TCAS Version 7 Data Collection

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TCAS Version 7 Data Collection


    From: Roy Grimes (Flight Technologies and Procedures Division, AFS-400)

     FAA Headquarters

Date: 9 March 2000

    Subject: TCAS II, Change 7 Modifications

ATTACHMENT. The 25 February edition of the TCAS Transition Program (TTP) Newsletter is attached

    to this cover letter. The Newsletter provides details on the Change 7 modifications to TCAS II.

BACKGROUND. The document entitled “TCAS II (Version 6.04) Operation in RVSM Airspace” was

    developed to inform pilots of Version 6.04 operating characteristics in RVSM airspace and to recommend

    aircraft operating practices to mitigate unnecessary RA events. Change 7 incorporates certain modifica-

    tions that enhance TCAS II operation in RVSM airspace (i.e., 1,000 ft vertical separation between FL 290-

    410). For some time to come, pilots will fly aircraft equipped with TCAS II incorporating Version 6.04 and

    other aircraft equipped with TCAS II incorporating Change 7.

RECOMMENDED OPERATING PRACTICES. The following aircraft operating practices recommended

    for RVSM operations with Version 6.04 should be continued when operating with Change 7:

a. TCAS should be operated in the TA/RA mode during all operations in RVSM airspace and

    Transition Areas.

b. Climb and descent rates in RVSM airspace and Transition areas should be limited to 1,000 fpm

    when operating within five (5) nm and 2,000 ft of other aircraft to minimize the generation of TAs

    and RAs.

REVISED TA AND RA ALERT THRESHOLDS. The following are the existing and re-

    vised alert thresholds that apply to operations at high altitude. The only changes in the

    thresholds are reductions in the altitude threshold for the issuance of TAs and RAs. The

    values that change between FL 300 and FL 420 are highlighted in the following table.

    Fixed Range Thre- Range Threshold Altitude Threshold

    shold Used with TCAS Advisory (Seconds) (Feet) Slow Closure Rates


    V6.04a V7 V6.04a V7 V6.04a V7 Traffic Advisory

    FL 200 FL 300 48 48 850 850 1.3 1.3

    FL 300 FL 420 48 48 1200 850 1.3 1.3 Corrective RA

    FL 200 FL 300 35 35 600 600 1.1 1.1

    FL 300 FL 420 35 35 700 600 1.1 1.1 Preventive RA

    FL 200 FL 300 35 35 700 700 1.1 1.1

    FL 300 FL 420 35 35 800 700 1.1 1.1


    ISSUE #V7-1 February 25, 2000

The TTP Newsletter is published and circulated to the aviation industry to provide periodic updates on the status of the TTP.

    TCAS Coordinators are encouraged to provide the widest possible dissemination of the information contained herein.

    The TTP introduced. Some airlines will also be carrying a li-

     mited number of TCAS data recorders supplied by the The TTP was established in 1991 to assess the per-William J. Hughes Technical Center (WJHTC) to col-formance of TCAS as it was introduced to comply with lect quantitative data on TCAS performance. the U.S. law requiring TCAS equipage. Because of the cooperation between pilots, controllers, airlines, To facilitate the data collection, new Pilot Question-industry organizations, and the FAA, the TTP has naires have been developed and are in the process of been very successful. The data that have been col-being distributed to operators. Controllers will contin-lected and analyzed have resulted in modifications to ue to use the existing Controller Questionnaire that the TCAS logic to address operational and technical that was updated and distributed in 1999 and should issues; enhancements to TCAS training programs; be available in their facility. The pilot and controller changes in operational procedures; and improved questionnaires can also be obtained from on the guidance on the use of TCAS in various airspace. ARINC web site at

    One of the premises that has made the TTP a suc- cess is the agreement by the FAA that information Organizations, individual pilots, and individual control-provided to the TTP regarding TCAS use and perfor-lers are strongly encouraged to renew their participa-mance could not be used to pursue enforcement ac-tion in the TTP to ensure that Version 7 provides its tion. These agreements continue to be in force and intended benefits. are expected to remain as new versions of TCAS are introduced. Version 7 Equipage

