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Aviation History
1960
1960 - 1459.PDF
FLIGHT, 26 August 1960 *^^r**^m 299 JET NOISE and Society A CASE FOR FULLER INFORMATION? by J. M. Ramsden THIS is the time of the year when movements at LondonAirport are at their peak, and when the consequent dis-ruption of family life, business, schooling and so on is at its least tolerable. A contributor to the New Statesman for August 6wrote: "Having now listened (in a Harlington back garden) to the noise they leave behind them I think these jets produce the mostterrible noise yet invented by man." Again, in a joint letter to The Times on August 10, repre-sentatives of six London Airport residents' associations took sharp Jet noise curves based on Bolt Beranek and Newman data. Key: (1) Comet 4 landing; (2) Boeing 707-120 landing; (3) DC-8 landing; (4) Boeing 707-120 take-off, reduced thrust (8,000lb); (5) Comet 4 take-off with reduced thrust (5,600-6,000lb); (6) Comet 4 take-off, full thrust (10,5001b); (7) Boeing 707-420 take-off 15,0201b thrust; (8) average piston-engined aircraft landing (DC-7, DC-7B, DC-7C, DC-6B, Super Constellations 1049 and 1649); (9) DC-8 take-off 13,0001b thrust; (10) Boeing 707- 320 take-off 13,5001b thrust; (11) average piston-engined aircraft (types as above) take-off 6OO 94 98 1O2 1O6 110 114 118 OVERALL SOUND - PRESSURE LEVEL (db) issue with an article in that newspaper which, in essence, hadsuggested that the noise problem was being exaggerated. The residents are waging their battle—as their letter to The Timesshows—with well informed arguments; the only emotional content of this particular quietly reasoned rebuttal was: "Wethink the limit of the tolerable has been passed when a child wokenin the night by a jet cries out—'No more noise! No morenoise!' " These public protests will continue, and they are likely to become more, rather than less, bitter as jet traffic increases. What does it cost a jet operator to reduce noise? The answer tothis question, wherein lies the essence of the jet noise problem, can be determined in general terms. The price to a Boeing 707-320can be as high as 10,0001b of fuel or pay load per decibel, and to a DC-8 (JT4A-9) it is of the same order. Roughly speaking, thedb is here interchangeable with the PNdb—the "perceived noise" decibel that is now the standard measure of jet noise at Londonand New York. These rough estimates assume the aircraft con- cerned to be at full power about three miles from the start oftake-off roll. In practice at London, everything depends on the noise limitation (llOPNdb by day) set by the Ministry of Aviation;the position of the Ministry's noise control monitoring points and the length of the runways concerned; the power-cutback tech-niques evolved by the operators; and other factors. It is therefore not easy to arrive at an estimate of the economic penalties incurredin practice. So far they have probably not been severe: certainly there have been no public protestations from the airlines, the greatmajority of whose crews have complied with the letter and the spirit of the Ministry's rules. The economic penalty of noisesuppressors, however, can be measured with a fair degree of realism: the airlines seem generally agreed that these devicesreduce thrust, increase fuel consumption and decrease payload by amounts ranging between one and two per cent in each case. Although the Ministry's noise rules do not have the force of lawbehind them, as do those of the US Federal Aviation Agency, something like 85-90 per cent of all jet take-offs are monitored bythe Ministry of Aviation at the control points indicated on the map overleaf, and the Ministry does not hesitate to reprimand
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