posted on Mar, 26 2008 @ 10:11 AM
Originally posted by Pilot
OZ, I was asking Weed about the altitude thingy...
OK, Pilot...first time I saw your question about how many miles a jet travels on its climb to altitude. There are variables, not the least of which
is the airplane's weight from Take-Off. Also, there can be ATC restrictions that require intermediate level-offs, say for conflicting traffic.
But, for the purposes of an example, let's assume an unimpeded climb from a sea-level airport to 35,000 cruise. Let's also assume an average of
2,000 fpm vertical speed, it will be greater at lower altitudes, and somewhat less at the higher altitudes. I won't bother to factor in the few
minutes spent just above 10,000 feet when we accelerate from the mandatory 250K speed limit to the 300-320K climb speed.
SO, a good average time to TOC (top of climb) is around 20 minutes. At a groundspeed of 450K you travel 7.5 miles in one minute (talking Nautical
miles here...one Nautical mile is 6,060 feet, compared to Statute mile, 5,280). Now, 7.5 miles per minute times 20 minutes...150 miles.
Of course, groundspeed isn't 450K throughout the climb, so I've exagerrated a bit, if that helps. BTW, for comparison, a typical glide ratio for
jets in descent, at flight idle power, is 3:1...that is, 3 miles downrange for every 1,000 feet. SO, from 35,000 we would expect to begin an idle
descent from about 100 miles out. This would be the most efficient way to do it, but unfortunately it doesn't always work that way in the real
world, much to the dismay of the airlines as they see oil and fuel prices go through the roof.
Hope this helps.