Guidance concerning Air Navigation in and above the NAT MNPSA
prepare a proposal to ATC with respect to the prevailing clearance above or below MNPS Airspace, turn-back, obtain the special routes, etc.);
circumstances (e.g. request clearance to fly along one of
advise and consult with ATC as to the most suitable action;
obtain appropriate re-clearance prior to any deviation from the last acknowledged Oceanic
When the flight continues in accordance with its original clearance (especially if the distance
ahead within MNPS Airspace is significant), the pilot should begin a careful monitoring programme:
to take special care in the operation of the remaining system bearing in mind that routine methods of error checking are no longer available;
to check the main and standby compass systems frequently against the information which is still available;
to check the performance record of the remaining equipment and if doubt arises regarding its performance and/or reliability, the following procedures should be considered:
attempting visual sighting of other aircraft or their contrails, which may provide a track indication;
calling the appropriate OAC for information on other aircraft adjacent to the aircraft’s estimated position and/or calling on VHF to establish contact with such aircraft (preferably same track/level) to obtain from them information which could be useful. e.g. drift, groundspeed, wind details.
The Remaining System Fails After Entering MNPS Airspace
The pilot should: immediately notify ATC;
make best use of procedures specified above relating to attempting visual sightings and establishing contact on VHF with adjacent aircraft for useful information;
keep a special look-out for possible conflicting aircraft, and make maximum use of exterior lights;
if no instructions are received from ATC within a reasonable period consider climbing or descending 500 feet, broadcasting action on 121.5 MHz and advising ATC as soon as possible.
this procedure also applies when a single remaining system gives an indication of
degradation of performance, or neither system fails completely but the system indications diverge
widely and the defective system cannot be determined.
Complete Failure of Navigation Systems Computers
A characteristic of the navigation computer system is that the computer element might fail,
and thus deprive the aircraft of steering guidance and the indication of position relative to cleared track, but
the basic outputs of the IRS (LAT/LONG, Drift and Groundspeed) are minimise the effects of a total navigation computer system failure comprehensive use of the plotting chart.
left unimpaired. A typical drill to
use the basic IRS/GPS outputs to adjust heading to maintain mean track and to calculate ETAs.
draw the cleared route on a chart and extract mean true tracks between waypoints.
NAT Doc 007