Reverse Velocity Rotor Approach for Design of a STOVL Heavy Lift Transport for Expeditionary Warfare

The next generation of ship-based military heavy lift rotorcraft must be high-speed and capable of conducting long-range combat assaults in support of a full spectrum of combat operations. It must be able to operate in all weather conditions, day or night, from prepared or unprepared surfaces. The aircraft’s capability to achieve cruise airspeeds greater than 200 knots is based on technology currently being researched at Sikorsky Aircraft and reported in Refs. 1 and 2. The concept, called “Reverse Velocity Rotor (RVR)”, is applied in this report. The authors are grateful to Dale Ashby and Chris Van Buiten of Sikorsky for suggesting this system, which has been incorporated in the design. The Condor is a four-engine, rear loading, single rotor helicopter that utilizes an optimally sized wing to unload the main rotor during high-speed flight. The aircraft retains all the low speed handling qualities of a traditional helicopter but reaps all the benefits of a fixed wing cargo aircraft at cruise speed, with the wing providing 80% of the lift. Maximum range under mission conditions is 615 nautical miles. Maximum gross weight is 120,000 lbs. Maximum cargo capacity is 37,500 lbs. Each of the four engines has a maximum power rating of 6,150 shaft horsepower. The rotor system is an eight bladed (110 foot diameter), fully articulated, foldable system with each blade incorporating the RVR airfoil cross section. The rotor system is driven by a lightweight variable speed transmission that allows RPM to be set at either 100% or 50% of operating RPM based on flight mode. The anti-torque system is a traditional six bladed pusher tail rotor mounted to the tail vertical pylon. Auxiliary propulsion is provided by two propellers (fifteen foot diameter), each driven by one of the two wing-mounted engines shown in the drawing.