ABSOLUTE FLOW CONTROLABSOLUTE FLOW CONTROL

AVTECH Sweden AB

Linköpings University

Jon H. Ertzgaard, AVTECH Sweden AB

RNoAF, USAF ETPS

Saab Chief Test Pilot and Project Test Manager -J35F Draken-AJ37 Viggen,

Saab 340, Saab 2000, man. guided missiles.

J39 Gripen Flight Control System

CAA Chief Test Pilot Saab 340 Certif.

SAS Line Capt., Instructor, Project Pilot,

Headed the AI/Airline A340/A320 Cockpit-Systems Integration Group

Cosultant to NASA (Ames), Fokker etc. Saab Friction Tester

Håkan Andersson, University of Linköping Master of Science, Comunication and transportation systems

AIR TRAFFIC CONTROL

”- problem solving of a continuously selfgenerating chaotic situation – ”

¤ DENSITY VARIATIONS

¤ ATC INTERVENTION

¤ STRATEGIC planning – TACTICAL intervention

¤ SLOT TIMES

SEPARATION

VIOLATION

CONFLICT

None – Metered Flow

Flow

Time

Min. separation

WASTE

Metered Flow

Inbound Flow

Time

Final approach-

ATC

Approach Control

METERING

Conflict

Land

None-metered Flow

Maximum approach flow

RWY

En-route

Minimum landing separation

OLDAOC -X

DISTANCE vs TIME

8 NM / minute

2,5 NM / minute

NM / minute?

Distance compression

Metered FlowInbound Flow

Time

Final approach-

Fine

METERING

Land

RWY

En-route

Minimum landing separation

ATM

Flow planning

METERING

NEW

Maximum approach flow

AOC

METERED FLOW

4-D NAV4-D NAV Planning

#

4-D NAV4-D NAV Execution

#

Optimum flight

(Free Flight)

Routes Flown for TrialsRoutes Flown for Trials

Malmö

Ängelholm

Luleå

Stockholm

33 RTA trial flights conducted by Smiths Aerospace with SAS.

Swedish CAA provided “undisturbed” priority servicing.

17 different flight crews.Smiths Aerospace test conductor in

jumpseat with SONY Digital-8 camcorder.

Malmö Ängelholm Luleå23 flights 8 flights 2 flights

TRAILTRAIL

Accurate Time Separation based on Distance and Ground Speed only

Tactical Sequencing and Separation tool

ATC defined – Flight Crew executed

Requires accurate positioning

Accuracy equal to or better than 4-D Nav.

TRAIL

Mixed equipage

Failure cases – backup

Wind information / Speed Profile

Parallel runways

CONTROL METHODSCONTROL METHODS

Num

ber

of to

uch

dow

ns

Touchdown separation (time)

Sep. min

Old

OLD

• Distance control•Information transfer lag

• Accuracy New

NEW

• Time control•Update rate

• Stability

OBJECTIVE

Investigate methods to increase air traffic flow (runway throughput) up to physical or regulatory limits

reduce waste of airspace

increased flow (throughput)

OBJECTIVE

Understand Air Traffic Flow and define Control Mechanisms to

- STABILISE Flow

- MAXIMISE Flow

APPROACH & LANDING (ARRIVAL RATE / RUNWAY

THROUGHPUT)

OBJECTIVE

Improved understanding of

- Flow characteristics

- Flow disturbances and propagation /damping

- Flow control

1

2

Maximum advantage

with

minimum changes to

procedures and infrastructure

Traffic flow characteristicsTraffic flow characteristics

CompressibilityDensity

– Aircraft performance– Pilot/Controller performance

3-dimensional flow

Flow – DensityFlow – Density Relation Relation toto Air-traffic Air-traffic

Method– Analogy from Road-traffic R/D– Assumed as 1-dimensional flow– Focus on final approach (traffic stream)

Definition of– Critical factors– Max and optimal density

ROAD TRAFFIC FLOWROAD TRAFFIC FLOWOld problem (1950)Flow modelsSimilarities with Air traffic flow

– Precision of a second– Compressible

Differences– Need of speed– Leakages of flow

Flow - densityFlow - density Final approach Traffic streamFinal approach Traffic stream

Kopt => qmax

Kmax = sep. min

Res

ulti

ng F

low

, q

(veh

/hr)

