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Aena GBAS CAT I Implementation at Malaga Airport:
Towards an Operational GNSS Landing System
Patricia Callejo, Aena Satellite Navigation Division, Spain
Aitor Alvarez, Aena Satellite Navigation Division, Spain
Fco. Javier De Blas, Aena Satellite Navigation Division, Spain
BIOGRAPHY
Patricia Callejo is an Aeronautical Engineer
specialized in Air Navigation Systems by the
Polytechnic University of Madrid (Spain). Within
the Aena Satellite Navigation Division, she is in
charge of technical issues, data processing and
analysis of onboard and on-ground systems
performances since 2006. Her background in data
collection campaigns and data analysis comes from
her work in Airborne Remote Sensing field, in
which she was specialized in positioning and
orientating remote sensors for the Spanish National
Institute for Aerospace Technology (INTA).
Aitor Alvarez is an Aeronautical Engineer from the
Technical University of Madrid (Spain). He works
at Aena as the Head of the GNSS Certification
Department being in charge of the Aena GNSS
(EGNOS and GBAS) implementation projects.
Since February 2009, he is a member of the ESSP
SAS Board of Directors.
Fco. Javier de Blas is an Aeronautical Engineer and
Master in Airport Systems from the Polytechnic
University of Madrid (Spain). After working for
Senasa (Services and Studies for Air Navigation and
Aeronautical Safety) for four years, he began
working as a GNSS consultant for the Aena Satellite
Navigation Division in 2008, dealing with GNSS
implementation projects.
INTRODUCTION
Aena started its GBAS CAT I Programme in the late
90s. By means of carrying out the installation of
several GBAS Ground Station Prototypes, Aena’s
Satellite Navigation team has had the opportunity to
acquire the experience and know-how to continue
working towards a certifiable CAT I system
installation. Therefore and after the complete
technical development of the new SLS-4000 system
and its installation in Malaga Airport, Aena is
facing up to the last step of the way to make GBAS
become a reality: the Operational Implementation
phase.
This phase represents a great challenge by its own:
it will be the first time for Aena and the Spanish
Civil Aviation Authority to manage the operational
approval of a New Air Navigation System within
the SES (Single European Sky) Regulation
framework. As a consequence a group of activities
affecting every aspect of the service provision
(maintenance, safety, security, charting, AIS, etc.)
will be done to integrate every change produced by
this new system into the structure of Aena and to
comply with every requirement included in the
regulations.
At the same time and due to the operational purpose
of this process Aena is improving its cooperation
activities with users. In this sense Aena and some
Airlines (Air Berlin, Thomson) are working together
to promote the operational implementation at
Malaga, and in the near future in other Spanish
Airports. Currently Air Berlin is playing a key role
by monitoring GBAS performances in their regular
approaches to Malaga Airport, and reporting their
results. In addition to these activities Aena keeps
collaborating with other stakeholders worldwide
(FAA, JACB, DFS).
This paper covers on one side the present status of
the Aena GBAS Programme and the description of
the Spanish approach to the process to obtain the
Operational Approval of a New Air Navigation
System within the SES Regulation framework.
On the other side, special attention is paid to the
results of the experimental tests on the performances
of the GBAS Ground Stations. Both in-flight and
on-ground trials are described and results are
presented. Several aspects as accuracy, integrity and
availability as well as broadcast signal coverage are
analysed versus CAT I specifications along a
number of experimental tests performed at different
sites.
AENA’s GBAS PROJECT STATUS
As mentioned before, Aena started its GBAS
Programme in the late 90s. The starting activities
consisted in the installation and first trials with an
experimental differential station. Later on the first
complete ground station installation was a SCAT-I
(SLS-2000) manufactured by Honeywell. This
system consisted of three GPS reference receivers
and a rackable processing unit including corrections
computation and VHF broadcasting both within the
same unit. A VDB transmitting antenna completed
the system.
