Towards Collaborative Air
Traffic Management
Ludwig Kilchert, Lars
G.V. Lindberg,
Kim O'Neil
Abstract
This paper will discuss why an evolution of the
present Air Traffic System is needed and how Users can affect that evolution.
It will make proposals for the development of an Airborne Avionics Architecture
based on emerging CNS/ATM operational requirements and will evaluate the
operational, technical and certification aspects to be considered. It will
consider ADS-B and VDL Mode 4 in this context, as key enabling technologies
that will permit the necessary transition of the current ATC system towards a
more efficient Air Traffic Management System - based on the Trajectory Concept,
Collaborative ATM with minimal ATC intervention. The paper will also outline a
Cost Benefit Study and associated "Tiger Team" activities to identify benefits
for the near term introduction of Collaborative Air Traffic Management.
1. Introduction
To ensure that maximum benefit is obtained from
technologies such as VDL Mode 4 and applications such as ADS-B, they must be
fully integrated into the aircraft avionics architecture. The development of
appropriate Aircraft Architecture Concepts is, therefore, a necessary step
along the road towards this goal of a fully integrated airborne solution. The
implementation of these concepts is essential if Airlines are to be able to
operate aircraft that are "Free Flight Capable". Affordable aircraft solutions
must be made available to achieve the potential economic benefits of the
planned transition from traditional ATC practices to Air Traffic Management.
Such concepts must take account of the range and capabilities of existing
aircraft types, and the growing number of 'digital' aircraft - in order to
develop realistic transition strategies towards possible future architectures
based on these concepts. This must also be done for General Aviation and
military aircraft as well as for larger commercial aircraft.
2. Aircraft Architecture Working Group
In order to achieve these goals, the Swedish CAA
invited a Working Group of independent experts to develop the necessary
technical concepts. In future, this work will be carried out within the NEAN
Update Programme (NUP), sponsored by the European Commission. This group will
also undertake and establish a consultation process with Airlines and their
Associations, Aircraft and Avionics Manufacturers, ATM providers, Regulatory
Authorities and interested Research Agencies in the development of these
concepts. The Working Group consists of: Team Member Responsibility Background
Lars GV LindbergAV TECH Operational Aspects SAS Fleet Technical Pilot Technical
Pilot Standards DevelopmentTurbine Engineer. Ludwig KilchertGAS Engineering
Aspects Chief Flight Technical Engineer.Aircraft Systems Projects, ex
Lufthansa.Mechanical Engineer. Kim O'NeilAAT Ltd. Regulatory Aspects Regulatory
Expert, recently UK CAA.CNS/ATM and Related Technologies,Software and Systems
Engineer.
Figure 1: Aircraft Architecture Working Group
3. Aircraft Architecture Working Group Tasks
The core task undertaken by the group is an
analysis of the integration of VDL Mode 4 into large commercial aircraft and
General Aviation aircraft. The Working Group will propose architectural
solutions, for different aircraft types. These proposals will follow an
analysis of User Requirements and Operational Scenarios based on the future
CNS/ATM environment.
The identified tasks are to:
- Identify and propose baseline CNS/ATM
Concepts.
- Propose architectures for different
generations of aircraft.
- Describe potential alternative architectures
to support CNS/ATM concepts.
- Identify potential User benefits for each
specific architecture.
- Estimate the costs and likely implications
for the different options.
- Identify aircraft constraints, including
antenna, cabling and interfaces.
- Identify consequences for FMS, EFIS and
Warning Systems design.
- Identify required Standardisation work e.g.
AEEC.
- Co-ordinate proposals with Airlines,
Manufacturers and User organisations.
- Identify and discuss related issues for other
airspace users.
A key aspect of the work is industry
consultation - to ensure that the Working Group's proposals are acceptable to
the key industry players. The Working Group will seek the active co-operation
of others working in this and related areas. In particular, the work will
proceed with the active guidance of an industry Reference Group.
4. Operational Scenarios
The Working Group has reviewed proposals for
future Air Traffic Management Systems - analysing source material from a wide
range of organisations. This extends from the scenarios presented by ICAO, ECAC
and Eurocontrol in defining concepts such as the EATMS; to the Free Flight
concept and associated R&D programmes and projects including the FAA's
'Safeflight 2000' and the US Cargo Airlines Association ADS-B Programmes.
European research, including Eurocontrol's PETAL II and FREER 3 projects; and
EC funded projects such as NEAN, NEAP and NAAN are also included. Consideration
has also been given to the range of possible VDL Mode 4 applications within the
general CNS/ATM concept. It will be necessary to explore possible relationships
between VDL Mode 4 and other technologies such as ACAS/TCAS, GNSS etc. It
should also be noted that CNS/ATM concepts and the generic and digital nature
of data-links cuts across the traditional boundaries separating communication,
navigation and surveillance applications. It is reasonable to question whether
these boundaries remain valid.
5. The Present Air Traffic System
The present Air Traffic System appears limited
almost everywhere. This paper will argue that a fundamental evolution of the
existing Air Traffic System is required, if the aviation industry is not to be
severely constrained by the shortcomings of the present system. Extending the
current system (as with Mode S) will simply not do. These limitations are
apparent:
- In the airspace and runways, where the
problems are the separation standards and lack of transparency of ATC.
- On the tarmac, where the lack of taxi way
guidance is a severe limiting factor (increasing airspace capacity will only
transfer the bottleneck to the ground).
