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North Atlantic (NAT)

International Operations Regional

Regional differences from the ICAO standard can be found in ICAO Document 7030 and your Jeppesen Airway Manual. Both of the sources, however, can be out of date. See Regional Introduction for ideas about getting up-to-date information.


 

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Figure: NAT Region, from Eddie's notes.

Communications

North Atlantic Requirement

ICAO Doc 7030, §NAT, ¶3.4.1] Within the NAT Region, aircraft equipped for SATCOM voice shall restrict the use of such equipment to emergencies and non-routine situations. An unforeseen inability to communicate by voice radio constitutes a non-routine situation. Since oceanic traffic typically communicates through aeradio facilities, a SATCOM call due to an unforeseen inability to communicate by other means should be made to such a facility rather than the ATC centre unless the urgency of the communication dictates otherwise. Dedicated SATCOM telephone numbers (short codes) for aeradio facilities and air traffic control facilities are published in national AIPs.

HF is required for U.S. Operators for just about every oceanic region in the world, though SATCOM can be used. The North Atlantic places this additional restriction on the use of SATCOM in place of HF for position reports.

More about this: HF.

This region is moving from a mix of navigation requirements to the system of Performance Based Navigation outlined in ICAO Document 9613. Current navigation requirements are available on Jeppesen Airway Manual Air Traffic Control pages and Chapter 4 of each region covered by ICAO Document 7030.

RNAV 10 (RNP 10)

[ICAO Doc 7030 Amendment 1, §NAT, ¶4.1.1.1.]

  • A lateral separation minimum of 93 km (50 NM) may be applied between flights operating within the control area of the New York Oceanic FIR.
  • The aircraft and operator must be approved RNP 10 or RNP 4 by the State of the Operator or the State of Registry, as appropriate. RNP 10 is the minimum navigation specification for the application of 93 km (50 NM) lateral separation.

More about this:Required Navigation Performance-10 (RNP-10).

Keep in mind RNP 10 is an exception to the rule of Required Navigation Performance standards, "RNAV 10" retains the "RNP 10" designation for matters of convenience.

Minimum Navigation Performance Specifications (MNPS)

[ICAO Doc 7030 Amendment 1, §NAT, ¶4.1.1.5.1.]

  • The MNPS shall be applicable in that volume of airspace between FL 285 and FL 420 within the Oceanic Control Areas of Santa Maria, Shanwick, Reykjavik, Gander Oceanic and New York Oceanic, excluding the area west of 60°W and south of 38°30′N.
  • For flights within the volume of airspace specified in 4.1.1.5.1.1 aircraft shall have lateral navigation performance capability such that:
    1. the standard deviation of lateral track errors shall be less than 11.7 km (6.3 NM);
    2. the proportion of the total flight time spent by aircraft 56 km (30 NM) or more off the cleared track shall be less than 5.3 × 10-4; and
    3. the proportion of the total flight time spent by aircraft between 93 and 130 km (50 and 70 NM) off the cleared track shall be less than 1.3 × 10-5.

The MNPS has been replaced by the North Atlantic High Level Airspace (NAT HLA) but ICAO Doc 7030 hasn't caught up yet. For now, you can just associate NAT HLA with MNPS.

More about this: North Atlantic Airspace (NAT HLA).

WGS-84 Compliance

All three countries listed in the NAT region, the Azores, Greenland, and Iceland are listed as WGS-84 in the Jeppesen WGS-84 website, but Greenland is listed only as partially compliant in their Jeppesen Airway Manual ATC page, dated 16 Aug 2013.

More about this: World Geodetic System 84 (WGS-84).

RVSM

[ICAO Doc 7030 Amendment 1, §NAT, ¶4.2.1.] RVSM shall be applicable in that volume of airspace between FL 290 and FL 410 inclusive in all FIRs of the NAT Region.

More about this: Reduced Vertical Separation Minimum (RVSM).

Altimeter Procedures

Transition altitude and level procedures vary by country.

More about this: Transition Altitude / Layer / Level.

