Navigation

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Navigation flight planningby FMS-equipped
aircraft
AI/EE-A 441.0144/01
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Table of contents

• P.3 Navigation flight management
• P.4 An overview of aircraft avionics
• P.5 GPS PRIMARY navigation
• P.8 RNP navigation
• P.10 Flight management
• P.11 Flight planning
• P.12 Vertical navigation
• P.13 Navigation database ARINC 424 format
• P.14 Path terminator concept
• P.15 IF leg type
• P.16 TF leg type
• P.17 RF leg type (new leg type)
• P.18 CF leg type
• P.19 DF leg type
• P.20 FA leg type
• P.21 FC leg type
• P.22 FD leg type
• P.23 FM leg type
• P.24 CA leg type

• P.26 CI leg type
• P.27 CR leg type
• P.28 AF leg type
• P.29 VA leg type
• P.30 VD leg type
• P.31 VI leg type
• P.32 VM leg type
• P.33 VR leg type
• P.34 PI leg type
• P.35 HA, HF, HM leg types
• P.36 ARINC 424 leg transitions
• P.37 Navigation database related issues
• P.38 Compatibility...
• P.39 Production process
• P.40 Some top level issues
• P.44 Recommendations
• P.45 Issues summary
• P.46 Short term
• P.52 Medium term

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Navigation flight management
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An overview of aircraft avionics ...

• Modern avionics have considerably improved flight
  safety on non-precision approaches
• accurate position (RNP 0.3)
• flight plan display on EFIS
• reference approach path
• automated lateral guidance
• automated vertical guidance
• ground proximity warning system (GPWS)
• terrain display on EFIS (EGPWS)
• terrain clearance floor warnings (EGPWS)

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An overview of aircraft avionics ...
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GPS PRIMARY navigation

• AIRBUS is promoting GPS PRIMARY navigation
• All new A318/A319/A320/A321/A330/A340 production
  aircraft are fitted with GPS PRIMARY capable
  equipment
• Ground navaids are only used as a backup
• VOR, DME
• ADF is not used for navigation
• only for procedural navigation check

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AIRBUS system GPS architecture

• Hybrid (A320 family A340 family)

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AIRBUS system GPS architecture

• Autonomous (A300-600/A310 family, retrofit
  solution for A320 family with older ADIRS)

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GPS PRIMARY crew interface

• In GPS PRIMARY mode, on-board system integrity
  has a confidence greater than 99.9, so the FMS
  position can be relied upon without any
  additional navigation cross check (using ground
  based navaids)
• Clear status of GPS PRIMARY is therefore provided
  to the crew

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GPS PRIMARY crew interface
CLB FLT4567890 CRZ OPT REC
MAX FL350 FL370 FL390 ltREPORT UPDATE
AT BRG /DIST --- /----.- TO
PREDICTIVE ltGPS GPS PRIMARY REQUIRED
ACCUR ESTIMATED 2.1NM HIGH 0.16NM GPS
PRIMARY
CLB FLT4567890 CRZ OPT REC
MAX FL350 FL370 FL390 ltREPORT UPDATE
AT BRG /DIST --- /----.- TO
PREDICTIVE ltGPS REQUIRED ACCUR
ESTIMATED 2.1NM HIGH 0.28NM GPS PRIMARY
LOST
triple click during approach
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RNP navigation

• AIRBUS is promoting RNP (required navigation
  performance)
• All A318/A319/A320/A321/A330/A340 aircraft are
  fitted or have been retrofitted with RNP capable
  equipment
• RNP allows crew awareness of estimated aircraft
  position accuracy compared to procedure
  designers required performance assumptions

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RNP crew interface

• RNP management provides HIGH and LOW navigation
  accuracy system monitoring against the Required
  Navigation Performance
• The system estimated accuracy has a 95 confidence

