In many design procedures for calculating supersonic isentropic flow the problem arises of calculating the change in Mach number which will occur due to a specified change in flow direction, e.g. considering simple Prandtl-Meyer corner flow, it is required to calculate the final Mach number M to which the initial sonic stream will be accelerated by turning through a specified angle v.

The aim of this paper is to describe some flight research on the aerodynamics of helicopters recently carried out by the Royal Aircraft Establishment at Bedford. Helicopter flight research has been a continuous part of the RAE programme since a Sikorsky R4 helicopter was delivered to Farnborough in 1945. Various types of single rotor helicopter including such types as the Sycamore, Sikorsky R6 and S51, Bell 47, Westland Wasp and Whirlwind have been used as test vehicles in the intervening period. More recently, two aircraft, a Westland Wessex and Westland Research Scout, have been used on aerodynamic research which includes performance, handling stability and control and some operational problems particularly those associated with operation from ships. Currently a Puma is being instrumented to take over the role of the Wessex. There is of course other flight research activity at RAE, notably in the general area of avionics in which other helicopters are used. All the tests described in this paper were made on a Wessex and are concerned with the aerodynamics of the main rotor. The work on the Research Scout which has a hingeless rotor with characteristics similar to the Lynx is used mainly for stability control and handling research and is not specifically discussed in this present paper.

The flow along the corners formed by the intersection of two semi-infinite flat plates has been studied by many workers, notably Pearson (1957) and Rubin (1966) who treated the case of a rectangular corner. The situation is characterised by a region of three-dimensional flow in the vicinity of the intersection line bounded by regions in which the usual two-dimensional boundary layer equations are applicable. Within these boundary regions a secondary shear layer exists whose velocity is normal to the ‘two-dimensional’ vector.

Veneration can often bestow an undeserved degree of respectability upon stories which have come down to us from the past. Some of these stories even acquire the status of legends if they are repeated with sufficient regularity, and, like the “laws” which tend to limit the vision of the scientist, these legends can restrict the retrospection of the historian. Aviation has its share of such tales, and it is one of these which now needs to be re-examined in the light of several new pieces of evidence.

The central character of this story is that great eccentric Noel Pemberton Billing, and the aeroplane with which we are concerned is the P.B.9, a neat little biplane scout which appeared at the outbreak of the First World War.

As an introduction to this paper, it would be worth defining a QSTOL aircraft, although it is not important that this be a rigid definition. The letters QSTOL stand for “Quiet Short Take-Off and Landing”, and may sometimes be abbreviated to STOL. A true STOL aircraft is capable of taking off and landing on a 2000 ft runway, this distance including the safety requirement to clear a 35 ft obstacle.

From the point of view of quietness, which is a subjective matter, dependent upon many factors, a quiet aircraft (according to one method of measurement) would produce a noise intensity no higher than 90 perceived noise decibels over an area of about 0·9 sq miles, of length 4 m, compared with an area of 16 sq m, length 14 m for such relatively quiet aircraft as TriStar and the DC-10, already in service (Fig. 1).

For the purposes of this paper, I shall call aircraft STOL if they can get in and out of runways up to 4000 ft long with a full payload, and any aircraft needing a longer distance will be conventional or CTOL aircraft.

Aviation is an advanced technology, constantly pursuing higher performance, and backed by painstaking research into new materials and techniques. The target of “performance” has changed with the period, but the extent to which energy can be provided for propulsion has always been rated of major importance. Since propulsive energy is stored on board in a fuel medium, the more obvious criteria for the fuel are the energy density (based on mass and/or volume) and the proportion of this energy usable within the propulsion system. At the same time, the fuel must respond safely to reasonable handling procedures. The more subtle requirements to emerge over recent years include those of a minimum potential for pollutant formation and, in the case of very high speed flight, a maximum capacity for heat absorption.

The objective of design is the production of manufacturing drawings which are right. This objective will rarely be achieved without first making mistakes which require experiment to rectify so that design is the work of a team which includes designers who draw, development engineers and experimental manufacturing operatives.

Design must have an output which can be valued and the value of the output must exceed its costs. In the aircraft industry, the cost of design is a considerable part of the cost of the product and must be recovered directly from the customer. Because underestimating the cost of design is endemic and because some work done to obtain orders will not be successful, not all cost of design can be recovered from the customer and so some costs must be written off.

A simple rational fraction is derived which gives the Mach number with an error of less than 0·05 per cent for a given value of the Prandtl-Meyer function.

A space vehicle is usually required to maintain a specific orientation with respect to Earth. If flexible appendages (such as panels of solar cells) are associated with the vehicle, the problem of controlling the attitude of the spacecraft becomes more complex. In this paper, attention will be directed towards the control of this class of vehicle when the control law suggested by Hughes is employed. This approach requires that the attitude and its rate of change with time are available in satisfactorily noise-free forms. The measurement of attitude is physically possible, but the measurement of rate is not. Consequently a Luenberger state observer was employed by the authors to reconstruct the rate information. A similar approach was adopted earlier where an analogue model of the observer was employed. It was found that in some situations the design procedure for the observer stipulated that very large amplifier gains should be incorporated into the model, and great care was needed to avoid this problem.

