THEwake vortices generated by aircraft [1–3] are a severe hazardnto other aircraft following behind. Because of mutual inter-naction, the trailing vortex pair descends at a rate of roughly 1.3 ton2:0m=s for all but extremely light aircraft. Therefore, if the trailingnaircraft stays well above the level of the leading aircraft, the chancesnofwake vortex encounter are small.Nevertheless, the rate of decay ofnthese vortices is important to determining the allowable separationntimes and, hence, distances between aircraft during the landingnapproach; therefore, it is the principal factor in capacity limitation atnbusy airports. The International Civil Aviation Organization (ICAO)ndefines minimum separation distances, which have been rather con-nservative because of the paramount need for safety. Even a moderateneasing of the separation standardswould lead to a significant increasenin airport capacities around the world. Given the fact that air travel isnexpected to double or even triple by 2025, and very few airports arenbeing built at major metropolitan centers, increasing the throughputnis perhaps the only solution to the projected increase in air trafficnwithout causing undue inconvenience to the traveling public and undesirable environmental impact due to inevitable delays andnairport congestion. Gerz et al. [4] presented current knowledge onntransport and decay of wake vortices in the atmosphere and outlinednconcepts and designs of wake vortex advisory systems in Europe andnthe United States.
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