Monitoring aircraft height-keeping performance consists of collection of necessary data using specialized systems, estimation of relevant performance parameters and comparison of these parameter estimates to corresponding RVSM requirements, on both an individual-aircraft and a system-wide basis.

Objectives of monitoring:

• To ensure that the height-keeping performance in RVSM airspace as a whole complies with system requirements, supporting continued safe use of the RVSM operations
• To ensure that individual operators and aircraft comply with applicable RVSM requirements, compliance which an operator must demonstrate in the course of obtaining State RVSM approval

As noted, the collection of necessary data is the first step in monitoring aircraft height-keeping performance. Aircraft geometric height is one of these data sources. There are two systems used to collect this type of information:

ADS-B Height Monitoring

United States: Aircraft equipped with qualified ADS-B out systems are height-monitored EACH DAY during normal operations in US ADS-B rule airspace at RVSM altitudes. Aircraft that are due for periodic monitoring or that must verify performance can fly any day to obtain a monitoring result. For assistance validating ADS-B, Request an ADS-B Performance Report (FAA.gov).

Canada: Aircraft equipped with qualified ADS-B out systems are height-monitored on MONDAYS (UTC) during normal operations in Canadian ADS-B rule airspace at RVSM altitudes. Aircraft that are due for periodic monitoring or that must verify performance can fly any Monday in Canadian airspace to obtain a monitoring result. For assistance validating ADS-B, Request an ADS-B Performance Report (NAVCanada.ca).

Operators who elect to utilize Part 91 Appendix G, section 9 to access RVSM airspace must verify their altitude-keeping performance. The current list of aircraft and their most recent successful monitoring date can be found at RVSM Approvals in the file labeled US IGA Operators with Domestic RVSM Authorization under Part 91 Section 9 (ADS-B).

Please allow 2-4 weeks for processing and posting of updated data.

US operators that are not listed, or do not have a current monitoring date in any of the monitoring result files, can request ADS-B results by providing flight details using the ADS-B Monitoring Request form on the NAARMO Points of Contact page.

GPS-based Monitoring Unit (GMU)

The GMU is a special-purpose data collection system carried aboard an aircraft for one flight, during which the unit collects Global Positioning System pseudo ranges. Post-flight processing of these data ensures estimates of aircraft geometric height which are of sufficient accuracy to permit estimation of relevant height-keeping performance parameters. In parallel, the current-generation FAA GMU also collects secondary surveillance radar Mode C data, which also contributes to parameter estimation.

The GMU has been in use since 1996 and has used by thousands of operators to satisfy monitoring requirements associated with the State RVSM approval process, thus supporting satisfaction of the second objective of monitoring noted above. However, the ensemble of monitoring results produced by application of the GMU has also been used to satisfy the first objective.

** A LOA or Operations Specifications must be obtained prior to conducting a monitoring flight.

More information on the GMU (PDF)

  AGHME | Aircraft Geometric Height Measurement Element: Systems Retired From Service  

The ground-based Aircraft Geometric Height Measurement Element (AGHME) monitoring systems have been decommissioned and are no longer available for use for height monitoring.

Monitoring is available via ADS-B Height Monitoring and GMU GPS-based Monitoring Unit - please see the relevant sections of this page in the headings above for more information.

For any questions or concerns, please contact NAARMO.