- In the effects of weather on ATC operations
and the way we cope (or rather don't cope) with adverse weather conditions.
- In the uncertainties over terrain and the
unacceptable rate of aircraft losses due to CFIT.
The problems associated with the present system
are well documented. The response to the saturation of the air traffic system,
to increasing delays and growing costs of ATC providers, has been to introduce
B-RNAV (benefits around 1999???), 8.33 kHz radio (benefits around 1999???) and
RVSM (benefits from 2000???). Despite the costs to airlines, the gains from
some of these can be measured in mere percentage points, although RVSM has the
potential to significantly increase capacity. Not one of these proposals will
significantly reduce ATC charges. In the meantime, Airlines operating in Europe
will continue their inexorable growth. This casts severe doubt as to whether
these measures will have any major effect on the capacity crisis. Perhaps the
most graphic illustration of the severity of the situation is captured in a
Eurocontrol diagram indicating the emerging ATM 'hotspots' in Europe:
Figure 2: European Air Traffic Hotspots
(Courtesy of Eurocontrol).
5.1 Costs of Present Air Traffic System
The present high cost and lack of global
availability of the Air Traffic System, places heavy commercial and operational
pressures on airlines. Typically, this has resulted in a system with high costs
and unacceptable (and growing) delays. These burdens are placed on airlines
almost irrespective of whether the ATS is:
- Non-existent, forcing airlines to adopt
unacceptable workarounds such as procedural separation using Air to Air voice
communications, visual means or TCAS/ACAS or
- Over-sophisticated, with far too much ATC
intervention, leading to frustrating operational restrictions and high costs.
Both these situations are unacceptable.
Undoubtedly, the best performance is obtained when a balanced level of ground
to air co-operation occurs, based on acceptable procedural separation
standards.
5.2 Handicaps of the Present System
The handicaps of the existing ATS are easily
enumerated:
- Aircraft position known only to ATC
- No common time base
- Actual intent is not known by any other
player
- Controller and pilot both control aircraft
trajectory
- ATS limiting parameters (e.g. separation,
runway RTA) other than altitude, are not controlled directly.
To this must be added the very limited
redundancy available in the current ground based system and the inefficiencies
caused by different methods of communication between Controller-to-Pilot and
Controller-to-Controller (further hampered by the limitations of the radio
spectrum and VHF voice). As such, there seems little future in the present
system.
6. What can be Done?
In essence, the answer to the question "What can
be done?" is an institutional question. Fundamentally, the solution is: A
Single Sky over a Single Market It is essential to note that this is not a
technological issue - tweaking the present system is not enough. Rather, the
Air Traffic system has to evolve to embrace new concepts of Air Traffic
Management. We will argue that a future ATM system must be based on the
Trajectory Concept and Collaborative ATM, and that ADS-B should be seen as a
key enabling technology. Indeed, it has already been observed that ADS-B is the
cornerstone of the future CNS/ATM Free Flight environment.
The future ATM system must move away from
self-limiting ground based radar concepts and capitalise on aircraft
capabilities. Eurocontrol has proposed its vision of a future EATMS as the
desire: "To allow all airspace users the maximum freedom of movement subject to
the needs for safety, cost-effectiveness, environmental aspects and National
security requirements." Eurocontrol has also made it clear that the development
of the EATMS depends upon a shift in the roles and responsibility between the
air and the ground, which can now be made as a result of improvements in
technology. These improvements will allow the ATM system to better understand
the trajectory of an aircraft (its intent). The future EATMS will lead to a
better sharing of tasks between the air and the ground and between human and
machine - enhancing the strengths of each. Eurocontrol's vision of the
distribution of airspace is also illuminating:
Figure 3: Proposed division of EATMS Airspace
(Courtesy of Eurocontrol)
In its ATM2000+ Strategy document, Eurocontrol
proposes the following targets and timescales for the transition of En-route
ATC: 2000 - 2005 Limited Separation Responsibility transfer 2005 - 2015
Extended Separation Responsibility transfer. These dates are key markers for
all ATM players in Europe and elsewhere, including Airlines, ATS providers,
Aircraft manufacturers and equipment suppliers. To achieve these targets, rapid
progress is required in the air and on the ground. More importantly, it is
essential to recognise that such a transfer of responsibility requires a
significant move away from traditional radar based separation techniques.
Specifically, it requires an independent Air-to-Air solution, i.e. ADS-B, based
on a technology with the capability of supporting a diverse range of
applications. The design and implementation must be able to support the highest
levels of certification.
7. ATS Philosophy
In order to move the debate forward, certain
principles are considered to be essential. In particular, it is necessary to
ensure that an appropriate level of information is distributed Air-to-Air and,
as required, Air-to-Ground and Ground-to-Ground. This information should
contain consistent and unambiguous data, which can be directly used for display
and/or applications in the air and on the ground without the need for further
interpretation or processing - to remove the "guesswork" that exists in the
current system. This will ensure reproducible solutions and remove doubt and
uncertainty from the Air Traffic System.
7.1 Controller/Pilot Roles and Communications
Communications between Pilots and Controllers
should be transparent. This alone will free valuable resources. In addition,
standard aircraft redundancy schemes should be introduced for ATS functions.
This will increase safety and maintain low separation standards. A key aspect
is the relationship between the Pilot and the Controller. This paper is not
proposing the transfer of ATC function to the cockpit. Rather, we are proposing
changes to the tasks being done. The ground should set and monitor separation
standards and impose those restrictions that are unavoidable.