Special Routings

North American Routes (NARs)

[NAT Doc 007, ¶3.3.1] The North American Routes (NARs) consist of a numbered series of predetermined routes which provide an interface between NAT oceanic and North American domestic airspace. The NAR System is designed to accommodate major airports in North America.

The NARs used to be in an easy to find location in paper copies of Jeppesen Airway manuals but not so much with the electronic version. The link provided by NAT Doc 007 died years ago. The FAA Order (7430.2A) that established them way back in 1984 was canceled in 2014. You can find a listing of the NARS in the JeppView North Atlantic En Route pages. (If you are flying a PlaneView cockpit, you will also seem them displayed if you select high altitude routes.)

Organized Track System (OTS)

[NAT Doc 007, ¶2.1.1.] As a result of passenger demand, time zone differences and airport noise restrictions, much of the North Atlantic (NAT) air traffic contributes to two major alternating flows: a westbound flow departing Europe in the morning, and an eastbound flow departing North America in the evening. The effect of these flows is to concentrate most of the traffic unidirectionally, with peak westbound traffic crossing the 30W longitude between 1130 UTC and 1900 UTC and peak eastbound traffic crossing the 30W longitude between 0100 UTC and 0800 UTC.

[NAT Doc 007, ¶2.1.2.] Due to the constraints of large horizontal separation criteria and a limited economical height band (FL310–400) the airspace is congested at peak hours. In order to provide the best service to the bulk of the traffic, a system of organised tracks is constructed to accommodate as many flights as possible within the major flows on or close to their minimum time tracks and altitude profiles. Due to the energetic nature of the NAT weather patterns, including the presence of jet streams, consecutive eastbound and westbound minimum time tracks are seldom identical. The creation of a different organised track system is therefore necessary for each of the major flows. Separate organised track structures are published each day for eastbound and westbound flows. These track structures are referred to as the Organised Track System or OTS.

[NAT Doc 007, ¶2.1.4.] Over the high seas, the NAT Region is primarily Class A airspace (at and above FL55) (See ICAO Doc. 7030 - NAT Regional Supplementary Procedures), in which Instrument Flight Rules (IFR) apply at all times. Throughout the NAT Region, below FL410, 1000 feet vertical separation is applied. However, airspace utilisation is under continual review, and within the MNPS portion of NAT airspace, in addition to the strategic and tactical use of 'opposite direction' flight levels during peak flow periods the Mach Number Technique is applied.

[NAT Doc 007, ¶2.3.1.] The agreed OTS is promulgated by means of t h e NAT Track Message via the AFTN to all interested addressees. A typical time of publication of the day-time OTS is 2200 UTC and of the night-time OTS is 1400 UTC.

[NAT Doc 007, ¶2.3.5.] The hours of validity of the two Organised Track Systems (OTS) are normally as follows:

  • Day-time OTS 1130 UTC to 1900 UTC at 30°W
  • Night-time OTS 0100 UTC to 0800 UTC at 30°W

ICAO Differences

Each country departs in some ways with the ICAO standard and common US practices. Pilots should always refer to the Jeppesen Airway Manual, Air Traffic Control, State Rules and Procedures pages for each country on their itineraries for differences with ICAO Standards, Recommended Practices and Procedures. More about this: US versus ICAO.

The following are a sampling of some of the differences, there are many more. You should check the Jeppesen Airway Manual State pages for every country you takeoff, overfly, or land.

