Normally when I am speaking I have to balance both sides of the argument to make sure that everybody has a fair crack at the whip, and make sure that both points of view are put. Today I do not. It has been made abundantly clear to me they wish me to speak straight on an environmental point of view with particular reference to the noise problems. I will do so with the greatest of pleasure. We have a document here which has good and bad points, from the environmental point of view I would like to state the good, because there are some in this document. Firstly, we know where we are going and we know what we have got to argue about. We know where the Government wants to go in the size and use of our airports and from the Gatwick point of view this is something we have wanted for a long time. Secondly, major developments at the airports in future may be subjected to some form of local authority control, an argument the local authority has been making for a long time.

For most aircraft, longitudinal dynamic stability is assured if the static margin is positive. However, a statically stable aircraft is not necessarily dynamically stable. The problem of establishing under what conditions static stability is sufficient has recently been considered in Ref. I, by means of two-parameter stability diagrams. It seems to the present writer that a simpler approximate solution can be found by considering the factors of the characteristic equation.

The work to be described was planned as the first stage of an investigation of the effects of streamwise vortices on base pressure. An axi-symmetric blunt-based body was used, consisting of a cylindrical portion with a semiellipsoidal nose. The intention was to mount strakes or semi-delta wings at incidence on the sides of the body to produce vortices and to measure the effects of these on the base pressure. The base of the body was fitted with 37 pressure tappings so that local variations of base pressure could be explored. It was found that for the body at zero incidence and yaw, without any strakes or wings, there was great difficulty in obtaining an axi-symmetric distribution of pressure on the base.

In the production of aluminium alloy components, costs of rectification of distortion after heat treatment can become inordinately high, especially if those components are either large or of complex shape. With small parts of simple shape, the problem is avoided by forming in the solution-treated condition so that no further heat treatment is required, the principal limitation being that the forming must be completed within about two hours of heat treatment, otherwise the subsequent age-hardening process will be too far advanced. For more complex shapes, forming in the annealed condition is much easier, and indeed may be the only practicable procedure if a rubber press is to be used. Obviously pressing the components is generally quicker and more economical than manual forming. The problem that arises after forming—manual or press—in the annealed condition is that the components must then be solution treated, during which a water quenching operation can cause distortion, calling for the rectification previously mentioned.

First some independent comments about the access issues raised in the consultation document originally and in the White Paper most recently, and I can do so with a fair degree of independence because now having got the Heathrow Underground link all we have to do is to run it properly and some of the current problems will look after themselves

Perhaps I can give a somewhat independent view on the access issues for airports generally. Just for the record we are interested in access not only for air passengers but also for airport workers who are almost as numerous in their movements as the air passengers are, and those doing business at the airports, particularly those involved in the movement of commercial vehicles. Access is important because, first of all, it can consume a good deal of time and effort on the part of a passenger as part of his total journey.

The self-correcting wind tunnel has attracted considerable interest in recent years as a concept for achieving minimum wall interference in a wind tunnel. Sears, et al., have presented an authoritative account which is recommended to the reader. Among their important conclusions is that a perforated wind tunnel wall (with control of the pressures in subdivided plenum chambers) is superior to control of impermeable, flexible walls such as suggested by Chevallier and Goodyer. In Reference 2 and 3 and the discussion in Reference 1 it is assumed that the impermeable, flexible wall is deformed into an a priori determined shape of fixed magnitude. The selection of wall shape function and its magnitude is made so as to minimise wind tunnel wall interference. In the present paper this concept is broadened to allow at least the magnitude of the wall shape to vary with flow conditions, e.g. flow dynamic pressure. More generally the shape function might vary as well. As will be shown there are advantages to such a compliant wall concept.