As a general statement, like the DC-3, Cessna 310, and and a few other types, the B-17 has split flaps. Unlike plain or Fowler flaps, split flaps do a lot more for drag, than lift when extended. Were I to be trying to "make the field" with less than the power I wished I had, I would not be lowering any split flap, until I was fairly sure of making the runway. Faster approach speed, yes, but better than all that drag if you think you can't make it. I can't speak for this unfortunate situation, but that's what I imagine...