Airport Operations

Automatic Dependent Surveillance–Broadcast (ADS-B) A B Automatic Dependent Surveillance−Broadcast (ADS−B) is a Wind surveillance technology being deployed throughout the NAS to facilitate improvements needed to increase the capacity TRACK TRACK and efficiency of the NAS, while maintaining safety. ADS-B supports these improvements by providing a higher update rate and enhanced accuracy of surveillance information over the current radar-based surveillance system. In addition, ADS-B enables the expansion of air traffic control (ATC) surveillance services into areas where none existed previously. The ADS-B Traffic information would be issued to the pilot of aircraft “A” ground system also provides Traffic Information Services- as 12 o’clock. The actual position of the traffic as seen by the pilot of aircraft “A” would be 1 o’clock. Traffic information Broadcast (TIS-B) and Flight Information Services-Broadcast issued to aircraft “B” would also be given as 12 o’clock, but (FIS-B) for use on appropriately equipped aircraft, enhancing in this case, the pilot of “B” would see traffic at 10 o’clock. the user’s situational awareness (SA) and improving the overall safety of the NAS. Figure 14-44. Traffic advisories. The ADS−B system is composed of aircraft avionics and a area (TRSA) has been implemented at certain terminal ground infrastructure. Onboard avionics determine the position locations. TRSAs are depicted on sectional aeronautical of the aircraft by using the GPS and transmit its position, charts and listed in the Chart Supplement U.S. (formerly along with additional information about the aircraft, to ground Airport/Facility Directory). The purpose of this service is to stations for use by ATC and nearby ADS-B equipped aircraft. provide separation between all participating VFR aircraft and all IFR aircraft operating within the TRSA. Class C service In the United States, ADS−B equipped aircraft exchange provides approved separation between IFR and VFR aircraft information on one of two frequencies: 978 or 1090 MHz. and sequencing of VFR aircraft to the primary airport. Class The 1090 MHz frequency is associated with Mode A, C, and S B service provides approved separation of aircraft based on transponder operations. 1090 MHz transponders with integrated IFR, VFR, and/or weight and sequencing of VFR arrivals to ADS−B functionality extend the transponder message sets with the primary airport(s). additional ADS−B information. This additional information is known as an “extended squitter” message and referred to as Wake Turbulence 1090ES. ADS−B equipment operating on 978 MHz is known All aircraft generate wake turbulence during flight. This as the Universal Access Transceiver (UAT). disturbance is caused by a pair of counter-rotating vortices trailing from the wingtips. The vortices from larger aircraft Radar Traffic Advisories pose problems to encountering aircraft. The wake of these Radar equipped ATC facilities provide radar assistance aircraft can impose rolling moments exceeding the roll- to aircraft on instrument flight plans and VFR aircraft control authority of the encountering aircraft. Also, the provided the aircraft can communicate with the facility and turbulence generated within the vortices can damage aircraft are within radar coverage. This basic service includes safety components and equipment if encountered at close range. For alerts, traffic advisories, limited vectoring when requested, this reason, a pilot must envision the location of the vortex and sequencing at locations where this procedure has been wake and adjust the flight path accordingly. established. ATC issues traffic advisories based on observed radar targets. The traffic is referenced by azimuth from the Vortex Generation aircraft in terms of the 12-hour clock. Also, distance in Lift is generated by the creation of a pressure differential over nautical miles, direction in which the target is moving, and the wing surface. The lowest pressure occurs over the upper type and altitude of the aircraft, if known, are given. wing surface and the highest pressure under the wing. This pressure differential triggers the rollup of the airflow aft of An example would be: “Traffic 10 o’clock 5 miles east the wing resulting in swirling air masses trailing downstream bound, Cessna 152, 3,000 feet.” The pilot should note that of the wingtips. After the rollup is completed, the wake traffic position is based on the aircraft track and that wind consists of two counter rotating cylindrical vortices. Most of correction can affect the clock position at which a pilot locates the energy lies within a few feet of the center of each vortex. traffic. This service is not intended to relieve the pilot of the [Figure 14-45] responsibility to see and avoid other aircraft. [Figure 14-44] In addition to basic radar service, terminal radar service 14-26