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.