After this installation Aena upgraded it to the PSP
CAT I Prototype (Honeywell’s SLS-3000 Beta
LAAS Plus). This ground system comprises four
improved GPS antennas and four GPS receivers
referred as Remote Satellite Measurement Units or
RSMUs. The antennas are composed of a High
Zenit Antenna (HZA) and a Multipath Limiting
Antenna (MLA), which data are integrated into a
sole GPS solution by software. In addition this
ground system comprises a Differential GPS cabinet
and a VHF Data Broadcast cabinet. The first one is
in charge of computing the GPS differential
corrections, performing the integrity monitoring and
synchronizing the VDB transmission. The second
one is in charge of transmitting the VHF signal to
the VHF antenna and monitoring this signal. Within
the PSP, the transmission power was increased in
order to achieve the coverage volume according to
CAT I requirements. In this way, the GBAS VDB
antenna is responsible of radiating the GBAS signal
from the station to the aircraft. Moreover eleven
integrity monitors plus eleven continuity monitors
and various Built-In-Test-Equipment monitors
complete the system improvement in order to
achieve CAT I performances.
Presently the incoming step goes through the
installation of the brand new GBAS ground system
SLS-4000. A system also manufactured by
Honeywell which is expected to obtain the FAA
System Design Approval by the mid of this year and
the FAA Operational Approval by the end of 2009.
The operational philosophy of the SLS-4000 is
similar to the PSP system but significant software
and hardware improvements have been introduced
at the design level. Four new GPS antennas will
replace the current ones. These new antennas are
specially designed to minimise the multipath effects.
The previous two cabinet configuration is unified in
a single rack integrating the processor and the VDB
subsystems but preserving and even improving the
redundancy model from its predecessor. Four
Differential Correction Processors organized in two
independent channels plus two VDB transmitters
and two VDB receivers for signal monitoring
purposes are part of this advancement. Some other
improvements affect the user/maintenance interface
and the data recording capability of the system.
Equipment for Monitoring GBAS
With the aim of monitoring and testing GBAS
signal quality and performances, several systems
and tools have been implemented both on ground
and onboard.
With regard to ground systems and tools, a GNSS
Monitoring Station or GMS was installed in the
surroundings of the GBAS facility. The GMS 670 is
an independent monitoring system manufactured by
Thales ATM. It monitors the GPS space segment as
well as the GBAS ground segment. The GMS
provides a real time end to end validation capability
of the differentially corrected GPS signal equivalent
to the “ILS-field monitor”.
This monitoring station is composed of a main
cabinet, which includes data processors and
recorders, two GPS antennas, one connected to a
GPS/SBAS receiver and the other to a GPS/SQM
receiver, a VHF antenna connected to a Telerad
VHF receiver and an integrated interference
monitoring module (see Figure 1).
Figure 1. GNSS Monitoring Station components:
GMS cabinet, GPS/SBAS and GPS/SQM receivers
antennas mounting and VHF antenna.
The GMS receives and process GNSS signals, both
GPS and SBAS, receives the GBAS messages from
an external independent CAT I GBAS station,
monitors these messages as well as the VDB link,
performs position monitoring by computing 3D
errors, 2D errors, vertical errors and protection
levels, displays real time data, parameters and
operational status on-site and online, is able to plot
historical data versus time and performs permanent
recording on hard disk of all relevant data, including
GPS raw data, position solutions, alerts and monitor
alarms. This capability allows for post-processing
and incident investigation. Moreover, Aena has
developed a GMS data convertor SW application in
order to convert the raw data recordings of the GMS
into Pegasus readable files. This option permits the
user to analyse GMS data with the commonly used
Pegasus toolset.
In addition, Aena’s GMS integrates an interference
monitoring function by means of the RFI module.
This module is continuously monitoring the L1
signal against the ICAO GNSS SARPS interference
mask [1]. The most critical interference signals are
those within the frequency range of 1.575 GHz ± 10
MHz. In case of an interference event, spectrum
data is stored and an alarm is raised in the GMS user
interface application.
Figure 2. GMS VDB link real time monitoring.
