Guidance concerning Air Navigation in and above the NAT MNPSA
before transmitting the position report to ATC, verify the waypoint co-ordinates against the Master Document and those in the steering navigation system. When feasible the position report “next” and “next plus 1” waypoint co-ordinates should be read from the CDU of the navigation system coupled to the autopilot.
Even if automatic waypoint position reporting via data link (e.g. ADS-C, CPDLC or FMC
WPR) is being used to provide position reports to ATC the above checks should still be performed.
The crew should be prepared for possible ATC follow-up to the position report.
Crews should also be aware that trials are underway in the NAT Region of ADS-C
conformance monitoring. ATC may establish event contracts that will result in automatic alerts whenever the aircraft diverges from its cleared profile. Unless previously advised by the pilot of the need for such a divergence, crews should expect ATC to query the situation. Standardised CPDLC alert messages have been developed for use here.
It is important to remember that there are a number of ways in which the autopilot may
unobtrusively become disconnected from the steering mode. engagement with the navigation system should be made.
Therefore, regular checks of correct
It is recommended that where possible the navigation system coupled to the autopilot should
display the present position co-ordinates throughout the flight. If these are then plotted as suggested above, they will provide confirmation that the aircraft is tracking in accordance with its ATC clearance. Distance to go information should be available on the instrument panel, whilst a waypoint alert light, where fitted, provides a reminder of the aircraft’s imminent arrival over the next waypoint.
A position check should be made at each waypoint and the present position plotted 10
approximately 2 degrees of longitude beyond plot a present position 2 degrees of longitude (e.g. when, due to equipment failure, only one
a generally east-west flight, this 10 minute point will be the oceanic waypoint. It may therefore in fact be simpler to after each 10 degree waypoint. There may be circumstances, LRNS remains serviceable) in which additional plots midway
between each waypoint may be justified.
It is good practice to cross check winds midway between oceanic waypoints by comparing
the flight plan, LRNS and upper millibar wind charts data. Such a cross check will also aid crews in case
there is a subsequent need for a contingency requiring the use of Dead Reckoning.
The navigation system not being used to steer the aircraft should display cross-track distance
and track angle error. Both of these should be monitored, with cross-track distance being displayed on the
HSI where feasible.
When the aircraft is within range of land based navaids, and the crew is confident that these
navaids are providing reliable navigation information, consideration should be given to updating the LRNSs. Automatic updating of the LRNSs from other navaids should be closely monitored, and before entry into
airspace where different navigation requirements have been specified (e.g. RNP5
airspace), crews should use all aids (including system is operating to the required accuracy. appropriate ATC unit should be informed.
VORs and DMEs) to confirm that If there is any doubt regarding
in European BRNAV the in-use navigation system accuracy, the
NAT Doc 007