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Guidance concerning Air Navigation in and above the NAT MNPSA

CHAPTER 15

CHAPTER 15: THE PREVENTION OF DEVIATIONS FROM TRACK AS A RESULT OF WAYPOINT INSERTION ERRORS

    • 15.1

      THE PROBLEM

      • 15.1.1

        During the monitoring of navigation performance in the NAT MNPS Airspace, a number of

GNEs are reported. There were 20 in 2007 and 25 in 2008. Such errors are normally detected by means of long range radars as aircraft leave oceanic airspace but are increasingly confirmed by means of ADS-C waypoint reporting. In addition, however, on 143 occasions in 2007 and 148 occasions in 2008, potential navigation errors were identified by ATC from routine aircraft position reports (from “next” or “next plus one” waypoints) and ATC were able to intervene to prevent incorrect routing by the aircraft. The vast majority of these instances were attributable to crew errors.

15.1.2

Investigations into the causes of all recent deviations show that about 25% are attributable to

equipment control errors by crews and that almost all of these errors are the result of programming the navigation system(s) with incorrect waypoint data – otherwise known as waypoint insertion errors. The remainder comprise mainly the following of the filed flight plan route rather than the cleared route (the

primary cause of some 80% of the ATC Interventions described in 14.1.1 above).

    • 15.2

      THE CURE

      • 15.2.1

        Waypoint insertion errors can be virtually eliminated if all operators/crews adhere at all

times to approved operating procedures and cross checking drills. This Manual provides a considerable amount of guidance and advice based on experience gained the hard way, but it is quite impossible to provide specific advice for each of the many variations of navigation systems fit.

15.2.2 drills/checks:

The following procedures are recommended as being a good basis for MNPS operating

  • a)

    Record the initialisation position programmed into the navigation computer. This serves two purposes:

    • it establishes the starting point for the navigation computations; and

    • in the event of navigation difficulties it facilitates a diagnosis of the problem.

  • b)

    Ensure that your flight log has adequate space for the ATC cleared track co-ordinates, and always record them. This part of the flight log then becomes the flight deck Master Document for:

    • read back of clearance;

    • entering the route into the navigation system;

    • plotting the route on your chart.

  • c)

    Plot the cleared route on a chart with a scale suitable for the purpose (e.g. Aerad, Jeppesen, NOAA en route charts). This allows for a visual check on the reasonableness of the route profile and on its relationship to the OTS, other aircraft tracks/positions, diversion airfields, etc.

  • d)

    Plot your Present Position regularly on your chart.

    • this may seem old-fashioned but, since the present position output cannot normally be interfered with and its calculation is independent of the waypoint data, it is the one output which can be relied upon to detect gross tracking errors. A position should be checked and

NAT Doc 007

89

Edition 2010

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