20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 11

Eurofighter Transonic Eurofighter Transonic Pitch Up MitigationPitch Up Mitigation

andand

Auto Low Speed Auto Low Speed Recovery (ALSR) Recovery (ALSR)

ConceptConceptHeinz Spölgen, EADS Test Pilot

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 22

Eurofighter Transonic Eurofighter Transonic Pitch Up MitigationPitch Up Mitigation

Heinz Spölgen, EADS Test Pilot

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 33

What happened?What happened?Transonic DecelerationTransonic Deceleration

offline simulationoffline simulation550 KEAS 550 KEAS worst case worst case

∆Nz ~4g

~1 sec

0.0 2.0 4.0 6.0 8.0

0.0

5.0

10.0

10.0

nz

nznz Auth.

Time (s)

Nz

M 0.98 M 0.95

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 44

ImpactsImpacts

• Handling Qualities

• Overstressing of aircraft structure

• non-compliant stability margin

• degraded performance and manoeuvring potential

• customer concerns

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 55

Problem Analysis Problem Analysis

M=0.9

M=0.95

M=0.975

M=1.05

M=1.1

10 20 300-20

0.08

0.06

0.04

0.02

0.00

-0.02

-0.04

-0.06

-0.08-10 40

AoA [deg]

CmCm

AOA [deg]

M 0.95, 6° AOA

M 0.975, 12° AOA

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 66

Problem Analysis (2)Problem Analysis (2)

4.006.00

C m

0.00

-0.01

-0.02

-0.03

0.01

0.02

0.03

0.9 1.0

Mach [-]

0.95 1.05 1.1

Cm

Mach

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 77

Mitigation Options (1)Mitigation Options (1)

Basic Philsophies:

• Change Aerodynamics

• predictive technique

• based on airdatameasurements and prediction model

• technique based on detectionat „time of occurrence“

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 88

Mitigation Options (1)Mitigation Options (1)Split Split FlaperonsFlaperons

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 99

Mitigation Options (2)Mitigation Options (2)

Transonic Pitching Moment CompensationTransonic Pitching Moment Compensation

Required Air Data Accuracy Required Air Data Accuracy Mach +/Mach +/-- 0.0050.005

Achieved Accuracy Achieved Accuracy Mach +/Mach +/-- 0.0250.025

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 1010

Mitigation Options (3)Mitigation Options (3)

two potential solutions:• „G-bucket“ with TPMC

(Transonic PitchingMoment Compensation)

• „Asymmetric Stiffness“

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 1111

Mitigation Options (4)Mitigation Options (4)

red: w/o g-bucket or asy. stiffness=> overstressing (worst case)

blue: asymmetric stiffnessblack: with g-bucket

9g7g

Mach

0.9 1.0

nz<9g

12g

0.87 1.05

Nz

Mach

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 1212

Asymmetric Stiffness (1)Asymmetric Stiffness (1)Basic Principles

Estimation of AOA response

Comparison withmeasured AOA

if measured AOA > estimated AOAplus

positive αimminent pitch up

„Asymmetric Stiffness“ ACTIVE

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 1313

Asymmetric Stiffness (2)Asymmetric Stiffness (2)

ddt Gα

Gd

dt q

GA3AFADA

FQEA GQ5A ∫

Gα

GA1A

ddt

Gα

α

q

nzα(nz)

αc

-

PID-controller

Asymmetric stiffness AoA-feedback

GA5AGA5AFXDA

SI1A FIIA

compensatingpitch down motion

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 1414

““Proof of Concept” Flight TestProof of Concept” Flight Test

• Experimental Software „on top of“ FCS Software• Dedicated flight test campaign• 6 flights (61 test points) in 4 days• 5 pilots (industry and Officials)• Comparison „G-Bucket“ / „Asymmetric Stiffness“

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 1515

ResultsResults• predictions for „G-bucket“ and „asymmetric stiffness“

confirmed

• asymmetric stiffness preferred virtually full Nz-authority

• still some minor transonic pitch up

• aircraft behaviour benign and safe

• no exceedance of structural limits

9g7g

Mach

0.9 1.0

nz<9g

0.87 1.05

Nz

Mach

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 1616

Lessons learntLessons learnt

•• Experimental SW and Experimental SW and „„proofproof of of conceptconcept“ “ flightflight test

