This is a big messy job (making a
good TACO), so anybody who can help with input is very welcome.
Excuse the rough detail and formatting, but note the gradual
progress in relating AWE to existing aviation standards-
Tethered-Aviation ConOps (TACO)
Case Focus on Experimental Airborne Wind Energy
(AWE)Provisional FAA Advisory Circular, and
Proposal-For-Action under ICAO Standards And Recommended
Preface to the
In 2010 the FAA and NASA called on the early
AWE industry to define its new "energy aircraft" types into the FAA's Category
& Class system, and develop a ConOps for AWE in US National Airspace (NAS).
In response, the Airborne Wind Energy Industry Association (AWEIA) undertook
this Tethered Aviation ConOps, to address all known requirements. "TACO" is an
open living document; AWEIA member, KiteLab Group, maintains it on a volunteer
basis. FAA and ICAO regulatory standards drive international practice, so this
content is specially intended for a FAA Advisory Circular and ICAO
Proposal-For-Action, to inform aviation stakeholders about AWE issues and
operations. TACO covers the full scope of TA, not just AWE, building on sound
existing models. This work is intended to merge into the NextGen Airspace
ConOps. Send corrections, additions, & comments to firstname.lastname@example.org
AOPA,-AirplaneOwners&PilotsAssociation; AMA-AmericanModelersAssociation: AWE-AirborneWind
ConOps-Concept of Operations; EAA-ExperimentalAircraft
Association; ETOPS-ExtendedOperations; FAA-USFederalAviationAdministration;
FARs-USFederalAviationRegulations; FBO-FixedBaseOperator, a small airport admin;
FEG-FlyingElectricalGenerator; FSDO- FlightStandardsDistrictOffice,
LSA-LightSportAviation/Aircraft; METAR-Meteorological Aviation data Reporting
format; NAS-NationalAirApace; NASA-NationalAeronautics&SpaceAgency; NextGen-
NextGeneration aviation standards; NOTAM-Notice(s)ToAirMen; PIC-PilotInCommand;
TA-TetheredAviation; TACO-TetheredAviation ConOps; UAS-UnmannedAviationSystem;
sUAS-smallUAS; UAV-UnmannedAerialVehicle; VO-Visual Observer
Tethering is a fundamental aeronautical engineering
method to transfer force over distance to and from wings, anchors, and payloads.
Tethered Aviation is a significant branch of aeronautics, with well-known
instances like kites, aerotowing, and aerostats (Moored Balloons). New
tethering concepts are expanding aviation capabilities; creating jobs,
industries, and novel recreations. TA is even poised to generate abundant clean
energy, as AWE, also known as "Kite Energy". This major new energy technology
has a potential to subsidize, by airspace usage fees and excise taxes, the needs
of populations and the dreams of aviation planners and general
aviation. Stakeholders such as pilots, developers, regulatory bodies, &
populations, are coming together to resolve lagging technical & social
challenges. Tethered or
not, acceptance-barriers persist to autonomous aviation in the US NAS (National
). The standing FAA requirement for direct human supervision of UAS systems will
hold for years yet. This early ConOps is thus "pilot-centric", embracing the
pilot as a key stakeholder, but also forward-looking to validated autonomous
flight (Appendix A).
The current aviation regulatory framework is mature,
not broke; daily protecting public saftey at reasonable cost. Pilots
are the primary workers in airspace most exposed to flight risk. Following
aviation norms and traditions, pilots are leading R&D of safe effective TA.
Pilot culture will ongoingly ensure safe operations in shared airspace. New
pilots will be needed to fill the many flying jobs created. The aerospace
industry must create systems that pilots accept and FAA inspectors (also pilots)
certify airworthy. Policy developers & decision makers, from national to
local levels, are another key stakeholder group. The well-informed
stakeholders must work honestly to convince extended stakeholders (populations)
that TA enhances society as a "good neighbor". TACO best-practice standards are
a basis for public acceptance.
The FAA relies on all aviation sectors, via user
associations and industries, to help define & promote best practice of
members. Failure of any sector to ensure safety brings down the full weight of
government enforcement. Safe aviation operations presided over by responsible
sector self-government allows the FAA to maximize its limited
resources and regulate with a light touch. Accordingly, the Airborne Wind Energy
Industry Association (AWEIA) has the formal mission of global leadership in
self-regulation of AWE and related TA. TACO is AWEIA's core effort to coordinate
Consencus Standards for safety and to acti as industry liason with regulators
like the FAA & ICAO. AWEIA will petition the FAA for new Rulemaking,
following the successful example of the Experimental Aircraft Association and
FAA together creating a regulatory framework for the new LSA category. Similarly
AWEIA will work within the ICAO framework to develop a core SARPs.
