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Path Terminators for Initial Departure Legs

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( VA may be used by data-house when coding parallel runway operations) DLH experience shows that CA better than FA on initial SID leg. ... – PowerPoint PPT presentation

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Title: Path Terminators for Initial Departure Legs


1
Path Terminators for Initial Departure Legs
2
Background
  • TGL 10 requires CF, DF, FA, IF and TF
    functionality in P-RNAV systems.
  • EUROCONTROL Guidance Material recommends the use
    of FA, CF, DF and TF path terminators when coding
    SIDs and proposes FA with CF or DF to start the
    SID. (VA may be used by data-house when coding
    parallel runway operations)
  • DLH experience shows that CA better than FA on
    initial SID leg.
  • ICAO introducing path terminator requirements in
    PANS-OPS including VA and VI.
  • Evidence that designers already confused by the
    subset defined in existing guidance material.

3
Trial Setup
  • Trials of different path terminator combinations
    conducted using Smiths PC-Sim
  • PC-based simulator.
  • Same processor and architecture as FMS in B737
    6/7/8/900, BBJ etc.
  • Same performance as airborne FMS.
  • Operational packed navigation database.
  • Different departure combinations coded and flown
    under different wind conditions.
  • No manual input during departure other than gear
    and flap retraction hence aircraft climbs on
    heading until autopilot engaged at 500ft agl.

4
PC Sim is manufactured by
5
PC Sim Process
  • Define procedure to be flown.
  • Code procedure for navigation database (Full
    ARINC 424 coding required).
  • Generate operational database (Available only
    through authorised data packer).
  • Load database.
  • Set met conditions.
  • Fly procedure.
  • Output recorded data.

6
Simulation Results - 1
VA (183º 3000ft), CF (270º EHM20) Wind 47kts
223º Wind 35kts 244º Note after reaching
3000ft logic seems to change flying course to
turn initiation point
7
Simulation Results - 1
Extreme case of a straight departure 15 turn
at DER
No wind
30kts cross-wind
8
Simulation Results - 2
Showing difference between CA and VA ground
track After 500ft agl, when AP engages, CA
recovers to 184 track while VA remains on 184
heading until 2000ft agl.
9
Simulation Results - 3
Early turning departure 46 turn 2.6NM from DER
No Wind
30kts Cross-wind
10
Simulation Results - 4
CF 183º to 10NM CF 270º to EHM20 IRS error of 1
lat and 1 long No wind No radio updating before
3000ft (GNSS, DME/DME and VOR/DME)
11
Simulation Results - 5
FA(1842000ft)/DF CA(1842000ft)/DF
12
Results Analysis
  • Simulation did not address the initial climb to
    500ft when the aircraft always maintained runway
    heading.
  • VA, VI and CA generate very similar ground tracks
    in still air.
  • VI seems to provide better track-keeping than VA,
    particularly in high cross-winds.
  • Max displacement between VA and VI ground tracks
    in simulation 450m.
  • May be an avionics specific feature.
  • CA controls drift in cross-wind conditions and is
    not affected by IRS errors.
  • CA/CF, VA/CF and VI/CF are all effective
    solutions for early turns in departure procedures
    where IRS updating may be used by some aircraft.

13
Conclusion/1
  • Procedure designer needs to be able to provide
    clear and unambiguous description of RNAV
    procedure (includes the ground track).
  • Path terminator useful short-hand for required
    leg-following function
  • Fly heading/track
  • Turn at altitude/waypoint/not before...
  • Procedure designer should not be expected to
    become ARINC 424 coding expert taking account of
    all different system peculiarities.
  • PANS-OPS provides an option for
    datahouses/avionics manufacturers
  • In certain cases, alternative path terminators
    may be used to enable specific RNAV systems to
    better follow the intended track such actions
    should be approved by the associated State
    Regulator and are within the purview of the data
    coder and the avionics manufacturer.

14
Conclusion/2
  • Designer should work with the smallest possible
    sub-set of path terminators
  • Headings use VA or VM for departures use VA
  • Tracks use FA, CA, CF, DF, FM, RF or TF for
    departures use DF or CF
  • Turn at altitude but not before(TAABNB) CA/CF
    or VA/CF CA/CA or VA/CA
  • Turn at altitude (CA or VA from the runway, FA
    from a waypoint, CA from a TAABNB)
  • Industry can get approval to alter coding where
    this can be shown to be a better solution for a
    particular aircraft system.

15
Coding the First 500ft
  • Simulation did not address the initial climb to
    500ft when the aircraft always maintained runway
    heading.
  • RNAV has little influence on aircraft
    track-keeping during take-off phase
  • LNAV systems engage at different heights agl.
  • Autopilots generally do not engage before 500ft
    agl.
  • Manual flight may be considered the norm, at
    present, up to at least 500ft agl.
  • Should procedure definition, in path terminator
    context, start from 500ftagl? Probably not!

16
Coding the Initial Departure Legs
  • Initial SID coding should be compatible with all
    approved aircraft
  • VA(xxxxft) followed by CA, CF or DF can be flown
    by all P-RNAV aircraft
  • The other get out option is to describe the
    initial legs conventionally and start the
    official RNAV procedure once the aircraft is in
    adequate coverage and the design can meet the
    criteria (min distance between waypoints etc.) It
    will still be coded by the datahouses.

17
Initial Legs Conventional/1
Rwy hdg to 2.5 D HEL, turn right to intercept
R254 HEL
FD (222º, 710ft, 2.5D) VI (285º) CF (254º) HK619
No Wind
FD (222º, 710ft, 2.5D) CI (285º) CF (254º) HK619
18
Initial Legs Conventional/2
Rwy hdg to 2.5 D HEL, turn right to intercept
R254 HEL
FD (222º, 710ft, 2.5D) VI (285º) CF (254º) HK619
30kt X-wind 30kt Headwind
FD (222º, 710ft, 2.5D) CI (285º) CF (254º) HK619
19
QUESTIONS?
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