NAV ACCUR UPGRAD
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RNP crew interface
CLB FLT4567890 CRZ OPT REC
MAX FL350 FL370 FL390 ltREPORT UPDATE
AT BRG /DIST --- /----.- TO
PREDICTIVE ltGPS REQUIRED ACCUR ESTIMATED 0.3NM
HIGH 0.28NM NAV ACCUR UPGRAD
CLB FLT4567890 CRZ OPT REC
MAX FL350 FL370 FL390 ltREPORT UPDATE
AT BRG /DIST --- /----.- TO
PREDICTIVE ltGPS REQUIRED ACCUR ESTIMATED 0.3NM
LOW 0.56NM NAV ACCUR DOWNGRAD
NAV ACCUR UPGRAD
NAV ACCUR DOWNGRAD
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AIRBUS flight management details

• Multi-sensor navigation automatic navaid tuning
• triple IRS, dual VOR DME, GPS
• nIRS only, nIRS/VOR/DME, nIRS/DME/DME, nIRS/GPS
• LOC updating
• RNP management
• GPS primary navigation
• RAIM or AIME on-board integrity monitoring
• certified for RNP 0.3 NM use
• Datalink
• including F-PLN, T/O DATA and WIND uplink
  capability from AOC (Airline Operational Control)

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AIRBUS flight management details

• 4D flight planning predictions
• runway to runway 4D pre-computed optimized flight
  profile
• real time optimization
• decelerated approach profile, 3D non-precision
  approaches
• full autopilot coupling capability (dual FMS,
  dual monitored AP)
• time resolution 1 minute, guidance accuracy
  around 2 minutes
• planned improvement to 1 second resolution,
  accuracy better than 30 s

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Flight planning

• Origin
• Departure SID
• Engine out SID
• En-route
• Arrival STAR
• Approach
• Destination
• Missed approach
• Alternate flight plan
• Alternate destination

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Vertical flight management
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Navigation database ARINC 424
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ARINC 424 path terminator concept

• The Path and Terminator concept is a means to
  permit coding of Terminal Area Procedures, SIDs,
  STARs and Approach Procedures
• Charted procedure are translated into a sequence
  of ARINC 424 legs in the Navigation Database
• Flight plans are entered into the FMS by using
  procedures from the navigation database and
  chaining them together

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ARINC 424 path terminator concept

• 23 leg types have been created to translate into
  computer language (FMS), procedure designed for
  clock compass manual flight
• Its high time to implement RNAV, using only
  DO236 preferred leg types IF, TF, RF which are
  fixed and without possible interpretation
• The leg type is specified at the end point
  path terminator concept

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IF leg type

• The Initial Fix or IF Leg defines a database fix
  as a point in space
• It is only required to define the beginning of a
  route or procedure

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TF leg type

• Track to a Fix or TF Leg defines a great circle
  track over ground between two known databases
  fixes
• Preferred method for specification of straight
  legs (course or heading can be mentioned on
  charts, but designer should ensure TF leg is used
  for coding)

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RF leg type (new leg type)

• Constant Radius Arc or RF Leg defines a constant
  radius turn between two database fixes, lines
  tangent to the arc and a center fix

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CF leg type

• Course to a Fix or CF Leg defines a specified
  course to a specific database fix
• TF legs should be used instead of CF whenever
  possible to avoid magnetic variation issues

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DF leg type

• Direct to a Fix or DF Leg defines an unspecified
  track starting from an undefined position to a
  specified fix
• Procedure designers should take into account the
  FMS flight path depends on initial aircraft
  heading as well

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FA leg type

• Fix to an Altitude or FA Leg defines a specified
  track over ground from a database fix to a
  specified altitude at an unspecified position

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FC leg type

• Track from a Fix from a Distance or FC Leg
  defines a specified track over ground from a
  database fix for a specific distance

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FD leg type

• Track from a Fix to a DME Distance or FD Leg
  defines a specified track over ground from a
  database fix to a specific DME Distance which is
  from a specific database DME Navaid

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FM leg type

• From a Fix to a Manual termination or FM Leg
  defines a specified track over ground from a
  database fix until Manual termination of the leg