Lost Communications

[NAT Doc 007, ¶6.6]

  • Rules and procedures for the operation of an aircraft following a radio communications failure (RCF) are established to allow ATC to anticipate that aircraft’s subsequent actions and thus for ATC to be able to provide a service to all other flights within the same vicinity, so as to ensure the continued safe separation of all traffic. The general principles of such rules and procedures are set out in Annexes 2 and 10 to the ICAO Convention. States publish in their AIPs specific RCF rules and regulations to be followed within their particular sovereign airspace.
  • It must be recognised that there is in general an underlying premise in “normal” radio communications failure procedures that they are for use when a single aircraft suffers an on-board communications equipment failure. Within the NAT Region and some adjacent domestic airspace (e.g. Northern Canada), where HF Voice is used for air-ground ATC communications, ionospheric disturbances resulting in poor radio propagation conditions can also interrupt these communications. While it is impossible to provide guidance for all situations associated with an HF communications failure, it is, however, extremely important to differentiate between two distinct circumstances: - firstly, an on-board communications equipment failure, resulting in an individual aircraft losing HF communications with ATC and; secondly, the occurrence of poor HF propagation conditions (commonly referred to as “HF Blackouts”), which can simultaneously interrupt HF air-ground communications for many aircraft over a wide area.
  • In the case of an on-board communications equipment failure, even though ATC loses contact with that aircraft, it can anticipate that aircraft’s actions and, if necessary, modify the profiles of other aircraft in the same vicinity in order to maintain safe separations.
  • However, the occurrence of poor HF propagation conditions can simultaneously interrupt HF air-ground communications for many aircraft over a wide area and ATC may then be unable to make any interventions to assure safe traffic separations using HF. Notwithstanding the growing use of Data link and SATCOM Voice for regular air-ground ATS communications in the NAT Region, all pilots must recognise that, pending the mandatory carriage and use of such means, an HF blackout will impact the ability of ATC to ensure the safe separation of all traffic. Hence, even if using other than HF for regular communications with ATC, pilots should still exercise appropriate caution when HF blackout conditions are encountered.
  • The following procedures are intended to provide general guidance for aircraft which experience a communications failure while operating in, or proposing to operate in, the NAT Region,. These procedures are intended to complement and not supersede State procedures/regulations.
  • General Provisions

    1. The pilot of an aircraft experiencing a two-way ATS communications failure should operate the SSR Transponder on identity Mode A Code 7600 and Mode C.
    2. When so equipped, an aircraft should use Satellite Voice Communications to contact the responsible aeradio station via special telephone numbers/short codes published in State AIPs (see also “HF Management Guidance Material for the NAT Region”). However, it must be appreciated that pending further system developments and facility implementations the capability for Ground(ATC)-initiated calls varies between different NAT OACs.
    3. If the aircraft is not equipped with SATCOM Voice then the pilot should attempt to use VHF to contact any (other) ATC facility or another aircraft, inform them of the difficulty, and request that they relay information to the ATC facility with which communications are intended.
    4. The inter-pilot air-to-air VHF frequency, 123.45 MHz, may be used to relay position reports via another aircraft. (N.B. The emergency frequency 121.5 MHz should not be used to relay regular communications, but since all NAT traffic is required to monitor the emergency frequency, it may be used, in these circumstances, to establish initial contact with another aircraft and then request transfer to the inter-pilot frequency for further contacts).
    5. In view of the traffic density in the NAT Region, pilots of aircraft experiencing a two-way ATS communications failure should broadcast regular position reports on the inter-pilot frequency (123.45 MHz) until such time as communications are re-established.

    Communications Procedures for Use in the Event of an On-board HF Equipment Failure

  • Use SATCOM Voice communications, if so equipped. (See General Provisions 2. above).
  • If not SATCOM Voice equipped try VHF relay via another aircraft (See General Provisions 3. & 4 above).
  • Communications Procedures for Use during Poor HF Propagation Conditions

