Mark152 From , joined Dec 1969, posts, RR: Reply 3, posted (13 years 8 months 3 weeks 21 hours ago) and read 1188 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.
Woodsboy From United States of America, joined Mar 2000, 1023 posts, RR: 3 Reply 4, posted (13 years 8 months 3 weeks 20 hours ago) and read 1179 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.
FDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 36 Reply 6, posted (13 years 8 months 2 weeks 6 days 23 hours ago) and read 1153 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.
VC-10 From United Kingdom, joined Oct 1999, 3691 posts, RR: 35 Reply 8, posted (13 years 8 months 2 weeks 6 days 21 hours ago) and read 1146 times:
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.