For noise ccnification of an aircraft (with a specified engine type), the aircraft has to fly precisely defined procedures to enable quantified noise measurements During those procedures, specific flight path propcnics arc prescribed (which often arc difficult to meet due to meteorological disturbances; this may require many test repetitions until the flight path requirements arc met). Pilot actions arc limited and must not include throttle or flap changes. Therefore, operational aircraft frequently are less noisy than certification flights.
In the future, standard procedures for flap and throttle scheduling may be accepted by the authorities for noise certification flights if those procedures arc always performed automatically by the flight management system not requiring any pilot action.
Presently, no noise rules exist for new SCTs. which means, that without a change or extension of existing noise rules, new SCTs cannot be certified. It is expected, that future SCTs must comply with the rules system FAR 36. stage 3 (perhaps modified) or even a future stage 4.
Certification of airports usually includes noise exposure levels (noise pressure, weighed by a human sensitivity filler including a weight for time of day. integrated over the noise exposure lime and the area) for the surroundings of the airports.
If the SCT will generate too much noise (e g. in climb phases not certification-related ). perhaps some airports will not accept SCTs although they can he certified according to the rules This may happen because the airport can loose its certification, if noise exposure levels nse too much, due to too much or too noisy traffic. Possibly the airports have to select the less noisy traffic to maintain their concession.
But airpon noise is not only related to aircraft (noise) performance, but also strongly to АТС (Air Traffic Control) procedures in the terminal area which often keep the aircraft for a longer time at low and noisy levels.