4-3MAS33 - J. BERARD - FMS Lateral Guidance 2012

Mai 2009

Pilotage - Guidage FMS

Piloting-Guidance:Flight Management System

Guidance along the lateral flight path

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Mai 2011Pilotage - Guidage FMS

FMS in Piloting - GuidancePiloting function:

• allows to control the Aircraft movement around the Centre of Gravity (CG)

=> CDVE, inner loop of the Auto Pilot (AP)

Guidance function:• allows to control the Aircraft on a pre-planned path

=> Outer loop of the AP , HPATH and VPATH modes of the FMS.

Flight Management function:• allows to define an optimized lateral and vertical profile

=> FMS

Navigation function:• aircraft position computation (Nav sensors), optimal nav sensors (or fusion of nav sensors) selection

=> FMS

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A F-PLN is a combination of elementary element :

FMS – What is a Flight plan ?

Departure airport

Arrival airport

Each airport is identified by an ICAO code / four-letter

LF - FRANCE

LFBO (TLS) – Toulouse / Blagnac Airport

LFPG (CDG) – Paris / Charles de Gaulle Airport (Roissy Airport)

LFPO (ORY) – Paris / Orly Airport

EG – UNITED KINGDOM

EGKK (LGW) – London / Gatwick Airport

EGLL (LHR) – London / Heathrow Airport

The three-letter code (IATA code) is more commonly known to the public.

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Departure airport

Arrival airport

Departure procedure

A Departure procedure contains 3 optional elements : - RWY (runway and runway transition)

- SID (Standard Instrument Departure)

- TRANS (SID enroute transition)

EnrouteSID enroute TRANSSID

Runway

RunwayTRANS

Search downstreamFirst point of enroutein reference F-PLN

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Departure airport

Arrival airport

Departure procedure

Engine Out procedure

An Engine Out procedure or EOSID is a standard procedure to use if an engine fails just after take off.

Runway

Search downstream

EOSID diversion point

3000 A

B

C

D

E

EOSIDA

EOSIDB

EOSIDCEOSIDD

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Departure airport

Arrival airport

Departure procedure


Arrival procedure

An Arrival procedure contains 4 optional elements : - APPR (Final approach including runway & missed approach)

- VIA (Approach transition)

- STAR (Standard Terminal Arrival Route)

- TRANS (STAR enroute transition)

Enroute STARenroute TRANS

Approach and missed approach

Search upstream Last point of enroutein reference F-PLN

STAR

Search upstream

Runway

Search downstream

Approach TRANS (VIA)

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Departure airport

Arrival airport

Departure procedure


Arrival procedure

Waypoints

5 means to identify a waypoint : - An Ident ex : BEROK

- A Latitude/longitude ex : 44°09.9N/010°21.1E

- A place/bearing/distance (PBD)ex : BEROK/100/10

- A place-bearing / place-bearing (PB/PB)ex : BEROK-090/SIPLO-045

-A place-distance or Along Track Offset (ATO)ex : BEROK/10

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Departure airport

Arrival airport

Departure procedure


Arrival procedure

Waypoints

Airways

An Airway is a published route.

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May-June 2010Navigation Page 9


Departure airport

Arrival airport

Departure procedure


Arrival procedure

Waypoints

Airways

Holding pattern

Due to traffic, the pilot may define holding pattern.

The FMS includes the Holding pattern into the flight plan

3-2-1) Lateral Flight planning - What is a Flight plan ?FMS – What is a Flight plan ?

H O L D A T AI N B C R S

3 4 0 °T U R N R E V E R T T O

L D A T A B A S E →

T I M E / D I S T

1 . 0 / 4 . 0

L A S T E X I T

U T C F U E L

- - - - - - - . -

← E R A S E I N S E R T *

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Departure airport

Arrival airport

Departure procedure


Arrival procedure

Waypoints

Airways

Holding pattern

Alternate airport

An alternate airport is a stand-by destination usedin case of non-landing on primary destination.

PrimaryDestination

AlternateDestination

AlternateF-PLNportion

Departure

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FMS – Flight plan skeleton

After this initialisation a skeleton of the complete F-PLN is available

Navigation Display (SA/LR) F-PLN page on MCDU (SA/LR)

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3 classes of legs are used :

FMS – Construction of the flyable lateral path

Fixed path legs(1/2)

These are characterized by the fact that their geographic location is perfectly fixed.

IF : Initial Fix

TF : Track to a Fix

CF : Course to a Fix

FM : From a fix to aManual termination

FA : Fix to an Altitude

PI : 045/180 procedure turn

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DF : Direct to a Fix

HA/HF/HM : Holding pattern

AF : Arc a Fix

RF : Constant radius Arc

These are characterized by the fact that their geographic location is perfectly fixed.Fixed path legs

(2/2)

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Fixed path legs

Heading legs

These are characterized by a heading to follow from the preceding leg. They end when given conditions are met.

VD : Heading to aDME distance termination

VI : Heading to anIntercept

VM : Heading to aManual termination

VR : Heading to aRadial termination

VA : Heading to analtitude termination

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Fixed path legs

Heading legs

Course legs

These are characterized by a Course to follow from the preceding leg. They end when given conditions are met.

