Operating North of 72N

Moderators: Kai, Rick, Lance Murray, Mr. Gadget

User avatar
dgger
3 Diamonds Member
3 Diamonds Member
FIRST NAME: Peter
Aircraft: DA42NG
Registration: DGGER

Posts: 65
Joined: Sun Feb 21, 2016 11:00 pm
Has thanked: 9 times
Been thanked: 7 times

Operating North of 72N

Postby dgger » Fri Mar 17, 2017 4:31 pm

Fellow Aviators,

I am struggling to make sense of a Garmin limitation. If I read things right, the Garmin AHRS should be considered INOP in some parts of the world such as north of 72N.

Now, what exactly are the consequences of this limitation? The way I read things (for an EASA registered AC) this would rule out IFR (two attitude indicators) and even NVFR (missing heading indicator) in these parts of the world. Is that indeed true?

And last but not least: Do the Garmin indications indeed become unreliable and/or deviate from reality? And what is the technical reason for this limitation?

Can anyone (of you Canadians, maybe ;) ) shed some light on this one?
User avatar
ThomasD
3 Diamonds Member
3 Diamonds Member
FIRST NAME: ThomasD
Aircraft: DA40
Registration: N215DS
Airport: EGBJ

Posts: 122
Joined: Thu Jan 20, 2011 9:53 pm
Been thanked: 5 times

Re: Operating North of 72N

Postby ThomasD » Fri Mar 17, 2017 5:09 pm

I was involved in a flight to the North Pole in a Garmin-equipped Cessna 210 (I was filming it).

FYI, this far north the consequences that I remember are:
1) the map stops - it simply ends and the screen is blank
2) course directions become highly curved - we were communicating with the crew and they were going the wrong direction. The HSI stayed in place but sure of its reliability
3) mag compass is not much use as mag north is so far from geographic north and the difference changes very quickly

The crew had to rely on a hand-held trekking GPS which didn't care how far north it was
User avatar
rwtucker
5 Diamonds Member
5 Diamonds Member
FIRST NAME: Robert
Aircraft: DA40
Registration: N831BA
Airport: KEUL KMYL KBOI

Posts: 1094
Joined: Thu Feb 21, 2013 11:24 pm
Has thanked: 53 times
Been thanked: 75 times

Re: Operating North of 72N

Postby rwtucker » Sat Mar 18, 2017 2:35 pm

Thomas - Your 210 trip to the North Pole sounds like a lot of fun. If you get time, I wold love to hear more about it and some of the navigational challenges.
User avatar
dgger
3 Diamonds Member
3 Diamonds Member
FIRST NAME: Peter
Aircraft: DA42NG
Registration: DGGER

Posts: 65
Joined: Sun Feb 21, 2016 11:00 pm
Has thanked: 9 times
Been thanked: 7 times

Re: Operating North of 72N

Postby dgger » Sun Mar 19, 2017 2:44 pm

Thomas,

That sounds like you did an awesome flight!

Do you know what causes the Garmin to go blank and why these limitations exist? Do you remember what you guys had used for backup? I cannot quite get my head around why Garmin, but apparently not other manufacturers would have this limitation.
User avatar
ThomasD
3 Diamonds Member
3 Diamonds Member
FIRST NAME: ThomasD
Aircraft: DA40
Registration: N215DS
Airport: EGBJ

Posts: 122
Joined: Thu Jan 20, 2011 9:53 pm
Been thanked: 5 times

Re: Operating North of 72N

Postby ThomasD » Sun Mar 19, 2017 3:09 pm

It was 'interesting', to say the least ! I was not doing the flying, actually filming the trip.
I hope to have a film trailer done within a month or so - I will post the link when done.

I don't know why the G1000 is not good for north of 70 degrees - maybe inability or cost to test the GPS accuracy that far north? Maybe the G1000 GPS models of the earth become less accurate as the earth is an oblate spheroid (not a perfect sphere)? And would require specific programming which is not worth doing on the G1000 ?
I think that someone would have to ask Garmin why.
User avatar
krellis
3 Diamonds Member
3 Diamonds Member
FIRST NAME: Keith
Aircraft: DA20-AI
Registration: N853DF
Airport: GA04

Posts: 164
Joined: Fri Apr 29, 2011 10:42 am
Has thanked: 1 time
Been thanked: 12 times

Re: Operating North of 72N

Postby krellis » Mon Mar 20, 2017 2:05 pm

The B-737 I fly is limited to 82N/82S - so I expect it's a testing and certification limitation.

