to support the work of the ICAO safety groups. This data also supports the safe evolution of separation standards, navigational requirements and procedures.