Two-dimensional flow past a bluff body can be constrained under two important circumstances. For single models, the side walls of a testing facility can impose a constraint on the flow past the model. On the other hand, for single row configurations the adjacent members impose a constraint on the flow past an intermediate member of the row. Both these effects are a consequence of boundary interference.

Ealier investigations related to the interference effects of side walls on the vortex shedding frequency and drag coefficient of single bluff bodies were limited to weakly constrained flows. Recently, side wall interference effects have been reported for severely constrained two-dimensional flows past normal plates, inclined plates, triangular prisms and circular cylinders Constraint or blockage for two-dimensional flow is defined as the ratio of the model width to the test section width. While defining blockage for single rows of bodies, the width of the test section has to be replaced by the spacing between adjacent rows of bodies.

It is a sign of greatness in a man that he leaves footprints like those of Good King Wenceslas to guide and invite others to follow. Sir Frederick left his boldly in the Aircraft Industry, SBAC, Cranfield, Royal Aeronautical Society, Air Registration Board and many other places. Not in every place but in all those I have named he has been my Good King Wenceslas and I his page.

In this lecture I could choose to follow any one of these tracks but they are not divergent but criss-cross and intertwine with the result that in starting along one I may well switch onto another. The track I shall start to follow is aeronautics at Cranfield.

The purpose of this note is:

1. (a) to provide a method for evaluating the fuel mass penalty incurred in flight after fitment of a system to an aircraft. The method relies only on a limited number of parameters and should prove particularly useful in the early design stages of a new project.

2. (b) to show the relative importance of the parameters involved, in particular the relationship between the fuel penalty due to system basic mass and that due to system drag (other than mass drag) which, depending on the flight conditions, could be significant or even greater.

It is naturally a great privilege to have been asked to give the 20th Henson and Stringfellow Memorial Lecture here at the Yeovil branch, within a few miles of the place where Henson and Stringfellow worked together and performed some of their historic experiments.

It is perhaps equally natural that, Yeovil having become the home of rotary wing VTOL in the UK and my own Company having pioneered high speed wing VTOL that I should have been asked to make some aspect of VTOL the subject of my paper.

The reinforcement for holes in tensile stress fields sometimes takes the form of an extensive thin plate attached to the sheet, especially if the reinforced region is of integrally machined or bonded construction. Such reinforcements are often placed eccentrically, that is on one side of the sheet only. It has been shown both experimentally and analytically that such an eccentrically placed reinforcement can promote considerable bending stresses.

Wittrick gives curves showing the effect of eccentricity in the case of the circular hole with an eccentrically located annular plate reinforcement in a plane, axially symmetric stress field. High, but only local, bending stresses exist which simple theory will not predict. The stresses are markedly higher than those given with the corresponding symmetric reinforcement. For example, under axisymmetric loading it is possible to design an optimum plate-reinforced neutral hole (i.e. the stress concentration factor is 1·0 in both sheet and reinforcement) if the reinforcement is deposed symmetrically about the plane of the sheet. If however it is placed totally eccentrically then for realistic sheet stresses bending raises the sheet concentration factor 2·0.

The EEC Treaty gives a good deal of prominence to transport policy. Among the activities of the Community specifically listed in Article 3 is Article 3(e)—‘the adoption of a common policy in the sphere of transport’.

There is a whole Title devoted to it, consisting of 11 articles (Articles 74-84), and the title is included in Part Two of the Treaty which is entitled ‘Foundations of the Community’. Yet on 5th June 1973, speaking in the European Parliament, the Commissioner responsible for transport (Mr. Scarascia Mugnozza) said:

‘… without wishing to detract from the progress already achieved, particularly when it is viewed in relation to existing difficulties, we must nevertheless frankly and objectively admit that very few of the aims of the common transport policy have been achieved.’

The flow along the corner formed by two semi-infinite intersecting flat plates is considered in which the corner line is parallel to the streamlines of a uniform incident flow and a uniform suction is applied at the plate surfaces.

Probabilism is the 16th century philosophical doctrine that certainty is unattainable but that belief and action must be governed by probability. As long as the existence, interpretation or application of a law remains doubtful, one may follow his own inclination, on the ground that a doubtful law cannot impose a certain obligation. But the subject “probabilistic design” embraces the idea of conceiving or planning of a thing so as to be fit for its purpose, more likely than not, but with less than absolute certainty. The designed “thing” is to be reliable. The lay meaning of “reliable” is trustworthy, predictable and good, and carries an implication that at successive points in time the “thing” will or could be somehow exposed to its purposed use and will successfully fit its purpose every time or most times.