Pilotless Drones: Background and Considerations for Congress Regarding Unmanned Aircraft Operations in the National Airspace System
Congressional research reportSep 10, 2012
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Pilotless Drones: Background and
Considerations for Congress Regarding
Unmanned Aircraft Operations in the
National Airspace System
Bart Elias
Specialist in Aviation Policy
September 10, 2012
Congressional Research Service
7-5700
www.crs.gov
R42718
CRS Report for Congress
Prepared for Members and Committees of Congress
Unmanned Aircraft Operations in the National Airspace System
Summary
Growing interest in the use of unmanned aerial vehicles (UAVs), particularly for homeland
security and law enforcement applications, has spurred considerable debate over how to
accommodate these unmanned aircraft and keep them safely separated from other air traffic.
Additionally, the use of these pilotless aircraft, popularly referred to as drones, for aerial
surveillance and law enforcement purposes has raised specific concerns regarding privacy and
Fourth Amendment rights and potential intrusiveness. These issues have come to the forefront in
policy debate in response to provisions in the FAA Modernization and Reform Act of 2012 (P.L.
112-95) that require the Federal Aviation Administration (FAA) to begin integrating unmanned
aircraft into the national airspace system by the end of FY2015.
While drones have been used extensively by the military and small radio-controlled model
aircraft have been around for more than 50 years, advances in more complex vehicle controls and
imaging sensor capabilities are spurring public sector and commercial interest in unmanned
aircraft for a variety of purposes, including law enforcement, homeland security, aerial imaging,
and scientific research. FAA currently approves public entities (such as federal agencies, public
universities, and local police departments) to operate UAVs on a case-by-case basis, but growing
interest is making this approach increasingly untenable. Moreover, commercial users are seeking
authorization to fly drones, but so far FAA has only allowed test and demonstration flights by
manufacturers. FAA faces a number of challenges to address anticipated growth in demand for
civilian UAV operations and develop regulations governing the certification and operation of
unmanned aircraft systems in domestic airspace.
Congress has generally supported efforts to integrate unmanned aircraft into the national airspace
system and foster growth in the unmanned aircraft industry. It enacted extensive provisions in
P.L. 112-95 that are designed to streamline and accelerate the operation of unmanned aircraft in
domestic airspace by both public entities and commercial operators. Notably, that law requires
FAA to issue regulations pertaining to the operation of small UAVs (weighing less than 55
pounds) and requires FAA to create and implement a plan to begin the integration of unmanned
aircraft into the national airspace system by the end of FY2015. Toward that goal, the act requires
FAA to establish six test ranges throughout the United States to study unmanned aircraft
integration technical issues.
The act establishes an ambitious timeline for FAA to grapple with and resolve a number of
complex issues regarding the safety and security of unmanned aircraft operations. Furthermore,
aircraft operators have expressed specific concerns that drone operations should not result in
airspace restrictions or other measures that could limit accessibility to the national airspace
system.
In addition to these various challenges, the privacy implications and potential intrusiveness of
drone operations have emerged as a significant issue before Congress. Civil liberties and privacy
groups have cautioned that voluntary industry measures, including a code of conduct to, among
other things, respect privacy, are inadequate to assure that drones will not be misused in ways that
could infringe upon the privacy of individuals and intrude upon their daily activities. Moreover,
FAA’s authority over specific uses of civilian unmanned aircraft appears limited so long as safety
and national security are not compromised, raising additional concerns that future drone
operations could lead to complaints and lawsuits over noise, intrusiveness, and interference with
the use and enjoyment of public or private property.
Congressional Research Service
Unmanned Aircraft Operations in the National Airspace System
Contents
Background...................................................................................................................................... 1
Military Roots............................................................................................................................ 1
From Longtime Hobby to a Burgeoning Civilian Market ......................................................... 2
Congressional Interest and Related Legislation............................................................................... 4
UAVs in Vision 100—The Century of Aviation Reauthorization Act ....................................... 4
Provisions of the FAA Modernization and Reform Act of 2012 ............................................... 5
Current FAA Policy and Oversight .................................................................................................. 5
Current Approvals Process ........................................................................................................ 6
Regulating Small Unmanned Aircraft ....................................................................................... 6
Wide Scale Integration of Unmanned Aircraft in Domestic Airspace....................................... 7
Domestic Airspace Integration Issues.............................................................................................. 7
Safety Concerns......................................................................................................................... 7
Sensing and Avoiding Other Air Traffic.............................................................................. 8
Mitigating Risks to Persons and Property on the Ground ................................................... 9
Human Factors Considerations ......................................................................................... 10
Operator Training and Qualification ................................................................................. 11
Addressing Potential Security Risks........................................................................................ 12
Drone Weapons ................................................................................................................. 12
Intentional Hacking and Signal Jamming ......................................................................... 12
Availability and Protection of Radiofrequency Spectrum................................................. 13
Responsibility for Security Issues ..................................................................................... 14
Airspace Restrictions............................................................................................................... 15
Industry Initiatives ......................................................................................................................... 16
Eyes in the Sky: Sensor Payloads .................................................................................................. 17
Cameras and Electro-Optical Imagers..................................................................................... 17
Infrared Sensors....................................................................................................................... 17
Synthetic Aperture Radar ........................................................................................................ 18
Specialized Sensors ................................................................................................................. 19
Concerns over Privacy and Intrusiveness ...................................................................................... 19
Figures
Figure 1. A Variety of Small to Medium-Sized Unmanned Aircraft Designs.................................. 3
Figure 2. An Electro-Optical/Infrared (EO/IR) Sensor Housed in a Pod Mounted on an
MQ-9 Predator B/Reaper Drone Operated by Customs and Border Protection (CBP) .............. 18
Contacts
Author Contact Information........................................................................................................... 21
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Unmanned Aircraft Operations in the National Airspace System
Background
In the early 2000s, military and intelligence use of unmanned aircraft systems (UASs)1 in
Afghanistan and Iraq spurred interest in potential domestic use of these systems. The safe
integration of unmanned aircraft in the crowded airspace above the United States poses a number
of regulatory challenges for the Federal Aviation Administration (FAA) and raises some unique
legal and ethical questions. These issues have come to the forefront following enactment of the
FAA Modernization and Reform Act of 2012 (P.L. 112-95), which requires FAA to begin
integrating unmanned aircraft into the national airspace system by the end of FY2015.
Military Roots
While much of the policy debate surrounding civilian use of unmanned aircraft is new, unmanned
aircraft have been used by the military since the early days of aviation. During World War I, the
Navy funded research to develop a prototype flying bomb called the Hewitt-Sperry Automatic
Airplane. Building on this concept, the first full-scale powered unmanned aerial vehicles, the
Curtiss-Sperry Flying Bomb and the Kettering Aerial Torpedo, nicknamed the “Bug,” were
developed in 1918 as unpiloted bomb delivery platforms. The “Bug” was designed to fly a pre-set
course, then shed its wings delivering an explosive payload that would detonate on impact. It was
never used in combat, and further development was halted in the 1920s.2 As evidenced by these
early prototypes, the U.S. military has long had an interest in unmanned aircraft, which evolved
into the development of several successful guided missile designs during World War II.
The military has used autonomous target drones and remotely piloted vehicles extensively since
the 1950s. These vehicles first served as targets for training combat pilots and as decoys in
combat arenas, but their roles evolved with advances in sensor technology, allowing them to take
on more advanced aerial reconnaissance roles.
In the 1980s, spurred by Israeli initiatives, the military developed more sophisticated unmanned
systems with extensive ground-based command and control capabilities. Unmanned aircraft were
used by U.S. forces for intelligence missions in the Balkans in the late 1990s, and in Afghanistan
and Iraq for reconnaissance and surveillance as well as, more recently, for combat missions.3 In
support of military research, development, testing, and training, the military now operates
unmanned aircraft extensively in U.S. airspace. The military services work closely with FAA to
designate special use airspace for conducting unmanned aircraft operations, typically over
military bases or sparsely populated land.
