Unmanned aircraft are a vital asset in today’s world. They have made aerial photography and videography cheaper and more accessible to both hobbyists and small business owners.
Today, the major hurtle is UAS integration into national airspace (NAS). One of the major aspects to integration of UAS into NAS is the ability for systems to sense and avoid other aircraft or obstacles. In the current FAA regulations, the term “see and avoid” exist, but in the future “sense and avoid” will be applied (Carey, 2013). Until that point UASs are unable to comply with the requirements, but this has not stopped companies and the military from working towards smart solutions to the providing a sense and avoid system that are dependable enough to garner FAA approval and support.
The techniques for monitoring separation from both manned and unmanned systems come in multiple forms. The overarching concept, regardless of technique, is that the UAS is informed of nearby traffic and can execute a predictable solution that will provide regulatory separation. The two major techniques to gathering this traffic information can be categorized as ground based or airborne based sensing. Ground based sensing utilize radar systems similar to air traffic control agencies. The major difference is that these radar systems integrate directly into the ground control station (GCS) of the UAS (SRC Inc. 2016). The airborne technique relies on advanced sensors being equipped directly on the air vehicle portion of the UAS. A lot of research is going into the development of micro radar systems that would be able to fit a highly capable radar system into a very small package (Gorwara, 2014).
Some of the major considerations that need to be factored in when deciding between ground based sensing or airborne sensing needs to be attributed to both the size and type of UAS airframe in questions. Small UASs need to be very cognizant of size power and weight of any additional sensors that need to be added to the air vehicle. These systems may benefit from a ground based system that is able to communicate with the ground control station. Additionally, micro radar systems are being produced to provide small quadcopter sized UASs with a robust ability to sense and avoid traffic with light weight and low power solutions (Gorwara, 2014). Large UASs like military grade UASs have a large payload capacity and a large power source capable of both carrying and powering complex sensors that can provide adequate sense and avoid capabilities. Another aspect to consider is the type of airframe in question. A small quadcopter may move slowly and within a relatively small range. This means less powerful sensors could be used to provide the separation and spacing required. Large fast fixed wing system could fly at high altitudes and at high speeds with an enormous range, so providing powerful onboard solutions may make the most sense.
Some larger systems like the MQ-4 global hawk actually have terminal collision and avoidance system (TCAS) which is used on most large commercial manned aircraft. There is also research into a new system call Airborne Collision Avoidance System for Unmanned Aircraft or ACAS Xu for short. This system will integrate with TCAS as well as provide autonomous functions that will support proper sense and avoid decision making if the UAS has lost link or is in autonomous flight (NASA, 2015).
Another current initiative is the use of a system called the ground based sense and avoid system (GBSAA) by SRC Inc. This system is currently being installed by the US Army at posts that are hubs for large UAS training. Fort Hood and Fort Campbell are both test beds for this technology (Mishory, 2016). The system utilizes powerful and expensive ground based radar dishes to directly communicate any traffic advisories directly to the GCS of the UASs operating within its area of responsibility. This system can detect both manned and unmanned aircraft as well as other airborne obstacles. The benefits of this system are that just one GBSAA can provide coverage for multiple aircraft working in a defined area. Also, GBSAA does not add any additional power or weight requirements to the actual air vehicles that are utilizing its information (SRC Inc., 2016).
Regardless to size and type, the need for FAA approved sense and avoid systems is vital to the integration of UAS into NAS. By understanding the limitations and capabilities associated with the size and type of a UAS will help engineers provide the best solution to each system on a case by case basis. The need to ensure the right capability is equipped on the right system is also vital in reducing excess costs and ensuring the general UAS user base is capable and willing to equip their UASs with these systems when it becomes available. Additionally, integrating the UAS sense and avoid technology into manned sense and avoid systems like TCAS will be vital to future integration.
