I am not trying to define a trend.
I am bringing attention to an effort to pretend that sharply increased helicopter losses don't mean anything. I think that Zig is treading on his interdiction and violating common sense.
Two points
Tyranny of small numbers.
Change in operational factors.
Zig's comment on sloppy operational detail. Similar sloppy operational detail is a root cause of an SA-3, Serb, shooting down an F-117 Stealth. (Stinkbug)
Some other non linear factors:
Change in geopgraphic concentration of helicopter sorties.
Increases in SAM's on hand by insurgents. A likely scenario.
Increases in weapons being dual used by Iraqi forces and their cousins in the various militias.
Changes in make up of troops in various areas, which includes more Iraqi troops, and thus more security breaches due to Iraqis being notoriously poor security risks, and more likely to give a tip to a militia if their loyalty is tested.
I don't think that has changed since I left.
DR