Re: contrails over Reno


Message posted by Magoo on March 14, 2000 at 17:31:29 EST:

There are several aircraft types that are known for producing unusual contrails due to aerodynamic disturbance on their exhaust emmissions.

The Boeing 757 is one in particular, as is the new C-130J Hercules, and the new Boeing C-17. Alot of the newer large twin engined passenger aircraft (B767, B777, A330 etc) can produce strange contrails too. Please don't ask me why - I'm not a thermodynamicsist!

The SR-71 has been known to produce 'knotted rope' type contrails too, because of the shock waves of the supersonic bypass air coming out the engine exhausts. Photo's of SR-71s taking off show these shock 'diamonds' clearly.

Connie - did you notice whether the contrail was higher up than your 'average' contrail? You can usually tell this from the disturbance to the contrail by the winds - at lower levels the winds tend to be stronger and the heat rising off the earth stronger, and this tends to 'tear' apart and dissipate contrails faster. At higher levels, the trails can hang around for hours! If you were also able to determine whether it was just one solid trail, or two (or more) trails close together, that could tell us how many engines the aircraft had.

One story I read about an SR-71 mission over the top of Norway to the Barents Sea in the mid eighties, tells how the crew were really shocked to see another contrail at 82,000 feet whilst theye were on their way out from the 'target' area. They thought they may have been 'bounced' by a new Russian fighter that could reach that altitude, until they finally realised that it was in fact their own contrail they had made on the inbound leg nearly an hour earlier!

Magoo


In Reply to: Re: contrails over Reno posted by Richard on March 14, 2000 at 13:44:05 EST:

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