1
Unmanned aircraft systems (UASs) refer to aircraft that fly without onboard pilots along with ground control stations,
networks, and personnel needed to operate these aircraft. Unmanned aerial vehicles (UAVs) refer to the unmanned
aircraft in these systems, which are often referred to as drones in the media. The terms UAVs, unmanned aircraft, and
drones are used interchangeably throughout this report.
2
Kettering Aerial Torpedo Bug, Fact Sheet, National Museum of the Air Force: Dayton, Ohio, available at
http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=320.
3
For further information on military and intelligence UASs see CRS Report R42136, U.S. Unmanned Aerial Systems,
by Jeremiah Gertler.
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Unmanned Aircraft Operations in the National Airspace System
From Longtime Hobby to a Burgeoning Civilian Market
Until recently, civilian interest in operating unmanned aircraft in U.S. airspace had largely been
limited to long-standing hobbyist use of radio-controlled model aircraft. The Academy of Model
Aeronautics, a national organization representing model aviation enthusiasts, was founded in
1936 and claims a membership of more than 150,000.4 It serves as the chartering organization for
more than 2,400 model airplane clubs across the United States. At present, radio-controlled model
aircraft operate under a voluntary standard that generally permits flights only below 400 feet
above the surface. These guidelines specify that model aircraft be flown away from populated
areas and not in close proximity to full-scale aircraft. They further request coordination with air
traffic facilities when planning operations within 3 miles of an airport and suggest that model
aircraft be adequately flight tested before being operated in front of spectators.5
While most radio-controlled model aircraft are powered by small propeller engines and weigh
only a few pounds, some are jet-powered scale models weighing over 100 pounds. The distinction
between functional model aircraft and small unmanned aerial vehicles is, therefore, largely based
on an aircraft’s use rather than its size or capabilities: whereas model aircraft are regarded as
being used for recreational purposes, UAVs serve public use missions, such as law enforcement
and disaster relief, and commercial applications. The prospect of robust growth in use of UAVs
had triggered more formal analysis of the process for granting approvals and development of
regulations for UAV operations. The challenges associated with safely integrating civilian UAVs
into domestic airspace are discussed in detail below (see “Domestic Airspace Integration Issues”).
Flight missions considered to be “dirty, dull, or dangerous” are regarded as prime candidates for
the use of unmanned aircraft. Examples include aerial surveillance missions for homeland
security, border protection, and law enforcement; highway traffic monitoring; forest fire scouting;
disaster response; aerial applications of pesticides; pipeline and transmission line inspection;
aerial surveying and geospatial imaging; atmospheric and environmental science; wildlife and
natural resources management; scientific data collection; and hurricane and severe storm
monitoring. Some industry experts foresee eventual use of unmanned aircraft for cargo transport.
At this point, however, passenger-carrying UAVs are not on the horizon.
Industry analysts anticipate a robust market for unmanned aircraft systems, although the extent to
which civilian sales will contribute to this market is highly dependent on how the regulation of
civilian drones proceeds. The Teal Group, an aviation and aerospace consulting firm, predicted
that, over the next ten years, annual spending on unmanned aircraft systems and sensor payloads
will increase by 73% and worldwide spending on unmanned aircraft systems will total $89
billion, with the United States accounting for 62% of the research and development spending and
55% of procurement totals.6 Similarly, VisionGain, a UK-based business information provider,
foresees strong demand for unmanned aircraft payloads and subsystems, as well for UAV flight
training and simulation.7
4
For additional information see the Academy of Model Aeronautics (AMA) website at http://www.modelaircraft.org.
Federal Aviation Administration, Model Aircraft Operating Standards, Advisory Circular AC 91-57, June 9, 1981,
Washington, DC.
6
Teal Group Corporation, Teal Group Predicts Worldwide UAV Market Will Total $89 Billion in Its 2012 UAV Market
Profile and Forecast, available at http://tealgroup.com/index.php/about-teal/teal-group-in-the-media/3/79-teal-grouppredicts-worldwide-uav-market-will-total-89-billion-in-its-2012-uav-market-profile-and-forecast.
7
VisionGain, The UAV Payload and Subsystem Market 2012-2022, July 19, 2012, available at
(continued...)
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Unmanned Aircraft Designs
Unmanned aircraft come in all shapes and sizes. They range in size from bug-sized “nano drones” to vehicles the size
and weight of large business jets. Small UAVs have an upper weight limit of 55 pounds. Typical civilian drones are
likely to fall in the range of a few pounds up to that weight limit, while medium-sized unmanned aircraft, like the MQ9 Predator 2/Reaper (with a 65-foot wingspan and a maximum takeoff weight of about 10,000 pounds) may be used
on more specialized, medium-altitude and high-altitude, long-duration missions like border and maritime patrols and
environmental research missions. Unmanned aircraft include fixed-wing airplanes, helicopters, rotorcraft, and even
blimps. Unmanned aircraft may also include certain vehicles, referred to as optionally piloted vehicles, that are capable
of being flown by a pilot as a conventional aircraft or being operated remotely or autonomously depending on mission
conditions, needs, and requirements. Figure 1 provides a montage of various unmanned systems illustrating a range
of different vehicle sizes and designs including (clockwise from top left) the hand-launched AeroVironment RQ-20
Puma; an unmanned version of the Kaman K-MAX external load helicopter operated by the U.S. Marine Corps; the
Honeywell RQ-16 “Tarantula” T-Hawk; the AAI RQ-2 Pioneer; and the “Altair” variant of the General Atomics MQ-9
Predator 2/Reaper.
Figure 1. A Variety of Small to Medium-Sized Unmanned Aircraft Designs
Sources: Clockwise from top left, U.S. Army, U.S. Marine Corps, U.S. Army, U.S. Army, National
Oceanographic and Atmospheric Administration (NOAA).
(...continued)
http://www.visiongain.com/Report/857/The-UAV-Payload-and-Subsystems-Market-2012-2022; VisionGain, The UAV
Flight Training & Simulation Market 2012-2022, May 17, 2012, available at http://www.visiongain.com/Report/823/
The-UAV-Flight-Training-Simulation-Market-2012-2022.
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While a substantial portion of this market will be accounted for by the defense sector,
manufacturers are increasingly looking toward the civilian sector, fearing that military sales may
stagnate as operations in Afghanistan are scaled back and U.S. defense budgets grow tighter.
However, some forecasters have concluded that growth in the civilian market is unlikely until a
regulatory framework allowing routine UAS operations is established.8 FAA anticipates that once
such regulations are put in place, roughly 10,000 active civilian UASs will commence operations
within the first five years.9
It is important to distinguish public-use missions from purely civilian activities involving UAVs,
although certain commercial operations, such as utility line inspection, may serve a public
benefit. The distinction matters because aircraft owned or leased by federal and state agencies,
counties, and municipalities, are regulated differently from civil aircraft operated by private
individuals and corporations.10 Although the regulatory distinctions are complex, in general, FAA
oversight and authority over public-use aircraft are more limited. For this reason, some publicsector entities, particularly homeland security and law enforcement agencies and public
universities, are already making limited use of UAVs while the commercial market awaits FAA
regulatory action.
Congressional Interest and Related Legislation
Congress has generally been supportive of efforts to integrate unmanned aircraft into the national
airspace system and foster growth in the unmanned aircraft industry. Through oversight and
legislation, it has pushed FAA to accelerate its regulatory processes regarding the certification and
operation of unmanned aircraft.
