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Aviation History
1954
1954 - 0395.PDF
12 February 1954 187 HELICOPTER FORUM Some Further Questions and Answers from the Helicopter Association s Brains Trust LAST week, under the above title, we gave a number of the questions asked at the Brains Trust held in London "^ on January 22nd by the Helicopter Association, together with summaries of the answers by the team of experts. This team consisted of Mr. L. G. Frise, technical director and chief engineer of Percival Aircraft, Ltd.; Dr. G. S. Hislop, chief designer, helicopters, of the Fairey Aviation Co., Ltd.; Mr. K. Reed, chief helicopter test pilot of Saunders-Roe, Ltd.; Mr. J. Shapiro, aviation consultant and previously chief technical officer of the Cierva Autogiro Co.; and Mr. R. H. Whitby, performance and analysis manager of B.E.A. Mr. Raoul Hafner was prevented at the last moment from attend ing, and his place was taken at short notice by Dr. Hislop. The Editor of Flight occupied the Question Master's chair. Below we deal with the remainder of the submitted questions, and the panel's replies to them; finally we summarize a number of questions put "from the floor," together with the answers. In view of the high operating costs and length of time taken by even experienced pilots to become proficient on heli copters, do the team consider that a synthetic trainer would be a practicable aid? If so, should there be a simulator for each type of helicopter or a general-purpose trainer; and in either case, should the simulator be built for visual or instrument flying, or both? MR. REED said that he thought it was wrong to say that con siderable training on helicopters was required. That point had been overdone. There were now a number of helicopters being operated, and consequently more pilots were being required than in the past. One of the best examples to take was the Royal Navy. So far as their helicopter pilots were concerned they were fully operational after 30 hours. He did not intend to give the impres sion that 30 hours was enough for a civil operator, but an indica tion of a certain standard reached in that number of hours. He did not think that a simulator would be of any great advantage. With more stable helicopters it would be much easier. MR. WHITBY said that B.E.A. liked to rely on more than 30 hours before putting anybody on the job on his own; they felt it should be the best part of 100 hours. Simulators were very expensive things and one had to have more or less "a production of pilots" before one could justify them. They obviously would not give a pilot primary training in helicopters. They might help to convert him to a certain type and save time, but he would actually need to do the exercises in a real aircraft—not just an armchair. In view of the recent statements in the Press concerning Sabena's expanding sphere of activities with their passenger- carrying helicopter services, does not the team think that in order to avoid being left at the post it would be better for B.E.A. to operate immediately with well-tried American heli copters, pending the arrival of suitable British ones? DR. HISLOP said he was in a cleft stick. Sabena were expanding their services, and he thought they would be followed by other European operators. According to a Sabena operations executive it was a good proposition for the time being. Very much to his personal regret, he thought it would be some time before there were British helicopters available to carry passengers economically over the networks which were envisaged, and it meant that B.E.A. stood in a position to find their traffic being filched by the other operators. Their problem, then, was whether to stand by their decision to keep the nucleus of their knowledge in being and then to expand, or to hold fire until British designs came along. It was a very difficult question to answer off the cuff, but he had a feeling that it might be best to extend their operations with larger helicopters and attempt a more economical service if they could find a suitable traffic pattern. They ought to do that for the next couple of years, because otherwise the rate of experience would die away and they would find themselves at a disadvantage when the time came when British helicopters were available. MR. WHITBY said that at this very moment there were no well- tried American helicopters suitable for the job, but at the rate of development it was likely they would be available before British types. If there was any possible means of speeding up development of suitable British transport helicopters he would be delighted. MR. REED said he did not understand Mr. Whitby's remark on no well-tried American helicopters. We must remember that they were using American aircraft. He asked if their degrees of safety were lower than British requirements? Mr. Whitby replied that the question was of a large transport helicopter—larger than the ones we were using at present, which, incidentally, were British. He thought that twin-engine safety was an absolute essential for any extended helicopter services which could get into city centres and had any hopes of being commercial. If the helicopter did not make use of its slow-speed properties it was obviously less efficient. DR. HISLOP said that any British helicopter competing in Euro pean networks with Sabena would have to go across the sea. Sabena used S-55s and operated across the land all the time. Should an engine fail a helicopter could put down on land. If B.E.A. endeavoured to keep abreast they must cross the water, and to schedule services regularly across the Channel on one engine was a ve*y difficult operation to take on. Does the panel consider that slow-speed, high-lift, fixed- wing aircraft constitute a serious threat to helicopters employ ing the same engine or engines? MR. FRISE thought it possible to do practically the same job with the same engine in the two types of flying machine. One could carry the same payload and fly the same distances with the same fuel, but in one the minimum speed was about 38 m.p.h. and the other it was zero. The extra structure-weight that had to go into the fixed-wing aircraft to make it come as near as 38 away from zero had used up what would normally be the extra payload that could go into a fixed-wing aeroplane. One accepted the fact that the helicopter, flying sideways on a propeller and being rather a crazy affair altogether, was not so efficient as a fixed-wing machine; but the moment one tried to make the fixed wing come nearer to the helicopter one sacrificed the difference. MR. SHAPIRO agreed entirely. He thought it much more sensible to go to the helicopter for everything from zero speed. Do the panel regard noise as a problem, and if so, what do they intend to do about it, on behalf of people outside the helicopter and those carried in it? MR. FRISE said that the yardstick used in the South Bank tests showed, surprisingly, that the existing method of using a piston engine with normal exhaust system was unacceptably noisy. He would have imagined that people who commuted daily in tube trains would have become toughened to noise. Noise had become a kind of modern Aunt Sally for constituents to consult their M.P.s about, and therefore there would be regulations laid on. There was no question that there were methods of making the helicopter less noisy. Already experiments had been made to demonstrate that a gas drive could be less noisy. The total energy being put through a low-pressure gas system gave less noise internally and externally than would the small proportion of exhaust from a free-turbine drive. That, it was hoped, would soon be demonstrated completely, and not just by calculations. The helicopter only started to earn its keep when it pottered about in built-up areas where a lot of ratepayers lived. He had recently come across a case where a certain company in America started a route from the centre of a typically skyscraperish town. Within a week all the tenants of these big blocks of offices went in a body to the mayor and said they were going to pack in at the end of the week if it were not stopped; and it was stopped. That was one example of people who paid money to occupy premises in a big city objecting to the sudden introduction of the noisy helicopter. Noise was a talking-point, and designers must face up to it from the very conception of the job. Questions "From the Floor" THE first question was with regard to the application of the » turboprop power unit to the single-rotor helicopter and the provision for anti-torque at the same time. MR. FRISE said that the turboprop power plant with a rotor being driven instead of an airscrew was a next step, and it would take its place in heli copter development. A lot of thought was being given to the matter, but he believed there was no question that the free turbine, with the weight of clutches avoided, was the obvious next step. There was a shortage of turboprops in the power range which could be expected to go into existing helicopters immediately. He did not think that the jet exhaust would contribute greatly to planning or that it could be used easily for overcoming the torque of the drive. To an additional point regarding the part which blade-tip
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