    During the past few months, TCAS suppliers have re-EUROCONTROL has issued a requirement for all air-ceived FAA certification of the latest revision to the craft with a MTOW greater than 15,000 Kg (33,000 TCAS software Version 7. Many of the changes lbs), or with more than 30 passenger seats, to be contained in Version 7 are largely the result of inputs equipped with Version 7 while operating in European received from pilots and controllers via the TTP ques-airspace. This includes both passenger and cargo tionnaires. aircraft. This requirement became effective on Janu-

     ary 1, 2000, but there is a transition period for equi-TCAS Version 7 Data Collection page that extends until March 31, 2001. EUROCON-

     TROL has established specific procedures for re-There have been no changes introduced to the TCAS questing exemptions to this requirement to allow software since the mid-1990’s, and the emphasis on equipage to take place during the transition period. collecting operational data on TCAS performance, as Other States, outside of Europe have also mandated well as the amount of data received during the past TCAS carriage, but none of these mandates will occur 18-24 months, has been significantly less than during during 2000. Details of these requirements can be the earlier years of TCAS operation. However, with found in the States’ AICs.

    the introduction of Version 7, there is a need to re- energize the TTP reporting and data collection pro-In the United States, there are no current plans to gram to increase the amount of operational perfor-mandate the upgrade to Version 7. mance data that is collected. During the remainder of 2000, ARINC will be collecting data from pilot and Because of the European mandate initial equipage controller questionnaires to verify that the changes with Version 7 will occur with aircraft operating in this contained in Version 7 are performing as intended and airspace. TTP data collection activities during 2000 to ensure that no new operational issues have been will initially focus on the international flights operated


    ISSUE #V7-1 February 25, 2000

    by the U.S. carriers. These activities will be comple-the arc for an RA requiring the pilot to maintain an ex-mented by similar activities conducted by EURO-isting vertical speed and for any RA that is modified CONTROL using inputs provided by operators based (weakened) when the response to the initial RA has in Europe. provided adequate vertical separation from the intrud-

     er. Whenever an RA is weakened, Version 7 will call In addition, the TTP will focus on identifying aircraft for the aircraft to be leveled by displaying the green being delivered with TCAS Version 7 and, as opera-arc beginning at 0 fpm and extending to ?250 fpm. tors begin to modify their domestic aircraft with Ver- sion 7, the TTP will seek to collect data from pilots Other Changes operating these aircraft as well.

     Horizontal Miss Distance Filter (HMDF). New logic

    Changes in TCAS with Version 7 has been included with Version 7 that will recognize

     encounters with adequate horizontal separation be-The objectives of the Version 7 changes were to fur-tween aircraft, and whenever possible, suppress an ther increase the safety benefits of TCAS; make RA. Simulations and testing have shown that the TCAS more compatible with the procedures used by HMDF will reduce the number of RAs by approximate-ATC; and to address operational concerns identified ly 25% in U.S. airspace, and up to 40% of RAs in Eu-by pilots operating the existing versions of TCAS. ropean airspace.

Some of the changes will be obvious to pilots, while RA Reversals. Version 7 will allow TCAS to reverse

    others will either be difficult to detect or transparent. an RA, e.g., change a CLIMB RA to a DESCEND RA, The most obvious changes from the flight deck pers-in a coordinated encounter with another TCAS aircraft. pective are changes in the aural annunications and on the RA display. Controllers should notice some re-Intruder Surveillance. There have been numerous

    ductions in the number of RAs issued and reductions improvements to the intruder surveillance functions to in altitude displacements when aircraft respond to provide more reliable tracking of intruders and to en-RAs. The following sections provide an overview of sure that TCAS meets its design guidelines for opera-the changes to the aural annunciations and the RA tion with ground radars. This will result in aircraft be-display, and outline other Version 7 features. ing more reliably tracked, and thus displayed, at long-

     er ranges in high-density traffic areas. New Aural Annunciations

     RVSM Compatibility Issues. The TA thresholds be-

    The aural annunciations used by TCAS when an RA tween FL300 and FL420 have been reduced to elimi-is issued have been modified to provide additional in-nate nuisance TAs while operating in RVSM airspace. formation about the desired response shown on the RA display. These changes, coupled with changes in Aural Inhibit Altitude. The aural inhibit altitude has

    the RA display, should make the desired response to been returned to 500 feet AGL to increase the aware-an RA more intuitive. A table comparing the existing ness of TAs issued while on approach. and modified aurals is provided at the end of this Newsletter. The shaded areas indicate those aural “Bump-up” Encounters. Version 7 contains software

    annunciations that have been modified. that recognizes encounters between 10,000 feet and

