The free-wing tilt-body aircraft refers to a vehicle configuration in which the wing, fuselage, and empennage are in a longitudinally articulated connection. This allows the main wing to freely rotate relative to the body, while the empennage, which is in the form of a long twin boom connected to the rear of the body, changes its incidence angle relative to the body in response to external commands. The principal advantages claimed for the configuration are short takeoff and landing capability, and reduced gust sensitivity. The aerodynamics of the free-wing tilt-body configuration has been previously studied, but analysis of its flight mechanics is limited. In this paper we present derivations of the flight dynamic equations of motion using multi-body dynamic modelling techniques, and combine the resulting equations of motion with experimental aerodynamic data to achieve a nonlinear mathematical model for flight simulation of a generic free-wing tilt-body vehicle. The mathematical model is suitable for the study of detailed dynamic characteristics as well as for model based control law synthesis. Key flight performance, and stability and control characteristics of a generic configuration are obtained from the mathematical model.

A method for accommodating engine deterioration via a scheduled linear parameter varying quadratic Lyapunov function (LPVQLF)-based controller is presented. The LPVQLF design methodology provides a means for developing unconditionally stable, robust control of linear parameter varying (LPV) systems. The controller is scheduled on the engine deterioration index, a function of estimated parameters that relate to engine health, and is computed using a multilayer feedforward neural network. Acceptable thrust response and tight control of exhaust gas temperature (EGT) is accomplished by adjusting the performance weighting on these parameters for different levels of engine degradation. Nonlinear simulations demonstrate that the controller achieves specified performance objectives while being robust to engine deterioration as well as engine-to-engine variations.

This paper highlights unmanned aerial vehicle (UAV) conceptual design using the multi-objective genetic algorithm (MOGA). The design problem is formulated as a multidisciplinary design optimisation (MDO) problem by coupling aerodynamic and structural analysis. The UAV considered in this paper is a low speed, long endurance aircraft. The optimisation problem uses endurance maximization and wing weight minimisation as dual objective functions. In this multi-objective optimisation, aspect ratio, wing loading, taper ratio, thickness-to-chord ratio, loiter velocity and loiter altitude are considered as design variables with stall speed, maximum speed and rate of climb as constraints. The MDO system integrates the aircraft design code, RDS and an empirical relation for objective function evaluation. In this study, the optimisation problem is solved in two approaches. In the first approach, the RDS code is directly integrated in the optimisation loop. In the second approach, Kriging model is employed. The second approach is fast and efficient as the meta-model reduces the time of computation. A relatively new multi-objective evolutionary algorithm named NSGA-II (non-dominated sorting genetic algorithm) is used to capture the full Pareto front for the dual objective problem. As a result of optimisation using multi-objective genetic algorithm, several non-dominated solutions indicating number of useful Pareto optimal designs is identified.

This paper discusses how structural load objectives can be included in a rotorcraft flight control system design in an efficient and straightforward way using multivariable control techniques. Several research studies have indicated that pitch link loads for various rotorcraft types can reach high or even unacceptable values, both in steady state and maneuvering flight. This is especially the case for high-speed aggressive maneouvers. Pitch link loads at high-speed flight are therefore taken as a case study. A novel longitudinal control system is presented, designed to reduce helicopter pitch-link loads during high-speed longitudinal manoeuvres whilst providing a pitch attitude command attitude hold response type. The design is based on a high-order model of a helicopter representative of the UH-60 Black Hawk. New metrics are presented for the analysis of structural loads that can be used in combination with ADS-33 handling qualities requirements.

In conventional gas turbine performance simulation, engine components are represented by characteristics where the 3D properties of the flow fields are averaged providing key flow properties at the component interfaces. Even though a very efficient method, the simplification of 3D flows to an averaged value is not always desirable. In particular for high-bypass turbofan aero-engines, the fan generates significant pressure variations from hub to tip. These profiles are affected by the flow profile resulting from the intake where boundary layers introduce radial distortion patterns.

This study investigates a performance simulation method where the intake and fan component of a two-shaft high-bypass turbofan are represented in an axi-symmetric 2D fashion. The intake was modelled using a commercial computational fluid dynamics tool. The remaining engine components were modelled using an in-house conventional gas turbine simulation tool with a radial representation of the fan. The coordinated application of both tools required an iterative data exchange, which is described in detail.

The inclusion of the radial representation of fan and intake showed twice the effect on thrust per inlet loss at cruise conditions. It was therefore worth considering despite the significant numerical effort.

An experimental investigation of aerodynamic drag reduction by counter How plasma jet injection from the stagnation region of a hemispherical blunt cylinder model flying at hypersonic Mach numbers are presented. Experiments are carried out in a hypersonic shock tunnel at four different jet-to-pitot pressure ratios namely 15·3, 24·52, 72·5 and 96·67 and three supply powers, namely 1·8KW, 2·7KW and 3·6KW. The flow fields around the test model are visualised using high speed schlieren technique. Direct force measurement is also performed using a single component accelerometer balance. The weakly ionised argon plasma jet has an electron temperature around 6,400K and electron number density ∼1.64 × 1015cm3. With plasma jet at pressure ratio 72·5 and 1·8K.W supply power the reduction in drag is found to be ∼28% (more than its cold jet counter part) although the plasma jet momentum is less than its cold jet counter part.