Define the boundary of Area Magnetic Unreliability (AMU) Airspace

[worldwide]

Is anyone familiar with a defined boundary for the Northern Hemisphere AMU?

FSIMS redirects to the Canadian AIPs, Canadian AIPs are vague, we are NOT approved for Polar (78N) and don't have Ops Spec B040 (AMU Ops). How far north can I operate?

 

[TundraT]

Ac 91-70a

I don't know if this will answer your question, but check out page 51 of the AC.

http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC 91-70A.pdf

 

[propilot]

4-103 AMUs. Two large areas of en route operation have unique features which significantly complicate air navigation. These two areas are centered around Earth’s magnetic poles.

A. Concept. Conventional magnetic compasses sense magnetic direction by detecting the horizontal component of Earth’s magnetic field. Since this horizontal component vanishes near the magnetic poles, magnetic compasses are highly unreliable and unusable in an area 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).

B. Convergence of the Meridians. Since these two major AMUs also occur near Earth’s geographic poles, the convergence of the meridians also 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 to maintain the assigned flightpath. When even small errors occur, very large navigation errors can develop over extremely short distances. An extreme example of this phenomenon occurs at Earth’s geographic North Pole. Flight in any direction from the exact pole is initially due South (that is, the direction to Russia or the United States is South).

C. Special Equipment, Techniques, and/or Procedures. Special navigation equipment, techniques, and/or procedures are critical to operate safely in polar areas, including the two AMUs. Operations based solely on magnetic references within AMUs are unsafe, unacceptable, and must not be approved. Operations within these areas can only be conducted safely if the primary heading reference is derived from sources other than magnetic.

1) All INS/IRS/IRU are capable of calculating true North independently from other aircraft systems. INS/IRS/IRU can be approved and safely used for operations in AMUs and polar areas provided the following conditions are met:

a) The INS is certified as Airworthy for the highest latitude authorized for these operations.

b) Ground alignment of the INS/IRS/IRU is restricted to those airports where satisfactory alignment has been demonstrated or otherwise approved.

c) The operator’s training programs and crew procedures provide acceptable techniques and methods for the following:

· Approaches and departures using appropriate heading references other than magnetic.
· The use of ground-based NAVAIDs, which are oriented to appropriate directional references other than magnetic.

NOTE: It is the FAA’s direction and guidance that inspectors must not approve operations in polar areas and/or AMUs without the participation and concurrence of one of the agency’s NextGen oceanic specialists.
2) There is a wide variety of other methods, systems, techniques, and procedures that can be used for navigation in AMUs and polar areas. However, due to the variety of means and the complexity of air navigation in these areas, specific direction and guidance for these other means of navigation are not provided in this order.

NOTE: It is the FAA’s direction and guidance that inspectors must obtain assistance from one of the agency’s NextGen oceanic specialists in evaluating and approving or denying an operator’s request to use systems, techniques, or procedures that are not discussed in this section.
D. Boundaries of the AMU.

1) For the northern hemisphere, the Canadian AIP establishes the basic boundaries for the AMU. Canadian Air Navigation Order, current edition, states that no person may operate an aircraft in instrument flight rules (IFR) flight within Canadian northern domestic airspace unless it is equipped with a means of establishing direction that is not dependent on a magnetic source. The special equipment, training, and procedures discussed in this paragraph are required for all operations into the area of northern domestic airspace. The boundaries of this area are shown in Figure 4-3, Canadian Domestic Airspace. This area is also outlined on Canadian en route charts. For the purposes of this paragraph, northern domestic airspace is considered to extend from ground level to infinity.

2) For the southern hemisphere, any operation south of lat. 65°00'00" S is considered to be within the AMU. Any proposal to operate within the AMU in the southern hemisphere must be reviewed and concurred with by AFS-400 before approval.

E. Approvals. All approvals for operations into AMUs are granted by issuing OpSpec B040, and by adding that area of en route operation to the standard OpSpec B050. A checklist for operations in AMUs is available in the guidance subsystem in association with OpSpec B040.

Figure 4-3. Canadian Domestic Airspace

 

[worldwide]

This was all very helpful, thank you.

 

[CaptSeth]

Did I log onto pprune by mistake?