Good-Bye Radar: Part 1 - S8-E4
Visible crew/equipment: When Radar arrives back at camp the Korean driver fixes Radar's stiff neck, and just as Radar gives him the money and we hear people cheer that Radar's back, the shadow of the boom mic can be seen on the ground at the bottom left side of the screen.
Answer: The C-42 was a military variant of the Douglas DC-2. Very few C-42's were built, so it's questionable that Potter would specifically have seen that particular model, but, given his military background, it's not entirely unreasonable that he might use the military designation even when the aircraft in question is actually a civilian DC-2.
Tailkinker ★