World Air Ops | NAT | Doc 007 MNPS Guidance

Guidance concerning Air Navigation in and above the NAT MNPSA CHAPTER 8continuous outage of RAIM capability of greater than 51 minutes in MNPS airspace means again that theflight should be re-routed, delayed or cancelled. It is understood that some prediction programmes carry outboth these checks together.Note - Derivation of the 51 minute limit – At the instant the RAIM capability is lost, it isassumed that the GPS navigation solution proceeds to direct the aircraft away from track at aspeed of 35 knots. With the current MNPS track spacing of 60 nautical miles, it is further assumedthat aircraft on adjacent tracks have a lateral “safety buffer” of 30 nautical miles. At 35 knots itwill take an aircraft 51 minutes to exit this “safety buffer”. It should be noted that this is a veryconservative methodology and it is thought unlikely that a RAIM outage alone could cause sucherrant navigation behaviour.Loading of Initial Waypoints8.3.14 The manual entry of waypoint data into the navigation systems must be a co-ordinatedoperation by two persons, working in sequence and independently: one should key in and insert the data,and subsequently the other should recall it and confirm it against source information. It is not sufficient forone crew member just to observe or assist another crew member inserting the data.8.3.15 The ramp position of the aircraft, plus at least two additional waypoints, or, if the onboardequipment allows, all the waypoints relevant to the flight, should be loaded while the aircraft is at the ramp.However, it is more important initially to ensure that the first en route waypoint is inserted accurately.Note - The vast majority of commercial air transport aircraft operating in MNPS airspace have anIRS/INS as part of their Long Range navigation fit. An increasing number of those with IRS/INSalso have GPS and whilst GPS may then be considered the primary LRNS, these aircraft are stillrequired to input the ramp position. This should then be compared with the GPS solution. Forthose few aircraft with GPS as the only LRNS, whilst there may be no need to actually load theramp position, it is good airmanship and recommended operational practice to compare thepublished ramp position with the GPS-derived position. Without selective availability GPS shouldgive a position within 30 metres of the published ramp position. If the GPS position is more than100 metres from the published ground position, then the cause should be investigated. If sufficientsatellites are in view the most likely causes are GPS receiver error, atmospheric interference, or,incorrect ramp co-ordinates.8.3.16 During flight, at least two current waypoints beyond the leg being navigated should bemaintained in the Control Display Units (CDUs) until the destination ramp co-ordinates are loaded. Twopilots should be responsible for loading, recalling and checking the accuracy of the inserted waypoints; oneloading and the other subsequently recalling and checking them independently. However, this processshould not be permitted to engage the attention of both pilots simultaneously during the flight. Whereremote loading of the units is possible, this permits one pilot to cross-check that the data insertedautomatically is indeed accurate.8.3.17 An alternative and acceptable procedure is for the two pilots silently and independently toload their own initial waypoints and then cross-check them. The pilot responsible for carrying out theverification should work from the CDU display to the Master Document rather than in the opposite direction.This may lessen the risk of the pilot 'seeing what is expected to be seen’ rather than what is actuallydisplayed.Flight Plan Check8.3.18 The purpose of this check is to ensure complete compatibility between the data in the MasterDocument and the calculated output from the navigation systems. Typical actions could include:NAT Doc 007 51 Edition 2010