Secret, stealth chopper in compound wreckage
Images of the wreckage of the helicopter left behind at Osama bin Laden's compound by U.S. forces have prompted speculation that the chopper is a secret, highly-modified version of the military's iconic Black Hawk.
The stricken aircraft, which commandos blew up at the scene, appears to be a long-rumored stealth helicopter, NBC News reported; a Black Hawk modified to reduce rotor noise and make it more difficult to detect by radar.
Pentagon officials have declined to comment as did Sikorsky, the helicopter's manufacturer.
Aviation Week reported that the chopper's tail appears to be highly modified compared to a standard H-60 Black Hawk. The report noted that stealth features on a helicopter usually aim to dampen rotor noise and reduce infrared signals.
Noise reduction can be accomplished by adding blades to the rotors and changing the way the pilot flies the chopper, such as flying in a manner to reduce the rotor's rpm, the report said.
As for reducing the likelihood of the aircraft chopper giving off infrared signals, Aviation Week pointed to an earlier helicopter prototype that had a complex exhaust system and fresh air ejectors to lessen the aircraft's heat signals.
If the modifications did reduce the helicopter's sound, the raid still was noisy enough to attract attention. A computer programmer, Sohaib Athar , was startled by the noise and posted a note to Twitter: "Helicopter hovering above Abbotabad at 1AM
