717 Engines
 

Our gate is next to AirTrans and when they push out or roll in I always see a stream of low pressure smoke coming out from the center of the bottom of the engines. Just curious what this was... thanks !

I've seen the same thing outta GV's

It's a Rolls Royce engine (with BMW .. BR715) and ALL Rolls engines seem to smoke on start up. Unfortunate you were not around to see Eastern and TWA start up their RB-211s at LGA.. in cold wx, the airplane would vanish in the start up smoke.

The old L1011 engines were a sight. To quote Austin Power's "It's a man baby!"

well not so much smoke on start up but there is a little jet / stream of it coming out on the bottom center of the engine when running and its even more pronounced when they taxi in after landing. i was thinking some excess oil burn off like engine blow by on a car?

Could possibly be fuel venting. On older engines, there was often some fuel dumped on shutdown but the EPA standards now prohibit that. Most is captured but some apparently still is 'released'.

Oil Breather Tube
 

What the other guys are talking about is oil that seeps out of the main bearings, pools in the hot-section, then smokes on initial light-up.

What you are talking about is a vent tube on the bottom of the cowling, correct?

The T-45 does this, as does the T-1A / Beechjet, and I think the Airbus.

I'm pretty sure it is an oil vapor vent from the oil tank.

yeah that def seemed to be what i thought it was !

It is not oil or fuel. It is excess bleed air. It comes out in the form of condensation. There is an oil drain on the bottom of the engine, but only a few drops come out of that after shutdown.

airtrans
 

i flew the 717 at fl for 3 plus years...they told us it was the oil breather...