**THE TWENTY-SEVENTH MEETING OF THE**

**INFORMAL PACIFIC ATC CO-ORDINATING GROUP**

**(IPACG/27)**

(Tokyo, Japan, 5-9 November, 2007)

Agenda Item 5: Air Traffic Management (ATM) Issues

**Update on the Status of the Operational Trials and Demonstrations for
10 Minute Longitudinal Separation without Mandatory Mach Number
Technique (MNT) in the Anchorage Flight Information Region (FIR)**

(Presented by the Federal Aviation Administration)

[Summary]{.underline}

This paper provides an update of the data collection required to
complete a safety assessment for the 10-minute longitudinal separation
without Mach Number Technique (MNT) operational trial being conducted
within the Anchorage FIR. An updated preliminary analysis on observed
longitudinally proximate pairs of aircraft is provided. The modification
of five reporting points from non-compulsory to compulsory within the
Anchorage FIR on 25 October 2007 should greatly assist the data
collection needed for the safety assessment. The traffic data and the
observed number of longitudinal proximate aircraft pairs will be
evaluated from 25 October 2007 forward to determine the full extent of
the operational trial needed to complete the safety analysis.

**1. Introduction**

1.  The operational trial for the use of 10 minute longitudinal
    separation without Mach Number Technique (MNT) within Anchorage
    Flight Information Region (FIR) began on 12 April 2007. The purpose
    of the operational trial is to obtain data for analysis and to
    acquaint controllers with the operational aspects of its
    application. A similar operational trial in the adjacent Oakland FIR
    was initiated in September 1998. Reference 1 contains the analysis
    conducted to support the operational trial in the Oakland FIR.

2.  The application of the 10 minute longitudinal separation without the
    use of MNT applies only to eastbound turbojet aircraft operating at
    or above FL290. The 10 minute longitudinal separation without the
    use of MNT can be applied to these aircraft upon entry into the
    Anchorage FIR and is applicable until either the aircraft is under
    radar coverage or exits Anchorage oceanic airspace.

3.  This paper provides an update on the data sources to be used in the
    implementation of the 10 minute longitudinal separation without MNT
    within the Anchorage FIR. It also provides an update to the
    preliminary analysis on observed longitudinally proximate pairs of
    aircraft.

**2. Discussion**

1.  Reference 2 provides a description on the data collection process.
    Position data from all aircraft operating in the Anchorage oceanic
    FIR are obtained from the Ocean21 data reduction archives.

    1.  On 1 March 2007, the Ocean21 system was introduced in the
        Anchorage FIR in oceanic sectors 10 and 11. Figure 1 illustrates
        the location of these sectors within the Anchorage FIR.

![](media/image1.wmf){width="5.360416666666667in"
height="2.522222222222222in"}

**Figure 1.** Location of Anchorage Oceanic Sectors 10 and 11

2.  The process described in reference 2 specified that all available
    positions (latitude, longitude (or fix) and flight level and
    associated times of all aircraft regardless of reporting method
    (High Frequency (HF), Controller-Pilot Data Link Communication
    (CPDLC), or Automatic Dependent Surveillance (ADS)) in the sectors
    of interest would be collected.

3.  Reference 2 presented a preliminary data analysis using a 16-day
    sample from the Anchorage FIR. Only 31 longitudinally proximate
    aircraft pairs were found in this analysis. This number was
    considerably lower than expected. All of the aircraft pairs found
    had reported their position via ADS-Contract (ADS-C). The data
    processing for proximate aircraft pairings did not identify any
    aircraft that utilized HF or CPDLC for position reporting. This
    preliminary analysis and result revealed the lack of electronic
    position report data in the Ocean21 data archives from aircraft
    using HF or CPDLC to report position. There were no compulsory
    reporting points in the airspace for aircraft operating between the
    Fukuoka FIR boundary and the extent of the Shemya (SYA) radar
    coverage.

4.  On 25 October 2007, the FAA modified five airspace fixes within the
    Anchorage oceanic FIR from non-compulsory to compulsory reporting
    points. These fixes include: AAMYY, CARTO, NIKLL, OPAKE, and PLADO.
    With this modification, position data from aircraft utilizing HF and
    CPDLC for position reporting not available previously in the Ocean21
    data archives, will be available and should greatly aid the data
    collection process needed to complete the safety assessment for 10
    minute longitudinal separation without MNT.

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2.  Updated Preliminary Data Analysis

    1.  The start of the operational trial was 12 April 2007. In order
        to complete a safety assessment to support the implementation of
        the 10 minute longitudinal separation without the use of MNT, a
        sufficient number of proximate aircraft pairs must be observed.
        Paragraph 2.1.3 mentions that the initial preliminary data
        analysis presented in reference 2 revealed a considerably lower
        number of longitudinal proximate pairs than were expected. The
        cause of this result is the lack of compulsory reporting points
        between the Fukuoka FIR boundary and the extent of the SYA radar
        coverage. This situation is expected to change on 25 October
        2007 with the addition of five compulsory reporting points in
        the Anchorage oceanic airspace.

    2.  Due to the known lack of position data available in the Ocean21
        data archives for aircraft utilizing HF or CPDLC for position
        reporting, this updated preliminary analysis is not specific to
        the 10 minute longitudinal separation without MNT. It is
        anticipated that data collected from 25 October 2007 onward will
        be used in the safety assessment of the 10 minute longitudinal
        separation without MNT in the Anchorage oceanic FIR.

    3.  The Ocean21 data archives collected from the Anchorage FIR from
        March through August 2007 were analyzed for this updated
        preliminary analysis. From the aircraft filed flight plan data,
        it is estimated that an average of 440 flights per day operate
        within the Anchorage FIR. Twenty-two percent of these flights,
        or approximately 97 flights per day, utilize ADS for position
        reporting. The remaining 78 percent, or approximately 343
        flights per day, utilize HF or CPDLC for position reporting.

    4.  There were 282 eastbound and 596 westbound longitudinally
        proximate pairs observed in the data. In each observed aircraft
        pair, both of the aircraft utilized ADS for position reporting.

    5.  It is desirable to include all potential aircraft pairs in the
        safety assessment for the 10 minute longitudinal separation
        without MNT in the Anchorage oceanic FIR, not just aircraft
        utilizing ADS for position reporting. Doing so ensures that all
        potential scenarios, including those arising from large
        prediction errors or large message transit times are taken into
        account in the safety assessment.

    6.  The length of time needed to collect a sufficient number of
        proximate aircraft pairs depends on the data, specifically, the
        number of observed eastbound proximate eastbound aircraft pairs.
        The traffic data and the observed number of proximate eastbound
        pairs will be evaluated from 25 October 2007 forward to
        determine the full extent of the operational trial required to
        complete the safety analysis.

**3. Recommendation**

3.1 The meeting is invited to note the information provided in this
paper.

**[References]{.underline}**

1.  "Status of Operational Trials and Demonstrations for 10 Minutes
    Longitudinal Separation Without mandatory MNT in the Oakland FIR",
    IP/3, Review of the General Concept of Separation Panel (RGCSP),
    Working Group A Meeting, St. Petersburg, 17-28 May 1999.

2.  "Status of the Operational Trials and Demonstrations for 10 Minute
    Longitudinal Separation Without Mandatory Mach Number Technique
    (MNT) in the Anchorage Flight Information Region (FIR)", IP/9,
    IPACG/26, Anchorage, Alaska, 14-18 May 2007.

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