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Aviation History
1954
1954 - 1165.PDF
FLIGHT, 23 April 1954 521 AIRLINE ENGINEERING . . . As in most airlines, B.E.A.'s maintenance function covers both routine maintenance of the aircraft on the routes, and over haul of equipment as well as aircraft. The major difference between B.E.A. and other airlines, however, lies in the use of the incentive bonus system. While experience has shown that such a system can reasonably be applied to the process of aircraft maintenance and overhaul and be well worth while, a good deal is still being learnt on the detail application of the system to the peculiar requirements of aircraft maintenance. The incentive bonus scheme was first introduced after the Vikings had been put into service, and with it came a main tenance system of centralized planning and rate-fixing. The emphasis was on planning of work in detail before the air craft came in for maintenance or overhaul, each man being given detailed instructions of the job to be done and how to do it. This particular approach was developed while the Viking was being developed and was settling down in service. Thus, as the particular idiosyncrasies of the Viking became well known, and the sort of troubles encountered on all new aircraft were dealt with, so the maintenance on the aircraft became more and more a matter of standardized routine. The difficulty with a system which depends on knowing too precisely in advance the work to be done on each check before the aircraft comes in, is that it can lead to lack of flexibility on the job, difficulty in making last-minute adjust ments, and difficulty in incorporating modifications on which the ultimate success of the operation depends. Two basic factors which determine the cost of maintenance in the airline are the amount of work to be done on the equipment and the cost of the replacements (spare parts and materials) required. The actual cost at any time arising from these two factors is a reflection of a number of things, and in particular (1) the suitability of the equipment for operational wear and serviceability; (2) suitability for ease of maintenance; (3) the total flying hours accumulated and the amount of experience obtained as a result; (4) the administrative skill in planning the maintenance work on the checks; (5) technical skill in deciding just how much work need be done. The great bugbear in the airline is the "special check" which appears on the maintenance schedule because some trouble has been experienced. It is so easy for the airline staff to call for a special check, or a check of all aircraft within a certain time. The Air Registration Board and the manufacturer also ask for such checks. Each time, the maintenance cost goes up and the check time cycle is affected. When the designer has done his best in the first place, and after the equipment has had initial testing and improving and has been bought by the airline, the only way in which the work set by the maintenance schedules can be reduced is to make the utmost use of experience in operation in extending the periods between inspection, adjustments, tests and cleaning and greasing operations. This means continual critical review of the work done, rapid development action on troubles arising, and rapid incorporation of modifications to develop the efficiency of the equipment. Adequate effort put into this work pays hand some dividends. "Trouble Shooting." Any system, however good, will fall down if the daily and hourly diagnosis of troubles is poor. The cost of maintenance on new equipment, instead of being steadily reduced, will stay static or even rise if rapid and intelligent diagnosis is not done. Troubles rise at all stages of the game; on the tarmac just before flight, while the aircraft is on a routine check, on overhaul, in the workshops. The accurate and expeditious diagnosis of faults and their precise location demands trained competent personnel, adequate test equipment, and flying equipment so designed that fault-finding is practicable. The airline must provide the first two of these and the manu facturer the third. Diagnosis—or more colloquially, fault-finding or "trouble shooting"—is directed at finding the location of the fault in the quickest possible time, so that it can be rectified in the most convenient manner, e.g., replacement of faulty components, adjustment or repair. Diagnosis is not intended to discover the root cause of faults, although it will sometimes expose them; this part of the work demands a totally different approach and may easily take weeks in complicated cases. The investigation of the root causes of troubles, defects and difficulty covers not only those experienced by the maintenance department, but also by others handling and using the equip ment, e.g., traffic, catering, and flying staff. It provides the material and experience for the alteration of equipment and techniques in service and also the vital experience on which requirements for new equipment can be based. Troubles sometimes arise, particularly with new equipment, in which routine rectification is not enough by itself without immediate investigation into the root cause; in these cases, the development staff is called in at once. This has two effects of economic benefit to the airline: in the first place it helps to "keep the aircraft flying"; and