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.
Master Sgt. Norman Hooten (Eric Bana) retired after a 20-year career in the army, joining the federal Air Marshal Service and then working as a contractor overseas. After this, concerned by the high rate of opoid addictions and suicides among returning vets, he studied medicine. Dr. Hooten is a full-time medical specialist at the Orlando VA Medical Center, focusing on PTSD and other combat-related disorders, as well as drug abuse.
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.
Ridley Scott: [ceiling fan] There is a large ceiling fan in the scene where Garrison interviews Mohammed Atto.