UAVs in Vision 100—The Century of Aviation Reauthorization Act
In 2003, Congress included language in Vision 100—The Century of Aviation Reauthorization
Act (P.L. 108-176) specifying that the Next Generation Air Transportation System (NextGen),
which FAA is developing to handle air traffic control, shall “accommodate a wide range of
aircraft operations, including airlines, air taxis, helicopters, general aviation, and unmanned aerial
vehicles.”11 That language set the stage for ongoing policy and technical consideration of how to
best accommodate unmanned aircraft in the future airspace system.
While unmanned aircraft were only briefly mentioned in the act, the specific language requiring
that they be accommodated in the design of NextGen served as an important step toward
recognizing that drones would likely play a significant role in the aviation system of the future.
Nearly a decade later, unmanned aircraft have evolved considerably, and the importance of
8
U.S. Government Accountability Office, Unmanned Aircraft Systems: Use in the National Airspace System and the
Role of the Department of Homeland Security, Statement of Gerald L. Dillingham, Ph.D., Director, Physical
Infrastructure Issues, Before the Subcommittee on Oversight, Investigations, and Management, Committee on
Homeland Security, House of Representatives, July 19, 2012, GAO-12-889T.
9
Federal Aviation Administration, FAA Aerospace Forecasts FY2012-2032, p. 57.
10
49 U.S.C. §40125 specifies the qualifications for public aircraft status.
11
P.L. 107-76, Section 709c(6), italics added.
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considering them in aviation regulation and the design and operation of the national airspace
system has become a major policy and technical consideration.
Provisions of the FAA Modernization and Reform Act of 2012
During debate over the most recent FAA reauthorization, the integration of unmanned aircraft in
national airspace was an issue of considerable interest. The resulting legislation, the FAA
Modernization and Reform Act of 2012 (P.L. 112-95) contained extensive provisions designed to
promote and facilitate the use of civilian unmanned aircraft. These included mandates for
•
development of an integration plan that is to commence by the end of FY2015, if
not sooner, along with a five-year roadmap for achieving integration objectives;
•
selection of six test sites to study UAV integration into the national airspace
system;
•
designation of certain permanent areas in the Arctic where small unmanned
aircraft may operate 24 hours per day for commercial and research purposes,
including flights conducted beyond line-of-sight;
•
a simplified process for issuing authorizations for entities seeking to operate
public UASs in the national airspace system;
•
a collaborative process to incrementally expand airspace access as technology
matures and safety data and analysis become available, and to facilitate public
agency access to UAS test ranges;
•
a requirement to develop and implement operational and certification
requirements for public UASs by December 31, 2015; and
•
an exemption from rules and regulations pertaining to the operation of unmanned
aircraft for model aircraft weighing 55 pounds or less that are flown within visual
line-of-sight strictly for hobby or recreation.
Current FAA Policy and Oversight
The provisions in P.L. 112-95 reflect a general view that FAA’s slow progress to date on
addressing regulatory requirements for unmanned aircraft may be a barrier to civilian drone
operations. While FAA has been studying unmanned aircraft operations for almost a decade, it
continues to address requests to operate unmanned aircraft on a case-by-case basis. This approach
is becoming increasingly untenable as growing numbers of public and commercial entities seek
authorization to operate unmanned aircraft in domestic airspace.
On February 13, 2007, FAA issued a notice of policy declaring that “no person may operate a
UAS in the National Airspace System without specific authority.”12 This policy applies to both
public and private unmanned aircraft. FAA currently has two methods for granting authority to
operate unmanned aircraft, depending on whether the operator is a public or a private entity.
12
Federal Aviation Administration, “Unmanned Aircraft Operations in the National Airspace System,” Federal
Register, 72(39), February 13, 2007, 6689-6690.
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Current Approvals Process
Unmanned aircraft operated by the military or other federal, state, or local agencies must obtain a
Certificate of Waiver or Authorization (COA) from FAA. Since 2006, FAA has issued COAs to
more than 100 unique public entities throughout the United States, ranging from local fire
departments to research laboratories. Since the COAs have narrow scopes and durations, entities
must obtain new authorizations every few months. In 2009, FAA issued 146 such COAs. In 2010,
the number of COAs issued grew to 298.13 Although FAA has streamlined its approval process, as
required by P.L. 112-95, growing interest in operating unmanned aircraft from public entities is
expected to place strains on the current case-by-case approach to authorization.
Additionally, in much the same manner as manned aircraft developers and builders must obtain
FAA certification to test fly their aircraft, a number of drone developers have received special
airworthiness certificates in the experimental category. Special airworthiness certificates, which
offer the only legal route for private entities to operate unmanned aircraft for commercial
purposes, have been issued on a limited basis for flight tests, demonstrations, and training.
FAA has raised concerns that other civilian users are operating commercial UAVs under the
voluntary guidelines issued in the early 1980s that were intended to apply only to recreational
users of model aircraft. As previously described, these guidelines advise such users to maintain
altitudes lower than 400 feet above the ground, select sites away from populated and noisesensitive areas, give right of way to full-scale aircraft, and advise airport operators and air traffic
facilities if operating within 3 miles of an airport. The FAA statement of policy clarifies that these
general guidelines alone are not sufficient for commercial operators of unmanned aircraft,
regardless of the size of such aircraft. The FAA did, however, indicate that it has undertaken a
safety review to determine whether certain small, slow-moving unmanned aircraft could be safely
operated under a similar set of guidelines without requiring special airworthiness certification.
Regulating Small Unmanned Aircraft
Developers of small-scale unmanned aircraft are concerned that FAA has been moving too slowly
on measures to safely accommodate these types of aircraft. Since 2007, industry has been pushing
for separate regulations for “ultralight, low-speed, short-life UASs that will not be flying over
populated areas or in controlled airspace,” arguing that a one-size-fits-all approach to regulation
would not likely be effective given the wide range of systems being considered for civilian use.14
Other than streamlining the case-by-case approvals process, FAA has not taken any formal action
addressing the regulation of civilian small unmanned aircraft. After several delays, FAA plans to
release a proposed rule regarding the certification and operation of small unmanned aircraft
systems (sUAS) in October 2012, as a step toward meeting the August 2014 statutory deadline for
issuance of a final rule. Additionally, P.L. 112-95 directed FAA to assess whether certain
unmanned aircraft operations do not pose a safety hazard or a threat to national security and can
therefore safely be allowed. Actions to address this mandate are currently in progress.
13
Federal Aviation Administration, Fact Sheet: Unmanned Aircraft Systems (UAS), Updated July 2011, available at
http://www.faa.gov/about/initiatives/uas/media/UAS_FACT_Sheet.pdf.
14
David Hughes, “Civil Use of Unmanned Aircraft Systems Could Grow Rapidly,” Aviation Week and Space
Technology, February 12, 2007, p. 49.
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Wide Scale Integration of Unmanned Aircraft in Domestic Airspace
UAV manufacturers and users are seeking a regulatory structure for the certification of UAV
systems and approval for operation in domestic airspace. Ideally, operators of approved systems
want the ability to “file and fly,” meaning that they would be granted vehicle certification with
broad operating authority akin to current manned aircraft certification standards. Such regulation
would potentially allow unmanned aircraft operators to file routine flight plans, or in some cases
simply carry out flight operations without any specific notification requirements, much as
manned aircraft do.15 While FAA’s approach to address the mandates set forth in P.L. 112-95
regarding unmanned aircraft integration into the national airspace system is yet to be defined, it is
most likely that FAA regulation and oversight of UAVs will adopt an evolving, risk-based
approach toward this end goal of seamless integration.
As a first step, P.L. 112-95 mandated that FAA identify six test sites to specifically test concepts
and technologies for integrated unmanned aircraft operations. FAA held public meetings and
webinars and solicited public comments on the selection of test sites in March 2012, but has not
yet gone through a formal source selection process or announced further details regarding test site
selection, even though it was mandated to identify the sites by the summer of 2012 and have at
least one site operational by February 2013.
