11.   The helicopter saves fuel with just one engine, eliminating the tail rotor in traditional helicopters.

12.   The spot where the crack began supports the tail rotor.

13.   They also make several models of an increasingly popular commercial helicopter known as the NOTAR, which flies without the tail rotor common to other helicopters.

14.   Traditional helicopters have a vertical tail rotor to stop the main rotor from spinning the craft endlessly round and round.

15.   To prevent the craft from spinning like a top, sideways thrust from the jet engine, or a small tail rotor, counters the effect of rotor torque.

16.   A fault in the tail rotor has been confirmed by investigators as the cause of crash.

17.   As the Army Blackhawk helicopter was attempting to land on a narrow bridge over the Nitchaga creek in far north Queensland, the tail rotor hit a branch.

18.   Eduardo Pacinio, a farmer who claims to have seen the accident, said the helicopter was flying low when its tail rotor detached and the aircraft plunged.

19.   Failure of a swashplate assembly on the tail rotor or main rotor could cause the Apache to crash.

20.   Fenestron is a helicopter tail rotor with many slender blades rotating in a short duct.