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Old 21st Feb 2001, 15:02
  #4 (permalink)  
Elevation
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The winglet's main purpose is to minimise the "spillover" of air from underneth the wing (higher pressure) to the topside (lower pressure), it also reduces wingtip vortices this way.
When an airplane takesoff, wingtip vortices is not significant (ground effect) and the spillover is also not a major factor.
So imho, the winglets have negligible effect on the airplane's acceleration.

From a pax's point of view, a twin will sound louder than a 4-engine, simple logic, for a twin, all the noise of the engines are right next to the fuselage. As for the 4-engine, the noise from the engines is lower because the noise produced is split between the outboard engine (which is further from the fuselage) and the inboard engine !

Cheers.