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FMS WindsMD-11 FMS Winds for Flight Plan Predictions

John LapointeFlight Technical Services

3 January 2001

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• Objectives• FMS wind basics• Cruise forecast wind entries and defaults• Cruise wind linear interpolation and propagation• Propagation of wind values in cruise• Propagation limitations in cruise• Climb and descent forecast wind entries and

defaults• Climb and descent linear interpolation and

propagation of wind values• Wind blending in cruise, climb and descent• Conclusions

FMS Wind Topics

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• Explain how forecast, current, and predictedwinds are entered, interpolated and propagatedfor use in FMS flight plan predictions

• Help pilots make better wind related decisionsresulting in improved accuracy of FMS flight planpredictions and more cost effective operations

FMS Winds - Objectives

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• The FMS wind model supports flight plan predictionsby projecting reasonable estimates of winds alongthe flight plan

• Wind data is used for ETA's, fuel burn, step climbpoints, max/optimum altitudes, flight plan pagealtitude predictions, EFOB, descent paths, fix infopage data, econ airspeeds, pred to calculations,RTAs, path intercept points, et al

• Forecast and predicted wind values are based onpilot entries on the MCDU, uplinked wind data,and/or default values

FMS Wind Model Basics

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• In-flight, the FMS blends current and forecastwinds to compute the predicted wind

• “The Message” - The more accurate andcomprehensive the wind data provided to the FMS,the better the quality of its predictions and themore cost effective your operation can be

FMS Wind Basics

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• Forecast wind for cruise is entered on the VERTREV 2 page for any cruise waypoint

• Linear interpolation of both bearing and magnitudeis used to determine forecast wind betweenentered altitudes

• Wind values computed for each waypoint can bereviewed on ACT F-PLN page 2

FMS Winds - Cruise

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FMS Winds - Cruise(Example of basic wind matrix and flight plan

with no wind data assigned to waypoints)

FL370

FL330

FL290

A C D E F G H I JB

Flight PlanVerticalProfile

Waypoint No Wind Value Assigned Flight Planned Altitude

S/C

S/C

Wind Matrix

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FMS Winds - Cruise (Example of fully populated matrix with

data entered at every waypoint)

FL370

FL330

FL290

A C D E F G H I JB

Flight PlanVerticalProfile

Waypoint Wind Value Entered Flight Planned Altitude

210/80 210/80220/70210/70 290/70 300/60300/40 010/80 020/80 010/80

230/80 220/70 200/80 290/50 300/60 310/70 020/80 030/70 030/80200/80

200/80 220/90 310/60 310/80 030/90 020/80 040/90330/80220/90220/80

Best case scenario

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• If no entries of forecast wind exist on the VERTREV 2 page for any cruise waypoint, forecast windfor all cruise waypoints will default as follows:– If Trip Wind has been entered, the forecast wind for all

cruise waypoints will be equal to the Trip Wind (Case 1)See slide 10

– Trip Wind is defined as the overall route average windand is entered on the F-PLN INIT page

– If Trip Wind has not been entered, the forecast windfor all cruise waypoints will be zero magnitude withcurrent wind or along track bearing (Case 2) See slide 10

FMS Winds - Cruise Defaults(What happens when no cruise entries are made)

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FMS Winds - Cruise Defaults(Matrix is completed with trip wind default)

FL370

FL330

FL290

A C D E F G H I JB

Flight PlanVerticalProfile

Case 1. Trip Wind = HD050 Case 2. Zero (HD000) if no Trip Wind entered

HD050 HD050HD050HD050HD050HD050HD050HD050

HD050HD050HD050 HD050

HD050HD050

HD050HD050HD050 HD050 HD050 HD050 HD050 HD050 HD050

HD050HD050 HD050 HD050 HD050

HD050

HD050

HD000 HD000 HD000 HD000 HD000 HD000HD000HD000 HD000HD000

HD000 HD000 HD000 HD000 HD000 HD000 HD000 HD000 HD000

HD000 HD000 HD000 HD000 HD000 HD000HD000 HD000 HD000 HD0001.2.

1.2.

