reply to post by Aqualung2012
Oh, dear.......first, your quote:
if that bit about 75 to 100 miles was even a coherant thought, you would have an easy explaination as to why (living less than 20 miles from
ohare) I see them a l l t h e t i m e.
Now......the contrails you see are NOT....I repeat, NOT local arrivals or departures, if you are near the airport you mention...not to THAT
You are seeing contrails from jets that are merely "passing by".....to other more remote destinations, and from other more remote origins.
Understand this, please. The way a jet descends can be simplified in a "3 to 1 ratio"......for every 3 miles
of forward travel, you
can expect to lose about 1,000 feet. Of course, I mixed "miles" and "feet" there, but it's easy to remember....if you convert 3
to feet, you get (we use Nautical miles, so it's 6,076 feet per)....3 X 6,076 = 18,228 feet.....so, for every 18,228 feet
horizontally, in a typical descent, you lose (when at normal airspeed) about 1,000 feet vertically.
THAT is our "rule of thumb" guideline....not "hard-and-fast", just a general guideline.
NOW! In order to descend from the altitudes where you make contrails.....let's say at a "minimum" 25,000 feet.....to be able to get down to
land......QUESTION: HOW far away from the airport do you have to begin your descent?? Keeping in mind, the "rule of thumb" of "3 to 1" as I