An additional ground system is the VDB signal
recording portable platform, developed by Aena
for experimental measurements of GBAS signal
field strength at the ground level. This portable
platform is composed of a Telerad VDB receiver, a
VHF portable antenna, a Novatel OEM4 GNSS
receiver plus antenna and two computers to manage
and record data. The layout of this platform is
depicted in Figure 3.
Figure 3. VDB signal recording portable platform
connections layout.
Figure 4. VHF portable antenna mounted on a mast
for static measurements.
Figure 5. VHF and GPS portable antennas mounted
on a vehicle for dynamic measurements.
With regard to airborne systems, Aena’s investment
is dedicated to the development of a GBAS
airborne experimental platform. In this sense, a
Beechcraft King Air A-100 is instrumented for
GBAS and SBAS experimental flight tests.
Figure 6. Beechcraft King Air A-100.
On the subject of GBAS flight testing purposes, the
equipment integration includes a Rockwell-Collins
Multi-Mode Receiver, MMR R-C GLU 925, a
Telerad VHF receiver, a GPS/SBAS independent
receiver and a Processing Console which acquires,
stores and processes data as well as it displays
navigation solutions in real time. The layout of this
platform is depicted in Figure 7.
Figure 7. Airborne platform connections layout.
Currently, this platform is being upgraded at HW
level by the integration of a new SBAS receiver,
several ruggedized storage devices and more
powerful processing units. At the same time, it is
being redesigned at SW level for full compatibility
with Pegasus post-processing.
GBAS SCENARIO AT MALAGA
Malaga is located in the South of Spain, next to the
Mediterranean Sea. Malaga’s Airport is the
southernmost airport on the European continent. It
connects seventeen Spanish cities and almost one
hundred European cities. It is ranked fourth in the
Spanish airport network and twenty-fifth in Europe.
Currently, this airport is being remodelled and
expanded. A new terminal area to double the
airport’s current capacity, new aprons and an
airfield expansion consisting in the construction of a
second runway depicts Malaga’s Airport as the
perfect scenario for new technologies opportunity.
At present, Malaga’s Airport is provided with one
runway serving two ILS CAT I approaches:
RWY13 and RWY31. The first one comes from a
mountainous area with a glideslope of 3.2º and the
second one comes from the sea with a nominal
glideslope of 3.0º.
Figure 8. Malaga’s Airport airfield.
Within this scenario, Malaga’s Airport was chosen
for the materialization of the Aena’s GBAS
Programme.
The current GBAS Ground System components
(SLS-3000 Beta LAAS Plus) were installed in 2006
(see Figure 9).
Figure 9. Current GBAS components: the DCP and
VDB racks, a GPS antenna with the HZA and MLA
components and the VDB antenna.
This ground facility is going to be upgraded in May
2009 to the certifiable SLS-4000. All the compo-
nents from the preceding ground system will be
replaced except the VDB antenna which will remain
from previous installation (see Figure 10).
Figure 10. SLS-4000 GS components: DCP/VDB
rack, GPS MLA antenna and VDB antenna.
Malaga’s present airport layout showing the
locations of the GBAS related ground equipment
can be seen in Figure 11.
Figure 11. GBAS related ground equipment
locations at Malaga Airport.
Ground Tests Results
In order to check the GBAS signal coverage down
to 12 feet above terrain [3], some ground tests have
been performed using the VDB signal recording
portable platform.
Firstly the portable platform VHF Rx antenna gain
pattern was experimentally characterized to correct
the field strength measurements. The Rx antenna
horizontal pattern obtained from the characterization
process can be observed in Figure 12:
5
0
-5
-10
-15
0
30
60
90
120
150
180
210
240
270
300
330
RX Antenna Pattern Diagram
Figure 12. VHF Rx portable antenna calibrated
horizontal pattern.
After that, the GBAS signal was measured
throughout the runway and the service roads. Field
strength data and GNSS observables were collected,
corrected and correlated. The SW applications in
charge of acquiring data are the Pegasus Online
Convertor tool for the VHF data and the GPSolution
(Novatel) for the GPS data. To obtain the corrected
GPS position solution, GrafNav (Novatel) SW tool
was applied. To correct the field strength
measurements some Matlab specific routines were
developed.
