The helicopter crash in the early scenes was unintentional. You clearly see the helicopter's tail rotor blades accidentally hitting the ground which caused the helicopter to spin out of control and crash, with debris and the top rotor blades narrowly missing the policemen in the scene and the crew off camera. The pilot received minor injuries. After being pulled from the wreck, Jack Riley and George Wilson quickly ad-libbed the rest of the scene as the wreck was set on fire. The crash of the $60,000 rented helicopter used up more of the budget than all other aspects of the film combined.
Shot on 35 mm Kodak 5247 negative stock film - very unusual for a low budget film at the time. Most low budget films were shot on positive stock film. The quality of the negative is one reason why many people thought the film cost more to make than it did.