British Overseas Airways Corporation) said that those concerned with air transport had been very conscious of their social obligations in regard to the problem of noise. As early as 1952 their first draft specifications for an aircraft to succeed the Comet had included the reduction of air-to-ground noise as one of the leading criteria. Knowledge of the problem at that time had not been sufficient to enable them to tell the designers what were the criteria of public acceptance, nor could the designers tell them what would be the effects on economics and performance of any attempt to meet hypothetical standards. This had been a difficult position for operators and designers who had then been planning for the late 1950s and early 1960s. 57. In the last five or six years, that position had changed a great deal because of the work of various authorities, including in Britain the Author himself and Lighthill, Greatrex, Bell and others. Operators now felt that they could say that the limits of their social obligations had been defined and that they could comply with them even with aircraft and operations which had been designed and planned before that knowledge had been available. 58. Their problem was to comply with them in safety and with economy. He mentioned safety because the greatest reduction in noise in the neighbourhood of airports came from getting the aircraft as high as possible before passing over residential areas and then reducing engine power as much as possible while over them. That introduced new operational techniques which were neither operationally easy nor popular. 59. The cost of complying with their obligations arose directly from the need on some aircraft to carry the so-called exhaust sound suppressors and also occasionally to restrict aircraft weight by reduction of fuel or payload. They did not often reduce the payload; it was most uneconomic, because. the exchange rate between aircraft weight and height and, therefore, noise levels, was poor, so that the practice was employed only in exceptional operational circumstances. Cost considerations could also arise from curfew restrictions on departures and arrivals and from the noise abatement provisions for engine run-ups on maintenance. 60. They did not, of course, quibble about the cost of noise abatement, any more than they would question the cost of safety margins on aircraft structural strength and performance; it was all part of the total job. It was, however, worth noting that the performance and weight costs of noise suppressors on the Boeing 707 over the life of a fleet was probably equal to the price of one aircraft, and that sort of margin had to be reflected in direct costs and fares. 61. It might be that in embarking on the development of suppressors they had adopted an unnecessarily expensive approach, and perhaps the Author would comment on that? They worsened the takeoff and climb performance and they added to the weight of fuel and aircraft for a given payload or journey. The regulatory or safety requirements, however, necessita...
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