# The Air Navigation (Noise Certification) Order 1990, Paragraph 3


(1) An aeroplane having the maximum total weight authorised specified in the 1st column of the following Table shall not, at the point referred to in paragraph 2 of this Part of this Schedule, exceed in the noise certification reference conditions the noise level specified in the 2nd column of that Table, as shown by flying trials.
TABLE
Maximum total weight authorised of aeroplane
Peak noise level in dB(A) at measurement point
1400 kg or more
88
600 kg or less
76
(2) Where the maximum total weight authorised of the aeroplane is between the weights specified in the above Table, the noise levels which are not to be exceeded shall vary linearly according to the logarithm of the maximum total weight authorised of the aeroplane.
(3) The necessary corrections shall be made where flying trials are carried out in conditions other than the noise certification reference conditions.

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Source: https://www.legislation.gov.uk/uksi/1990/1514/schedule/1/part/VI/paragraph/3 (the official version)
Page: https://openlegislation.uk/air-navigation-noise-certification-order-1990/schedule-1/part-VI/paragraph-3
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.