The US Army's Aviation Applied Technology Directorate (AATD) is refocusing its recently launched effort to demonstrate new rotorcraft drivetrains to include emerging vertical take-off and landing unmanned air vehicles and not solely to improve the performance of in-service helicopter types.

Boeing and Sikorsky were recently awarded contracts under the Rotorcraft Drive Systems for the 21st Century (RDS-21) programme. This was intended to demonstrate new drivetrains primarily for growth versions of the Boeing AH-64, Boeing Sikorsky RAH-66 and Sikorsky UH-60X.

AATD is redirecting the RDS-21 to include smaller UAV applications by requiring scalable technology. This would allow the technology's use in the US Army and Defense Advanced Research Projects Agency's Unmanned Combat Armed Rotorcraft demonstrator.

The goals are still to demonstrate a drivetrain with a 35% improvement in power-to-weight ratio and a 20% reduction in production, operating and support costs. Earlier RDS-21 objectives had included a 15db cut in external noise, but this is being de-emphasised.

New technologies being examined include reduced stage main gearboxes, split face gearboxes, lightweight and affordable gears and spring overrunning clutches.

Source: Flight International