Document ID: FAA-2011-1279-0022
Agency: faa
Document Type: Rule
Title: Airborne Wind Energy Systems Policy Statement
Posted Date: 2022-12-23T05:00Z

[Federal Register Volume 87, Number 246 (Friday, December 23, 2022)]
[Rules and Regulations]
[Pages 78849-78852]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-27993]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 77

[Docket No: FAA-2011-1279]

Airborne Wind Energy Systems (AWES) Policy Statement

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Policy statement.

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SUMMARY: FAA is finalizing its policy on the applicability of 
regulations concerning the safe, efficient use and preservation of the 
navigable airspace to all airborne wind energy systems (AWES).

DATES: This policy is effective December 23, 2022.

FOR FURTHER INFORMATION CONTACT: Brian Konie, Airspace Rules and 
Regulations Team, Air Traffic Organization, Federal Aviation 
Administration, 800 Independence Avenue SW, Washington, DC 20591; 
telephone: (202) 267-8783; email: [email protected].

SUPPLEMENTARY INFORMATION:

I. Statutory Authority

    Congress, pursuant to 49 U.S.C. 44718, mandated that the Secretary 
of Transportation require the public to provide notice to FAA of ``the 
construction, alteration, establishment, or expansion, or the proposed 
construction, alteration, establishment, or expansion, of a structure 
or sanitary landfill when the notice will promote (1) safety in air 
commerce; (2) the efficient use and preservation of the navigable 
airspace and of airport traffic capacity at public-use airports; or (3) 
the interests of national security, as determined by the Secretary of 
Defense.'' Moreover, under that section, the Secretary is required to 
conduct an aeronautical study to decide the extent of any adverse 
impact on the safe and efficient use of the airspace, facilities, or 
equipment if the Secretary decides that constructing or altering a 
structure may result in an obstruction of the navigable airspace, an 
interference with air or space navigation facilities and equipment or 
the navigable airspace, or, after consultation with the Secretary of 
Defense, an adverse impact on military operations and readiness. FAA 
codified these requirements in Title 14 of the Code of Federal 
Regulations (14 CFR) part 77 and identified the form and manner in 
which a person must submit notice.

II. Background

    In 2011, FAA published a notice of policy and request for 
information (Notice) stating its policy on the application of 14 CFR 
part 77 to temporary AWES.\1\ The Notice also contained a request for 
information from AWES developers and the public on these systems so 
that FAA can

[[Page 78850]]

comprehensively analyze AWES and evaluate the potential impacts of 
their long-term integration into the National Airspace System (NAS).
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    \1\ Notification for Airborne Wind Energy Systems (AWES), Docket 
No. FAA-2011-1279 (76 FR 76333, Dec. 7, 2011) (Notice).
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    The Notice stated that the Obstruction Evaluation process under 
part 77 applies to any new forms of wind gathering devices, including 
temporary AWES proposals.\2\ This allowed the FAA to gather data about 
these devices while the technology continued to develop.\3\ The notice 
explained that anyone proposing to conduct temporary airborne testing 
of AWES for data collection purposes must comply with part 77, 
including the requirement in section 77.13(a)(1) that requires notice 
of any construction or alternation of more than 200 feet above ground 
level (AGL).
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    \2\ Id. at 76334.
    \3\ FAA also stated in the Notice that it may address permanent 
and operational AWES under part 77 in the future after further 
evaluation and risk assessments.
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    Airborne wind energy (AWE) is the conversion of wind energy into 
electricity using tethered flying devices.\4\ An Airborne Wind Energy 
System (AWES) is a temporary or permanent structure, which consists of 
a self-supported airborne system tethered to a ground station, with an 
airborne or ground-mounted drivetrain used to convert kinetic energy in 
the wind to mechanical power for purpose of generating electricity. The 
tethered aspect of AWE provides the opportunity to harvest stronger and 
more consistent wind found at higher altitudes.\5\
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    \4\ www.energy.gov/eere/wind/articles/new-report-discusses-opportunities-and-challenges-airborne-wind-energy.
    \5\ Id.
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    While many AWES are similar in concept (designed to harvest kinetic 
wind and create consumable power), the technology and individual 
components, specifically the aloft portion, differ dramatically. 
Regardless of entity-specific design and potential resemblance between 
designs, each AWES possesses different attributes. Due to different 
attributes and impacts on NAS, FAA concluded that it must study each 
proposed AWES deployment on a case-by-case basis to analyze the 
surrounding aviation environment and ensure aviation safety.