Under P.L. 112-95, FAA is also required to develop a comprehensive plan to safely accelerate
integration of civilian unmanned aircraft into the national airspace system as soon as practical but
not later than September 2015. Meeting this mandate will require extensive research and
regulatory action over the next three years.
Domestic Airspace Integration Issues
Key challenges to drone integration in domestic airspace include safety concerns, potential
security risks, and concerns regarding airspace restrictions and possible disruptions to manned
flight operations.
Safety Concerns
Threshold criteria for integrated unmanned aircraft operations are that UAVs do not pose undue
risk other aircraft or compromise safety to persons or property on the ground.16 To meet safety
objectives, UASs will require technology and standard procedures for sensing and avoiding other
air traffic under all possible scenarios, including lost communications. System reliability and
human factors are important systems design considerations, as are training and qualification
standards for drone pilots, unmanned aircraft systems operators, and other safety-critical
personnel.17
15
Katherine McIntire Peters and Beth Dickey, “Droning On,” Government Executive, October 15, 2004, pp. 68-76.
16
Federal Aviation Administration, Fact Sheet: Unmanned Aircraft Systems (UAS), Updated July 2011, available at
http://www.faa.gov/about/initiatives/uas/media/UAS_FACT_Sheet.pdf.
17
Drone pilots refers to ground personnel responsible for direct flight control of the unmanned vehicle whereas the
term systems operators refers to personnel responsible for operating sensor payloads or other aircraft systems, such as
fuel systems, that do not involve direct manipulation of flight controls or flight guidance systems. Other safety critical
(continued...)
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Sensing and Avoiding Other Air Traffic
Domestic airspace accommodates more than 70,000 flights per day18 at a variety of altitudes,
including low- and high-altitude military training flights, high-altitude air carrier and business jet
flights, medium-altitude commuter and general aviation flights, and low-altitude recreational and
sightseeing flights and helicopter operations. The risk of collision between these users and
unmanned aircraft must be adequately mitigated before unmanned aircraft can routinely utilize
the national airspace system.
The Government Accountability Office (GAO) concluded that no suitable technology is currently
available to provide unmanned aircraft, particularly small UAVs, with the detect, sense, and avoid
requirements needed to safely operate within the national airspace system. GAO noted that small
unmanned aircraft pose a particular challenge because they operate at low altitudes. Many other
aircraft operating at these altitudes do not use electronic transponders to broadcast their position
and altitude, and in any case many small UAVs lack the ability to receive transponder signals.
The needed equipment is simply too large and heavy to install on many small UAVs.19
Currently, these limitations substantially restrict UAV operations to line-of-sight scenarios, where
operators on the ground or spotters in chase planes can provide the necessary capabilities to
detect and avoid other air traffic. FAA is currently evaluating options for routinely allowing small
unmanned aircraft to use line-of-sight as an acceptable means to detect and avoid manned aircraft
under a regulatory regime for small UAVs.
For more sophisticated medium and large-sized UAVs seeking approval for operations beyond
line of sight, technology advancements are needed to assure safety in an environment shared with
manned flights. Remote sensing capabilities, including onboard cameras, airborne radars, and
equipment to interrogate aircraft transponder signals (similar to the traffic collision avoidance
systems on jetliners) can combine to provide operators with robust air traffic information.
An emerging technology, Automated Dependent Surveillance-Broadcast (ADS-B) will be
required on manned aircraft by 2020 and will serve as the principal means for aircraft tracking
under NextGen. Using ADS-B, aircraft will broadcast precise global positioning system (GPS)
location information to air traffic controllers and other air traffic, potentially including unmanned
aircraft. While ADS-B may provide unmanned aircraft operators with the capability to gather
precise position and flight path information for nearby air traffic in the future, backup systems
will likely be needed because ADS-B transmission and reception may not be guaranteed all the
time.
(...continued)
personnel may include maintenance personnel and equipment technicians that service the air vehicle, the ground station
or command and control linkages between the vehicle and the ground station.
18
Based on 2010 total combined aircraft operations at towered airports reported in Federal Aviation Administration,
FAA Aerospace Forecasts FY2012-2032. This does not include activity at non-towered airports and, therefore,
understates the total number of daily flights, for which there is no definitive count.
19
U.S. Government Accountability Office, Unmanned Aircraft Systems: Use in the National Airspace System and the
Role of the Department of Homeland Security, Statement of Gerald L. Dillingham, Ph.D., Director, Physical
Infrastructure Issues, Before the Subcommittee on Oversight, Investigations, and Management, Committee on
Homeland Security, House of Representatives, July 19, 2012, GAO-12-889T.
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FAA has not specifically approved any technology or suite of technologies as being sufficient to
provide acceptable “sense and avoid” capabilities.20 Part of the challenge is that existing
technologies do not assure avoidance capabilities under all operational conditions, including
autonomous UAV operations or in situations when UAVs lose their command guidance links with
ground control facilities. Standardized procedures for responding when UAV guidance has been
lost are currently lacking, but will be needed to ensure that air traffic controllers and airspace
managers can redirect nearby traffic and mitigate collision risks.
No single technology is likely to address the complex sense and avoid requirements that are
critical for unmanned aircraft integration. FAA has been working closely with RTCA, Inc., which
functions as a federal advisory committee on aviation technologies, to develop consensus
standards regarding minimum aviation system performance standards for sense and avoid
technologies as well as for command, control, and communications systems for unmanned
aircraft systems.21 RTCA has been performing this work under its standards committee on
unmanned aircraft systems (SC-203), which is scheduled to complete its work on these issues by
December 2013 and intends to publish recommended standards soon thereafter. These standards,
along with findings from unmanned aircraft integration testing, will likely form the basis of FAA
regulations and guidance regarding sense and avoid technologies and UAV operating procedures.
Mitigating Risks to Persons and Property on the Ground
In addition to risks to other air traffic, unmanned aircraft operations may pose a risk to persons
and property on the ground. Thus far, unmanned aircraft testing and operational use, such as for
military testing and training and for border and maritime patrol operations, have been conducted
largely over sparsely populated areas. In the future, however, law enforcement and commercial
users are expected to undertake flights over densely populated areas, a prospect which raises
specific concerns over safety procedures. For example, to minimize the likelihood of a crash
when communications, command, and control linkages between the vehicle and the ground
control station are disrupted, UAVs may need the ability to autonomously return to base.
Drone crashes, such as the 2006 crash of an MQ-9 Predator B drone operated by Customs and
Border Protection (CBP) near Nogales, NM, and the more recent crash of a Navy RQ-4A Global
Hawk near Salisbury, MD in June, 2012, have raised public concern over the safety of unmanned
aircraft operations. While drone safety has improved considerably over the past decade, the
accident rate for unmanned aircraft is still far above that of manned aircraft, although direct
comparisons are difficult, given that most drone operations examined have involved riskier flying
during development and testing and in war and conflict zones.22
The risk posed to persons and property on the ground is a function of both crash likelihood and
the potential consequences in terms of loss of life, injury, or property damage. While smaller
20
“Sense and avoid” refers to technologies and capabilities allowing unmanned aircraft to reliably detect other air
traffic and maneuver away from such traffic in a manner that adequately mitigates collision risks.
21
RTCA was organized in 1935 as the Radio Technical Commission for Aeronautics. Today it operates as a private,
not-for-profit corporation. Its recommendations are used by FAA as a basis for policy, program, and regulatory
decisions.
22
Roland E. Weibel and R. John Hansman, Safety Considerations for Operation of Unmanned Aerial Vehicles in the
National Airspace System, MIT International Center for Air Transportation, Department of Aeronautics and
Astronautics, Massachusetts Institute of Technology, Cambridge, MA, March 2005, Report No. ICAT-2005-1.
