The skies over New York City's John F. Kennedy International Airport were clear and relatively calm when American Airlines Flight 587 took off on November 12, 2001. Minutes later the Airbus A300-600 airliner broke up in midflight and dove into the ground--felled perhaps in part by turbulent vortices of air produced by the wings of a Japan Airlines jumbo jet that had just preceded it down the runway.

Engineers are working on ways to detect hazardous wake vortices so pilots can avoid them or to design aircraft that leave safer skies behind them. If implemented, these new technologies could boost the number of planes that airports could handle, thus cutting delays and enabling increased commercial air traffic in coming years.

This article was originally published with the title Quieting Killer Wakes.

1 Comments

1. 1. scots engineer 08:48 AM 7/11/10

   Despite the orthodox explanation of flight being down to the difference in pressure between the top and bottom surface of the wings, a more scientifically consistent theory invokes the law of conservation of momentum and means that in totality the forces resisting gravity come from accelerating masses of air in a downward direction. Thus any flying aircraft creates a flow of moving air which will take time and space to to disperse both it's momentum and energy through friction with the nearby air mass and surface features. The architecture that these flows assume have to obey both the laws of conservation of momentum and energy and become continuous vortices leading back from the wing tips and tailplanes, or in the case of birds where the flapping action sheds these vortices to leave a trail of internally rotating torii ( like a smoke ring without the smoke ). Since momentum increases linearly but kinetic energy increases exponentially with velocity, efficiency comes from keeping air velocity as low as possible -which means a greater air mass moving slower to provide the same lift forces. By the simple geometry of surface to volume ratio and the fact that the viscosity friction only acts at the surface of the bubble, or vortex, a large slow vortex takes longer to slow down and disperse. One thing that is in their favour is that the wing tip vortices rotate in opposite directions and will eventually cancel each others angular momentum when they meet. It may well be that measures to increase the angular momentum of these vortices at the expense of the linear momentum may lead to a more rapid dispersal. It remains true that there will be turbulence behind any large aircraft with a scale and duration linked to the mass and speed of that aircraft, and there is no getting round that.

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