This paper describes a method for using inverse simulation to obtain a preliminary assessment of helicopter handling qualities. Formal descriptions of standard manoeuvres, defined to establish the handling qualities of military helicopters, are used to drive an inverse simulation of a subject helicopter. The simulation generates the controls and states of the helicopter as it executes the manoeuvre and the results may be used to calculate values of quickness, a parameter defined to measure responsiveness. Initial results reveal that in the context of inverse simulation quickness is independent of vehicle configuration when, as specified in the requirements, the quickness is based on the helicopter's kinematic states. An alternative quickness parameter, associated with the control displacements required to fly the manoeuvre is shown to be capable of discriminating between the pilot workload involved in flying two different configurations through the same manoeuvre.

Closed form solutions for low thrust orbit raising are well known for mission analysis and vehicle performance prediction. This paper provides extended solutions which include nodal regression through the effect of the J2 oblateness term in the geopotential. Since regression is a strong function of orbit radius, the resulting change in ascending node angle is coupled to the in-plane orbital motion. However, it is demonstrated that the resulting dynamical equations may be separated and solved sequentially. Nodal regression during orbit raising is of importance for solar electric vehicles due to the resulting variation of sun aspect angle and eclipse conditions.

This paper reports on the experimental validation of a new model of slider-reefed ram-air parachute opening, using jump data collected by this investigator and others. The model is based on the parachute load equation of motion coupled with a new differential equation which describes the rate of change of the parachute's drag area. The model clearly identifies the important factors which determine the inflation peak load and opening time. It also features many scaling relationships useful for design work. Several predictions are shown to be design-independent. The experimental data used in this model validation were gathered during sport parachuting jumps performed by this author. Also used are data generated by the US Navy during tests of the MC-5, MT-1X/SL and MT-1XX parachutes. The experimental results and model predictions are found to agree within 20% accuracy over a wide range of opening speeds and deployment altitudes.

Recent experience in the prediction and assessment of windtunnel wall interference is reviewed. Three areas of development are identified. The first deals with the influence of wall boundary layers on wall-induced velocities in solid-wall windtunnels; the second is concerned with preparations for determining wall interference in the European Transonic Windtunnel and the third relates to recent studies aimed at providing the basis for correcting data to free-air conditions.

In recent years the increasing importance of electronic warfare has resulted in a proliferation of assorted antennae, large fairings and other foreign bodies attached to transport aircraft airframes. In many cases the size, shape and location of these excrescences are fixed by the requirements of the relevant electronic devices and it is then left to the engineers and aerodynamicists to attach them to the airframe in the least adverse manner.

This note describes an installation which was extensively tested in a large-scale commercial windtunnel and was found to give apparently well-behaved steady-state aerodynamic characteristics but which, when flight tested, exhibited unacceptable levels of airframe buffeting and rather unusual directional stability problems. A re-examination of the fuselage flowfield using a simplified model, but with attention focused on the unsteady aspects of the flow, rapidly identified the underlying cause and enabled a successful aerodynamic fix to be developed. The lessons learnt from this experience are presented as a warning to those contemplating the addition of large excrescences to any airframe.

For practical purposes, it is beneficial to be able to predict the useful operating range of an aerofoil in oscillatory motion before the onset of the strong non-linear effects associated with dynamic stall. In the current work, a range of criteria which have been used to indicate the onset of dynamic stall are presented. It is observed that, since all of these are based on physical manifestations of the dynamic stall process, they may only provide an indication that the process has started rather than identifying the initiation itself. A more suitable criterion for this is the concept of critical angle, first proposed by Wilby. It is shown that the critical angle, which is normally determined through an extensive programme of oscillatory tests on a given aerofoil, is achieved in advance of all the other criteria. The present work presents a correlation which has the potential to determine the critical angle, and hence the useful oscillatory range of an aerofoil, on the basis of simple ramp function tests.

A comparative study is made on the performance of several low Reynolds number k-ε models and the k-ω model in predicting the shockwave-turbulent-boundary layer interaction over a supersonic compression ramp of 16°, 20° and 24° at a Mach numbers of 2.85, 2.79 and 2.84, respectively. The model equations are numerically solved by a higher order upwind scheme with the 3rd order MUSCL type TVD. The computational results reveal that all of the low Reynolds number k-ε models, particularly those employing y+ in their damping functions give erroneously large skin friction in the redeveloping region. It is also interesting to note that the k-ε models, when adjusted and based on DNS data, do not perform better, as expected, than the conventional low Reynolds number k-ε models. The k-ω model which does not adopt a low Reynolds number modification brings about reasonably accurate skin friction, but with a later onset of pressure rise. By recasting the ω equation into the general form of the ε equation, it is inferred that the turbulent cross diffusion term between k and ε is critical to guarantee better performance of the k-ω model for the skin friction prediction in the redeveloping region. Finally, an asymptotic analysis of a fully developed incompressible channel flow, with the k-ε and the k-ω models, reveals that the cross diffusion mechanism inherent in the k-ω model contributes to the better performance of the k-ω model.