Nick,
You drive a good argument.
The Piasecki SpeedHawk was brought up because it is the first time I have seen 'hard' information relating to the power consumed by a tail rotor. This hard information being the statement
"a 500-hp tail rotor".
There is much 'soft' information available;
- Western aerodynamic texts have mathematically shown that the tail rotor wastes 8 - 10% of the power.
- Kamov has stated in an article entitled Aerodynamic Features of Coaxial Configuration Helicopter that the tail rotor wastes 10-12% of total power.
- Stepniewski in 'A comparative study of Soviet vs. Western Helicopters' says that the tail rotor consumes approximately 11% of the power, during hover.
- Prouty in 'Military Helicopter Design Technology' says, "... tail rotor absorbing 10 to 20 percent of the engine power".
I'll buy into your statements; up to the point where you start to implying that a single main-rotor + torque arrester can match the efficency of twin main-rotors.
Dave