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Smokey Start-ups........  
User currently offlineSJC-Alien From United States of America, joined Jul 1999, 919 posts, RR: 0
Posted (14 years 6 months 2 days 7 hours ago) and read 1729 times:

I've noticed over the years, that some jet aircraft engines emit a large volume of smoke(blue in color) from the engines after start up in the AM,,,rarely in the PM.

This occurs on 737-300/500 series,,,,never seen it on a -400 series. Some Airbus, 757 and also the L-1011 when they were in the later stages before most airlines quit using them.

I've never seen this on 727- or a 747 or a DC-10
after a start up.

Why do they smoke and how come it's usually on low /under wing engine pod aircraft? Am I wrong?

SJC Alien





10 replies: All unread, jump to last
 
User currently offlineDanny From Poland, joined Apr 2002, 3509 posts, RR: 2
Reply 1, posted (14 years 6 months 2 days ago) and read 1508 times:

Here are my thoughts:

1. Since there is some kind of "fire" in the engine on start-up, there should be smoke.

2. It seems to happen more on cold days, or in the AM as you mentioned. Could it be the hot, humid air condensing in the cold, dry air? Just like the "smoke" coming when we breathe when it's cold.

And, here are some pics to show the smokey start-ups. By the way - the 727 and the DC10 (actually MD11, but...) can have a smokey start-up.


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Photo © Richard Austen



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Photo © AirNikon



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Photo © Mathias Henig



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Photo © Darcy Stevens



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Photo © John Sidorowicz



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Photo © Jonathan Derden



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Photo © Søren Geertsen



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Photo © Sean Codier




User currently offlineDnalor From Australia, joined Mar 2000, 369 posts, RR: 0
Reply 2, posted (14 years 6 months 1 day 23 hours ago) and read 1485 times:

Hmmm, at first I was tempted to say it might have been oil accumalation, but then I believe Kerosine or its cousin Avtur1 can give off a white vapour when heated sometimes.

User currently offlineMark152 From , joined Dec 1969, posts, RR:
Reply 3, posted (14 years 6 months 1 day 13 hours ago) and read 1463 times:

From the terrace at LGW you get an excellent view of the rear of the engines at start-up. The ones which I have noticed to produce large amounts of smoke are L1011, 777 and Virgin's ex Air NZ 747-200. I also notice resonance during start up on the 777 and the 747-200 with RR.

User currently offlineWoodsboy From United States of America, joined Mar 2000, 1031 posts, RR: 2
Reply 4, posted (14 years 6 months 1 day 12 hours ago) and read 1454 times:

The Rolls Royce RB211 series is well known for its smokey start-up behavior. This engine is a common thread on the L-1011 (all L-1011s have RB211s), 757s (they employ the RB211-535 with some airlines) and many 747s that belong to foreign operators which are the ones I notice to be RB211 powered. The TriStar is perhaps the most notorious "smoker" although this doesnt suggest mechanical problems or old engines.

Aside from that I have also seen P&W powered 757s (Delta) have some pretty smokey starts, the colder the air temp the smokier! But as the photos suggest many a/c and engine types can produce billowing clouds of smoke.


User currently offlineTjwgrr From United States of America, joined Mar 2000, 2443 posts, RR: 2
Reply 5, posted (14 years 6 months 15 hours ago) and read 1431 times:

I believe it has something to do with fuel that is vaporized but not ignited.


Direct KNOBS, maintain 2700' until established on the localizer, cleared ILS runway 26 left approach.
User currently offlineFDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 34
Reply 6, posted (14 years 6 months 14 hours ago) and read 1428 times:

Nice pictures. Actually the United 727 isn't a smokey start but condensation being exhausted from the air turbine starter during the initial motoring up of the engine during the start sequence. The vapor is escaping the confines of the cowling. Often times this happens after it rains.


You're only as good as your last departure.
User currently offlineAaron atp From United States of America, joined Mar 2000, 533 posts, RR: 2
Reply 7, posted (14 years 6 months 14 hours ago) and read 1423 times:

like FDXmech said, water being vaporized in the engine, whether it be due to rain, or the temp reaching the dewpoint earlier that morning is the most likely explanation....

aaron


User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3701 posts, RR: 34
Reply 8, posted (14 years 6 months 12 hours ago) and read 1421 times:
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The white vapour that is emitted from the jet pipe can have two sources.

1. If the ignitor (spark) plug is worn it can be slow in lighting off the fuel so you see fuel vapour.

2. If the engine is an RB211, the fuel system has a Fuel Enrichment valve to assist with eng starts. this vlv allows additional fuel into the engine until the N3 reaches 54%. It is this additional fuel vapour you see on start.

If the smoke is blue it is oil that has leaked out of a bearing compartment in the hot section & is being burnt.

If the "smoke" is prior to light up then it is as FDXmech says.


User currently offlineBigGiraffe From United States of America, joined Jan 2000, 257 posts, RR: 0
Reply 9, posted (14 years 6 months 9 hours ago) and read 1409 times:

While the RB211 is making white smoke during startup it is also making a distinctive vibration which fades away when it gets up to speed. What is the cause of that?

User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3701 posts, RR: 34
Reply 10, posted (14 years 6 months 3 hours ago) and read 1399 times:
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I belive it is the harmonics between the 3 spools as they pass through specific RPM range's

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