### 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 2: AI

###### 

###### Mode-S SSR Upgrade

(Presented by Airways New Zealand)

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| # SUMMARY                                                             |
|                                                                       |
| New Zealand is in the middle of a radar modernisation program to      |
| extend the life of our current SSR and PSRs, a total of 6 SSRs and 3  |
| PSR radars are being replaced. This work involves all the SSRs being  |
| upgraded to mode S capability.                                        |
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1\. **INTRODUCTION**

1.  The radar modernisation program began at the start of 2005 and will
    finish in the last half of 2006. The SSR radars are being replaced
    by Thales with RSM 970S Mode S.

2.  Full commissioning has been undertaken for one SSR site, another two
    SSRs have undergone Site Acceptance Testing (SAT) and one PSR has
    undergone SAT.

**2. DISCUSSION**

1.  The program has not gone without a few hitches, most of which can be
    put down to the enhanced discretion the new radars exhibit, both in
    terms of accuracy and performance.

2.  For instance, we had a number of problems with target dropouts or
    garbling. These generally fell into one of 3 categories:

    -   Non-compliant transponders

    -   Faulty transponders

    -   Unusual cases

3.  The first of these we discovered were transponders that were not
    compliant with the latest specifications (mode S), and to which
    various airworthiness directives (ADs) were in force. These
    non-compliant transponders showed up on the old radar, but not the
    new one and more than likely will not show up on TCAS either.

4.  The second case was transponders that while being compliant had
    faults, eg in power output, which exhibited garbling and drop outs
    on the new radar.

5.  The third problem was particular to a B737 airframe, where the
    captain's transponder would not show up on the new radar. Despite
    ramp and bench checks of the transponder out of the aircraft, no
    problems showed up. Eventually a cable that connected to a relay was
    replaced and the problem went away.

6.  These problems slowed progress on the actual tuning of the radars
    and masked other fault finding and testing procedures. We now have
    processes in place to quickly identify where problems relate to one
    of these three areas, and they can be dealt with effectively.

7.  Right at the start of this program we made a decision to minimize
    the operational impact of the upgrade. To do this testing was done
    in the simulator with sector controllers, noting the effects of
    withdrawing specific radars from the network. The controllers
    therefore gained confidence in their ability to manage traffic in a
    reduced radar coverage environment.

8.  Additionally we made a decision to move the existing radars within
    the buildings they were housed in and install the new radars in
    their place. This had the benefit of enabling us to cut over from
    old to new or back again within a 20min period.

9.  While the new radars are operating in mode S, the ATM system will
    not be adapted to accept mode S inputs until the upgrade program is
    complete.

**Conclusions**

10. Do not expect an upgrade to mode S SSR to be a simple matter; you
    will uncover a lot of issues.

11. Be careful not to put operational controllers in front of a radar
    screen, for testing, unless you are confident of the results. Your
    operational controller does not care that the reason why a target
    garbles is because it has a faulty transponder, he just doesn't want
    it to garble.

12. Look at ways to minimize the operational impact of upgrading radars.
    One of your customers is the controller and he wants the process to
    be as painless as possible.

**3. RECOMMENDATION**

1.  The meeting is invited to:

> note the experiences of Airways New Zealand in replacing its current
> radar system and introducing mode S.