2017-02

Airworthiness Approval and Certification Considerations for Navigation in Northern Domestic Airspace and Polar Regions

Effective Date: 1 March 2017

Reference: TAM Part 2, Chapter 3

OPI / Telephone: DTAES 6-4C1 / 819-939-4675

1        Purpose

1.1            Both civil (reference 3.2.1.o) and military (reference 3.2.1.c., Book #1 of 2, Chapter 8, page 8-2/13, para 8) operational regulations require a means of establishing direction that is not dependent upon a magnetic source when operating within the Northern Domestic Airspace (NDA). These operational regulations exist because anomalies with the Earth’s magnetic field in the Polar Regions cause erroneous magnetic heading indications. Aircraft, therefore, use True Heading information when flying in NDA.  Properly certified navigation equipment, as well as special techniques and/or procedures, are critical to safe operation in polar areas, including the area of magnetic uncertainty (reference 3.2.1.n).

1.2             This Technical Airworthiness Authority (TAA) Advisory addresses the technical airworthiness approval requirements for navigation equipment providing True Heading outputs and long-range navigation capability (i.e., Inertial Navigation Systems (INS) and Global Navigation Satellite System (GNSS)), for use in the NDA during Night and Instrument Flight Rules (IFR) operations. It does not address the other equipage and operational requirements (i.e., surveillance equipment, flight or basic navigation instruments, cold temperature certification to limits other than those already defined in the Aircraft Operation Instructions (AOI) or Flight Manual (FM), gravel runway certification, etc.) that may be necessary for Department of National Defence/Canadian Armed Forces (DND/CAF) fleets to conduct NDA operations. Communications aspects associated with operations in NDA are also discussed.

2        Applicability

2.1            This advisory applies to all DND/CAF personnel, as well as their support contractors, who are seeking to obtain an Airworthiness Approval and Technical Airworthiness Clearance for night and/or IFR operations in NDA on DND-registered aircraft.

2.2            This guidance is not intended to apply to DND-registered aircraft that already have a clearance to operate in the NDA. However, if significant design changes are incorporated, which could affect the onboard navigation system capabilities in the NDA, these changes should be evaluated against the criteria in this document.

2.3            The methodology in this advisory assesses the impact of high latitude (NDA and Polar) operating conditions on the function and performance of equipment required for Night and IFR operations. The FM will be annotated to identify any applicable limitation or restriction.

2.4            It is highly recommended that the TAA and the Operational Airworthiness Authority (OAA) staff be engaged early into, and throughout, the approval process.

3        Related Material

3.1       Definitions

3.1.1.        Nil.

3.2       Regulatory References

3.2.1         The following references should be used in conjunction with this advisory, as appropriate:

  1. C-05-005-001/AG-001 – Technical Airworthiness Manual, Part 2, Chapter 3 – Technical Airworthiness Clearance;
  2. B-GA-104-000/FP-001 – Operational Airworthiness Manual;
  3. B-GA-100-001/AA-000 – National Defence Flying Orders;
  4. MIL-HDBK-516C, Airworthiness Certification Criteria, dated 12 December 2014;
  5. U.S. Title 14 Code of Federal Regulations (14 CFR), Chapter I, Subchapter C - Aircraft, Part 23, Airworthiness Standards: Normal, Utility, Acrobatic, and Commuter Category Airplanes.
  6. U.S. 14 CFR, Chapter I, Subchapter C – Aircraft, Part 25, Airworthiness Standards: Transport Category Airplanes;
  7. U.S. 14 CFR, Chapter I, Subchapter C – Aircraft, Part 27, Airworthiness Standards, Normal Category Rotorcraft;
  8. U.S. 14 CFR, Chapter I, Subchapter C – Aircraft, Part 29, Airworthiness Standards, Transport Category Rotorcraft;
  9. Transport Canada Civil Aviation (TCCA) Canadian Aviation Regulations (CARs) and Standards, Part V – Airworthiness Chapter 523 – Normal, Utility, Aerobatic and Commuter Category Aeroplanes;
  10. TCCA CARs and Standards, Part V – Airworthiness Chapter 525 – Transport Category Airplanes;
  11. TCCA CARs and Standards, Part V – Airworthiness Chapter 527 – Normal Category Rotorcraft;
  12. TCCA CARs and Standards, Part V – Airworthiness Chapter 529 – Transport Category Rotorcraft;
  13. Federal Aviation Administration (FAA) Order 8900.1 – FAA Flight Standards Information Management System, Volume 4 – Air Navigation and Operational Authorizations, Chapter 1 – Air Navigation, Communications, and Surveillance, Section 5 – Safety Assurance System: Special Navigation Areas of Operation, paragraph 4-103c;
  14. TCCA’s Designated Airspace Handbook, TP1820E;
  15. TCCA CAR 605.16(1)(g).

