noise abatement
Gentlemen, untill now this has primarily been a pilots discussion. However let me add a bit to this discussion from the experience of an "Dinosauer" that once has spent 8 frustrating year in what is called "Noise Abatement and Environmental Protection ".
Before I go to the approach or departure noise problems let me quote an important sentence from ICAO PANS OPS Doc 8168 - Vol I - Chap V - Noise Abatement Procedures:
Nothing in these procedures shall prevent the pilot-in-command from exercising his authority for the safe operation of his aeroplane.
That sentence in mind I can assure you that taking off in a reduced power procedure will make you the "darling" of the beancounters in your company because of reduced fuel burn and wear on the costly engines. Also youīll become the darling of the Rabbits on the airport because of 2 or 3 db less perceived noise, but thatīs it!!
All the good intentions are gone once you or you FMC or what so ever gadget used applies climb power beyond the airport fence. One should remember what once a Scientist said. Aircraft noise is also perceived via the eyes, means the noise source you see you will hear more intensive. Also as mentioned in this thread social structure of the airport neighbours plays a major role in the amount of noise protests!!
On top of this remark - noise distribution in free atmosphere is a somewhat strange thing to happen. If an ideal atmosphere would exist at the moment of take off, the distribution of noise underneath the flightpath of an aircraft follows an "Gaussian Bell Distribution". Unfortunately there is wind, sometimes cloud layers and / or temperature layers / inversions. The wind will drift the noise in worst case towards one side of the flightpath, the clouds or temperature layers work as a mirror.
I remember evaluations done in the early 80īs at FRA that showed some departures to be extremly noisy while flying excactly on centreline of a SID and passing through a noise monitoring gate - two Noise microphones right and left of the centre line.
This all together can have as a result, that though a pilot has done everything he can do to contribute to noise abatement, the perceived noise level at the airport neighbours house or property becomes uncomfortable, to say the least.
As for the noise generated on an approach, I remember a discussion I had in 1984 with some engineers at Boeing Everett plant. They claimed than already that approach noise will become primarily Aerodynamic Noise, not engine noise.
This said, this is the explanation why Continous Descend Approaches work very well in a distance to the airport fence, but will not have a similar influence on the noise levels on final with gear, flaps and slats extended.
So all you as a pilots involved can do is to follow the SOPīs and try your best. Donīt expect to receive a glorious appreciation fromthe airport neighbours!!
Jo
Last edited by Annex14; 9th Jul 2012 at 10:09.