reply to post by Komodo3
I have lived near airforce bases and have seen contrails frequently...
Ha! You presumed to call me
'ignorant'?? (AND< no...I don't do this to "argue"...it is to EDUCATE. Denying ignorance, as it
Living "near" an AFB, and seeing contrails? You aren't seeing contrails being made by any of the airplanes arriving, or departing...IF you are
"near". Sorry...jets have to descend to land, and below about 25,000 feet, no contrails. Same after takeoff, they climb on departure, and are
(depending on routing, and traffic conflicts and climb rate) many miles downrange**, by the time they exceed 25,000 feet altitude. AND, even then,
NOT ALL CONTRAILS are persistent!!!
(**)You can do some rough math calculations. Figure a speed of about 250 knots (below 10,000 feet) then accelerating to about 300 knots. All the
while (if a large jet, passenger or military transport type) at a climb rate of 3,000 to 2,000 fpm. (Rate decreases, as you get higher, performance
Let's see an example: 300 knots works out to 5 miles per minute. At 2,000 fpm, time to climb to above 25,000 feet is 12 to 13 minutes. (Assumes
direct climb, average rate and speed). 12 minutes, times 5 miles? 60 miles away from the airport, before the airplane is in the altitudes where
contrails can form. Reverse that, for arrivals....typically, a normal power-idle descent, for large jets, gives a drop of about 1,000 feet for every
3 miles horizontally. (Our "rule-of-thumb" that is used, to plan descents...back before all of the fancy on-boards computers, that do it for us
nowadays). Below 25,000 feet, at around 65-75 miles away from the airport.
Some DO, in fact, evaporate (sublimate) just minutes after forming. I see it all the time. I ALSO see persistent contrails, too. BOTH exist. The
fact that you may not have paid close enough attention, nor had the classes required to learn this stuff, does not diminish the FACTS and reality of
contrails. Especially persistent ones, that ARE the reason for this hysterical nonsense, and faux "concern" over those so-called "chemtrails". They
do not exist.
edit on 28 November 2010 by weedwhacker because: (no reason given)