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• If there is at least one pilot entry of forecastwind, then the forecast wind for all waypointswithout entries is determined by propagation

• Propagation is defined as copying of entered winddata from the waypoint(s) where the entry is madeto other waypoints for which no entries have beenmade

FMS Wind Propagation - Cruise(How the FMS deals with an incomplete matrix)

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• Propagation is performed in a forward, horizontaldirection toward the top of descent through eachwaypoint until another waypoint is encountered forwhich an entry at that altitude has been made(Rule 1)

• If there are no more waypoints with entries atthat altitude, then the propagation is performedthrough each remaining waypoint (Rule 2)

• For waypoints which are prior to the firstwaypoint with a wind entry, propagation isperformed from that first entry in a backwarddirection toward the top of climb (Rule 3)

FMS Wind Propagation - Cruise(Here are the rules - See slide 14)

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• Flight plan modifications which affect anywaypoint with entered forecast winds result inanother propagation of the affected forecastwind values (Rule 4)

• Propagation in a vertical direction is used todetermine forecast winds above the highest andbelow the lowest altitude entry (Rule 5)

• The forecast wind between successive cruisewaypoints is obtained by linear interpolation ofboth bearing and magnitude (Rule 6) This cannotbe seen on ACT F-PLN page 2

• Linear interpolation is used to determine forecastwind between entered altitudes (Rule 7)

FMS Wind Propagation - Cruise(Here are more rules)

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FMS Winds - Propagation Rules(How waypoints get wind values in an incomplete matrix )

FL370

FL330

FL290

210/80 210/80210/80

A C D E F G H I JB

290/50

Entered Wind Data Propagated Wind

210/80 210/80 210/80 210/80 210/80 210/80 210/80

290/50 290/50 290/50 300/60 300/60 300/60 300/60 300/60

300/60300/60300/60300/60300/60290/50290/50290/50290/50 290/50

1,2

6

7

Propagation Rule

3 1*3

5 5 5 5 5 5 55 55

3 3 3 3 1* 1* 1* 1*

1*1*1*1*1*1*

*Rule 2 also applies

4 = FlightPlan Mods

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• When pilot entered forecast wind data is notassigned to every waypoint, an incomplete matrixexists and the propagation function assignsforecast values to all waypoints (Scenario 1) Seeslide 17

• Scenario 1 demonstrates that propagation of windsat FL290 assigns a favorable tailwind to the endof the flight plan

• This misrepresentation may cause the FMS not togenerate step climbs at the correct points in theflight plan as it assumes the higher fuel burn atFL290 is more than offset by the apparenttailwind

FMS Wind Propagation(Managing wind propagation limitations)

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• The inaccurate wind profile will negatively impactfuel predictions, ETAs, and other performancefunctions for the remainder of the flight

• Therefore, when an incomplete matrix exists, onetechnique is to enter forecast wind data at anybut only one altitude

• This will limit horizontal propagation and provide amore accurate wind profile for flight planpredictions (Scenario 2) See slide 18

FMS Wind Propagation(Managing wind propagation limitations )

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FMS Winds - Propagation(Scenario 1 - Managing wind propagation limitations -

winds entered at planned altitudes)

FL370

FL330

FL290

210/90 210/80 200/80 200/80 200/80 200/80 200/80 200/80 200/80220/90

A C D E F G H I JB

290/50 290/50 290/50290/50 290/50 310/70 310/70 310/70 310/70

030/90 020/80 040/90030/90 030/90 030/90 030/90 030/90 030/90 030/90

A/C Heading020º

Tail

Cross

Head

Propagated WindPilot Entered Wind

300/60

Propagation Direction

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030/90

FMS Winds - Propagation(Scenario 2 - Managing wind propagation limitations -

winds entered at any but only one altitude)

FL370

FL330

FL290

210/90 210/80 200/80

290/50 300/60 310/70 030/90 020/80 040/90

A C D E F G H I JB

210/90 220/90 200/80210/80

310/70

020/80 040/90

030/90 020/80 040/90

210/90 220/90 200/80210/80

290/50

A/C Heading 020º

Tail Cross Head

300/60 310/70

Propagated WindPilot Entered Wind

220/90 300/60290/50

Propagation Direction

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• The forecast wind for climb is based on pilotentries on the CLIMB FORECAST page

