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North Atlantic High Level Airspace (NAT HLA)

Airspace

By the time you read this, it will probably be out of date . . .

But perhaps up-to-date enough to make a difference. All of us who fly the North Atlantic for a living are in a continuing battle to keep up with the changing requirements. I think I have a handle on it. (At least at this snapshot in time.)


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Photo: NAT HLA, NAT Doc 007, figure 1.

Click photo for a larger image

Summary of Requirements

How do you know where you can fly? It all depends on your Performance Based Communications, Navigation, Surveillance capabilities. The Navigation we know about: that's PBN, after all. The rest is now being called PBCS, at least tentatively.

If you have the following equipment: You can fly:
Communications Navigation Surveillance
VHF VOR, DME, ADF Mode C Limited parts of the NAT HLA
HF (in Shanwick OCA) 1 LRNS VHF / HF Position Reports Limited parts of the NAT HLA

Note that we are talking about equipment for these parts of the airspace. Click on the links in the right column to learn about just how limited this can be. If you want greater access, you will need communications, navigation, and surveillance capabilities and those require authorizations.

If you have the following authorizations: You can fly:
Communications Navigation Surveillance
HF RNP 10 and 2 LRNS HF Position Reports NAT Tracks, NAT HLA
(Except FL350-390)
CPDLC RNP 10 and 2 LRNS ADS-C NAT Tracks, NAT HLA
(All Flight Levels)
*
CPDLC / RCP 240 RNP 4 and 2 LRNS ADS-C / RSP 180 NAT Tracks, NAT HLA
(All Flight Levels)

* The NAT Tracks between FL350 - 390 require RCP 240 and RSP 180.

A Summary of Changes

  • March 29, 2018 — PBCS required to fly NAT Tracks between FL350 - 390, you need RCP 240 and RSP 180
  • January 4, 2018 — The number of RLatSM tracks expanded to include most tracks between FL350 - 390.
  • January 1, 2017 — TCAS 7.1 required in entire NAT region.
  • December 7, 2017 — Data Link required FL 350 - 390, except for Tango routes, the airspace north of 80N, Surveillance airspace, Blue Spruce routes, and New York OCA.
  • December 2015 — RLatSM instituted for 3 Core tracks.

A Summary of Authorizations

  • A056 — Data Link Communications (you will need this for ADS-C and CPDLC)
  • B036 — Required Navigation Performance Airspace (you will need this for RNP-4 or RNP-10)
  • B039 — North Atlantic High Level Airspace (NAT HLA), formerly North Atlantic Minimum Navigation Performance Specifications (NAT/MNPS) Airspace
  • B046 — Reduced Vertical Separation Minimum (RVSM) Airspace

Limited parts of the NAT HLA

There is more to this than shown in this short paragraph from NAT Doc 007. You will probably be transiting the airspace of several countries (Canada, Greenland, Iceland, Scotland, Ireland, to name a few) and will need to get smart about their individual requirements.

[NAT Doc 007, Forward] Aircraft without NAT HLA or RVSM Approvals may, of course, also fly across the North Atlantic below FL285. However, due consideration must be given to the particular operating environment. Especially by pilots/operators of single and twin engine aircraft. Weather conditions can be harsh; there are limited VHF radio communications and ground-based navigation aids; and the terrain can be rugged and sparsely populated. International General Aviation (IGA) flights at these lower levels constitute a very small percentage of the overall NAT traffic but they account for the vast majority of Search and Rescue operations.

Flights Planning to Operate Without Using HF Communications

[NAT Doc 007, ¶4.2.12 Aircraft with only functioning VHF communications equipment should plan their route according to the information contained in the appropriate State AIPs and ensure that they remain within VHF coverage of appropriate ground stations throughout the flight. VHF coverage charts are shown in Attachment 4. Some may permit the use of SATVOICE to substitute for or supplement HF communications. However, it must also be recognised that the Safety Regulator of the operator may impose its own operational limitations on SATVOICE usage. Any operator intending to fly through the NAT HLA without fully functional HF communications or wishing to use an alternative medium should ensure that it will meet the requirements of its State of Registry and those of all the relevant ATS providers throughout the proposed route.

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Photo: VHF Coverage at FL300, NAT Doc 007, Attachment 4.

Note: There are also charts for FL100 and FL200.

Click photo for a larger image

Flights Planning to Operate with a Single Functioning LRNS, or Normal Short-Range Navigation Equipment Only.

