Springtime - S3-E6
Other mistake: While Radar is measuring the camp, he says that last year they had 2,986 square feet, but this year they have 2,863 square feet. The square root of 2,863 is about 53.5, so unless the camp is 53 feet by 53 feet (!) his numbers are WAY off. (00:16:15)
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 ★