The tail rotor can be installed either as a pusher or as a tractor. Test results given in Chapter 4 show that the pusher is more effective since it is less interfered with by the vertical fin. Nevertheless, there may be reasons for using the tractor installation. For example, on the Sikorsky UH-60, the designers decided to tilt the tail rotor shaft to take advantage of a vertical component of tail rotor thrust. To obtain adequate clearances as a pusher, the tail rotor shaft would have had to be very long. As a tractor, the installation was much lighter and more compact.
The longitudinal and vertical location of the tail rotor with respect to the main rotor affects the mutual interference in hover, sideward flight, and forward flight. Reference.10.7 discusses test results concerning these interferences in hover. As might be expected, these tests show minimum interferences when the gap between the main rotor and tail rotor discs is large.
Reference 10.8 cites experience indicating that left sideward flight was smoother and the Dutch roll made more stable when the tail rotor was raised on the Hughes AH-64 during its flight test development phase.