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Latitude Limit Over Greenland? 747/757  
User currently offlineNjxc500 From United States of America, joined Dec 2007, 243 posts, RR: 0
Posted (5 years 10 months 3 weeks 2 days 10 hours ago) and read 5615 times:

I saw a chart in a photo in a magazine.....Anyway it was clear enough so I could read it, and it appeared as though there was a latitude limit for the 747 and 757 over greenland. It was a sectional chart of some sort, and I have never seen one of these, so I have no idea. However, it caught my attention, so I'm wondering if someone can enlighten me.

Thanks,
Nick

25 replies: All unread, showing first 25:
 
User currently offlineMax Q From United States of America, joined May 2001, 4556 posts, RR: 19
Reply 1, posted (5 years 10 months 3 weeks 2 days 8 hours ago) and read 5584 times:

Our limits for the 757 / 767 aircraft we operate are maximum latitudes of 87 Degrees North or South, regardless of which land mass we are over.

Don't know about the Queen of the skies, but would be curious !

[Edited 2008-11-13 21:55:24]


The best contribution to safety is a competent Pilot.
User currently offlineBassbonebobo From United States of America, joined Apr 2008, 66 posts, RR: 0
Reply 2, posted (5 years 10 months 3 weeks 2 days 7 hours ago) and read 5551 times:



Quoting Max Q (Reply 1):
Our limits for the 757 / 767 aircraft we operate are maximum latitudes of 87 Degrees North or South, regardless of which land mass we are over.

Interesting. Any ideas on what the reason behind this is? Is this an airline procedure or a limitation on the aircraft itself?



Rule #176. Any device that can crawl across the table on medium, does not need to be brought into the office.
User currently offlineVikkyvik From United States of America, joined Jul 2003, 10048 posts, RR: 26
Reply 3, posted (5 years 10 months 3 weeks 2 days 7 hours ago) and read 5542 times:
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Quoting Bassbonebobo (Reply 2):
Interesting. Any ideas on what the reason behind this is? Is this an airline procedure or a limitation on the aircraft itself?

Could it be due to magnetic field lines converging, and compasses being more inaccurate in turns and such up there? I don't think they use a compass as their primary means of navigation, but perhaps they need it as a backup?

Actually, that may not make sense, seeing as magnetic north is somewhere in the vicinity of 82-83 degrees latitude.



"Two and a Half Men" was filmed in front of a live ostrich.
User currently offlineMax Q From United States of America, joined May 2001, 4556 posts, RR: 19
Reply 4, posted (5 years 10 months 3 weeks 2 days 6 hours ago) and read 5526 times:

I am not sure if that is just our Airlines limit or Boeings.

I believe the 777 has a grid navigation system for the more northerly / southerly latitudes as magnetic headings become rather academic.

There may be some 75 / 6 operators that certified their aircraft for these 'extreme latitudes'



The best contribution to safety is a competent Pilot.
User currently offlineTristarSteve From Sweden, joined Nov 2005, 4016 posts, RR: 34
Reply 5, posted (5 years 10 months 3 weeks 2 days 3 hours ago) and read 5487 times:

I have seen the chart you talk about. On our B767 fleet there is a northern limit of operation. This actually affects operation between London and Calgary. Will try and find it for you. The B747 and B777 are not affected.

User currently offlineScooter01 From Norway, joined Nov 2006, 1204 posts, RR: 8
Reply 6, posted (5 years 10 months 3 weeks 2 days ago) and read 5444 times:
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This information might be of some help :
http://www.boeing.com/commercial/aer...ne/aero_16/polar_nav_by_model.html

Glad to oblige my  twocents  worth

Scooter01



"We all have a girl and her name is nostalgia" - Hemingway
User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2255 posts, RR: 15
Reply 7, posted (5 years 10 months 3 weeks 2 days ago) and read 5428 times:

I'm in a hurry at the moment but if I understand correctly , I've done polar flights and I believe the route over Greenland has to do with eng. failure driftdown alt which is too low for some parts of Greenland terrain. I apologize if I misunderstood...later

User currently offlineNjxc500 From United States of America, joined Dec 2007, 243 posts, RR: 0
Reply 8, posted (5 years 10 months 3 weeks 1 day 23 hours ago) and read 5418 times:

Interesting comments on this topic.... This "limit" was around the latitude of the arctic circle somewhere over greenland, and it was printed in magenta color. It specifically listed the limit for two aircraft, and I am hoping someone here can come up with the sectional, so everyone can see it. Maybe I'll buy the magazine I was flipping through, scan the picture and post it here.

Thanks for the interesting read. It is interesting to think of things like having to "rapidly change heading selector" as written in that article regarding crossing the poles.


User currently offlineTristarSteve From Sweden, joined Nov 2005, 4016 posts, RR: 34
Reply 9, posted (5 years 10 months 3 weeks 1 day 22 hours ago) and read 5398 times:

Our B757 and B767 are approved to operate up to 68N, plus an area over Greenland and another over Norway up to 75N. This is in the terms of the AOC.
This is a lower limit than Boeing promulgates per the post above, and I assume it has something to do with the equipment fitted to the aircraft.
Another problem is that the MSA over most of Greenland is above 10000ft, so this needs planning with one engine out driftdown.


