The General Flipped at Dawn - S3-E1
Continuity mistake: As the chopper lands on the pad, and the ambulance comes up, the pilot is as two different men when Hawkeye and Trapper approach and arrive at the chopper, meaning the landing was stock footage.
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 ★