In the first half of the paper some of the basic aerodynamic engineering and piloting problems that have been encountered during the design and development of modern naval deck landing aircraft are enumerated and described. Such aircraft, of basically swept-wing configurations and high transonic or supersonic performance, have to be capable of being flown comfortably under full pilot control at the low speeds expected for carrier deck landings.

In Part II, the many devices of aerodynamic and engineering design will be described which have been evolved in an attempt to overcome or minimise the problems.

Turbine-powered helicopters mark the most important step taken thus far in the transition from development to business for that segment of the transportation industry which utilises the capability for vertical flight.

Completing more than a year ot detailed study and evaluation, New York Airways recently announced its commitment to purchase ten multi-turbine Vertol 107 aircraft designed to cruise in excess of 150 miles per hour with 25 passengers. They will be introduced into service in the spring of 1961. With these machines commercial revenues could, for the first time, offset all operating charges and produce a fair return on the capital investment—without government financial support. The availability of the Fairey Rotodyne in 1964 will place New York Airways in a position to offer the public a substantially enlarged and even more useful service operating on a business basis.

The successful development of a helicopter and its introduction into service may be influenced by several factors but a well co-ordinated development programme is by far the most important. A practical and realistic balance between representative ground tests and the subsequent flight proving is essential if the project is to be completed within a reasonable budget and time scale. The two parts of this paper cover these phases and aim to show how they are related in a particular development programme. The use of major fully representative ground rigs is discussed in relation to pre-flight functioning and fatigue life assessment; this is followed by the initial flight trials and finally the structural and performance clearance of the helicopter over its full design envelope. Although the tests and techniques described are generally applicable, the examples quoted relate to the Bristol Type 192, tandem rotor helicopter. The opinions expressed are personal and do not necessarily represent those of the Bristol Aircraft Limited.

The difficulties of computing a solution to the Prandtl lifting line equation for large values of A/a0 are well-known, at least to any investigators who have tried. In attempting to deduce the loading over straight-tapered wings, like those used on sailplanes, the author has used an iterative method by which the nth. approximation to the downwash is obtained by a numerical integration based on the (n–l)th. approximation to the distribution of circulation. The main difficulty here is essentially one of making a good initial guess of circulation for the first approximation to the downwash.

Existing approximate formulae for the thickness of laminar and turbulent boundary layers are used to derive a method of calculating the free-stream velocity distribution corresponding to a given variation of shape parameter.

Thwaites has given the formula

for the momentum thickness of a laminar boundary layer with free-stream velocity u (x). This is the integral form of the empirical equation

For some years the author has been interested in subsonic ram-jets as a means of helicopter rotor tip propulsion and has done a considerable amount of experimental work with this end in view. Most of the effort has been concentrated on producing engines to operate at the lower end of the speed range as it was thought that, however simple a ram-jet may be, this advantage is lost when other means of propulsion are needed for starting purposes.

I would like to add yet another note to those already published on the notions of viscous and hysteretic damping in a simple oscillator. In particular, I would like to hammer a nail into the coffin of the so-called “complex stiffness.“

One of the features which hysteretic damping may be defined to possess is the property that the energy loss per cycle (in sinusoidal motion) is independent of the frequency of oscillation, ω. This property is derived from some experimental evidence. It is shown in Reference 1 that this behaviour is reproduced by the particular integral of the equation