Noise abatement
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Are you sure? I believe that you are using LIDO
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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 you´ll become the darling of the Rabbits on the airport because of 2 or 3 db less perceived noise, but that´s 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 80´s 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 SOP´s and try your best. Don´t expect to receive a glorious appreciation fromthe airport neighbours!!
Jo
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 you´ll become the darling of the Rabbits on the airport because of 2 or 3 db less perceived noise, but that´s 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 80´s 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 SOP´s and try your best. Don´t expect to receive a glorious appreciation fromthe airport neighbours!!
Jo
Last edited by Annex14; 9th Jul 2012 at 10:09.
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Interesting that you should mention Germany too. The last time I looked in our Jeppessen rule book, in the ATC differences section it stated that NADP1 should be used for all german airports.
Thread Starter
Thanks for everyone's input including those via private mail. I am particularly interested how others determine takeoff N1 setting and V speeds and how climb gradients required by particular SIDs are taken account of. Ryanair apparently do not use improved climb. So it seems like they share Mutt's view.
I think it fair to say that this has been a bit of an eye opener. If I lived close to Schönefeld, which a lot of my colleagues do, I would be concerned that everything really is being done to minimize noise when it finally gets going.
I think it fair to say that this has been a bit of an eye opener. If I lived close to Schönefeld, which a lot of my colleagues do, I would be concerned that everything really is being done to minimize noise when it finally gets going.
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As far as I know, and our company policy, is that all German airports have the following noise abatement procedure:
T/o thrust V2 plus 10 min. Until 1500'agl
Then climb thrust and accelerate to flap up speed on schedule.
I am now confused as some German airlines don't seem to comply with this rule themselves? is our company wrong and our info incorrect?
T/o thrust V2 plus 10 min. Until 1500'agl
Then climb thrust and accelerate to flap up speed on schedule.
I am now confused as some German airlines don't seem to comply with this rule themselves? is our company wrong and our info incorrect?
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despegue
Nothing to worry about or to be confused. Your company simply flys according
ICAO PANS OPS Doc 8168 Vol I - Part V - Chap. 3.1.2.1 - Procedure A.
That was tested repeatedly on different airports in Germany back in the 80´s, also the Procedure B was checked. However the differences - max 1 - 3 db perceived noise level - are not considered to be significant enough to recommend only one of the two ICAO procedures, or probably any specific type or company related procedure.
As mutt pointed out earlier very correct, the best method of noise abatement is to get as much distance possible between your aircraft and the recepient on the ground.
Jo
ICAO PANS OPS Doc 8168 Vol I - Part V - Chap. 3.1.2.1 - Procedure A.
That was tested repeatedly on different airports in Germany back in the 80´s, also the Procedure B was checked. However the differences - max 1 - 3 db perceived noise level - are not considered to be significant enough to recommend only one of the two ICAO procedures, or probably any specific type or company related procedure.
As mutt pointed out earlier very correct, the best method of noise abatement is to get as much distance possible between your aircraft and the recepient on the ground.
Jo
Last edited by Annex14; 10th Jul 2012 at 08:32.
Thread Starter
Things have changed a bit over the last 20 years. The vast majority of takeoffs are now twin jets, which as has been pointed out are most often limited by the 2.4% climb gradient engine out scenario in the second segment. But in almost all cases we have such a surplus of thrust that we see pretty healthy initial climb rates once we finally get airborne.
The noise per aircraft has obviously reduced over time. But overall number of takeoffs has also increased dramatically. The question is could we do better? Ironically I can find no evidence that reduced thrust takeoffs save fuel, nor can I find any conclusive proof that they are noise optimized at least at low weights with low acceleration heights. What they definitely do is make engines last longer as the recent post about the TUI 737 engine record shows. It depends who the engine belongs to as to who benefits from that long term.
The noise per aircraft has obviously reduced over time. But overall number of takeoffs has also increased dramatically. The question is could we do better? Ironically I can find no evidence that reduced thrust takeoffs save fuel, nor can I find any conclusive proof that they are noise optimized at least at low weights with low acceleration heights. What they definitely do is make engines last longer as the recent post about the TUI 737 engine record shows. It depends who the engine belongs to as to who benefits from that long term.
