Helicopter Flight Dynamics, 3rd Edition

10Tiltrotor Aircraft: Modelling and Flying Qualities

The XV‐15 research aircraft, designed and built by Bell Helicopters, first flew on 3 May 1977 and was operated by NASA and the US Army, delivering proof of concept demonstrations and multiple research outputs over more than 25 years. Results from research using simulations of this aircraft, undertaken by the author and colleagues, feature throughout this chapter.

Source: Photo NASA

Rotorcraft aeromechanics may be too complex to ever predict with high confidence; Programs must reflect this reality and plan for change in areas of high risk or technical complexity. We are good at using analysis and simulation to help us fix issues once we've found them in flight test but we are not so good at predicting problems before they occur.

(Phil Dunford¹, V‐22 Lessons Learned, AHS International Forum, May 2003)

10.1 Introduction and Scope

The introductory quotation, taken from Phil Dunford's keynote presentation (Ref. 10.1), highlights¹concerns with the industry's capability to predict rotorcraft aeromechanics and emphasises the importance of building in resources to be able to tackle problems as they surface in development. The presentation described the Bell‐Boeing V‐22 tiltrotor program, focussing on lessons learned from 14 years of developmental flight testing. This was 2003, and it would be another four years before the V‐22 fully ...