**THE TWENTY-NINTH MEETING OF THE**

**INFORMAL PACIFIC ATC CO-ORDINATING GROUP**

**(IPACG/29)**

(Fukuoka, Japan, 27-31 October 2008)

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 data in this
analysis was collected after the modification of five reporting points
from non-compulsory to compulsory within the Anchorage FIR on 25 October
2007. This change has greatly assisted in locating longitudinally
proximate pairs in the data, which is a necessary component of the
safety assessment. The traffic data and the observed number of
longitudinal proximate aircraft pairs will continue to be evaluated 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.  Reference 3 describes the previous analysis in which there were 282
    eastbound and 596 westbound longitudinally proximate pairs observed
    in the Ocean21 data for the period March through August 2007. The
    observed eastbound proximate eastbound aircraft pairs were
    determined to be insufficient for use in this study because the only
    aircraft included were those utilizing ADS for position reporting.
    Aircraft utilizing HF radio for position reporting were not
    considered in reference 3 due to the absence of compulsory reporting
    points between the Fukuoka/Anchorage FIR boundary and the SYA radar
    coverage area..

5.  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 is in the
    Ocean21 data archives, is available and will aid the data collection
    process needed to complete the safety assessment for 10 minute
    longitudinal separation without MNT.

6.  Reference 4 describes an analysis performed after the modification
    of the five airspace fixes within the Anchorage Oceanic FIR from
    non-compulsory to compulsory reporting points. The addition of the
    compulsory reporting points increased the average number of
    longitudinally proximate pairs found in the data from 146 to 323
    pairs per month. The number of eastbound longitudinally proximate
    pairs is a key component in the completion of the safety assessment.
    There were 559 eastbound proximate pairs observed in the new data
    sample, however only 267 eastbound pairs were usable in the
    estimation of the longitudinal overlap probability. The pairs that
    contribute to the estimate of the longitudinal overlap probability
    are those that have a reduction in separation. The increase in the
    number of observed aircraft pairs reflects the addition of the
    compulsory reporting points in the airspace; this allowed the
    analysis to consider a longitudinal window of 30 minutes between
    aircraft operating on the same route and flight level.

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2.  **Updated Preliminary Data Analysis**

    1.  The Ocean21 data archives collected from the Anchorage FIR from
        November 2007 through August 2008 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.

    2.  From this data sample it was determined that there was on
        average 378 longitudinally proximate pairs in Anchorage Oceanic
        FIR each month. There were 1442 eastbound proximate pairs
        observed in this data sample, 702 of them could be used to
        determine the estimate of longitudinal overlap probability.

    3.  Figure 2 presents a histogram of the change in separation
        observed between eastbound aircraft pairs. The data needed to
        estimate the probability of longitudinal overlap are the
        aircraft pairs with an observed decrease in separation.

![](media/image2.wmf){width="5.996527777777778in"
height="4.090277777777778in"}

**Figure 2.** Change in Separation between Eastbound Proximate Pairs

4.  It was determined that additional data are required to properly
    estimate the probability of longitudinal overlap. 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 aircraft pairs.

**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.

3.  "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)",
    IP/4, IPACG/27, Tokyo, Japan, 5-9 November 2007.

4.  "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)",
    IP/8, IPACG/28, Las Vegas, Nevada, 14-16 May 2008.