Figure 13 shows the following sets of data versus
time: the raw field strength as directly measured by
the VHF receiver (in green), the theoretical field
strength estimated by using only free space losses
(in red), the theoretical field strength introducing
losses with multipath (in purple) and the corrected
field strength (in blue) computed by the application
of the correction for cable losses, the factory
characterization of the VHF receiver error and the
calculated Rx antenna gain pattern.
399900 399950 400000 400050 400100 -100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
Time (s)
Fie
ld S
tre
ng
th (
dB
m)
RWY31: Comparison of estimated signal and signal at the antenna input (dBm)
Free Space Multipath Corrected Measured
Figure 13. Comparison of measured, corrected and
theoretical field strength.
The result of these comparisons are coherent with
the expectations, since the free space losses model is
only valid for short distances with respect to the
VDB antenna (right area of the graph) where
multipath effect is negligible. The improved model
is only valid for long distances (left area of the
graph) where multipath effect becomes quite
significant.
Figure 14 depicts the results of the field strength
measurements on both RWY31 and RWY13
revealing a good matching. Figure 15 locates both
sets of data together with the service roads
measurements on Malaga’s Airport image. It was
verified that the measured signal along both
runways and thresholds was good enough and
appropriate for autolanding. The corrected signal
reached a maximum signal of –11 dBm in RWY31
and –13 dBm in RWY13 and a minimum of –61
dBm in RWY31 and –60 dBm in RWY13. These
values are far away from the limits specified in [1]
and [2].
VDB Tx Antenna position
GBAS Reference Receivers positions
GNSS Monitor System (GMS) position
Field Strength comparison
-65
-55
-45
-35
-25
-15
36.665 36.67 36.675 36.68 36.685
Latitude (º)
Fie
ld S
tren
gth
(d
Bm
)
RWY31 RWY13
Figure 14. RWY31 and RWY13 corrected field
strength data comparison.
Figure 15. Malaga’s Airport GBAS field strength
level at 12 ft above terrain.
Flight Tests Results
The GBAS signal performance and coverage has
been tested through several flight tests carried out
with Aena’s GBAS airborne experimental
platform. A number of approach procedures to both
thresholds have been flown in addition to several
maneuvers specific to check the signal coverage
volume limits according to [1] and [2].
To compute the flown trajectories or Actual Flight
Paths, GrafNav (Novatel) SW application is used to
compute a CPDGPS position solution. To get the
performances of the Navigation System the Pegasus
modules GNSS_Solution and Dynamics are applied
to the MMR data recordings. Several tools as
Filewatch, M-File runner and Matlab graphs are
used to visualize and analyse the results of the
processing.
Figure 16. Example trajectory of some approaches
to RWY31 and a Circular Orbit. CPDGPS position
solution plotted over Malaga airport surroundings.
Figure 17. Approaches to RWY31. Navigation
System Flight Path altitude vs distance to LTP.
The analysis of the GBAS positioning performance
of the airborne segment comprises the study of the
positioning errors, which will be studied by
analysing the Navigation System Errors, the Flight
Technical Errors and the Total System Errors. The
Path Definition Error (PDE) will be normally
assumed as negligible.
Figure 18. Definition of positioning error
components.
The Navigation System Flight Path (NSFP)
computed by the MMR according to GBAS
received data was very accurate. In fact, the Cross
Track Navigation System Error mean (95% of the
absolute values) was around 0.20 meters and the Up
FAP
IF
Track Navigation System Error mean (95% of the
absolute values) was around 0.70 meters for the
approaches to RWY13 and 0.50 meters for the ones
to RWY31. The Total Navigation System Error
mean (95%) was lower than 0.75 meters in both
procedures. Figure 19 shows the Navigation System
Error values for some approaches to RWY13.
