The dynamibility of a conventional helicopter is discussed with reference to the function of its swashplate. It is also shown how better dynamibility is achieved in stiff-blade coaxial helicopters by their very conception; in multiple respects. In horizontal-axis wind turbines, based on the assessment of the gyroscopic reaction moment of a single blade as it rotates and yaws, a rigorous proof of the optimum number of rotor blades to be three is given. Properly designing the main bearing is a main contributor to their durability, maintainability and dynamibility.