III. Request for Information

    In the Notice, FAA identified concerns regarding AWES operations in 
the NAS, (e.g., conspicuity to aircraft via marking and lighting), 
desired operational airspace volumes, potential impact on various NAS 
facilities (e.g., communication, navigation, and surveillance), and 
overall safety. These concerns remain relevant to FAA's management of a 
safe and efficient NAS for all users.
    In addition to operational concerns, FAA also recognized the 
various design concepts AWES developers use for individual AWES 
components. These varying concepts include the components that keep the 
system aloft, the power-generating equipment, the energy-transferring 
equipment, the maneuvering controls, and the physical and operational 
dimensions. Given the variation in potential AWES design, operations, 
and technologies, FAA requested information from the industry in the 
Notice. Examples of information requested included design concepts and 
safety mechanisms; the type, material composition, and physical 
dimensions of mechanical devices employed to keep the system aloft; and 
long-term plans for this system. FAA also requested information to 
determine if proponents could comply with existing marking and lighting 
requirements and to discern how an AWES will be conspicuous to the 
flying public.

IV. Summary of Comments

    In response to the Notice, FAA received 20 comments during the 
comment period. Eight comments came from individuals and 10 comments 
came from major organizations or industry stakeholders. Six of the ten 
major organization or industry stakeholder commenters were from 
companies developing various types of AWES (Altaeros Energies, Inc., 
EnerKite GmbH, Highest Wind, LLC, Makani Power Inc., SkySails GmbH, and 
Windlift, LLC); two were from organizations or associations 
representing the wind energy industry (Airborne Wind Energy Consortium 
(AWEC) and Airborne Wind Energy Industry Association (AWEIA)); and, two 
were from associations representing the aviation industry (Experimental 
Aircraft Association (EAA) and National Agricultural Aviation 
Association (NAAA)). Of the 18 comments, 11 supported FAA's AWES policy 
and 7 opposed the policy. Of the seven comments that either wholly 
opposed AWES operations or supported change to enable safe AWES 
operations, four supported traditional marking and lighting per FAA 
Advisory Circular (AC) 70/7460-1, Obstruction Marking and Lighting,\6\ 
and two expressed support for part 77 notice and analysis. 
Additionally, 13 of the 20 comments received provided additional 
recommendations.
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    \6\ Available at https://www.faa.gov/regulations_policies.
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    FAA summarizes and addresses those comments responsive to the 
Notice.\7\
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    \7\ The FAA does not address comments that are not responsive to 
the request for information in the Notice.
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    1. Proposed system designs. While specific designs vary, based on 
comments received from industry, FAA finds general consistency in a 
three-part design with an aloft portion attached to a ground station 
via a mooring cable, tether, or similar device. Altaeros Energies' 
aloft portion is an inflatable shell filled with helium; EnerKite and 
SkySails' is similar to a textile kite; Highest Wind's concept 
resembles an autogyro; and Makani and Windlift plan for a wing made 
from lightweight rigid or flexible fabric wings, respectively.
    The material used for the tether or similar device varies across 
system designs, e.g., carbon fiber, interwoven copper cable, or 
polyethylene (Dyneema\TM\) fibers. These designs incorporate control of 
the aloft portion to maximize wind energy capture from either the 
ground station or from a segment of the aloft system, e.g., a module 
suspended below the canopy. The aloft portion of some proposed (called 
fly-gen) systems are generally static, generating electricity aloft and 
transferring it to the ground station, while other proposed (called 
ground-gen) systems use a winching system to generate electricity 
within the ground station. The size of the aloft portion varies within 
models from singular companies and across companies, with Highest 
Wind's test article a smaller size than their planned operational 
model. Additionally, some ground stations incorporate a mobile design 
to enable ease of transport and portable use.
    2. Airspace, operational, and safety considerations. Many industry 
comments provided conceptual discussions of their systems and indicated 
that the companies remain in the testing phase. Based on the nature of 
the aloft portion's need to move (while tethered to a fixed ground 
station) for electricity generation and the stated desired altitudes 
for harvesting wind energy, the systems have different desired 
operational airspace volumes.
    While comments focused on operational altitude, four commenters 
submitted diagrams that also considered the lateral airspace aspect, 
e.g., operations to 2,000 feet AGL at a 30-degree altitude requires a 
lateral distance of 3,500 feet. Some commenters integrated safety or 
buffer zones into their proposed airspace plan