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
x 104
-2
-1
0
1
2Approaches to RWY13 - Cross Track NSE vs Distance to LTP
Distance to LTP (m)
NS
E C
T (
m)
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
x 104
-2
-1
0
1
2Approaches to RWY13 - Up Track NSE vs Distance to LTP
Distance to LTP (m)
NS
E U
T (
m)
AF01
AF02
AF03
AF04
Figure 19. Approaches to RWY13. Navigation
System Error cross and up track components vs.
distance to LTP.
Regarding the Flight Technical Errors (FTE), from
the Final Approach Point (FAP) on, the Cross Track
FTE remained lower than 100 meters in the majority
of the approaches. In the complete set of approaches
the Cross Track FTE presented a decrease tendency
with distance, being lower than 50 meters from 10
kilometres down to the LTP. It is worth mentioning
that the Cross Track FTE was negative through all
the approaches, which could be due to cross-wind
conditions, a pilots characteristic flight manner
when facing a procedure, or a navigation system
offset. In the final approach segment the Up Track
FTE remained lower than 100 meters for the whole
set of approaches. Attention must be paid on the fact
that, in the majority of the approaches, the error was
always positive. This means that the path was flown
at a higher altitude than the guidance, probably
because of safety proceedings.
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2
x 104
-200
-150
-100
-50
0
50
100
150
200Approaches to RWY13 - Cross Track FTE vs Distance to LTP (Final approach segment)
Distance to LTP (m)
FT
E C
T (
m)
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2
x 104
-200
-150
-100
-50
0
50
100
150
200Approaches to RWY13 - Up Track FTE vs Distance to LTP (Final approach segment)
Distance to LTP (m)
FT
E U
P (
m)
AF01
AF02
AF03
AF04
Figure 20. Approaches to RWY13. FTE cross and
up track components vs. distance to LTP inside the
final approach segment.
The analysis of the GBAS integrity and availability
performance covers the study of the Protection
Levels (PL) and Alert Limits (AL) as well as their
interrelation. On this topic, Figures 21 and 22
present the Lateral and Vertical Navigation System
Error (red) together with the Lateral and Vertical
Protection Levels (green) and the Lateral and
Vertical Alert Limits (blue) for a set of approaches
to RWY31.
0 5000 10000 150000
10
20
30
40
50
60
70
Distance to LTP (m)
LN
SE
- L
PL
- L
AL
(m
)
Approach AU01
0 5000 10000 150000
10
20
30
40
50
60
70
Approach AU03
Distance to LTP (m)
LN
SE
- L
PL
- L
AL
(m
)
0 5000 10000 150000
10
20
30
40
50
60
70
Approach AU04
Distance to LTP (m)
LN
SE
- L
PL
- L
AL
(m
)
0 5000 10000 150000
10
20
30
40
50
60
70
Approach AU05
Distance to LTP (m)
LN
SE
- L
PL -
LA
L (
m)
LAL
LNSE
LPL
Figure 21. Approaches to RWY31. Lateral NSE,
LPL and LAL vs. distance to LTP.
0 5000 10000 150000
5
10
15
20
25
30
35
40
45
Approach AU03
Distance to LTP (m)
VN
SE
- V
PL
- V
AL
(m
)
0 5000 10000 150000
5
10
15
20
25
30
35
40
45
Approach AU04
Distance to LTP (m)
VN
SE
- V
PL
- V
AL
(m
)
0 5000 10000 150000
5
10
15
20
25
30
35
40
45
Approach AU05
Distance to LTP (m)
VN
SE
- V
PL
- V
AL
(m
)
VAL
VNSE
VPL
0 0.5 1 1.5 2
x 104
0
10
20
30
40
50
Distance to LTP (m)
VN
SE
- V
PL
- V
AL
(m
)
Approach AU01
Figure 22. Approaches to RWY31. Vertical NSE,
VPL and VAL vs. distance to LTP.
Likewise concerning the integrity assessment, the
Safety Index parameter represents the ratio between
the navigation system error and the protection level
at the same point. This parameter indicates that
integrity requirements are met when it is below 1.0.
Next figure represents Safety Index values versus
the distance to the LTP for the approa-ches to
RWY13 and to RWY31. The lower the Safety Index
is, the safer the manoeuvre in terms of integrity
margin and misleading information events.
