Boss Raptor,
I stand corrected on the 707 Hushkit.
But, I'm gonna get you on the
"Whether or not a S3 hushkit makes any difference to joe public is not the issue - what is from an operators/manufacturers point of view is that legally the noise footprint is within the S3 limits for compliance"
Noise certification has nothing to do with the footprint, though I suppose one could assume they get smaller as the maximum noise levels based on weight and number of engines comes down. Noise certification is based on measured levels at 3 points. Takeoff, lateral(sideline), and approach.
And to say hushkits making any difference to joe public is not the issue, than why does noise certification exist? So that joe public can look forward to a future with less aircraft noise........
Makes no difference if you lower levels 10 dB cum like Chapter 4 did when every aircraft built today meets that criteria. With the increase in movements that will happen over the next 10 years and no Chapter 3 phaseout, joe public will think Chapter 4 allowed for more noise.
I knew the Jet Engineering kit was a Chapter 4/Stage 3 (Stage 4 is not available for application in the USA until 2006) kit. I just wanted to point out that it really will make no difference to humans or the monitors.
Noise footprints generated by the manufacturers or the hushkitters is based on max rated takeoff power. Well, we all know every operator out there will derate to the maximum allowable unless forced to do otherwise to save on engine maintenance. When operating derated the noise footprint increases dramatically. Also on approach they use stable thrust to generate the noise footprint when most airplanes are on auto throttle. This too increased the noise footprint of any aircraft dramatically.
Operational aircraft tend to be a lot lighter when they are landing than what they were noise certified to. This sometimes can drop the thrust required into the bleed schedule (Rolls and Pratt). When a bleed opens you can double the EPNL of an engine.
Am I boring you yet?
When you look at it, the current noise certification requirements by the FAA and ICAO are bogus on a realistic operational standpoint. The noise certification requirements are based on a single event, when the person experiencing the noise is facing multiple events. They are not indicative of how the airplanes are flown on a day to day basis.
Peace out Boss.........