secondly the development staff get to know first-hand the sort of things that are really hurting the airline, costing it money and causing dislocation. Thus, from the initial occurrence of the trouble, there are two chains of action. The first is the diagnosis of the fault and its immediate rectification, resulting in the equipment being put back on the service in its original state, while the action taken is recorded so that subsequent investigation can trace back on what was done: the second chain is the establishment of the cause of the fault and taking action to eliminate its recurrence. The necessary development of new aircraft and equipment after they are designed is in three parts; maker's tests and trials, proving and familiarization trials, and development in service. Much has been written on the subject of the design and supply of equipment, so that it does not require development in service, e.g., components already proven to run long lives. The facts of life are, however, that in the air transport business, the quantities of new equipment likely to be sold are comparatively small, and all pre-service trials and testing will put up the initial cost of each piece of equipment. There is therefore an economic limit to the amount of testing and proving which can be done by the maker. This limit must, however, be sought and in our experi ence there are cases where insufficient pre-service testing has been done; on the other hand, experience shows it to be very unlikely that the most extensive bench-testing will provide an automatic long life in service with complete freedom from teeth ing troubles. The amount of proving of a new aircraft before service is also a matter of economics—it will cost a lot, for example, to do extended proving flying of whole aircraft. Yet there is no other way of seeing how the equipment will perform. On the Viscount and Elizabethan 200 hours' proving flying was done on each, apart from makers' trials and operators' training. Experience shows that no new aircraft of any size or complexity should be put into service with less than this. It is extremely important that this proving flying should simulate precisely the conditions of operation in all respects, and for this reason there is no doubt that the first operator should do it, however it is financed. Development in Service. This is a much more difficult and costly task, not even capable of solution by "just getting the money from somewhere." A separate development aircraft can only be used for tests and trials involving relatively few hours of flying. Development in service carries big financial rewards, but can only be done on the basis of many hours' use; the real proving of a new aircraft, therefore, demands many hundreds of hours in actual service. This is essential on all new equipment and yet is very difficult indeed to do. Any disturbance of standardized maintenance or flying schedule routines will be costly in manpower or in the time the aircraft is off service, yet a modification or trial of a new piece of equipment or change in technique may lead to very substantial reduction of maintenance costs or time off in service. More important, the reduction is not just an isolated case at one moment in time, but probably capable of recurring for the rest of the life of the equipment. We thus have the paradox that the maintenance and flight operating routines must be continually disturbed in order to discover or try out the very necessary means of improving them. Modifications are the core of development in service. It is a fact perhaps not appreciated by many that all proposed modifica tions can be judged on financial grounds. In B.E.A., no pro posal to alter either the aircraft or any part of the flying equip ment can get beyond the examination stage until the financial result likely to accrue has been assessed, and authorization given. The development engineers have been trained from the outset to think commercially and to produce a balance sheet for what they are doing, showing the cost, the economic penalties and the advantages. In our experience, the use of development engineers trained to think in terms of economics, and the insistence that all pro posals to alter equipment should pass through this system have resulted in enormous savings through the efficient control of modifications. No separate system of weight control is necessary. Any such system of modification control, however, is ineffective if the modifications receiving approval are not incorporated quickly. The traffic pattern of B.E.A. is highly seasonal. Although the summer peaks may be reduced in degrees by various means they are likely to persist. The heavy work period for engineering staff is therefore in the summer, and the problem we have not yet solved is how to deal with this situation most economically. The prospect of a solution has been confused by the introduction of the two new types so close together, and the extensive modi fication programme being performed on the Elizabethan. We have for some years employed the system of progressive maintenance, on which the aircraft never comes in for an annual overhaul, this work being broken down into parts done at one or other of four successive major checks. This enables a much more constant work load to be planned for hangars and work- *
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