I.R.PIRATE sez: "Why not climb at V2?"
Cannot. For
certification, both ICAO and FAA noise regs call for (applicant's choice) between V2+10 to V2+20.
FrankR sez: "Why not follow the procedure as it is written?"
I should have been more clear. Sorry. This is NOT a noise abatement procedure at all. It is a standardized
certification procedure, not at all the best way to fly neighborly.
Green Cactus sez: "If you fly the procedure as instructed (V2+10), you are not going to spent more time flying that speed when you reduce the takeoff weight. You will be climbing at a lower speed but steeper, you will reach your desired altitude in less time. And that equals less noise on the ground...."
Yes, this is true for the takeoff or flyover measurement, since most of the noise reduction on the ground is due to a longer distance now away from the microphone. However, it is
not true for the
sideline measurement which must be made at the noisiest point perpendicular to the takeoff path 450 meters away. How come? It's because the noise measurements are in
effective perceived noise level units which take into account the time of exposure to the noise. Slower TAS, higher noise.
Summing all this techno trash up, high gross weight = higher takeoff and approach noise, but lower sideline noise. Low gross weight = lower takeoff and approach noise, but higher sideline noise
given a lower climb TAS.
My goal is to
not increase sideline noise at lower weights, hence I must climb at
more than the newly calculated V2+10. And that's the question. All mumbo jumbo aside, from an
operational standpoint, do you feel that a climb airspeed restriction (at lower weight) of say, V2+18 has advantages/disadvantages over V2+10? When considering the question, remember that V2+10 at gross weight is equal to V2+18 at the lower weight.
(And for the purists out there, yes I know "mass" is more correct, but let's just all agree we're in an American assumed 1G environment, OK?
)
Tom