Planned Density, k (veh/mi)

kopt kmax

Free flow

Forced flow

Over saturated flow

Vmax

Vmin

qmax

TouchTouch dowdownn distribution distributionN

umbe

r of

touc

h do

wns

Touch down separation (time)

Sep. min

Present system

Improved system

Reduction of waste

PresentPresent ATC ATC control loop control loop

Pilot Aircraft

RadarController

Improved control loopImproved control loop

Pilot Aircraft

High accuracy A/C

positionADS-B

Controller

F(t)

F(t) = Control law

Automatic control loopAutomatic control loop

Pilot Aircraft

GNSSController

F(t)

F(t) = Control law

TRAIL CONTROL LAWTRAIL CONTROL LAW

Requires relative position and Ground Speed PDI-Controller Input = Time Error Output = Acceleration

Required time

Time error

Air – Air Information

Relative Position

String control

Absolute reference control

ExampleExample

Conditions– String control– Speed adjustment– PDI-Controller– 1Hz update frequency– Equal aircraft performance– Stable string– Final approach

Speed profileSpeed profileGS (m/s)

113

85

67

1 NM 19 NM Distance flown from start of run

Speed – Distance Speed – Distance

Time error – time Time error – time

RESULTSRESULTS

Flow Control– Stable– High precision (milliseconds)

Required developments– Phase shifted speed profile– Information transfer lag– Gross control

¤ TRAIL separation Control accuracy measured in meters and fractions of a second

¤ TRAIL separation that approach legal and physical limits (ROT, WING VORTEX)

FINDINGS

AIRBORNE-Systems available now (4-D Nav.) or soon (TRAIL) - Compatible procedures

GROUND-Technical Systems modifications ”simple” !-- Procedures and responsibilities ???

FINDINGS

Factors That Affects FlowFactors That Affects Flow

Controllers precision and authority

Disturbancese, For example: Mix of aircraft

Environmental Conditions

Navigation accuracy

Buffer – Time – Track

Planning

Metered vs Unmetered Flow

Negotiation/Renegotiation

Sequencing

Ground

AirTRAIL vs 4-D

Execution

Old FMS, DME/DME

New FMS, GNSS

Mixed equipage

Accuracy and stability

REQUIRED STUDY

Track adjustment - gross control

IAS

Speed adjustment - fine control

CONTROL POWER

TRAIL

Speed Correction Authority

Track Correction Control Law

Robustness

Update rate (stability)

Information Transfer Lag (accuracy)

Disturbance

Mixed performance

REQUIRED STUDY

AVTECH - LIU

CONSORTIUM

STRATEGIC PLANNING based on 4-D navigation

CONCEPT

4-D navigation or transition to

TRAIL

STATEGIC PLANNING based on

4-D navigation information

OPTIMUM FLIGHTbased on

4-D navigation

PLANNING AND EXECUTING A METERED FLOW

ATC ¤ STRATEGIC planning –

TACTICAL intervention

ATM

¤ STRATEGIC planning – TACTICAL intervention

ATS

4-D NAV4-D NAV

Position determinationPosition determination##

Silos/Railroad tracksSilos/Railroad tracks##

FMSFMS-DME/DMEDME/DME

-GNSSGNSS

##

TimeTime

4-D NAV4-D NAV

Requires common time baseRequires common time base##

SequencingSequencing-Strategic Planning-Strategic Planning

-Tactical Intervention-Tactical Intervention

RTA Time-Control WindowRTA Time-Control WindowControl PowerControl Power

17:24:00

17:25:26

17:26:53

17:28:19

17:29:46

17:31:12

17:32:38

17:34:05

17:35:31

276

254

225

198

167 9

5

78

63

48

32

23

13 7

2.1

Distance to RTA Waypoint (nm)

Tim

e (G

MT

)

Latest A rriva lT im e

E arliest A rriva lT im e

Descent PhaseCruiseFL350

Climb

R equired T im eof A rriva l

F light #23 D ata

h=10,000 ft

3 %Gain

7 %Loss

Example of Modeled vs. Example of Modeled vs. Actual Descent WindsActual Descent Winds

-15 -10 -5 0 5 10 150

50

100

150

200

250

300

350

400

Flig

ht

Lev

el

Headwind (knots)

Forecast Winds (entered in FMS)Actual Descent Winds

- ” Present Air Traffic Management is a series of disconnected events conspiring to prevent the efficient conduct of flight ”-