[NAT Doc 007, ¶3.2.1]

  1. *Blue Spruce Routes require state approval for NAT HLA operations, and are listed below:
    • - MOXAL – RATSU (for flights departing Reykjavik Airport)
    • (VHF coverage exists. Non HF equipped aircraft can use this route)

    • - OSKUM – RATSU (for flights departing Keflavik Airport)
    • (VHF coverage exists. Non HF equipped aircraft can use this route)

    • - RATSU – ALDAN – KFV (Keflavik)
    • (VHF coverage exists. Non HF equipped aircraft can use this route)

    • - ATSIX – 61°N 12°34'W – ALDAN – KFV
    • (VHF coverage exists. Non HF equipped aircraft can use this route)

    • - GOMUP – 60°N 15°W – 61°N 16°30'W – BREKI – KFV
    • (VHF coverage exists. Non HF equipped aircraft can use this route)

    • - KFV – EPENI – 63°N 30°W – 61°N 40°W – OZN
    • (VHF coverage exists. Non HF equipped aircraft can use this route)

    • - KFV – SOPEN – DA (Kulusuk) – SF (Kangerlussuaq) – YFB
    • (VHF coverage exists. Non HF equipped aircraft can use this route)

    • - SF (Kangerlussuaq) – DARUB – YXP
    • (VHF coverage exists. Non HF equipped aircraft can use this route)

    • - OZN – 59°N 50°W – AVUTI (FL290 to FL600) - PRAWN – YDP
    • (VHF coverage exists. Non HF equipped aircraft can use this route)

    • OZN – 59°N 50°W – CUDDY (FL290 to FL600) - PORGY – HO
    • (VHF coverage exists. Non HF equipped aircraft can use this route)

    • - OZN – 58°N 50°W – HOIST – YYR
    • (VHF coverage exists. Non HF equipped aircraft can use this route)

    State approval for NAT HLA operations is required for operations along Blue Spruce routes.

  2. routes between Northern Europe and Spain/Canaries/Lisbon FIR. (T9*, T13, T213 and T16);
  3. *routings between the Azores and the Portuguese mainland (T25) and between the Azores and the Madeira Archipelago;
  4. routes between Iceland and Constable Pynt on the east coast of Greenland and between Kook Islands on the west coast of Greenland and Canada;
  5. defined routes of short stage lengths where aircraft equipped with normal short-range navigation equipment can meet the NAT HLA track-keeping criteria as follows:
    • - G3- VALDI - MY (Myggenes) - ING – KFV
    • - G11 - PEMOS - MY (Myggenes)
    • State approval for NAT HLA approval is required for operations on G3 and G11.

    Note: *routes/routings identified with an asterisk in sub paragraphs (a), (b), (c) and (d) above may be flight planned and flown by approved aircraft equipped with normal short-range navigation equipment (VOR, DME, ADF) and at least one approved fully operational LRNS.

The NAT HLA (Except FL350-390)

Flying anywhere within the NAT HLA means you will need some kind of authorization (an LOA or OpsSpecs) and will need to be RVSM compliant. If you are not RVSM approved, however, there are special provision to allow you to climb and descend through RVSM levels, detailed in NAT Doc 007, ¶1.6

What about navigation accuracy? Well that depends on when you got your current authorization and which parts of the NAT HLA you want to use.

Location

[NAT Doc 007, Forward]

  • A large portion of the airspace of the North Atlantic Region, through which the majority of these North Atlantic crossings route between FLs 285 and 420 inclusive, is designated as the NAT High Level Airspace (NAT HLA). Within this airspace a formal Approval Process by the State of Registry of the aircraft or the State of the Operator ensures that aircraft meet defined NAT HLA Standards and that appropriate crew procedures and training have been adopted.
  • The lateral dimensions of the NAT HLA include the following Control Areas (CTAs): REYKJAVIK, SHANWICK (excluding SOTA & BOTA), GANDER, SANTA MARIA OCEANIC, BODO OCEANIC and the portion of NEW YORK OCEANIC EAST which is north of 27°N.

Authorization

[NAT Doc 007, ¶1.1.3] Aircraft operating within the NAT HLA are required to meet specified navigation performance in the horizontal plane through the carriage and proper use of navigation equipment that meets identified standards and has been approved as such by the State of Registry or State of the operator for the purpose. Such approvals encompass all aspects affecting the expected navigation performance of the aircraft, including the designation of appropriate cockpit/flight deck operating procedures.

[NAT Doc 007, ¶1.1.4] All aircraft intending to operate within the NAT HLA must be equipped with altimetry and height-keeping systems which meet RVSM Minimum Aircraft System Performance Specifications (MASPS). RVSM MASPS are contained in ICAO Doc 9574 and detailed in designated FAA document, AC91-85 (latest edition).

