I am looking at your post and in front of me I also have the Alps Driftdown Orientation Chart and see your problem. I also see much higher grid MORA's than you qoute like 18,500 near ROCCA. As for the company pushing the corner on the 4 minute rule. I don't understand why. All I can reason is that they do not want to carry the extra oxygen? I am not familiar with your aiplane but would disagree with anyone who wanted to maximize descent times in an emergency situation such as cabin decompression.
You also mentioned the driftdown curve. What is your reference to that? I do not see a relationship between driftdown and decompression. They are two very different scenarios.
I spend alot of time between 35,000 and 41,000 and just recently got into this type of discussion while crossing some very high terrain NW of YAK (Yakutat Alaska) grid MORA of 21,900.
I am sorry also if I am a little vague on Jar Ops1+ but these are new to me and I am still trying to unravel them.
[This message has been edited by UP2ZSKY (edited 25 November 2000).]