From The FAA: NextGen

Part 1: What it is and how it will impact maintenance

Did you know that when night flying for the Post Office was inaugurated between New York and Chicago in 1925, some system upgrades had to be made to assure safe flight? These improvements included: 289 flashing gas beacons, 17 planes with luminous instruments and parachute flares, five lighted terminal fields for primary and alternate landings, and 34 emergency landing fields along the route; that was initially for just one flight per night. It was the Roaring Twenties version of NextGen.

NextGen upgrades will be implemented into the Air Traffic Control (ATC) systems by 2020. These changes remove the guesswork from air-to-ground communications and assure expedient routes between airports; they’ll improve in-flight weather problem analysis; and foresee air-to-air traffic snarls that’ll provide the aircraft with corrections to avoid collisions both in-air and on the ground. In short, NextGen will be the eyes, ears, and decision-maker for all aircraft movements.

Automatic dependent surveillance broadcast (ADS-B)

According to the FAA NextGen performance standard, “All aircraft must be equipped with ADS-B by 2020 to fly in controlled airspace.”

NextGen’s purpose: incorporate these advances to improve efficiency, safety, and increase tracking, while intensifying information sharing in the National Airspace System (NAS). ADS-B will facilitate the direct routing of aircraft, while optimizing countless departures and approaches. It assists in tracking aircraft more efficiently; this increases capacity, while saving time and fuel. NextGen is a proactive approach to increasing aviation safety.

ADS-B broken down means automatic, being that the message element repeatedly “squitters,” or broadcasts, once per second; the message element is the information being transmitted, e.g. position, altitude, aircraft dimensions, etc., that contains the information for ATC to provide services. It is dependent as it relies on GPS (presently) for position; the rule doesn’t dictate ‘GPS’, but the system must be accurate. Surveillance as it provides information to ATC to determine who you are. Finally, broadcast … well, that’s self-explanatory. Like all technologies, it’s intended to be a fluid technology, i.e. its implementation and use is dictated by any events that could affect global aviation.

The further an aircraft is from a radar antenna, the more the accuracy degrades. However distance from an ADS-B ground station has no effect on ADS-B accuracy because it uses satellite-based position data. ADS-B allows tracking of aircraft, both fixed wing and rotorcraft, in many geographical locations; all ADS-B ground stations will be installed by 2013. While radar coverage is limited, ADS-B accurately follows aircraft flying over, say, the Gulf of Mexico with stations located on oil drilling platforms; they’ve a range of 200 nautical miles. Active ADS-B ground stations are in Louisville, KY; Houston, TX; the Florida peninsula; and Philadelphia, PA.

ADS-B systems provide information for both properly equipped aircraft and ATC, which is accomplished by ADS-B ‘IN’ and ADS-B ‘OUT’. The term ADS-B OUT speaks to the data that is broadcast from the aircraft and is used by ATC to locate and identify aircraft; ADS-B OUT is the only functionality mandated by 14 CFR 91.225 and 91.227. ADS-B IN is a situational awareness tool for the aircraft; it allows the aircraft to see other aircraft around it and displays this information for the pilot(s). ADS-B IN is optional; it’s not included in the regulations.

The equipment

Equipment-wise, ADS-B is a separate entity from the transponders being used on most aircraft today. On air carrier aircraft it can be a single box unit that houses the ADS-B, Transponder Mode S and TCAS or it can be a stand-alone datalink processor that interfaces with other systems. In GA aircraft it can be a universal access transceiver (UAT), but there won’t be stereotypical ADS-B equipment. The installation of an ADS processor in a line replaceable unit will need to interface with input components like a global positioning system (GPS), flight management computer (FMC), and air data computer (ADC). If the aircraft is currently operating with a GPS and Mode S at 1,090 Megahertz (MHz), it will interface with them.

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