  • Poor HF propagation conditions are the result of ionospheric disturbances. These are usually caused by sun-spot or solar flare activity creating bursts of charged particles in the solar wind which can spiral down around the Earth’s magnetic lines of force and distort or disturb the ionised layers in the stratosphere which are utilised to refract HF radio waves. As with the Aurora Borealis, which is of similar origin, these ionospheric disturbances most commonly occur in regions adjacent to the Magnetic Poles. Since the Earth’s North Magnetic Pole is currently located at approximately 87N 150W, flights through the North Atlantic and Northern Canada regions can, on occasion, experience resulting HF communications difficulties.
  • SATCOM Voice communications are unaffected by most ionospheric disturbances. Therefore, when so equipped, an aircraft may use SATCOM Voice for ATC communications (See General Provisions 2 above).
  • If not SATCOM Voice equipped, in some circumstances it may be feasible to seek the assistance, via VHF, of a nearby SATCOM Voice equipped aircraft to relay communications with ATC (See General Provisions 3. & 4. above).
  • Whenever aircraft encounter poor HF propagation conditions that would appear to adversely affect air-ground communications generally, it is recommended that all pilots then broadcast their position reports on the air-to-air VHF frequency 123.45 MHz. Given the density of traffic in the NAT Region and the fact that in such poor propagation conditions ATC will be unable to maintain contact with all aircraft, it is important that even those aircraft that have been able to establish SATCOM Voice contact also broadcast their position reports.
  • If for whatever reason SATCOM Voice communications (direct or relayed) are not possible, then the following procedures may help to re-establish HF communications. Sometimes these ionospheric disturbances are very wide-spread and HF air-ground communications at all frequencies can be severely disrupted throughout very large areas (e.g. simultaneously affecting the whole of the NAT Region and the Arctic.). However, at other times the disturbances may be more localised and/or may only affect a specific range of frequencies.
  • In this latter circumstance, HF air-ground communications with the intended aeradio station may sometimes continue to be possible but on a frequency other than either the primary or secondary frequencies previously allocated to an aircraft. Hence, in the event of encountering poor HF propagation conditions pilots should first try using alternative HF frequencies to contact the intended aeradio station.
  • However, while the ionospheric disturbances may be severe, they may nevertheless only be localized between the aircraft’s position and the intended aeradio station, thus rendering communications with that station impossible on any HF frequency. But the aeradio stations providing air-ground services in the NAT Region do co-operate as a network and it may, even then, still be possible to communicate with another aeradio station in the NAT network on HF and request that they relay communications. Efforts should therefore be made to contact other NAT aeradio stations via appropriate HF frequencies.
  • Nevertheless, as previously indicated, there are occasions when the ionospheric disturbance is so severe and so widespread that HF air-ground communications with any aeradio station within the NAT Region network are rendered impossible.
  • Rationale for Lost Communications Operational Procedures

  • Because of the density of oceanic traffic in the NAT Region, unique operational procedures have been established here to be followed by pilots whenever communications are lost with ATC. These procedures and the rationale for their development follow.
  • Tactical ATC Environment

  • In a tactical ATC environment,, such as one in which ATS Surveillance and VHF voice communications are used, ATC has continuous real-time data on the position/progress of all relevant traffic and the intentions of any individual aircraft with which ATC may have lost communications can be inferred from that aircraft’s filed flight plan. Hence, in such an environment, when voice communications with a single aircraft fail, the relevant published “lost comms procedures” normally require that aircraft to “land at a suitable aerodrome or continue the flight and adjust level and speed in accordance with the filed flight plan”. Communications blackouts affecting multiple aircraft, are not a feature of this type of VHF environment and hence in these circumstances, if required, ATC will be able to re-clear other traffic to ensure safe separations are maintained.
  • Procedural ATC Environment

