In the present paper, it is presented the NOTAR Design App, a tool for preconceptual design of a NOTAR helicopter simulating a hover flight. The theoretical backgrounds are briefly introduced and the used mathematical models are presented. It is noted that the main rotor balancing counter-torque is generated by two separate phenomena: the Jet Thruster Force and the Tail Boom Circulation Control. The Jet Thruster analysis includes sequential control volumes along the inside of the Tail Boom, while the Tail Boom Circulation Control comprehends the examination of a sectional area of the Tail Boom and corresponding integration along the slot length. Results of the app depend on the user inputs and show reasonable agreement with the expected values.