Europe's Erica tiltrotor project continues as a paper exercise led by AgustaWestland. A much heavier design, the 10,000kg (22,000lb) Erica will also have smaller-diameter proprotors than the Bell/Augusta Aerospace BA609. Outer-wing sections will move independently of the nacelles, with a rigid continuous shaft running between them, to both support the nacelles and drive their rotation. To allow heavier payloads and longer range, the 7.4m (24ft) -diameter proprotors will provide ground clearance sufficient to allow take-off and landing in aeroplane mode. A highly twisted proprotor blade could raise Erica's maximum cruise speed to 350kt (650km/h), 75kt faster than current tiltrotors.
Since a smaller proprotor affects hover performance, the design team's answer is to reduce download on the wing by allowing the outboard sections to move independently. This should also deliver a wider aeroplane-to-helicopter-to-aeroplane conversion corridor and better autorotation characteristics.
To reduce weight, the support shaft between the nacelles will have pipes and wires routed inside. This will dispense with the need for swivelling joints and synchronisation mechanisms on the nacelles.
AgustaWestland plans to aim Erica primarily at the civil market, where it calculates up to 95% of operations will be in aeroplane mode. Four-abreast seating will allow 22 passengers to be carried but, for vertical performance, the limitation will be that magic number 19 - the maximum that can be legally carried without a flight attendant being on board.
Erica is one of five "critical technology" development projects partially funded by the European Union as part of a proposed transport policy. Others include an advanced rotor hub offering lower noise and vibration, active flight control technologies including fly-by-light, an integrated drive system and research into tiltrotor aerodynamic interaction.
Source: Flight International