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UAVs may be expected to crash more frequently, the potential for catastrophic consequences is
less given that these vehicles do not weigh enough or carry enough fuel to cause major damage
on the ground. On the other hand, larger UAVs, like the MQ-9 Reaper or the RQ-4 Global Hawk,
can potentially cause as much damage as a mid- to large-sized corporate jet. However, safety
considerations in the design and operation of these more complex systems may reduce the
likelihood of a crash. Additional procedures that can be incorporated into safety regulations for
unmanned aircraft systems may further mitigate flight risks. These procedures may include
•
formal risk assessments for systems certification and mission planning;
•
development of ground impact models and mitigation plans to reduce risks to
persons and property on the ground;23 and
•
structured training and certification requirements for unmanned aircraft pilots,
systems operators, and other safety critical personnel.
Human Factors Considerations
The issue of training and certification requirements for unmanned aircraft systems personnel
raises a much broader issue regarding the role of humans in these systems. Indeed, the term
unmanned aircraft system (UAS) is a misnomer: while the aircraft themselves may be unmanned,
the systems needed to operate them safely depend extensively on human interaction. Although
drones operate without a pilot on board, human performance is a major consideration in setting
policy for the integration of unmanned aircraft systems in domestic airspace. Key human factors
to be considered include operator interfaces and controls and the training and qualifications of
drone pilots, systems operators, and other safety critical personnel.
The previously mentioned 2006 crash of a UAV operated by Customs and Border Protection
(CBP) illustrates the importance of these human factors considerations. On April 25, 2006, a
Predator B (MQ-9) drone crashed in a remote area along the U.S.-Mexico border near Nogales,
AZ following a loss of engine power. The National Transportation Safety Board (NTSB)
determined that the probable cause of the mishap was the drone pilot’s failure to follow
appropriate procedures when switching to an alternate control console in the ground control
station following a computer malfunction.24 The error resulted in the pilot inadvertently cutting
off the vehicle’s fuel supply.
CBP had only been operating the Predator B aircraft since September 2005, eight months prior to
the mishap. NTSB concluded that during this time CBP was providing a minimal amount of
operational oversight of its UAS program and cited its inadequate surveillance of the program as
a contributing factor in the crash.
The NTSB investigation revealed that, despite repeated computer malfunctions, neither CBP nor
its contractors had a program in place to ensure that maintenance tasks were performed correctly
or that corrective measures were applied. The NTSB investigation also found that while the
mishap pilot had only 27 hours of flight time with the Predator B model, and had only been given
23
Ibid.
National Transportation Safety Board, NTSB Identification: CHI06MA121, Aviation Accident Database &
Synopses, Probable Cause Approval Date: October 31, 2007. Available at http://www.ntsb.gov/aviationquery/
brief.aspx?ev_id=20060509X00531&key=1.
24
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verbal approval to fly the vehicle accompanied by an instructor pilot, the instructor pilot was not
present in the ground control station when the error occurred. NTSB further noted that the verbal
approval was not standard practice for CBP.
The incident illustrates that, despite the lack of an onboard pilot, human performance
considerations are critical in the design of unmanned aircraft systems. The failure that led to the
crash was preventable had the system been designed and operated with certain safeguards in place
to compensate for human fallibility. Greater attention to human factors considerations in the
design and operation of unmanned aircraft systems and in the development of training programs
and operational procedures could improve safety and facilitate the integration of unmanned
aircraft in the national airspace system.
Operator Training and Qualification
One particularly important human factors consideration for regulators is a determination
regarding training standards and minimum qualification requirements for personnel involved in
flight operations. The appropriate training and qualifications may depend in part on the size of the
aircraft and the complexity of the system, as a “one size fits all” approach may be inappropriate
given the diversity among vehicles, systems, and operational missions.
Currently the U.S. Air Force requires its Predator/Reaper and Global Hawk pilots to be pilot-rated
military officers.25 The other military services do not require drones to be operated by rated pilots,
but do require specialized training. It is uncertain how these different approaches may serve as a
basis for FAA to develop training requirements and qualification standards for civilian UAV pilots
and operators, as military approaches vary considerably and are tailored to specific systems and
missions.
One approach would be for FAA to develop basic training and certification standards for
operators of small UAVs, while requiring more elaborate training and certification requirements
for personnel seeking to operate or maintain large, complex unmanned aircraft systems. The
extent to which requirements for UAV personnel may overlap with requirements for piloting or
maintaining manned aircraft remains uncertain but could have significant implications for the
industry’s development. One perceived advantage of unmanned aircraft over manned aircraft is
lower operating costs, and mandating that unmanned systems have highly trained pilots and
operators with specialized certifications could reduce that potential cost advantage.
Another issue may involve medical certification. Medical conditions or poor eyesight preclude
some individuals from obtaining pilot certification, and the rigors of the flight environment
demand stringent medical requirements. Given the significant differences in the work
environment and the potential consequences of medical problems in an aircraft compared to
inside a ground control station, FAA may choose to relax some medical requirements to allow
certain individuals that would otherwise not be medically fit to fly to operate unmanned aircraft.
25
See CRS Report R42136, U.S. Unmanned Aerial Systems, by Jeremiah Gertler.
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Addressing Potential Security Risks
In addition to safety risks, the operation of civilian unmanned aircraft in domestic airspace raises
potential security risks, including the possibility that terrorists could use a drone to carry out an
attack against a ground target. It is also possible that drones themselves could be targeted by
terrorists or cybercriminals seeking to tap into sensor data transmissions or to cause mayhem by
hacking or jamming command and control signals.
Drone Weapons
Terrorists could potentially use drones to carry out small-scale attacks using explosives, or as
platforms for chemical, biological, or radiological attacks. In September 2011, the FBI arrested
Rezwan Ferdaus, a U.S. citizen from Ashland, MA, charging him in a terrorist plot to attack the
Pentagon and the Capitol using large model aircraft packed with high explosives. While the small
payload of the model aircraft may have limited the lethality of the explosions, Ferdaus planned to
recruit others to use assault rifles to target people fleeing the Pentagon after the drone attack.26 In
July 2012, Ferdaus pleaded guilty to attempting to provide material support to terrorists and
attempting to damage and destroy federal buildings by means of an explosive in a plea agreement
under which additional charges were dropped. The incident has raised specific concerns about
potential terrorist attacks using unmanned aircraft, although the payload capacities of small UAVs
would limit the damage these attacks could inflict using only conventional explosives.
Intentional Hacking and Signal Jamming
Additionally, unmanned aircraft command and control links could potentially be intentionally
jammed or hacked resulting in a loss or hostile takeover of control. For example, Todd
Humphreys, an assistant professor at the University of Texas at Austin, demonstrated a remote
hijacking of an unmanned aircraft by GPS guidance signals. In congressional testimony, he
warned that advances in software-defined radio and the availability of GPS signal simulators may
provide average hackers with the capability to interfere with unmanned aircraft operations.27
Humphreys recommended that non-recreational civilian unmanned aircraft weighing more than
18 pounds be required to have spoof-resistant navigation systems. More broadly, he
recommended that GPS-based timing and navigation systems used in national critical
infrastructure also be required to be spoof-resistant. He noted that while “[t]here is no quick, easy,
and cheap fix for the civil GPS spoofing problem…reasonable, cost-effective spoofing defenses
exist which, if implemented, will make successful spoofing much harder.”28 As a long-range
solution, he further recommended that the Department of Homeland Security commit to funding
the development and implementation of methods for performing cryptographic authentication of
GPS signals, or at least for the augmented GPS signals used for civil aviation.
26
Milton J. Valencia, “Ashland Man Faces Terrorism Charges,” Boston Globe, September 29, 2011.
Todd Humphreys, Statement on the Vulnerability of Civil Unmanned Aerial Vehicles and Other Systems to Civil GPS
Spoofing, Submitted to the Subcommittee on Oversight, Investigations, and Management of the House Committee on
Homeland Security, July 19, 2012.