User currently offlineMax Q From United States of America, joined May 2001, 4556 posts, RR: 19
Reply 10, posted (5 years 10 months 3 weeks 1 day 20 hours ago) and read 5351 times:

That was a very interesting link Scooter01, thanks for the information.


The best contribution to safety is a competent Pilot.
User currently offlineThrottleHold From South Africa, joined Jul 2006, 657 posts, RR: 1
Reply 11, posted (5 years 10 months 3 weeks 1 day 2 hours ago) and read 5178 times:

Also, above a certain Latitude (can't remember the exact fugure) there is a requirement to carry extra polar survival equipment.

User currently offlineTristarSteve From Sweden, joined Nov 2005, 4016 posts, RR: 34
Reply 12, posted (5 years 10 months 3 weeks 1 day 2 hours ago) and read 5172 times:



Quoting ThrottleHold (Reply 11):
above a certain Latitude (can't remember the exact fugure) there is a requirement to carry extra polar survival equipment.

It is above 60N in N America. However we have an exemption if an ETOPS aircraft is flying within 600nm of a diversion airport, so we use this and don't carry it.


User currently offlineAAH732UAL From , joined Dec 1969, posts, RR:
Reply 13, posted (5 years 10 months 3 weeks 21 hours ago) and read 5109 times:

IIRC accroing to Honeywell and Boeing above 70 degrees North Latitude, the IRUs may take up to 15 minutes to fully align.

User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 14, posted (5 years 10 months 3 weeks 21 hours ago) and read 5088 times:



Quoting AAH732UAL (Reply 13):
IIRC accroing to Honeywell and Boeing above 70 degrees North Latitude, the IRUs may take up to 15 minutes to fully align.

That doesn't seem so bad...they take 10 minutes to align at normal latitudes.

Tom.


User currently offlineAAH732UAL From , joined Dec 1969, posts, RR:
Reply 15, posted (5 years 10 months 3 weeks 20 hours ago) and read 5080 times:



Quoting Tdscanuck (Reply 14):

Exactly, I guess they just make note of it to help crews time manage better. I would think the ADIRU on the 777 is a lot faster if they decide to do a full re-align and not just update it with GPS.


User currently offlineNjxc500 From United States of America, joined Dec 2007, 243 posts, RR: 0
Reply 16, posted (5 years 10 months 3 weeks 18 hours ago) and read 5045 times:

I have found a flight safety publication from AA that might explain this.

http://www.fsinfo.org/FSI-journals/4q_2000.pdf

It speaks extensively about the limitations of emergency descents over greenland with masks deployed. Never thought about it, but with hundreds of passengers to supply with O2, they must have time limits. It specifically points out the need for supplemental O2 bottles for 10% of passengers.

I am still working on finding the chart that showed this note....Hopefully soon.

Nick

P.S. Ironically this also contains research on fuel temperatures in the arctic on the T7....


User currently offlineAAH732UAL From , joined Dec 1969, posts, RR:
Reply 17, posted (5 years 10 months 3 weeks 14 hours ago) and read 4975 times:



Quoting Njxc500 (Reply 16):

Great link..... sorta sad that they had all the A300 rudder reports 1 year before the crash.


User currently offlineNjxc500 From United States of America, joined Dec 2007, 243 posts, RR: 0
Reply 18, posted (5 years 10 months 2 weeks 6 days ago) and read 4754 times:

This is email correspondence with the author of the article, Rand Peck.

The chart is a "company" specific, "North Atlantic/Canada Orientation Chart." Using this chart, we highlight our oceanic course, called a track, using lat/long coordinates. During the day, a "track message" is published, defining the tracks by lat/long and identifying them by letter. ie the Alpha track, Bravo track etc... This is where we receive our information to "build" our chart. We also mark our track entry/exit coordinates and our ETOPS points. ETOPS is an acronym for Extended range Twin engine Operational Performance Standards. ETOPS defines by time, our oceanic or remote area flight capabilities on two engines. In other words, we must always be within a specified time frame, from a suitable alternate airport on one engine plus other considerations. I suspect that you understand all this though. Other information, concerning navigational and altimeter accuracy are recorded here too. Although we're using Flight Management Computers and LNAV in our 757, this chart supplies us with a visual reference, to just where we are out here. When we complete our flight, this chart and our flight plan are packaged up and sent somewhere, in the event that questions arise in the future. You mentioned a specific detail though Nick; let me know what it is and perhaps I can help.

