njxc500
Posts: 194
Joined: Mon Dec 24, 2007 6:47 pm

Latitude Limit Over Greenland? 747/757

Fri Nov 14, 2008 4:35 am

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
 
Max Q
Posts: 5644
Joined: Wed May 09, 2001 12:40 pm

RE: Latitude Limit Over Greenland? 747/757

Fri Nov 14, 2008 5:53 am

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.
 
bassbonebobo
Posts: 52
Joined: Sun Apr 06, 2008 3:09 am

RE: Latitude Limit Over Greenland? 747/757

Fri Nov 14, 2008 6:54 am



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.
 
vikkyvik
Posts: 11855
Joined: Thu Jul 31, 2003 1:58 pm

RE: Latitude Limit Over Greenland? 747/757

Fri Nov 14, 2008 7:26 am



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.
I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".
 
Max Q
Posts: 5644
Joined: Wed May 09, 2001 12:40 pm

RE: Latitude Limit Over Greenland? 747/757

Fri Nov 14, 2008 7:56 am

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.
 
Tristarsteve
Posts: 3365
Joined: Tue Nov 22, 2005 11:04 pm

RE: Latitude Limit Over Greenland? 747/757

Fri Nov 14, 2008 11:19 am

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 avatar
Scooter01
Posts: 1183
Joined: Tue Nov 28, 2006 11:06 pm

RE: Latitude Limit Over Greenland? 747/757

Fri Nov 14, 2008 1:59 pm

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
There is always a good reason to watch airplanes
 
CosmicCruiser
Posts: 2049
Joined: Tue Feb 22, 2005 3:01 am

RE: Latitude Limit Over Greenland? 747/757

Fri Nov 14, 2008 2:29 pm

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
 
njxc500
Posts: 194
Joined: Mon Dec 24, 2007 6:47 pm

RE: Latitude Limit Over Greenland? 747/757

Fri Nov 14, 2008 2:55 pm

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.
 
Tristarsteve
Posts: 3365
Joined: Tue Nov 22, 2005 11:04 pm

RE: Latitude Limit Over Greenland? 747/757

Fri Nov 14, 2008 3:54 pm

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.
 
Max Q
Posts: 5644
Joined: Wed May 09, 2001 12:40 pm

RE: Latitude Limit Over Greenland? 747/757

Fri Nov 14, 2008 6:19 pm

That was a very interesting link Scooter01, thanks for the information.
The best contribution to safety is a competent Pilot.
 
User avatar
ThrottleHold
Posts: 545
Joined: Tue Jul 18, 2006 11:00 pm

RE: Latitude Limit Over Greenland? 747/757

Sat Nov 15, 2008 12:31 pm

Also, above a certain Latitude (can't remember the exact fugure) there is a requirement to carry extra polar survival equipment.
 
Tristarsteve
Posts: 3365
Joined: Tue Nov 22, 2005 11:04 pm

RE: Latitude Limit Over Greenland? 747/757

Sat Nov 15, 2008 12:46 pm



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.
 
AAH732UAL
Posts: 242
Joined: Sun Mar 30, 2008 9:41 pm

RE: Latitude Limit Over Greenland? 747/757

Sat Nov 15, 2008 4:54 pm

IIRC accroing to Honeywell and Boeing above 70 degrees North Latitude, the IRUs may take up to 15 minutes to fully align.
DME/DME RNP0.3 NA -Escalators don't break---- they just become stairs!
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: Latitude Limit Over Greenland? 747/757

Sat Nov 15, 2008 5:53 pm



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.
 
AAH732UAL
Posts: 242
Joined: Sun Mar 30, 2008 9:41 pm

RE: Latitude Limit Over Greenland? 747/757

Sat Nov 15, 2008 6:16 pm



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.
DME/DME RNP0.3 NA -Escalators don't break---- they just become stairs!
 
njxc500
Posts: 194
Joined: Mon Dec 24, 2007 6:47 pm

RE: Latitude Limit Over Greenland? 747/757

Sat Nov 15, 2008 8:43 pm

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....
 
AAH732UAL
Posts: 242
Joined: Sun Mar 30, 2008 9:41 pm

RE: Latitude Limit Over Greenland? 747/757

Sun Nov 16, 2008 12:24 am



Quoting Njxc500 (Reply 16):

Great link..... sorta sad that they had all the A300 rudder reports 1 year before the crash.
DME/DME RNP0.3 NA -Escalators don't break---- they just become stairs!
 
njxc500
Posts: 194
Joined: Mon Dec 24, 2007 6:47 pm

RE: Latitude Limit Over Greenland? 747/757

Mon Nov 17, 2008 2:05 pm

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
 
hotelmode
Posts: 179
Joined: Tue Jan 23, 2007 6:31 am

RE: Latitude Limit Over Greenland? 747/757

Tue Nov 18, 2008 12:01 pm

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]
 
Tristarsteve
Posts: 3365
Joined: Tue Nov 22, 2005 11:04 pm

RE: Latitude Limit Over Greenland? 747/757

Tue Nov 18, 2008 2:11 pm



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.
 
njxc500
Posts: 194
Joined: Mon Dec 24, 2007 6:47 pm

RE: Latitude Limit Over Greenland? 747/757

Tue Nov 18, 2008 10:44 pm

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
 
hotelmode
Posts: 179
Joined: Tue Jan 23, 2007 6:31 am

RE: Latitude Limit Over Greenland? 747/757

Fri Nov 21, 2008 8:42 am



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.
 
aircatalonia
Posts: 522
Joined: Wed Nov 28, 2007 12:50 pm

RE: Latitude Limit Over Greenland? 747/757

Fri Nov 21, 2008 2:07 pm

Doesn't the famous SIN-JFK route fly directly over the north pole?
 
Viscount724
Posts: 19046
Joined: Thu Oct 12, 2006 7:32 pm

RE: Latitude Limit Over Greenland? 747/757

Fri Nov 21, 2008 10:40 pm



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.
 
buckfifty
Posts: 1278
Joined: Tue Oct 16, 2001 4:05 pm

RE: Latitude Limit Over Greenland? 747/757

Sat Nov 22, 2008 2:59 am

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.

Who is online

Users browsing this forum: Starlionblue and 15 guests