28
Ibid. In this context, spoofing refers to transmitting false navigation signals that could cause a drone or aircraft to
veer off course.
27
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Additionally, GAO noted that “low cost devices that jam GPS signals are prevalent.”29 However,
it concluded that the issue could be mitigated by using additional navigation systems that do not
rely on GPS, and/or by encrypting communications and telemetry signals.
Availability and Protection of Radiofrequency Spectrum
GAO also noted that the lack of dedicated radiofrequency spectrum for UAS operations raises the
risk of lost communications links due to either unintentional or intentional signal interference.30
Issues regarding dedicated radiofrequency spectrum for unmanned aircraft, which sometimes
involve satellite control links, are typically addressed in an international forum to assure global
harmonization. The appropriate forum for such determinations is International
Telecommunication Union (ITU), the United Nations agency responsible for global information
and communications technologies.
In December 2009, ITU issued guidance on spectrum requirements for safe operation of
unmanned aircraft in non-segregated or integrated airspace. It concluded that unmanned aircraft
operations will require radiofrequency spectrum for air traffic control, vehicle command and
control, and sense and avoid capabilities.31 In November 2011, it published specific guidance on
the technical feasibility and advantages and disadvantages of several candidate frequency bands
for beyond line of sight communications, command, and control for unmanned aircraft systems.32
It did not formally consider or propose regulatory methods for how these frequency bands might
be allocated, which would be left up to individual regulatory authorities such as the Federal
Communications Commission (FCC) in the United States.
FCC has addressed radiofrequency licensing for UAVs on a case-by-case basis, much as FAA has
done for certifying drone flight operations. With continued demand for spectrum from mobile
broadband providers, securing dedicated radiofrequency spectrum for unmanned aircraft
operations is likely to be an ongoing challenge. Moreover, the protection of radiofrequency
signals to prevent potential hacking and spoofing through encryption and other methods has not
yet been adequately addressed and remains a threat to the security of unmanned aircraft systems
operations.
29
U.S. Government Accountability Office, Unmanned Aircraft Systems: Use in the National Airspace System and the
Role of the Department of Homeland Security, Statement of Gerald L. Dillingham, Ph.D., Director, Physical
Infrastructure Issues, Before the Subcommittee on Oversight, Investigations, and Management, Committee on
Homeland Security, House of Representatives, July 19, 2012, GAO-12-889T.
30
Ibid.
31
International Telecommunication Union, ITU-R Radiocommunication Sector of ITU, Characteristics of Unmanned
Aircraft Systems and Spectrum Requirements to Support Their Safe Operation in Non-Segregated Airspace, Report
ITU-R M. 2171, December, 2009, Geneva, Switzerland.
32
International Telecommunication Union, ITU-R Radiocommunication Sector of ITU, Frequency Sharing Between
Unmanned Aircraft Systems for Beyond Line of Sight Control and Non-Payload Communications Links and Other
Existing and Planned Services in the Frequency Bands 13.25-13.40 GHz, 15.4-15.7 GHz, 22.5-22.55 GHz and 23.5523.60 GHz, Report ITU-R M. 2230, November, 2011, Geneva, Switzerland.
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Responsibility for Security Issues
Under the Aviation and Transportation Security Act (ATSA, P.L. 107-71), responsibility for
aviation security was transferred from FAA to the newly formed Transportation Security
Administration (TSA) in 2001. TSA has not specifically addressed the potential security concerns
arising from the operation of drones in domestic airspace.
With regard to matters involving hacking and signal jamming, responsibility for the regulation
and oversight of system security is far more complex. While TSA maintains responsibility for
airspace security, FAA has regulatory authority over the certification of air vehicles. FAA has not
issued certification standards for unmanned aircraft and systems, but future FAA standards may
include hardware and software security and reliability assurance requirements.
FAA has worked closely with RTCA and the European Organization for Civil Aviation Equipment
(EUROCAE) to define software or information assurance criteria for aircraft systems, and RTCA
has released specific guidance on software considerations for airborne systems and equipment.
FAA has issued advisory information for aircraft and aircraft equipment manufacturers regarding
systems security and software assurance. This information indicates that the RTCA document is
only one guideline manufacturers may utilize in applying systems engineering principles to
ensure that aircraft component hardware and software are reliable and robust against hacking,
signal interference, and other threats.33
Additionally, the National Information Assurance Partnership (NIAP), a partnership between the
National Security Agency (NSA) and the National Institute of Standards and Technology (NIST),
has established common criteria for information technology systems evaluation. Systems meeting
the highest levels in the testing process are regarded as having “high robustness,” meaning that
they have stringent failure protections and rigorous security measures. Some avionics systems for
airliners are now being tested using these common criteria methods, although such testing is not
currently required. As the issue of unmanned aircraft systems certification is addressed, specific
requirements for hardware and software security could be put in place. Additionally or
alternatively, drone manufacturers may voluntarily apply various systems engineering and
information assurance methods, such as those specified in the RTCA guidance or in the NIAP
common criteria methodology, to protect systems against various information security threats.
As with many aspects of unmanned systems, a “one size fits all” approach may not be suitable,
and FAA and TSA may choose to adopt a risk-based approach in addressing security matters
related to unmanned aircraft operations. Under a risk-based approach, larger, more complex
unmanned aircraft may be required to adopt more specific systems security and software and
information assurance requirements, while more basic operational security procedures may
suffice for small UAVs weighing less than 55 pounds, for example.
In general, a comprehensive approach to security issues pertaining to unmanned aircraft systems
operations will likely require close coordination between TSA, FAA, FCC, manufacturers, and
operators to address security issues pertaining to systems hardware and software, radiofrequency
communications, and flight operations.
33
Federal Aviation Administration, Advisory Circular 20-115B—Radio Technical Commission for Aeronautics, Inc.
Document RTCA/DO-178B, January 11, 1993.
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Airspace Restrictions
Besides safety and security, the potential impact of drone operations on airspace accessibility for
other aircraft has been raised as a specific concern, particularly among operators of smaller
general aviation aircraft.
One significant difference between military unmanned aircraft and unmanned aircraft operated by
other public agencies or by civilian users is that the military, for many years, has negotiated with
FAA to set aside airspace designated for military training, testing, and other purposes. Military
airspace consists of military operations areas, military training routes, test ranges, and other
restricted or prohibited airspace. Military operations areas and training routes are typically
located in remote areas. While not set aside exclusively for military use, these areas and routes
are charted and documented, allowing other airspace users, especially smaller general aviation
aircraft, to be alert for military flight operations, including operations involving unmanned
aircraft. The military has also worked with FAA to set aside specific restricted and prohibited
airspace (e.g., above test sites and bombing ranges) to accommodate operations that pose greater
risks to other air traffic. This airspace is charted and documented to allow pilots to avoid these
areas when restrictions designating them as off limits to non-military users are in effect.
Airspace restrictions can serve as an effective tool for mitigating risks to civilian air traffic.
However, their use concerns some airspace users because they pose inconveniences and
sometimes raise additional safety issues. With additional restrictions, civilian pilots may be forced
to fly more circuitous routes, leaving pilots with fewer options to avoid bad weather or plan for
fuel stops. The Aircraft Owners and Pilots Association (AOPA), which represents more than
400,000 general aviation pilots and aviation enthusiasts across the United States, has been
particularly critical of the use of restricted airspace designations to separate unmanned aircraft
operations from other air traffic. AOPA has asserted that unmanned aircraft operations should not
have a negative impact on general aviation operations and should not require special airspace
designations, such as restricted airspace, for their operation.34 It, however, generally supports the
integration of unmanned aircraft so long as they do no harm to current manned operations.35
AOPA has been particularly critical of FAA’s issuance of temporary flight restrictions (TFRs) to
separate CBP drone operations for border surveillance from other air traffic. Testifying before the
House Subcommittee on Aviation at a March 2006 hearing, AOPA Executive Vice President for
Government Affairs Andrew Cebula stated that “AOPA believes that the use of ‘temporary’ largescale flight restrictions for yearlong UAV operations is not appropriate and the FAA needs to fully
explore the alternatives available to allow CBP (or any other agency for that matter) to secure our
borders without impacting the aviation community.”36
34
Aircraft Owners and Pilots Association, Regulatory Brief Unmanned Aircraft Systems, Updated January 31, 2008,
Frederick, MD, available at http://www.aopa.org/whatsnew/regulatory/unmanned.html.