However, only the pilot should control the
aircraft. The pilot should also have the capability to monitor traffic (only
partially and imperfectly achieved through TCAS/ACAS). This will provide the
required additional operational redundancy. It will also increase both safety
and capacity and will achieve the lowest possible separation standards. As the
volume of Managed Airspace (MAS) is reduced (see figure 3) and Free Flight
Airspace (FFAS) grows, it is clear that two distinct levels of functionality
emerge:
- Air-to Air communications in FFAS and
- Air-to-Air plus Air-to-Ground in MAS
Clearly, the distribution of FFAS and MAS will
be locally dependent on the traffic distribution and available infrastructure.
7.2 Air-to-Air Communications
The availability of a truly global Air-to-Air
communication function and the broadcast of aircraft position will provide
redundant traffic situation awareness for aircrew. With the further
availability of synchronised UTC, these two new elements will form the basis of
any new Air Traffic System - bringing benefits independent of ground
infrastructure. By adding to this the real-time intended trajectory of the
aircraft, the result is a complete "no guess" CDTI. These elements will further
simplify algorithms for traffic alerts with increased integrity. This will be
the basis for any meaningful aircraft based conflict management system. The
overall result will be radically improved aircraft displays (and associated
HMI) achieving the level of compatibility/redundancy required in a future
CNS/ATM system.
8. Technological Options
Detailed examination of the various technologies
can be found elsewhere. This brief section summarises the two main technologies
considered in the context of this paper.
8.1 VDL Mode 4
A review of the capabilities of the various
technological options currently available or under consideration in the near or
medium term, quickly leads to the conclusion that only VDL Mode 4 offers the
possibility of providing the necessary CNS/ATM functionality required to
achieve the goals of Free Flight. ADS-B implemented under VDL Mode 4 offers the
opportunity of rapidly achieving many of the potential benefits within the ICAO
CNS/ATM concept.
It is clear that VDL Mode 4 is able to:
- Provide the redundant data-link (without
compromise to TCAS/ACAS).
- Provide 200+ NM Air-to-Air range
- Provide the necessary data-link capacity
- Provide low power consumption, Standby
operation.
Substantial technical material already exists to
support these propositions and they are further supported by projects which
have demonstrated the capability of VDL Mode 4 including the North European
ADS-B Networks (NEAN), the Faraway Project (Fusion of Radar and ADS-B Data),
NEAP (North European ADS-B Applications) et al. Further co-ordination occurs
with other projects including PHARE, Freer, Petal II, NAAN, JANE etc.
8.2 Mode S
Traditional ATC based approaches have centred on
Mode S. Mode S related proposals require the extensive down-link of aircraft
parameters. Typically, these include:
- Flight Call-sign
- Altitude in 25' intervals
- Magnetic heading
- Speed, IAS, TAS, GS
- Roll angle
- Vertical speed
- Track angle
In addition, expanded Mode S "services" might
also require down-linking of:
- Selected flight level
- Selected magnetic heading
- Selected course
- Selected IAS/Mach number.
The Mode S option would clearly "cement existing
ATC practices" which are acknowledged to be at their limits. Mode S options are
derived from ground based ATC concepts which assume a continuing and increased
tactical interventionist role by ATC. These obsolete notions are incompatible
with emerging CNS/ATM concepts such as Free Flight. Despite the considerable
cost of obtaining and down-linking these Mode S parameters from aircraft,
little advantage would be gained in Air Traffic Management or to aircraft
operation. Aircraft intent (i.e. its trajectory), for example, would still be
unknown. As a result of the costs, world-wide implementation is implausible.
Thus, true global interoperability would not be
achieved. Rather, Mode S represents an extension of current ATC practices for
some, with high aircraft and infrastructure costs and minimal benefits for the
majority of civil aviation (for many aircraft, these costs would be very high
indeed).
Accordingly, there is considerable unease within
the airline community about the high and disproportionate cost of Mode S.
Implementation of ADS-B in Mode S extended squitter is not considered a
practical option and would severely compromise the TCAS/ACAS function. Even the
most optimistic projections for Mode S do not give it the range or the capacity
required for ADS-B. Perhaps most damaging is the fact that proponents of Mode S
seem unwilling or unable to accept, trust or use the capabilities of modern
aircraft. This is ironical, considering the high cost and effort put into the
design, development and certification of aircraft systems and the obsolescent
and uncertified nature of ground systems! Mode S proponents also apparently see
no application for ADS-B as a replacement for current surveillance techniques
"for the foreseeable future" - a somewhat out of step perspective.
These issues should come as no surprise, given
the very long gestation period for Mode S and its origins in ground based ATC.
It is certain that Mode S was never conceived with concepts such as Free Flight
in mind, or intended to provide such far reaching capabilities.
9. Overview of VDL Mode 4 Related Projects
The following is a (very) brief overview of VDL
Mode 4 Projects evaluating this technology in a wide variety of applications
and scenarios. There have been many considerable achievements made in these
projects that deserve wider dissemination. Some of these achievements have
far-reaching implications for the development of future Air Traffic Management
Systems - and concepts such as Free Flight. Many of the results have very near
term application. The reader is advised to contact the relevant projects.
