Warbird Information Exchange

I always wondered what the four vents on the top of the wing behind each engine were for. At least I'm assuming they are vents for something. perhaps not I may have read what their purpose was at some point but if I did I've forgotten it. I was reminded of it just now when watching an episode of "Jay Leno's Garage" where they were talking about the B-17 909.

do a Google image search for "B-17 Cutaway"

One of many such drawings says "ventilating slots for hot air from oil radiator and supercharger cooler"

Thanks.

If.you look closer at the leading edge of the wing you see air three intakes per engine. One is oil cooler, one is for the intercooler and one is combustion air that ends up mixed with fuel and ends in the positions. Now if you eeven closer you will notice they are.behind the props, witch is called ram air, in other words the prop rams the air into the intakes. And the air exits through those vents on wing and as exhaust.

As a model builder, one of my pet peeves is seeing otherwise beautifully done models of B-17s with big black soot streaks coming out of the wing vents. Photos of well-weathered Forts show that the relatively clean hot air coming out of the vents actually deflected the oil and grime slung back from the engines, leaving the areas behind the vents cleaner the surrounding wing surface. The only actual engine exhaust of course exits from the turbos underneath the wing.

SN

Its my understanding of the B-17 induction system that Ram Air intake air is directed into the turbo, with surplus air bled off into the inner wing area. This inner wing area air also supplied the "alternate" air supply for flight in rain conditions. The excess inner wing area air is vented to atmosphere through the upper wing surface vents behind the engines.
So, all that should really vent through those slots in the upper wing is clean, warm air....perhaps with a radial's ever present slight mix of oil fumes and small oil leaks...but mostly air.