• Linear interpolation of both bearing and magnitudeis used to determine forecast wind betweenentered altitudes (Case 1)

• Propagation of both bearing and magnitude is usedfor forecast wind above the highest enteredaltitude (Case 2)

• If there are pilot entries on the CLIMBFORECAST page, but no pilot entry is made forthe origin altitude, the origin altitude forecastwind will be zero magnitude with a bearing equalto the lowest entered climb wind bearing

FMS Winds - Climb(Entered Data - See slide 20)

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FMS Winds - Climb(Linear interpolation and propagationof pilot entered climb forecast data)

Entered Climb Forecast Data

280/50FL 250

260/30FL150

250/20FL100

240/10Surface(FL000)

FL280/280/50

FL210/272/42

FL130/256/26

FL090/249/19

Climb InterpolatedValues

FL000/240/10

2

1

Case 1 = Linear Interpolation Between Altitudes Case 2 = Propagated Value

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• If there are no pilot entries on the CLIMBFORECAST page, the forecast wind for climbdefaults as follows:– If Trip Wind has been entered, the forecast wind for

climb is ramped linearly from zero at the origin altitudeto the Trip Wind value at 20,000’ (Case 1)

– If Trip Wind has been entered, the forecast wind forclimb will be equal to the Trip Wind at and above 20,000’

– If Trip Wind has not been entered, the forecast windfor climb will be zero magnitude with current windbearing (Case 2)

FMS Winds - Climb Defaults(No data entered - See slide 22)

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FMS Winds - Climb Forecast(Trip wind linear interpolation with

no pilot entered climb forecast data)

FL200

T/C

Surface

FL100

FL150

HD050

HD050

HD038

HD025

HD000

Case 1. Trip Wind = HD050 Case 2. Zero if no trip wind entered

HD000

HD000

HD000

HD000

HD000

1

2

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• The forecast wind for descent is based pilotentries on the DESCENT FORECAST page

• Linear interpolation of both bearing and magnitudeis used to determine forecast wind betweenentered altitudes (Case 1)

• Propagation of both bearing and magnitude is usedfor forecast wind above the highest enteredaltitude (Case 2)

• If pilot entries on the DESCENT FORECAST pageexist, but no pilot entry is made for thedestination altitude, the destination altitudeforecast wind will be zero magnitude with abearing equal to the lowest entered descent windbearing

FMS Winds - Descent(Entered Data - See slide 24)

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FMS Winds - Descent(Linear interpolation and propagation

with pilot entered descent forecast data)

260/50FL200

230/10Surface(FL000)

240/30FL100

250/40FL150

Entered DescentForecast Data

FL210/260/50

FL160/252/42

FL120/244/34

FL070/237/24

DescentInterpolated Data

Case 1 = Linear Interpolation Between Altitudes Case 2 = Propagated Value

1

2

FL000/230/10

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• If there are no pilot entries on the DESCENTFORECAST page, the forecast wind for descentdefaults as follows:– If Trip Wind has been entered, the forecast wind for

descent is ramped linearly from zero at the destinationaltitude to the Trip Wind value at 20,000’ (Case 1)

– It Trip Wind has been entered, the forecast wind fordescent will be equal to the Trip Wind at and above20,000’ (Case 2)

– If Trip Wind has not been entered, the forecast windfor descent will be zero magnitude with current windbearing

FMS Winds - Descent Defaults(No data entered - See slide 26)

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FMS Winds - Descent(Default Trip wind linear interpolation with

no pilot entered descent forecast data)

FL200

T/D

Surface

FL100

FL150

HD000

HD025

HD038

HD050

Case 1. Trip Wind = HD050 Case 2. Zero (HD000) if no Trip Wind entered

1

2HD000

HD000

HD000

HD000

HD000

HD050

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• The predicted wind for any point is computed byblending the current wind and the forecast wind