Yes, I enjoyed the article very much. Thank you for contacting me, it is very much appreciated, and it's always a good day when you can have a good flying discussion. Here's the question: There is a note on the chart pictured that states a latitude limit for (I believe) the 747 and 757 over Greenland. The map looks a lot like a sectional, so I'm not sure where to find a copy. The note was in magenta. We are discussing it on Airliners.net, in the tech/ops forum, under 757/747 latitude limit. The current consensus is that above a certain latitude, the terrain is too high to allow an emergency descent to below 14,000 feet. But why the specific note about two types? I guess maybe if it's company specific. And the masks are an option, but on these two types, is there a severe limitation on the amount of oxygen on board? Also, I found an American Airlines publication that stated some new option of carrying enough bottled oxygen for 10% of passengers. All of this was specific to crossing Greenland, and no one really seems to realize crossing that country is so difficult.


You're correct Nick, it's a passenger oxygen requirement, due to the fact that we can't descend below 10,000 feet in this mountainous terrain. The 747-400 and the 757 use individual oxygen generators which produce sufficient "passenger" oxygen to descend from 40,000+ feet to 10,000 feet at a constant rate. In other words, for an emergency rapid descent. But seeing as though we can't get down to 10,000 feet here, we're required to avoid it. You'll note though that our 747-200's and A-330's aren't affected by this restriction. That's because our 747-200's are freighters and carry no passengers and the 330 carries sufficient oxygen. I've flown 320's, but know nothing about 330's and their performance specs. I don't know how they satisfy this requirement, but further inspection of the chart legend, reveals that they do have a time restriction above FL250.


A point of discussion though. If we were ferrying a 757, with no passengers (I'm not sure about flight attendants, I'd have to check our MEL and with dispatch if this actually arose) we could fly north of 68 degrees. The pilot oxygen system is completely separate from the passenger system. Ours is supplied under pressure from a bottle with significant reserves for the captain, FO, and observers seat. We'd have enough oxygen to fly above 14,000 for a sufficient period of time. I "suspect" that this is true for a -400 too.


Interesting answer, we were on the right track.

Nick


User currently offlineHotelmode From United Kingdom, joined Jan 2007, 460 posts, RR: 1
Reply 19, posted (5 years 10 months 2 weeks 5 days 2 hours ago) and read 4530 times:

Quoting Njxc500 (Reply 18):
The 747-400 and the 757 use individual oxygen generators

Hate to correct Rand (love his articles) but the 747-400 has oxygen cylinders not generators and has no latitude/high ground restriction. We wouldnt get to HKG over the high ground in mongolia if it did. I seem to remember the only restriction is 87 degrees north as per 777. I've been to nearly 80 on occasion.

[Edited 2008-11-18 04:03:42]

User currently offlineTristarSteve From Sweden, joined Nov 2005, 4016 posts, RR: 34
Reply 20, posted (5 years 10 months 2 weeks 5 days ago) and read 4502 times:



Quoting Hotelmode (Reply 19):
747-400 has oxygen cylinders not generators

Do all B744 have cylinders?
On the B777 it is an option. I have seen some with cylinders and some with generators.


User currently offlineNjxc500 From United States of America, joined Dec 2007, 243 posts, RR: 0
Reply 21, posted (5 years 10 months 2 weeks 4 days 16 hours ago) and read 4409 times:

I did see the chart he speaks of, and the 747 is listed as restricted, so there must be something to this, but it's obviously airline and aircraft specific now.

Nick


User currently offlineHotelmode From United Kingdom, joined Jan 2007, 460 posts, RR: 1
Reply 22, posted (5 years 10 months 2 weeks 2 days 6 hours ago) and read 4286 times:



Quoting TristarSteve (Reply 20):
Do all B744 have cylinders?

Ours do and Qantas definately do! I cant see why you wouldnt want them even as a North american carrier if they prevent you overflying large chunks of Greenland. Any aircraft not fitted would be useless for resale to any European/Asian carrier.


User currently offlineAirCatalonia From Spain, joined Nov 2007, 560 posts, RR: 0
Reply 23, posted (5 years 10 months 2 weeks 2 days ago) and read 4242 times:

Doesn't the famous SIN-JFK route fly directly over the north pole?

User currently offlineViscount724 From Switzerland, joined Oct 2006, 25461 posts, RR: 22
Reply 24, posted (5 years 10 months 2 weeks 1 day 16 hours ago) and read 4187 times:



Quoting AirCatalonia (Reply 23):
Doesn't the famous SIN-JFK route fly directly over the north pole?

It's SIN-EWR, not JFK. Eastbound I believe that flight normally uses the traidtional North Pacific routing close to Japan and over Alaska and Canada to benefit from usual tailwinds. In the other direction they may use the polar route passing fairly close to the North Pole but they also often use a longer transatlantic routing that crosses Europe when winds make that route faster.


User currently offlineBuckFifty From Canada, joined Oct 2001, 1316 posts, RR: 20
Reply 25, posted (5 years 10 months 2 weeks 1 day 11 hours ago) and read 4154 times:

On the 346 I used to fly, there is a button which switches our navigation from magnetic to a true grid. Without such a device, we could not do polar ops, simply because everything above an average latitude of 82N is denoted in true bearings.

For example, if you have a polar chart out, check out the VOR at Thule in Greenland. You will notice that it transmits it's radial information in true, not magnetic. This applies to all the tracks also.


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