Nowhere in the literature of helicopter noise can one find a general understanding; only isolated, inconsistent, and often inadequately documented facts. These could, of course, be reviewed but hardly with profit; it is easier to ask critical questions of nature than of previous investigators.

For fundamental reasons the helicopter in its present state of development is not in fact matched to the bulk, low-cost transport of passengers. But for equally good reasons the phenomena of aerodynamically generated noise now bid fair to banish from inhabited localities all other forms of vertical take-off and landing aircraft so that, if a city-centre to city-centre aircraft transport system is ever to be practicable, it will most probably be based on some metamorphosis of the helicopter.

It is shown that stagnation line heating rates for laminar, transitional and turbulent boundary layers measured on swept cylinders at supersonic speeds, can be correlated in terms of a Reynolds number based on the spanwise momentum thickness at the stagnation line.

A critical Reynolds number for transition along the stagnation line is determined and experimental results show evidence of transition up to M= 10.

A test vehicle, in the G.W. sense is a body used in free flight to test components, structures, aerodynamics, servo controls, guidance systems and propulsion. The body may have weapon-like characteristics or may be designed purely to investigate a particular phenomenon or theory which has a bearing on the design of weapons. From the inception of the G.W. Department this work was given an important place in the programme and played a major part in laying the foundation of knowledge and experience on which the G.W. work in this country was built.

Two early test vehicles were CTV.1 and KTV.1. CTV.1 was used for a good deal of aerodynamic investigation, together with the development of free flight instrumentation and measurement techniques, it was our first “beam rider”, and was also used in a command guided role. The beam riding work was done in co-operation with TRE who were responsible for the guidance aspects of CTV.1. RTV.1 was a larger vehicle used mainly on beam riding guidance research. A later version was used in a vertically launched role to study launching and stability problems preparatory to the Black Knight work.

The CTV series culminated in CTV.S which itself took various forms. The CTV.S Series I was designed for aerodynamic measurements on a coasting dart at high incidences and therefore high altitude. CTV.S Series 2 was designed for kinetic heating investigations while CTV.5 Series 3 was an upper atmosphere sounding rocket, later known as Skylark and still providing a valuable service.

RTV.2 was designed for further work on liquid fuel propulsion and semi-active radar guidance research and was developed further to become the better known GPV. An interesting method of recovery from the sea was developed for this vehicle. With the requirement for ballistic missiles and satellite launchers a whole new field of work on missile structures, stability, control and guidance was opened up. This called for the development of the latest and very successful test vehicle, Black Knight.

In the early 1930s, when the 14-passenger DC-2 made its appearance, it was regarded as too big for anything but transcontinental operations, both from the standpoint of capacity and airport requirements. When its follow-on, the 21-passenger DC-3, came along, it sparked a mammoth new Federal Airport Programme, and several regional air carriers in the United States almost choked on red ink. Others merged into systems big enough to absorb this monster.

Had someone suggested that within a short span of three decades a helicopter carrying 28 passengers would be hedge-hopping around Southern California, operating day and night from “micro” airports, which we call heliports, I am afraid he would have been given a silent stare.

In comparison with the previous papers, this one is somewhat speculative in tone. In discussing commercial VTOL there is little hard fact to form a sound basis for extrapolation as there is with conventional aviation.

But we do know that relatively fast VTOL aircraft can now be engineered around the jet, the fan and the propeller. It also seems that VTOL may offer some peculiar advantages and bring about a significant increase in the capacity of the air transport system as a whole.

So it should be useful now to discuss in pretty broad terms the impact of the higher performance type of VTOL on the system: it will certainly be invaluable to the aircraft constructor to try to find out the influence of the whole air transport environment upon the design of the vehicle itself.

It has been shown both experimentally and theoretically that the Mach number range from 1·0 to 1·5 is very critical for panel flutter. Also, the correlation between experiment and theory in the above range has generally been poor.

Sufficient papers have now been written which are relevant to the title subject that it is possible to make a review of the subject and to make recommendations for further work. These papers are reviewed in approximate chronological order. In all cases the panels referred to are rectangular and unswept with the air flow on one side only, unless otherwise stated.

The main factor contributing to hydroplaning on slick runways is the existence of a squeeze film in the contact area between tyre and surface. The situation may be improved by optimising surface texture so that the asperities break through the water film in a minimum time. Two techniques are described for characterising surface texture: a superposition solution based on viscous channel flow and a dimensionless number approach involving size, spacing and shape factors. The “feel” of a surface is quantitatively obtained, and an outflow meter is described which, by directly measuring the mean hydraulic radius of runways, provides a comparison of their drainage abilities.

