The ICAO has imposed Noise Abatement Departure Procedures (NADP1 and NADP2) in order to limit the noise impact of departing aircraft on communities living nearby airports. Could noise reduction lead to an increase in NOx/CO2 emissions (an aircraft needs more power to achieve faster climbing rates)? If so, why don't the ICAO (or local authorities) impose "Emission Reduction Procedures"?

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    $\begingroup$ Because, if your theory is correct (and I don't know the answer to that part), people really care far less about emissions than they care about being kept up all night by aircraft taking off from the local airport. $\endgroup$
    – FreeMan
    Dec 20 '17 at 21:01
  • $\begingroup$ This document (Appendix B) points out "significant tradeoff issues [...] between noise, NOX and CO2, primarily related to the thrust-settings". It looks more complex than I thought (sustainableaviation.co.uk/wp-content/uploads/2017/03/…) $\endgroup$
    – harveyAJ
    Dec 22 '17 at 16:20

Generally, it is most fuel efficient - when considering fuel for the whole flight as opposed to individual flight phases - to climb to cruise altitude as quickly as possible (i.e. using maximum thrust), since the aircraft flies much more efficiently at cruise altitude than at lower levels. This is in direct contradiction to anything to do with close-in noise reduction (i.e. around the airport), but it would reduce total flight emissions (other than noise).

For noise further away from the airport, climbing with maximum thrust may actually be more beneficial, as there is another tradeoff between noise emitted at the aircraft and the altitude achieved at the noise sensitive area (quiet can mean passing with low thrust or at high altitude).

So, yes, by altering the climb profile, the emission profile for the flight is altered. The noise abatement procedures will often lead to higher emissions than could be achieved theoretically (not necessarily practically though).


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