Future Air Navigation (long)

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Date:         17 Mar 95 12:58:03 
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                              FANS 1 UPDATE FOR 747-400
                                     DAVID ALLEN
            INTRODUCTION
            Based  on  the  FANS  concept   of  a  phased  approach   to
            implementation, Boeing and its  customer airlines have  been
            working with civil aviation administrations to develop FANS-
            1, a system upgrade for the 747-400 that is compatible  with
            present and future  upgrade plans  of the  Boeing family  of
            aircraft.    FANS-1  complements  the  International   Civil
            Aviation Organization's  (ICAO)  Global  Plan  and  regional
            planning activity going  on in several  parts of the  world.
            This report  will concentrate  on  the development  of  FANS
            capability for the 747 -400 (which will be  the first Boeing
            airplane to have an integrated FANS solution installed).

            Before plunging into the details of the FANS  implementation
            on the 747-400, it is necessary  to review the ground  rules
            associated with the creation of the functional baseline:

                 1. Implementation  of  FANS  capability   must  proceed
                    incrementally, with  benefits  outweighing  cost  at
                    each step
                 2. Implementation  of   functions  must   consider  all
                    requirements necessary  to achieve  maximum benefits
                    (ground and airborne)
                 3. Maximum utilization  of existing  equipment, minimum
                    installation of new equipment
                 4. Integrity issues  must be  addressed  at the  system
                    level
                 5. The 747-400 system  upgrade must be  consistent with
                    plans for other Boeing aircraft

            Clearly FANS cannot be implemented in  a single step.   But,
            at some point,  manufacturers and  airlines have  to take  a
            first step or FANS will never be  implemented.  For Boeing,
            FANS-1 is that first step.

            At its September-October 1993 meeting in Montreal, the  FANS
            Committee recognized  the  operators'  needs  for  a  timely
            return on investments and  ``encouraged States and  aircraft
            operators to implement communication system protocols  based
            on the  ARINC  Specification  622 in  order  to  gain  early
            benefits.''  Just as ARINC 622 provides a transition  to the
            Aeronautical Telecommunications  Network  (ATN)    --    the
            ultimate communications system envisioned by ICAO  --   GPS,
            with or without augmentation,  provides a transition to  the
            ultimate ICAO  Global  Navigation Satellite  System  (GNSS).
            Adding GPS  and  ARINC  622 compatible  equipment  with  ATN
            compatible  applications    guarantees  compatibility   with
            tomorrow's FANS equipment.  FANS-1 will provide the airlines
            with significant benefits  for the extended  period of  time
            required  for  the  ultimate  FANs  environment  to   become
            reality.

            OPERATIONAL BENEFITS
            In working with the airlines, it  was apparent that a  first
            and practical step in the FANS evolution could be  improving
            en-route operations in  non-radar surveillance  areas.   The
            South Pacific region is a good example of that  environment,
            but most  of  these benefits  are  applicable to  all  other
            regions  (exception  might  be  Dynamic  Re-routing).    The
            targeted operational benefits are:

                 1. Reduced lateral and longitudinal separations
                 2. Dispatch on  Required  Navigation Performance  (RNP)
                    routes
                 3. Flexible Tracks on existing organized track systems
                 4. Dynamic Re-routing
                 5. Improved response  for  altitude  and  route  change
                    requests
                 6. Avoidance of altitude loss for crossing tracks
                 7. Non Precision GPS RNAV approaches to MDA
                 8. Improved availability of alternate airports

            The 747-400 FANS-1 CNS performance and integrity levels will
            be documented  and certified  so they  may  be used  by  the
            airlines in support of Operational Specification changes  to
            support the above benefits.

            Reduced Lateral and Longitudinal Separations
            The current aircraft separation  utilizes the lowest  common
            navigation capability to  determine the airspace  separation
            requirements and  is  predicated  on  traditional  means  of
            navigation,  communication,   and  surveillance.   Potential
            errors  in  voice  communication   between  the  pilot   and
            controller  are  considered  in  determining  the   airspace
            separation requirement (especially  in the HF  environment).
            Digital communication between the  crew (using the  airborne
            ATC DL * function)  and the  controller drastically  reduces
            that error source.
                                
            * Also known as Controller Pilot Data Link Communications
               (CPDLC) and Two-Way ATC Data Link (TWDL)

            The potential for pilot entry errors must also be considered
            in this determination.   Currently, it sometimes takes 20 to
            45 minutes  to  make  High  Frequency  (HF)  voice  position
            reports.   The  uncertainties associated with error  sources
            from navigation, pilot entry error, communication  problems,
            and  traditional  voice   position  reporting   surveillance
            requires  the  Air   Traffic  Controller   to  "reserve"   a
            tremendous amount  of  airspace  for  each  aircraft.    The
            typical Air  Traffic  System  (100  nm  lateral  by  120  nm
            longitudinally) requires 48,000 square miles of airspace  to
            protect a single aircraft.     This translates to  operating
            penalties for  the  airlines  in terms  of  lower  operating
            altitudes and fixed speeds.