9.1 The North European ADS-B Network (NEAN)
The NEAN project aims to demonstrate the
benefits of ADS-B, validate the technology and establish a cost base. The
cellular VDL Mode 4 network extends over Denmark, Sweden, Germany and beyond,
giving extensive North European coverage (see map) of an integrated cellular
ADS-B network. The project partners include the Civil Aviation Administrations
of Sweden, Denmark, Germany & UK, with the active participation of
Lufthansa, SAS and other airlines. Potential applications of the high capacity,
two-way data-link communications (air/air, air/ground ground/ground) include
Situation Awareness, Free Flight, Fleet Management, Surveillance, GNSS
Augmentation and ground movement monitoring etc. A NEAN work package examined
issues related to the certification of the ADS-B infrastructure.
The cellular structure of NEAN permits easy
extensibility. The potential of this project and the achievements already made,
have been recognised by the European Commission, which has elevated the status
of the NEAN to that of a Strategic International Project. NEAN is part funded
by the European Commission under its Trans European Networks (TENs) programme.
NEAN is likely to experience rapid expansion in the very near future.
9.2 NEAP - North European ADS-B Applications
Project
NEAP is an EU funded applications project which
will use the NEAN infrastructure to test, develop and evaluate user
applications based on ADS-B and the VDL Mode 4 data-link in the following
areas: · Enhanced ATC Surveillance · Pilot Situation Awareness
· GNSS Precision Navigation in all phases of flight. · Up-linking
of Traffic Data and ATIS. The project partners include the civil
administrations of Denmark, Germany and Sweden, and airlines including SAS and
Lufthansa.
9.3 NAAN - North Atlantic ADS-B Network
This project will establish a cellular ADS-B
infrastucture across the North Atlantic, based on VDL Mode 4. Project partners
are from Denmark, Ireland, Norway, UK, Faroe, Iceland and Greenland. This
network will then be connected to NEAN to create continuous ADS-B coverage
extending from Europe across to the Western Atlantic. The North Atlantic
network will be used to evaluate Free Flight concepts and applications.
9.4 FARAWAY Project: Fusion of Radar & ADS
Data
The FARAWAY project aims to investigate the
potential gains in operational performance of ground surveillance systems, and
aircraft navigation, over continental areas which are possible through the
fusion of ground generated surveillance data (radar data) and aircraft derived
position information (ADS). The project covers Italian airspace and will
connect with the NEAN network in FARAWAY II. NEAN and FARAWAY will also
co-operate with Eurocontrol's PETAL 2 project, investigating Controller Pilot
Data-Link Communications (CPDLC). The project partners include:- Alenia
Sistemi, ENAV, AAVTAG, Alitalia, ItalATC, DASA, and National Avionics.
9.5 FARAWAY II Project
An extension of Faraway I, this project will
extend the ground infra-structure to give complete ADS-B coverage in Italian
airspace. ADS-B coverage will then be used to augment radar coverage. The
project partners include:- Alenia Sistemi, ENAV, AAVTAG, Alitalia, ItalATC,
DASA and National Avionics. This local cellular network in Italy will then be
connected to NEAN to extend the European infrastructure as part of the EC's
Trans European Network programme.
9.6 Petal II
This project is investigating Controller Pilot
Data-link Communications (CPDLC) and its application to Air Traffic Management.
The project is utilising the VDL Mode 4 infrastructure of the NEAN project.
Latest achievements include the clearing of a Lufthansa 747 through Maastricht
Upper Airspace entirely via data-link. The project also involves the
development of controller workstations to support CPDLC operations.
9.7 FREER
FREER is a Eurocontrol project investigating the
transfer of some ATC functions to the cockpit and the potential of trajectory
negotiation to increase airspace capacity. Some of the results of this work
have been particularly encouraging and illustrate the potential benefits to be
gained by fully exploiting aircraft capabilities.
10. Air-to Air (Global) Function
In order to develop this function, it will be
necessary to develop a common format for the transfer of changes to the
intended trajectory. Position reports are transmitted as:
Present Lat/Log,
Altitude, Time, Attribute
In future, position/intent reports should be
considered as being equivalent to confirmation of the active FMC Flight Plan,
as defined in the Eurocae P-RNAV requirements. Waypoints should be located in
the Flight Plan to allow linear interpolation between consecutive
waypoints:
- Present Lat/Long, Altitude, Time,
Attribute
- Next Lat/Long, Altitude, Time,Attribute
- ------------
- Lat/Long, Altitude, Time, Attribute
- Next + N Lat/Long, Altitude, Time,
Attribute
10.1 Display Capabilities
Additional display capabilities should include:
· Own position plus own reported position · Traffic information
up to at least 200 NM · Separation standard, out of the Navigation
Database, selected or uplinked · Pilot selected conflict alert level
· Traffic conflicting with active FLPN, resolution proposal, call sign
and frequency The Display should also be capable of identifying any conflicting
intent report, terrain information or weather information and compare it with
its own modified Flight plan and resolution proposal. It should also be able to
display any selected intent report and the call sign of any selected target.
Additional computing functions should include:
- Flight plan building, prediction and guidance
(to meet the Eurocae P-RNAV requirements)
- Trajectory conflict search and alert, based
on separation standard and alert level.
- Immediate availability of intended
trajectory, in case of evasive manoeuvre
- Active separation control (on own and merging
trajectory). The necessary hardware changes include:
- Provision of sufficient display and computing
capability
- Active cursor control in NAV display
- Frequency control for VDL
- Suitable interfaces to VDL, with sufficient
data flow rates and capacity
- Provisions for at least two dedicated VDL
Mode 4 transceivers.
