Some of the radio chatter in the film was taken from actual radio transmissions made during the battle.
The Black Hawk going down, spiralling as it crash-lands, was achieved largely through real, skillful flying of the helicopter, with some CGI augmentation. The minute it hits the ground, however, the rotors are computer-generated.
The set was constantly bothered by stray dogs running into shots. Ridley Scott kept them in because he liked the authentic feel of their presence. Eight dogs were adopted by various members of the production and were eventually brought back to the US with them.
Nelson (Ewen Bremner) says to Twombly "Just don't fire that thing so close to my head, I can barely hear as it is." Bremner actually partially lost his hearing because of all the gunfire. He eventually recovered from it.
The scene depicting a soldier cut completely in half by an RPG is partially true. In reality his torso and legs were held together by his spine, and he survived unconscious for about two hours. In his commentary Ridley Scott opted to depict it as it is onscreen as he felt audiences would not be able to suspend their disbelief if it was shown as it happened.
Ridley Scott: [ceiling fan] There is a large ceiling fan in the scene where Garrison interviews Mohammed Atto.