[[Page 78851]]

to depict the area needed to mitigate the safety risk to other airspace 
users and persons and property on the ground.
    Altaeros completed testing below 200 feet AGL and all industry 
commenters expressed interest in either testing or sustained operations 
below 2,500 feet AGL. Five commenters expressed their desire to conduct 
uninterrupted testing during the day and at night over a period of days 
or months to replicate a realistic operational environment. As of 2011, 
SkySails tested aboard vessels at sea.
    EAA believed that the deployment of AWES systems above 500 feet AGL 
will have an adverse effect on recreational and general aviation flight 
safety operations. EAA and other commenters suggested conducting 
initial tests or data collection in established prohibited and/or 
restricted areas before allowing AWES access to the rest of the NAS. 
One non-AWES industry commenter remarked that creating more special use 
airspace is invasive to an already crowded NAS. Another commenter 
expressed concern about potential conflict between AWES and other 
aircraft and suggested AWES deployments at the same altitude as 
existing terrain.
    Companies planned to test and operate in either single 
configurations or in small (e.g., 3-5 units) or large (e.g., 300 units) 
farms on land or offshore. Highest Wind asserted that they can find 
willing private landowners underlying Class G airspace, where there is 
virtually zero air traffic below 3,000 feet AGL, to host testing. 
Additionally, Highest Wind requested that FAA ``designate a specific 
number of no-fly zones up to 2,000 feet AGL over private lands'' for 
testing and development purposes to reduce any burden of marking and 
lighting. NAAA stated that AWES deployments could render blocks of 
farmland untreatable by air, as aerial crop protection pilots would 
avoid the entire AWES ``cone of flight'' considering the shifting 
location and angle of an AWES due to wind variations. An aerial 
application (part 137) flying service commenter opposed AWES and 
believes they are a safety risk to agricultural and general aviation. 
The commenter stated that the amount of affected airspace would 
severely disrupt aviation.
    A pilot expressed safety concerns about the ability of an AWES' 
aloft portion to remain attached to the ground station in adverse 
weather and the length of time it takes to return the aloft portion to 
the surface. Industry commenters provided numerous proposed safety 
methods specific to their system design and its capabilities. Altaeros 
commented that they rely on established aerostat practices and that 
their device has a valve to quickly and safely lower the device during 
an emergency, e.g., tether failure. EnerKite stated that its system has 
weak links, a pyrotechnical cutter, and soft wings to minimize any 
safety risk. Highest Wind commented that their system's ``anti-
collision lights and on-board alarm'' comprise their safety 
considerations. Makani commented that their system is unique from other 
obstructions and its aloft portion can transition to a stationary hover 
and land within minutes in case of an emergency or, in case of a tether 
failure, land the aloft portion at a pre-determined point. SkySails 
commented that it intends to mark and light its system and, if the 
aloft system escapes its mooring, the aloft portion will sink to the 
ground. Additionally, SkySails' system has internal systems to monitor 
performance and recover the aloft portion as needed due to an emergency 
and suggested charting AWES to enhance safety. Windlift commented that 
their system can either quickly retrieve the aloft portion (reel in at 
10 meters per second) or fly the aloft portion toward the ground (30 
meters per second) to bring the aloft device below 500 feet AGL in less 
than 6 seconds.
    3. Marking and lighting compliance. Sixteen comments mentioned the 
risk to aviation safety and 13 comments mentioned either marking or 
lighting--the primary methods that enhance an obstacle's conspicuity 
for a pilot to see and avoid. Comments ranged from providing full 
support of FAA's marking and lighting schemes to suggestions of 
alternative means based on the inability to comply with traditional 
marking and lighting due to system design.
    EAA supported adequate marking and lighting controls for AWES equal 
to that required for other obstacles. NAAA expressed safety concerns 
with AWES, specifically the ability of pilots operating at low levels 
to see and avoid the tether. NAAA explained that a thin AWES tether may 
prove indistinguishable from the background depending on the time of 
day and weather conditions and recommended a strobe light on each 
individual structure and lighting on the tether. To NAAA, properly 
marked and visible obstructions are a life or death issue for low-level 
operators. An experienced general aviation pilot expressed AWES safety 
concerns based on low-level accidents involving MET towers and the 
difficulty pilots may have seeing an AWES during the day and at night. 
A part 137 commenter added that aircraft commonly operate safely at 
altitudes less than a proposed AWES operation and a pilot could mistake 
the aloft portion of an AWES as another aircraft disregarding the 
possibility of a tether and inviting disaster. This commenter also 
stated that the airfoil of AWES would need to be painted and lit and 
that the tether would need high-visibility strobes positioned at 
regular intervals to achieve a visual effect.
    AWEC proposed a high-intensity light on the airborne portion of the 
system, flashing at regular intervals at a fixed altitude or flashing 
at the top and bottom of the (circular) flight path. AWEC proposed to 
not mark or light the tether, claiming tether drag will prevent an AWES 
system from achieving desired levels of performance.
    Altaeros proposed lighting the structure using a high-intensity 
blinking light on top of the aloft portion, glow lighting or 
illumination of the aloft portion from the inside, or one or more 
spotlights aimed from the ground. Altaeros supported lighting the 
aerostat and not the tether.
    EnerKite's proposed system has brightly colored wings that can have 
red markings to increase conspicuity. EnerKite commented that decreased 
weight and movement of the system are substantial factors in system 
efficiency, thus rendering large obstacle marking infeasible. 
Additionally, EnerKite stated that flags generate considerable drag and 
complicate the dynamic extension and retraction of the system. EnerKite 
stated their system's movement at variable tether lengths also 
increases conspicuity and proposed the construction of a nearby 
obstacle with traditional marking and lighting for further enhancement. 
EnerKite indicated their ability to illuminate the wing from the ground 
or the nearby obstacle.
    Highest Wind commented that current marking requirements in AC 70/
7460-1 are overly burdensome and existing lighting requirements would 
make their system commercially and technically infeasible. Highest Wind 
asserted that AWES needs the development of new lights with half the 
weight, size, and energy requirements of those available when FAA 
published the Notice. Highest Wind also stated they planned to provide 
an anti-collision light on the flying vehicle to make it conspicuous to 
pilots in all weather conditions and expressed that marking the tether 
would be very difficult to achieve. From a testing perspective, Highest 
Wind desired to test in areas free of aviation then re-visit the 
marking and lighting requirement.
    Makani commented they intended to paint the wing white, in a manner 
similar to wind turbine blades, and

