Navigation is an art practised by all who travel but it developed as a science when the means of travel took travellers beyond sight of landmarks. Thus it was seamen who initially developed the science of navigation and the requirements of the marine fraternity drove its development until the invention of the aeroplane.

The capabilities of early aircraft limited their navigation requirements but as they could fly in conditions where visual contact with the ground was lost, the need for sophisticated navigation methods grew. At first marine techniques and equipment were adopted but these were found to have severe limitations in the new environment.

This report describes a series of steady and time dependent pressure measurements on a half-model of a rectangular wing of aspect ratio 4. The wing was mounted on a halfbody attached to a sidewall of the RAE 8 ft x 8 ft windtunnel and the tests were made at Mach numbers of 0·60, 0·70 and 0·80 with fixed transition and a Reynolds number of about 2·4 x 106 at the highest Mach number. The wing was oscillated about its mid-chord axis at four frequencies giving frequency parameters up to 0·27 at M = 0·80. The static angle of incidence was varied from -10° to + 10°; here interest is centred on angles of incidence for which the flow on the upper surface of the wing is separated.

Selected mean and oscillatory measurements are offered as a challenge to computational fluid dynamicists for this simple threedimensional configuration. The measurements are of particular interest because the transonic flows include both incipient and well developed separations.

Experiments have been conducted to study the impingement fiowfield, over a double wedge deflector, produced by the impingement of an overexpanded supersonic jet. The jet has an exit Mach number of 3.1 and an expansion ratio of 0.81. The distance between the nozzle exit and deflector apex was varied from 2 to 5 times the nozzle exit diameter. The experiment consisted of schlieren flow visualisations and measurements of pressure distribution. Load coefficient has been obtained by integrating the measured pressure distributions. Boundary layer thickness and skin friction coefficient on the deflector surface have been calculated by solving compressible turbulent boundary layer equations, using moment integral and moment-of-momentum integral equations in conjunction with the measured surface pressure distributions.

The purpose of this note is to demonstrate the application of a Flame lonisation Detector gas chromatograph for the measurement of gas concentration in short duration windtunnel facilities. The determination of gas mixing properties has many important applications in internal and external aerodynamics: for example, two phase flows in jets, film cooling and wake flow properties.