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
x 104
0
0.2
0.4
0.6
0.8
1Approaches to RWY13 - Vertical Safety Index
Distance to LTP (m)
NS
E U
T / V
PL
AF01
AF02
AF03
AF04
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
x 104
0
0.2
0.4
0.6
0.8
1Approaches to RWY13 - Lateral Safety Index
Distance to LTP (m)
NS
E C
T / L
PL
0 2000 4000 6000 8000 10000 12000 14000 16000 180000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1Approaches to RWY31 - Vertical Safety Index
Distance to LTP (m)
Sa
fety
In
de
x (
NS
E U
T / V
PL
)
0 2000 4000 6000 8000 10000 12000 14000 16000 180000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1Approaches to RWY31 - Lateral Safety Index
Distance to LTP (m)
Sa
fety
In
de
x (
NS
E C
T / L
PL
)
AU01
AU03
AU04
AU05
Figure 23. Approaches to RWY13 and to RWY31
respectively. Safety Index vs. distance to LTP.
It must be stressed that for all the flight tests
executed up to date, the Navigation System Errors
have remained well below the Protection Levels,
which means that integrity was provided for the
approaches. Moreover, the Protection Levels
computed by the MMR during the flight tests were
always below the Alert Limits, hence assuring the
availability in every of the approaches.
Regarding GBAS signal coverage, Figure 24
represents field strength values collected during
some approaches to RWY31. The approaches
intervals are marked in the graph. It can be observed
that the values do not reach the minimum value of –
87 dBm (red line in the graph). The four approaches
present comparatively the same boundary values:
maxima around –50 dBm and minima around –80
dBm. The mean values vary from –63 to –68 dBm.
The highest values in the graph correspond to the
instant when the aircraft passed above the ground
station VDB transmitter antenna (yellow and red
samples in the graph).
Figure 24. Approaches to RWY31. GBAS signal
field strength vs. time.
Figure 25 represents the field strength values during
a circular orbit manoeuvre. This manoeuvre is used
to check the GBAS signal lower level at the
coverage volume limits. The most significant event
appears in the middle of the graph, where an interval
of 5.5 minutes contains no data (from 292568 sec. to
292902 sec.). It can be stated that there is a shadow
area where the GBAS signal cannot be reached
because of the local orography. This event happens
in an area where approach procedures are not
affected (see the orange marked region within
Figure 25). Apart from that event, it can be
observed that a few values were below the minimum
of –87 dBm (red line in the graph). The rest of the
samples present their mean value around -75 dBm.
287800 288000 288200 288400 288600 288800 289000 289200 289400 289600 289800 290000 290200 290400
-95
-90
-85
-80
-75
-70
-65
-60
-55
-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
Approaches to RWY31 - Field Strength vs Time
GPS Time (s)
Fie
ld S
tre
ng
th (
dB
m)
AU01 AU03 AU04 AU05
Figure 25. Circular Orbit. GBAS signal field
strength vs. time.
Ground Station Performance Tests Results
Based on the GBAS Reference Receivers
observables, one can perform a pseudorange
accuracy performance analysis of the GBAS
pseudorange corrections. This analysis can be
characterized by a Code-Minus-Carrier (CMC)
evaluation (see [2]). Figure 26 presents the CMC
versus elevation computed for the two components
of the current receiving antennas installed at
Malaga, the MLA and the HZA.
Figure 26. CMC of MLA and HZA versus elevation.
Although these experimental curves comply with
(are below) GAD C curve and therefore with CAT I
requirements, a significant improvement will be
achieved with the installation of the new MLA
single component antennas which are integrated
within the SLS-4000 ground system. Figure 27
presents the CMC versus elevation curve for these
new antennas and reference receivers (courtesy of
Honeywell) where continuous and lower values are
evinced.
Figure 27. CMC of new MLA single component
antenna versus elevation.
Additionally, the pseudorange corrections accuracy
can be characterized by analyzing the B-values
broadcast by the GBAS ground station (see [2]).
