3 Commando Brigade

AI Locking With AA Undetected

Benzy is right - first you'd know of an IR manpad would be a smoke trail zooming towards you... good luck

Whilst working on the Apache mod, I've become familiar with Kimi's IR jammer.  It needed a little fixing, but that's another story.  As there is no IR jammer in game, it simulates the effect by releasing a stream of invisible IR flares.  It would be possible to fit this to our new helicopter mods, if required.

It may also be possible to add it to some exiting aircraft via our config mod, if required.

I'd suggest you think carefully whether its needed  though, as it could lead to unbalanced ground to air combat.

Edit:  It can also be configured to work against other guidance types ie radar

We need to get some RPG-happy AI's. If you watch videos of Dslyexci flying in their ArmA2 missions, he takes an insane amount of RPG fire. On the public I've not seen AI use RPG to attack a helicopter at all.
(They do use the Strela, but never the unguided RPG's)... is there any chance of getting this behaviour changed via one of the AI mods? IIRC there's some AI related config that tells them which weapons are suitable to attack what kind of targets.
The same goes for machine gunners: Any heli that's going faster than ~100mph is simply never engaged, even if it's coming straight at the AI in question. 

Until we can get other units to engage helicopters we'll have to leave the AA in as otherwise it'd be waaay too easy to keep a helicopter alive (Choosing a bad LZ or orbiting an hostile AO too low should be 'rewarded' with a fiery death!)

That might have been Zeus  but if it actually was AI we need to figure out how to make them do that more often

ASR_AI does Blind fire with RPGs

as previously mentioned, IR SAMS max ceiling is at best 15000ft and can only be launch detected by active radar launch warning systems which are nowhere near 100% effective and generally have blind zones (or the old classic mk1 eyeball).
Passive radar systems such as RWR (radar warning receivers) emit a warning tone (and often have a graphic display to show direction/strength of signal) when a search radar is detected.  A different tone/graphic will operate if a radar is detected in a track or 'lock' mode (this can be determined by different pulse and strength characteristics).

TL;DR 
Manpads and other IR = safe above 15000 and shorter range (generally meaning easier to evade too) 
Radar = easier to detect operational SAMS but they have a much higher ceiling (even able to reach airliners COUGH) and generally longer range.  sometimes track detected

yes I am aware that the TL;DR is almost as long as the original message.  so what. sshh.