Longitudinal Navigation

[NAT Doc 007, ¶1.3.1]

  • Time-based longitudinal separations between subsequent aircraft following the same track (in-trail) and between aircraft on intersecting tracks in the NAT HLA are assessed in terms of differences in ATAs/ETAs at common points. The time-based longitudinal separation minima currently used in the NAT HLA are thus expressed in clock minutes. The maintenance of in-trail separations is aided by the application of the Mach Number Technique.
  • Mach Number Technique has been required in the North Atlantic for quite a while. About the only thing that has changed since its inception is the tolerance went from 0.002 Mach to zero. But there is more to longitudinal separation than just speed control.

  • However, aircraft clock errors resulting in waypoint ATA errors in position reports can lead to an erosion of actual longitudinal separations between aircraft. It is thus vitally important that the time-keeping device intended to be used to indicate waypoint passing times is accurate, and is synchronised to an acceptable UTC time signal before commencing flight in the NAT HLA. In many modern aircraft, the Master Clock can only be reset while the aircraft is on the ground. Thus the pre-flight procedures for any NAT HLA operation must include a UTC time check and resynchronisation of the aircraft Master Clock (typically the FMS).
  • To take advantage of Reduced Longitudinal Separation, you will need something more than just good Mach Number technique and a clock. See Reduced Longitudinal Separation, for more.

Lateral Navigation

[NAT Doc 007, ¶1.3.2] There are two navigational equipment requirements for aircraft planning to operate in the NAT HLA. One refers to the navigation performance that should be achieved, in terms of accuracy. The second refers to the need to carry standby equipment with comparable performance characteristics (ICAO Annex 6 (Operation of Aircraft) refers).

[NAT Doc 007, ¶1.3.3] The navigation system accuracy requirements for NAT MNPSA/HLA operation should only be based on the PBN specifications, RNP 10 (PBN application of RNAV 10) or RNP 4. Although when granting consequent approval for operations in MNPSA/NAT HLA, States should take account of the RNP 10 time limits for aircraft equipped with dual INS or inertial reference unit (IRU) systems. All approvals issued after 04 February 2016 must be designated as “NAT HLA” approvals.

[NAT Doc 007, ¶1.3.4] Additionally, in order for the 50 NM lateral separation minimum to be utilized in the New York Oceanic East the following navigation performance criteria must also be met by aircraft with RNAV 10 (RNP 10) approvals:

  • the proportion of the total flight time spent by aircraft 46 km (25 NM) or more off the cleared track shall be less than 9.11 × 10-5; and
  • the proportion of the total flight time spent by aircraft between 74 and 111 km (40 and 60 NM) off the cleared track shall be less than 1.68 × 10-5.

[NAT Doc 007, ¶1.3.5] And similarly the additional criteria which must be met by aircraft approved as RNP 4 are as follows:

  • a) the proportion of the total flight time spent by aircraft 28 km (15 NM) or more off the cleared track shall be less than 5.44 × 10-5; and
  • the proportion of the total flight time spent by aircraft between 44 and 67 km (24 and 36 NM) off the cleared track shall be less than 1.01 × 10-5.

NAT Tracks

The Organized Track System (OTS) carries with it all the restrictions of flying in the NAT HLA plus a few more. You must also be careful in that there are several layers of authorizations involved. You could be permitted the lower altitudes and standard spacing, all altitudes with the chance of decreased longitudinal spacing, and all altitudes with the chance of decreased longitudinal and lateral spacing.

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Photo: Example of Daytime Westbound NAT Organized Track System, NAT Doc 007, Figure 2.

Click photo for a larger image

[NAT Doc 007, ¶2.1]

  • 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 uni-directionally, 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.
  • The flight levels normally associated with the OTS are FL310 to FL400 inclusive. These flight levels, and their use have been negotiated and agreed by the NATS ATS providers and are published as the Flight Level Allocation Scheme (FLAS). The FLAS also determines flight levels available for traffic routing partly or wholly outside of the OTS as well as flights operating outside of the valid time periods of the OTS; often referred to as “transition times’.
  • The hours of validity of the two Organised Track Systems (OTS) are as follows:
    • (Westbound) Day-time OTS 1130 UTC to 1900 UTC at 30°W
    • (Eastbound) Night-time OTS 0100 UTC to 0800 UTC at 30°W

    Note: Changes to these times can be negotiated between Gander and Shanwick OACCs and the specific hours of validity for each OTS are indicated in the NAT track message. For flight planning, operators should take account of the times as specified in the relevant NAT track message(s). Tactical extensions to OTS validity times can also be agreed between OACCs when required, but these should normally be transparent to operators.

