A Discussion on the Relationships between Government and Aeronautics was held at the Society on 4th November 1965 with the President, Sir George Gardner, KBE, CB, HonDSc, FRAeS, in the Chair. Short introductory papers were given by Mr. Denis W. G. L. Hayiland, General Robert Lecamus and Brigadier General Ake Sunden. Introducing these principal speakers Sir George said how fortunate the Society was to have persuaded three such eminent people to open this Discussion; they were particularly grateful to their French and Swedish colleagues. General Sunden had graduated as an engineer and had been a pilot since 1934. He had served in a number of commands and had been a flying instructor and a test pilot. He was now a member of the Board and Director of Aircraft, Royal Swedish Air Force Board, which included responsibility for aircraft, armament, aero engines, airborne electronics and test flying.

General Lecamus was also an engineer and a pilot; he had served as an engine specialist in various duties, including three years as Head of the Engine Test Section at the French Test Flying Centre at Bretigny. In 1948 he had joined Direction Technique des Industriel Aéronautiques (DTIA) (which later became DTCA—Direction Technique des Constructions Aéronautique) as Deputy Chief of the Development Department and later had served as Chief of Inspection Services in Toulouse for the South West of France. He was now Director of DTCA.

Mr. Haviland had served throughout the 1939-45 War in the Army but he also had learned to fly. After the War he had been Principal, Control Office for Germany and Austria, becoming Assistant Secretary; in 1951 he transferred to the Ministry of Supply becoming Under Secretary, and from 1959-64 was Deputy Secretary, Ministry of Aviation. In 1964 he had joined Industry and was now Chairman and Managing Director of Staveley Industries Ltd.

Over the past ten years the RAF has cost the country an average of some £500 m per year. Of this sum about £200 m has been spent with the aircraft and electronic industries, of which about half has been for new aircraft and weapons, the remainder being needed for spares, modifications and ground equipment. A further £200 m is expended on service and civilian manpower, the majority of whom have been employed on the maintenance of technical equipments or are needed to provide direct support for personnel so employed. Thus we have a situation where something like £200 m a year—almost half of the total budget—is spent upon maintenance.

As the cost of modern weapons systems needed to achieve the necessary operational performance is increasing rapidly, the front line strength of the Royal Air Force will be weakened unless substantial savings in these maintenance costs can be made, and this in the face of increasing complexity of aircraft equipments.

While the subject of this colloquium is limited to reliability, I feel it is essential to put this parameter in its right context as we as users in the RN see it.

We in the RN are most concerned with the availability of our aircraft to perform the required operational task. We define availability as the percentage of a given period of time that an aircraft is either being used or is serviceable ready for use. If availability is low then we need a larger number of aircraft to meet a commitment. With the cost of current aircraft and our restrictions on carrier complements this is a vital consideration.

The Purpose of Army light aircraft, fixed-wing and helicopter, is to help ground units to carry out their normal tactical task more effectively. Therefore the main roles are:

1. Reconnaissance.

2. Fire support.

3. Exercise of command.

4. Tactical movement.

5. Logistic support.

For special-to-arm tasks, light helicopters are integrated into certain major units of the Royal Armoured Corps, Royal Artillery, Royal Engineers, Royal Signals and Infantry. The aircraft must be capable of living in the field and be easy to maintain. Aircraft strengths in these units vary from six in an air squadron of the Royal Armoured Corps, to three in an air platoon in an infantry battalion.

In terms of cost, BEA estimate this to be worth over £3 000 000 a year or, putting it another way, 7% of the revenue we receive has to pay for unreliability.

No specific allowance is made for the rectification of defects in the scheduling of aircraft during its turn-round time and to cover this we aim to schedule two stand-by Tridents, two Vanguards, one Comet and three Viscounts for their respective fleet sizes, so that if the snags are anything but minor, the stand-by aircraft take over while the defective one is rectified.

No one present can be complacent about the standard of aircraft reliability and his contribution to it. This applies to all concerned, to those responsible for the requirement, those responsible for the specification, all those concerned in the design and manufacture of airframes, engines, equipments and components and finally, the user and his servicing organisation. Significant improvement in reliability will result only from a contribution by everyone involved. It seems that in recent years the attention given to reliability has been out of balance with that given to all the other desired qualities. Those responsible for the requirement must be prepared to sacrifice performance or perhaps time, or variety, or pay more, for a gain in reliability; they must be given some indication of the rate of exchange to help them in this judgment. The designer must have this problem of balance and compromise clearly in mind and must play his part in clarifying the issue. Generally we have striven after the best performance possible and because weapons systems take so long to develop this tendency is probably more pronounced. But if you cast your minds back, systems which were regarded as being designed somewhat conservatively have often, overall, given the best service. Thus my first point is that there must be a conscious compromise between performance and reliability, associated of course with the time-scale and cost of the project. The designer must give equal consideration to reliability and to maintainability (the two go together of course) as to performance and other qualities.

What I talk about relates to an experience on military aircraft produced for our own Services under the working arrangements which were then usual.

We have heard that the Services are finding that unreliability is taking too much of their time and money and could impair their fighting efficiency. I think that this situation is well understood by aircraft constructors, and that there is a real desire to improve the situation and to do whatever can usefully be done. But it is not easy to quantify the subject of reliability, and some of the approaches which have been suggested for improving reliability do not seem feasible to me.

