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


(1) Subject to the provisions of paragraph 4 of this Part of this Schedule an aeroplane having the maximum total weight authorised specified in the 1st column of the following Table shall not, at the points referred to at (a), (b) and (c) of paragraph 2 of this Part of this Schedule, exceed in the noise certification reference conditions the noise levels in relation to those points in the 2nd column, the 3rd, 4th and 5th columns (whichever is applicable having regard to the number of engines installed in the aeroplane) and in the 6th column of that Table, as shown by flying trials.
TABLE
Noise level in EPNdB
Maximum total weight authorised of aeroplane
At point (a)
At point (b)
At point (c)
2 engines
3 engines
4 engines
400,000 kg or more
103
385,000 kg or more
101
104
106
280,000 kg or more
105
48,125 kg or less
89
35,000 kg or less
94
98
28,615 kg or less
89
20,234 kg or less
89
(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/II/paragraph/3 (the official version)
Page: https://openlegislation.uk/air-navigation-noise-certification-order-1990/schedule-1/part-II/paragraph-3
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.