UAS in the NAS

Separation of unmanned aerial vehicles in the national airspace continues to be an area not fully addressed causing delays in regards to the integration of UAS in NAS by the FAA. Mid air collisions still occasionally occur with manned aircraft more specifically in general aviation as seen most recently over the harbor in Los Angeles (Serna, J. 2016). Making the transition and having confidence in technology for sense and avoidance and separation once the pilot is removed from the cockpit is a huge leap that has been undertaken for some time now but without complete success, yet. Sense and avoid technologies currently are listed by the FAA as one of the top reasons for not meeting the deadline for UAS integration in the NAS in addition to data link and control station reliability, lack of air traffic control procedures, minimum air vehicle performance requirements, and inadequate framework for sharing and analyzing safety data (Hampton, M. 2014).

There are various sensor and sensing options currently available such as ADS-B which will be required on all transport aircraft by 2020 per the ongoing NextGen efforts that uses GPS to broadcast aircraft position and velocity in an accurate manner. ATC transponders which most aircraft carry is another method for tracking an aircrafts location based on interrogation of ground based radar which is a much older technology that’s been in use for years but has many shortcomings. Transponders and ADS-B only work if an air vehicle is equipped with them otherwise non-cooperative traffic would not be detectable. Other sensing technologies outside of the two most common are infrared cameras, primary radar, laser range finding, and acoustic processing (Angelov, P. P. 2012). Another issue arises based on group number. Smaller UAV’s found in group 1 and 2 may not be capable of being outfitted with a multitude of sensors due to weight and power restrictions. Regardless of group in order for SAA systems to be certifiable and successful in the NAS five key sensor parameters must be accounted for based on UAV type and environment. Filed of view, range, update rate, accuracy, and integrity are the critical components in a UAV sensing system that are currently being tested by various research groups such as the DoD, DARPA, and NASA (Angelov, P. P. 2012). The second element is the avoid aspect which involves threat identification and resolution. Collision avoidance involves the use of algorithms to determine the distance and space to maneuver to avoid a potential threat. Based upon airframe configuration the time in which an air vehicle must avoid a threat will be different. An electric multi rotor copter versus a fixed wing twin turbo fan would approach each other at very different speeds making threat identification and resolution decisions occur at different rates. Even with ongoing testing, we are still not at the point of seamless integration and the FAA still needs to set clear and concise standards.

Current technologies coupled with more advanced techniques could provide a solution for UAS integration but I believe using a technology like TCAS or ADS-B alone on a UAV would be oversimplifying the issue. More test data is required for confidently certifying a sense and avoid system or self-separation standard. Although the military has many UAV flight hours of experience the majority of time is spent flying in remote or desolate locations, not in our busy national airspace where traffic density continues to increase.


References

Angelov, P. P., & Books24x7, I. (2012). Sense and avoid in UAS: Research and
applications (2nd;1; ed.). Hoboken: John Wiley & Sons.

Austin, R. (2010). Unmanned aircraft systems: UAVS design, development,and deployment. Chichester, U.K: John Wiley & Sons Ltd.

Hampton, M. (2014). FAA’s Progress and Challenges in Integration of Unamanned Aircraft
Retrieved from
http://transportation.house.gov/uploadedfiles/2014-12-10-hampton.pdf

Serna, J. (2016). Mid Air Collsion off Coast Near LA Harbor. Retrieved from,
http://www.latimes.com/local/lanow/la-me-ln-la-harbor-plane-crash-20160205-story.htmlthe NAS.