There is an old saying in the aircraft industry that you can make a brick fly, if you give it enough power. How true this is I would not care to say, but it is certainly true that the worries of the designer are lessened if he knows that he can always give the throttle a little extra push, if all else fails.

This is not to say that the design of a conventional, high powered, aircraft is a simple, hit or miss affair, that would be ridiculous, but it does serve to show the special difficulties faced by the builders of a man-propelled aircraft who have less power available to them than is used by a small electric fire.

I will describe in this paper some features of current Boeing-Vertol production helicopters that I have selected as those which strike me personally as being of particular engineering interest. But first just to provide some perspective on the subject I would like to summarise the background of the present Vertol Division of The Boeing Company. The Company was formed in 1944 as the Piasecki Aircraft Corporation and its first product was the HRP Tandem Rotor Helicopter, which first flew in 1945. This was followed by the HUP in 1948, the H-21 in 1952 and the H-16 in 1953. In 1956 the Company was renamed Vertol and the next aircraft to fly was the Model 107 Prototype in 1958. In 1960 Vertol was acquired by Boeing and became the Vertol Division. The currently manufactured models about which I am going to talk, are the 107 series (now mostly in production as the US Marine Corps Model CH-46, Sea Knight) and the 114 series (in service with the US Army as the CH-47, Chinook) of helicopters.

The problem as to which engine configuration—single or twin—is most suited to the close support/tactical strike class of aircraft has faced both designers and Air Force personnel for many years. The inherent human choice on safety grounds is two engines. But, many aircraft built today are powered by one engine and good reasons for this choice have been produced. The basic arguments for one engine are the lower initial cost and better maintainability.

A comprehensive view of the overall costs incurred by selecting one layout as opposed to the other is a rarity, and yet it is possible to produce a definite indication, albeit by a broad brush, as this paper will show.

I have been asked to talk today about international co-operation with respect to helicopter airworthiness regulations. If I confined my talk to this subject only it would be very brief for, to my knowledge, this co-operation is at the present time very limited, if not non-existent.

The airworthiness committee of the ICAO which is the officially appointed organisation for international co-operation does not often deal with helicopter problems. As to the military, except for a number of points of a very limited scope (such as location of the cargo sling control on the cyclic stick) they have never really approached important problems specific to the helicopter from an international stand-point. The trend they are following today is rather to go by the civil regulations in force in their respective countries and there is an increasing tendency in the various manufacturing countries to consider conformity to civil regulations as the prime requirement to be met for the development of a prototype intended for military usage, except of course for a number of specific points related to battlefield applications which impose requirements different from those to be met for civil applications.

Head-up display (HUD) is an electronic presentation of flight information projected into the pilot's line of sight, enabling him to see both the outside world and relevant instrument information at the same time (see Fig. 1).

Using HUD the pilot no longer needs to alternate his attention continually between his cockpit instruments 2-3 ft (0·6-0·9 m) away and the outside world effectively at infinity. This continual change which present day pilots must make is first, very tiring and secondly it takes time; time to scan instruments, assimilate the relevant information, move the head and eyes, refocus the eyes on the outside world, adjust perhaps to a different light level and then take in the changed surroundings before returning to check the instruments. This time may add up to several seconds. In normal flight this is acceptable.

We continue our fundamental discourse on the natural modes in an element and extend our considerations to large displacements. First, we present a general procedure for establishing the so-called geometrical stiffness kG, when the natural modes of the complete element are given. The theory is a substantial generalisation and clarification of the method initially given in refs. 2 and 3 and shows that in establishing the modification to the transformation matrix aN it is necessary to ignore the contribution of the natural modes, which cause rotation at the nodal points but no displacement there. The point is subtle and was not made in ref. 2, although the applications given there are correct. As an example, the geometrical stiffness of a straight beam in space with all degrees of freedom is established. There follows the extension of the geometrical stiffness concept to a sub-element. This is of great practical significance for two reasons. First, it allows to derive the geometrical stiffness of elements of complex shape and behaviour, e.g. curved beams in space subjected to normal forces, bending moments and torque.

The purpose of this paper is to outline briefly the aerodynamics of high-lift devices in the most general possible way to provide the background against which the more detailed advances in calculation methods to be described by the RAE may be viewed. At the same time it is intended to discuss the factors affecting maximum lift coefficient in which the methods described in the RAE paper may be used to obtain improved performance.

The object of this paper is to illustrate the high-lift research programme at the RAE. It is not intended to be a complete survey of all aspects of this programme, but rather to highlight areas which will stimulate discussion of the programme. Again, it was not intended to consider only completed research work, but rather to illustrate the problems that are being investigated, and the ways in which solutions to these problems are being sought.

Throughout this paper I shall be using the term Guided Weapon to describe a weapon which receives corrections to its direction of flight after leaving the launching device, the corrections being related in some way to the measured relative positions and behaviour of the target and weapon. With this definition some rocket weapons are guided, others are not; most of the so-called ballistic missiles are not. I must also emphasise that the opinions expressed are my own, although I gratefully acknowledge the permission of the Ministry of Defence, Navy Department, to publish the paper. I have drawn on UK Naval experience, in much of which I have been personally involved, but at various stages the evolution of Naval guided weapons has been mixed inextricably with that of the other Services’ weapons. For this reason I chose a more general title for the paper.