Abstract: Helicopter antitorque auxiliary propulsion system comprising a propeller attached to the tail boom adapted for powered rotation to create a directed air flow rearward of the helicopter, including a duct encircling the propeller and a pair of stabaron doors hingedly mounted in the ducted airstream to divert the air flow at high speed for directional control and to close at low speed and allow the air flow to be diverted through openings in the duct for directional and antitorque control.

Abstract: The lead-lag angle or phasing of a rotor blade system for helicopter can be adjusted by using a method and apparatus which positions the blade tip at a spatial location and angular orientation approximating a no-lift, full centrifugal load condition. An optical means is used to form a line-of-sight from the blade tip to a first and second target. The first target is mounted on the lead-lag hinge pin and the second target is mounted on or near the rotor drive hub. Both the optical means and either one or both of the targets may be offset so that, when the optical means, first target and second target will lie along a linear line-of-sight, the designed lead-lag angle of the corresponding blade to which the apparatus is coupled, will be achieved. The apparatus comprises a frame member through or on which the blade tip slips and includes levels to ensure the proper spatial and angular orientation of the blade given the specific rotor blade system.