ADS-B in the North Sea
Kim O'Neil
Advanced Aviation Technology Ltd.
www.aatl.net
Abstract
The introduction of ADS-B (Automatic Dependent
Surveillance - Broadcast) has the potential to significantly improve the
safety, efficiency and costs associated with aircraft operations - especially
in isolated locations. Solutions are now available to greatly improve
communication, navigation and surveillance services in areas such as the North
Sea for both offshore helicopter operations and for civil aircraft serving
those isolated airports that the offshore helicopters operate from. These long
overdue improvements can lead to widespread cost/benefits for all aspects of
aircraft operations in the North Sea. Significantly, such improvements can be
made quickly and at relatively low cost. ADS-B implementation in the North Sea
begins this Autumn, for helicopters operating out of Shetland to the North Sea,
under the EU funded NUP project.
1. Introduction
The costs of services currently provided to offshore
helicopter operators in the North Sea are high. These costs include the
provision of (limited) radar services, en-route procedural services, ATS
related engineering services and, of course, the provision of air traffic
controllers. North Sea operations have been "black starred" by IFALPA for many
years - largely due to the lack of navigation services and, rather
surprisingly, due to the lack of capacity at aerodromes at peak periods.
There are fundamental limitations in current radar and
voice-based procedures, which have evolved over many years in the North Sea.
Providing radar cover to offshore locations has always been problematic anyway
(as helicopters often operate at low levels), and far too costly. These costly
restrictions are now both unnecessary and avoidable as advances in CNS/ATM
technology such as ADS-B, now offer new solutions, free from the restrictions
of traditional ground-based navaid methods. The EU funded NUP project will
directly demonstrate the benefits of ADS-B and related services in a major new
project due to begin this Autumn.
2. Scasta Aerodrome in the Shetlands
Scatsta Aerodrome in the Shetland Islands serves the
offshore industry in the East Shetland Basin. Helicopters typically fly out to
rigs, ferrying personnel and various supplies. There is also a connecting fixed
wing service from Scatsta to Aberdeen. The offshore operators and the oil
companies that pay the bills are, naturally, anxious to improve safety and
address current operational restrictions at Scatsta due to aircraft dependence
on NDB approaches, the limited radar services and restrictive procedures.
Upgrading these services by traditional methods would normally be prohibitively
expensive and unjustified for such an aerodrome, due to the relatively low
volume of traffic over the course of a year.
However, like many similar operations around the
world, there are periods when Scatsta can become quite busy. At regular
intervals up to five helicopters can arrive together from offshore rigs to
disembark personnel for onward transport by fixed wing aircraft to Aberdeen in
Scotland. Ideally, the arriving helicopters would disembark passengers to the
waiting fixed wing aircraft as quickly as possible (which requires closely
spaced arrivals) - to avoid unnecessary delays to passengers on the next leg of
their journey. In good visual conditions, this can be achieved relatively
quickly and smoothly.
However, visual conditions in the Shetlands are often
not good and can change rapidly. Terrain is also a significant factor, as
Scatsta is surrounded by hills with no simple conventional navaid solution to
both runway ends. Decision heights are high at 520'. The combined result can be
significant delays, at an aerodrome that has only an NDB and limited radar
services.
Conventional solutions might typically propose an
offset DVOR. The DVOR would have to be offset from the runway, as it has to
serve both runway ends. This could not be achieved (due to terrain), with the
navaid located near the runway. Yet, this would only marginally improve
decision heights and would be very expensive (adding other costs, delays and
logistical problems for a physically remote aerodrome). Relocating the NDB
would, again, only bring limited benefits. Radar approaches could have the
advantage of enabling significant reductions in decision heights, but at the
price of reduced capacity (as only one aircraft at a time can be handled by
this procedure). A navaid would still be required for the missed approach.
Improved solutions to these issues are available,
based on satellite navigation and Automatic Dependent Surveillance - Broadcast
(ADS-B). These satellite navigation techniques have been developed in various
international fora and the corresponding technologies have been adopted in ICAO
SARPs. Both are fully in line with ICAO's CNS/ATM Concept.
