The aircraft maintenance function is a vital element of airline operations. The achievement and sustaining of the airworthiness standard throughout the life of an aircraft is its prime concern and responsibility. There are many approaches one may take in describing the maintenance function, no one of which is complete in itself, but when considered collectively as a reference framework, can provide a comprehensive insight into the rather complex and dynamic process involved.

The generally steadily rising costs of labour and material, together with lagging or level fare structures, are demanding even greater gains in productivity and utilisation of resources to maintain profit margins and adequate returns on investments. The productivity gains made possible by introduction of jet aircraft are being exhausted and new ways must be found to achieve lower operating costs. At the outset I think it might be reasonable to ask ourselves the simple question “Why aircraft maintenance?” From an airline corporate or operating viewpoint it certainly conflicts with the objectives of attaining low operating costs, low material inventory levels, high utilisation of aircraft. I have stated on several occasions that “we are the trouble department—and when we have no trouble we are really in trouble”.

The One-Eleven autopilot has been developed in parallel with the aircraft as a whole, being largely prompted by the increasingly sophisticated requirements of our customers, and I am sure you will agree it is a continuing story of achievement of which the British aviation industry in general, and BAC with their sub-contractors in particular, can be justly proud.

The One-Eleven is not one aircraft, it is a “family” of aircraft, each member of the “family” having a unique autopilot requirement and standard of fit (see Table I).

A careful reading of this Report will show that there were not a few events of considerable importance, which occurred during 1970. These are worthy of mention.

Early in the year the Society was informed that, as from the end of the first quarter, the financial support, provided by the Ministry of Technology and the SBAC for the work of the Engineering Sciences Data Unit, would cease. Although this was not unexpected, it obviously posed problems on the future working of the Unit. The Future Policy Committee considered the future of ESDU and recommended to the Council that the prices of the Data Items be increased, and that the Society alone bear the financial burden. The Council agreed and the recommendations were put into effect.

It is a great pleasure and honour to accept the Royal Aeronautical Society's invitation to deliver the Eleventh Cierva Memorial Lecture. I remember Cierva from a number of meetings and conversations. He was one of the great pioneers without whose work the autogyro would have been developed only far later, or possibly not at all. His significant contributions included the following:

He created a completely new concept, the autogyro.
He perfected the flexible, rotating-wing which was later used by the helicopter.
He demonstrated autorotation. Before Cierva many doubted that autorotation was possible in case of engine failure.

The first part of this title is the name of the Royal Aeronautical Society's own book with which I was concerned, as an exercise in long term studies, stimulated by the Centenary Year. The second part was added especially for the lecture as it seemed a concise way of relating long term speculations with some practical restraints which have to be circumvented too, if aeronautics is to progress.

Thiry-three years ago, by an ironic fate, a man passionately concerned with safety in air travel, which he hoped to achieve by a radical change from fixed to rotating wings, lost his life in an aeroplane accident. Since de la Cierva's tragic death, civil air transport has grown to a spectacular system, especially if one considers the speed of modern aircraft and the size of modern airports. It is, however, still quite small by comparison with other mass transport systems, if one takes ton-mileage or passenger-mileage as the yard-stick. Indeed the penetration of the aircraft into road, rail and sea traffic has not been very impressive except across the Atlantic and perhaps on certain routes in the USA. The modern airliner with a casualty probability of the order of 10-6 per passenger flight is considered a fairly safe means of transport. Although the cost of air travel is comparatively high, the mode of travel, especially the high cruise speed, is attractive.

Seaspeed was established as a wholly owned subsidiary of British Railways to operate high-speed non-conventional marine craft, concentrating initially on the SRN4 hovercraft. As a first preliminary it was decided to establish an SRN6 route across the Solent to gain operating experience. Since those early days, with two SRN6s, two HM2s and two SRNs the company has ferried 1 026 595 fare-paying passengers a total approaching ten million passenger miles.