35
Benet J. Wilson, “Integrating Manned, Unmanned Vehicles in Airspace System,” Aircraft Owners and Pilots
Association, Frederick, MD, available at http://www.aopa.org/advocacy/articles/2012/120608intregating-mannedunmanned-vehicles-in-airspace-syste.html.
36
Aircraft Owners and Pilots Association, Statement of Andrew V. Cebula, Executive Vice President, Government
Affairs Concerning Unmanned Aerial Vehicles in the National Airspace System, Before the Committee on
Transportation and Infrastructure, Aviation Subcommittee, U.S. House of Representatives, March 29, 2006.
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Industry Initiatives
The unmanned aircraft industry, collectively consisting of unmanned aircraft systems and system
component manufacturers and system operators, has been cognizant of concerns regarding the
operation of unmanned aircraft for civilian uses in domestic airspace. Collectively, the views of
drone developers and operators worldwide are represented by the Association for Unmanned
Vehicle Systems International (AUVSI). AVUSI has addressed many of the public concerns
surrounding UAV operations in a voluntary industry code of conduct issued in July 2012, which
is summarized in the text box below.
Voluntary Industry Code of Conduct for Drone Operations
In July 2012, the Association for Unmanned Vehicle Systems International (AUVSI) issued a voluntary industry code of
conduct for the operation of unmanned aircraft systems. The code of conduct addresses concerns raised by the
public and regulators regarding safety, professionalism, and respect.
With regard to safety, operators adopting the code commit to
•
operating in a manner that will not present undue risk to persons or property on the surface or in the air;
•
ensuring that vehicles are piloted by competent and properly trained individuals; and
•
ensuring that flights are conducted only after thorough risk assessments, including consideration of weather
conditions, potential failures and possible consequences, crew fitness for flight operations, airspace issues,
applicable aviation regulations, frequency spectrum requirements, and the reliability, performance, and
airworthiness of the aircraft.
With regard to professionalism, adopters of the code commit to
•
complying with all federal, state, and local laws, ordinances, covenants, and restrictions pertaining to unmanned
aircraft operations;
•
operating systems as responsible members of the aviation community;
•
being responsive to public needs;
•
cooperating fully with federal, state, and local authorities in response to emergency deployments, mishap
investigations, and media relations; and
•
establishing contingency plans for all anticipated non-normal events and sharing these plans openly with all
appropriate authorities.
Finally, with regard to respect, operators adopting the code commit to
•
respecting the rights of other airspace users;
•
respecting the privacy of individuals;
•
respecting the concerns of the public regarding unmanned aircraft operations; and
•
supporting improved public awareness and education regarding the operation of unmanned aircraft.
Source: Association for Unmanned Vehicle Systems International (AUVSI), Unmanned Aircraft System
Operations Industry “Code of Conduct,” Arlington, VA.
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Eyes in the Sky: Sensor Payloads
A central issue surrounding the use of unmanned aircraft is the airborne sensors, particularly
imaging sensors, that are mounted to the underbellies of these vehicles to gather data and collect
images of the earth below. While these sensors may be utilized for a variety of beneficial
applications, they have also raised considerable concerns regarding their potential intrusiveness,
despite the aforementioned industry commitments to respect the privacy of individuals (see
“Concerns over Privacy and Intrusiveness” below).
Cameras and Electro-Optical Imagers
Typical cameras and sensors placed on unmanned aircraft can collect data across a broad range of
the electromagnetic spectrum, both within and beyond the range of human vision. They can
provide aerial surveillance capabilities and spectral data under a wide range of lighting and
atmospheric conditions. In many cases, small UAVs used in surveillance applications are simply
equipped with commercial, off-the-shelf digital still photograph or video cameras. Usually, for
aerial work, high-end digital cameras with image stabilization are needed to provide detailed
resolution from a distance and avoid motion blur from the movement and vibration of the aircraft
and the camera platform. UAVs used for detailed earth imaging are fitted with more advanced
high resolution cameras. These cameras may have advanced optical features, including very large
digital imaging arrays, large zoom lenses, and advanced image stabilization capabilities, allowing
them to take highly detailed aerial photographs.
Captured videos and images may be transmitted for further processing or, in some cases, may be
processed onboard by computer vision and video analytic software. Analytics may include tools
such as scene motion detection and analysis, object detection capabilities, license plate readers,
and, possibly in some cases, facial recognition software.
Drones may also be equipped with electro-optical sensors that are specifically designed for aerial
operations. With regard to their imaging capabilities, electro-optical imagers are similar to highend consumer digital cameras and typically take either still or video images within the visual
electromagnetic spectrum, similar to human visual capabilities. Thus these sensors, like cameras,
provide eyes in the sky when operated in good daylight and twilight visual conditions, when not
obscured by clouds or fog.
Infrared Sensors
Cameras and electro-optical sensors cannot provide quality images during nighttime operations or
when operating in low visibility, such as in clouds or in fog. Therefore, to augment electro-optical
imaging capabilities and allow for imaging under a broader range of light conditions, sensor
platforms often also include two-dimensional infrared (IR) imaging arrays. Since the longer
wavelengths in the IR bands are not absorbed or attenuated by clouds or fog and are emitted by
warm objects at night, IR sensors are capable of providing images beyond the capabilities or
normal human sight. In the far infrared spectrum, passive millimeter wave sensors provide
thermal imaging capabilities particularly for night vision and thermal imaging applications. The
thermal sensing properties of IR sensors make them well suited for law enforcement and border
security applications, for example, for providing eyes in the sky for foot pursuits. IR sensors are
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also important for command and control of UAVs operated beyond line of sight, giving operators
improved situational awareness at night and in poor visibility.
Electro-optical and infrared sensors, collectively known as EO/IR sensors, are often housed
together in a turret pod with gyro-stabilized gimbals that allow the sensors to move, either at the
direction of a preprogrammed mission plan or from commands issued by a sensor operator
remotely controlling the device (see Figure 2).
Figure 2. An Electro-Optical/Infrared (EO/IR) Sensor Housed in a Pod
Mounted on an MQ-9 Predator B/Reaper Drone Operated by
Customs and Border Protection (CBP)
Source: Customs and Border Protection (CBP).
Synthetic Aperture Radar
In addition to passive EO/IR sensors, aircraft are sometimes fitted with active synthetic aperture
radar (SAR) antennas, which measure reflections of emitted microwaves to generate sensor
imagery. Real time SAR imagery can penetrate through rain, fog, smoke and dust, providing
surveillance capabilities in poor weather and in maritime and desert environments that can
augment or replace IR and millimeter wave sensors. Some civilian applications of SAR include
maritime search and rescue in adverse conditions, fire line tracking in smoke, iceberg detection
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and tracking, and oil spill monitoring.37 While SAR platforms had only been available for large
unmanned aircraft until recently, in 2008, defense contractors demonstrated a 2-pound SAR
payload for small UAVs that was made commercially available in 2010.38
Specialized Sensors
Although cameras, EO/IR, and radars are the most typical types of sensors for UAV applications,
unmanned aircraft can be equipped with other sensors for special applications. For example,
chemical, biological, or radiological sensors may be used to collect air samples in hazardous
environments. NOAA has equipped its UAVs with instruments to collect and analyze air samples.
