1. LIGHTER-THAN-AIR CRAFT COMPRISING AN ELONGATED HULL WITH A LONGITUDINAL AXIS, PROPULSION MEANS LOCATED AT THE REAR OF SAID HULL AND IN SUBSTANTIAL ALIGNMENT WITH SAID LONGITUDINAL AXIS, MEANS FOR VARYING THE DIRECTION OF THE THRUST ON SAID HULL BY SAID PROPULSION MEANS, SAID PROPULSION MEANS EMBODYING A DRIVE SHAFT HELD IN SUBSTANTIAL ALIGNMENT WITH THE LONGITUDINAL AXIS OF THE HULL, A ROTOR HAVING A PLURALITY OF BLADES, A DRIVING CONNECTION BETWEEN THE DRIVE SHAFT AND ROTOR INCLUDING PIVOT MEANS SAID ROTOR BLADES BEING MOVABLE ABOUT SAID PIVOT MEANS TO VARY THE PLANE OF ROTATION OF SAID BLADES WITH RESPECT TO SAID DRIVE SHAFT AND THE LONGITUDINAL AXIS OF SAID HULL SAID BLADES FURTHER BEING MOVABLE ABOUT SAID PIVOT MEANS AND WITH RESPECT TO EACH OTHER TO VARY THE CONING ANGLE OF THE BLADES DURING ROTATION.