CNS/ATM solutions can now be deployed in the North Sea
to:
- Improve safety
- Improve navigation
- Improve operating procedures
- Improve operating flexibility
- Provide new services
- Significantly reduce infrastructure/operating
costs
- Improve overall costs and services
3. Current ATC Methods and Charges
There has been significant contraction and
consolidation of helicopter operations in the North Sea in recent years (as has
been the case in many other similar locations). This has largely been the
result of changes in manning practices at offshore installations and by
economic conditions. Nevertheless, the relatively high cost of helicopter
services to the North Sea has exacerbated this contraction. Yet not all of this
is due to the physical costs of operating helicopters.
Overall helicopter operating costs, are significantly
affected by the "fixed costs" that flow from the limitations of existing ATC
procedures and associated ATS charges. The impact of these charges has a major
affect on the commercial viability of helicopter operations.
It follows
that:
- Operating restrictions significaantly affect costs
e.g. duty times, routes, scheduling etc.
- Reducing en-route navigation fees/costs would
benefit the industry as a whole.
4. ICAO CNS/ATM Concept
ICAO has recognised the limitations of traditional ATC
services based on radar and ground Navaids and developed the CNS/ATM Concept
based on satellite navigation and advanced datalink technologies. Automatic
Dependent Surveillance - Broadcast (ADS-B) is a cornerstone of this concept.
ADS-B enables aircraft to calculate their position using navigation information
available (e.g. GPS) and broadcast this to ground-stations and other aircraft.
The operational benefits of this approach are enormous, especially to
helicopter operations in remote locations.
ICAO Standards and Recommended Practices (SARPs) have
now been published and ADS-B equipment can now be bought 'off the shelf' at low
cost for installation in aircraft and at airports. ICAO has published SARPS for
VHF Datalink Mode 4 (VDL mode 4) implementing ADS-B for surveillance
applications (and this is now being extended to navigation and communications).
VDL mode 4 can be combined with display technology giving full moving map and
traffic information including Air Traffic Information Services (ATIS) and other
up-linked services e.g. traffic data.
5. ADS-B and VDL mode 4
ADS-B implemented by VDL mode 4 can improve all
surveillance services, including ground-to-air and air-to-air and
ground-to-ground surveillance. ADS-B reports contain essential information
including identity, position, altitude, speed, direction and other data.
Typical benefits of implementing ADS-B in VDL mode 4 (especially for remote and
otherwise poorly served locations) is that it:
- Is broadcast and can be received by other aircraft,
vehicle or ground stations.
- Contains more information than radar data and is
transmitted at higher rates.
- Provides end-to-end communications e.g. air-to-air
without ground infrastructure.
- Operates at low power, typically 5-20W, with
long-range coverage up to 200 NM
(with better than normal line of sight
restrictions).
- Has higher capacity per bandwidth and spectrum
occupancy than other data links.
- Has equal or better surveillance at a significantly
lower cost than radar.
- Is cellular - enabling coverage over wide areas in
difficult and isolated terrain.
- Can be easily deployed in hostile
environments.
ADS-B and VDL mode 4 services have much to offer
helicopter operations in the North Sea. Many of the potential benefits
translate directly into tangible improvements in safety, capacity, efficiency
and can lead to overall reductions in operating costs. ADS-B and VDL Mode 4 can
support many CNS applications, including:
- Pilot situation awareness
- Traffic Information Service Broadcast (TIS-B)
- Flight Information Service Broadcast (FIS-B)
- Airborne Separation Assurance (ASAS)
- Advanced Surface Movement Guidance and Control
(A-SMGCS)
- Enhanced ATC surveillance
- Runway Incursion
- Parallel Runway Monitoring
- Controller-Pilot Data Link Communications
(CPDLC)
- Pre-departure clearances (PDC)
- GNSS Augmentation (e.g. replacing Non Precision
Approaches)
These applications have been widely demonstrated in
many operational trials.
The key benefits can be summarized as: safety,
capacity, efficiency and cost reduction.
VDL mode 4 is especially
cost/effective when compared with radar and conventional navigation aids. The
cost/benefits are good even when existing services are provided by radar (due
to improved through life costs).
VDL mode 4 is also very flexible in its operating
environment, being easy to install and maintain. It operates at low power and
is physically unobtrusive (externally requiring only small VHF and GPS
aerials). VDL mode 4 can be fitted in ground stations, on aircraft, to vehicles
and to offshore installations (including sea going vessels). Hence VDL mode 4
is ideal for offshore helicopter operations.
6. Flight Watch
VDL mode 4 enables Flight Watch capabilities enabling
Flight Operations to more effectively manage helicopter resources. It also
enables a straightforward flight watch to be maintained on board offshore
installations (for regulatory reasons, careful distinction needs to be made
between Flight Watch and an operational Air Traffic Service).