There are already urgent R&D safety issues AWEIA
is addressing, such as obligatory sharing of safety-critical failure modes &
mishap reporting. AWEIA is just one of several associations with overlapping
interest in TA. AOPA & EAA have strong interests within the new sectors.
Many practicioners will begin in TA from enthusiast communities: The American
Kiters Association (AKA) governs recreational & professional kite
operations. The American Modelers Association (AMA) is responsible for safe
hobbyist aviation. User associations in soaring & other sectors that
commonly perform tethered operations also have direct stakeholder roles. Wind
energy industry standards promoted by AWEA will also apply to AWE operations.
TA Applicable Standards,
Exceptions, and Exemptions
These sections present specific concensus standards for
regulating TA. Some of it is rough FAA "boiler-plate" in process of being
adapted to TA. An Applicable Standard is a operational
manufacturing/design/maintenance/quality standard, method, technique, or
practice approved by or acceptable to a civil aviation authority. An Exception
is a case in which a rule, general principle, etc., does not apply. There
are very few natural exceptions that apply to TA. An Exemption is approval to be
free from current regulations in 14 CFR. Minimal need for exemption of TA from
air regs is a goal of this ConOps
FARs Category, Class, & Type Certifications for
A first step is to newly define tethered wings (kites)
as aircraft. Currently only airplanes, rotorcraft, gliders, and balloons are
recognized Aircraft. A tether and associated motor-winch should be classed as an
Engine when it conveys motive or bulk power. Ratings and Operating Limitations
would be certificated just as reciprocating and rotary IC engines are. The
notion of an Airframe remains the same.
FARs can be vague, confused, & contradictory; the
classification scheme is a sort of patchwork. NextGen FARs are to overhaul
classification, but ontological quirks will surely persist. The system offers
wiggle-room, with exceptions, exemptions, and options possible at the discretion
of even low-level FAA field authorities.
The profusion of new TA design Types can be roughly
sorted according to the FAA's Aircraft/Airman/Operations Category, Class, &
Type System. Categories naturally grow by adding Classes. Special TA Classes are
proposed within current Categories. Just like any other aircraft,TA platforms
can be classified by gross-weight & airspeed, by the same physics of
"consequence". Weight & Speed (mass & velocity) are primary determinants
of Class within a Category. In general higher mass/velocity Classes have Higher
Consequence Failure-Modes & so require proportionally higher standards for
equivalent safety (mortality to flight hours). Stall Speed is a key safety
parameter, the lower the better, with the widest possible range of operation
between max airspeed & stall speed.
Selected Aircraft Categories- aircraft, rotorcraft,
normal, utility,acrobatic, commuter, transport, manned free balloon, glider,
special, restricted, etc. As an example of how TA Class can apply across
Categories, many given Types can be modified for aerotowing, with special
restrictions accruing. Single/Multi-Engine Classes- Many TA applications have
powered modes that naturally assign them to an Engine Class within a Category.
The trade-off of getting improved reliability from multi engines is a higher
standard of Pilot training & engineering design required.
As used with respect to the certification, ratings,
privileges, and limitations of airmen, Class means a classification of aircraft
within a category having similar operating characteristics. Examples include:
single engine; multiengine; land; water; gyroplane; helicopter; airship; and
free balloon; A major new class of Tethered Aviation is proposed. As used with
respect to the certification of aircraft, class means a broad grouping of
aircraft having similar characteristics of propulsion, flight, or landing.
Examples include: airplane; rotorcraft; glider; balloon; landplane; and
seaplane. A major new class of Tethered Aircraft or Kite is proposed.
Experimental and rare aircraft types are integrated by
ad-hoc classification across multiple categories & classes. Aviation is
increasingly diverse and major new branches may become wholly new Categories.
Tethered-Aerobatic, Tethered-Single-Engine (or turbine), Tethered-Multi-Engine
(or turbine), Tethered-Normal, Utility, Sport, Ultralight, Moored-Balloon,
Aero-Towed Glider, Tethered Rotorcraft.
Some Categories and Classes of aircraft
& operations are mixed, overlap, or are interrelated. For example, a UAS
(type) might be operated as a Commercial or Private Aircraft.