EfficientEfficient Design Design ToolTool

test

•• AdequateAdequate ADS ADS accuracyaccuracy forfor a a „„predictivepredictive“ “ solution

DifficultDifficult to to achieveachievesolution

High potential High potential

Independent of ADS Independent of ADS accuracyaccuracy and and MachnumberMachnumber

•• AsymmetricAsymmetric StiffnessStiffness

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 1717

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 1818

Auto Low Speed Auto Low Speed Recovery (ALSR) Recovery (ALSR)

ConceptConcept

Heinz Spölgen, EADS Test Pilot

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 1919

FlightFlight MechanicsMechanics IssuesIssues

• unstable in pitch axis

•• AOA AOA measurementmeasurement unreliableunreliable < 50 < 50 ktskts EAS EAS AOA AOA protectionprotection isis lostlost

below 50 kts departurecannot be excluded 100%

AUTO Low Speed Recovery

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 2020

General ALSR General ALSR PhilosophyPhilosophy

ALSR

• must ensure safe recovery fromall conditions ≥ 50 KEAS

• Robustness (gusts, Air Datameasurement tolerances etc.)

• must not be triggered too earlyduring air combat

• must not occur „by surprise“Pre - warning

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 2121

LowLow SpeedSpeed WarningWarning / ALSR / ALSR AlgorithmAlgorithm (1)(1)

30°

60°

90°

γ

50kts EAS

Low SpeedWarning

Low SpeedAutorecovery

V

90°γ

60°

30°

v50 kts EAS

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 2222

LowLow SpeedSpeed WarningWarning / ALSR / ALSR AlgorithmAlgorithm (2)(2)

30°

60°

90°

γ

50kts EAS

Low SpeedWarning

Low SpeedAutorecovery

V

30°

60°

90°

50 kts EAS

γ

v

• higher decelerationrate (e.g. decreaseof thrust)

• positive climb angle rate

• higher altitude• higher aircraft mass

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 2323

LowLow SpeedSpeed WarningWarning / ALSR / ALSR AlgorithmAlgorithm (3)(3)

CDA

speed

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 2424

LowLow SpeedSpeed WarningWarning / ALSR / ALSR AlgorithmAlgorithm (4)(4)

CDA

speed

LowLow speedspeedmanoeuvringmanoeuvring

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 2525

LowLow SpeedSpeed WarningWarning / ALSR / ALSR AlgorithmAlgorithm (5)(5)

pre-warning

FCS Take Over

• MILITARY Thrust• Option for AFTERBURNER• Airbrake IN• recovery manoeuvre

keep speed > 50 kts EAS

hand-over back to pilot(90 – 110 kts EAS)

about 3 sec

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 2626

Auto Auto RecoveryRecovery ManoeuvresManoeuvres (1)(1)

for climb angles < 60°

KnifeKnife edge edge manoeuvremanoeuvre

Roll Roll invertedinvertedand pulland pull

PushPush overover

Dependingon bankangle

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 2727

Auto Auto RecoveryRecovery ManoeuvresManoeuvres (2)(2)for climb angles > 60°

• CDA 60° ~ 80°• close to wings level if < 120 kts at 70° CDA

< 100 kts at 60° CDA

Knife Edge • close to inverted• close to vertical

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 2828

Cockpit Cockpit AspectsAspects (1)(1)

ALSR takes over in about 3 seconds if the pilot doesnot react to the warning

VOICE Warning:

„SPEED LOW –RECOVER“

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 2929

Cockpit Cockpit AspectsAspects (2)(2)

FCS OVERRIDE

plus VOICE Warning:

„FCS OVERRIDE“

20/07/200420/07/2004EF Transonic Pitch Up Mitigation EF Transonic Pitch Up Mitigation

and ALSR Conceptand ALSR Concept 3030

FlightFlight Test Test IssuesIssues

• Build up philosophy expectedminimum speed and target flight pathangle

• speed BIAS (various)• pilot facility for rapidly taking manual

control (HOTAS switch)• equipped test aircraft (spin gantry,

Emergency Power System)

Questions ?Questions ?