PPRuNe Forums - View Single Post - Engine Start-Is that smoke from fuel or oil
Old 12th July 2014 | 11:45
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SMOC
 
Joined: Jul 2000
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From: Smogsville
Smoke by definition occurs as a result of combustion, while I agree it can be inhibiting fluid involved in the video it would be interesting to know the temperature of the day, I've done wet spins on very cold mornings with cold engines where upon selecting fuel on the fuel vapour appears to condense and appear visually. Later doing the normal start the condition can be seen to stop immediately at the time when combustion begins, luckily it was a BA 747 with RB211-524D4s which as many know make a distinctive noise at light-off, therefore confirming the point of combustion coinciding with the vapour cloud stoping.

Unfortunately every video or picture of cases like these refers to it as smoke giving the impression it's like burning oil which is incorrect, it can still be seen today during very cold mornings where there is a short burst of fuel vapour/condensation but light-off occurs some time after as expected on a cold morning, usually after the aircraft has been parked overnight allowing the entire engine to get cold soaked.

http://www.!!!!!!!!!!!!!!/photo/North...114/0473034/L/

Last edited by SMOC; 12th July 2014 at 12:10.
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