I wanted to update to the latest dev branch some time ago and steam wouldn't let. I tried using the Game Updater and I ended up having to do the whole game download since I made a mistake and installed the main branch instead. So I ended up having 1.24 Main Branch update ( which had a config glitch ) and the Dev Branch. I got both on the latest update, 1.26, and the dev branch is 1.27 or 1.28 something like that. After I updated my main branch to 1.26, I couldn't see helicopters. It may be because I used the Game Updated to download the Main Branch in the first place... maybe it didn't download properly, but the all the main pbo's are in the Addons folder, and the Arma 3 exe seems fine.