Events in the aerodynamic development of the multi-service V-22 Osprey tiltrotor are reviewed, with emphasis on recent flight test findings and the solutions developed. A discussion of the performance in the USMC, Navy and SOCOM missions is presented.

The Bell-Boeing V-22 Osprey tiltrotor is a unique aircraft capable of landing vertically, flying at speeds in excess of 300 KTAS (knots, true air speed), with the added feature of folding the rotor and wing for deployment from ships for US Navy, Marines, and SOF operations. During the development of the V-22, including 1200 hours of flight testing, a number of significant technology and design development challenges were encountered and overcome. This paper presents an overview of many of these challenges. It also reviews the integrated approach to testing to be used in the next phase of the flight test programme, and describes the changes that have been implemented to improve flight test productivity.

Potential function methods have been applied extensively to many terrestrial and space robot control problems. This paper extends these methods to multiple robot problems for on-orbit assembly. By considering a population of free-flying robotic vehicles in orbit, capable of both rotation and translation, the potential function method reduces complex assembly problems to sets of simple translation and rotational commands. This is achieved using a potential function incorporating both collision avoidance between the free-flyers and connection constraints in the assembled structure. The method also allows a subsumptive type control architecture with the flexibility to carry out many different assembly tasks simultaneously.

The selective bleed turbofan is a two shaft, three compressor, variable cycle aircraft engine. Its bypass ratio (BPR) can be modulated to suit the operating flight conditions. At subsonic flight speeds it operates as a medium bypass turbofan (low pressure mode or LPM). It becomes a low bypass turbofan (high pressure mode or HPM) when flying faster and is capable of supersonic cruise without reheat (RH).

The aim of this paper is to describe the selection of the main engine design parameters in the HP mode and to outline the challenges to be met to enable the powerplant to operate in the other mode. The components have to perform satisfactorily over a wide range of varying conditions. The resulting demands are reflected in many ways, for example in the operating lines of the low pressure compressors and in the overall efficiency changes with increased bypass ratio. In the case of the present investigation the two bypass ratios selected are 0·3 for the high pressure mode and 0·7 for the low pressure mode. The latter was selected after an examination of a choice of bypass ratios ranging from 0·4 to 1·0. The change in variable stators required to achieve the LP mode cycle is indicated.

The effect of changing bypass ratio on engine performance and handling is shown. The main conclusion is that the design of this engine seems to be feasible within current technological capabilities and further investigation is encouraged because it appears to yield significant benefits.

A computational study has been undertaken of 3D vortical separation from the curved surface of a prolate spheroid at high angle of attack (10° and 30°). Attention focuses on the predictive capabilities of a new variant of non-linear, low Re eddy-viscosity model and full second-moment closure, the latter coupled to a low Re k-ε Boussinesq-viscosity model which is applied to the semi-viscous near-wall region. The study demonstrates that both anisotropy-resolving formulations return very similar predictive performance which is in several respects superior to that achieved with the k-ε model based on the linear stress-strain relations. At the higher incidence angle, transition is free, and this is the source of considerable uncertainty in respect of the sensitivity of the predicted leeward flow to the location of transition. While none of the models is fundamentally capable of capturing natural transition, the ability of the non-linear model to suppress turbulence generation by irrotational straining at the windward impingement region, thereby preventing (bypass) transition by diffusion of turbulence from the freestream to the laminar boundary layer, is exploited to demonstrate that the sensitivity of the separated leeward flow to the location of transition is weak.

The RAF has been undertaking peacetime repairs on composite rotor blades, fibreglass radomes and panels on a variety of combat aircraft types for many years. However, the Service's main experience in the repair of aircraft structures manufactured from carbon fibre composite (CFC) material has been related to the Harrier II. In any future conflict involving air power, battle damaged aircraft, including the Harrier II, will have to be repaired rapidly to meet operational requirements. The repair techniques used may have to differ from those undertaken in peacetime but they must still aim to restore the full static strength of the aircraft within the time constraints imposed by the operational situation. Therefore, aircraft battle damage repair (ABDR) is a carefully planned alternative to conventional repair techniques. This paper describes the main CFC structures of the Harrier II and outlines the variety of RAF peace and wartime structural repair procedures applied to the aircraft. Examples are provided of various simple and complex repairs. Greater emphasis on adhesively bonded repairs is called for if Harrier II experience is to aid in the logistic support of Eurofighter 2000 (EF2000) in peace and war.