Shots of the helicopter main rotor speed taken from the outside as it is flying do not match the speed shown from the inside shots. The rotor is going very slowly when viewed from inside and could not sustain flight.
Bogie walks into a tent while pulling off his shirt then does it again after it's been tucked in.
Soon following the scene in which June Allyson gets the grenade away from the Korean soldier, the scene changes to outside where a chopper is a mere 15-20 feet from a tent. No way would a tent, even with the sturdiest canvas and 10-foot deep stakes, survive the wind storm of the chopper landing so close.
Major Webbe and many others in his unit are seen carrying and using firearms. Medical personnel of the U.S. Armed Forces are forbidden to carry and use firearms.
Early in the film, Bogart's character tells the nurses, "The smoking lamp is out." Smoking lamp is a navy phrase and was not, at the time, used in the army. However, the Army did use the phrase in Vietnam. Google "army version of the smoking lamp is lit." The quote "the smoking lamp is lit" is in Google books.
The aircraft strafing the hospital at the beginning of the movie have USAF markings. Thus the scene depicts a "friendly-fire", or "blue-on-blue", incident where combatants mistakenly fire on personnel of their own army/allies. Given that a MASH unit was to be as close to the combat zone as possible, such incidents, while not common, were not unusual.
Helicopters of this era required constant attention to the collective/throttle as well as the cyclic. The pilot is shown numerous times reaching up and holding his helmet mounted microphone to speak for extended periods of time. This lack of attention to the controls would render the helicopter unstable resulting in a less than smooth flight.
During surgery on the Korean boy, June Allyson's character is assisting the doctor but is not wearing gloves. During surgery, Allyson's character wipes her forehead with her hand, which is a definite no-no during surgery.
Bogie gets a cigarette accidentally knocked out of his hand by the soldier who gave it to him.
Rectangular film lights are reflected in Bogie's glasses.
When The 8666 "bugs out", the vehicles in their convoy have their headlights on. This would be ill-advised, as it would attract gunfire from the enemy. In fact, during their rest stop, when the lieutenant is admonished for smoking, they are fired upon by the enemy.
At various times during the movie ground vehicles and aircraft are shown with headlights, landing lights, navigation lights, instrument panel lights, etc. turned on with little concern for enemy gunfire. In a combat zone such lights are ill advised.
At various times during the movie ground vehicles and aircraft are shown with headlights, landing lights, navigation lights, instrument panel lights, etc. turned on with little concern for enemy gunfire. In a combat zone such lights are ill advised.
As Bogie moves away from talking to the wounded commander in the back of the truck, the shadow of the microphone is seen on the ground.
The pilot is often shown holding down the Push-to-Talk switch on the cyclic (control stick) while transmitting and receiving. With the Push-to-Talk button depressed, the pilot can transmit, but he cannot receive. These radios are simplex, not duplex like a telephone.