A review of some methods of obtaining augmented lift coefficients in aerofoil sections precedes a description of lift by circulation control by blowing. The basic aerodynamic characteristics are considered as a prelude to a comparison of the merits of their application to helicopter rotors.

In calculating the performance of a helicopter rotor which uses high lift coefficients, the determination of the induced power has demanded an extension of the performance estimation curves normally used. A theoretical model has been developed to calculate the induced power factor which suggests a large increase in this parameter for rotor thrust coefficients above the current helicopter operating regime. Experimental results up to thrust coefficients of 0·1 which confirm the theoretical results are presented.

Some tentative ideas on the application of circulation control to produce a high speed helicopter are considered.

When a large rocket or missile is fired, the hot exhaust gases must be allowed to escape without damaging structures or equipment in the vicinity of the firing area. Generally, the exhaust gases are directed harmlessly away from the launching installation by water-cooled deflecting surfaces fabricated in steel. In arid areas such as Woomera, where water is not available in large quantities, there is the possible danger that a steel efflux deflector will melt, and other materials such as refractories may be more suitable for the deflecting surface.

To provide data for the design of uncooled efflux deflectors, a heating rate investigation of the Blue Streak installation at Woomera has been carried out theoretically and experimentally. The heat transfer coefficient and stagnation temperature at the efflux deflecting surface are calculated theoretically with the aid of model test results. Heat transfer coefficients derived from temperature measurements on steel plates embedded in the deflecting surface are compared with the theoretical results. It is concluded that simple aerodynamic heat transfer theory can provide an effective engineering estimate of the temperature rise of an efflux deflecting surface.

It has long been known that compressibility affects the maximum lift coefficient at Mach numbers as low as 0·15. A schematic flight envelope (Fig. 1) shows that there are two main phenomena to be considered; the effects of compressibility on the low speed stall, and on the high subsonic speed stall.

In the low speed stall regime there is, in general, a decrease of the maximum lift coefficient with increasing Mach number which is appreciable even at typical aircraft landing speeds. A knowledge of the lift boundary throughout the envelope is necessary if allowances are to be made for gusts and if a safe rough-air performance is to be determined.

Summary:—There is no doubt of the need for strong central planning of aeronautical research and development as advocated by the Post-Plowden Working Party of the Royal Aeronautical Society (pp. 391-392 June 1967 “Journal“).

But there are many other problems in the efficient use of aerospace resources which are equally in need of attention by the Society. Among the most important are:

1. The complementary role of improved industrial and project management.

2. The need to deal separately with the distinct problems of Defence, Civil Aviation and Space—in particular the improvement of Defence procurement methods.

3. The need to discover the correct commercial and engineering bases (as distinct from political bases) for European collaboration.

4. The need to complement the work of a strong planning organisation by providing facilities for high-level and informed technical debate, wherever possible in public.

I would first like to thank the Royal Aeronautical Society for inviting Entwicklungsring Süd to give this lecture on the development work on vertical take-off aircraft. The Southern Germany Development Group—Entwicklungsring Süd—the abbreviation of which is EWR—was founded at the beginning of 1959 for the purpose of developing a vertical take-off and landing strike-fighter, the VJ 101, and was an association of the three firms: Bölkow-Entwicklungen KG, Ernst Heinkel Flugzeugbau GmbH und Messerschmitt AG. Heinkel has recently left the association and joined Vereinigte Flugtechnische Werke (VFW), Bremen. The work is now carried on by the remaining two firms, Bölkow and Messerschmitt. Since July 1965 EWR has the form of GmbH (Ltd).

In May 1966 under threat of USA withdrawal from the 1929 Warsaw Convention, over 30 of the world's leading international airlines agreed to increase the limit of their passenger legal liability from US $8300 (Warsaw) or US $16 600 (Hague) to US $75 000 (inclusive of legal costs) or $58 000 (plus costs) for passengers travelling to, from or via the USA. Today the number of participating airlines is over 90 and there are individual variations, eg (i) BEA has extended the new limits to all its Warsaw or Hague passengers; (ii) Lufthansa and other airlines have adopted the equivalent of a $58 000 limit for domestic passengers within Germany.

In the United Kingdom (including associated overseas territories) on 1st June 1967 the Hague Protocol came into force for the first time and the limit of liability for non-Convention (ie mainly domestic) carriage was raised to the equivalent of approximately £21 000 ($58 000).

The end of the first year of the new limits and the beginning of the new UK limits were marked by the Air Law Group of the Royal Aeronautical Society by an international discussion held at the Society on 1st June 1967. The Chair was taken by Sir William Hildred, CB, OBE, MA, and the principal speakers were: Dr. B. Cheng, University College, London; L. S. Kreindler, Trial Lawyer, New York; A. Goodfellow, Solicitor, London; and M. J. Lester, Secretary and Solicitor, BEA.

The aims of the Discussion were to:–(a) Review the present position nationally and internationally; (b) Discuss possible future developments from the viewpoint both of airlines and their passengers.

The hot-wire anemometer is one of the few instruments which can be used to make velocity measurements in turbulent and unsteady flows. However, the probe supporting the wire inevitably interferes with the local flow and it has been found that the effect of this interference on the reading of the anemometer varies considerably as the orientation of the probe to the flow direction is changed (the wire itself being maintained in the same direction). This leads to errors in any measurements taken where the instantaneous local flow direction differs significantly at any time from the direction for which the anemometer was calibrated. Such errors are quite separate from, and in addition to, errors due to finite wire length, incidence of the wire to the local stream direction, etc.

Every structural member deforms under the forces acting upon it. In this paper the Maximum Principle, recently developed by Pontryagin is applied to the problem of determining that profile of a beam that deforms least under its own weight. The beam considered is a solid horizontal cantilever having constant density, modulus of elasticity and width. The height is taken as an independent variable subject to the restrictions that it lies between an upper and lower bound and is symmetrically distributed about the centre-line. The method is attractive in that it can readily be extended to take account of variable density, width and/or hollow members by extending the control vector u defined in the analysis.

The cylindrical tankage which forms part of the primary structure of missiles and space vehicles may be subjected to high compressive axial and bending loads. Since allowable compressive stresses for monocoque construction are generally low because of small bending rigidity and sensitivity to geometric imperfection, it is advantageous to use some type of wall stiffening. One such choice is the integrally milled-out 45° waffle. This consists of a square gridwork of ribs which form 45° helices over the cylindrical surface. The panel is generally milled out in the flat and then bent up to form a circular cylinder. An advantage of the 45° construction is the exclusion of buckling modes between hoop reinforcement; such modes are frequently critical for the 0° to 90° type of stiffening.