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Aviation History
1949
1949 - 0173.PDF
JANUARY 27TH, I949 FLIGHT The minimum distance between Rotorstations, showing the effect of possible navigational error. Mr. Rowe said that the essential features for helicopter air trafficcontrol were the means of point-to-point navigation with high accuracy in terms of time, means of rotorstation recognition, andsafe let-down in conditions of low visibility. He then gave the advantages of the Decca Track Guide system which, he thought,gave the basic means of accurate navigation. It was envisaged that a number of rotorstations would be used instead of a singlemain station. Each would handle the traffic from a sector, the angle of the sector depending on the density of -the traffic in thatgeneral direction. Thus the main distances of the stations from the city centre would depend on the minimum safe distance betweenany pair. Mr. Rowe then gave a brief outline of possible let-down and take-off procedures, which required very accurate flying.The aim was to keep the radius of procedure turn to as low a value as possible while ensuring physical separation duringthe take-off and landing manoeuvres. Schedules would be arranged so that normally suchmanoeuvres would not take place at the same time at a given rotor-station. Traffic control en route relied upon high separation byquadrantal rules or otherwise, com- bined with scheduled flying allalong the route by reference to Decca Track watch and mileageindicator. Economy was undoubtedly themajor problem to be solved before the helicopter could play its fullpart in the pattern of transport, and further that the machineitself, and its operation, the plan as a whole should be considered.Mr. Rowe felt that initially the cost of operation, the capital andrunning costs of rotorstations, an«I of all navigational aids includingAir Traffic Control should be .kept as low as possible. In analysing present operatingcosts he referred to two operations of the B.E.A. Experimental Heli-copter Unit, one of about five weeks' duration carrying dummymail, and the other of four months carrying live mail. Total flying time was 1,332 hours, of which 1,019 was on the threeS.51S and 313 was on two Bell 47BS. The rate of utilization was low but the average total operating costs of the S.51 was about^28 per flying hour made up in the proportions of standing charges 33 per cent, maintenance and repairs 22 per cent, flying operations23 per cent, station costs and headquarters charges 22 per cent. Standing charges could be reduced by increasing the utilizationto 1,200 hours and making necessary adjustments in other factors. Based on an average capacity payload of 750 lb androute „ speed of 65 m.p.h., the operating cost per capacity ton-mile was £1 5s. Such charges would make regular scheduledpassenger services uneconomical in this country, and the main factors involved in making an overall reduction of about one-quarter were, increased cruising speed to diminish the effect of adverse winds, larger size, lower first cost, maintenance organizedto increase utilization and a machine with good basic qualities. In amplification he thought that we should aim during the nextfew years to achieve a cruising speed of 115 to 120 m.p.h. at 60 per cent take-off power and weak mixture. That would make practicala schedule of 100 miles in the hour as an average, which would give savings of time worth while paying for. The prospects ofobtaining these were bright since the Fairey Gyrodyne had flown at 124 m.p.h. using less than full power. The size of an aircraft BBTWUU Kamm. t For night landing, wind direction and illumination was given by the Wiggimac in which the Circumference of the illuminated area was marked by a band of white on the ground. affects operating economy in that the consideration of potentialtraffic may demand a vehicle smaller than would be most econo- mical judged on technical grounds alone. There was, he said, aminimum size and a tentative conclusion was for a 12- to 15-seater, but the actual figure would depend entirely upon the detailedeconomics of any specific design. Little information was available of the probable first cost ofcommercial helicopters, but taking a rough figure of 1,000 lb all-up weight per passenger, first cost was of the order of £3,000 perpassenger. Taking a total life of 12,000 hours the cost per hour was about /0.35, representing 15 per cent of a fare of 8d per mileThat was a very high proportion of the total cost and its reduction . -..::-:.-.-:, ' .-".. was of great importance to the success of helicopter commer-cial operation. The operator he said, would be responsiblefor choosing the right size of vehicle and the luxuriousstandards associated with fixed- wing transports would have togive way to a more austere type of seating appropriate toshort stages. Mr. Rowe was convincedthat a revolution was needed in present-day methods ofmaintenance if high utilization and cheap maintenance wereto be achieved. He described the inspection method as un-economical and highly un- scientific and a process whichrested essentially on lack of knowledge. He proposed that~ it should be replaced by a system of sealed servicing in which parts and componentswould not be touched save for normal maintenance until they had completed a predetermined life. He thoughtthat such a method would reduce costs of air operation and that the helicopter offered a particularly fruitful fieldfor its application. Maintenance, he said, would become a simple routine, reducing labour to a minimum, one in which agiven volume of traffic could be handled with the least number of aircraft through high utilization, and the high reliability implicitin the system. The cost of spares would be reduced because useless spares would not be purchased and the correct proportion of sparesactually needed would be known. Economic Maintenance Necessary Referring again to the efiect of utilization on economy, Mr. Rowestated that whereas fixed wing transport with block speeds of 160-170 m.p.h. were utilized for 1,500-2,000 hours per annum, a heli-copter would be required to do 2,500-3,500 hours to achieve the same aircraft miles per year. It was therefore imperative thatmaintenance should be simple and mechanical reliability very high. Helicopter operation would depend upon an adequate network ofground sites covering the country. Thus the great towns would be directly linked by a shuttle service whereas lesser towns wouldbe linked by a circuitous stopping service. Such widespread use would take some time to develop but Mr. Rowe emphasized therelation between high utilization and frequency and the corollary that an adequate number of operating sites was needed in any areain which services were to be developed. The cost of rotorstations would depend fundamentally on the size but would be effected byposition, whether it was elevated and the complexity of operating essentials such as lighting and other aids, maintenance and ser-vicing. Elevated sites without nearby obstructions could be much smaller than ground sites and may be much easier to provide nearthe city centres. The whole design of such sites was intimately interconnected with the. ' .... foreseen pattern of helicopter service and .• the problem of Air Traffic Control. Allow-ing for aircraft circumscribed by a circle of 100ft diameter and errors of wind andpilotage, the area should probably be of the order of 120ft x 120ft as a minimum, withadditional space for parking. An, attempt had been made to assess costwith generous assumptions for the number of staff required, ground rent and the costof ground aids. The resulting charge per landing was £10, assuming a low utilizationof ten landings per day and with all costs supported by the operation. At a morereasonable utilization of four per hour the charge would be £2 10s per landing. Sum-ming up, Mr. Rowe said that there was a good prospect of commencing operationsabout four years hence. He thought that the greatest doubt was the development ofsuitable power plants, -but since our future strength in this country was likely to bein the development of the internal com- bustion turbine engine he suggested that wemust quickly begin to apply those to helicopter development. The provision ofrotorstations was necessary in advance of the operations, and Mr. Rowe was con-vinced that in order to have rotorstations B 2S
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