7. Improving Navigation,
VDL mode 4 ground stations can also provide
differential GNSS corrections and integrity data to aircraft to enhance
navigation. This enables satellite navigation to be operationally exploited in
environments where alternative means of navigation are not available, are too
expensive, are too limiting or are simply not feasible.
The use of satellite navigation to provide high
integrity services such as landing systems has been an area of rapid
development. For example, the FAA has undertaken a massive programme of GPS
procedure design in the US - over 500 procedures a year are being produced for
all major airports. Criteria for the design and deployment of GPS procedures
have been established. Airbus and Boeing both claim to be able to deliver
aircraft that are 'GPS Cat I certified'. GPS is in practical everyday use in
many operational civil aircraft flying today.
Particular safety benefits can be achieved in the
replacement on "Non Precision Approaches" (NPA). These have been identified as
a major risk factor in aircraft operations and a causal factor in many
accidents.
Specific concerns with Non-Precision Approaches
include:
- Unacceptable Hazards
- Terrain Problems
- Poor Situation Awareness
- Unsatisfactory Decision Heights
- Poor Operational Performance
To this must be added the severe general restrictions
in operating procedures caused by the limitations of existing ground navaids
such as NDBs and DVORs. These adversely affect decision heights, create
unnecessarily complex procedures (where terrain awareness can be impaired) and
lead to less than optimal positioning of holding patterns etc. Despite the
obvious benefits of GNSS based procedures, regulatory confidence in satellite
navigation will best be achieved by a phased approach. This is the approach
that will be taken by the NUP project in the North Sea.
8. VDL mode 4 in the Offshore Environment
Significant practical experience has already been
gained with VDL mode 4 prototypes in offshore applications. Extensive and very
successful flight trials were carried out to the Tyra rigs 100NM off the coast
of Denmark. This was done as part of the North European ADS-B Network (NEAN)
project (a precursor to NUP). VDL mode 4 was installed in several locations in
Denmark and on the Tyra East rig where a Maesk helicopter was also equipped for
the trials. In related trials in the current NUP project, work will also be
carried out in Denmark and Norway.
9. NUP: Implementing ADS-B at Scatsta
It is proposed to equip 10 helicopters with ADS-B
(implemented by VDL mode 4) and install ground stations at Scatsta in Shetland
as part of the EU funded NUP programme. Installation will begin in Autumn 2001
and operational trials will begin early in 2002. New GNSS procedures will be
developed and trialed in a step-by-step manner, in order to demonstrate the
improvements possible with CNS/ATM implementation. Care will be taken to carry
out a full risk and hazard analysis as part of the Safety Case that will be
developed for ADS-B operations at Scatsta. A full cost/benefit study will also
be carried out in order to demonstrate the commercial benefits of ADS-B
implementation.
10. Summary
There are significant opportunities to improve
communication, navigation and surveillance services at Scatsta and in
helicopter operations in the North Sea (including approaches to offshore
installations). These improvements can lead to radical improvements in safety,
efficiency and reductions in costs. A key element in achieving these
improvements is the full adoption of satellite navigation and datalink services
and in particular ADS-B. VDL mode 4 fully implements these functional
improvements and provides major cost/benefits over existing costs and
services.
Specifically, it is time to upgrade existing
procedural services to a level more in line with modern aircraft operations.
Current procedures, methods and operating practices are expensive, inefficient
and adversely affect the commercial operation of helicopter services. Satellite
navigation can significantly improve operating procedures, reduce decision
heights at aerodromes and improve routes and holding patterns. These all lead
to corresponding gains in safety, efficiency and cost reduction.
VDL mode 4 also provides a communication
infrastructure on which many other services can be built at low cost. Typical
additional services that could be provided include: Airline Operational
Communications (improving efficiency of helicopter operations), maintenance and
engine performance (improving flight safety), Flight Watch, automated ATIS and
related Met services, differential GPS corrections and integrity data (improved
navigation and flight safety), asset management, emergency and disaster
management and coordination, remote monitoring and many other functions.
The publication of ICAO SARPs, Eurocae MOPS and
European Standards for VDL mode 4, mean that these technologies can be
introduced and certified for many beneficial and cost/effective operational
services. The NUP project aims to show these benefits directly. |