11. Air-to-Ground Functions
In order to provide Air-to-Ground functions, it
is only necessary to adapt existing ground functions to interface with ADS-B.
Improved controller workstations will be required with the necessary HMI - in
order to achieve compatibility and redundancy between the Air-to-Ground and
Ground-to-Ground. Ideally, the Air-to-Ground data-link should be compatible
with the Air-to-Air data-link. These improvements have already been
successfully demonstrated in numerous EC funded projects supported by European
Civil Aviation Administrations, including those of Denmark, Germany, Sweden,
Italy and in work carried out under the aegis of Eurocontrol. Improved
controller workstations have also been developed and demonstrated by
Eurocontrol.
12. High Level Design
12.1 Option 1 - Integrated VDL Mode 4
Transceiver
The high level design for integrated VDL Mode 4
is outlined in the following diagrams. Option 1 illustrates the architecture
for a fully integrated VDL mode 4 installation, as depicted in figure 7. Note
that this is a fully redundant dual installation. Inter-connection between the
two buses provides additional protection.
Figure 6: Option 1 - VDL Mode 4 Integrated
into Aircraft Architecture
Redundancy in the Avionics Architecture is
similarly reflected in the redundant installation of the VDL Mode 4 radio
transmitters and receivers as indicated in figure 7.
Figure 7: Option 1 - VDL Mode 4 Transceiver
Redundancy
12.2 Option 2: MMR Integrated VDL Mode 4
Transceiver
A second and alternative option involves the
integration of VDL Mode 4 within the Multi-Mode Receiver (MMR). This involves a
simpler internal architecture appropriate for those aircraft equipped with the
MMR. Figure 8: Option 2 - MMR Integrated VDL Mode 4 Transceiver. The dual MMR
configuration is provided with a similar arrangement of VDL Mode 4 Transceiver
redundancy.
12.3 Redundancy and Failure Modes
An analysis of the failure modes shows that this
design is highly robust in the event of equipment failure, providing high
levels of redundancy, reliability and availability. An account of the failure
modes and the protection provided will be made available.
12.4 Aircraft Changes to Support Air-to-Air
Communications
The hardware changes to support the various VDL
installation options, require a New 'Standalone' VDL Mode 4 box to be installed
in lieu of existing data radio and VOR receivers. Added to this must be made
provision for the Multi-Mode Receiver. These changes will permit transmission
of broadcast ADS reports and delivery of:
- Report Requests - equivalent to the
non-active or modified FMC flight Plan, in the same format as the
Position/Intent report.
- Clearance Uplinks - in the same format, with
different attributes as in Position/Intent report (e.g. Restrictions only -
Free Flight!)
12.5 Aircraft Changes to Support Air-to-Ground
These changes also permit Air-to-Ground
communications. With this come a number of advantages and disadvantages. It is
clear that Channel loading in Managed Airspace (MAS) will be an issue (whatever
the underlying technology), as will the lack of a communication acknowledgement
(resolved with point to point communications). However, it is also clear that a
redundant link is available and that Receive/Transmit channels should be
permanently monitored. Necessarily, Closed Loop communications will be required
in any case. This is outlined in Figure 8 below.
Figure 9: Closed Loop Communications
Implementing the Air-to-Ground communications
link makes it possible to up-link data, which will lead to direct benefits in
flight management. These include:
· Position reports from non-reporting
targets (Traffic Information Service-Broadcast) · QNH, RVR, Surface
wind, RWY condition · Centre frequency and call-sign · DGNSS etc.
These services have already been demonstrated in various European projects
(NEAN, NEAP, FARAWAY etc.). Necessarily, this will require additional display
capabilities in the aircraft for actual QNH, RVR, Surface wind, runway
condition and crew alerts. Other display capabilities include actual airport,
severe weather, actual centre frequency and call-sign. Additional computing
functions will include auto-tuning and selection of VDR and audio system - in
order to keep the voice channel always on 'standby' without manual setting and
checking. No further hardware changes will be required to enable these
facilities.
13. Certification
In order to gain the greatest possible benefit
in the implementation and integration of VDL Mode 4 into the aircraft avionics
architecture, it will be necessary to certify to the highest level. This
stringent requirement is a necessity to ensure: - Safety - Maximum operational
benefits - Future proofing - Early benefits - Industry confidence
13.1 Certification of Ground Installations
Similar considerations are required for the
certification of the ground system, due to the possibility for close coupling
in certain operational scenarios. That is, unsurprisingly: - Safety! - Maximum
operational benefits! - Future proofing! - Early benefits! - Industry
confidence! There seems little realistic appreciation with the ATM community
for the need for certification and little understanding that systems cannot
simply be "bolted on" to aircraft. A fundamental re-think is required by ground
authorities regarding the certification of ground systems.
However, some work is already underway to assess
the potential safety significance for integrated VDL mode 4 applications. For
example, work is being carried out in a number of projects including the North
European ADS-B Applications Project (NEAP). The work involves assessing a
number of operational scenarios including: - Situation Awareness - GNSS
Augmentation - Separation Assurance - Precision Approach (CAT I). Following the
assessment of these operational scenarios, the applications will be analysed to
assess: -
- Safety Criticality
- Mission criticality
- Other aspects
Assessments are required to identify essential
certification requirements such as Integrity, reliability, availability etc.
