I guess that was also a bit crass. I just have put some real time into long technical discussions on here and then get flamed for it.
All airlines have to be noise conscious these days. Problem is, most really want to lower their levels, but few understand how to operationally do it. I won't preach to the choir and explain all the many things that can and do affect the perceived noise of large aircraft. Things are tightening up, everyday there are more politicians screaming about airport noise.
We have made great leaps in reduction since the 70s, but the reductions are getting smaller and smaller. The airports have to be able to show regular reductions in the amount of noise leveled on any one area to at least appear they are doing something.
The old days of save your tires and brakes by landing at lower speeds at max flap are soon going to be failing the cost equation. Airports will have to pass on the cost of a wider area of noise suppression installations in homes to the airlines if they start losing court battles. All those 747s landing at LHR makes that place especially targeted.
Without looking I am not sure how many operations into LHR happen a day for 747s. I do know there is approximately a 2 dB difference in EPNL levels flaps 25 vs 30 on a 747. On the older ones it can be as much as 3 dB.
Using 2 dB, a crude calculation of an airline choosing to operate at Flaps 25 vs 30 would reduce it's operational noise dump by 2%. Doesn't sound like much, but it will add up fast as more and more operators follow suit, if they do. Hence the glass takes longer to fill.
The flaps 25 for 747s is just one small step. There is much more they could do that is not suggested by the manufacturer and should be mandated by the FAR/JAR regulations.
If airlines had to regularly qualify the acoustic configuration or condition of their airplanes they would become more conscious of the vast number of things that can reduce operational noise levels. Things they are already doing on a day to day basis. They just need to be shown how doing maintenance one way vs another can help or hurt the acoustic configuration of their aircraft. Even if it wasn’t forced I think they would be doing some of these things anyway. They just need to be taught how to look at how they acoustically maintain their aircraft. I know that an aircraft in poor acoustic shape can lose as much as 40% of it’s delivered ability to meet the FAR 36 Certified noise levels.
I can walk around an airplane and tell by looking if the plane has any chance of passing a test to see if it still meets what it was certified to noisewise. Let me look at the maintenance records and I can tell a lot more.
Aircraft are noise certified at constant thrust. The majority of aircraft today are landing with auto throttles on and is one reason why monitors show higher noise levels than cert. How conscious a pilot is to how he flies the airplane and how it affects monitored noise levels is another. Pilot input to controls and aircraft maintenance affects how much the auto throttle has to work(move around). If it is constantly jumping around chances are it is bumping the engines to maintain speed. The more it bumps the more noise the engine dumps. This can be helped.
I kinda rambled on past the intent of what I wanted here. Sorry if it was too boring.
Time for bed.