US Patent 7871035 Propulsion system for an airship or hybrid aircraft

A propulsion system for an airship or hybrid aircraft includes a propeller and a pivot mechanism connected to the propeller. The pivot mechanism enables the propeller to pivot around a first pivot axis between a maneuver thruster position and an emergency ballonet fill position. Under normal conditions, when the propulsion system is disposed in the maneuver thruster position, the pivot mechanism also enables the propeller to pivot around a second pivot axis to control the attitude and thrust of the vehicle. However, in an emergency descent situation, the propeller may be rotated to the emergency ballonet fill position.