>and two “scanners.” The purpose of the scanners was to stand by the B-17’s rear doors and keep lookout for other aircraft

I spoke to one of the CAF "scanners" when the B29 "FiFi" visited nearby and he said one of their roles was to watch for smoke in case one of the engines caught fire. The engines are "upgrades" from just after the war.

https://en.wikipedia.org/wiki/FIFI_(aircraft)