The effect of swirl on the high speed flow past blunt bodies is analysed by assuming constant density in the region between the shock wave and the body. For small swirl the stand-off distance is only slightly affected, but it is shown that there is a critical value of the swirl parameter which, if exceeded, will cause a jump in the position of the shock. This is demonstrated by solving the full constant-density equations for the flow past a sphere and by a perturbation expansion in powers of the density ratio across the shock for a more general body shape. The perturbation solution shows that the pressure coefficient on the body is constant at the critical swirl number.

This paper contains results for the response of a helicopter rotor blade under stationary random excitation when the helicopter is in forward flight. The blade model takes into account the bending and torsional modes as well as the root-rigidity conditions. The resulting linear dynamical system equations with periodic coefficients are treated within the framework of the filtering theory to yield matrix ordinary differential equations for the required response-statistics themselves.

This paper presents a contribution to Watson’s formulae and gives analogous formulae for the higher derivatives of the functions ψm and ϵm of classical aerofoil theory. In Appendix A these formulae are related to Thwaites’s method of solving Theodorsen’s non-linear integral equation. The resultant equations are also given in matrix form, which enables the calculations to be mechanised by using automatic computers.

The effect of the operation of a 15 per cent trailing edge control surface on the flow around a two-dimensional aerofoil in a high subsonic shock-free condition is investigated using the integral equation method developed by Nixon and Hancock. The effect of retaining the non-linearities in the transonic potential equation is to increase considerably the magnitude of the pressures over the front part of the aerofoil in comparison with the pressure found using a modified linearised theory in which significant second-order terms in the boundary conditions are retained. The magnitude of the lift coefficient and the pitching moment coefficient are increased by 10-15 per cent over the values found using the modified linear theory, and by 20 per cent over the values found using standard linear theory. However, the magnitude of the hinge-moment coefficient is decreased by the order of 20 per cent compared with the modified linear values and by 30 per cent when compared to the standard linear values.

The power spectral technique has been extended to show the effect of aerodynamic non-linearities on the normal acceleration response of a rigid aircraft in the cruise configuration. Non-linearities in the normal force and pitching moment variations with incidence have been considered. The resulting changes from the linear root-mean-square values of normal acceleration were only 3 to 5½% for a root-mean-square vertical gust velocity of 20 m/s.

Experiments to determine the overall buckling and faceplate wrinkling loads of sandwich panels with carbon fibre reinforced plastic faces and honeycomb cores when loaded under uniaxial compression are described. The results are compared with theoretical predictions which assume that the faceplates are orthotropic. The effect on the experimental loads of certain coupling terms, which occur in the constitutive equations of those faceplates which are not orthotropic, is then considered.