            While it  might  be  possible  to  gain  minimal  separation
            benefits from an improvement in a single area (ADS reporting
            for  example),   full   benefits   require   an   integrated
            improvement in the CNS suite:

                 1. Communication
                      Improved response time (for intervention)
                      Reduction in communication errors
                 2. Navigation
                      Improved navigational accuracy
                 3. Reduction in entry errors
                 4. Surveillance
                      Increased frequency of position reporting

            Inclusion of intent information to position report
            HF relayed voice communication can have a significant delay.
            ATC Data Link communications will require a fraction of  the
            transmission time  and  they  are much  less  likely  to  be
            misunderstood.   GNSS integration will provide the  airplane
            with significantly greater navigational accuracy.  The  data
            linking and loading  (into the  FMC) of  ATC clearances  and
            routing will greatly reduce the probability of entry errors.
            FANs equipped airplanes  have the ability  to transmit,  via
            satellite data link, automatic dependent surveillance  (ADS)
            reports (actual position  and intent information)  nominally
            every 5 minutes or at a  rate selected by the ATC  authority
            down to 64 seconds.   This position will  not only have  the
            benefits of GNSS accuracy, but will also have the benefit of
            a synchronized clock with the controller (via GNSS Universal
            Time Constant).

            This  combination  of   improvements  (using  systems   with
            appropriate  integrity  and  cockpit  alerting)  allow   the
            authorities   to   reduce   mandatory   separation   between
            airplanes, therefore allowing more airplanes to fly at their
            optimum altitude (reducing fuel burn).   Industry is working
            with the national administrations  and relevant ICAO  panels
            to implement such  procedure changes  right now.   The  FANS
            Committee  estimated  communications   cost  for  each   ADS
            position report would  be somewhere between  50 cents and  a
            dollar.  The authorities are considering the  implementation
            of a  preferred track  system  which will  give preferential
            tracks to  FANS equipped  airplanes.   While there  will  be
            transitional improvements in separations based on experience
            and ground base equipage, it is anticipated that full ground
            implementation will  give a  FANS 1  aircraft 30  nm  radius
            protection  (2,827   square  miles)   which  is   a   1,690%
            improvement over today's system.

            Dispatch on Required Navigation Performance (RNP) Routes
            Many of the  regional ATC  planning groups  are planning  to
            establish preferred routes for airplanes which can guarantee
            a certain RNP.  The FANS  1 implementation supports a  full,
            integrated  compliance  to  the   RNP  concept  with   pilot
            alerting, automatic  "phase  of flight"  default  RNPs,  and
            pilot entry RNPs.  With GPS combined with IRS, the  airplane
            performance will be capable of operating in the planned  RNP
            environments.

            Flexible Tracks on Existing Organized Track System
            Flexible tracks  are  currently  used in  areas  with  lower
            traffic density  which allow  the  airlines to  fly  optimum
            routes using seasonal  winds.  This  gives a more  efficient
            route than the fixed track system.  The capabilities of  the
            FANS 1  aircraft which  allow reduced  separation will  also
            support the implementation of additional flexible tracks for
            equipped airplanes.

            This allows  an  optimized  flight  plan  using  the  latest
            weather data to be  sent via satellite data  link to an  en-
            route aircraft.  One  way this could  be implemented is  for
            the airline flight planning office to send the new optimized
            flight plan  via company  data link  to the  aircraft.   The
            aircraft could then data link that new route as a  clearance
            request to Air  Traffic Control (ATC),  receive a  clearance
            from the ATC controller via data link, then load and fly the
            new route.  Another  way would be for  the ATC authority  to
            compute the optimum flight plan  (a new flexible track)  and
            send it to the  airplane using the  ATC Data link  function.
            By flying the  optimized flight plan,  fuel burn and  flight
            time could be reduced.   Real and  tangible benefits to  the
            operator could result.

            Improved Response Time for Altitude Change Requests
            In the HF radio communication environment, it can take up to
            20-60 minutes to get a clearance  for a step climb to a  new
            optimum altitude.  Satellite  communication can reduce  that
            response time  to minutes.   Operating  at optimum  altitude
            reduces fuel burn.

            Avoidance of Altitude Loss for Crossing Tracks
            Airplanes which are approaching crossing tracks are required
            to be separated  by altitude  (meaning one  airplane can  be
            forced to  operate  as  much  as  4000  feet  below  optimum
            altitude).  If  the ATC controller  had timely  surveillance
            data and  the  airplane  has  the  ability  to  control  the
            airplane speed such that it crosses the way point at a given
            time, then this altitude separation would not be necessary.