References
Carey, B. (2013, June 22). FAA Plans Unmanned 'Sense and Avoid' Rule in 2016. Retrieved
October 03, 2016, from http://www.ainonline.com/aviation-news/air-transport/2013-07-22/faa-plans-unmanned-sense-and-avoid-rule-2016
Gorwara, A. (2014). Doppler micro sense and avoid radar. Retrieved October 3, 2016, from http://pmi-rf.com/documents/DopplerMicroSenseandAvoidRadarPaper.pdf
Mishory, J. (2016, June 16). Initial UAS flights using GBSAA system at Ft. Hood have been delayed. Retrieved October 03, 2016, from https://insidedefense.com/daily-news/initial-uas-flights-using-gbsaa-system-ft-hood-have-been-delayed
NASA. (2015, January 25). NASA, FAA, Industry Conduct Initial Sense-and-Avoid Test. Retrieved October 03, 2016, from http://www.nasa.gov/centers/armstrong/Features/acas_xu_paves_the_way.html
SRC Inc. (2016). Ground-Based Sense and Avoid Radar System. Retrieved October 03, 2016, from http://www.srcinc.com/what-we-do/radar-and-sensors/gbsaa-radar-system.html
Showing posts with label risk mitigation. Show all posts
Showing posts with label risk mitigation. Show all posts
Tuesday, October 4, 2016
Wednesday, August 17, 2016
Sense and Avoid Technology for UASs... Risk Mitigation vs. Complete Risk Avoidance
The integration of
unmanned aerial systems (UASs) into national airspace (NAS) has been an ongoing
process that is slowly but surely making small steps to a future filled with
UASs. There are multiple facets that make integrating UASs into NAS a
complicated process. Questions that deal with aircraft registration, operator
training, ethical responsibility, hacking and lost link procedures are all on
the table when it comes to integration into NAS. One topic that has been at the
front and center of the integration process is sense and avoid standards and responsibilities
for UASs. Companies like Amazon, Google, and Intel are all working solutions to
this challenge, but the Military and government entities like NASA are also
looking for solutions to getting more robust sense and avoid technology into
the skies fast.
Currently in Part 91.113
of the federal aviation regulation, it lays out the rules of the sky in terms
of right of way for all aircraft. One key verbiage used is that aircraft must “see
and avoid”. This does not include the ability to sense and avoid, which is the
method by which a UAS would accomplish this same task. Due to this, these
regulations are very limiting to UAS operation. For military UAS this means
that we must have visual observers that are trained and qualified observing the
aircraft at all times while operating in NAS. This creates a huge logistical addition
to typical training missions and is a cumbersome task to accomplish when it
comes to personnel and crew management. It is reported that the FAA is
attempting to alter Part 91.113 this year in order to include sense and avoid
technology as a legal substitute for see and avoid (Carey, 2013).
The Army specifically has
been working with a ground based sense and avoid system (GBSAA) to augment
their ability to fly in NAS. I have worked with this technology during my time
as a UAS commander in the Army and have seen how beneficial proper
implementation could be for units stationed in the US. GBSAA works very similarly
to ground based ATC radar systems, the only difference is that it is completely
dedicated to a particular UAS mission. The radar picture of both participating
and non-participating aircraft is collected via LSTAR ground sensors and
overlaid on the ground control station’s display and moving map that is utilized
by the operator to navigate the UAS (SRC Inc., 2016). When fully functional and
approved by the FAA, this system would allow the Army to fly large UASs through
Military Operations Airspace (MOA). For locations like Fort Campbell, Kentucky,
this would greatly expand the operational area for the multiple UAS units
stationed there.
Depiction of Ground Based Sense and Avoid System by SRC Inc.
In the civilian sector,
there is a greater focus on autonomous sense and avoid capabilities. This technology
will allow for smaller UASs to go further and farther than ever before. For
companies like Amazon, who want to be able to deliver merchandise via UAS, it
will be imperative that they can utilize autonomous drones that will legally be
authorized to travel beyond line of sight as long as they are equipped with autonomous
sense and avoid technology (Popper, 2016).
Regulators are attempting
to find a perfect answer to the sense and avoid issue, but the technology is
currently very good, but not perfect. Some argue that the technology needs to
be better, while others argue that aviation has always been about risk mitigation
and not risk avoidance. Companies like Intel have produced sense and avoid
systems that could reduce risk nearly to zero, but not promise a perfect solution
to every scenario (Popper, 2016). Many feel that the same risk acceptance
levels applied to manned aviation should be carried over to unmanned aviation rather
than attempting to create a more stringent and difficult standard to achieve.
What do you think is the best way forward? Please feel free to respond in the
comments section below.
References:
Carey, B. (2013, July 22).
FAA Plans Unmanned 'Sense and Avoid' Rule in 2016. Retrieved August 17, 2016,
from http://www.ainonline.com/aviation-news/air-transport/2013-07-22/faa-plans-unmanned-sense-and-avoid-rule-2016
FAA. (2004). Part 91
GENERAL OPERATING AND FLIGHT RULE. Retrieved August 17, 2016, from http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/0/934f0a02e17e7de086256eeb005192fc!OpenDocument
Popper, B. (2016, January
16). What's really standing in the way of drone delivery? Retrieved August 17,
2016, from http://www.theverge.com/2016/1/16/10777144/delivery-drones-regulations-safety-faa-autonomous-flight
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