Figure 28 presents a GAD assessment carried out
from collected data in Malaga’s Airport according to
B-values methodology. Figure 29 presents the same
GAD assessment but based on data collected from
the SLS-4000 (courtesy of Honeywell). The
comparison between both graphs makes clear the
improvement achieved for low elevation angles
(from 5º to 40º) in the SLS-4000 new antennas and
RSMUs.
Figure 28. PR_GND estimation and GAD assessment
based on real B-values generated by the PSP GS.
291200 291400 291600 291800 292000 292200 292400 292600 292800 293000 293200 293400 293600 293800
-95
-90
-85
-80
-75
-70
-65
-60
-55
-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
Circular Orbit - Field Strength vs Time
GPS Time (s)
Fie
ld S
tre
ng
th (
dB
m)
Figure 29. PR_GND estimation and GAD assessment
based on real B-values generated by the SLS-4000
GS.
NAVIGATION SYSTEMS OPERATIONAL
IMPLEMENTATION IN SPAIN
From the start of the GBAS project Aena has been
working within a harmonized initiative coordinated
under the EUROCONTROL Landing and Take-Off
Group (LATO) and the EUROCONTROL and FAA
International GBAS Working Group (IGWG)
umbrella to assure a common strategy for the
Operational Validation of the new GBAS CAT I
systems.
Together with DFS (Germany) at European level
and with ASA and the FAA at International level,
Aena has been the first ANSP with a program for
GBAS operational implementation to be certified in
the short term, playing a leading role through the
work done within the LATO and the IGWG groups.
Once every CAT I technical objective is about to be
reached and after more than ten years from the
beginning, the Aena’s GBAS Programme is close to
its successful completion by the last challenging
step in its way: the Operational Approval.
Since 2004 the European air navigation regulatory
framework has undergone several deep changes due
to the emergence of a new concept: the Single
European Sky (SES). This new scenario stated in
the SES Regulation involves important changes in
every aspect of the air navigation service provision.
Therefore the operational approval of a brand new
navaid as GBAS represents a great challenge, as it
will be the first time for Aena as ANSP and for the
Spanish Civil Aviation Authority (DGAC) to
manage the operational approval of a new air
navigation system within the SES Regulation
framework.
Two main processes can be identified at a high level
within the complete procedure. On one hand Aena is
already certified as an ANSP since December 2006
in accordance with [4]. Nevertheless to provide this
new GBAS service Aena will have to apply for an
extension of its certificate to include this service.
As a consequence of this process to obtain an
“extended certificate” every aspect of the service
provision (maintenance, safety, security, charting,
AIS, etc.) has to be analysed to identify any impact
of the introduction of this new service and to
integrate any change needed to comply with every
requirement included in the SES Regulation. This
process involves the coordination of nearly all the
Departments within Aena which deal with the
aspects of the service provision, entailing a vast
effort at institutional level.
On the other hand, in order to ensure the
interoperability of all the systems in the EATM
network and before the system is put into service,
Aena has to produce an EC Declaration of
Verification of the GBAS ground system
confirming its compliance with the corresponding
requirements specified in [5]. To fulfill this task
Aena has developed its own process by going
further than the Regulation [5] and taking the
chance to design an ambitious process which will be
able to track every system requirement through all
the system lifecycle. This system verification
process considers four different stages related with
the evolution of the system operational
implementation:
- overall design,
- development and integration of the system,
- operational system integration, and
- system maintenance.
This identification of stages aims to ease the
tracking of the compliance with every requirement
at each verification stage where it is applicable. In
addition to that and to give the process a coherent
structure, every stated compliance will be supported
with documentary evidences guaranteeing the aimed
traceability.
As part of the System Verification process and to
cover some of the safety requirements of the system
is worth to point out that Aena has recently started a
Spanish Iono Study in order to validate the iono
threat model which is integrated in the SLS-4000
GS for the Spanish national territory. This is a
pioneer initiative involving the analysis of the GPS
observables from the receivers distributed
throughout the Spanish territory along a solar cycle.
This activity will hopefully mean a first step to a
European iono assessment.
