This paper describes a comparative evaluation of two data smoothing algorithms for use in a two step estimation-beforemodelling procedure for aircraft parameter identification. A simple fixed lag smoother is compared with the usual, and more complex, modified-Bryson-Frazier smoother in the first, state estimation, step of the aircraft parameter identification procedure. The comparison is illustrated by application to the analysis of the Dutch Roll motion of the Embraer EMB-312 Tucano. Both algorithms were found to give results of comparable accuracy although the fixed lag smoother is computationally more efficient. It was concluded that the fixed lag smoother algorithm is an acceptable alternative to the modified-Bryson-Frazier algorithm in aircraft parameter identification applications.

Progress in aeroelasticity of fixed and rotary wing aircraft is compared by means of a selective review. Discussion of the role of concurrent engineering leads into modelling and validation, these being dealt with under the headings of aerodynamics, structural and integrated models. Formulation and solution of equations of motion are considered, which relate mainly to rotorcraft, and then aeroelastic performance improvement is covered. This includes optimisation, aeroservoelasticity and passive devices. Basic insight providing models are reviewed and the paper concludes with, further comments on insight, and also future progress in aeroelasticity.

The forces due to normal pressure have been measured in the region of the junction between a rear-loaded wing swept forward at 28°, and a flat plate on which a turbulent boundary layer had developed. The Reynolds number was 1·03 × 106, based on the streamwise wing-chord of 500 mm. At low incidences, 0° < α ≤ 6°, the local pressure drag coefficients were found to be negativeaway from the junction, and the interaction with the junction was found to be favourable;that is the pressure drag coefficient became more negative as the junction was approached. At α = −3° the pressure drag coefficient changed from a positive value away from the junction to a negative value close to the plate. These results contrast with those for a swept-back wing-plate interaction, which has been reported as being unfavourable so far as the pressure drag was concerned. At 6° incidence, the interaction remained favourable but there was evidence of root stall beginning. At an incidence of 9°, root stall was much more marked and the positive pressure drag coefficient increased as the junction was approached.

Asymmetric vibration of multilayered conical shell with core layers of viscoelastic material are investigated in this paper. The analysis presented herein considers bending, extension in plane shear and transverse shear deformations in each of the layers, and also includes rotary, longitudinal translatory and transverse inertias. Appropriate trigonometric series are used as solution functions in the Galerkin method to reduce the governing equations to a set of matrix equations. The corresponding principle of linear viscoelasticity for harmonic motion is used for evaluating the damping effectiveness of shells with elastic and viscoelastic layers. A computer program has been developed for determining the resonance frequencies and associated system loss factors for various modes of families of asymmetric vibration of a general multilayered conical shell consisting of an arbitrary number of specially orthotropic material layers. Variation of resonance frequencies and the associated system loss factors with total thickness parameter and circumferential modal number for three, five and seven layered conical shells, with three sets of classical end conditions: simply supported at both ends, clamped-clamped and free-free, which can be of some use to designers, are been reported.

Non circular jets are emerging as a new class of passive control mechanism of jet flow. Jets issuing from non circular nozzles, rectangular, square, triangular, elliptic etc, are found to entrain several times more ambient fluid than equivalent axisymmetric nozzles. Non circular jets are generally referred to as non axisymmetric or three-dimensional jets. The increased entrainment of these asymmetric jets, particularly that of elliptic jets, has attracted the attention of many researchers. As asymmetric jets, multiple jets of different geometric configurations have also been proved to be effective in passive control of the jet flowfield. Multiple asymmetric jets may be expected to emerge as an effective method of passively controlling the jets. Many researchers have studied the flow field of single three dimensional jets and multiple circular or plane jets. But studies on multiple threedimensional jets are very limited. Pani and Dash studied the flowfield of three-dimensional single and multiple free jets. Their observed mean velocity distribution results were in agreement with the theoretical profiles.

The multidisciplinary problem of tail buffeting is solved using three sets of equations. The first set is the unsteady, compressible, full Navier-Stokes equations which are used for obtaining the flowfield vector and the aerodynamic loads. The second set is the coupled aeroelastic equations which are used for obtaining the bending and torsional deflections of the tail. The third set is the grid-displacement equations which are used for updating the grid coordinates due to the tail deflections. For the computational applications, a sharp-edged delta wing of aspect ratio one and a rectangular vertical tail of aspect ratio one placed in the plane of geometric symmetry behind the wing are considered. The configuration is pitched at a critical angle of attack (α = 38°) which produces asymmetric, vortex-breakdown flow from the delta wing primary vortices. The results show the effects of coupled and uncoupled bending-torsional responses and the effects of Reynolds number.

This paper proposes a correlation which attempts to relate an aerofoil's low speed dynamic stall onset incidence to particular parameters describing its stall behaviour in steady conditions. These parameters, which can be derived from experiment or predictive algorithm, are the incidence of steady stall and a term related to trailing-edge separation characteristics. The correlation is based on a large amount of data obtained from a number of aerofoils broadly classified into two families: the NACA four digit series of symmetrical sections and a family of four profiles with the NACA 23012 as the generic shape.

The correlation has been extended to low pitch rates outside the “deep” dynamic stall range and, whilst it pertains to stalling under ramp motions, a link has been established with oscillatory motions. The potential of the correlation is demonstrated by its application to the design of a symmetric aerofoil for use on wind turbines.