These key parameters are identified for some applications in, for example, ICAO
All Weather Operations Panel (AWOP) reports. What rapidly emerges from an
analysis of the potential applications, is that a "No Hazard" certification
process is untenable. Previous experience has shown that such (essentially)
uncertified equipment is limited in its operational value. Indeed, considerable
confusion exists over the certification status of many airborne equipments,
which have only been given installation approval and not certified in terms of
performance or functionality. Indeed, the difficulty in certifying many CNS/ATM
applications has been identified elsewhere e.g. RTCA , leading to an effort to
streamline the CNS/ATM certification process.
13.2 The Certification Process
It is also clear, that an early start is
required in the certification process to ensure that certified equipment is
available for operational use at the earliest possible opportunity. The lead
times for certification are very long and critically depend, not only on the
availability of Standards and certification procedures but also on active
co-operation between Aircraft manufacturers, equipment suppliers, airlines and
Aviation Authority Administrations. Such co-operation is well established in
the US, with the RTCA, FAA and AEEC - to the benefit of American industry, but
is less well established in Europe.
Figure 10: Overview of Needed Requirements,
Standards and Legal Instruments.
Figure 10 above indicates the complexity of the
certification process (from a European perspective) yet is only an overview.
Even so, the support of the Airlines and the Aircraft manufacturers is clearly
an essential element in making the certification of advanced CNS/ATM
functionality possible. Active Airline pressure on Flight Safety authorities
will be necessary to ensure that standards and certification processes are put
in place and that work is undertaken at the earliest date to ensure early
implementation with corresponding benefits to Airline operations. Unless this
occurs, there will be substantial delays in the movement towards concepts such
as Free Flight (whatever technological option is chosen).
It is also important to recognise that simply
waiting for technology to emerge (usually from the US) is not an effective
strategy for achieving early benefits from CNS/ATM concepts such as Free
Flight. Whilst there are few shortcuts, many of the required certification
activities could, with Airline support and co-ordination, be carried out in
parallel - so shortening the lead times to early benefits. Active co-operation
between Airline players in Europe, the US, Asia and Africa could significantly
hasten the introduction of major operational ATM benefits.
14. Implementation Strategy
In order to move rapidly towards a CNS/ATM Free
Flight scenario, it is necessary to develop strategies to address key areas for
a successful implementation. Necessarily, this can be complex in detail, but
some simple conclusions are possible. For example, the strategy underlying this
paper is based on an approach for gaining:
- The support and commitment of key Airline
players - The co-operation of Pilot Associations and Airline Organisations -
The co-operation of the aircraft manufacturers - The co-operation of the
avionics manufacturers - Improved understanding of ATM providers of Aircraft
capabilities.
The objective being to gain airline support, by
emphasising the airline perspective and outlining a 'way ahead' that does not
rely on the decisions of the ATM providers. In particular, by
a) Asking the question: "How can Free Flight be
achieved: - unless airlines buy aircraft capable of Free Flight?" b)
Emphasising that the solution also lies with the airlines: - not just the ATM
providers!
c) Air/Air communications require a technology
with specific supporting characteristics.
d) Air/Ground data-link communications require
an appropriate ground infrastructure, preferably compatible with the Air/Air
data-link.
14.1 The Aircraft Market Strategy
Similarly, the implementation strategy is based
on the need to take account of the range of existing aircraft types, and the
growing number of 'digital' aircraft - in order to develop realistic transition
strategies towards possible future architectures based on the concepts outlined
in this paper. This must include General Aviation (GA) aircraft and military
aircraft, as well as larger commercial aircraft. The strategy is therefore
based on the division of the aircraft market into four sectors:
- a) The Immediate Procurement Market That is,
aircraft which are subject to imminent procurement.
- b) Future Aircraft Aircraft to be procured in
the next 5+ years.
- c) The Retrofit Market Existing aircraft with
a significant operational life.
- d) The General Aviation Market
A diverse market, for which further subdivision
may be necessary. The object of the strategy is to identify and target those
aircraft for which the proposed Architecture will create maximum benefit at
minimum cost and which gives the greatest possible 'leverage'. This can be
achieved by targeting future aircraft procurements, aiming to ensure that
aircraft are delivered 'Free Flight capable' - as this is the lowest cost
solution and will result in 60 - 80 aircraft a month entering operational
service. This will have a significant effect on the retrofit market.
In essence, apart from providing guidance on
preferred architectures, this could result in a self-fuelling process. Airlines
will upgrade because their aircraft lack the essential functionality required
to operate effectively in Free Flight airspace - which in turn limits their
commercial value and revenue potential. The cost of delivering a VDL Mode 4
ready aircraft is small in comparison with the cost of the aircraft, yet
provides essential functionality required for the future ATM and/or Free Flight
environments.
However, justifying retrofitting an aircraft is
always more difficult because the cost of retrofitting must come from revenue
budgets and because the cost of retrofitting is higher. The retrofit system
development has to be undertaken by the airlines. Retrofit aircraft may be less
likely to recover the cost of 'full implementation' and therefore may only make
use of partial solutions.
Consequently, the cost benefit justifications
are different because different formulae and logic are being applied.
Retrofitting is always a compromise. The key argument here is that new aircraft
must be "Free Flight" capable or the investment being made in the aircraft is
at risk. Indeed, it is essential that aircraft are as "future proofed" as is
possible. Older aircraft may have a more limited commercial life and
consequently have less potential to capitalise on the opportunities presented
by a future CNS/ATM environment.