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CA leg type

• Course to an Altitude or CA Leg defines a
  specified course to a specific altitude at an
  unspecified position

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CD leg type

• Course to a DME Distance or CD Leg defines a
  specified course to a specific DME Distance which
  is from a specific database DME Navaid

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CI leg type

• Course to an Intercept or CI Leg defines a
  specified course to intercept a subsequent leg

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CR leg type

• Course to a Radial termination or CR Leg defines
  a course to a specified Radial from a specific
  database VOR Navaid

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AF leg type

• Arc to a Fix or AF Leg defines a track over
  ground at specified constant distance from a
  database DME Navaid

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VA leg type

• Heading to an Altitude termination or VA Leg
  defines a specified heading to a specific
  Altitude termination at an unspecified position

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VD leg type

• Heading to a DME Distance termination or VD Leg
  defines a specified heading terminating at a
  specified DME Distance from a specific database
  DME Navaid

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VI leg type

• Heading to an Intercept or VI Leg defines a
  specified heading to intercept the subsequent leg
  at an unspecified position

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VM leg type

• Heading to a Manual termination or VM Leg defines
  a specified heading until a Manual termination

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VR leg type

• Heading to a Radial termination or VR Leg defines
  a specified heading to a specified radial from a
  specific database VOR Navaid

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PI leg type

• Procedure Turn or PI Leg defines a course
  reversal starting at a specific database fix,
  includes Outbound Leg followed by a left or right
  turn and 180 degree course reversal to intercept
  the next leg

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HA, HF, HM leg types

• Racetrack Course Reversal or HA, HF and HM Leg
  Types define racetrack pattern or course
  reversals at a specified database fix

HA Altitude Termination HF Single circuit
terminating at the fix (base turn) HM Manual
Termination
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ARINC 424 - allowable leg transitions
The IF leg is coded only when the altitude
constraints at each end of the FX, HX or PI
leg are different. A CF/DF, DF/DF or FC/DF
sequence should only be used when the termination
of the first leg must be over flown, otherwise
alternative coding should be used. The IF/RF
combination is only permitted at the start of the
final approach for FMS, GPS or MLS coding and
only when a straight line, fixed terminated
transition proceeds the start of the final.
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Navigation database related issues
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Compatibility...
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Navigation data production process
AIP
Procedure design by Civil Aviation Authorities
operator responsibility
Data Supplier
ARINC 424 master file
FMS Database Processing
Packed Data
FMS
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Some top level issues

• Navigation database process is not certified
• Transcription of procedures in computer
  language (ARINC 424) requires interpretation
• Procedure designer intent is currently only
  published under pilot language format
• Each FMS implementation logic is different
• May results in different flight paths and SOP
• Charts and aircraft navigation displays differ
• Increased risk of Human error
• Training costs

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Reminder - flight plan construction

• Charted procedure are translated into a sequence
  of ARINC 424 legs in the Navigation Database
• Flight plans are entered into the FMS by calling
  procedures from the navigation database
• Procedure segments are chained together (or
  melded) to form the FMS flight plan

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Example F-PLN procedure melding

• Procedures are chained together to form the FMS
  flight plan. Example

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Example procedure compatibility ?

• Possible procedure misconnects between en-route,
  arrival, and approach charts
• Possible discontinuities between or inside
  procedures
• Incompatible or conflicting altitude requirements
  between arrival and approach charts

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Navigation database recommendations
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Waypoint naming issues

• Different approach procedure types
  (ILS/LOC/RNAV) use different trajectories and/or
  waypoint names without reason
• Unnamed waypoints on charts are assigned default
  names
• Same waypoint names used at different locations
• Chart wording leading to usage of leg types which
  cause the FMS to create its own waypoints, with
  names which do not match chart
• Coding constraints lead to creation of waypoints
  not on the chart

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Procedure trajectory issues

• Chart wording and/or coding rules lead to coding
  of magnetic course leg types such as CF legs
• Chart wording and/or coding rules lead to bad
  coding of vertical descent angles, which are
  critical to a correct vertical path
• IFR minimum altitudes often coded as AT
  constraints
• Overfly waypoints trajectories are not repeatable
• Barometric temperature limitations should be
  indicated on charts

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Why not use overfly waypoints ?

