[Viper]

A helo's cruise alt is one thing, usually around 2-3k, but depending on conditions helo's can get well over 6K alt. The main reason for flying at high altitude is to avoid sound detection in a Radar/Sam free environment. If you dropping inf/trash into a remote area free from Radar/thermal detection means then it's your "whack",rotor noise, that your concerned with. I was an Avionics Tech and AO/AG, aerial observer/Gunner for CH-53Ds. Unless we got above 6K alt we could be detected by ground troops not otherwise occupied. You spiral to alt, between 6-10k, then cruise to Lz/Dz area then bury the collective and trim back the engines until your 3k or so. It makes you drop fast and silent. Troops in the Dz/Lz area will still hear ya but at least the troops between point A and point B did't have a clue you were overhead. Getting ATGM to get close to a high flying helo would be a serious trick considering most of them with the range needed, are vehicle mounted and can't point much higher then 30 degrees. This is from personal knowledge and I am sure there are plenty of weapon systems out there that I haven't seen. I mid alt slow flying helo I can see being a hard to hit target for ATGM. But a "turfing", tree top flight or high Alt helo is pretty much untouchable by ATGM systems in most if not all situations IMO. I don't see Tows or Hellfires turning fast enough to even keep up with a helo unless he's in a hover or really slow. Some helo's are bigger the tanks, mainly the CH models, but we are also a lot faster and a hell of a lot more agile.

I guess there are two ways around this if you wanted to touch it. Make a Cruise. Mid ranged alt setting or make High alt closer to 8-10K alt. At that Alt, spotting anything standing still or smaller then an APC in the open is all but impossible. High Alt flights and drop down insertions were common practice and we trained on the tactic.