14.2 Air-to-Air Implementation: Airlines
The decision to proceed with an integrated
Air-to-Air solution will be airline controlled, due to the envisaged benefits.
These benefits depend upon the:
- Introduction of Free Flight Airspace (FFAS)
- Increased Capacity, Flexibility and Safety in
FFAS
- Early introduction of reduced Separation
Standards below existing Radar based Separation Standards
- Functionality that is available world-wide -
when equipped aircraft share airspace or when Traffic Information Service -
Broadcast (TIS-B) is available.
14.3 Air-to-Air Implementation: Aircraft
Manufacturers
The Production Development lead needs to be
taken by the Aircraft manufacturers (OEMs), due to the need for:
- H/W, S/W, cockpit and Procedure Integration.
- Single solution across OEM's Fleet
- Aircraft installation and certification
- Fast ADS-B introduction (potentially over 800
aircraft per year).
14.4 Air-to-Ground Implementation: ATC/Airport
Agencies
The implementation decision for the ground
infrastructure must be taken by the ATC/Airport Agencies due to the need for:
- Cost reduction to stay competitive
- Providing airspace capacity ahead of traffic
demand
- Infrastructure, H/W, S/W, Controller Station
and Procedure integration
- Hardware installation
Many Airport authorities recognise that
improvements in Airspace capacity will only increase the pressures at airports.
Unfortunately, many airports are presently outside the CNS/ATM debate, tending
to rely on ATS providers to fulfil this role. Bringing the benefits of emerging
CNS/ATM technologies to airports will be a key element in enabling improvements
in capacity, safety and efficiency in ATM.
15. Recommendations
This paper and a detailed presentation were
given to a series of meetings in order to obtain appropriate feedback and
obtain further input towards the task of refining an avionics architecture able
to support Free Flight concepts. At a meeting held in Stockholm of Airlines,
National Authorities and other bodies, the following basic principles and
recommendations were agreed:
- ADS-B will be the cornerstone of the future
CNS-ATM environment
- ADS-B needs to be fully integrated in the
airborne architecture to achieve the goals of EATMS, ATM 2000+ and other plans.
- The most efficient way of achieving a timely
implementation of ADS-B is by providing an architecture in the immediate
Procurement market.
- The effort of achieving a viable airborne
architecture must be User driven.
- The work provided by the Aircraft
Architectures Working Group should be used as a platform for the ADS-B
architecture. Input taken from this meeting and the established Project
Reference Group
- The work provided by the Aircraft
Architectures Working Group shall be used as a platform for a user driven ADS-B
architecture.
- The input from this meeting and the
established Project Reference Group shall be used to develop the proposal to be
presented to Airbus and Boeing in preparation for an All Operator Conference on
ADS-B and Airborne Architectures.
16. Airborne Architecture Project Reference
Group
As indicated above, a Reference Group was
established to provide further User input to the work of the Working Group.
This input was seen as essential to enabling the further progress of the
Aircraft Architecture proposals. The Working Group is grateful for the positive
support given.
16.1 Terms of Reference
The Terms of Reference of the Reference Group
are (very briefly):
- To review the Airborne Architecture Working
Group proposals
- To provide User input to these proposals.
- To seek consensus within the group during the
development process.
Membership of the Reference Group includes:
Lufthansa, SAS, United Airlines, Cargo Alliance Airlines (e.g. UPS,
FedEx…), DFS, Swedish CAA, Eurocontrol, Russian FAA (GosnIIAS) and
FAA.
17. Future Work
The concepts of Collaborative ATM and Free
Flight based on ADS-B have reached such level of maturity, that the path from
Research and Development to operational implementation must now to be mapped.
Future work to be addressed include:
- Benefits for the early users,
- Transition steps,
- ATM environments with mixed equipage, as well
as the
- Overall Cost / Benefits
In the de-regulated airline environment, with
fierce competition, it is crucial for the airlines to make the correct
investment. Such investments must provide returns within an acceptable time
period - which for most airlines is a maximum of 3 years. From recent
experiences in the implementation of BRNAV, RVSM and 8,33 kHz frequency split,
many conclusions can be drawn. One simple lesson is that the importance of
Cost/Benefit studies cannot be underestimated.
However, in a situation with spiraling delays
and possible effects on overall safety, one not only has to take account of the
short term Cost/Benefit ratio - but also long-term effects. Therefore, in a
conclusive C/B study it is of very high importance to establish consensus
between Users, Service Providers and OEM's of the need for a paradigm shift.
17.1 Airline Requirements
- The airlines have four essential requirements
for a new ATM System:
- 1. Safety is improved in absolute terms.
- 2. The system can sustain the forecasted
growth.
- 3. The cost of operating in the system is
reduced, including both the:
- - Direct operational cost and the
- - Cost for infrastructure on the ground
and in the aircraft.
4. Implementation on a global basis
over an acceptable time frame.
With traffic currently increasing at 5%+ on a
yearly basis, the numbers of accidents and incidents will, at least, have to be
held to the current levels to maintain the confidence of the travelling public
and airline industry employees - according to IATA. This implies a massive
reduction in the accident and incident rates.
Even with a modest annual growth of 5 %, the
total European air traffic volume will have doubled by 2012. Some Analysts
claim that the ATC system - which is struggling to handle today's traffic in a
satisfactory way - will be incapable of handling tomorrow's traffic levels.