• Overfly waypoints depending on wind, aircraft
  speed, bank angle limitation etc the FMS
  trajectory will be different

overfly wpt
trajectory not repeatable
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Why use fly-by waypoints ?

• Fly-by waypoints better trajectory control is
  achieved as the FMS will track a pre-computed
  curve

fly-by wpt
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Why not use CF legs ?

• CF leg magnetic course angles may mismatch

excessive roll maneuvering
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Why use TF legs ?

• TF legs always fit, independently of magnetic
  variation

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Why code FPA constraint on each FINAL leg ?
FPA matches altitude constraint
FPA greater than altitude constraint
IDLE segment
FPA smaller than altitude constraint
No FPA
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Why not use AT altitude constraints ?

• Using AT constraints may cause undesired vertical
  path

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Why use AT_OR_ABOVE altitude constraints ?

• Using AT_OR_ABOVE constraints and FPA constraint
  on each leg ensures seamless path

MDA
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Medium term - recommendations

• Implementation of DO201A by civil aviation
  authorities for procedure publication
• Implementation of DO200A by data providers
• Implementation of RTCA DO236 / EUROCAE ED-75
• Implementation of ATA Chart, Data and Avionics
  Harmonization Top Priorities
• Improved transatlantic coordination between
  working groups, authorities industry
• ARINC 424, ATA FMS/RNAV Task Force, TARA, RTCA
  SC-181 193, Eurocae WG-13 44, FAA, JAA,
  Eurocontrol, ICAO

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Medium term - ATA CDAH priorities

• Redesign of existing non-precision approaches to
  accommodate VNAV
• Altitudes at precision FAFs
• Unnamed step-down fixes
• Waypoints on EFIS but not in database or charts
• Waypoint names longer than five characters
• Duplicate navaid and waypoint identifiers
• Different altitude for same point on STARs and
  approaches
• Magnetic variation tables used in course
  calculations
• VNAV angle depiction on charts

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Longer term - goals

• Fully resolve the disconnect between
• the procedure design by the Airspace Planner,
• the coded description in the navigation database,
• and the way it is displayed and flown by the FMS
• End-to-end certified process with integrity
  guidelines and criteria
• A worldwide, common process with Airworthiness
  Authorities involvement under an ICAO mandate

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Longer term - recommendations

• Publication of a single standard/language for
  procedure design, database coding, and FMS
• Reduced ARINC 424 set
• Improved charts-database-FMS compatibility
• Design of FMS-friendly procedures
• Publication of these procedures using FMS
  compatible language (in addition to charts)
• Publications of standards for navigation database
  integrity and certification

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Longer term - common language

• Comprehensive worldwide commonality requires
  rules at ICAO level
• A common coding Standard should be
• clearly defined,
• including rules for use by both the aircraft and
  the RNAV Airspace Planner,
• the minimum capability of any "FANS RNAV system,
• the maximum set usable by the RNAV Airspace
  Planner
• This would ensure a unique unambiguous coding of
  routes and procedures

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Longer term - FMS friendly procedures

• Use only fixed, named waypoints
• For straight segments use only TF legs
• For large course changes (gt30) use RF legs
• Use only fly-by waypoint transitions (no overfly)
• Put a waypoint at each vertical path change
• Use descent gradients between 2.5 and 3.5
• Start the missed approach at or before the runway
• Use same waypoint names and approach path for all
  approach types to a given runway
• Use unique waypoint names (max 5 characters)

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Longer term - integrity

• Integrity must concern the entire process, from
  procedure design to the loading of the FMS
• Ultimate goal should be a fully digital process
• Process should be under direct supervision of
  airspace management authorities
• Worldwide implementation requires ICAO rules

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End of presentation Any question?