Previous speakers have referred to the subcontractors being responsible for most unreliability. I feel therefore I must begin by pointing out that the electronics manufacturer merely designs equipment and assembles components from sub-contractors. Nevertheless we do take the responsibility for our products.

In the post-war period there have been continuous and rapid advances in the design of aircraft. To take full advantage of the higher performance and increasing speeds offered to them, the airlines of the world have demanded smaller and lighter electronic equipment providing, at the same time, more and more facilities. The rapid increase in traffic, the higher speeds of aircraft operation and the introduction of pilot-controlled communications have demanded more complex equipment and the electronics industry has met these requirements by continuous development of both components and equipment. It is a tribute to the industry that the present day equipments, although vastly more complex, are smaller, lighter and no less reliable than their counterparts of ten years ago.

My Part of this discussion concerns development for reliability—the part after the original design and before production starts. But this stage cannot be divorced from the other two. All designs evolve from past experience of one sort or another or analogies. So new designs are evolved which use bricks or assemblies or mechanisms which have been used previously, even though perhaps in another way; these pieces have therefore been tested and there is practical experience of their behaviour. This applied to the original design. It is certain, however, that this will require modification, because in the confined space and with the extreme technical requirements demanded in the aircraft industry, any initial design will require modification—if not the scheme has been too pedestrian in concept and will be out-classed by competitive ideas evolved with more daring. Thus once again the designer needs development knowledge.

I Would like to describe an approach which is being made by the Air Registration Board to the Safety of complex systems such as those used in automatic landing, or in supersonic and other advanced aircraft, since I believe that these methods may have a further application in the assessment of aircraft reliability.

Airworthiness Requirements can be considered to be of two kinds. There are empirical requirements based on engineering interpretation of past experience, and there are those which stem from a selected level of safety and which involve consideration of probability of occurrences. This paper is concerned with the second kind since it is relevant to the consideration of reliability.

I have been asked to express a user's viewpoint of what is required to ensure the adequate Reliability of military aircraft before their introduction into service, and to outline briefly what the Operational Requirements staff of the Royal Air Force are now doing to assist in this.

The problem of unreliability arises, particularly for military aircraft, from the increasingly complex systems which are needed to meet our stringent performance requirements. The reliability of equipment has not kept pace, and this has led to difficult and costly maintenance problems. These difficulties are further emphasised by tactical requirements which demand minimum maintenance in the field. The nature of STOL/VTOL operational aircraft and the need to deploy them with minimum support facilities is a special case where reliability is of outstanding importance.

An Examination of the available data on aircraft unreliability, whether on civil or military aircraft shows quite clearly that the systems engineering is more troublesome than the structural engineering.

The statistics show that landing gear, brakes, hydraulics, fuel and air conditioning systems are all at fault to approximately the same degree. In addition equipments for which the airframe manufacturer is not directly responsible, are a frequent cause of trouble.

The aircraft manufacturers’ contribution to improving reliability must come from three directions.

Failure of electronic equipment represents a significant proportion of the overall defect rate for modern aircraft. While this is not entirely surprising in view of the quantity of electronic equipment installed, and the variety and multiplicity of functions performed, it remains a serious problem.

The specific reliability of electronic equipment, in terms of separate facilities, has tended to show marked and continuous improvement, but this has been overshadowed by the increasing number of functions performed, and by greater dependance on this equipment. Most electronic failures occur without warning, and many of the remainder need delicate and complex test procedures to obtain even a few hours warning of impending failure. In some instances, particularly where electronics is used because of its rapid reaction time, a fault can, unless special precautions are taken, be a serious risk to safety, or cause other serious consequences even before there is any warning that a fault condition exists.

The Title of this paper presupposes the existence of the most important and fundamental document, namely a clear specification of design requirements.

The normal sequence of activities after receipt of the specification is as follows: —

1. Design.

2. Prototype and Experimental batch manufacture.

3. Development (and Approval Testing).

4. Production.

5. Customers’ Use.

The function of Design and Development determines the ability of the design to meet the specification, and this can be classified as the “Quality of Design.”

If You take a quick look at the subjects chosen for this Colloquium you will see that all except one have been, or will be, given by specialists and on their own subjects. In being invited to comment on the responsibilities of the user I have been presented with the unique task in this Colloquium of telling someone else what his job is. It is hoped, therefore, that the next ten minutes may provoke some lively discussion and will be taken in good part by anyone implicated.

Since the two speakers who follow are dealing with the way in which the user handles defects and defect records, it seems fitting to open with one or two comments on the user's responsibilities for this function, as seen by the manufacturer

About Half of the speakers so far have mentioned feed-back of user experience. Unquestionably, if we are to make real advances in reliability, Industry must be fed with comprehensive and timely data on the behaviour of its products in Service, and most of us would agree that the systems for data retrieval which exist today fall short of this requirement. It is inevitable, I suppose, that by the time we disperse from this meeting a number of problems within the whole field of reliability—whether to do with rig testing, responsibilities of sub-contractors, statistical prediction, contractual procedures, etc.—will have been thoroughly aired but not always with general agreement on them and in most cases without any feasible solution or break-through having been proposed. I suggest that the particular field of data feed-back is one where the requirement is almost unanimously agreed and where profitable and constructive steps forward are both identifiable and feasible.