The C-17 reportedly had issues when going south of the equator early on in it's history. Apparently, it had never been tested and the first flight south of the equator reportedly caused a reboot of the entire PFD/MFD system. Don't know if this really happened or was just a tale being passed around the squadrons.
User avatar
rwtucker
5 Diamonds Member
5 Diamonds Member
FIRST NAME: Robert
Aircraft: DA40
Registration: N831BA
Airport: KEUL KMYL KBOI

Posts: 1094
Joined: Thu Feb 21, 2013 11:24 pm
Has thanked: 53 times
Been thanked: 75 times

Re: Operating North of 72N

Postby rwtucker » Mon Mar 20, 2017 4:38 pm

User avatar
dgger
3 Diamonds Member
3 Diamonds Member
FIRST NAME: Peter
Aircraft: DA42NG
Registration: DGGER

Posts: 65
Joined: Sun Feb 21, 2016 11:00 pm
Has thanked: 9 times
Been thanked: 7 times

Re: Operating North of 72N

Postby dgger » Mon Mar 20, 2017 10:42 pm

Keith, Robert,

Thanks for the input. I suspect, the GPS itself would not be the problem, but the AHRS (or the INS in the 737 case). I would not find that hard to imaging given the weakening centrifual force when approaching the axis.

This is also in line with the limitation given by the POH.

I am off to do some reasearch, then.
User avatar
ThomasD
3 Diamonds Member
3 Diamonds Member
FIRST NAME: ThomasD
Aircraft: DA40
Registration: N215DS
Airport: EGBJ

Posts: 122
Joined: Thu Jan 20, 2011 9:53 pm
Been thanked: 5 times

Re: Operating North of 72N

Postby ThomasD » Mon Mar 20, 2017 10:53 pm

Yes of course, the AHRS and in particularly the magnetometer could have a hard time due to magnetic variation being so far off geographic north, and the testing required to ensure this was correct in that area, which is relatively little used by G1000 equipped small airplanes (may be different on a turbine with G1000 / G2000 ?)
User avatar
Lou
3 Diamonds Member
3 Diamonds Member
FIRST NAME: Louis
Aircraft: DA40
Registration: CGXLO
Airport: CZVL

Posts: 88
Joined: Sat Nov 21, 2015 1:39 pm
Has thanked: 4 times
Been thanked: 7 times

Re: Operating North of 72N

Postby Lou » Tue Mar 21, 2017 1:45 am

I can throw in my limited C$ .02 :D ( That's now $ .015 usd). I thought the G1000 limitation esssentially traces a similar boundary to the Northern Domestic Airspace. Ie not above 65N between 75W and 120W, otherwise not above 70N. This is the area around the magnetic North Pole, but does not include the Western arctic. Basically a semi-circle around magnetic north. Magnetic compasses are not reliable in the NDA and all runway and VOR headings, for instance, are given in degrees true. ( look in Foreflight at YBK, for example) It's also all standard pressure (in cruise - different rules apply for approaches) Compasses are less reliable in part because the vertical componet of the magnetic field gets more and more pronounced as you approach the pole, Ie a compass wants to point down, and also the needle gets very sensitive.

I am not entirely clear how they navigate in the NDA where there are no radio aids. I should ask my buddy who has spent his career in the north. I expect that GPS that is not linked to an AHRS is fine, since GPS is very reliable in the north because I understand more satellites are visible.

Anyway, compasses don't work and tha AHRS is probably just as unreliable. That's what I would guess.

(All the magnetic variations are charted until 77N, at which point there is a full degree of variation every 6 miles or so, so I don't think that is the issue. )

Return to “Diamond Gadgets & Extras”

Who is online

Users browsing this forum: No registered users and 0 guests