Pre-Sept 11, you could get onto the Ft Rucker website and download to your heart's content just about everything including attack helicopter tactics training. With a bit more searching I found at the time that just about every training resource in the US Forces could be downloaded freely off their web servers.
Unfortunately when I found this I only had very slow dialup and only got one manual. Very shortly after 9/11, it all went bye-byes, and the Ft Rucker site is now one of the most unhelpful helicopter sites around.
From what I've seen (I've got a hard copy of the 1971 version of that manual), the dynamicflight site has got pretty much all of it there, and I'd be surprised if you found better anywhere else on the 'net.
Your only other option really is to buy the manual from one of the places that sells it to the public, and ask the publishers if you can get it as a .pdf (good luck).