A newly-developed stealth helicopter design may have been used to transport the US Navy task force that killed Osama Bin Laden at the start of May 2011, it's been suggested.
Images of part of the helicopter released over the past few days show a tail rotor layout that's unlike anything known to be in service today. Only the tail section of the secretive design is reported to now be intact, after the troops that killed Osama destroyed the helicopter, too.
Many sources now support the idea that the helicopter could have been a modified Sikorsky Black Hawk helicopter, with stealth-type upgrades.
The Sikorsky UH-60 Black Hawk is a widely-used helicopter design, produced in many different versions to suit the needs of various operators.
Experts believe that another classified version has been produced that incorporates a unique five or six-bladed tail rotor layout (adding one or two more blades to what's normal for the Black Hawk). This rotor is partially enclosed behind a disc shape: an arrangement that might be aimed at lowering the helicopter's acoustic signature and, so, making it stealthier.
Stealth helicopters are not presently fielded by any military operator, as far as we know, but the US did have a development programme running between 1996 and 2004. This focused on the Boeing/Sikorsky RAH-66 Comanche helicopter, which was an out-and-out stealth design. Among its features were radar-absorbent materials and retractable turrets while it, too, feature an enclosed tail rotor.
The secretive and unrecognisable helicopter apparently used in the operation to kill Osama was finished with a special type of paint, the experts say. This would make the helicopter less able to be picked up by infrared sensors of the type built into missile warheads. It seems likely that, mirroring its tail rotor, the mystery helicopter had five or six main rotor blades, too: more than most contemporary helicopter designs.
Less than 12 months prior to the Osama mission was carried out, Sikorsky announced plans to developed an unmanned Black Hawk variant, not as a replacement for conventional manned helicopters, but more as a complement to them. This drone Black Hawk would typically be deployed on especially dangerous operations, featuring a particularly high human casualty risk.
Meanwhile, other US military technologies are also reported to have been involved in the Osama Bin Laden operation. Potentially, these included the RQ-170 Stealth UAV, the existence of which was acknowledged by USAF officials in December 2009.