The
busy and often congested airspace over the United States accommodates
commercial, military, and recreational air traffic. With the addition of
Unmanned Aircraft Systems (UAS) to this airspace, current and future
stakeholders are concerned that the safety of air transportation will be at
risk. Pilots of all aircraft are required by law to maintain vigilance and
avoid other aircraft if weather permits1. Because the pilots of UAS
are removed from their aircraft, some other means of avoiding other aircraft would
be necessary to adhere to this regulation.
To
aid in separation, manned aircraft are monitored by Air Traffic Control (ATC)
by a variety of means. At large airports, Air Traffic Controllers sit in a
control tower, and elevated building with windows, and visually monitor the
aircraft. Controllers may also have a surveillance system such as a radar that
measures radio reflectance of aircraft to determine their position. These
aircraft may have equipment on-board (called a transponder) that transmits
augmentary information to the controller such as airspeed, altitude, aircraft
identification, and coordinates. Additionally, aircraft may carry a Traffic
Collision Avoidance System (TCAS) that alerts the pilot to nearby aircraft.
Aircraft may be controlled or uncontrolled, depending on the airspace they are
flying in and the type of flight. Controlled aircraft must fly in controlled
airspace, file a flight plan, and remain in communication with ATC.
Uncontrolled aircraft must fly in certain classes of airspace, do not file
flight plans, in most cases do not have to communicate with ATC, and must fly
in good weather.
In order to comply with the “see and avoid” requirement, the implementation of UAS into the national air space to date has involved keeping the UAS within the visual line of sight of an observer on the ground or in a manned chase aircraft. This observer must have direct communication with the pilot of the UAS in order to give commands to avoid aircraft. For some applications of UAS, this method is sufficient to carry out the task. However, the benefit of using UAS is often diminished by the limitation of a ground observer’s line of sight or the expense of concurrently flying a chase aircraft. The Federal Aviation Administration (FAA) is responsible for regulating the safety of air transportation in the United States. The FAA has moved slowly in implementing UAS, due to the complex nature of the problem and the risk of an accident. One might argue that the FAA might have chosen not to implement UAS at all, were it not for a mandate from Congress to integrate UAS into the National Airspace System (NAS) by 2015.
The FAA’s goal in integrating UAS into the NAS is to achieve
an equivalent level of safety to manned aircraft users of the airspace. To attain
this level of safety, it is important to understand the risks involved. If a
commercial airliner crashes, there is the potential for hundreds of fatalities
and property destruction. If a small recreational passenger plane crashes,
there are usually only a handful of fatalities, if any, and minimal property
damage. Accordingly, there are many more regulations governing the operation of
turbine-powered commercial aircraft than for recreational aircraft. UAS vary in
size from the Global Hawk, which has a wingspan of 116 feet, to the Hummingbird
UAS, whose wingspan is only 6.3 inches. While both of these platforms share the
issue of having the pilot removed from the aircraft, the potential for loss of
life and property vary greatly between them. For this reason, one set of
regulations will not be appropriate for all UAS.
The first step that the FAA will take in creating these
regulations for UAS is to divide them into categories. The FAA has already
stated that it will not regulate UAS used for recreational purposes (no size
limitation was imposed). Next, the FAA is expected to release rules for what it
calls small UAS, which are arbitrarily defined as 55 pounds or less. A “small
UAS rule” was expected to be released from the FAA in late 2014, but had not
been at the writing of this paper. For these small UAS, the FAA may still only
allow flights within visual line of sight.
The question remains of how UAS can operate in the NAS beyond
the line of sight of their operators. The aforementioned technology for
separation of aircraft can be employed by UAS in some cases. UAS large enough to
carry the equipment for broadcasting its position and receiving traffic data
may be able to meet the level of safety of manned aircraft. However, this
technology is only relevant when all aircraft are equipped. The FAA has
mandated that nearly all aircraft must be equipped with position-reporting
transponders by 2020 as part of its Next-Gen ATC system. These transponders are
becoming smaller, lighter, and cheaper allowing them to be used for small UAS.
While this Next-Gen system is put into place, would-be
operators of unmanned aircraft are calling for a solution. Companies that have
property and infrastructure spread out over large areas, such as pipeline and
power line companies, would like to survey these infrastructures with UAS.
Without some means of detecting and avoiding air traffic, this application will
likely have to stay within line of sight.
Until new technology becomes commercially available to reliably
detect, sense and avoid air traffic, the FAA’s limitations on UAS are going to
remain. The largest of UAS may be able to remain in positively controlled
airspace and rely completely on ATC for avoidance, but this still does not
represent an equivalent level of safety to manned aircraft. Many view the
forthcoming UAS regulations from the FAA as an inevitability, but the agency
that regulates the world’s safest form of transportation is not going to make
any hasty changes that could jeopardize that record.
1Code of Federal Regulations 14, Part 91.113(b)
References:
NASA
Armstrong Fact Sheet: Unmanned Aircraft Systems Integration in the National
Airspace System. (2014). Armstrong Flight Research Center. National
Aeronautics and Space Administration. Retrieved from: http://www.nasa.gov/centers/armstrong/news/FactSheets/FS-075-DFRC.html#.VN_R0PnF_ZI\
Sagetech
Unmanned Solutions. (2015). Sagetech, Inc. Retrieved from: http://www.nasa.gov/centers/armstrong/news/FactSheets/FS-075-DFRC.html#.VN_R0PnF_ZI
Air
Traffic NextGen Briefing. (2014). Federal Aviation Administration. Retrieved
from: http://www.faa.gov/air_traffic/briefing/
FAA
Reauthorization and Modernization Act of 2012. (2012). U.S. Government Printing
Office.