Small Aircraft- 12,500
pounds or less, maximum certificated takeoff weight.
A statement of compliance (SOC) is a signed statement
made by the aircraft manufacturer stating that the aircraft (specific by serial
number) was designed, manufactured, and is supported with a monitoring and
correction of safety-of-flight within a continued airworthiness
system, following Consensus Standards.
Tethered Aircraft (TAC) that operate
aerobatically & incur high G-loadings are Acrobatic Category (limited to
12,500lbs gross). Tether-Weight counts toward rated gross weight. Tether-Drag
counts against rated L/D. Autonomous Flight of high-consequence platforms (high
mass &/or velocity, especially around populations) require a proportionately
more cautious rigorous path to validation & certification.
AWECS are generally high-duty UAS &
so merit Utility designation. According to gross weight they can be sorted into
Ultralight, Sport, Normal, Commuter, & Transport Weight & Airspeed
Operational altitude is a major category
criteria. Some relevant ceilings- 400ft for low mass low speed hobbyist model
aviation. 500ft as a "floor" for general VFR aviation. Class G airspace, which
is low, but variable, with higher ceilings in remote areas, 2000ft obstruction
regulations for mast & tower certification, 18,000ft as an "absolute"
ceiling to avoid transport aviation operations. 25,000ft is the defined theshold
of High-Altitude flight, with special applicable standards.
Note: Many current tethered vehicle
platforms are not formally designated as "Aircraft" in Aircraft Categories under
current FARs, but the FAA reserves a right to designate them so. Tethered
aircraft must be formally designated as aircraft to be regulated for
airworthiness in the existing framework. Any conventional aircraft can in
principle be put on a tether, which does not negate its status as a
legal aircraft of a given mass & speed envelope, but adding a tether
adds operational complexity and hazard. Tethered aircraft may someday need to be
Type Certified in a suitable new Category or special Classes.
Pilot Categories & Training
Training and testing pilots is
fundamental to all aviation. All pilots in TA-shared airspace need awareness of
new operations & conditions. TA pilots must master basic aeronautical
training, plus specialized knowledge and operational proficiency. As
high-consequence risk emerges by more powerful industrial-scale systems, TA
Pilots must meet equivalent standards of certification to Transport Pilots.
Sec. 61.31 — Type
rating requirements, additional training, and authorization
Airspace- Obstuction Reg altitude
Multi-Tether Systems are comparable to
Multi-Engine Aircraft, with similar engineering trade-offs. The increase in
operational complexity, by added redundancy, can actually enhance safety.
A tether is a significant flying object,
an obstuctional hazard requiring great respect. Tether geometry and operational
methods are unique TA features to account for, but with useful similarity to
standard geometry flight trajectories & operations like cable rigging
Electrically Conductive Tethers require
special standards addressing unique safety issues. Formations of aircraft joined
by tethers into dense-arrays is an major operational configuration to validate.
A goal is that dense-array methods greatly enhance general aviation safety &
Aircraft Types operate in diverse roles
and regulations allow for this. Sample Operational Categories- Transport,
Normal, Utility, Acrobatic, Limited, Restricted, and Provisional. Provisional
uses are defined as needed- STOL, High Altitude, Marine Environment, Unmanned,
IFR, Weight & Speed Cats., Obstruction, & so on.
It is proposed by the FAA that
some AWECS might operate under Obstruction Regs such as govern Antenna Farms,
but this model is partial. For example, an antenna-farm Obstruction is also
regulated under mast & tower structural codes outside the purview of the
FAA. Towers lack many inherent hazards related to aircraft airworthiness & a
potential to crash far afield (runaway). An AWECS is not a tower & needs to
comply with Airworthiness Standards.
Current TA Norms & Regulations
The FAA's mandate to maintain a safe NAS covers TA activity but existing regs need upgrading to
cover holes in safety and allow enhanced capabilities.
Certificating airworthiness within current regs prevents TA R&D
from creating a "menace-to-aviation". Most AWE venture starts have no formal
aviation background & face acculturation along an FAA approved path. Class G
Airspace is the primary realm of current TA R & D.FSDOs are the current arbiters of allowable
experiments, with decentralized flexibility. AWE R & D can shop around for a
"best-fit" FSDO (generally remote low-traffic NAS regions). Special Airworthiness Certificate in the Experimental
Category is the certification currently available to civil operators of UAS.
