challenges that feed into the way the system is funded. Other challenges are societal: airport expansion with its increases in noise and pollution, and the transportation infrastructure that allows people to get from their doorsteps to the airport. Finally, challenges in weather and wind conditions, including turbulence, gust, shear, and visibility, are physical in nature, and not the topic of this study. This report concerns just one of these many obstacles, a challenge that has both operational and physical aspects: wake turbulence.
All aircraft trail wake vortices as a consequence of lift developed in flight. The wake vortex can present a real danger to aircraft following each other, particularly when the leader is larger than the follower. When the Boeing 747 entered the airspace system in 1970, it was substantially bigger than existing commercial aircraft. As a result, wake vortex separation criteria were developed based on then-available technology. Though there have been a few revisions to the criteria over the intervening years, the state of the art has not provided a basis for substantial revisions. In many cases, these wake vortex separation requirements (discussed in the next section) prevent the use of reduced separation standards enabled by satellite and other technologies. This report reviews the nation’s wake turbulence research and development program and assesses its ability to provide wake vortex avoidance and/or mitigation technologies that will permit achievement of the NextGen goals.
There are no Federal Aviation Regulations specific to wake vortex hazards, either for certification or operations. Current aircraft separation standards related to wake vortex hazards have evolved over the past 40 years. Guidance material for pilots is contained in FAA Advisory Circular 90-23F: Aircraft Wake Turbulence (FAA, 2002), and in the FAA Aeronautical Information Manual (FAA, 2006a), updated semiannually. These publications contain educational and operational advisory information pertaining to aircraft operations in potential wake vortex situations, including pilot responsibilities. Pilot groups and industry associations have also issued advisory material to their constituents to raise awareness and provide guidance for avoiding and dealing with potential encounters. Pilots are generally well aware of this information and adhere to the recommended operating procedures for wake vortex avoidance. However, these procedures generally require pilots to observe the flight path of the wake-generating aircraft; therefore they are currently effective only in visual meteorological conditions (VMC), i.e., clear weather.
ATC aircraft separation standards and procedures for their use are contained in FAA Order 7110.65R: Air Traffic Control (FAA, 2006b). As