As UAS use in the National Airspace (NAS) becomes more prevalent separation
of manned and unmanned aircraft, viewed in terms of collision avoidance, is an
issue that will become increasingly pertinent join the NAS. Automatic Dependent
Surveillance Broadcast (ADS-B) described in further detail in paragraph 2
provides an effective means of monitoring aircraft of all sizes and
configurations operating in the NAS. ADS-B
is not airframe or power plant specific and the FAA has mandated that most
aircraft be ADS-B equipped by the year 2020 (Marshall, 2013) thus making it a
logical choice for UAS implementation.
Autonomous avoidance maneuvering of fully autonomous aircraft presents
additional challenges as it requires integrated and automated collision avoidance
maneuvering capability. Remotely piloted
UAS could operate safely with a Sense and Avoid (SAA) capability such as that
displayed by General Atomics during testing last year on a Predator UAS
(Govers, 2013) or similar to that displayed by Sagetech Corporation (Sagetech
Corporation, 2012).
ADS-B
systems are highly accurate and relative to ground based radar relatively
economical (ADS-B explained, n.d.). ADS-B
is a transponder based system that automatically and continuously sends out a
signal providing aircraft position, altitude, heading, speed, and flight number
to any ADS-B capable ground station, aircraft or satellite (Marshall, 2013). ADS-B hardware can be compact with some
systems scaling in at 100 grams (Sagetech Corporation, 2012) making it suitable
for a wide variety of airframes both conventional and UAS.
Another technology currently in use by manned aircraft and suitable for limited
use in UAS is Traffic Alert and Collision Avoidance System (TCAS) however, TCAS
is at a size disadvantage for use in smaller UAS. System weights vary based on configuration
and manufacturer however for example one system in use on numerous commercial aircraft
weighs approximately 16 pounds without the antennae (TCAS 2000, n.d.) and
therefore would be unsuitable in smaller UAS and for larger UAS may require
compromise in other payload areas. It is
this disadvantage and the upcoming ADS-B requirement that makes ADS-B a more
suitable all around option.
Another option to safely integrate UAS into the NAS and avoid conflict
with manned aircraft is to create separate or tiered rulings based on aircraft
size and operational altitudes similar to rules currently in effect for recreational
UAS and model airplanes (Tadjdeh, 2014).
Based on statements by Jim Williams, the
FAA’s UAS Integration Manager, the FAA will likely adopt similar rulings
applicable to commercial use UAS by September 2015 (Tadjdeh, 2014). While details of the specific ruling have yet
to be announced Mr. Williams characterized the ruling as one which will allow
for significantly greater commercial utilization of airspace under 400 feet by
UAS (Tadjdeh, 2014).
Effective and safe integration of UAS into the NAS will require a
multi-faceted approach with consideration given to aircraft size, capability,
and mission requirements for both civil and government users.
References
ADS-B
explained. (n.d.). Retrieved from
http://www.trig-avionics.com/adsb.html
Govers, F. (2013, December 18). General Atomics tests UAV that can "sense
and
avoid" other aircraft. Retrieved
from http://www.gizmag.com/uav-sense-
avoid-test-general-atomics/30184/
Sagetech
Corporation. (2012, February 21). World's Smallest Mode S
Transponder with ADS-B Out, now available
from Sagetech Corporation.
Retrieved from http://www.sagetechcorp.com/news/worlds-smallest-mode-s-
transponder-with-ads-b-out-now-available-from-sagetech-
corporation.cfm#.VGb0ligx9JE
Tadjdeh,
Y. (2014, November 8). FAA Official:
Small Drone Rule to Be Released
by End of Year. Retrieved from
http://www.suasnews.com/2014/11/32567/faa-
official-small-drone-rule-to-be-released-by-end-of-year/
TCAS 2000.
(n.d.). Retrieved from http://www.acss.com/wp-
content/uploads/2012/03/TCAS-2000.pdf
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