NOTAM & COAs allow pioneering AWE R & D to
Obstruction regs, such as apply to antenna farms, can
partly serve for persistent "static" TA operations under 2000ft AGL.Shielded operations is an option for a TA operator
able to identify sites.
Draft FAA s UAS regs call for Pilot-in-Command & Visual
Observer crews. A misconception in the AWE field is that autonomous
operations will permissible in a short time-frame of a year or two, but the
safer bet is that many years must pass before the required safety &
reliability is validated & permitted.
Key Title 14 Parts of the Code of US Federal Regulations
(Aeronautics & Space)
PART 101 - MOORED BALLOONS, KITES, UNMANNED ROCKETS AND
UNMANNED FREE BALLOONS
Part 77 - OBJECTS
AFFECTING NAVIGABLE AIRSPACE
The FAA regulates
skydiving activity as"Parachute Operations" Part 105 (14 CFR 105). Flight
operations for skydiving are conducted under Part 91 "General Operating and
Flight Rules" (14 CFR 91).
FAA Advisory Circulars provide additional guidance about
operations. A TAConOps circular is a logical step.
Banner-Towing & Glider Aero-Towing regulations inform
equivalent operations in other applications.
Recreational NAS use covered by FAA Advisory Circular (AC)
91-57; generally limits operations to below 400 feet ASL well separated from
airports & air traffic. This is the appropriate place for virtually all
current AWE developers to conduct most experiments without being a "menace to
acceptable means of operating UASs in the NAS: 1) within “restricted” airspace:
or under a Special Airworthiness Certificate (2) Experimental Category or (3)
Certificate of Waiver or Authorization (COA). A COA authorizes an operator to use defined airspace under
specific provisions unique to the operation. It may require Visual Flight Rules
(VFR) & operation only &/or during daylight. COAs are issued for a
specified time period; one year typical. COAs require coordination with air traffic control &
may require a transponder in certain types of airspace.
Sense and Avoid Standard
current inability to autonomously follow ”sense and avoid” rules means a ground
observer (PIC &/or VO) must maintain visual contact operating in
unrestricted airspace. The VO must also maintain aural vigilence in a
quiet enough setting to detect airplane intrusion before visual spotting.
"Sense & avoid"
UASs requirement currently means PIC (Pilot-In-Command) & VO (Visual
Observer), plus dive or kite-kill capability.
of special IFR Rules clearances, especially higher operational ceiling during
graveyard shift to help bridge night-time inversion.
ETOPS Regulations for
Extended Operations is a basic condition for AWE, so a tailored set of FAA ETOPS regs is needed.
Avoidance System (TCAS) -
TCAS III utilizes interrogation of, and replies from,
airborne radar beacon transponders and provides traffic advisories and
resolution advisories in the vertical and horizontal planes to the pilot. TA
should use multiple transponders and develop trajectory reporting according to
the emerging NextGen standard.
TA Operations Notes
Tethered Aviation operations entail particular
hazards. A tether is a vulnerable and dangerous obstacle extending almost
invisibly over large distances. Navigation markers are an established
requirement & will long continue un use. Filing daily NOTAM are an essential
procedure in many airspace regions. PIREP are another messaging tool. with
Mayday as the most extreme instance.
Separation, Avoidance, Visibility, & Education
(SAVE) is a useful mnemonic for the basic principles of safe TA operations. S is
for passive Separation; the relegation of TA operations to remote low-traffic
airspace; A is for Avoidance; the effective evasive capability of a TA platform
(ie. "kite-killers"). V for Visibility is the standard for obstruction markings,
transponders, radar-reflectance, etc.. E for Education is the requirement to
appropriately inform & train all pilots operating in proximity to TA, as
well as the special Type-Rating knowledge a TA PIC needs.
Separation- Default minimums, flight planning,
Avoidance- Kite killers, PIC/VO, transponders,
Visibility- Signal lights and markings. A five-mile
visibility standard is proposed to supercede the current one mile balloon/kite
Education- General and specialized training of all
A major class of TA is arrays of crosslinked wings.
The 155lb UltraLight Vehicle Maximum is proposed as a Consencus Standard AWE
wing unit maximum for large arrays. Multi Line Requirement- The highest standard
of safety from Breakaway Mishap.
