The first point which I wish to make, speaking on behalf of the Air Transport Users Committee, is that low fares are still an exception rather than the rule outside North America. There are some genuine low fares on the North Atlantic and many inclusive tour fares from this country, as other speakers have said, can be classified as genuinely low. Elsewhere in the world fares are still much too high, although we have been glad to see a slight reduction in fares to Scandinavia and to Australia.

While users very naturally are interested in low fares and do not wish to pay more than is absolutely necessary for their travel, they do have reservations regarding low fares which are achieved by very high seat factors rather than by genuine reduction in cost.

Free flight testing of missile designs is generally necessary to confirm that accurate estimates have been made of effects due to the change in size from wind tunnel model to full scale missile and of effects arising from the flight dynamic behaviour of the missile. The amount of such testing is generally limited by the high costs involved and so every effort is made to obtain the maximum information from each flight trial. During recent years parameter estimation techniques have been developed to provide superior methods for analysis of free flight tests. They enable the analyst to extract the required data with greater accuracy from fewer tests than has previously been possible. The old equation error methods relied on measuring all the variables characterising the projectile motion and using the equations of motion to obtain a relationship between aerodynamic forces and moments and translational and angular velocities of the vehicle.

In the analysis of aircraft flight dynamics problems at high incidence, non-linear aerodynamic effects are of considerable importance. The aerodynamic phenomena are generally extremely complicated and the non-linearities may be difficult to predict quantitatively. In this note we confine our attention to longitudinal symmetric motion at constant speed and height. Our aim is (i) to enable the pilot to know when he is in a potentially dangerous manoeuvre (which could lead, for example, to a super-stall) and (ii) to determine simple control laws for an autopilot which would prevent such a super-stall occurring.

Interference fits are an effective method for improving the fatigue performance of bolted joints. The use of Taperlok bolts in aircraft joints is one such example. One of the most important but difficult problems to analyse in these joints is their behaviour after the onset of separation between pin and plate.

Extensive work has been done in the past for the analysis of interference fit joints prior to separation. A comprehensive survey of this area (up to 1965) was brought out by Venkataraman. He also presented many new analytical solutions by a direct method of continuum analysis for interference joints in finite domains. Analysis of these problems in the pre-separation zone continues to draw attention and recently, John Crews used a complex variable technique to analyse the stresses around a flexible pin in an infinite plate under uniaxial tension.