            Non-precision GPS RNAV Terminal Area Procedures to MDA
            The FANS 1 GPS implementation will support GPS terminal area
            non-precision approaches down to MDA when Receiver
            Autonomous Integrity Monitor (RAIM) is available (dependent
            on constellation).  Ground based predictive RAIM can be used
            to provide this assurance.

            Improved Availability of Alternate Airports
            One of the considerations associated with routing is the
            availability of alternate airports.  GPS/FMS approach
            procedures are evolving, but will allow operations into
            airports which are normally not available to airlines (due
            to lack of precision approach availability. Since, the FANS
            1 FMC will be certified to allow GPS only non-precision
            approaches to Minimum Decision Altitude allowing more
            airports to be considered as alternates (with regulatory
            approval).  Additional alternate airports and increased
            terminal capability at the destination airport can
            modification of routing to reduce fuel carriage.
            
	    Such procedure changes would be achievable with FANS-1 and
            improved ground infrastructure.  In practice more airplanes
            could fly at their optimum altitude and fly closer to
            optimum track; fuel burn and flight time could be reduced,
            the cost of carrying excess or contingency fuel reserves
            could be reduced, and payloads increased.  In short; FANS-1
            enables operators to increase revenues and reduce
            operational costs.  Such operational improvements are also
            good for the environment.  They are also good for the
            national economies: they increase the air transportation
            system capacity.

            747-400 FANS 1 FMCS FUNCTIONS
            The  following  airplane  Flight  Management  functions  are
            required to support an  initial FANS implementation.   These
            functions are referred to as FANS 1:

                 1. Automatic Dependent Surveillance (ADS)
                 2. ATC Data Link (ATC DL)
                 3. Company Data Link
                 4. Global Positioning Satellite (GPS) Integration
                 5. Required Time of Arrival

            Company Data Link,  ADS and ATC  DL will  use the  currently
            defined and operational  data network  utilized by  airlines
            today (ie  ACARS/Satcom using  ARINC 622  protocols).   This
            network  will  link  the  airplane,  ground,  and  satellite
            environments.

            FANS-1 will give Airline Data Systems the capability to data
            link new  routes, position  reports, and  updated winds  via
            this network.   The  ADS function  will report  the  current
            Flight  Management  Computer  System  (FMCS)  position  (GPS
            corrected) via  satellite  or  VHF  data  link  to  the  ATC
            controller.  This report will not  only give the actual  GPS
            reported position, but the report will also be referenced to
            the GPS time  standard and contain  information relating  to
            the current   intent.   This will  considerably improve  the
            surveillance of  enroute  airplanes.    The  ATC  Data  Link
            function will replace the tactical communication between the
            crew and the ATC controller.  The crew will have the ability
            to  request  deviations  to  the  filed  flight  plan  (even
            replacements of the filed flight plan).  The ATC  controller
            will also  have the  ability  to directly  request  tactical
            changes  to  the  airplane  flight  path.    The  integrated
            solution includes an aural and  visual alert of an  uplinked
            ATC message.

            GPS integration requires  the installation  of sensor  units
            and antennas.   The GPS position  and integrity  information
            will be  sent directly  to  the Flight  Management  Computer
            System (FMCS).    The  FMCS will  use  the  sensor/satellite
            determined integrity monitor and other navigational  sensors
            (IRS, DME/DME) to determine the validity of the GPS position
            solution and, whenever possible, the GPS will continue to be
            used as the prime sensor.

            This GPS improvement provides  a more accurate position  for
            enroute operations  and, as  a minimum,  the capability  for
            non-precision  GPS  approaches  down  to  Minimum   Decision
            Altitude (MDA).  Key to  this implementation is the  concept
            of Required  Navigation  Performance  (RNP)  and  certifying
            navigation systems to  meet RNP type  requirements.   (Under
            the FANS concept, the navigation system must demonstrate  it
            can  meet  the  RNP   type  requirements  rather  than   the
            individual sensor components  each having  to meet  specific
            requirements.  Such  a  change  in  concept  recognizes  the
            benefits of multiple sensor systems and provides a means  of
            traversing gaps in GPS coverage.)  The FMCS will  constantly
            monitor  Actual  Navigation  Performance  (ANP)  and  if  it
            exceeds the RNP, the  pilot will be  alerted.  Advisory  and
            status messages  also  provide provide  the  crew  real-time
            awareness of system availability.

            Required Time  of  Arrival  (RTA) will  give  the  crew  the
            ability to assign a time constraint to a lateral way  point,
            allowing them to cross  a latitude/longitude at a  specified
            time (AT, AT/AFTER, AT/BEFORE).  The FMCS will automatically
            adjust the  cruise  speed  to  achieve  that  time  (+/-  30
            seconds).  If  the FMCS cannot  guarantee that  performance,
            the crew  will be  notified via  a visual  alert.   The  RTA
            Constraint can be uplinked as an  ATC request and loaded  by
            the crew into the FMCS.

