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


(1) Subject to the provisions of paragraph 4 of this Part of this Schedule a helicopter 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 specified in relation to those points in the 2nd, 3rd and 4th columns of that Table, as shown by flying trials.
TABLE
Maximum total weight authorised of helicopter
Noise level in EPNdB
At point (a)
At point (b)
At point (c)
80,000 kg or more
109
108
110
788 kg or less
89
88
90
(2) Where the maximum total weight authorised of the helicopter 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 helicopter.
(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/IX/paragraph/3 (the official version)
Page: https://openlegislation.uk/air-navigation-noise-certification-order-1990/schedule-1/part-IX/paragraph-3
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.