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boofhead
21st Aug 2015, 18:46
Some of the charts show the GPS approach uses True Course. They do not show the equivalent Mag course. The US method shows both Mag and Grid. In the US the Garmin uses Mag and is seamless, but what happens when flying the approach in high latitudes in Canada? Do I see any difference? Will the Garmin switch to true course? How will I know?

How do I find the areas of Canadian MNPS?

ahramin
21st Aug 2015, 22:57
What approach are you looking at? All approaches in Canadian Southern Domestic Airspace, including GPS approaches, show directions relative to Magnetic North regardless of lattitude. In Northern Domestic Airspace, which has no major airports, all directions are in True regardless of type of approach GPS or otherwise. No references to magnetic North and you would need to set your DG to true heading and your Garmin to true. I don't know of any navigation system that automatically switches from Mag to True without pilot input. The Garmin has three user selectable modes: True, Magnetic Auto, and Magnetic User.

High lattitudes is not a problem for magnetic compass systems, being close to the magnetic North pole is. This is why high lattitude plates outside of the area of compass unreliability (in otherwords not close to the Magnetic North Pole) still use Magnetic North. High lattitudes are a problem with both magnetic and true headings rapidly changing as you follow a straight line, which is why they use grid reference.

27/09
21st Aug 2015, 23:07
Isn't there a limitation on how far north (or south) you can use some GPS units?

aterpster
21st Aug 2015, 23:35
boofhead:

Some of the charts show the GPS approach uses True Course. They do not show the equivalent Mag course. The US method shows both Mag and Grid. In the US the Garmin uses Mag and is seamless, but what happens when flying the approach in high latitudes in Canada? Do I see any difference? Will the Garmin switch to true course? How will I know?

Those procedures are stored in the nav database in true course.

boofhead
22nd Aug 2015, 00:42
Is the magnetic unreliability charted? Where could I find that?

underfire
22nd Aug 2015, 01:09
At Deadhorse we used grid north..

found more recent mapping
http://i59.tinypic.com/2igkrra.jpg

Sleepybhudda
22nd Aug 2015, 10:51
From our experience in Antarctica, AHRS have limitations on Latitudes but GPS or GNSS units don't.


Which Garmin units are people referring to? GNS 430/530 or G1000?


SB

aterpster
22nd Aug 2015, 15:19
This was as far north as I could find:

http://i201.photobucket.com/albums/aa214/aterpster/CYLT-1_zpsyyc0vrbg.jpg

http://i201.photobucket.com/albums/aa214/aterpster/CYLT-2_zpsxbyvpkth.jpg

http://i201.photobucket.com/albums/aa214/aterpster/CYLT-3_zpsjgytayha.jpg

evansb
22nd Aug 2015, 20:10
Where to find the reference? The Canadian AIM publication, IFR charts and FAA Advisory Circular 120-42B, and FAA Advisory Circular 91.70A.

The FAA designates Canada's NCA and Arctic Control Area (ACA) as AMUs. Although Canadian publications sometimes refer to it as the area of compass unreliability, they are the same. The magnetic North Pole is at approximately 75N 100W and is slowly moving as it circles the true pole every 960 years. This is why we see current navigation charts occasionally changing an instrument landing system (ILS) course by 1.

When operating in the AMU, move the HDG REF switch to TRUE when the Canada HI 4 chart defines the course with a T. Add two additional items to the master flight plan checklist: TRUE HDG adjacent to the first true heading leg and MAG HDG at the end of the AMU. This will serve as a reminder to return to a normal heading reference. The primary reason for selecting TRUE HDG in the NCA and ACA is to provide a more realistic navigation display (ND) heading presentation, thus avoiding rapidly changing heading indications. This will help with radar vectors in TRUE and comply with Canadian Air Regulations.

http://i1047.photobucket.com/albums/b477/gumpjr_bucket/canadian_control_areas_tc_aim_figure_2.3.png


Note the comments in parenthesis on the chart below:
http://i1047.photobucket.com/albums/b477/gumpjr_bucket/arctic_radio_vhf_jeppesen_ap.png

The worst magnetic compass performance is probably in the center of the Northern Control Area, home to the magnetic North Pole. This position creates a notch in the circle of magnetic unreliability, often called a "key hole." Charts should be checked for the presence of a "T" denoting the use of True Heading instead of Magnetic. Some aircraft automatically switch to True based on airway designation or latitude. The G450, for example, automatically switches above N73 or S60 latitude. More about this: G450 Procedures & Techniques / FMS: True/Magnetic Selection.

evansb
23rd Aug 2015, 05:12
Ultimately, if you are planning on flying in Canada's Arctic Airspace, contact NavCanda.ca

Additional map and PDF link you may find helpful:
http://i1047.photobucket.com/albums/b477/gumpjr_bucket/RVSM%20Canada.gif

http://www.icao.int/SAM/Documents/2003/RVSMII/D-MacKeigan-Can%20Imp%20Exp%20Plans.pdf

JammedStab
24th Aug 2015, 03:32
I don't know of any navigation system that automatically switches from Mag to True without pilot input.

The 747-400 and 777 both switch over to true automatically at the appropriate North or south latitude.

Intruder
24th Aug 2015, 03:56
From the 744 FCOM:
High Latitude Operations
The heading reference for PFDs, NDs, and RMI (if installed) changes to true north at 82N (or north of 70N between 80W and 130W) or at 82S (or south of 60S between 120E and 160E).
At latitudes between 82N (or south of 70N between 80W and 130W) and 82S (or north of 60S between 120E and 160E), the FMC and IRU reference is determined by Heading Reference switch position. Outside this region, the FMC and IRUs reference true north regardless of Heading Reference switch position.
Automatic switching to a true north reference annunciates by a white box around the word TRU on the ND. A TRUE heading reference can be selected with the Heading Reference switch inside or outside high latitudes. The ND displays a green box around the word MAG to annunciate the change back to magnetic reference. If the heading reference is TRU in the descent phase, the ND displays a flashing amber box around the word TRU.

A Squared
24th Aug 2015, 04:12
At Deadhorse we used grid north..

WHy? Flown in and out of Deadhorse a bunch, including crewing an airplane based there, and never felt much of a need to use grid azimuths. WHiskey compasses and slaved DG's all seemed to work just fine and match the published mag courses.

boofhead
24th Aug 2015, 22:08
That was a lot of help, thanks all.

Intruder
24th Aug 2015, 23:40
Is the magnetic unreliability charted? Where could I find that?
The Jeppesen Atlantic Polar High Altitude en route Chart AT(HI)5 defines the
airspace.

Isn't there a limitation on how far north (or south) you can use some GPS units?
From our FOM: GPS updating may be available up to a latitude of 88 N. SATCOM may be available up to a latitude of 84 N.

JammedStab
25th Aug 2015, 04:56
Isn't there a limitation on how far north (or south) you can use some GPS units?

Could be, I seem to remember reading that when at the far north latitudes, you might be able to catch a signal from orbiting satellites on the other side of the pole. I don't remember seeing any restrictions based on latitude in general GPS info.

I have used a GPS, aftermarket installation at the exact north pole and there was no difficulty. I have not heard anybody mention difficulties at the south pole which is a much busier location with a frequently used airstrip during the summer.