  • However, in a (largely) non-ATS surveillance environment such as the North Atlantic, ATC must rely significantly upon the HF Voice Position Reports communicated by each aircraft for position, progress and intent data. Communications equipment failures and/or poor propagation conditions can interrupt the provision of this information. Therefore, to mitigate against such occurrences in the busy NAT HLA, outside of VHF coverage, ATC often employs strategic traffic planning and issues Oceanic Clearances which have been pre-co-ordinated with downstream OACs. Flights that continue to follow such a pre-coordinated strategic oceanic clearance are thereby guaranteed conflict-free progress to oceanic exit, even if no ATS communications are subsequently possible with any one, or even with all, of those strategically planned aircraft.
  • Every effort is made by the initial NAT OAC to clear aircraft as per their filed flight plans. However, this is not always possible, particularly during peak traffic flow periods. Aircraft may receive clearances at flight levels or speeds other than those flight planned or, less frequently, may be cleared on oceanic tracks via entry or exit points other than those contained in the filed flight plan. Also it must be recognized that while a filed NAT flight plan may contain one or more step climbs for execution within the NAT Region, the initially issued oceanic clearance, or even any subsequently updated clearance (i.e. reclearance), has only been co-ordinated for a single ( i.e. initial or current) flight level. It must therefore be appreciated that it is only the flight routing and profile contained in the last received clearance that ATC has probed for conflicts. Unless this clearance is precisely the same as the filed flight plan, in any lost communications situation in the NAT Region, if a pilot in receipt of a clearance unilaterally reverts to his/her filed flight plan (even by simply executing a later step climb), then no guarantee of conflict-free progress exists. Consequently, if a NAT aircraft loses the possibility of communications with the relevant OAC at any time after receiving and acknowledging a clearance, and the pilot elects to continue the flight, then the aircraft must adhere strictly to the routing and profile of the last received clearance until exiting the NAT Region. Pilots must not unilaterally revert to their filed flight plan.

These are exceptions to ICAO Lost Comm procedures.

More about this: Lost Communications.

Strategic Lateral Offset Procedure (SLOP)

[NAT Doc 007, ¶8.5.3] Distributing aircraft laterally and equally across the three available positions adds an additional safety margin and reduces collision risk. SLOP is now a standard operating procedure for the entire NAT Region and pilots are required to adopt this procedure as is appropriate. In this connection, it should be noted that:

  1. Aircraft without automatic offset programming capability must fly the centreline.
  2. If you have automatic offset programming capability, you MUST SLOP in the North Atlantic. If you do not have automatic offset programming capability, you MAY NOT SLOP.

  3. To achieve an equal distribution of flying the centreline or 1 NM (one nautical mile) right or 2 NM (two nautical miles) right of centerline, it is recommended that pilots of aircraft capable of programming automatic offsets should randomly select flying centreline or an offset. (See Note in 8.5.2 a) above) In order to obtain lateral spacing from nearby aircraft (i.e. those immediately above and/or below), pilots should use whatever means are available (e.g. ACAS/TCAS, communications, visual acquisition, GPWS) to determine the best flight path to fly.
  4. An aircraft overtaking another aircraft should offset within the confines of this procedure, if capable, so as to create the least amount of wake turbulence for the aircraft being overtaken.
  5. For wake turbulence purposes, pilots should fly one of the three positions shown above. Pilots should not offset to the left of centreline nor offset more than 2 NM right of centreline. Pilots may contact other aircraft on the air-to-air channel, 123.45 MHz, as necessary; to coordinate the best wake turbulence mutual offset option. (Note. It is recognized that the pilot will use his/her judgement to determine the action most appropriate to any given situation and that the pilot has the final authority and responsibility for the safe operations of the aeroplane. See also Chapter 13, paragraph 13.5.) As indicated below, contact with ATC is not required.
  6. Pilots may apply an offset outbound at the oceanic entry point and must return to centreline prior to the oceanic exit point unless otherwise authorized by the appropriate ATS authority or directed by the appropriate ATC unit.
  7. Aircraft transiting ATS Surveillance-controlled airspace mid-ocean should remain on their already established offset positions.
  8. There is no ATC clearance required for this procedure and it is not necessary that ATC be advised.
  9. Voice Position reports should be based on the waypoints of the current ATC clearance and not the offset positions.

If you have automatic offset capability, SLOP is mandatory for you in the North Atlantic.

More about this: Strategic Lateral Offset Procedure (SLOP).

References

ICAO Doc 7030 - Regional Supplementary Procedures, International Civil Aviation Organization, 2 2008

ICAO Doc 9613 - Performance Based Navigation (PBN) Manual, International Civil Aviation Organization, 2008

ICAO NAT Doc 007, North Atlantic Operations and Airspace Manual, v 2017-1

Revision: 20170504
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