World Air Ops | NAT | Doc 007 MNPS Guidance

Guidance concerning Air Navigation in and above the NAT MNPSA CHAPTER 14Rare Causes Of Lateral Navigation Errors14.3.2 To illustrate the surprising nature of things which can go wrong, the following are examplesof some extremely rare faults which have occurred:a) the lat/long co-ordinates displayed near the gate position at one international airport werewrong.b) because of a defective component in one of the INS systems on an aircraft, although the correctforward waypoint latitude was inserted by the crew (51°) it subsequently jumped by one degree(to 52°).c) the aircraft was equipped with an advanced system with all the co-ordinates of the waypoints ofthe intended route already in a database; the crew assumed that these co-ordinates were correct,but one was not.d) when crossing longitude 40°W westbound the Captain asked what co-ordinates he should insertfor the 50°W waypoint and was told 48 50. He wrongly assumed this to mean 48°50'N at50°00W (when it really meant 48°N 50°W ) and as a result deviated 50 NM from track.e) the flight crew had available to them the correct co-ordinates for their cleared track, butunfortunately the data which they inserted into the navigation computer was from the companyflight plan, in which an error had been made.f) at least twice since 1989, longitude has been inserted with an error of magnitude of times 10.e.g. 100°W instead of 10°W, or 5°W instead of 50°W. Because of low angles of bank, theaircraft departed from track without the crews being aware, and both lateral and longitudinalseparations with other aircraft were compromised.g) a crew based at and usually operating from London Heathrow was positioned at LondonGatwick for a particular flight. One pilot inadvertently loaded the Heathrow co-ordinates intothe INS, instead of those for Gatwick. This initialisation error was only discovered when theaircraft had turned back within the NAT after experiencing a GNE.h) the pilot of a flight departing from the Caribbean area input the wrong departure airfield coordinatesprior to departure. This error was discovered when deviation from cleared routeseriously eroded separation with two other opposite direction aircraft.14.4 LESSONS TO BE LEARNED‣ Never relax or be casual in respect of cross-check procedures. This is especially importanttowards the end of a long night flight.‣ Avoid casual R/T procedures. A number of GNEs have been the result of a misunderstandingbetween pilot and controller as to the cleared route and/or flight level. Adhere strictly to properR/T phraseology and do not be tempted to clip or abbreviate details of waypoint co-ordinates.‣ Make an independent check on the gate position. Do not assume that the gate co-ordinatesare correct without cross-checking with an authoritative source. Normally one expects coordinatesto be to the nearest tenth of a minute. Therefore, ensure that the display is not to thehundredth, or in minutes and seconds. If the aircraft is near to the Zero Degree E/W(Greenwich) Meridian, remember the risk of confusing east and west.‣ Before entering Oceanic Airspace make a careful check of LRNS positions at or near to thelast navigation facility – or perhaps the last but one.NAT Doc 007 87 Edition 2010