Question for Monarch 757 Engineers
We've recently noticed from ATC fumes / smoke emanating from a vent on the underside of port engine, about a third of the way back from the front of the cowling. Probably on starboard engine as well, but can't see it from the tower. Occurs on taxy to stand after landing, and has also been seen on take off run. Only noticeable when backlit by low evening sun, so quantity of fumes is probably very small. Been to inspect the vent with pilot; the vent area seemed slightly wet, but no real clue as to origin of fumes. Pilot's response - 'Dunno, I just sit up front and drive it'. Any ideas to put our minds at rest ?