Concern- AWECS noise can mask the noise of intruding
air traffic (An airplane is often heard before seen, helping "sense &
Special TA Risks
Mid-Air Collisions- Tether trajectories and aerobatic
patterns of fast moving AWE kiteplanes can catch a VFR pilot unwares, otherwise
Mid-Airs are not a major hazard. Sense and Avoid is the Consencus Standard. UAS
must give way to all manned aircraft.
Breakaway, Tether Dragging
A Breakaway of a kite from its anchor generally
results in the kite gliding down to the surface in large circles. A kite
generally lands 4x its altitude away from its breakaway location.
Tether Dragging is a most dangerous condition where a
kite dragging its anchor or junk sustains flight for an indefinite distance.
This hazard should be known and planned for by population
Conductive-Tethers, Electrocution, Shorted Grids,
WildFire, Lightning. FAA discourages unpressurized Magnetos above 14000ft due to
Security concerns range from vandalism to terrorism
and are proportional to the inherent risk of an operation and the measures takem
to offset them.
Surge Loads- Strain limits, Safety Factor 8
UV degradation, Freeze damage, Mud Daubers in Pitots,
Bird Nesting in Airframe cavities,
Configuration, Maintenance, and Procedures (CMP)
Document. A document approved by the FAA that contains minimum configuration,
operating, and maintenance requirements, hardware life-limits, and Master
Minimum Equipment List (MMEL) constraints necessary for an airplane-engine
combination to meet ETOPS type design approval requirements.
FAA certification offices provide airworthiness
certification or related approval: Manufacturing Inspection District Office
(MIDO), Manufacturing Inspection Satellite Office (MISO), Flight Standards
District Office (FSDO), International Field Office (IFO), Certificate Management
Office (CMO), or CertificateManagement Unit (CMU).
Production Approval Holder.
A holder of a production certificate (PC), an approved production inspection
system (APIS), a parts manufacturer approval (PMA), or a technical standard
order (TSO) authorization who controls the design and quality of a product or
Prototype and Production
Conformity Inspection of Prototype Products and Related
Parts. An inspection to determine the applicant’s compliance to 14 CFR part 21,
Certification Procedures for Products and Parts, § 21.33(b) and any other
inspections necessary to determine that the prototype products and related parts
conform to the proposed design drawings and specifications.
Conformity Inspection of Production Products and Related
Parts. An inspection that may be necessary to determine that completed
production products and related parts conform to the approved type design and
are in a condition for safe operation.
Representative (DAR) - Maintenance. An individual appointed in accordance
with § 183.33 who holds a mechanic’s certificate with an airframe and powerplant
(A&P) rating under 14 CFR part 65, Certification: Airmen Other Than Flight
Crew-members, or a person who holds a repairman certificate and is employed at a
repair station certificated under 14 CFR part 145, Repair Stations, and who
meets the qualification requirements of this order.
Representative (DAR) - Manufacturing. An individual appointed in accordance
with § 183.33 who possesses aeronautical knowledge and experience, and meets the
qualification requirements of this order.
Simple preservation operations and replacement of small standard parts. These
constant routines are usually supervised or performed by the PIC.
Production Approval Holder.
A holder of a production certificate (PC), an approved production inspection
system (APIS), a parts manufacturer approval (PMA), or a technical standard
order (TSO) authorization who controls the design and quality of a product or
Representative (DER). An individual appointed in accordance with § 183.29
who holds an engineering degree or equivalent, possesses technical knowledge and
experience, and meets the qualification requirements of this order.
Conformity Inspection of
Prototype Products and Related Parts. An inspection to determine the
applicant’s compliance to 14 CFR part 21, Certification Procedures for Products
and Parts, § 21.33(b) and any other inspections necessary to determine that the
prototype products and related parts conform to the proposed design drawings and
Conformity Inspection of
Production Products and Related Parts. An inspection that may be necessary
to determine that completed production products and related parts conform to the
approved type design and are in a condition for safe operation.
TA Excise Taxes &
AWE taps airspace as a source of
vast energy. E nergy markets pay excise taxes; 5%
of a producer's selling price is typical. Unlike non-renewable energy sources,
which eventually run out, renewables can generate excise revenue in perpetuity.
B arriers to broad AWE
societal stakeholder acceptance, like NIMBY (not-in-my-back-yard) forces, will
melt before a rich new tax base that more than offsets any negatives.
average citizen who does not fly or own aircraft still shares a birthright to
the airspace commons. An equitable AWE Excise Tax can make a huge contribution
to basic social welfare & a new era of sustainable prosperity for
Airspace access is by
international legal tradition a Public Commons based on the doctrine of
Freedom-of-the-Seas. There is stiff resistance by existing aviation stakeholders
to privatization of NAS as some venture-capital AWE stakeholders propose.