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Annex14, ref your post #22, as you stated, on approach aerodynamic noise is the killer.
I used to fly for a company that had a limit for geardown @ 3.5nm, sometimes a bit late to use as a target versus limit, and certainly only usable if one was applying the 500' VMC stable appr gate in preference to the 1000' IMC one.
It was always nice when flying a visual to try to leave the gear till that point & be spooling up @ 500 agl if possible just for self satisfaction (to the naysayers who say too late to stabilise I would say, well, a CFM56 is permanently spooled up anyhow, so response is pretty much instantaneous from the artificially high flt idle we have)
I had the good fortune to fly many visuals over the city I lived (no noise abatement/local regs to prohibit it, and I am sure the local tourist board liked it
) following an sms sent from 8000' ft or so to Mrs Playstation to look out.
I always asked afterwards, "was it loud" as we arched gracefully across the centre @ 1500' or so agl in a turn, apparently it wasn't, but on the days when I judged it less well & passed above 1500' but with the gear down it was, I am told, much noisier.
So (and good airmanship does sometimes dictate otherwise) the key to appr noise appears to be the latest practical selection of gear (following a well executed CDA ) On take off I am sure thrust reduction@ 1500 accelerate @ 3000 in reduced climb would be the best, but , the need to save fuel/engines has won the day here in most companies priorities, witness Ryanairs change from NADP1 to 2 as the default choice.
I used to fly for a company that had a limit for geardown @ 3.5nm, sometimes a bit late to use as a target versus limit, and certainly only usable if one was applying the 500' VMC stable appr gate in preference to the 1000' IMC one.
It was always nice when flying a visual to try to leave the gear till that point & be spooling up @ 500 agl if possible just for self satisfaction (to the naysayers who say too late to stabilise I would say, well, a CFM56 is permanently spooled up anyhow, so response is pretty much instantaneous from the artificially high flt idle we have)
I had the good fortune to fly many visuals over the city I lived (no noise abatement/local regs to prohibit it, and I am sure the local tourist board liked it
) following an sms sent from 8000' ft or so to Mrs Playstation to look out.I always asked afterwards, "was it loud" as we arched gracefully across the centre @ 1500' or so agl in a turn, apparently it wasn't, but on the days when I judged it less well & passed above 1500' but with the gear down it was, I am told, much noisier.
So (and good airmanship does sometimes dictate otherwise) the key to appr noise appears to be the latest practical selection of gear (following a well executed CDA ) On take off I am sure thrust reduction@ 1500 accelerate @ 3000 in reduced climb would be the best, but , the need to save fuel/engines has won the day here in most companies priorities, witness Ryanairs change from NADP1 to 2 as the default choice.
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The A300-600 was the first aircraft where we encountered increasing thrust at acceleration height, Airbus solved this by limiting the thrust reduction to 25% OR CLIMB THRUST, I'm pretty sure that Embraer does the same thing.
As a sideline anecdote .. nothing new here.
Wal Stack (the QF ops eng boss back in REALLY olden times) related a tale concerning the very earliest days of reduced thrust takeoffs (QF was one of the initial leading lights).
Appears one of his 707s launched to wherever ... crew came back and raised the point that, at thrust reduction to climb power, the FE had pushed up the throttles .. and the Commander thought that a tad strange.
Whereupon Wal had a direction issued to limit takeoff thrust reduction to the intended climb thrust setting .. which made the spectre go away and kept his operating crews happy and contented.
One of the advantages of having an (ex) operator running the ops eng show.
As a sideline anecdote .. nothing new here.
Wal Stack (the QF ops eng boss back in REALLY olden times) related a tale concerning the very earliest days of reduced thrust takeoffs (QF was one of the initial leading lights).
Appears one of his 707s launched to wherever ... crew came back and raised the point that, at thrust reduction to climb power, the FE had pushed up the throttles .. and the Commander thought that a tad strange.
Whereupon Wal had a direction issued to limit takeoff thrust reduction to the intended climb thrust setting .. which made the spectre go away and kept his operating crews happy and contented.
One of the advantages of having an (ex) operator running the ops eng show.
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crew came back and raised the point that, at thrust reduction to climb power, the FE had pushed up the throttles
Haven't seen the FAFC "unlock" shuffle for a while though.........
