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Aviation History
1967
1967 - 0019.PDF
FUGHT International, S January 1967 21 Certification: the New ARB Rules ON MARCH 21 LAST YEAR the Air Registration Board madeproposals for simplifying light-aircraft certification andmaintenance procedures (Flight, March 17, page 444). Three major changes were suggested: (1) the division of all powered aircraft of under 6,0001b gross weight into two categories for Certificate of Airworthiness purposes: "General Purpose" for all aircraft designed, built and tested to the full airworthiness standards regardless of whether used for private or hire-and-reward flying, and "Restricted" for ultra-light, amateur-built and experimental aircraft (2) The acceptance of a specified minimum amount of performance and operating data, produced by the manufacturer in any convenient form, rather than scheduled performance to the standard required in the case of large transport aircraft. (3) The introduction of a maintenance scheme based on manufacturers' recommenda- tions, together with a general inspection of the aircraft after each 100 hours' flying and the renewal of the C of A every two years. This would take the place of the present one-, two- and three-year Cs of A each with its own maintenance regula- tions. As briefly recorded in Flight for December 1 last, after analysis of invited comments the board has chosen to imple- ment the first two amendments with minor alteration. But the simplified maintenance scheme has been found unacceptable. Instead, a modified form of the RAeC/ABAC maintenance scheme will be introduced for all aircraft in the general-purpose category. The C of A associated with it will be renewable every two years, and there will be 50-hour, 100-hour and two- yearly inspections linked with simplified schedules of main- tenance. A handbook describing the new requirements is to be published by the ARB and it is hoped to start implementing the regulations on April 1. The following comments on the ARB plan are by Mr L. S. Whicher (although he is a member of the board they do not necessarily represent ARB policy). * * * After analysis of all the comments received [writes Mr Whicher], it seems clear that the first two proposals, with minor amendments, are both welcome and acceptable to the great majority of users. The introduction of a "General Pur- pose" category will put an end to certain anomalies and obstacles regarding the legal use of the aircraft, and the acceptance of the "owner's handbook" type of publication, pro- vided it meets certain minimum standards, will avoid the costly preparation and formal approval of a flight manual. However, the proposals concerning maintenance, which were based to a large extent upon current practice in America, are clearly not unanimously acceptable in this country. Although there is a wide divergence of opinion on this subject there is also a clear indication that, for the time being at any rate, a standard form of maintenance schedule, applicable to any aircraft of up to 6,000lb and published by the Air Registration Board, would be a better solution. This schedule would be based on a C of A renewed every two years. It is not unprofitable to look carefully into the reasons for these conclusions and to examine the philosophy of the two alternative systems of maintenance. No one will argue against the fact that it is the duty of an airworthiness authority to control maintenance at an optimum level consistent with safety, i.e., aircraft must not be under- maintained, thereby reducing safety, or over-maintained, thereby causing unnecessary work and expense. The control system must ensure exactly the right amount of maintenance —no more and no less. To achieve this target in the field of scheduled and semi- scheduled transport operations is relatively easy, because the annual utilisation, the quality of the maintenance staff and their facilities, the routes flown and the general reliability of the equipment used, are all factors which can usually be assessed with a high degree of accuracy. However, when it comes to the maintenance control of light aircraft engaged in general aviation the airworthiness authority has a far more difficult task and, if it makes detailed schedules of maintenance mandatory for such aircraft, it will inevitably miss the target in the majority of cases. Most of the aircraft will be either under- or over-maintained, and only a few will receive the optimum maintenance consistent with safety and economics. This is because the various factors affecting maintenance are completely unknown collectively and are infinitely variable, and the use (or misuse) of the aircraft both in the air and on the ground can vary between such wide limits. The American airworthiness authorities, with over 120,000 light aircraft on their books, long ago evolved a system whereby the responsibility for maintenance was placed fairly and squarely on their licensed engineers, approved repair stations, and the aircraft manufacturers and owners. These between them are responsible for maintaining the aircraft on the basis of the manufacturers' recommendations, together with inspections after every 100 flying hours, and the amount of work and depth of the inspection is to a very large extent decided by the licensed inspector. The philosophy behind this is that the inspector is the only person in a position to decide what maintenance work is required on a particular aircraft at any one time. This system, with local variations, has been adopted in various Commonwealth countries, notably Aus- tralia, and also by a number of airworthiness authorities in Europe. Its value is becoming increasingly widely recognised because such a large proportion of light aircraft throughout the world are of American origin. The ARB's proposals of March 1966 advocated the use of a similar system in this country, but with modifications, in that the upper weight limit was to be 6,0001b and the C of A was to be renewed after inspection of the aircraft by the Board every two years. Why do these proposals appear to be unacceptable in this country? The reasons seem to be as follows: — (i) The majority of licensed engineers and repair organisations have become to used to maintaining and overhauling air- craft to a fairly detailed schedule of work, monitored by the board, that they are not "conditioned" suddenly to decide for themselves the depth of inspection and amount of work necessary at the lOOhr inspection, (ii) In America, because of the large number of aircraft in- volved, a highly organised maintenance system has been evolved by the manufacturers, through their many approved repair stations and licensed mechanics. In Britain there are small numbers of a great variety of types of imported air- craft, so a legal obligation for maintenance strictly to manu- facturers' requirements would throw a heavy burden of responsibility on the individual licensed engineers and some of the smaller repair organisations. The ARB, by the very nature of its constitution, does not institute procedures or change requirements unless they are generally acceptable to those who have to abide by them. So it follows, at least for the time being, that the March proposals affecting maintenance will have to be abandoned in favour of a standard schedule produced by the board. I am personally convinced that, from the long-term point of view, the problem has not been completely solved; sooner or later, when conditions permit, we must come into line with international practice: only in this way will the maintenance cost of light aircraft be reduced and the licensed engineers regain their rightful place in general aviation. DIARY Jan 5 Institute of Transport, West Middlesex Group: "Air Safety—The Airline Pilot's Viewpoint," by Capt L. Taylor. Jan S RAeS: "A Young People's Guide to the Concorde," by E. H. Burgess; 4 Hamilton Place, London Wl, 3 p.m. Jan 5 RAeS Southend Branch: "Modern Planning Methods and Computer Techniques as Applied to Aircraft Maintenance," by E. Everett; Queen's Hotel, Westcliff. 7.45 p.m. Jan 10 RAeS: Joint meeting with 1EE; Savoy Place, London WC2, 6 p.m. Jan 10 RAeS Test Pilots' Group: "Inertia Cross-Coupling Effects," by W. J. Pinsker and J. Dell; 4 Hamilton Place, London Wl, 6 p.m. Jan II Kronfeld Club: USAF films, "Supersonic Thunderbirds" and "Quick- Span"; 74 Eccleston Square London SWI 8 p.m.
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