Windtunnel tests on a two-dimensional model of a three element high lift system in a takeoff mode indicate that airjet vortex generators can produce a significant increase in lift at a given angle of incidence and a substantial increase in CLmax. An associated reduction in profile drag is inferred from measurements of momentum defect on the upper surface.

The improvements are much greater than those typically achieved with vane vortex generators and cannot simply be associated with the suppression of boundary layer separation. Instead, the airjets and the vortices which they generate promote enhanced mixing and momentum transfer across the complex shear layers above the main wing, from the external flow right through to the surface. Detailed surveys reveal, for example, that the slat wake is dispersed — or absorbed into a region of greater shear — and that the growth of the main wing boundary layer is significantly reduced.

It is suggested that neither the relatively low Reynolds numbers . and Mach numbers of the tests, nor the effects of windtunnel interference, detract from the general relevance of the novel principle involved. Attention is drawn, however, to the need for further work to elucidate and quantify the flow mechanisms and to establish the balance between the benefits from the improved aerodynamics and the performance costs of installing and supplying the jets.

The optimal takeoff performance of a vectored thrust V/Stol aircraft is analysed by a nonlinear programming method based on a sequential unconstrained minimisation technique. The study is focused on ship operations which involve VTO and ski-jump STO launches. Once the optimal ramp geometry is determined, minimum-fuel and minimum-time problems are solved. The optimal control sequences are evaluated and the effects of ship motion and atmospheric winds are discussed. A microburst encounter following an STO launch is also dealt with in terms of aircraft survival.

A thin, low cambered aerofoil with a tab at the trailing edge in inviscid, incompressible, two-dimensional, unstalled flow with varying freestream velocity and arbitrary, different motions for both aerofoil and tab is considered. The general expressions for unsteady lift and aerodynamic moment on aerofoil and tab are derived within the assumptions of potential theory.

To verify the approach proposed in this paper, the classical Theodorsen case of an oscillating aerofoil is adopted. For this case, aerofoil loads are calculated in the time domain by applying an inverse Laplace transformation to the approximation of the lift deficiency function in the frequency domain.

The comparison of the results calculated by this method with those obtained by other methods and experiments shows good agreement, which validates the general formulation. The loads on an aerofoil having different frequencies for main aerofoil pitch and tab deflection are calculated.

Measurements have been made of the surface pressure distributions in the region of the junction between an untapered wing, of NACA 0015 section swept back at 20°, and a flat plate on which a turbulent boundary layer had developed, for several values of wing incidence. It is shown that the section lift coefficient of the wing diminishes, while the pressure drag coefficient increases, as the junction is approached. Oil-flow visualisations on the plate surface show the passage of the horseshoe-like vortex which forms when the retarded boundary layer flow separates as it approaches the leading-edge of the junction. Kinks in the isobars on the plate correlate with the trailing “legs” of this vortex. The surface flow visualisations also show that the turbulence in the junction region spreads onto the wing from the leading edge at an angle of about 10°.

A rotatable X-wire anemometer was used to make measurements of the mean velocity field and of five components of the Reynolds stress tensor, in the wake of the junction, with the wing at incidences of 0° and 9°. Log-law (Clauser) plots were used with the profiles Ū(Y) of longitudinal velocity to estimate the skin friction coefficient on the plate, though adjustments of the zero for Y were necessary to obtain a sensible fit. These corrections were often larger than can be readily explained, but the skin-friction values are consistent with the corresponding, measured velocity correlation, . The Reynolds stresses in the wake region clearly show that the horseshoe-like vortex legs persist beyond the trailing-edge of the wing, the turbulence intensity being larger on the suction side for the wing at incidence.

Average values of the skin-friction coefficient on the plate in the junction region are little different from those away from the junction. No corresponding information is available for the skin-friction on the wing, but if this is likewise unaffected by the junction, then the total drag of the junction region will be greater than the sum of those of the isolated parts, simply because of the increase in pressure drag.

Excessive deceleration forces experienced during high speed deployment of parachute systems can cause damage to the payload and the canopy fabric. Conventional reefing lines offer limited relief by temporarily restricting canopy inflation and limiting the peak deceleration load. However, the open-loop control provided by existing reefing devices restricts their use to a specific set of deployment conditions. The sensing, processing, and actuation which are characteristic of adaptive structures form the basis of three concepts for active control of parachute inflation. These active control concepts are incorporated into a computer simulation of parachute inflation. Initial investigations indicate that these concepts promise enhanced performance as compared to conventional techniques for a nominal release. Furthermore, the ability of each controller to adapt to off-nominal release conditions is examined.