  • Use of the OTS tracks is not mandatory Aircraft may flight plan on random routes which remain clear of the OTS or may fly on any route that joins, leaves, or crosses the OTS. Operators must be aware that while ATC will make every effort to clear random traffic across the OTS at requested levels, re-routes or significant changes in flight level from those planned are very likely to be necessary during most of the OTS traffic periods. A comprehensive understanding of the OTS and the FLAS may assist flight planners in determining the feasibility of flight profiles.

[NAT Doc 007, ¶2.4]

  • To ensure a smooth transition from night-time to day-time OTSs and vice-versa, a period of several hours is interposed between the termination of one system and the commencement of the next. These periods are from 0801 UTC to 1129 UTC: and from 1901 UTC to 0059 UTC.
  • During the changeover periods some restrictions to flight planned routes and levels are imposed. Eastbound and westbound aircraft operating during these periods should file flight level requests in accordance with the Flight Level Allocation Scheme (FLAS) as published in the UK and Canada AIPs.
  • It should also be recognised that during these times there is often a need for clearances to be individually co-ordinated between OACCs and cleared flight levels may not be in accordance with those flight planned. If, for any reason, a flight is expected to be level critical, operators are recommended to contact the initial OACC prior to filing of the flight plan to ascertain the likely availability of required flight levels.

PBCS Tracks

[NAT Doc 007, ¶4.1.11] Flights which are planned to follow an OTS track for its entire length (during the OTS periods) may plan any of the levels published for that track, keeping in mind PBCS and DLM requirements.

Note: PBCS tracks will be identified in Note 3 of the OTS message. Operators planning to operate in the altitude band FL350-390 on the PBCS OTS are subject to equipage and authorization requirements as outlined in NAT OPS Bulletin, “Implementation of Performance Based Separation Minima”.

The NAT HLA (All Flight Levels)

They have gradually moved from selected tracks to all the tracks: if you want to fly between FL350 and FL390, inclusive, you will need data link.

[NAT Doc 007, ¶1.8.1] The NAT Data Link Mandate (DLM) is being implemented in phases. The goals are that: by 2018, 90% of aircraft operating in the NAT region airspace at FL290 and above will be equipped with FANS 1/A or equivalent ADS-C and CPDLC and that by 2020, 95% of aircraft operating in that airspace will be so equipped. The DLM requires aircraft to be equipped with, and operating, CPDLC and ADS-C in specific portions of the NAT region. Currently, the mandate incorporates FL350 to FL390 throughout the NAT region.

[NAT Doc 007, ¶4.1.9] Flight planning in the NAT at FL350 to FL390 inclusive is restricted by the Data Link Mandate. Chapter 1 outlines equipment required to flight plan in the NAT at FL350 to FL390 inclusive as well as any airspace not confined by the DLM.

[ICAO Doc 7030, Amendment 9, NAT ¶3.3]

Area of applicability

3.3.1 All aircraft intending to conduct flights in the airspace defined below shall be fitted with and shall operate controller-pilot data link communications (CPDLC) equipment:

a) from 7 February 2013, on specified tracks and flight levels within the NAT organized track system (OTS); and

b) from 5 February 2015, in specified portions of NAT minimum navigation specifications (MNPS) airspace.

Note 1.— The specified tracks and flight level band within the NAT OTS will be published by the States concerned in national AIPs and identified daily in the NAT track message.

Note 2.— The specified portions of NAT MNPS airspace and aircraft equipment performance requirements where applicable will be published by the States concerned in national AIPs.

Means of compliance

3.3.2 Operators intending to conduct flights within the airspace specified in 3.3.1 shall obtain CPDLC operational authorization, where applicable, either from the State of Registry or the State of the Operator. The State of Registry or the State of the Operator shall verify that the equipment has been certified in accordance with the requirements specified in RTCA DO-258/EUROCAE ED-100 or equivalent, capable of operating outside VHF data link coverage.

3.3.3 The services provided within the airspace specified in 3.3.1 shall comply with the Oceanic Safety and Performance Requirements as specified in RTCA DO-306/EUROCAE ED-122 or equivalent.

Note.— Additional guidance can be found in the ICAO Global Operational Data Link Document (GOLD).

[ICAO Doc 7030, Amendment 9, NAT ¶5.4]

Area of applicability

5.4.1 All aircraft intending to conduct flights in the airspace defined below shall be fitted with and shall operate automatic dependent surveillance – contract (ADS-C) equipment:

a) from 7 February 2013, on specified tracks and on specified flight levels within the NAT organized track system (OTS); and

b) from 5 February 2015, in specified portions of NAT minimum navigation specifications (MNPS) airspace.