            The benefits for the FANS 1 functions center around  reduced
            fuel burn, reduced flight time, and increased cargo capacity
            for take-off  weight  limited  flights.    Trials  flown  by
            airlines as part of the Pacific Engineering Trials have show
            3000 lbs fuel burn reduction and approximately 6 minutes  of
            flight time  reduction.   The fuel  burn reduction  provides
            benefits in reduced fuel costs, but can provide even greater
            benefit when that fuel weight is  replaced by cargo.   These
            benefits vary with the route structure and wind  conditions,
            but conservative  averages of  1% fuel  burn and  6  minutes
            flight time reduction have been deemed reasonable.

            The FANS  1 Package  primarily affects  the FMCS,  but  also
            requires updates to the Integrated Display System (IDS)  and
            Modular Avionics Warning  and Electronics Assembly  (MAWEA).
            Concurrent installation of the Global Positioning  Satellite
            option is highly recommended due to the  inter-relationships
            between GPS and FANS  1 benefits.   GPS cannot be  installed
            without FANS 1  due to the  requirement to  modify the  FMCS
            software.   The GPS  modification affects  the IDS  and  the
            Central Maintenance Computer.  The changes required for  all
            of these modifications have been coordinated and  scheduled.
            An operational data  link requires the  installation of  the
            Aircraft  Communications  Addressing  and  Reporting  System
            (ACARS) Management  Unit  (MU)  and  oceanic  benefits  will
            require installation of a data capable Satcom system.

            The  Master  Changes  for  these  modifications  have   been
            released by Boeing as of October 1993 and are available from
            Customer Engineering.   The  FANS concept  is a  fleet  wide
            concept.    The three FANS 1 Master Changes (by engine type)
            are:

                 3461MK4143     -    FANS 1 for PW Engines
                 3461MK4144     -    FANS-1 for RR Engines
                 3461MK4145     -    FANS 1 for GE Engines

            The GPS Master Changes are

                 3458MK4018     -    GPS Installation for
                      airplanes with GPS provisions
                 3458MK4020     -    GPS Installation for airplanes
                      without GPS provisions

            Changes to the MAWEA, CMC, and IDS will be accomplished  via
            PRR and shall be basic and installed via Service Bulletins.
   
            GROUND SYSTEM STATUS
            FANS 1 interoperability will be initially implemented in the
            South Pacific,  but  plans  for  rapid  migration  to  other
            regions are  under  way.   The  South  Pacific  ATC  centers
            controlled by the USA  (FAA Oakland Center), Australia,  New
            Zealand, and  Fiji    have agreed  to  have  ground  systems
            certified  and  operational  by  April  1995.    France  has
            formally stated that Tahiti  (which controls a large  Pacfic
            region) will have ATC  DL by mid 1995  and ADS by mid  1996.
            Papua/New Guinea,    and  Singapore  are  also  expected  to
            support FANS 1 in the near future.

            The FAA  has  further  agreed  to  migrate  this  system  to
            airspace controlled  by Anchorage  and New  York by  October
            1996.   The North/Central Pacific airspace is controlled  by
            (FAA) Oakland, (FAA) Anchorage, Tokyo, and Russian Far  East
            control centers.    The Informal  Pacific  ATC  Coordination
            Group (IPACG)  and  the Russian  American  ATC  Coordination
            Group (RACGAT) have  initiated CNS/ATM development  programs
            that are expected to mature by April 1996.

            Planning  for  rapid  migration  to  other  regions   (North
            Atlantic, Asia/Europe)  is underway.   India  has  announced
            that it has developed an ARINC 622 compatible ground system,
            and announced a FANS only  route from Phuket, Thailand,  via
            Port Blair  in the  Andeman Islands,  to Vishakhapatnam,  on
            India's central east cost (this will cut 60nm off the normal
            route and is the first FANS only route).

            The  747-400  FANS-1  functions   were  designed  to   allow
            integration into the other  Boeing models requiring  enroute
            operational enhancement.   Boeing has  committed to  deliver
            the FANS  1 functions  as basic  on  the 777  airplane  with
            incorporation currently  planned in  a late  1996  follow-on
            certification.  The  implementation of FANS  1 functions  on
            the 757/767 is under review.

            Note:  Author David  Allen is the  project engineer for  the
            747-400 Flight Management  Computer System at  BCAG.  He  is
            coordinating the development  of the FANS  1 improvement  to
            the Flight Management System for the 747-400.

            For more information on 747-400 FANS 1, please contact David
            Allen at FMCDave@aol.com