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provided that the magnetic course (track) is available on the flight log, a check against the magnetic
heading being flown, plus or minus drift, is likely to indicate any gross tracking error.
Always remember that something absurd may have happened in the last half-hour. There are
often ways in which an overall awareness of directional progress can be maintained; the position of
the sun or stars; disposition of contrails; islands or coast-lines which can be seen directly or by
using radar; radio navaids, and so forth. This is obvious and basic, but some of the errors which
have occurred could have been prevented if the crew had shown more of this type of awareness.
If the crew suspects that equipment failure may be leading to divergence from cleared track, it is
better to advise ATC sooner rather than later.
In conclusion, navigation equipment installations vary greatly between operators; but lessons
learned from past mistakes may help to prevent mistakes of a similar nature occurring to others in
the future.
NORTH ATLANTIC MNPSA OPERATIONS MANUAL CHAPTER 14
NAT MNPS 73 Edition 2005
Chapter 14: The Prevention of Deviations From Track as a Result of
Waypoint Insertion Errors
14.1 THE PROBLEM
14.1.1 During the monitoring of navigation performance in the NAT MNPS Airspace, a number of
GNEs are reported. There were 10 in 2003 and 15 in 2004. Such errors are normally detected by means of
long range radars as aircraft leave oceanic airspace. In addition, however, on 71 occasions in 2003 and 118
occasions in 2004, 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. Of the 118 such instances in 2004, 81 were attributable to crew errors and 16 resulted from a
communications misunderstanding between controller and pilot.
14.1.2 Investigations into the causes of all recent deviations show that about 75% 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.
14.2 THE CURE
14.2.1 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.
14.2.2 The following procedures are recommended as being a good basis for MNPS operating
drills/checks:
• 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.
• 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.
• 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.
• Plot your Present Position regularly on your chart.
NORTH ATLANTIC MNPSA OPERATIONS MANUAL CHAPTER 14
NAT MNPS 74 Edition 2005
– 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 preferably
plotted approximately 10 minutes after passing each waypoint, and, if circumstances
dictate, midway between waypoints. e.g. if one system has failed.
• Check the present, next and next+1 waypoint co-ordinates as shown on the Master Document against
those in the steering CDU before transmitting position reports (in performing these checks review
the LRNS stored co-ordinates in expanded Lat/Long format (not abbreviated ARINC 424 format).
• Check the LRNS indicated magnetic heading and distance to the next waypoint against those listed
on the Master Document.
14.2.3 The procedures outlined in this Section will detect any incipient gross errors, providing that
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