[Milsurplus] I-81-A Radio Compass Indicator

[C.Whitaker]

de WB2CPN
The guns on the belly and top of the B-17, and
maybe other airplanes, had a rather complex
non-electrical cam system for compensating
the aim for when the gun was aiming at targets
which were on either side, or below and above
the B-17.  Maybe the other guns, too.
Something like the three-dimentional cam that
was in the Norden bomb sight but it had servo
sensors. 
That's what I've been told.
73  Clete