• The predicted wind is equal to the current wind atthe current aircraft position and altitude

• For cruise, the influence of the current winddecreases linearly such that the predicted windequals forecast wind 200 NM ahead of and 10,000feet above and below the aircraft (See slides 28-29)

• For climb and descent, the influence of thecurrent wind decreases linearly such that thepredicted wind equals forecast wind 10,000 feetabove and below the aircraft at any given timewith no forward limit (See slides 30-33)

FMS Wind Blending

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FMS Wind Blending - Cruise

B C D E

200 NMForecastAirspace

A

Forecast

Current

F

-10000’

+10000’

BlendedValue

ForecastValue

40 NM 40 NM 40 NM 40 NM 40 NM

Forecast

Blended Wind Airspace

Blending

+5000’

-5000’

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FMS Wind Blending - Cruise(Current altitude and off altitude predictions)

B C D EA

Forecast

100%Current

80%/20%@B

60%/40%@C

40%/60%@D

20%/80%@E

0%/100%@F

F40 NM 40 NM 40 NM 40 NM 40 NM

Forecast

1 2

ExampleWind Value = 1. 40/60 value at current alt then 2. 50% linear between that value and forecast at 10,000’ above

100%Forecast

Blended Value =% Current and % Forecast

100 % Forecast

0%100%

50%/50%

50%/50%

0%/100%

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FMS Wind Blending - Climb

Blended Wind Airspace*± 10000’

Maximum Altitude

Forecast Wind Airspace

Time Now

T/C

Forecast Portionof Climb

Blended Portion of Climb

* Blended airspace has no forward limit

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FMS Wind Blending - Climb

Forecast

Current

Forecast

+5000’

-5000’

-10000’

+10000’

Blending

100 % Forecast

Blended Value =% Current and % Forecast

50%/50%

75%/25%

25%/75%

Time Now

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FMS Wind Blending - Descent

Blended Wind Airspace*± 10000’

Forecast Wind Airspace

Forecast Portionof Descent

Blended Portion of Descent

Time Now * Blended airspace has no forward limit

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FMS Wind Blending - Descent

Blending

Forecast

Current

Forecast

+5000’

-5000’

-10000’

+10000’

100 % Forecast

Blended Value =% Current and % Forecast

25%/75%50%/50%

75%/25%

Time Now

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• The better the input of wind data, the moreaccurate the FMS predictions

• Manual entry of wind data at every cruisewaypoint may not operationally practical soknowledge of limitations and workarounds canbring success

• As an absolute minimum, trip wind should beentered on the F-PLN INIT page for every flight

• Suitability of using trip wind alone should beevaluated for each phase of flight

FMS Winds - Conclusions 1/4

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• If even one wind is entered for a phase of flight,trip wind defaults are overridden and propagationwill determine wind values at waypoints andaltitudes

• Propagation may not provide an accuraterepresentation of the actual wind profile and mayimpact the quality of FMS predictions

• Accuracy is degraded when winds are propagatedto waypoints that differ significantly from theforecast at those waypoints

• Propagation between a few waypoints where windsdon’t change appreciably is insignificant

FMS Winds - Conclusions 2/4

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• Propagation can be limited by entering forecastcruise winds at any but only one altitude

• This technique forces propagation into a verticaldirection except for a small amount of horizontalpropagation between adjacent waypoints where noentries have been made

• If forecast winds are going to be entered, theyshould be inputted at waypoints (cruise) oraltitudes (climb or descent) where significant windchanges occur or there is significant differencebetween forecast/current and Trip Winds

FMS Winds - Conclusions 3/4

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• Significant descent forecast winds should beentered before final descent path computation atapproximately 40NM from the T/D

• All vertical profiles will have a blended portion anda forecast portion and significant variations inthese values can cause problems meeting pathconstraints

• For all phases of flight, blended airspace is alwaysreferenced from the current aircraft position andclimb and descent have no associated forward limit

• Blended or predicted winds are not displayed– The PROGRESS page displays current wind– The ACT F-PLN page 2 displays forecast wind

FMS Winds - Conclusions 4/4