Ce document est la propriété d EADS CCR ; il ne peut être communiqué à des tiers et/ou reproduit sans lautorisation préalable écrite d EADS CCR et son

Ce document est la propriété d ’EADS CCR ; il ne peut être communiqué à des tiers et/ou reproduit sans l’autorisation préalable écrite d ’EADS CCRet son contenu ne peut être divulgué © EADS CCR 2004

A Probabistic Approach to handle Cumulative Effects of Personal Electronic

Devices inside Aircraft

EADS CCR Environmental Modelling

Fabien Mangeant


Outlines

• Context of the study and general considerations

• Presentation of the electromagnetic problem

• Methodology to evaluate the vulnerability of a system

• Application of the methodologies to an aircraft

• Possible Electromagnetic Protections for Aircraft

• Conclusion and Perspectives


Context of the study

• European Project EMHAZ FP5 (G4RD – CT – 1999 – 00093) : 2000 2004

• Eurocae WG58 on PED : On-going


Goal :

To evaluate the electromagnetic threat due to Personal Electronic Devices (PEDs) located inside a cavity on different systems (radio communication systems, electronic equipments…)

Electromagnetic problem (1/3)

Remaining questions :

Which data to characterize the vulnerability?

How to obtain these data?


Physical problem split into three parts:

EMISSION of the source(s) (PED)

COUPLING between source and receiver

SUSCEPTIBILITY of the receiver

Electromagnetic problem (2/3)


Electromagnetic problem (3/3)Key Features of « PED environment inside aircraft»

• Wide frequency band (mobile phones, laptop, electronic games, …)

• Many avionics systems impacted (different failure modes)

Hypothesis used within this study

• Dimensions of the sources small compared to the size of the cavity

• Re radiating currents neglected

• « Failure mode addressed » : coupling on radio communication systems (analogic signal) by radiated field through apertures of the aircraft


Methodology to evaluate the vulnerability of a systemEMISSION

Random variable: Ef electric field at one meter at the frequency f in free space (first approach)

Event: E choice of one PED and one orientation

fEOrient

fEPED nOrientatioPEDOrientPEDf

E,, ,,

Mathematical definition of the random variable Ef :

Eff

EE

fE

f

Ex

RE

:

Population:


Methodology to evaluate the vulnerability of a systemCOUPLING

Random variable: Cf transfer function between emitter and receiver at the frequency f

Event: C choice of one position and one orientation of the emitter

Mathematical definition of the random variable Cf :

Cf

Cf

CC

fC

f

Xx

RC

:

fCfC

OrientfC

System Age

fC

AgeOrientPosition

AgeOrientPosition

,,, ,,

,,Population:


Methodology to evaluate the vulnerability of a systemSUSCEPTIBILITY

Random variable: Sf level of susceptibility in electric field at the frequency f

Event: S choice of one receiver and one orientation

Mathematical definition of the random variable Sf :

Sf

Sf

SS

fS

f

Xx

RS

:

fSOrient

fS OrientPositionOrientceiver ceiverfS

,, ,,Re Re

Population:


Methodology to evaluate the vulnerability of a systemVULNERABILITY

Random variable: Zf safety margin between the transmitted power to the receiver by the PED via the system

Mathematical definition of the random variable Zf:

ffff

ff

ff

fS

fC

fE

f

ECSZwith

Zz

RZ

:


one electromagnetic source emits an electromagnetic field

events E, C, S are not mutually excluded

independence of the random variables

Methodology to evaluate the vulnerability of a systemSTATISTICAL HYPOTHESIS


• Emission max(Ef)• Coupling max(Cf)• Susceptibility min(Sf)

• The safety margin in the worst-case approach is equal to:

• The criterion of interference is the following :

WCfWCfWCfWCf ECSZ

0WCfZ

Methodology to evaluate the vulnerability of a systemWORST- CASE APPROACH


• Limit state:

• Safety domain:

• Domain of interference:

0 ffff ZL

0 ffff ZS

0 ffff ZI

Methodology to evaluate the vulnerability of a system

PROBABILISTIC APPROACH


fS

fC

fESCE

Ef

Cf

Sf

ceInterferen

ECSP

,,

0Pr

Probability of interference


PROBABILISTIC APPROACH : EFFET OF ONE PED

ffceInterferen ZP 0Pr


Interferences due to several PEDs

=> incoherent sources (no relation between the phase over the time)

=> coherent sources (difference of phase is constant over the time)


PROBABILISTIC APPROACH : CUMULATIVE EFFECT OF PEDs



PROBABILISTIC APPROACH : CUMULATIVE EFFECT OF PEDs

Probability of interference

ffceInterferen ZP 0Pr

Limit State Function

21

1

2

1

**N

i

fi

fi

N

i

fi

fi

ff ECECSZ

Coherent sources Incoherent sources


Application of the methodologies to an aircraft

Data necessary:

Worst case approach: extremum values of Ef, Cf, Sf

Probabilistic approach: law of distribution of Zf

=> How to generate these data?


• EMISSION / WORST-CASE APPROACH


EMISSION

“Global” envelop of emission

EMHAZ


Numerical model of A 319

Numerical model of A 319


COUPLING


Probabilistic Approach

Probabilistic ApproachWorst-case


COUPLINGComputations with ASERIS-BE



COUPLING



SUMMARY• Susceptibility of the receivers not yet studied => Data to be provided to finish the analysis

• On-going work on Coupling Models (analytical formulas taking into account

• Good behavorial representativeness of the model

• Relative analysis possible

• Dynamics of simulation smaller than dynamics of measurement in the case of a generic mock-up

• Importance of the apertures (doors, windows, slot)


Conclusion

Problems split into three parts Emission Coupling Susceptibility

Data Random variables with marginal laws

Two approaches of the vulnerability Worst case approach Probabilistic approach


Possible Electromagnetic Protections For Aircraft

-100

-80

-60

-40

-20

0

10 100 1000 10000Frequence (MHz)

dB

501-30-1 501-15 570-30 570-15 501-X 570-X X-X-1

Attenuation of different

samples at 50 cm

SHIELDED WINDOWS



VOLUMIC ABSORBERS

Emerson Cuming Eccosorb AN : Carbon loaded, laminate

polyurethane sheets (open-cell foam absorber)

Frequency range 600 MHz - 40 GHz


-110

-100

-90

-80

-70

-60

-50

-40

70 80 90 100 110 120 130 140 150

Frequency (MHz)

Tra

ns

fer

Fu

nc

tio

n (

dB

)

PED 4 SO_WO PED 4 SC_WO PED4 Slot shielded Noise

20 dB attenuation for the mock-up on

VHF – UHF – ATC band


Seal Only

Seal + Shielded Windows

No Protection


Future works

Interferences due to several PEDs => decorrelated sources (no relation between the phase)=> correlated sources (difference of phase is constant over the time)=> Link to be made with realistic data

Statistical Data and hypothesis to be precised

• Correlation between the different random variables

• Better Methods to be used (Mode Stirring Chambers, Probabilistic Methods, …)

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Ce document est la propriété d EADS CCR ; il ne peut être communiqué à des tiers et/ou reproduit sans lautorisation préalable écrite d EADS CCR et son