CR : Course to aRadial termination

CD : Course to aDME distance termination

CI : Course to anIntercept

CA : Course to analtitude termination

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Ex – SID SAM3P on EGKK airport with 08R runway :


Leg type Fix Couse/Heading Altitude Turn DirectionFA : From fix to an altitude 08R 80° 700A CF : Course to a fix D265B 80° 1200A TF : Track to a Fix D080C DF : Direct to a fix DET26 2500A LeftTF : Track to a Fix DET36 3000 TF : Track to a Fix DET43 4000 TF : Track to a Fix SAM

700

Course 080°

EGKK08RD265B

DET26

D080C

DET36

FACF

08R

TF

TF

DFTF

DET43

SAM

TF

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Transitions between legs :


Transition between two leg is dependent of :

- type of both legs

- A/C parameters (Ground speed and Roll angle)

- The course change between both legs

700

080°

EGKK08RD265B

DET26

D080C

DET36

FACF

08R

TF

TF

DFTF

Geometric path

D015J

D231L IF

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- type of both legs

- A/C parameters (Ground speed and Roll angle)

- The course change between both legs

- FMS manufacturer design for comfort and performance

- Maximum Turn Anticipation Distance (TAD)

- Phi nominal (altitude, speed, ….)

- Phase of flight

- Engine (engine out consideration)

- ……

No predictable and repeatable path is specified

Optimum path varies with various parameters:

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For fly-by transition, regulation defines predictable and repeatable boundaries of the transition area are defined (DO-236)

The boundaries is defined with the following parameters:

- Radius of turn (R) in NM :

- Turn Initiation Boundary Distance (Y) in NM :

Where : V+W is the maximum Groundspeed assumed for the transition in Kts.

α = track change, in degrees

Ф is the maximum aircraft bank angle, in degrees.

For Low altitude transitions (<FL195 )

(V+W) = 500 kts

Ф = min(α/2 ; 23°)

.

For High altitude transitions (>FL195)

(V+W) = 750 kts

Ф = 5°, by default.

If 5° results in Y > 20 NM, then

Y = 20 NM and R = 20/tan(α/2)

.

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FMS Navigation Function

Departure Runway

Departure Procedure

(SID)

Destination

Runway

Arrival Procedure

(STAR)

En Route Phase

?Where am I?

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Conventional sensors/means onboard AIRBUS aircraft

A/C Position computation

Autonomous Navigation

- Time

- Air Data

-Inertia

-Radio-altimetry

RADIO-NAVIGATION

Cruise :

- ADF

- VOR

- DME

- GPS

Approach/Landing :

- ILS/MLS/DGPS/SBAS


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Autonomous Navigation means• Inertial units :

• outputs : AttitudePosition : Latitude / LongitudeVelocity


• Radio-altimeter :

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• ADF (Automatic Direction Finder) :• Outputs : azimuth of ADF Navaid wrt aircraft axis.

Radio-Navigation

Bearing

Navaid direction


• VOR (VHF Omni Range) :• Outputs : magnetic radial of the navaid

Azimuth

Nm

Nm

Heading

VOR Navaid

Radial

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• DME (Distance Measuring Equipment) : • outputs : direct distance between A/C and the DME navaid

Radio-Navigation

R E Answer delay 50μs

DME ground station

ρ


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P O S I T I O N M O N I T O R

F M G E C 1 4 6 1 0 . 2 N / 0 0 6 1 8 . 3 E3 I R S / D M E / D M E


R A D I O 4 6 1 0 . 1 N / 0 0 6 1 8 . 2 E

M I X I R S 4 6 0 9.72N / 0 0 6 1 8 . 0 EI R S 1 I R S 2 I R S 3

N A V 0 . 4 N A V 0 . 2 N A V 0 . 4

S E L

← F R E E Z E N A V A I D S >


Inertial

Radio

GP(IR)S

IRS 1, 2, 3

DME

VOR

MMR

LOCposition FMS

Position computation in FMS – General principle

ρ/ρ position

ρ/θ position

Navigation

Function


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Navigation modes automatic/optimum selection

IRS Position

Available + reasonable

GPS Position


Radio Position


NO NAV

GPS/INERTIAL

RADIO/INERTIAL

INERTIAL ONLY

No

No

No

Yes

Yes

Yes

DME/DME VOR/DME


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P O S I T I O N M O N I T O R



R A D I O 4 6 1 0 . 1 N / 0 0 6 1 8 . 2 E

M I X I R S 4 6 0 9.72N / 0 0 6 1 8 . 0 EI R S 1 I R S 2 I R S 3

N A V 0 . 4 N A V 0 . 2 N A V 0 . 4

S E L

← F R E E Z E N A V A I D S >

NAV mode

Available

positions

IRS drift

HMI – Synthesis of Position computation function


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Flight planning : the path to follow

Navigation : I know where Iam

FMS – Guidance along the lateral path

Departure Runway

Departure Procedure

(SID)

Destination

Runway

Arrival Procedure

(STAR)

En Route Phase

Guidance along lateral path

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Lateral guidance :- is controlled by pilot or by FMS depending onlateral guidance mode.