The history of the application of fungicides is one which shows a tendency to use ever decreasing quantities of spray liquid to the acre; the reason for this is obviously one of economics. The classification of various spray techniques is discussed with particular reference to the term ultra low volume. This may be defined briefly as the spraying of such extremely small volumes of liquid to the acre that it becomes impossible to use a simple aqueous medium as carrier. The reasons for this are given and the advantages of using special formulating agents noted.

The success of the low volume technique of spraying potatoes for the control of blight is illustrated with a series of blight progress curves, showing that 5 lb of copper oxy-chloride applied at 50 gpa gives identical results to a similar rate of copper at 2 gpa. Copper estimations made on leaf samples from the top, middle and bottom leaves of a potato crop sprayed at 100 gpa and 5 gpa respectively show that the mass distribution of copper is much more uniform in the high volume plots than in the low volume plots. However, the largest quantities of copper are found in the top layers of the plots sprayed at low volume.

It is necessary at the outset to discuss the limitations that are imposed by (1) the security classification normally attached to approved requirements and (2) the inter-relationship of technology and the establishment of formal requirements.

“Military requirements” may be defined broadly as formally stated military needs that are considered technically obtainable at reasonable cost in a specified time period. The required and obtainable performance will normally be classified as security information, as will the details of the intended concept of military operation and application. Hence, it is possible to deal with the subject only in a rather generalised manner.

Conditions of thermal fatigue encountered in the Aircraft Industry are usually located in engine components subjected to severe temperature and stress cycling. These components include gas turbine blading, nozzle guide vanes, flame tubes and turbine discs fabricated from a number of different materials ranging from Nimonics to sheet iron— and cobalt-base alloys. In recent years considerable experimental work has been carried out to assess material behaviour under thermal fatigue conditions and several means of testing have emerged. Rapid heating and cooling cycles using a “fluidised bed” technique have been extensively applied by Glenny and co-workers, at NGTE, and by material manufacturers to aid alloy development. Other experimenters have used axial straining devices based on expansion and contraction of heated columns followed by air cooling. One aircraft engine manufacturer has developed a thermal fatigue rig incorporating a repeated tensile axial load and temperature cycle. A further means of assessment has been developed by Forrest at NPL, in which the test specimen is strain cycled under reverse-bend conditions at constant or fluctuating temperatures.

When stagnation heat transfer rates are expressed in terms of free stream flow properties, the following combination of terms is found to occur: —

where ps pressure at the stagnation point

p∞free stream pressure

U∞free stream velocity

Dnose diameter

ßstagnation point velocity gradient.

In the past there has been some ambiguity—primarily in the spoken word—attached to the meaning of such terms as “thermal strain”. There is thus a need to standardise terminology. It is proposed that the following definitions be adopted generally. These are common to standard text books and have been adopted as a National Aerospace Standard in America and by the Royal Aircraft Establishment.

The definitions are not phrased for the mathematician, but for the engineer who deals with normal engineering materials. Materials which are not homogeneous or isotropic, for example, require more detailed mathematical definition.

This paper is concerned with two-dimensional, incompressible fluid motion generated within a square cavity (a) by an outer stream and (b) by the action of a flat surface passing over one of its sides. This type of motion (“cavity flow”) is considered to consist of a boundary layer surrounding an inviscid “core.” A solution of a linearised form of von Mises’ equation is obtained for steady flow in the boundary layer for constant pressure and that of a small periodic variation around the walls of the cavity. From this analysis the vorticity imparted to the core is obtained. The motion in the core is then determined on the basis of the persistence of this value of the vorticity. Experimental results are given for (a) and (b) and compared with the theory. A method of solution of the non-linear boundary layer problem is indicated.

This paper is in effect an illustrative case study based in part on an actual study but including also a large amount of subsequent work.

In the previous paper the cost structure of an air transport system was considered and some models appropriate to capital investment and procurement programmes were discussed. The importance of obtaining optimal utilisation of this capital equipment was stressed, and delays, especially during turn-round of aircraft at airports, were mentioned as one group of factors which reduce utilisation both of aircraft and airports and which therefore merit attention by the OR scientist.

Instead of proceeding immediately with the broad survey of models referred to in the second article, the opportunity is taken at this point to consider intensively one particular set of investigations focused on this problem area. It is based on field work done some years ago on the apron of an airport by A. M. Lee and the author, and is concerned with the human controller of turn-round operations.

It is of special interest in that it demonstrates the increasing ability of science to tackle problems previously considered intractable to any rigorous scientific method.