Figure 30. Spanish territory iono assessment first
results.
Leaving SES apart and focusing at a national level,
there are some other activities defined by the
Spanish Regulation needed to operationally
implement the GBAS system that Aena is set to
comply with. The reviewing of regulations defining
air navigation phraseology, obstacle consideration
areas and the definition and approval of the
operational GBAS CAT I procedure are part of the
task to be accomplished.
Meanwhile, always bearing in mind the operational
purpose of this process, Aena is improving its
cooperation activities with users and stakeholders
worldwide in order to promote the use of GBAS and
to disseminate its capabilities. The actual interest
and cooperation of Airlines like Air Berlin and
Thomson are the basis for the future development
and expansion of GBAS, thus Aena will keep
improving its effort to gather every support to its
project.
ACKNOWLEDGEMENTS
The authors would like to thank the following
people and organisations that have provided an
invaluable support in the preparation and execution
of the tests and procedures presented within this
paper: Brian Koosmann, Mark Cady, David Jensen
and Dennis Clark (Honeywell), Paco Morales and
the rest of the Malaga ATC, Victor Cuevas, Alfredo
Serrano, Fco. José Morales and Javier Monje
(Spanish Eastern Sector Radio Navigation Aids
Maintenance Department), Miguel A. Sagrado and
the Senasa Avionics Maintenance staff jointly with
the pilots of the Aena’s experimental aircraft
(Senasa), Miguel A. Sanchez-Rosel and Alberto de
la Fuente (GMV), as well as Luis Andrada, Pablo
Haro, Javier de Andres and Rogelio Roman (Aena’s
Satellite Navigation Division).
REFERENCES
[1] ‘Aeronautical Communications. Radio
Navigation Aids’ ICAO Annex 10 Vol. I.
[2] ‘Minimum Operational Performance
Specification for GBAS Ground Equipment to
support CAT I Operations’ EUROCAE ED-
114.
[3] ‘Manual on Testing of Radio Navigation Aids’
ICAO Doc. 8071 Vol. II.
[4] Regulation (EC) No. 550/2004 of the European
Parliament and of the Council of 10 March
2004 on the provision of air navigation services
in the single European sky (the service
provision Regulation).
[5] Regulation (EC) No. 552/2004 of the European
Parliament and of the Council of 10 March
2004 on the interoperability of the European
Air Traffic Management network (the
interoperability Regulation).
ACRONYMS
AL: Alert Limit
CAT: Category (of precision approach
operation)
CMC: Code-Minus-Carrier
CPDGPS:Carrier Phase Differential GPS
DFS: Deutsche Flugsicherung GmbH
DGAC: Direccion General de Aviacion Civil
(Spanish CAA)
EASA: European Aviation Safety Agency
EATM: European Air Traffic Management
EC: European Commission
EGNOS: European Geostationary Navigation
Overlay Service
FAA: Federal Aviation Administration
FAP: Final Approach Point
FAS: Final Approach Segment
Ft: Feet
FTE: Flight Technical Error
GBAS: Ground-Based Augmentation System
GMS: GNSS Monitoring System
GNSS: Global Navigation Satellite System
GPS: Global Positioning System
GS: Ground Station
HZA: High Zenit Antenna
HW: Hardware
ICAO: International Civil Aviation Organisation
IF: Intermediate Fix
IGWG: International GBAS Working Group
ILS: Instrument Landing System
JCAB: Japan Civil Aviation Bureau
LATO: Landing And Take-Off group
LTP Landing Threshold Point
MLA: Multipath Limiting Antenna
MMR: Multi-Mode Receiver
NSE: Navigation System Error
NSFP: Navigation System Flight Path
PL: Protection Level
PSP: Provably Safe Prototype
RWY: Runway
RFI: Radio Frequency Interference
Rx: Receiver
SARPS: Standard And Recommended Practices
SBAS: Satellite-Based Augmentation System
SES: Single European Sky
SQM: Signal Quality Monitoring
SW: Software
Tx: Transmitter
VDB: VHF Data Broadcast
VHF: Very High Frequency
