When any failure to the GNSS occurs, it is to be expected that some aircraft will fail to meet the RNP and require special action to be taken, while others will be able to continue to meet the RNP. It is important that controllers and pilots are made aware of any degradation in a timely manner.
IFATCA Policy is:
A monitoring and interpretation service should be established to monitor the status of all elements of the GNSS and interpret this information in a manner that provides relevant information to pilots and ATC. The information disseminated from the monitoring service or displayed at controller positions must be expressed in operational terms.
ATC procedures must be established for the use of GNSS and must cover the failure or degradation of the system. When ATC is informed of a change in the status of t he GNSS by the monitoring service or by display equipment, specific procedures associated with that change must be implemented. Should it not be possible to achieve the RNP in airspace, an alternative RNP should be declared.
|See: WP 86 – Tunis 1996
See also: WP 93 – Santiago 1999
Last Update: September 29, 2020