Preventative Medicine - S7-E22
Other mistake: During the duration of the episode a wounded person is addressed as Corporal North but during the credits he is called Private North.
Other mistake: After pulling out of the camp to head for the cave, The Bus is shown from several angles. Even though it's loaded, the shots of it travelling are re-used shots from an earlier episode, and the place it stops is a re-used shot from the episode "Rainbow Bridge"





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 ★