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Aviation History
1939
1939 - 0627.PDF
MARCH 2, 1939 FLIGHT. 227 AIRWORTHINESS and the A.R.B. The G.A.P.A.N. Discusses an Interesting and Important Subject IF those who attended the discussion, held recently at the Royal Aero Club on the subject of Airworthiness and the Air Registration Board, expected to be told exactly where we stand under the new regime, they were mildly disappointed. The details divulged were few, but the impression was formed that the A.R.B. intends to adopt a friendly and by no means dictatorial attitude. And that is something to the good. The discussion had been arranged by the Guild of Air Pilots and Navigators, whose Deputy-Master, Capt. Rex Stocken, was in the chair. Dr. H. Roxbee Cox, Ph.D., D.I.C., B.Sc, F R.Ae.S., chief technical officer of the Air Registration Board, opened the discussion. He recalled briefly the history and development of airworthiness regulations. Before the war airworthiness did not exist as a distinct branch of aeronautics. In IQIO flying was prohibited within five miles of Charing Cross, but no steps were taken to ensure safety in flight. During the war the seeds of airworthiness were sown. These grew up at the Admiralty and War Office departments whose duty was the formulating of specifications. The word meant considerably more then than it does now. It meant, in fact, that the design calculations were carried out by the Service department concerned. Construction was, from beginning to end, inspected by Government officials. Recalling "The Snag" Soon after the war the basic airworthiness procedures were published in a volume known as H.P.806. The worked-out examples in HP.806 referred to a particularly awkward aero plane called the Snag. This book was the designer's guide to stress calculation. The basic volume, revised and enlarged, became famous as A.P.970, and was for a long time the.bible of the designer of Service aircraft. By 1932, however, the differences between civil and military aircraft became recog nised and a separate handbook for civil aircraft, known every where as A.P.1208, was produced. In other words, during the war period the responsibility for the strength of aircraft lay with the Government. Soon after the war the responsibility was s#hared between the Air Ministry and the contractor. The year 1923 saw the beginning of the " approved firm " system, by which certain firms were approved by the Air Ministry for conducting their own inspection of construction, under A.I.D. supervision. This form of approval has since spread to most of the industry and its associated firms. In 1928 another important step was taken, which shifted still more responsibility on to the shoulders of the constructors. It was in that year that the system of approved designing firms was introduced. The approved designing firm was considered able to make its own design investigations under the general super vision of the Airworthiness Department of the Air Ministry. In 1930 the approved designing firms were asked to guarantee the arithmetical accuracy of their calculations. - In the case of Service aircraft, the lecturer continued, there are no further important developments to record. In civil aircraft, however, the story continues, and a further stage w the emancipation of the designer can be deduced by com- panng civil and military requirements. The first impression one formed, and quite an erroneous one, from such a com- panson was that authority was more concerned for the safe carnage of bombs than for the safe transport of fare-paying passengers. A more correct deduction was that the civil aesigner was given a little more self-determination than the designer of Service aircraft. Cor n reXt imPortant change arose from the findings of the thV7 ^0lnmittee in 1934- That committee recommended that over tn airworthiness of civil aircraft should be handed of ren M ,aut°nomous executive authority, to be composed writers eTKtlVeS °f manufacturers, operators and under- Prin.jri +,Alr Council accepted the recommendation in the anth 1 ?r the tlme beinS restricted the supervision of protntv™ "ty (*e Air Registration Board) to design and andcarr mS?e °n °f airCraft UP to I0'000 lb- §"•» "**#* tion BoarHK er than eleven passengers. The Air Registra- inspectio, rrf6??n T°rk in APril- IQ37> was responsible for the Certifier! L .subsequent" aircraft and for the renewal of Dr R-?vk Airworthiness, irrespecti-ve of size. mitteeV r^T x stated, with reference to the Gorell Corn eals shonW v datlon that the system of " approved " authority that ^^S^' with the ARB" as the approving . LUd.T tne A.R.B. intends to extend this system and in the direction of placing as much responsibility for airworthi ness as possible on the shoulders of the constructor. By way of describing the working of the airworthiness system under the A R.B., Dr. Roxbee Cox took the case of a company designing and constructing civil aircraft. Normally the firm would apply to the A.R.B. for approval of its design and inspection organisations. Officers of the A.R.B. would inspect the organisations and recommend to the Board that approval be granted, possibly suggesting certain amendments of the organisations first. The firm's design staff would be assumed competent to report the results of its design investigations. It would be expected to discuss with the Board its design assumptions and methods, but would not expect the Board to check its calculations. The Board would expect the firm to supply a " type record." This is a document which, by reference to drawings, calculations and tests, describes the design, indicates the reserve strengths of structural members, and gives such other information as is necessary to prove that the design meets requirements. On the inspection side, approval would mean that the firm's organisation was considered competent to inspect construction under the general supervision of the Board's surveyors. While proceeding with a particular design, the firm would be expected to discuss assumptions and methods with the Board's officers and to keep in touch with the Board during the progress of calculations and any tests which might be necessary. Construction would proceed under the supervision of the Board's surveyors. In the past the official flight trials were generally done by R.A.F. personnel at Martlesham Heath. The A.R.B. does not, Dr. Roxbee Cox said, propose to establish a testing station for the present. Instead it was intended to compile a list of approved test pilots. From this list would be selected two pilots to conduct a particular set of C. of A. flight .trials. The final recommendation to the Secretary of State for Air would be based on the results of three sets of flight trials: One by the applicant's pilot and one by each of the two pilots selected by the Board for the tests. Dr. Roxbee Cox pointed out that the Board's pilots would be mainly concerned with the flying qualities. Performance tests, it was suggested, might be made by the applicant's pilot under the observation of the Board's officers. The drawing-up of the list of approved pilots was no easy matter, and the A.R.B. had asked for the assistance of the G.A.P.A.N. Mostly, experienced test pilots had their time fully occupied at present. Nevertheless, the Board hoped shortly to publish its list. He pointed out that the Board will lay down a schedule of tests which the pilots will be asked to make. The take-off requirements would be checked by a camera method, and the necessary apparatus was now in an advanced stage of development. One great advantage of it was that it would be transportable, so that it could be taken to the con tractor's aerodrome for the tests. He thought the transport ability should particularly appeal to the smaller firms. In conclusion Dr. Roxbee Cox asked those present to express their views on any particular aspect of the flight trials which they might consider important, and asked if they were satisfied with the present spinning tests, in which recovery must be made in two turns after spinning four turns; Did they think that spinning tests should be made at all on aeroplanes in the '' normal'' category ? The Discussion CAPT. F. DIGBY asked what the A.R.B. was doing about the question of ice formation in the carburetter. He thought it was time something was done. MR. J. LANKESTER PARKER said he was very much the " new boy " [he has but recently joined the G.A.P.A.N.—ED.]. He thought a great deal of unnecessary work was being done on spinning and stalling, and asked what "stalling" meant. He had asked the question recently at a meeting at which the Air Ministry was represented, and everyone present had a different interpretation of the word. He thought the G.A.P.A.N. would be doing good work by helping the A.R.B. to lay down appro priate tests. CAPT. H. S. BROAD thought they might substitute "fall" for '' stall.'' MR. R. A. C. BRIE pleaded guilty to having an anti-stall kink. He urged the A.R.B. to consider not only how many turns a machine should do in the spin and in the recovery, but also possible ways of avoiding the spin starting at all. He
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