### The Twentieth Meeting of the Informal South Pacific ATS Coordinating Group![](media/image1.jpeg){width="1.3291666666666666in" height="0.7368055555555556in"}

**(ISPACG/20)**

Honolulu, USA, 30 January -- 1 February 2006

Agenda Item 4: AI 17-5 ADS-B Implementation

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###### Airways New Zealand ADS-B Technical Trial

(Presented by Airways New Zealand)

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| # SUMMARY                                                             |
|                                                                       |
| The following paper and associated presentation summarises New        |
| Zealand's experience in conducting an ADS-B trial at Christchurch.    |
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1\. **INTRODUCTION**

1.  The Eleventh ICAO Air Navigation Planning Conference recommended
    that States recognize ADS-B as an enabler of the global ATM concept
    bringing substantial safety and capacity benefits; support the
    cost-effective early implementation of it; and ensure that it is
    harmonized, compatible and interoperable with operational
    procedures, data linking and ATM applications.

2.  Several trials have been conducted by different manufacturers at
    sites in Australia, the U.K., the U.S.A., France, Singapore and a
    few other locations. Data from these trials has given a good
    indication of the system performance that Airways can expect.

3.  Both Australia and the FAA have taken the next step of operational
    deployment and use of ADS-B. Airways has been fortunate to be
    included in the Australian ADS-B Implementation team meetings which
    share quality information about all issues associated with the
    ground and avionics technology development.

**2. DISCUSSION**

1.  Thales ATM, a well known supplier of air navigation systems and
    related equipment, agreed to make a Mode S ADS-B Ground Station
    model (AS680) available to Airways on a temporary basis for a three
    month evaluation. The supply included equipment installation,
    commissioning, and training for selected Airways staff.

2.  The key benefits from this trial are focused around the achievement
    of first hand knowledge and skill - particularly in showing a full
    understanding of the issues, costs, resources, and work packages
    required for Airways to be able to deploy and use ADS-B
    operationally. This will support future decision making on how and
    when such use is appropriate.

3.  The ADS-B RCMS workstation with two screens was installed in a
    separate ATM system Lab, and provided remote control and monitoring
    of the ground station, and a real time air situation display for
    ADS-B traffic. Located alongside the RCMS, was the single box
    (processor) ATM system. This ATM system was also connected to the
    normal Lab provisions of live radar and flight plan data, allowing
    comparison between radar and ADS-B and identification of flights.

4.  Data analysis used a combination of regular monitoring of the RCMS
    displays, and statistical analysis of the ground station data logs
    using software custom written by the project engineers. Airways
    proprietary Plotting Tool was also interfaced to the ADS-B system to
    allow map presentation of ADS-B data.

**Coverage**

5.  Actual coverage observed correlated closely with the theoretical
    chart. The most distant target observed was an A345 operated by
    LanChile, observed flying at FL360, 373nm to the northeast. In this
    direction the propagation path was unobstructed by terrain.

6.  ADS-B communications are affected by antenna shielding as for MSSR
    surveillance. No examples of aircraft attitude induced drop-outs
    were observed for RPT aircraft, possibly due to the low altitude
    near-airport location of the receiver, in conjunction with the dual
    antenna installations on these aircraft.

7.  Loss of surveillance due to antenna shielding was observed on the
    flight test aircraft during manoeuvres at range. Because some data
    items in the ADS-B data set are transmitted less often than others,
    extended dropouts can cause odd anomalies. In one case, the velocity
    vector reported by the ground station on the first report after the
    dropout had out of date values for heading.

**Comparison with Calibration Flight Data**

8.  Conveniently, the ADS-B trial system was in service at the time of
    the flight test of the new Cass Peak Mode-S SSR radar. This radar
    operates in the same coverage area as the ADS-B ground station, so
    the opportunity was taken to flight test the ADS-B system.

9.  Data for the calibration flight from the GPS log and from the ADS-B
    system were plotted and compared, with the following results.

10. In straight constant speed flight, the track position of ADS-B and
    Calflight equipment coincide with no significant lateral or
    longitudinal offset.

11. In turning flight, the ADS-B data exhibited classical tracker lag,
    with position reports placing the aircraft outside the actual turn
    performed. The size of the offset to the outside of the turn
    increased with increasing turn rate. The smoothing was strongly
    damped with a relatively lengthy time (15 seconds) taken to converge
    with the straight flight path at the end of a turn.

