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DESCENT AND APPROACH

As discussed earlier, center-controlled airspace is divided into smaller pieces of airspace called sectors. Each sector is further divided into high altitude or low altitude portions of sectors. High altitude sectors are aircraft that are above 24,000 feet, and low altitude sectors are below 24,000 feet.  For example, the Macey Womac Arrival that we monitor here on atcmonitor.com is the low altitude en route northeast Atlanta sector.  Controllers who work that sector have named it "Logen" for the last intersection name included on the arrival chart.  

Once your aircraft has descended below 24,000 feet, it is considered to be in the descent phase of flight.  Your pilot will contact the center controller with his or her arrival intentions.  For example, the pilot might say "LAX Center, Delta 542 is inbound via Paradise Four".  Paradise Four simply refers to the pre-defined arrival route into the LAX airspace that has been filed by the pilot's dispatcher. That route is called "Paradise Four" arrival. 

Don't confuse a STAR with STARS! STAR is the FAA's legacy acronym for Standard Terminal Arrival Route.  STARS is the newer acronym for Standard Terminal Replacement System.   Many high traffic airports have dedicated Standard Terminal Arrival Routes (STAR) which are code named and published to keep from having to repeat this information often. For example, Los Angeles has the "Paradise Four" arrival which has a standard set of instructions for aircraft entering the LAX airspace from the East sector. Pilots can contact ATC and alert them that they are approaching via the "Paradise Four" arrival. In Atlanta, you may be familiar with the Macey Arrival STAR which feeds the Atlanta TRACON from the northeast.

With arrivals coming from several directions, the center controller of each sector must route several aircraft entering the center airspace, to begin merging towards one path towards the airport. The center controller makes every effort to have all entering aircraft in such a position that each aircraft will fall one behind the other and follow this path towards the landing runway. Once all of the aircraft are being established in the follow-the-leader process, they are then handed off to the approach controller working in the TRACON.  

At this point, the approach controller's job is to adjust the flight path of each incoming aircraft, by slightly adjusting its heading, altitude and speed in order to further merge this traffic into one single file line towards the active runway which establishes the aircraft's final approach course. Upon initial contact with approach, the pilots advise the controller that they have the current Airport Terminal Information Service (ATIS) information, which includes the current weather, wind speed and active runway information. This information is usually coded with one of the 26 phonetic alphabet codes, such as Alpha, Bravo, Charlie, etc. So your pilot may contact LAX approach and say "LAX approach, Delta 542, with information Bravo", assuming that's the coded indicator for that particular day.

As the aircraft are continuing to approach the airport, the pilots onboard are checking in with approach control to find out several things about their destination. For example, if it's a busy day at LAX, the controller may have to position aircraft side by side during the final approach phase of flight. While doing this, the aircraft that is already aligned with the runway may have to speed up, while the ones alongside them slow down, and side step in behind the landing aircraft. This is the type of information that pilots are listening for while they continue their approach for landing. 
Once the final approach course is established, the pilots of Delta flight 542 will line up the aircraft with the runway centerline to prepare for landing. When the aircraft has lined up with the runway for landing (which is usually 10 miles from the airport), the TRACON controller will hand off the aircraft to the airport's tower controller.


TOUCHDOWN FOR LANDING 

Unlike the controllers working in the TRACON, the tower controllers have the best view of the airport. They give Delta 542 a landing clearance, which might sound like "Delta 542, runway 25 Right (25R), winds are out of the Northeast at 15 knots; you are cleared to land". Once the aircraft touches down on the runway and air brakes slow the aircraft down, it turns off the runway onto one of the taxiways. Once the aircraft is clear of the active runway, the tower hands off Delta 542 to the ground controller, who advises your aircraft how and where to taxi to get to your arrival gate at LAX. The ground controller usually sits in the control tower, so he or she can see, and at larger airports uses ground radar to track the movements of your aircraft while it taxis to the arrival gate. The ground radar is usually located on top of the control tower in the shape of a white dome. Look for it the next time you fly. Once the aircraft is parked at the gate, you have reached your destination and the job of the air traffic controllers working that flight is finished.



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