A3D Fuel Vent

One of the oddities of the A3D configuration is the change to, but apparently not a retrofit of, the fuselage fuel system vent.

It was originally a very small vent mast on the lower side of the left horizontal stabilizer.

Even after the bottom half of it was painted red, it's not very noticeable:

For some reason, on all A3Ds starting with Bureau Number 142650 and subsequent, both Bombers and Versions, the fuel vent was changed to a large mast extending from the left side of the aft fuselage. (The small red tube below the fuel vent mast was added at the same time; it was a drain for the vent system.)

The change coincides with the introduction of the tanker kit in production. It must not have been changed for a particularly important reason, since it doesn't seem to have been retrofitted to A3Ds before BuNo 142650, even on Skywarriors that have the tanker kit installed.