12. The source of the position offsets is not clear. Because the error
    is dynamic (only occurs with lateral acceleration), the source is
    likely to be either the dynamics of moving position determination in
    the GPS receiver, or a processing step in the chain which
    time-corrects position data to accommodate processing latency.
    Except for the time taken to re-converge with straight flight, the
    error is consistent with straight line projection of the aircraft
    position forward in time along the instantaneous velocity vector.

**Comparison with Radar Data**

13. A holding pattern was flown 60nm distant from the radar under test.
    On the comparison plot, the most significant position anomalies
    shown are a combination of azimuth noise and tracker lag. The effect
    is most clearly shown on the standard turn (largest radius outside
    turn) in which the radar takes one scan to identify the commencement
    of a turn and two more scans for the Kalman filter tracker to
    establish the turn radius and correctly track the aircraft.

14. In conjunction with 25ft steps in altitude reports, increasing the
    reporting rate from aircraft has the potential to improve tracking
    in multi-sensor surveillance areas, allowing superior performance in
    automation safety net applications (short term conflict alert,
    minimum safe altitude warning, danger/restricted area intrusion
    warning) during maneuvering flight, and possibly the further
    reduction of separation standards in well assessed circumstances. At
    present, ADS-B applications in practice are focusing on en-route
    coverage extension with conservative separation standards befitting
    an emerging technology.

**Proportion of Fleet Equipage**

15. Air New Zealand (ANZ) and Freedom (SJ) A320s are providing ADS-B.
    These aircraft all fly International routes. Some Pacific Blue B738s
    are providing ADS-B. Only one other aircraft on the NZ Register
    (ZKVAA) is seen. Other flights seen in New Zealand providing 1090ES
    ADS-B are Emirates (UAE) A345 aircraft (all), some Singapore
    Airlines B773s and one SIA B772.

16. The ADS-B Trial observed flights from Christchurch, Wellington and
    Dunedin. Scheduled International flights also operate from Auckland,
    Hamilton and Palmerston North Airports. In addition to the flights
    observed from Christchurch, Auckland have regular Aerolineas
    Argentina, Korean, Malaysian, Thai International, Air Tahiti,
    Garuda, Eva, Air Pacific, Lan Chile, Air Vanuatu, DHL freight and
    Lufthansa freight and others. It is not known what ADS-B capability
    each of these operators has.

17. It is estimated that approximately 0.5% of domestic movements at
    Christchurch, Wellington and Dunedin are currently ADS-B equipped
    and 36% of the international movements.

**Anomalies**

18. Two issues that require further investigation were uncovered;
    longitudinal fault (applied to one airframe only) and position
    quantization (applied to one aircraft type).

19. The longitudinal fault applied intermittently to one particularly
    aircraft, and gave spurious longitude positions for varying lengths
    of time. The reasons for the fault are not yet known.

20. Position quantization applied to A345 aircraft whereby the reported
    positions fell within a lattice with step distances of approximately
    1/32 nm. This problem has been filed as a PR, and would require
    rectification before going operational with this system.

**Conclusions**

Airspace coverage was as predicted.

The New Zealand avionics fitment is lower than expected -- about 0.5% of
the total fleet.

No domestic RPT aircraft flying domestic routes are equipped.

Unsolved problems with Emirates A345 and Pacific Blue B738s indicate
that there are still some issues to solve for this to be the primary
surveillance tool.

The lack of ADS-B avionics and the upgrading of all NZ radars combined
are enough to make an early introduction of sole means ADS-B very hard
to justify.

Further trialing of the equipment at the existing or another NZ site
will not provide value to the extent that is worthwhile to purchase the
trial equipment.

ADS-B combined with Multilateration is a very different solution, and a
trial of that combination of technologies has been approved.

For International traffic ADS-B may be useful for busy tracks about the
domestic boundary, or at strategic sites in the Pacific.

For Domestic traffic ADS-B surveillance, a re-evaluation should be made
at the midlife of SSRs.

**3. RECOMMENDATION**

1.  The meeting is invited to:

note the experiences of Airways New Zealand in conducting ADS-B trials