Excellent, I hope you were toasty warm in the cabin. I still have yet to witness trails from piston a/c except from footage of WWII B-17/29s .......Yes, the Doctor Killers are smooth flying machines. Walter DCA ----- Original Message ----- From: "Dennis Murphy" <dmurphy4@houston.rr.com> To: <AIRLINE@LISTSERV.CUNY.EDU> > Way back when.......... > > I've pulled contrails with my Cessna T-210 (circa 1974) over Colorado & > Kansas in the winter. My Bonanza A36TC would do the same. I don't remember > what altitude, but I do remember it was lower than FL250 (maximum > "certified" ceiling on both aircraft.) For what's worth, the Bonanza was > more "fun" to fly......... > > Dennis Murphy > > ----- Original Message ----- > From: "W Wilson" <wlw-jr@att.net> > To: <AIRLINE@LISTSERV.CUNY.EDU> > Sent: Saturday, December 29, 2001 10:05 PM > Subject: Re: Contrails > > > > Richard, > > Here is a message I left about a month ago on the ComAirScan messge > > board...with a few changes. > > > > Depending on the temperature and humidity, contrails will form starting at > > around > > FL310 to FL350 (definitely not carved in stone.) . In summer, they may > not > > form at all. In the northern part > > of the US, contrails on a cooler day, may be around FL280 or lower, but > > while it can > > be cold enough for a contrail, there may not be enough moisture in the > air. > > Also, except for military aircraft that operate with fuel additives to > > prevent contrails, a Learjet can leave a contrail as a 747. Also in the > > Arctic, you may have seen photos of Twin Otters and > > C-130s leaving trails from start-up, to taxi, thru takeoff. Contrails form > > from the hot exhaust rapidly expanding as it hits the colder > air...remember > > physics... > > as air expands, it cools...if it cools to the dewpoint it > > condenses...thus a trail of moisture is formed. (in this case, due to the > > extremely cold temps...the vapor sublimates directly into ice crystals) > > > > To answer your Qs. Yes...there can be a narrow band of altitude where > > contrails will form...depending on temperature and dewpoint. > > > > Walter > > DCA > > > > ----- Original Message ----- > > From: "Richard A Whitenight" <rum.runner@juno.com> > > To: <AIRLINE@LISTSERV.CUNY.EDU> > > Sent: Saturday, December 29, 2001 20:58 > > Subject: Contrails > > > > > > > Anyone who watches the skies sees the contrails emitting from a jet > which > > > is obviously in rather cold air <grin>. Why is it that normally only > see > > > contrails in a narrow band of cold air? Is there a high and low > altitude > > > where contrails don't form, or is it strictly dependent on the > > > temperature of and/or moisture in the air. > > > > > >