Stealth Copters in Osama Raid?

Could be. [Link]

It was a secretly developed stealth helicopter, probably a highly modified version of an H-60 Blackhawk. Photos published in theDaily Mail and on the Secret Projects board show that the helicopter's tail features stealth-configured shapes on the boom and tip fairings, swept stabilizers and a "dishpan" cover over a non-standard five-or-six-blade tail rotor. It has a silver-loaded infra-red suppression finish similar to that seen on some V-22s.

No wonder the team tried to destroy it. The photos show that they did a thorough job - except for the end of the tailboom, which ended up outside the compound wall. (It almost looks as if the helo's tail hit the wall on landing.)

Stealth helicopter technology in itself is not new and was applied extensively to the RAH-66 Comanche. Priorities are usually different versus fixed-wing aircraft. Reducing noise and making it less conspicuous is the first job (more main and tail blades reduce the classic whop-whop signature). Listen here. 

Noise can also be reduced by aerodynamic modifications and flight control changes that make it possible to slow the rotor down, particularly in forward flight below maximum speed. Infra-red reduction measures are crucial -- the Comanche had an elaborate system of exhaust ducts and fresh-air mixers in its tailboom.