The drag at cruise CL of a number of recent aircraft—mostly large subsonic transports—has been analysed in terms of figures-of-merit derived from Melvill Jones’ original concept of a streamline aeroplane. The values have been compared with those for some representative aircraft from the 1930-1940 period. The paper then proceeds to highlight some of the main sources of excess drag; for the recent aircraft, these are grouped under broad headings such as “excrescences”, “Mach-number effects” and “nacelle installation or interference”.

The results of the analysis are somewhat disturbing. Perhaps the most striking feature, bearing in mind that only a restricted class of aircraft have been considered, is the very wide spread between the figures for the poorest and the best of the recent aircraft. Also, the detailed drag breakdown varies widely from one aircraft to another. The evidence in the paper suggests that, in many cases, present drag standards can and should be improved.

This work deals with theoretical aspects of thrust vector control in rocket nozzles by the injection of secondary gas into the supersonic region of the nozzle. The work is concerned mainly with two-dimensional flow, though some aspects of three-dimensional flow in axisymmetric nozzles are considered. The subject matter is divided into three parts. In Part I, the side force produced when a physical wedge is placed into the exit of a two-dimensional nozzle is considered. In Parts 2 and 3, the physical wedge is replaced by a wedge-shaped “dead water” region produced by the separation of the boundary layer upstream of a secondary injection port. The modifications which then have to be made to the theoretical relationships, given in Part 1, are enumerated. Theoretical relationships for side force, thrust augmentation and magnification parameter for two- and three-dimensional flow are given for secondary injection normal to the main nozzle axis. In addition, the advantages to be gained by secondary injection in an upstream direction are clearly illustrated. The theoretical results are compared with experimental work and a comparison is made with the theories of other workers.

The various systems developed by, or under the responsibility of Engins MATRA, and which are related to the dynamics of the satellite, i.e.: the de-spin system, the precession damper, and the spin-up system will be described as well as the Attitude Control of the ESRO II spacecraft.

Before discussing these particular subjects, the general characteristics of the ESRO II satellite will be recalled:

The orbit is nearly polar (approximately 98° inclined to the equator) and has perigee at 350 km and apogee at 1200 km; the orbital plane precessions, in the retrograde sense, by about 1° per day; the orbit is thus synchronous with the sun's apparent motion. The launch time was chosen at 6 pm so that the orbital plane be, and remain, perpendicular to the sun's direction, at least in a first approximation. This is assuming a polar orbit and neglecting the angle between the plane of the Ecliptic and the plane of the Equator.

This work is concerned with the side force produced in rocket nozzles by secondary gas injection. A new theory for determining the side force is presented for two-dimensional flow and this is considered to be an important step towards a theory applicable to three-dimensional flow. The proposed theory is based on a double wedge model for the separated region upstream of the secondary port. The principal feature of the model is that it accounts tor the fact that the angle of the shock wave, originating from the separated region, is observed to increase with increase in secondary mass flow rate. Theoretical side force results are shown to compare favourably with experimental results obtained using two-dimensional nozzles and a comparison is made between the proposed theory and the theories of other workers.

The special structural problems of VTOL aircraft are examined, taking the Do 31 as a basis and it is shown how these problems can be solved without significant weight penalties.

After a short description of the aircraft and the systems associated with aircraft testing, the structural design of the Do 31 is described.

The effect of special VTOL load cases on the individual aircraft components are illustrated and it is shown where these are critical. The methods used in the calculations are explained briefly and theoretical results are compared with tests.

Special emphasis is given to the lift pod structure and its structural analysis.

There are special problems with VTOL aircraft which must be considered during the structural design phase. The effects of temperature on the engine pods, wing and fuselage are shown and the solution of the associated design problems are indicated. The results obtained are compared with a number of Do 31 test results.

If conventional British or US fire requirements are applied to the design of lift pods, there is a possibility of some weight penalties. Fire problems and fire requirements for lift pods are discussed with reference to test results. Recommendations for minimising the danger of explosions and for the use of fire detecting devices are also made.

A great advantage of VTOL aircraft is their ability to use unprepared sites. Debris may be thrown up by the downward deflected jet exhausts and strike the aircraft. Calculations and test results show the effect of impact velocities, stone shape, etc. Structural optimisation for withstanding debris impact is considered.

Noise problems have to be investigated during the aircraft design phase because of the high engine thrust installed in a VTOL aircraft. Results of the Do 31 tor near field noise levels are given. Particular attention is given to the proportion of overall noise level which affects the airframe.

The matrix methods of structural analysis developed specifically for use on modern digital computers have now become universally accepted in structural design. These methods provide a means for rapid and accurate stress and deflection analysis of complex structures under static and dynamic loading conditions and they can also be used very effectively for the stability analysis. In the conventional stability analysis two possible approaches are normally used; either the differential equations describing the structural deflections are formulated and the lowest eigenvalue representing the buckling load condition is found for a given set of boundary conditions, or alternatively, if the differential equations are too difficult to prescribe, approximate deflection shapes are used in the strain energy expression for large deflections which is subsequently minimised, leading to the stability determinant whose lowest root represents the instability condition. When designing complex structures the conventional methods of finding buckling load conditions are extremely difficult to apply, and therefore in such cases we have to rely on the matrix methods of stability analysis.

Both the authors have been members of a small Helicopter Research Team at the Royal Aircraft Establishment, whose main activities in recent years have already been described in papers presented at the V/STOL Loading Action Symposia held at Buffalo and Southampton in 1963 and 1965 respectively. It is a matter of regret that the size of this team, and indeed of corresponding teams elsewhere in Britain, has been such that significant reports could not be made more frequently. However, progress in research has been rapid elsewhere, particularly in the USA, and there has been a noticeable trend recently for changes in helicopter design. Hence, the Rotorcraft Section Committee requested a general survey of current rotorcraft aerodynamics. This is the object of the present paper, in which the findings of many workers in Western countries have been included. Even so, there will be omissions because the authors will not comment on subjects with which they have had no first-hand experience: rotor blade flutter and divergence is a notable omission on which there have been advances recently by the Massachusetts Institute of Technology and Southampton University.