**** IMPORTANT NOTICE ****
STRUMBLE HMU is no longer available for use. North Atlantic Height monitoring takes place every Monday in Shanwick airspace for suitably equipped aircraft using space-based ADS-B.
The NAT AHMS collates all ADS-B data within Shanwick airspace (FL290-410 inclusive) every Monday. This data is then combined with a geographic model and MET data using our ASE processing software to produce height monitoring results. The system requires no extra procedures from Operators if the flight is using ADS-B within Shanwick on Mondays.
Due to the flexibility of AHMS systems, the NAT CMA is working with all NAT ANSPs to increase the coverage and frequency of monitoring. Please check back to the NAT CMA website to see the latest coverage area.
(Insert map of Shanwick)
Operators do not need to divert from an optimum route in order to fly over a physical location. All ADS-B flights within Shanwick will be monitored. Any flights for the specific purpose of height monitoring should be flight planned for Mondays.
In Flight Procedures.
The NAT AHMS continually monitors aircraft through the entirety of the flight within the stated coverage area. To achieve a successful result, the aircraft must fly in level flight for a minimum of 5 minutes. It is possible to achieve multiple positive results per 5 minute period in a single flight. This means crews should follow ATC instruction as normal. If a request for a level between FL290 and FL410 has been made, crews should include in the request to ATC “…for height monitoring flight.”
The NAT AHMS is capable of tracking all flights simultaneously. To that end, provided the above procedures are followed and aircraft are properly equipped and the flight takes place during and within the stated availability, aircraft height will be monitored automatically.
Post Flight Procedures.
Operators wishing to ascertain the result of the overflight should complete and submit the Height Monitoring Request form.