[[Page 78852]]

proposed an option of adding light-emitting diode (LED) lights to the 
wing tips similar to those used on light aircraft. Makani explained 
that tether marking encumbers the tether and endangers the system 
during launching and landing. Therefore, Makani proposed to not mark or 
light the tether and instead mark the wing and ground station. Makani 
commented their prototype, at the time FAA published in its Notice, 
could not comply with current part 77 lighting requirements due to the 
mass and drag of the lights. However, Makani anticipated the 
utilization of lighting onboard the aloft portion that flashes at the 
top and bottom of each loop, emulating the appearance of a stationary 
radio tower and making the obstacle conspicuous to pilots. In an AWES 
farm setting, Makani proposed to light the wings in the manner of a 
traditional wind farm, with lights on the wings at the perimeter of the 
farm and on wings that are high spots.
    SkySails said they could partly comply with marking and lighting 
requirements but did not provide any specific information. SkySails 
stated their system will be conspicuous to the flying public with the 
canopy made of yellow-colored fabric illuminated between sunset and 
sunrise at the center and wingtips by a spotlight situated on top of 
the control pod (suspended below the canopy). SkySails commented that 
if the illumination of the kites and registration in air traffic charts 
is not sufficient, wind farm arrays could be marked by tethered 
balloons placed on the outlines of the array. Balloons and mooring 
lines of the balloons will be marked and lighted according to existing 
requirements. SkySails did not comment on the policy, other than to 
provide specifics on their system.
    Windlift commented they are fully committed to working with FAA and 
NAS users to ensure aviation safety during the development of their 
systems but did not specifically comment on the policy. Windlift 
commented that their fabric wings can have bright colors embedded with 
reflective elements to maximize visibility. During night operations, 
Windlift's proposed system planned to use a conductive cable strung 
with the tether or a battery to power lights. Windlift commented that 
tether marking is a challenge to system performance due to increased 
drag and placing multiple flags within 75 feet of the aloft portion 
could provide a visual signal of the tether for pilots. Windlift 
proposed the use of LED lights instead of lights with more weight.