The Solent was chosen for a number of reasons. It was the birthplace of the hovercraft and manufacturers were all readily at hand. The weather conditions in relation to the size of the N6 were judged to be representative of the weather conditions facing the N4 on the Channel. Further, as we saw that successful hovercraft would have to operate in crowded terminal conditions, operating in and out of Cowes would give us valuable experience that we could transfer to N4 operating. Our first N6 route was, therefore, selected as Southampton/Cowes.

I am deeply conscious of the privilege of giving this First Joint Lecture of the Royal Aeronautical Society and the Society of Licensed Aircraft Engineers and Technologists. I am delighted this has been initiated by our two bodies. Our close working together can only be to the benefit of aviation as a whole in this country. It is also another step in bringing closer together those concerned with research, development, and design with those of us concerned with maintenance. In these days of high costs of equipment and of labour, I am glad to say that maintenance is at last being recognised as requiring a much larger degree of attention at the initiation of projects than has been the case in the past. Moreover, it gives me particular pleasure that a Royal Air Force lecturer should be invited on this occasion because of the very close affiliation of the work of engineers in the Royal Air Force with that of the members of SLAET.

The rotor performance is computed for the two modes of VTOL flight, hover and cruise. In the hover mode the rotor must provide sufficient thrust to support the whole aircraft weight, whereas in the cruise mode only a small fraction of the thrust is required. On the other hand, the flow through the rotor is relatively small in hover, but large in cruise. These different conditions in the two modes of operation demand variable blade geometry in terms of blade twist, as well as aerofoil camber. The high thrust in the hover mode must be obtained with a minimum of blade area to avoid excessive drag in the cruise mode. To achieve this a fairly high tip speed must be combined with high lift coefficients. In the cruise mode on the other hand, tip speed and lift coefficients must be reduced considerably. This leads to a high advance ratio.

It is indeed an honour and a pleasure to join with you in honouring the memory of one of the great pioneers in British aviation. When I read the story of Captain Frank Barnwell's life so ably presented by Major Bulman in the first of these lectures, I was struck by the indomitable spirit of a man who, at the age of 57, was still determined to flight test his own new design. It is the same type of spirit that sustained Alan Shepard through a decade of physical adversity to reach the moon at the age of 47 and perform on its surface with all of the vigour this mission required. It is this type of human spirit that has made all of the fabulous technical achievements possible, and it is this type of spirit that is an essential ingredient for the continued assault on the great unknowns that lie in murky darkness all along the frontiers of man's knowledge of himself and his universe.

In April 1961, the 4400th Combat Crew Training Squadron was activated at Hurlburt Field, Florida, to train US Air Force aircrews in the varied and difficult skills of special air operations.

Because of the increasing emphasis on counter-insurgency (COIN) operations brought on by the conflict in South East Asia, the concept grew from a training squadron to a numbered Air Force equivalent headquarters with two wings and a Special Operations School. Designated the USAF Special Operations Force (USAF SOF), this unit of the Tactical Air Command is responsible for training US aircrews for special air operations in counterinsurgency. Over ten different types of COIN aircraft are used in these tasks, from the multi-mission C-47 with nearly 35 years of continuous civil and military service to the newest aircraft capable of COIN operations, the OV-10A. Some of these aircraft are performing in conventional air operations such as the tactical air support mission of the forward air controller. All have COIN capabilities which have been used or are available for special air operations.

If R. J. Mitchell were still alive, then it is very probable that this creator of the Spitfire, the Schneider Trophy seaplanes, and other classic aircraft would be attracted by the challenge of space flight. This is more than ever likely at this precise point in time, when the technology of the aeroplane is being joined with that of the ballistic rocket, in readiness to take the next great step forward in astronautics with the new vehicles which have come to be called “space shuttles”.

It was with these thoughts in mind that I chose the subject matter of this Memorial Lecture, when the Southampton Branch honoured me with the invitation to deliver it.