- is based on the Active leg (leg A/C is supposed to fly)of the Primary F-PLN.

- takes into account a notion of F-PLN sequencing (leg switching when specific condition between two legs is reached)


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Two lateral guidance mode are availableManaged modeManaged mode is engaged by pushing the HDG/TRK selector knob on FCULateral guidance is controlled by the FMS to follow the trajectory as defined onMCDU (MFD).

Selected modeSelected mode is engaged by pulling the HDG/TRK selector knob on FCULateral guidance is controlled by pilot selection on the FCU

FCU on A380FCU on SA/LR

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LateralGuidancemode


SA/LR

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Managed modes Engagement logic

RWY • During TO up to 30 ft RA

NAV

• 3 submodes : Heading (if Active Leg = Heading Leg)Track (if Active Leg = Course Leg)HPATH (if Active Leg = Course Leg) : roll command

APPNAV

LOC

LAND

Depending on precision or non precision approaches

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In NAV Managed mode, depending on active leg type the FMSsteering commands are :

- Roll targets for fixed path legs (TF, CF, DF, …) : HPATH Submode

- Heading targets for heading legs (VD, VI, VM, …) : HDG Submode

- Track targets for course legs (CD, CI, CA, …) : TRK Submode


DET26

DET36DF

D015J

Active leg

D080C is the FROM wpt

DET26 is the TO wpt

DET 36 is the NEXT wpt

Command=

Roll target

D080C

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The HPATH Law

HPATH

law

XTK

TKE

Phi target

Ground speed

Phi commandé

GS

Desired course

XTK

TKE

GS*TKE

Phi target

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HPATH Law input

Phi target computation

)_

arctan(2

arg radiusturngGSsignsegmentett ×

×=φ

0arg =ettφStraight segment & final RAD =>

Curved segment & initial RAD =>

RAD = Roll Anticipation Distance

= distance from the termination of the leg at

which the phi target is modified to reach the

phi target of the next segment at the entry point

= f(Δroll angle , roll rate, ground speed)

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HPATH Law in FMS

HPATH

law

XTK

TKE

Phi target

Errors

computation

Phi target

computation

Navigation

Ground speed

Ground speed

Segment

sequencing

Aircraftposition

Aircraft position

Activesegment

Active & nextsegment

Trajectory

Model construction

Aircraft

states

Phi

commandé

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NAV guidance mode

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FMS – Guidance along the lateral pathNAV guidance mode is armed (1/3)

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FMS – Guidance along the lateral pathNAV guidance mode is armed (2/3)

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FMS – Guidance along the lateral pathNAV guidance mode is engaged (3/3)

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F-PLN Sequencing :


An automatic sequencing occurs when :- A/C overflies TO waypoint or crosses with specific condition for fixed path legs.- conditions linked to the leg are met for heading and Course legs.

In this example, A/C is in selected mode,ABADI has been passed with a Crosstrack error less than 5NM. TO waypoint is now BOKNO

XTRKerror

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F-PLN Sequencing :


When conditions for automatic sequencing are not met the F-PLN must be sequenced manually.

The FROM is cleared

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F-PLN Sequencing :



ABADI becomes the FROM WPT

A HDG/TRK is selected on FCU to intercept the active legbefore TMPY F-PLN insertion

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F-PLN Sequencing :


Managed Mode is armed

PNEP

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Guidance – Flight Technical Error

Flight Technical Error (FTE) :

The navigation error introduced by the pilot’s (or autopilot’s) capability to utilizedisplayed guidance information to track the desired flight path is commonlyreferred to as flight technical error (FTE).

In the RNP environment, the overall navigation performance must account for thecontribution of FTE.

During real time operation of the system, the FTE can be measured, however duringthe system certification, an estimated system FTE shall be established.

ED75 – DO236B

Minimum Aviation System Performance Standard :

Required Navigation Performance for Area Navigation

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Guidance – Flight Technical Error

Flight Technical Error (FTE) :

FTE should not exceed 1.0 nmi for en route, 1.0 nmi for terminal or approach transition, or 0.25 nmi (for equipment using GPS data) or 0.5 nmi (for equipment not using GPS data) for approach operating modes on a 95 percent basis.

FAA Advisory Circular AC20-130A:AIRWORTHINESS APPROVAL OF NAVIGATION ORFLIGHT MANAGEMENT SYSTEMS INTEGRATINGMULTIPLE NAVIGATION SENSORS

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RNP Concept: Navigation Performance DO-236 Definitions

Desired Path

Defined Path

Path Steering Error (PSE) or Flight Technical Error (FTE)

Path Definition Error (PDE)

Estimated Position

True Position

Total SystemError (TSE)

Position Estimation Error (PEE) or Navigation System Error (NSE)

Example of use : RNP Operation

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November 2010RNP AR flight operations and Services presentation Page 49


Required Navigation Performance (RNP) approach

Navigation accuracy :RNP values

Documents

4-3MAS33 - J. BERARD - FMS Lateral Guidance 2012