Typhoon Transonic Pich Up

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



Eurofighter Transonic Eurofighter Transonic Pitch Up MitigationPitch Up Mitigation

Heinz Spölgen, EADS Test Pilot



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



ImpactsImpacts

• Handling Qualities

• Overstressing of aircraft structure

• non-compliant stability margin

• degraded performance and manoeuvring potential

• customer concerns



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



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



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“



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




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




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

(Transonic PitchingMoment Compensation)

• „Asymmetric Stiffness“




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



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



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



““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“



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



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



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

ConceptConcept

Heinz Spölgen, EADS Test Pilot



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



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



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




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




CDA

speed




CDA

speed

LowLow speedspeedmanoeuvringmanoeuvring




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



Auto Auto RecoveryRecovery ManoeuvresManoeuvres (1)(1)

for climb angles < 60°

KnifeKnife edge edge manoeuvremanoeuvre

Roll Roll invertedinvertedand pulland pull

PushPush overover

Dependingon bankangle



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



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“



Cockpit Cockpit AspectsAspects (2)(2)

FCS OVERRIDE

plus VOICE Warning:

„FCS OVERRIDE“



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 ?

Typhoon Transonic Pich Up

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