Lockheed Martin's Skunk Works has teamed with Karem Aircraft to joint develop the Optimum Speed Tilt-Rotor (OSTR) design. Karem's OSTR is one three candidate designs for the US Department of Defense's proposed Joint Heavy Lift programme.
The OSTR design was developed under a JHL concept design and analysis (CDA) contract awarded to Karem by the US Army's Aviation Applied Technology Directorate (AATD). Karem and Lockheed will now refine the design under one of three CDA extension contracts awarded by AATD.
The CDA studies identified an advanced tilt-rotor as the preferred configuration for the vertical take-off and landing JHL. Extension contracts were also expected to be awarded to Bell Boeing for the Quad Tilt Rotor and Sikorsky for the Variable Diameter Tilt Rotor, but these have not been confirmed.
© Karem Aircraft
Karem believes an advanced tiltrotor eliminates the need to compromise between vertical lift and efficient transport. The OSTR has a variable-speed propulsion system. This allows the proprotors to operate at higher speed in vertical flight for hover performance and lower speed in forward flight for cruise efficiency.
The JHL is pursued to meet the requirement to manoeuvre US Army Future Combat Systems armoured vehicles around the battlefield. The growing weight of FCS vehicles has increased the payload required from 20t to approaching 30t, and scaled-up designs will studied under the CDA extension contracts.