md600n
Heliman
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| In a nutshell, the use of the Coanda effect as applied to the NOTAR concept for a full scale machine is described below...
The Coanda effect is the tendency of a fluid jet to adhere to a solid wall even when the wall curves away from the jet's direction. The downwash from the main rotor follows the curve of the tailboom much like the airflow over a wing, producing 'lift' sideways.
As usual, it's not as simple as that. The boom is pressurised internally by a variable-pitch fan at the fuselage end. Pressure is low at about 2 psi, but volume is high and the fan, rotating at 5,399 rpm, needs to shift 460 cubic feet of air per second at times of peak demand. Doing this can soak up 200 hp, so there's no great power-saving over a tailrotor.
There are eight horizontal slots in the right side of the boom, in two rows, one in the middle of the boom, one almost underneath. The air directed downwards by these slots mixes with the downwash, accelerating it and creating low pressure on the right side, providing the lateral lift vector to counter torque. The more the downwash, the greater the 'lift'. There's a baffle along the left side to discourage a similar effect there.
All of which would be tough to model in 72 inches of fuselage. |