     FL 300 where an aircraft is climbing or descending to RA Display Changes level off 1,000 feet away from the TCAS aircraft and

     slightly delays the issuance of an RA. Changes to the RA display and portions of the TCAS logic were developed to help reduce altitude excur-Altitude Crossing RAs. Version 7 contains additional

    sions during an RA, and to provide pilots with conti-biases to reduce the frequency of altitude crossing nuous guidance throughout an RA by expanded use RAs. of the green “fly-to” arc. Currently, TCAS will display a green arc only for an initial RA requiring a change in Good Operating Practices

    vertical speed (e.g., Climb or Descend RA); a sec- ondary RA requiring a stronger RA response (e.g., Past experience in the TTP has shown that the use of Increase Climb/Descent RA); or an RA reversal (e.g., the following procedures or techniques will minimize 4 Climb/Descend NOW). Version 7 retains the use of any impacts of TCAS operation on the flight crew, the the green “fly-to” arc for these advisories. It also uses controller, or the airspace environment.


    ISSUE #V7-1 February 25, 2000

     questions regarding the traffic in the vicinity of an air-

    Do not place TCAS in TA Only or TA/RA until just craft.

    prior to taking the runway for departure. On landing,

    place TCAS in Standby as soon as workload permits TTP Contacts

    after clearing the active runway.

     Questions concerning the information in this Newslet-

    If an initial RA is weakened (for example, a Climb RA ter, Version 7, or other TCAS operational information

    weakens to a Do Not Descend RA), pilots should re-can be addressed to the following individuals:

    spond to the weakening RA and adjust the aircraft's

    vertical speed accordingly but still keep the needle or ARINC

    pitch guidance symbol out of the red arc or outlined Sean Reilly (410) 266-2904

    pitch avoidance area. With Version 7, the green arc or will remain displayed for the weakened RA to provide Rick Stead (410) 266-4852

    a target vertical speed for the modified RA. Pilots are or

    reminded that attention to the RA display and prompt Dan Tillotson (215) 493-8016

    reaction to the weakened RA will minimize altitude or

    excursions and potential disruptions to ATC.


    Communications regarding TCAS events and dis-Larry Nivert/AND-520

    played information should be limited to that required to (202) 493-4708

    inform the controller that an aircraft is responding to

    an RA. Discretion should be used in using the infor-

    mation provided via the TCAS traffic display to ask

    TCAS Advisory Version 7 Aural Annunciation Existing Aural Annunciation Traffic Advisory Traffic, Traffic Traffic, Traffic Climb RA Climb, Climb Climb, Climb, Climb Descend RA Descend, Descend Descend, Descend, Descend Altitude Crossing Climb RA Climb, Crossing Climb; Climb, Crossing Climb, Crossing Climb; Climb, Crossing

    Climb Climb Altitude Crossing Descend RA Descend, Crossing Descend; Descend, Descend, Crossing Descend; Descend,

    Crossing Descend Crossing Descend Reduce Climb RA Adjust Vertical Speed, Adjust Reduce Climb, Reduce Climb Reduce Descent RA Adjust Vertical Speed, Adjust Reduce Descent, Reduce Descent RA Reversal to a Climb RA Climb, Climb, NOW; Climb, Climb Climb, Climb, NOW; Climb, Climb NOW


    RA Reversal to a Descend RA Descend, Descend NOW; Descend, Des-Descend, Descend NOW; Descend, Descend

    cend NOW NOW Increase Climb RA Increase Climb, Increase Climb Increase Climb, Increase Climb Increase Descent RA Increase Descent, Increase Descent Increase Descent, Increase Descent Maintain Rate RA Maintain Vertical Speed, Maintain Monitor Vertical Speed Altitude Crossing, Maintain Maintain Vertical Speed, Crossing Main-Monitor Vertical Speed Rate RA (Climb and Descend) tain

    Weakening of Initial RA Adjust Vertical Speed, Adjust Monitor Vertical Speed Preventive RA (No change in Monitor Vertical Speed Monitor Vertical Speed, Monitor Vertical vertical speed required) Speed RA Removed Clear of Conflict Clear of Conflict


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