Utility-scale AWE operations can contribute to shared airspace by paying Excise
Taxes on energy extracted & maybe even special Airspace User Fees.Airspace User Fees is a toxic to
existing aviation, but makes sense for the economic windfall promised by some of
the new types of aviation.
The AWE industry can thus earn
aviation stakeholder acceptance by subsidizing common airspace infrastructure
benefiting all. AWE tax revenue can offset existing FAA costs, relieving the
overall Federal budget, pay for NextGen infrastructure, guarantee liability
performance, & fund publicly-shared AWE R
& D. The early industry requires a
phase-in period for taxes, so as to not choke off early investment & to
promote initial growth. As significant mature AWE revenue-base develops, &
airspace becomes widely impacted, the tax base can be tapped. Small-scale
personal AWE operating at low altitudes should be exempted commercial
Like all aviation, TA operations must carry Liability
Insurance proportional to risk. Such insurance is currently unavailable from
traditional providers. An industry self-insurance pool may be needed to
jumpstart liability coverage. Secondary coverage, like Hull Insurance, can await
market solutions. A wrongful death these days
can cost some ten million USD. The insurability guaranteed by an excise endowed
fund can ensure that a financially weak AWE player in a freak-accident (even an
unknown failure-mode) event does not leave victims or families
Birds (and bats*) have
a primordial right to airspace, but can present a hazard to human aviation and
are themselves at risk by activities
like conventional wind power generation, night lit
towers, etc.. The problems are increasingly well known and mitigation is an
ongoing process. AWE can mostly build on existing bird management practices,
adding new protocols as needed.
Migratory species in
transit are most vulnerable to disturbances, but follow fairly predictable
seasonal patterns, helping risk mitigation. Conventional windfarms can cause
wholesale slaughter of flocks, so regulations are emerging to curb seasonal
risk. Sense-and-Avoid capability of AWE systems might serve to give clearance to migrating formations.
Sense-and-Warn might also work, but is an open study.
The presence of
endangered bird species or high bird populations raise the urgency of bird
issues. Nesting birds can be stressed by looming kites, acting out predator
response behaviors. In extreme cases birds will abandon active nests, but in
other cases birds adapt to kites and even seem to exploit some operations as
defensive cover. Generally year-around birds exposed to kite operations adapt
well, fully habituating, showing no stress response. Birds that first encounter
kites can react by fight-or-flight response. Hawk kites scare birds away and
might be a useful management tool, but birds are intelligent
and often learn to ignore an empty threat. Young birds can act quite different
to the same cues than their more experienced parents.
Flying birds are most
common near the surface and become rare with altitude, with few exceptions (like
migrating snow geese over high mountains). AWE at higher altitude therefore
seems potentially far more bird friendly that wind towers. An exception is the
tendency for birds to shun a looming flying object, while relaxing if
overflying, a predation response. Its probable that wind energy operations
change bird species distribution of their area. Towers are known
useful to raptors, and turbine killed birds can attract scavengers. AWE has the
potential to reduce such changes. AWECS and other aerial structure should be
minimally visible to birds even at night, by white markings. Black or dark red
markings by day usually give the farthest warning to air traffic for easy
Visibility reduces air
hazards. FAA nav markings intended to warn pilots of close proximity also serve
to clue birds. Turbines that make noise and have red painted tips to delineate
the disk area probably better warn birds. Fast-moving lines are a special
hazard, potentially acting as a saw. Painting alternate black (or red) and white
marking on moving line could help by making the motion visible. Fog has
disoriented migrating birds, which in some cases cue in on artificial lights
like radio mast warning lights. We should anticipate these rare events and find
solutions proactively. A proposed method is to radar detect airtraffic and only
then activate mast and tower warning signals. Another idea is to create clear
migration corridors, well chosen gaps in the wind farm
pattern, for birds to follow.
The design of an AWECS
can range from benign to deadly to birds. Where bird issues are most sensitive,
the slower, softer, more visible systems are favored. Although direct data is
scant, its probable that fast moving kiteplanes flying ae constitute the same
sort of hazard to birds as large conventional turbines. Many birds seem to have
a hard time detecting or understanding the threat of a large fast-moving object
on a highly curved trajectory, but do better avoiding an aircraft on a set
Birds easily see and
avoid large slow moving tethers and kites, with no known mortality factor. Birds
often do not see the fine lines on toy kites and collide with them, usually with
no bad effect, although a small potential for injury exists. Classic kiting is
bird friendly, with the exception of fighter kites with cutting line. Some South
Asian traditions even regulate the kite-fighting season based on bird presence.
