LHcapt2007 From United States of America, joined Mar 2004, 235 posts, RR: 0
Reply 6, posted (10 years 11 months 3 weeks 5 days 13 hours ago) and read 5496 times:
Any possibility of the shifting hydraulic loads imposed from slats/flaps/landing gear contributing to the smoke? Steam from the oil breather sounds ligit, but was this pic on landing or TO(I know the reversers arent deployed but maybe just at touchdown or rollout if a landing, prob TO)?
Broke From United States of America, joined Apr 2002, 1322 posts, RR: 3
Reply 11, posted (10 years 11 months 3 weeks 5 days 3 hours ago) and read 5018 times:
On all jet engines there is some leakage of high pressure air past the seals at the bearings into the oil system. This usually occurs at the bearings that are in the high pressure compressor/high pressure turbine assembly. The oil breather allows this air to dump overboard and not pressurize the oil system. The air is vented through a fixed devise that centrifuges the oil out of the air so, usually, there is little or no loss of oil out of the breather.
What I believe you are looking at is the air coming out of the breather. The air is warm and in humid or cold areas you may see condensation forming in the exhaust. If the engine losing oil out of the breather, the color of the breather air will be darker and there is generally staining on the cowling at the exhaust port.
VC-10 From United Kingdom, joined Oct 1999, 3717 posts, RR: 33
Reply 12, posted (10 years 11 months 3 weeks 5 days 3 hours ago) and read 5011 times:
On all jet engines there is some leakage of high pressure air past the seals at the bearings into the oil system
That's what keeps the oil in! The rotor bearings are in a sump which is basically a box with the rotor shaft passing through it. Oil jets spray oil on the bearings in the sump and higher pressure air is fed into another 'box' around the sump. This air leaks into the sump through the seals and so keep the oil in the sump.
Both the oil and the air is extracted from the sump through the scavenge oil pumps and the mixture eventually finds its way to the oil tank in which there is a de-airator. Once separated from the oil the air is vented to the gearbox and vents to atmosphere via the centrifugal oil breather that removes any remaining oil from the air. It is this oil/air vapour you see in the picture.
You generally see the vapour when an engine is accelerating or decelerating as the internal pressures are unbalanced at this time.