V. Additional Discussion

    A 2021 Department of Energy (DOE) report discusses U.S. locations 
where there is an increase in average wind speed with altitude up to 
approximately 300 meters (985 feet), above which the wind speed profile 
becomes mostly flat up to 500 meters (1640 feet).\8\ DOE finds that 
most AWES will operate below 500 meters. Aloft portions of an AWES, 
including the tether or similar device connecting it to a ground 
station, above 499 feet AGL would be in airspace available to general 
aviation and must be readily identifiable so a pilot can see and avoid 
it. As part of FAA's aeronautical study conducted under part 77 and the 
process defined in FAA Order JO 7400.2, FAA may include marking and 
lighting recommendations in its determination.
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    \8\ www.energy.gov/sites/default/files/2021-12/report-to-congress-challenges-opportunities-airborne-wind-energy-united-states.pdf.
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    Advisory Circular 70/7460-1 describes the FAA's standards for 
marking and lighting structures to promote aviation safety. Based on 
individual AWES characteristics, FAA may require marking and lighting 
applicable to specific systems to ensure visibility during varying 
weather conditions or night operations. FAA continues to research and 
test alternative marking and lighting for use by all components of an 
AWES (to include the aloft portion and the tether or similar device). 
Once the FAA identifies an acceptable standard, it may include it in AC 
70/7460-1. Additionally, FAA must evaluate each AWES and issue a 
technical note approving the system's marking and lighting prior to a 
proposed AWES deployment and part 77 analysis.
    As part of the part 77 evaluation, FAA will coordinate the proposal 
with potentially impacted air traffic control (ATC) facilities for 
local analysis, as required. If FAA determines the need for local 
coordination, each affected facility performs an operational safety 
analysis of the potential effects or risks of AWES operations to local 
air traffic. This analysis may also include AWES-specific 
considerations, e.g., the aloft portion separating from the ground 
station or the duration required to recover the aloft portion to the 
ground station. If the local ATC facility discovers additional safety 
hazards, FAA may convene a local Safety Risk Management (SRM) panel to 
complete a safety analysis and document its findings in an SRM 
document. The SRM panel's findings could affect FAA's final 
determination. Additionally, FAA-issued final determinations for AWES 
proposals may include conditions for marking and lighting to ensure the 
structure is visible to aircraft operating in proximity to an AWES.

VI. Final Policy

    Based on feedback received in response to the Notice, the FAA 
concludes that AWES may affect navigable airspace. As of the effective 
date of this policy statement, the FAA amends the policy set forth in 
the Notice and will consider part 77 applications for all AWES, 
including permanent and operational systems. Those entities proposing 
construction of an AWES that exceeds the parameters in section 77.9 
(e.g., an AWES constructed at more than 200 feet AGL at its site) must 
file advance notice with FAA.
    FAA receipt of part 77 notices of proposed construction from all 
AWES will enable the continued development of this emerging technology 
while allowing FAA to study the potential impacts of each individually 
proposed AWES on the safety and integrity of the NAS. Further, this 
action ensures inclusion of AWES information in the FAA's publicly 
searchable obstruction database.\9\
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    \9\ https://oeaaa.faa.gov/.

    Issued in Washington, DC, on December 20, 2022.
Michael R. Beckles,
Director (A), Policy, AJV-P.
[FR Doc. 2022-27993 Filed 12-22-22; 8:45 am]
BILLING CODE 4910-13-P