"Tweaking" the current system will increase capacity, but not even Reduced
Vertical Separation (RVSM), Basic RNAV, Precision RNAV etc. combined can
sustain the forecasted growth. The FAA is now predicting aviation grid lock in
the USA by year 2005.
The yearly cost of ATC induced delays for
European airlines, was estimated in 1994 to be between one and two billion ECU,
according to ECAC/McKinsey. This is now considered to be a significant
underestimate of the true cost. While the airlines have been able to reduce the
fuel costs by investing in more efficient aircraft and engines, the cost for
the ATC service has steadily increased - on average 7,2% over the last ten
years. This has occurred despite the fact that the airlines have invested
heavily in new avionics. For a major airline like Lufthansa, the direct ATC
charges are now 5% of the operational cost. As a comparison, the cost for fuel
is 10% of the operational cost.
17.2 Cost/Benefits
The Airlines also require that the new ATM
System enable reductions in direct operational costs. This can be accomplished
by allowing the full use of: actual performance capability of the aircraft,
routing, speed, altitude etc. To achieve the first and third objective i.e.
safety and cost reduction, the system has to be implemented globally within an
acceptable time frame. Regionally implemented systems will not only increase
the cost of installation of equipment but also increase operational hazards.
Introducing Free Flight, with an optimum use of
the airspace and aircraft performance, will reduce both fuel burn and time
airborne and thus reduce both the operational cost and the environmental
effects of air transport. However, the economical gains for the airlines and
the traveling public in solving the spiraling capacity problem, as well as the
threatening safety issues are of an order of magnitude greater.
Therefore, the focus of the study will be on the
benefits of solving capacity problems in the two regions with the
largest capacity deficiency i.e. Europe and USA, and on the global safety
enhancement associated with a system-wide introduction of ADS-B. The
overall C/B study should be made on the assumption that, by the year 2007, all
airspace and tarmac users are equipped to a level that allows for participation
in the Collaborative ATM System. The study should also take into account
material from other related studies e.g. those conducted by EU, Eurocontrol,
FAA, CAFT and IATA.
17.3 "Tiger Team" Activities
Identifying and implementing benefits for the
early users is essential. To achieve this, it is crucial that potential users
and service providers work at a local level e.g. at an airport to identify
specific areas where ADS-B and increased situation awareness on the ground and
in the air, can directly improve safety and increase capacity. The "Tiger
Teams", that conduct these projects will have to set achievable objectives that
will generate quantifiable operational benefits for all parties. It is also
necessary to address the issue of benefits for equipped aircraft in the
en-route environment.
To accomplish this, we have proposed three
"Tiger Teams" within the framework of NEAN Update Programme (NUP). These teams
should address the issues of local implementation of procedures and services
based on ADS-B at:
- Tiger Team 1: Frankfurt Airport Proposed
partners: Lufthansa, DFS, Airbus and Frankfurt Airport
- Tiger Team 2: Stockholm Arlanda Airport
Proposed partners: SAS, SCAA, Stockholm Arlanda and Boeing
- Tiger Team 3: Maastricht UAC. Proposed
partners: Eurocontrol, Lufthansa, SAS and Aircraft Manufacturers
Examples of procedures and services at a local
level include, but are not limited to:
- Procedure improvements during parallel
approaches
- Reduced separation between ADS-B equipped
aircraft in the TMA
- Operational enhancements for ground
operations in reduced visibility.
Benefits for the en-route sector could include,
but should not be limited to:
- reduced en-route separation between ADS-B
equipped aircraft
- a 15% reduction of en-route charges for
equipped aircraft, etc.
- All procedures to have the aim of
enhancing system safety and throughput.
18. Summary
The need for major changes to the existing Air
Traffic system is urgent. The mounting statistics on capacity restrictions,
delays, controller overload and safety are clear indicators of the need for
change. The traditional solutions of 'providing more tools and support to ATC'
will not significantly improve capacity, are expensive and do not tackle the
underlying problems. A revolutionary approach is not tenable or feasible -
purely from an implementation perspective. Rather, an evolutionary approach as
outlined in this paper will yield the earliest benefits and provide for a
smooth transition towards a more efficient Air Traffic Management System.
The evolution of the Air Traffic System towards
a less interventionist Air Traffic Management System is in line with the ICAO
CNS/ATM concept. This can be achieved with the Trajectory Concept,
Collaborative ATM and tools like ADS-B, supported by technologies such as VDL
Mode 4 able to provide real-time exchange of information including broadcast,
point to point and air to air communications. The changes required to the
current Air Traffic System described in this paper are necessary, evolutionary,
logical and are realistic and achievable in the near term. These changes emerge
simultaneously from considerations of the requirements for the Ground and
Air-side.
The proposals will enhance Pilot and ATC roles
and will significantly improve performance. They are also in-line with
Eurocontrol's EATMS Target Concept and are achievable in the timeframe set in
Eurocontrol's ATM2000+ document. No realistic alternatives have yet been
proposed.
The proposals outlined in this paper for
integrating VDL Mode 4 into the Aircraft Avionics Architecture are based on
Industry experience and represents a low cost solution to these problems.
The industry needs to commit to an evolutionary
approach to the re-organisation of the airspace to handle the ever-increasing
growth in Air Traffic. Both the development and transition phases outlined in
this paper must be completed before the Air Traffic System reaches saturation.
If not, the resulting chaos and loss of revenue to the airlines will be a
perfect illustration of the "Law of diminishing returns". |
