Automatic Dependent Surveillance–Broadcast  (ADS-B)  Wake Turbulence  Radar Traffic Advisories  Vortex Generation  Automatic DGLYPH<df00>pGLYPH<df00>ndGLYPH<df00>nt SurvGLYPH<df00>illancGLYPH<df00>−Broadcast (ADS−B) is a surveillance technology being deployed throughout the NAS  to facilitate improvements needed to increase the capacity  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  ground system also provides Traffic Information Services- Broadcast (TIS-B) and Flight Information Services-Broadcast  (FIS-B) for use on appropriately equipped aircraft, enhancing  the user’s situational awareness (SA) and improving the  overall safety of the NAS.  ThGLYPH<df00> ADS−B systGLYPH<df00>m is composGLYPH<df00>d of aircraft avionics and a ground infrastructure. Onboard avionics determine the position  of the aircraft by using the GPS and transmit its position,  along with additional information about the aircraft, to ground  stations for use by ATC and nearby ADS-B equipped aircraft.  In thGLYPH<df00> UnitGLYPH<df00>d StatGLYPH<df00>s, ADS−B GLYPH<df00>quippGLYPH<df00>d aircraft GLYPH<df00>xchangGLYPH<df00> information on one of two frequencies: 978 or 1090 MHz.  The 1090 MHz frequency is associated with Mode A, C, and S  transponder operations. 1090 MHz transponders with integrated  ADS−B functionality GLYPH<df00>xtGLYPH<df00>nd thGLYPH<df00> transpondGLYPH<df00>r mGLYPH<df00>ssagGLYPH<df00> sGLYPH<df00>ts with additional ADS−B information. This additional information is known as an “extended squitter” message and referred to as  1090ES. ADS−B GLYPH<df00>quipmGLYPH<df00>nt opGLYPH<df00>rating on 978 MHz is known as the Universal Access Transceiver (UAT).  Radar equipped ATC facilities provide radar assistance  to aircraft on instrument flight plans and VFR aircraft  provided the aircraft can communicate with the facility and  are within radar coverage. This basic service includes safety  alerts, traffic advisories, limited vectoring when requested,  and sequencing at locations where this procedure has been  established. ATC issues traffic advisories based on observed  radar targets. The traffic is referenced by azimuth from the  aircraft in terms of the 12-hour clock. Also, distance in  nautical miles, direction in which the target is moving, and  type and altitude of the aircraft, if known, are given.  An example would be: “Traffic 10 o’clock 5 miles east  bound, Cessna 152, 3,000 feet.” The pilot should note that  traffic position is based on the aircraft track and that wind  correction can affect the clock position at which a pilot locates  traffic. This service is not intended to relieve the pilot of the  responsibility to see and avoid other aircraft.  [Figure 14-44]  In addition to basic radar service, terminal radar service  area (TRSA) has been implemented at certain terminal  locations. TRSAs are depicted on sectional aeronautical  charts and listed in the Chart Supplement U.S. (formerly  Airport/Facility Directory). The purpose of this service is to  provide separation between all participating VFR aircraft and  all IFR aircraft operating within the TRSA. Class C service  provides approved separation between IFR and VFR aircraft  and sequencing of VFR aircraft to the primary airport. Class  B service provides approved separation of aircraft based on  IFR, VFR, and/or weight and sequencing of VFR arrivals to  the primary airport(s).  All aircraft generate wake turbulence during flight. This  disturbance is caused by a pair of counter-rotating vortices  trailing from the wingtips. The vortices from larger aircraft  pose problems to encountering aircraft. The wake of these  aircraft can impose rolling moments exceeding the roll- control authority of the encountering aircraft. Also, the  turbulence generated within the vortices can damage aircraft  components and equipment if encountered at close range. For  this reason, a pilot must envision the location of the vortex  wake and adjust the flight path accordingly.  Lift is generated by the creation of a pressure differential over  the wing surface. The lowest pressure occurs over the upper  wing surface and the highest pressure under the wing. This  pressure differential triggers the rollup of the airflow aft of  the wing resulting in swirling air masses trailing downstream  of the wingtips. After the rollup is completed, the wake  consists of two counter rotating cylindrical vortices. Most of  the energy lies within a few feet of the center of each vortex.  [Figure 14-45]  Figure 14-44.  Traffic advisories.  TRACK  TRACK  Traffic information would bGLYPH<df00> issuGLYPH<df00>d to thGLYPH<df00> pilot of aircraft “A”  as 12 o’clock. ThGLYPH<df00> actual position of thGLYPH<df00> traffic as sGLYPH<df00>GLYPH<df00>n by  thGLYPH<df00> pilot of aircraft “A” would bGLYPH<df00> 1 o’clock. Traffic information  issuGLYPH<df00>d to aircraft “B” would also bGLYPH<df00> givGLYPH<df00>n as 12 o’clock, but  in this casGLYPH<df00>, thGLYPH<df00> pilot of “B” would sGLYPH<df00>GLYPH<df00> traffic at 10 o’clock.  Wind  A  B  14-26 