The SEALs on board braced themselves as the tail rotor swung around, scraping the security wall.

NEWYORKER: Getting Bin Laden

The rotors turn in opposite directions to cancel out torque, the twisting action which requires conventional helicopters to use a tail rotor a hazardous appendage.

ECONOMIST: Autonomous helicopters

Pakistani journalists started arriving at bin Laden's Abbottabad compound soon after the helicopter crashed and started filing stories about the mysterious helicopter and its oddly shaped tail rotor.

CNN: Are 'Swift Boat' attacks on Obama bogus?

It included the black box flight recorder, the fuselage with the engines and rotor gearbox attached, the separated rotor head with the main rotor blades still attached, and the separated tail.

BBC: Crash report urges safety checks

It explores the idea of a low-fuel-use plane that uses open-rotor engines mounted on what is called a Pi-tail in the stern of the ship.

FORBES: The World's Biggest Planes