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Aviation History
1974
1974 - 1902.PDF
FLIGHT International, 21 November 1974 LIGHT COMMERCIAL & BUSINESS continued from page 709 Beech considers commuter Beech is at an advanced stage in a 19-passenger commuter aircraft design study. The specification, which has been discussed with several US air lines, is for a 17,0001b gross-weight, stretched Super King Air, retaining the PT6A-45 engines and T-tail of the present model. Air London standby Air London of Gatwick and Baylee Air Charter of Jersey have agreed on a joint plan to operate emergency medical flights between the Channel Islands and the mainland using Aztec or Twin Comanche aircraft. The main requirement is expected to be the carriage of blood plasma in "life-and-death" cases. Airtruk production steady Production of the Transavia Airtruk is running at approximately 16 units per year and over 80 have been built to date. The order backlog includes five aircraft for Thailand and three for India. One of the two HS.748s in commercial use in Canada, this aircraft of Gateway Aviation operates charter flights in support of oil companies. The company intends to add another HS.748 to its fleet of 26 aircraft, which includes DC-3s and Twin Otters UK air-taxi flying increases The number of air-taxi operators in Britain increased from ten to 50 during the past 18 months and their 200 aircraft represent one-third of the UK air transport fleet. They had flown 66,000hr during the past year, covered 15 million miles, carried 150,000 passengers and 1,000 tonnes of freight. This was the summary given by Eric Thurston, chairman of the Air Taxi Operators' Association, at its annual dinner. The association was now preparing a code of practice and had established good working relations with the Civil Aviation Authority. The statistical information require ment of the Class 7 operating licence had just been re duced from days of work to one form, though it still took days of work to establish a 30p charge under the variable- route charging system. The Association was a member of the general aviation airworthiness committee and the London Airport scheduling committee, but, surprisingly, not yet of the civil aviation advisory control committee. Flight-time limitations were being studied and operators were once again able to use unlicensed airfields with aircraft of less than 6,0001b gross weight. Mr Thurston felt that the CAA should not have to pay its own way and pointed out that the Government paid for motor transport regulatory activity. The association wanted to see greater cost-effectiveness in the CAA. Beplying, Air Marshal Ivor Broom, Controller, National Air Traffic Services, noted that ATC service outside con trolled airspace was still free of charge, "so far". His organisation had to respect the official policy that the public must not subsidise the travelling passenger. Szydlowski upholds fixed turbines "The abandoning of the single-shaft turbine—which was and still is a brilliant success in the turboprop field—for the multi-shaft solution is, in my opinion, a costly technical error; the money could have been invested in research towards improving turbine/compressor performance." From M Joseph Szydlowski, founder of Turbomeca, whose power- plants have done so much to uphold the helicopter and business aircraft market, these were fairly predictable sentiments. They were in fact the keynote of his Sir Henry Boyce lecture last week to the Derby branch of the Boyal Aeronautical Society. The Bolls-Boyce Derby division was, of course, the birthplace of three-shaft engine technology, beginning with the Trent and BB.207, so his choice of topic, "The Fixed Shaft Turbine with Constant Speed and Variable Torque," was not without some piquancy. He went on: "I am moreover convinced that the develop ment of transport aircraft has taken the wrong turning by putting the emphasis on speed to the detriment of economy —a factor which should never have been neglected and which has become predominant due to the petrol crisis. In my opinion a single-shaft variable-pitch fan could be designed with a suitable bypass ratio to accommodate three requirements: well-matched take-off and cruise thrust, best fuel consumption at Mach 0 6-0-8 and reason ably sized fan-duct diameter." Szydlowski's preoccupation with constant-speed engine operation stems from 1946, when he became convinced that it offered safety, economy and simplicity. He excused his company's entry into the free-turbine field by observing that not everybody shared his opinion of fixed turbines, and that "I am, however, still obliged to manufacture engines, the technical and commercial success of which I do not deny, whilst being persuaded that more rational solutions exist." The speaker described the application of the fixed- shaft Astazou XVIII to the SA.360 Dauphin, noting that the rapid response of this engine to throttle demands was largely responsible for the impressive climb acceleration of this helicopter. Considerable improvement had been made with the free-turbine engine, "but they have never attained the power response available with fixed turbines." One of the Turbomeca's most significant developments was the Astafan. No fewer than 300 tests were run with <m ^WN@?W&'&&: fans of 22in, 23-6in and 27-6in diameter, with 21 different reduction ratios to step down the shaft speed of the three engines used in the tests—Astazou XVI, XVIII and XX. Total mass flows varied from 69-41b/sec to 1371b/ sec, with equivalent fan speeds of 11,770-7,300 r.p.m. The tip-speed Mach numbers varied between 1 • 04 and 0 • 744 and fan pressure ratios between 1-16:1 and 1-41:1 were investigated. Bypass ratios varied between 14:1 and 6:1. The speaker showed graphs of predicted and actual thrust as a function of flight Mach number to illustrate the close agreement obtained between ground tests and flight trials of the company's modified Aero Commander.
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