Medinaj From United States of America, joined Jun 2000, 38 posts, RR: 0 Posted (10 years 3 months 2 weeks 1 day 10 hours ago) and read 3797 times:
I recently flew MAD-MIA on one of IB's classic 747. A few hours into the flight, I noticed a stream of blue-ish smoke coming out of a little vent on the side of the outboard engine. I started freaking out a bit and shut my sunvisor closed. A few minutes later, I checked again and the smoke had dissappeared. Some minutes later I looked again and it was coming out again.
We landed at MIA without incident, and at no point did the FAs or pilot advise or do anything out of the ordinary, so I assume this was a normal event. Anybody has any idea of what this was? Sorry if it's a dumb question, I just never noticed this before.
JeffDCA From , joined Dec 1969, posts, RR:
Reply 1, posted (10 years 3 months 2 weeks 1 day 6 hours ago) and read 3635 times:
I've often seen this when the aircraft are taxiing around at SFB, only seems to happen on RR's though. Seen it on the B742's RB211's, and the A330's Trent 500's, coming out a small vent under the RR badge. Doesn't seem to happen on the 767's CF6's though.
FLYtoEGCC From United Kingdom, joined Feb 2004, 947 posts, RR: 2
Reply 2, posted (10 years 3 months 2 weeks 15 hours ago) and read 3342 times:
I noticed exactly the same thing on an Monarch A330 this year. I have no idea what it was, but the engine was an RR Trent 772. It's a little sort of pointy vent facing backwards, and white smoke came out. I was a little bit worried, but as you say, after take-off it disappears.
Broke From United States of America, joined Apr 2002, 1322 posts, RR: 3
Reply 4, posted (10 years 3 months 2 weeks 14 hours ago) and read 3259 times:
What you were probably seeing are engine breather vapors. The seals in the engine's oil system at the bearings will generally keep out most of the high pressure air out of the system. But there is a little leakage past the seals. If you didn't have a way to relieve this increase of air pressure in the oil system you could over pressurize the oil system and start losing oil through these same seals and in other areas.
So you vent the oil system breather air overboard. The system has a unit that centrifuges most of the oil out of the air before it goes overboard, but a little will go out with the air. So you sometimes get a little bluish vapor coming out of the breather vent port.
If your oil temperature, oil quantity, and oil pressure are normal; then there is nothing to be worried about with these vapors.