Concerns over Privacy and Intrusiveness
While unmanned aircraft may carry a wide variety of sensor payloads for diverse applications,
cameras and imaging sensors have raised particular concerns among privacy advocates who fear
that widespread civilian unmanned aircraft operations could lead to abuses in monitoring,
tracking, and surveilling people throughout the courses of their daily lives. Civil liberties and
privacy groups including the American Civil Liberties Union (ACLU) and the Electronic Privacy
Information Center (EPIC) argue that aerial drones pose a unique threat to privacy.39 Proponents
of drones have countered these arguments by underscoring the many potential benefits of
domestic drone use. For example, aerial imaging of farm crops across multiple spectral bands can
provide data on crop conditions and may provide critical information on the impacts of drought
conditions or other factors affecting crop health. Drone proponents also contend that while
unmanned aircraft have been singled out in public policy debate, the sensor technologies, imaging
systems, and data collection capabilities in question are not unique to unmanned aircraft, as these
devices could just as easily be installed on manned aircraft, or on utility poles, cell phone towers,
and tall buildings.40
While the main focus of current public policy debate regarding drone use centers on the law
enforcement and government use of UAVs for surveillance purposes, additional concerns have
been raised regarding the commercial use of drones, including their potential use by marketing
firms, private investigators, and paparazzi. While such uses may be considered intrusive by many,
Fourth Amendment concerns would not specifically apply to data collections that are not
conducted by or on behalf of governmental entities. Besides tracking and surveillance activities
37
Mike Hanlon, “ScanEagle UAV Gets Synthetic Aperture Radar (SAR), GizMag, March 18, 2008, available at
http://www.gizmag.com/scaneagle-uav-gets-synthetic-aperture-radar-sar/9007/.
38
Ibid., “Insitu Announces Availability of NanoSAR—Synthetic Aperture Radar Payload.” BusinessWire, February 23,
2010, available at http://www.businesswire.com/news/home/20100223005511/en.
39
Jay Stanley and Catherine Crump, Protecting Privacy From Aerial Surveillance: Recommendations for Government
Use of Drones,” American Civil Liberties Union, New York, NY, December 2011; Testimony and Statement for the
Record of Amie Stepanovich, Association Litigation Counsel, Electronic Privacy Information Center, Hearing on
“Using Unmanned Aerial Systems Within the Homeland: Security Game Changer?” Before the Subcommittee on
Oversight, Investigations, and Management of the U.S. House of Representatives Committee on Homeland Security,
July 19, 2012.
40
For further information on the legal implications of domestic drone use, including Fourth Amendment and other
privacy concerns, see CRS Report R42701, Drones in Domestic Surveillance Operations: Fourth Amendment
Implications and Legislative Responses, by Richard M. Thompson II.
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that raise specific privacy concerns, civilian unmanned aircraft operations may raise additional
concerns regarding their potential intrusiveness. Various potential commercial uses, such as aerial
advertising (using drones to tow banners or display other targeted visual advertisements), may not
raise privacy concerns per se, but may nonetheless be regarded by some as intrusive and a
nuisance because of aircraft noise and visual distraction.
FAA’s authority over specific uses for civilian unmanned aircraft appears limited. As a matter of
law, aircraft have privileged access to navigable airspace. U.S. law generally maintains that equal
access and availability of navigable airspace to all users are basic principles underlying the
national airspace system, so long as safety and national security are not compromised. Notably,
49 U.S.C. Section 40101(c) (2) specifies that FAA, in carrying out its authority to regulate
aviation, shall consider the public right of freedom of transit through the navigable airspace.
Navigable airspace is defined in statute as that airspace above minimum flight altitudes
prescribed by regulation, including airspace needed to ensure safety during takeoff and landing.41
Away from airports, minimum altitudes defining navigable airspace are largely predicated on
safety concerns and depend on characteristics of the aircraft and risks posed to persons and
property on the ground. In general, navigable airspace is considered to be 500 feet above ground
level and higher, except in congested areas where the minimum safe altitude rises to 1,000 feet
above the highest obstacle within a 2,000-foot radius of the aircraft’s position at any given time.42
In sparsely populated areas and over water, navigable airspace can be considered to be much
lower, so long as operators assure that they can make an emergency landing after an engine
failure without undue hazard to persons or property on the ground. Moreover, helicopters,
powered parachutes, and powered hang gliders can be operated below established minimums so
long as operations are conducted without hazard to persons or property on the ground, and so
long as helicopters follow certain prescribed routes and altitudes when defined, usually for noise
abatement purposes. Minimum altitudes for drones are yet to be defined. However, unregulated
model aircraft are generally permitted below 400 feet, outside of navigable airspace for most
manned aircraft.
Small low-flying drones may pose particular concerns regarding intrusiveness, especially if they
become widely proliferated in urban and suburban areas. For example, it is imaginable that
drones displaying advertising material might hover noisily above a beach, or that a magazine
might deploy a drone equipped with high-resolution cameras to photograph a celebrity’s garden
party. As FAA is primarily concerned with balancing safety concerns with its obligation to
facilitate access to navigable airspace, it is likely to tread lightly with regard to matters pertaining
to the regulation of specific drone uses based upon their perceived intrusiveness.
Although FAA may be reluctant to address such issues, matters pertaining to the use of domestic
airspace generally fall exclusively within its purview. 49 U.S.C. §40103(a)(1) specifies that the
federal government has exclusive sovereignty of domestic airspace, thus significantly limiting
state and local governments from promulgating laws, regulations, or ordinances affecting access
to the national airspace system. This may make it particularly difficult for state and local
governments to restrict or regulate the use of drones, including imposing limitations on noise.
41
42
49 U.S.C. §40102(a)(32).
See 14 C.F.R. §91.119 Minimum safe altitudes: General.
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Unmanned Aircraft Operations in the National Airspace System
On the federal level, landowner rights with regard to the navigable airspace above private
property are similarly restricted. The Supreme Court has stated that “the air is a public highway,
as Congress has declared. Were that not true, every transcontinental flight would subject the
operator to countless trespass suits. Common sense revolts at the idea.”43
While the concept of the air as a public highway has largely overturned the ancient Roman
concept that the owner of a land also holds title to the air above, it does not preclude civilians
from potentially seeking civil remedies in the courts against aircraft operators flying overhead or
in close proximity to an individual’s land. This may potentially include civil action against private
or commercial drone operators, if damage or interference can be demonstrated. It may also
include claims against federal drone operators if the operations are considered to constitute a
taking of property by the government because the aviation activity results in a loss of use or a loss
of enjoyment of the property. The Fifth Amendment, among other things, protects citizens from a
taking of private property for public use without just compensation.
In these matters, case law relating to aircraft noise may have particular relevance to potential
landowner actions in response to nuisances and interference caused by drone operations.
Nuisance suits pertaining to aviation noise have allowed recovery for annoyance, inconvenience,
discomfort, and mental and emotional distress, as well as for property damage. Additionally,
citizens have been successful in actions against the federal government under the “just
compensation” clause of the Fifth Amendment in cases where federal aviation operations, usually
from military airbases or military training areas, have interfered with the use and enjoyment of
private land, thereby constituting a “taking” of the land without any formal exercise of powers of
eminent domain. To the extent that case law regarding aircraft noise from the early days of civil
jet air transportation may bolster potential legal challenges to drone operations, history suggests
that the introduction of civilian drones in the national airspace system is likely to be a highly
contentious matter.
Author Contact Information
Bart Elias
Specialist in Aviation Policy
belias@crs.loc.gov, 7-7771
43
United States v. Causby, 328 U.S. 256, 260-61 (1946).
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This is a copy of a public record, reproduced as it was published. It is not legal advice, and it may not be the version a court would rely on. Check the official source before you cite it.