Note 1.— The specified tracks and flight level band within the NAT OTS will be published by the States concerned in national AIPs and identified daily in the NAT track message.

Note 2.— The specified portions of NAT MNPS airspace and aircraft equipment performance requirements, where applicable, will be published by the States concerned in national AIPs.

Means of compliance

5.4.2 Operators intending to conduct flights within the airspace specified in 5.4.1 shall obtain an ADS-C operational authorization, where applicable, either from the State of Registry or the State of the Operator. The State of Registry or the State of the Operator shall verify that the equipment has been certified in accordance with the requirements specified in RTCA DO-258/EUROCAE ED-100 or equivalent, capable of operating outside VHF data link coverage.

5.4.3 The data link services provided within the NAT airspace shall comply with the Oceanic Safety and Performance Requirements as specified in RTCA DO-306/EUROCAE ED-122 or equivalent. Conformance monitoring shall provide alerts to the controller when reports do not match the current flight plan, and the following ADS contracts shall be used:

a) ADS periodic contracts at an interval consistent with safety requirements and published by the States concerned in national AIPs; and

b) ADS event contracts that include the following event types:

1) lateral deviation event (LDE) with a lateral deviation threshold of 9.3 km (5 NM) or less;

2) level range deviation event (LRDE) with a vertical deviation threshold of 90 m (300 ft) or less; and

3) waypoint change event (WCE) at compulsory reporting points.

Note.— Additional guidance can be found in the ICAO Global Operational Data Link Document (GOLD).

Training

You will have to update your old MNPS LOA or OpsSpec (B039) for NAT HLA by 2020 and part of that process will be a cross examination by your local FAA about how well prepared you are for these changing standards. Part of that examination will include your training program.

[NAT Doc 007, ¶1.3.8] It is essential that flight crews obtain proper training for NAT HLA and RVSM operations in line with procedures described in other chapters of this document.

[NAT Doc 007, ¶8.5.13] Training and drills should ensure that minor emergencies or interruptions to normal routine are not allowed to distract the flight crew to the extent that the navigation system is mishandled.

[NAT Doc 007, ¶12.1.4] Flight crew training and consequent approval for NAT HLA operations should include instruction on what actions are to be considered in the event of navigation system failures. This chapter provides guidance on the detection of failures and what flight crew action should be considered, together with details of the routes that may be used when the aircraft’s navigation capability is degraded below that required for unrestricted operations in the NAT HLA.

Keeping Up-to-Date

In case you were thinking I was joking about this page being out of date as soon as it was written, I was not. There are so many players out there, around the world, and no central mechanism to keep everyone else current. So you can just do your best. Here are my methods.

Good sources to monitor for changes:

  • NAT OPS Bulletins — available at www.icao.int/EURNAT/, following “EUR & NAT Documents”, then “NAT Documents”, in folder “NAT OPS Bulletins”.
  • NBAA Air Mail — https://www.nbaa.org/airmail/), several forums, including one for international operations. (Membership required.)
  • OpsGroup — opsgroup.com, a platform for pilots, controllers, dispatchers, and managers to ask questions, provide answers, and to learn from peers. (Membership required.)

See Also

Oceanic Clearance

Performance Based Communications and Surveillance (PBCS)

Regional: North Atlantic

Book Notes

Portions of this page can be found in the book International Operations Flight Manual, Part III, Chapter 7.

References

14 CFR 91, Title 14: Aeronautics and Space, General Operating and Flight Rules, Federal Aviation Administration, Department of Transportation

FAA Domestic/International NOTAMs.

FAA Orders 8400 and 8900

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

ICAO Doc 7030, Amendment 1, International Civil Aviation Organization, 8 January 2009

ICAO Doc 7030, Amendment 9, International Civil Aviation Organization, 2 October 2017

Jeppesen Airway Manual

ICAO Nat Doc 007, North Atlantic Operations and Airspace Manual, v. 2019-2, applicable from 28 March 2019

NAT OPS Bulletin 2010-026, Trial of a 5 Minute Along Track Longitudinal Separation in the Shanwick OCA, Issued 16 March 2012

NAT OPS Bulletin 2012-030, Reduced Longitudinal Separation (RLongSM) Trial, Effective 17 September 2012

NAT OPS Bulletin 2016_001, Re-naming of the Nat MNPSA to NAT HLA, Effective 4 February 2016

Transport Canada Aeronautical Information Manual

Revision: 20190224
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