Introduction
The Next Generation Air Transportation System (NextGen) is considered a comprehensive overhaul of the National Airspace System (NAS) across U.S. that the Federal Aviation Administration (FAA), in collaboration with other agencies, are undertaking (Paczan, Cooper, & Zakrzewski, 2012). There are three main goals of what NextGen strives to achieve. Firstly, it aims to enhance navigation so that air traffic routing can be more efficient and allow more air traffic in the same airspace while reducing fuel consumption and carbon emissions. Secondly, it allows enhanced collision avoidance mechanisms such that every aircraft knows the location of each other in space to be able to avoid colliding into each other. Finally, there will be better digital data communications between aircraft and ATC systems (Goyer, 2015). Initiated in 2004, NextGen program will cost an estimated $40b and is expected to take years of air traffic system modernization that will extend at least 25 years into the future (Houston, 2016).
Foundation of NextGen
Forming the foundation of NextGen is the Automatic Dependent Surveillance Broadcast (ADS-B) technology that is made compulsory for all air traffic users in controlled airspace starting 2020 according to 14 CFR 91.225 and 14 CFR 91.227 (AOPA, 2015). The main purpose of ADS-B is to provide better aircraft location information than traditional radar systems to air traffic controllers. The system will enable continuous and almost real-time broadcasting of aircraft position information through the use of GPS satellite signals. An ADS-B enabled aircraft will be able to retrieve GPS data and other avionics data from its sensors to create a precise location, speed, altitude, etc. to ATC and other participating aircraft, thereby enhancing situational awareness of airspace users. ADS-B has two functions namely ADS-B Out, and ADS-B In. ADS-B Out will be the function that is mandatory for all aircraft in most controlled airspace. Airborne systems equipped with ADS-B Out will transmit its own identification, altitude, airspeed and direction to ATC and surrounding aircraft. ADS-B In, on the other hand, will receive information from other aircraft ADS-B Out and display the information.
How will NextGen affect UAS
The increasing role of UAS in applications such as search and rescue, weather monitoring, agricultural applications, military training, etc. has led to the proliferation of UAS today. However, because there is a lack of common understanding of the requirements to operate UAS safely in NAS, the continued expansion of commercial UAS operations has been inhibited (JPDO, 2012). The planning and architecture of NextGen did not clearly define the introduction of UAS. However, in the roadmap to integrate civil UAS into NAS by DOT (2013), its long term activities are consistent with Joint Planning and Development Office (JPDO) concept and vision of NextGen. The roadmap specifically states the requirement for UAS operations to continue evolving based on NextGen requirements.
Due to the nature of current UAS technology, such as the sensory limitations, it will continue to remain a human factor challenge to provide intuitive traffic information to enhance situational awareness of UAS pilots. Nevertheless, UAS operations can still benefit from ADS-B Out when installed. The technology will allow UAS to be visible to ATC and other suitably equipped airspace user. UAS that are equipped with transponders and traffic collision and avoidance system (TCAS) will also be visible to other users so that they can receive warnings and perform any necessary collision avoidance maneuvers. Therefore, in any inadvertent scenarios of problematic command and control links between ground control stations (GCS) and UAS, the ADS-B communication link, which runs on a different frequency, can still be used as a backup to send instructions to the UAS (Contarino, Young & Contarino, 2015). At the same time, ADS-B can allow the broadcast of an unmanned aircraft (UA) that has encountered datalink problems to transmit its intent to ATC and other surrounding aircraft using this medium (Valavanis & Vachtsevanos, 2015).
Regarding the need to have comprehensive sense and avoid (SAA) capabilities, current cooperative SAA technologies such as TCAS and ADS-B, when installed on UAS, allows the broadcast of UAS information to other aircraft. However, according to Valavanis & Vachtsevanos (2015), ADS-B does not work on non-cooperative traffic over remote areas such as farmlands, where typical airborne systems use optical sensors, radar or laser scanners. Therefore, it will be a technical challenge ahead for such non-ADS-B equipped airborne systems where SAA is concerned to allow their utilization to be prevalent.
Conclusion
NextGen system will have to accommodate a wider range of aircraft systems such as UAS. It is well anticipated that UAS will be one of the main drivers of NAS demand growth. Therefore, promulgating technically sound UAS integration policies with related human factors considerations in the process is necessary. ADS-B equipage delays are also expected for NAS users with the current high costs of ADS-B equipment, particularly for those owners with low-value aircraft that see little benefits for ADS-B when they do low level flights for farming and other low altitude applications (AOPA, 2015). At the same time, it is still uncertain whether UAS operators are required to have their UA equipped with ADS-B Out. It will still be a long while before UAS can be fully integrated into NAS along with NextGen initiatives.
References
AOPA (2015). Air traffic services brief: Automatic dependent surveillance-broadcast (ADS-B). Retrieved from https://www.aopa.org/advocacy/advocacy-briefs/air-traffic-services-brief-automatic-dependent-surveillance-broadcast-ads-b
Contarino, V.M., Young, S.O., & Contarino, M.R. (2015). Economical safe operation of UAS using ADS-B and RADAR. Retrieved from http://www.auvsishow.org/auvsi2015/Custom/Handout/Speaker9515_Session1011_1.pdf
DOT (2013). Integration of civil unmanned aircraft systems (UAS) in the National Airspace System (NAS) roadmap. Retrieved from https://www.faa.gov/uas/media/uas_roadmap_2013.pdf
Goyer, R. (2015). What is nextgen? Why does it matter?. New York: Bonnier Corporation.
Housten, S. (2016). NextGen in a nutshell. This history and the highlights of the next generation air traffic system. Retrieved from http://aviation.about.com/od/ATC-Technology/p/What-Is-Nextgen.htm
JPDO (2012). NextGen research, development and demonstration roadmap. Retrieved from http://www.dtic.mil/get-tr-doc/pdf?AD=ADA561097
Paczan, N.M., Cooper, J., & Zakrzewski, E. (2012). Integrating unmanned aircraft into NextGen automation systems. Paper presented at the 8C3-1-8C3-9. doi:10.1109/DASC.2012.6382440
Valavanis, K.P., & Vachtsevanos, G.J. (2015). Handbook of unmanned aerial vehicles. New York: Springer
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