    4       Discussion

    4.1      Background

    4.1.1     Northern Domestic Airspace

    4.1.1.1    Canadian Airspace is divided into two main regions – Southern Domestic Airspace (SDA), and NDA (Figure 1).  In the NDA, runway headings, tracks, etc., are given in degrees true, rather than magnetic. This is due to the diminishing horizontal component of the earth’s magnetic field in proximity to the magnetic North Pole and its effects on magnetic compass systems. 

    4.1.1.2     The NDA includes the Northern Control Area (NCA), the Arctic Control Area (ACA) and all the airspace below the base of these control areas down to the surface of the earth. The FAA designates Canada's NDA as an Area of Magnetic Unreliability (AMU). Although Canadian publications sometimes refer to it as the area of compass unreliability, they are the same. The NDA, NCA and ACA are depicted on all Canadian enroute charts and encompass the northernmost Canadian airspace. 

    4.1.2     Increased Alignment Times Due to Magnetic Variation and Convergence of the Meridians

    4.1.2.1    Conventional magnetic compasses sense magnetic direction by detecting the horizontal component of the earth's magnetic field. Since this horizontal component vanishes near the magnetic poles, magnetic compasses are highly unreliable and unusable in an area of approximately 1,000 NM from each magnetic pole. Within these areas, air navigation tasks are further complicated by very rapid changes in magnetic variation over small distances. For example, when flying between the Magnetic North Pole and the True North Pole, a heading of True North results in a magnetic heading of south (a magnetic variation of 180 degrees).

    Figure 1 – Northern and Southern Domestic Airspace

Figure 1 – Northern and Southern Domestic Airspace

Copyright Transport Canada

This figure outlines the area covered by the Southern Domestic Airspace for which the north-west boundary starts at the top of the western boundary of Yukon, extends east past Inuvik to 130 degrees W longitude, then comes straight south to 67 degrees latitude. It then goes east, linking the cities of Yellowknife, Churchill, Inuvik, and Iqaluit while including them. From Iqaluit, it goes north-east to 67 degrees latitude. All the Canadian airspace north of this boundary is the Northern Domestic Airspace.

4.1.2.2  The convergence of the meridians (i.e., lines of longitude) presents additional directional complications. When flying "great circle" courses at latitudes greater than 67 degrees, convergence of the meridians can create rapid changes in true headings and true courses with small changes in aircraft position. As a result, relatively small errors in determining the aircraft's actual position can produce very large errors in determining the proper heading to fly and maintain the assigned flight path. When even small errors occur, very large navigation errors can develop over extremely short distances. An extreme example of this phenomenon occurs at the earth's geographic North Pole. Flight in any direction from the exact pole is initially due south.

4.1.3    Navigation in the NDA

4.1.3.1   Navigating in the NDA presents several issues not found anywhere else in the world (other than near the South Pole). Because of these issues, an acceptable method of navigating within the NDA is through the use of long-range navigation systems referenced to True North, using Inertial and/or GNSS:

  1. Inertial Based Navigation Systems. All Inertial Navigation Systems (INS) / Inertial Reference Systems (IRS) / Inertial Reference Units (IRU) are capable of calculating True North referenced outputs independently from other aircraft systems.
  2. GNSS Systems. As of January 2017, according to Nav Canada’s Aeronautical Information Publication – AIP Canada (ICAO), the only global operational GNSS approved for use in Canada are the United States NAVSTAR Global Positioning System (GPS) and the Russian GLONASS. GNSS can output tracks referenced to degrees True, but generally do not provide any heading information. Operationally, a GNSS and an Automatic Direction Finder (ADF) can be used to determine aircraft heading. This heading can then be used to manually set a Directional Gyro, for example.

4.2     Airworthiness Considerations

4.2.1      The applicant is responsible for verifying that the installed navigation equipment and overall avionics architecture continues to provide its intended function while operating in NDA.  Certain CAF aircraft use a civil certification basis, while others use MIL-HDBK-516, or the aircraft design specification. The appropriate airworthiness certification basis needs to be identified to ensure that the correct means and methods of compliance are incorporated into the project objectives, safety assessment, test plans and flight manual amendments.

4.2.2       For aircraft designed and certified to civil airworthiness standards, as a minimum, the following Federal Aviation Regulation (FAR) or Canadian Aviation Standard Airworthiness Manual (AWM) requirements should be included:

  1. 1301 Function and Installation;
  2. 1309 System Safety; and
  3. 1501, 1583 and 1585 Flight Manual.

The certification basis should be carefully assessed to determine whether any additional airworthiness standards and requirements need to be addressed as a result of any specific design peculiarities.

4.2.3       For aircraft designed and certified to MIL-HDBK-516, the typical requirements should include:

  1. Section 4.5 – Operator’s and Maintenance Manual;
  2. Section 10 – Diagnostics Systems;
  3. Section 11 – Avionics; and
  4. Section 14 – System Safety.

4.2.4       Specific functional ground and flight test, system safety and FM/AOI requirements, criteria and guidance are identified in this advisory’s Annex A, Annex B and Annex C, respectively.  Fleets seeking airworthiness approval to operate in the NDA need to address these requirements as part of their airworthiness certification program.