Continuity mistake: When Henry, Trapper, and Hawkeye get into the jeep with Radar notice the style of jeep and its number is 16930382, but when they're driving to the chopper pad the style differs - things such as hood, antenna, etc, and its number is 11172419. Then when the chopper takes off the jeep's style is back to the original jeep they were in.
Visible crew/equipment: At the chopper pad, as the scene plays out, reflections of the lighting rigs can be on the chopper canopy.
Continuity mistake: As Henry watches the chopper fly off, his back is to Radar's jeep. After he orders back to camp, Henry is suddenly standing with his right side to the jeep without having turned.
Other mistake: When Trapper and Hawkeye are driving along, you can see two points of light on the steering wheel. The lights are from from the filming illumination panels.
Other mistake: When Trapper and Hawkeye make the right turn after Trapper tries to use the restroom, you see that Trapper avoids the left side of the road just after the turn. This is to avoid the explosive charge set in the ground used to simulate a mortar round exploding.
Audio problem: At the end when Borelli is getting ready to take off, in the close ups you can see the main rotor blades starting to turn, getting ready to fly. But the sound suggests that the rotors and engine are already at full power.
Audio problem: As Hawkeye and Trapper get into the chopper, you hear the engine powering up, and the blades slicing the air, but the blades aren't moving at all.
Answer: Even an Army field hospital would have SOME weapons for self-defense if the enemy attacked. What's meant is that it's not a combat outfit, and therefore wouldn't have enough weapons to actually attack anyone. (It's also mentioned a few times that the Officer of the Watch is supposed to carry a pistol at all times, but Hawkeye refuses to do it when he's in charge and Colonels Blake and Potter don't enforce the rule).
Captain Defenestrator