Hi 500N,
Good discussion and I may be mixing apples and oranges a little.
Much valuable use was made of sensors for reconnaissance in Vietnam from a range of fixed wing aircraft moreso than choppers and usually from above about 4,000 AGL. We operated 'people sniffer' gear from Hueys at tree top level level but no other electronic detectors. The state of the art sensor stuff is of course great and much of this kit is now an optional fit for fixed and rotary wing enabling cost-effective adaptation for particular roles.
War-fighting in barren open terrain like Iraq and Afghanistan requires some variations in operating practices compared with counter-insurgency in tropical jungle environs. As always, there is still need for a range of recce capabilities including visual reconnaissance where sight, sound, smell can locate human activity not necessarily detectable by sensors (e.g. cooking, toilet odours) emanating from caves, tunnels.
Attack helicopters have special applicability including of course armour busting for which they were initially conceived. But they are super-expensive and mostly not equipped with an adequate mix of gun weaponry for intimate close-quarters support (as close at 10 metres from friendlies) where weapon redundancy is essential.
The 2 helo gunship (light fire team) operating concept was not sound in my view because the trailing aircraft only provides support for the lead, but that differs when wagon-wheeling. Similarly for the AAH which tend to fly further apart for radar and sensor considerations. The following illustration depicts both 2 and 3 ship attack profiles for Huey gunships with the advantages of a 3 aircraft flight apparent. A 3 or 4 gunship/AAH flight would be best conducted in fighter low level battle formation during transit or reconnaissance giving effective cross-cover for all aircraft. But as indicated in APACHE, units operating that complex aircraft struggle to maintain 50 percent on line availability so they probably get stuck with the 2 ship concept (likely so for the Tiger).
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Basic 2 & 3 ship Bushranger attack profiles