Black Smoke From JAL 777
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Black Smoke From JAL 777
I'm confused about something
On the 11th April I was aboard a JAL 772 seat 57k right at the back and about 20 mins after takeoff and I could see a thin, dark black line coming from under the wing, which at first i assumed was the smoke trail of another aircraft below but under closer inspection it I noticed it appeared to be coming from the engine.
I was on the verge of calling a flight attendant when it seemed to all but disappear. Just as I had managed to pry my fingernails from the armrests I saw it reappear for a few seconds then go completely. I can happily say I didn't see it again for the rest of the flight...so I was wondering if any of you guys/gals might be able to help me with this?
Am I just paranoid or was this nothing to worry about?
Cheers,
TBP
On the 11th April I was aboard a JAL 772 seat 57k right at the back and about 20 mins after takeoff and I could see a thin, dark black line coming from under the wing, which at first i assumed was the smoke trail of another aircraft below but under closer inspection it I noticed it appeared to be coming from the engine.
I was on the verge of calling a flight attendant when it seemed to all but disappear. Just as I had managed to pry my fingernails from the armrests I saw it reappear for a few seconds then go completely. I can happily say I didn't see it again for the rest of the flight...so I was wondering if any of you guys/gals might be able to help me with this?Am I just paranoid or was this nothing to worry about?
Cheers,
TBP
Last edited by thebassplayer; 27th Apr 2009 at 20:32. Reason: bad spelling...
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I dont know the correct technical term, but you often see dark trails at wingtips when the air is very humid. It's caused by a vortex formed at the wingtip due to the pressure difference above and below the wing; the vortex can spin fast enough to reduce the air pressure inside it; reduce air pressure causes reduced temperature; reduced temperature can cause water vapour to condense. You do also see these - I'll call them vortex streams for want of a better term - at other locations also. I suspect you saw one of these.
Dark trails back from the engines (or a little distance behind them) are something I have noticed from time to time for the last 40 years. I have always assumed they are the start of formation of the jet trails. As most know, sometimes these are present and sometimes not, sometimes they start before the tail and sometimes afterwards, and the sun angle varies between flights, so in combination sometimes you see it and sometimes you don't - and if you are in F class, or on the flight deck, you never see it at all !
