Wake Vortex Systems

Wake VortexWake vortices are a by-product of lift generated by aircraft. Turbulence associated with these wakes poses a potential hazard to other aircraft, especially lighter aircraft following at low altitude. This risk is mitigated by air traffic control standards that require increased aircraft separation when wake turbulence avoidance is a concern.

The FAA and NASA have embarked on a multiphased research and development program to develop and implement wake avoidance solutions that can safely reduce separation between aircraft and improve airport capacity within the National Airspace System.

Wake Vortex Research

The mid-term phase of the research focuses on the application of wind-dependent procedures for improved departure operations from Closely Spaced Parallel Runways (CSPRs). These procedures are referred to collectively as Wake Turbulence Mitigation for Departures (WTMD).  The enabler for WTMD is a Wind Forecast Algorithm (WFA) being developed by MIT Lincoln Laboratory, which predicts when the runway crosswind will be suitable to ensure that the wake from the downwind runway will not impact the upwind aircraft. Figure 1 shows an example of a WFA minimum crosswind prediction.

Wake Vortex from NASA Study This picture from a NASA study on wingtip vortices illustrates the structure of a wake vortex through visualization enabled by smoke entrainment.

Specifically, the WFA forecasts when the crosswinds along the departure airspace, from the surface to the height that aircraft achieve divergent flight paths, (nominally defined as an altitude of 1000 feet) will remain consistently strong enough to provide wake-independent operations on the upwind runway.  The WFA has two components: a surface crosswind prediction and a winds aloft prediction.  The surface prediction is derived from a statistical analysis of recent wind behavior (past 35 minutes), available from the airport’s Automated Surface Observing Station (ASOS) at 1-minute intervals. The wind prediction aloft is derived from the Rapid Update Cycle (RUC) numerical weather prediction run by the NOAA National Center for Environmental Prediction.

Demonstration Versions Deployed

Real time operational versions of the WTMD system were deployed at Lambert International Airport in St. Louis and Houston Intercontinental Airport.  An operational field demonstration is planned for Spring 2011.  In addition, an analogous system is being investigated for safely reducing the spacing of arrival aircraft.

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