Fallen line should always be collected to avoid snaring wildlife.
The risks are two-way.
A bird strike can bring down almost any airplane by varied damage. Engines can
be damaged enough to stop. Control surfaces, windscreens, pitot tubes, antennas,
radardomes, etc. can be made inoperable. A kiteplane is subject to bird-strike
risk, it can be blinded, brought down or breakaway, creating risk off-field.
Birds can create a nuisance to
ground equipment, nesting in cavities and fouling surfaces with droppings.
Bird study is a part of
AWE site assessment. Baseline bird presence should be determined before a kite
farm is established and bird presence tracked for ongoing impact detection and
mitigation. Qualified independent biologists should be relied on to develop
flexible management plans to meet high standards.
In conclusion, AWE and
birds can seemingly coexist well, but its up to designers and operators to make
sure adverse impacts are minimal.
*Bats are presumed to
resemble birds in their general relation to AWE, but with a more nocturnal
Turbines on resonant composite wings can be quite
noisy, sounding like an IC engine or high-speed machinery. Slower large scale
oscillating wings can create booming and infrasound noise pollution. The noise
can range from "washing machine" to "ocean wave". Noise issues with AWE can be
judged by extending the standards of AWEA.
TACO/Nextgen Transformation Path
process toward NextGen Integration-
The TACO Draft focuses
mostly on near-to-mid-term AWE R & D. The forward-looking capabilities
referenced below derive from the NGATS Vision Briefing of 2005 toward the
NextGen Airspace CONOPS for 2025. Mature Tethered Aviation Operations
(TAO) shall conform to these standards-
Supervisory Override of Semi-Automated Flight is a
Constrained Airspace is a capability needed for Tethered
EVFR rules for
relaxed visibility will widen the TA flight envelope & be a bridge to
Autonomous IFR .
Case Study- Small
Airports Accomodating AWE R&D
A common myth in popular AWE reportage is that
existing aviation norms and interests will impede progress. Its a reasonable
sounding theory, and restrictive standards do apply in congested airspace,
pending NextGen air traffic control, but such airspace is
only a tiny fraction of world airspace, even in aviation intensive regions. In
fact, existing small aviation operations will embrace TA adoption and help
perfect it. The latest sign is a growing list of small airports willing to host
AWE R&D, as a new aviation niche market. Due to corporate NDAs , which small airports are already developing
programs, but face-to-face meetings with airport administrators and their
stakeholders (aviators, aero clubs, skydivers, etc.) confirm an early consensus that AWE can coexist with general
aviation, that the operational issues are manageable . The
stakeholders are eager to validate new multi -use aviation.
A common profile is a struggling airfield with good
winds and low air traffic. Administrators informed about AWE aviation and the
specific means to integrate it safely into existing operations get excited at
the possibilities. A cautious step-by-step plan is appropriate. Usage fees and
partnership agreements are a revenue basis. There will be plenty of eager FBOs (Fixed Base Operators (of small
Many airports have large open fields in the spaces around
runways. As has been
noted, small airports with a second crosswind runway have an interesting
potential to host crosswind AWE generator vehicles on the idle runway. Two
orthogonal paved runways can do the job of adapting to wind direction almost as
well as a far more expensive paved field open in all directions. Conductive
contact strips can be embedded along the runway to tap energy for the
There is an invisble airfield traffic pattern to keep clear
of. In an emergency, the whole airspace needs to be clear. Shared airspace around an
airport depends on all aircraft
being able to "sense and avoid".
safety standards for AWE operations at an airport-
Tethers and membranes have special structural
characteristics and dependent operational methods.
Ground Anchors are a critical component of many TA
classes. Civil engineering and soil geology must interface with tethered flight
systems seamlessly, thus these fields become aviation related.
Load cases with time steps are used for various
analysises. Static stress analysis with linear material models/ Each load
case has a set of forces, moments and nodal deflections. For natural frequency
(modal) analysis each load case presents one mode shape and frequency. The first
load case is the first natural frequency, second case- second frequency, and so
on. In heat transfer, each load case is a time step in transient