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Aviation History
1950
1950 - 2218.PDF
FLIGHT, 21 December 1950 603 the chief test pilot to provide facts andnot opinions in his test reports and made a habit of flying whenever a basicchange had been incorporated in the empennage set-up—and this in spite ofthe fact that the test pilots uncon- sciously did their best to increase theirprestige by making the ride as uncom- fortable as possible. The crucial decision was made quitesuddenly. The chief designer had been reading a test report in which the find-ings were strangely familiar and had sent for the aerodynamicist and theexperimental manager. It appeared that elevator development had gonefull circle and that the configuration then being tested was exactly thatwhich had been tried with only limited success about three months previously—the configuration, in fact, on which the production drawings had alreadybeen based. He sent for the chief draughtsman and the productionmanager. Within three hours the discardedinitial-production tailplane and eleva- tor were being assembled on the firstproduction aircraft and the riveting guns were chattering again on thework in the various empennage jigs. Four days later the aircraft waswheeled out for engine runs. Work- ing overnight, the inspectors passedit for flight thirty-six hours after- wards. The test crew had neverstarted work so early in the morning; the chief designer was to have flownwith them but they were airborne be- fore he had reached his office. Notthat it mattered; the first flight would not have told him much and therewere a hundred-and-one things to be checked in a new aircraft before anykind of start could be made on serious elevator assessment. However, the initial findings werepromising. At normal loadings there was a change for the better in thecharacteristics and, as the test work proceeded, hopes rose. Several changeswere made in the tab-gearing ratios and one to the ratio between the eleva-tor's up and down angles; but these were, so to speak, merely gilding thelily. The thing was miraculously '•strode vigorously through the drawing office," right; there was a very decent degree of stability at loadings more aft than had ever been attempted before, and with the e.g. at the forward "paper" limit there was ample control, with only moderate stick forces, in the most extreme landing conditions. To cut a long story short, the first production aircraft was delivered, witha full Certificate of Airworthiness, a whole week before the contractualdeadline. Now the curious thing is that veryfew people in the firm—except those directly concerned with control devel-opment—seemed to consider the result to be in any way remarkable. Maybethey took it for granted that the test team and the A.R.B. had previously t ". . . as uncomfortable as possible." been too fussy, or they had learnt to accept without inner comment the idiosyncracies of flying machines. No- body outside the little group directly concerned asked just why the produc- tion aircraft, with the same old dis- carded elevator set-up, should so miraculously have got over its stability troubles. It was the public relations manager —a serious chap with a superficially cynical manner, but a passion for col- lecting all the facts before bursting into print or words—who told me all about it when the story could no longer make news. There had simply been a mistake in the drawings. Whereas the prototype's tailplane and elevator had been hand- made from the original project-office drawings, the first production aircraft's empennage had been made in the assembly jigs from the productiondrawings—and these, it transpired, dif- fered in at least one vital particular.Following some indication of fatigue trouble, a certain amount of minorinterim redesign work had been carried out on the elevator hinge-brackets, and when the production general-arrangement drawings werefinalized the hinge line had moved quite appreciably further aft. So the elevator had been accidentallygiven, in small measure, something for which the chief test pilot had alwaysbeen clamouring—back-set hinges. With this fractionally increased " built-in " aerodynamic balance for the eleva- tor, the differentially geared tabs, whenthe ratio had been duly readjusted on the early production test flights, had aless impossibly wide variety of condi- tions with which to cope. No doubt,too, the inevitable differences between the prototype and production trailing-edge contours had, for once, gone the right way, and later measurementsshowed the tatlplane incidence to be slightly more negative than in theoriginal design. Such variations are normal in aircraft manufacture andmay have had some bearing on the total improvement—but undoubtedlythe cumulative drawing error did the trick. I doubt if the draughtsman respon-sible knows of his error. Certainly, nobody gave him a packet of cigarettesfor saving the situation—but, on the other hand, nobody even suggestedthat he should be given his cards. ". . . the draughtsman responsible ..." Lamploug Li IX >IR FRANK MUST LOOK TO HIS LAURELS Jt/"\R so we thought last week J ^ when, idly thumbing through i a Flight Manual of 1910, we were stopped in our tracks, so to speak, by the startling advertisement re- produced here. The unequivocal statement demanded instant inves- tigation, so to the bookshelves we went; and almost before the dust had settled we were faced—on page 698 of Flight for August 27th, 1910 —with an anti-climax. It seemed that what Mr. Lamplough and his son had in fact contrived was a sort of four - cylinder, eight - opposed piston swashplate engine of tur- bine-like proportions. C'est mag- nifique (we reflected, a little sadly) mats ce n'est pas la turbine a gaz. I AM PI A.. •... INlhRNAl- COMBUS1 IOV WIYHOV Tl RMNLir.
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