PAUL LEWIS / WASHINGTON DC
HYBRID CONFIGURATION AIMED AT OVERCOMING LIMITATIONS OF V-22 AND BA609
AgustaWestland has released more details about its proposed Erica hybrid tiltwing/tiltrotor concept, revealing a design intended to overcome many of the operating and performance limitations associated with traditional tiltrotor designs.
Engineers say that Erica will differ from current tiltrotors such as the Bell Boeing V-22 and Bell/Agusta Aerospace BA609 in three important respects. The planned 10,000kg (22,000lb) transport will have smaller diameter proprotors, outer wing sections that will tilt independently of the nacelles, and a continuous tubular structural connection between the proprotors.
Erica will feature a 7.4m (24ft)-diameter four-blade rotor, which unlike the V-22's and BA609's respective 11.6m- and 7.9m-diameter three-blade rotors, will have sufficient blade tip ground clearance to land and take off with nacelles forward in aircraft mode, improving payload/range performance. The highly twisted blade will be optimised for high-speed performance up to 350kt (650km/h) maximum cruise speed, compared with 275kt for current tiltrotors.
To help offset the reduced hover performance of the smaller rotor in helicopter mode, Erica's outboard wing sections will also tilt and can be moved independently of the nacelle to optimise angle of attack. Secondary benefits will include an enlarged conversion corridor between aircraft and helicopter modes and improved autorotation, says AgustaWestland.
Erica's two proprotors will be rigidly connected by a continuous tube that will support and drive nacelle rotation. This is intended to simplify and reduce the weight of the design by having piping and wiring run inside the tube and dispenses with the need for swivelling joints on the nacelles and synchronisation mechanisms.
AgustaWestland is aiming the vehicle primarily at the civil user market, where 95% of flight time will be in aircraft mode flying point-to-point and a very limited amount of flying in helicopter mode. Erica's double bubble, four-abreast fuselage is being designed to carry 22 passengers plus luggage up to 2,200kg of payload in short take-off/landing mode, or 19 passengers in the vertical take-off/landing role.
The European Union is funding the concept development along with four associated critical technology programmes. They comprise development of an advanced rotor hub for reduced noise and vibration, active flight control technology such as fly-by-light, an integrated drive system and a study of tiltrotor aerodynamic interaction, rotor performance, whirl stability and noise.
Source: Flight International
