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Aviation History
1947
1947 - 2002.PDF
562 FLIGHT NOVEMBER 13TH, 1947 s CORRESPONDENCE The Editor does not hold himself responsible for the vtews expressed by correspondents. The names and addresses 0/ the writers, not necessarily for publication, must in all cases accompany letters. AUTOMATIC PILOTING Essentials of a "Safe" Auto-pilot 'HTHE fact that the Directoi and General Manager of Smiths•A- Aircraft Instruments, Ltd., should himself reply to my letter is gratifying, as it shows that his organization realizesthey cannot afford to be complacent about automatic flight, but I would hasten to add that my suggestion of complacencywas aimed not at the manufacturers of the S.E.P.i, but at those who made little of the American achievement insteadof recognizing it on its true merits. Quite obviously, Mr. Morgan's company is fully appreciative of the difficulties over-come during thi? flight. I would like to reply to points raised in his letter as follows:* (1) Has a completely automatic approach and landing with- -out human Gontrol in the air or on the ground actuallybeen achieyed»at B.L.E.U.? * (2) Since4;he S.E.P.i requires the crew to manipulate pitchtrim antfaltitude controls, it does not provide completely automatic1* control for instijrm.ent approach and landing.These, I submit, are essentials, not refinements. If the human pilot has constantly to cdfrect for trim changesand altitude changes, then he might as well fly the air- craft himself, and we are losing sight of our aim ofscheduled flights in any weather conditiojj.. (j) What is a sale automatic pilot? It has to make coarsecontrol movements at approach speeds to keej» the air- craft on the beam. Such control movements are theresult of signals generated and there is always the" possi- bility of incorrect signals being generated due to mal-functioning. The A-12 has always provided that any foreseeable failurewill cause the gyropilot to be automatically switched "OFF" or that nil control will be applied. Does the S.E.P.i go furtherthan this? The problems to be overcome to enable aircraft to operateregular schedules under all weather conditions are still numerous, and all readers will, no doubt, be more than pleasedto note the degree of optimism for, and the vigorous pursuance of, the solution to these by the instrument companies inEngland. Note well Mr. J. T. Bain's remarks in the third British Commonwealth and Empire Lecture, '' The greatestof all evils in airline travel is the lack of ability to maintain schedule." " B " LICENCE PILOT. SPITFIRE REPAIR IN FRANCE Groundwork by Air Service Training WE read with interest your article by Mr. King on "AView of France," in which he writes of the French air- craft factories. It is noted that he has omitted to mention AirService Training, Ltd., which was the first British aircraft factory to send technicians to French factories, and it is hopedthat a few words on the subject will not come amiss. In December, 1944, we were approached by the then Ministryof Aircraft Production to assist in the re-habilitation of the French aircraft industry, A.S.T. having the largest Spitfirerepair organization in the country, and in March, 1945, after a survey visit by Mr. H. W. Sidwell, our general manager, Iwas appointed technical adviser to S.N.C.A.N. at Les Mureaux, who were to repair Spitfire aircraft for the French Air Force.The section of the works allotted for fuselage repair was with- out a roof and the floor was cratered with bomb holes, andit -was some time before materials could be obtained to do the necessary repairs, but we went ahead with the floor levellingand carried on the aircraft repairs in another hangar. It was decided that the first aircraft should be a minorrepair using components repaired in England. This was com- pleted in fairly good time, but the French workman had suc-cessfully used a '' go-slow '' method whilst working for the Germans, and owing to the shortage of food was reluctant toincrease his pace until conditions had improved. However, the first aircraft was completed and when Jack Storey, whowas our chief test pilot at the time, came over to fly it, only minor snags were reported and celebration was made in theusual French manner. When V. E. Day came we had completed a number of air-craft and had a production line going. In fact, their input of pjrcraft was dwindling and they were looking around for additional work. Vickers-Armstrongs, who at that time wereinterested in the factory for business reasons, decided that they would like to take over the Spitfire repair after lease-lendterminated, and on November 1st, 1945, it was handed over to the Vickers-Armstrongs representative. It will be observed from the foregoing that Air Service Train-.ing, Ltd., did the original organizing and successfully com- pleted quite a number of aircraft during the eight months inwhich the Spitfire repairs were under their control. Service and Publicity Manager, R. J. WOODHAMS,Air Service Training, Ltd. FUEL CONSUMPTION WHILE "STACKED Pilot Can Cope if Warned Well Ahead T WAS much interested in the article under the heading of -*• "Casual Commentary," published in your issue of the 23rd of October. Your contributor has drawn attention to the necessity for improving the airport controls before turbine powered civil air liners can be operated. This is, as he rightly points out, an urgent problem as there is little hope of the consumption of turbine powered aircraft, under conditions of " stand-off " when waiting their turn to land, being brought down to anything like a comparable figure to that which is obtainable on piston engined aircraft. A distinction must, however, be drawn •been propeller turbines and jet units. propeller turbine engines the specific fuel consumption depends mainly on the percentage of the maximum power at which they are run, and it is not very sensitive to aircraft speed. It follows, therefore, that if some engines can be shut down and the rest run at comparatively high power, the total consumption when stacked up need not be prohibitive. Obvi- ously this would not be an acceptable method on a twin-engine machine, however reliable the engine starting might be, but there can be no operational objection on aircraft like the Saunders-JRoe boat or the Brabazon which will have 10 and 8 Proteus engines respectively. While the propeller turbine cannot approach the flexibility of the piston engine, the type in which the compressor is driven independently from the propeller will always give a good effi- ciency if the compressor is run close to the maximum permis- sible continuous speed. At this speed the B.H.P. can be varied over quite Wide limits by changing the altitude. For any propeller turbine driven aircraft there is an altitude which will give the maximum speed and another and higher altitude which will give the optimum air miles/gallon. In oper- ating between these two heights, it is possible to make quite large variations in speed without a very serious change in air miles/gallon. If, therefore, the ground control can give the pilot reasonable notice of when he will be allowed to land, he should be able to exercise quite a lot of control over his time of arrival without seriously increasing his fuel consumption, and by this means the necessity for excessive '' stacking-up" should be avoidable. Your contributor also refers to the necessity of continuing piston engine development and with this I am in comjw| agreement. Jie goes on, however, to make some comparisons between the overhaul periods obtained on British and Ameri- can piston engines, and to state that even the "paper" figures on British engines are rarely, if ever, reached. Everyone who has been associated with civil air line opera- tion knows that the attainment of long overhaul periods and reliable operation can only come as the result of experience, and if the current overhaul periods of established engines, whether they be British or American, are considered in relation to the time for which they have been in service, it will be seen that British engines do not compare unfavourably. Since the war, the overhaul period of the Bristol Hercules engine has twen progressively increased in 100 hour stages as experience has been gained and no final limit has yet been established. On earlier marks of engine, we have established a period of 700 hours between major overhauls when operating under the severe conditions associated with flying boats and at a normal cruising power of about 65 per cent of M.E.T.O. *n spite of this quite exceptionally high power, our records slw* that 89 per cent of the engines removed from the aircraft are removed as time-expired and not as the result of failure. The Bristol Aeroplane Co., Ltd. B. G. MARKHAM,
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