Presentazione di PowerPoint hazards on... · 2014-03-13 · • La presenza del terreno •...

Rischi elettromagnetici a bordo

di aeromobili

Corso di Elettrotecnica V.O.

Corso di Laurea di Ingegneria Aerospaziale

a.a. 2001-2002

Prof. M.S. Sarto

• Interferenze con dispositivi elettronici

portatili

• Invecchiamento dei cablaggi

• Effetti indiretti della fulminazione

diretta ed indiretta di aeromobili

• Interferenze con campi elettromagnetici

di elevata intensità (HIRF)

Interferenze con dispositivi elettronici

portatili

Esempi di dispositivi elettronici portatili sono:

• Cell phones

• Laptop computers

• Portable AM/FM Radio Cassette Players

• Portable CD Players

• Electronic Games

• HF Radio

Prove di EMI prodotte da PEDs su aeromobili a terra

sono scarsamente significative:

Le condizioni di prova a terra e di volo sono

completamente diverse a causa di numerosi fattori:

• La presenza del terreno

• L’assenza delle persone

• La forte dipendenza del manifestarsi dell’EMI dai

fenomeni di risonanza elettromagnetica che si

presentano a bordo

• Non si riesce a ricreare le stesse condizioni di EMI a

terra

Posizionamento delle antenne su un AIRBUS 320

Possibili modalità di accoppiamento del disturbo

elettromagnetico prodotto da PEDs su un aeromobile

• US Federal Aviation Regulation 91.21 prohibits the

use of any portable electronic devices on board

aircraft, with the exception of voice recorders, hearing

aids, heart pacemakers, shavers, and any other device

that the operator of the aircraft has determined will not

cause interference with the navigation or

communication systems of its aircraft

• The regulation puts the responsibility firmly on an

individual airline to determine that there is no

interference.

• US airlines implement a general ban on using any

portable electronic devices (PEDs) below 10,000ft

Normative che regolano l’uso dei PEDs a bordo di

aeromobili

Interferenze elettromagnetiche prodotte

dall’uso di telefoni cellulari

Cellular phones are a particular source of problems

because, regardless of whether they may interfere with

aircraft systems, the technology on which cellular

telephones are based precludes their effective use on

aircraft.

This applies to all cellular phones, including the analogue

technology in the US and the digital GSM technology in

Europe.

The technology of cellular phones is based on small local ground-

based reception areas called `cells'. A cellphone user is served by just

one cell, and when reaching the boundary of a cell, will be `handed

over' to another cell which (s)he is about to enter. The topology of

coverage is based on the assumption that the user is on or near the

ground, and it is a technical assumption on which the entire system is

based that a user will be within `sight' of just one cell except when

nearing a cell boundary.

When in an aircraft, however, a user is within radio `sight' of many

cells, simply because (s)he is way off the ground. An attempted call or

reception from an aircraft would activate many if not all cells in the

local area, which `breaks' the technology -- it causes many

transmission problems and the system is disturbed. Therefore the

various communication authorities, such as the US Federal

Communications Commission (FCC), ban the attempted use of

cellular phones while on board aircraft.

Nordwall reports that the RTCA Committee 177 inquiry

found 137 `incidents' (pilot reports, anecdotes) reported

either to them, or to the FAA/NASA Aviation Safety

Reporting System (ASRS) program, or to the International

Air Transport Association (IATA).

VOR reception was affected in 111 incidents -- by far the

most common occurrence.

From the 33 reports direct to RTCA, 21 incidents related

to laptop computers and only 2 to cellular phones.

Navigation systems were affected in 26 of those

incidents; fuel systems, warning lights and propulsion

reported one incident each.

Rough correlation of suspect with effect by turning the

suspect device on and off was found in 14 cases, on-off-on

in 6 cases, and no correlation in 13 cases.

0

5

10

15

20

25

30

35

40

Eve

nts

nu

mb

er

Bo

ard

ing

Ta

xi

be

rore

T.O

.

Ta

ke

off

Cli

mb

Cru

ise

De

sce

nd

Lan

din

g

Ta

xi

aft

er

Ldg

.

Dis

em

ba

rk

Un

kn

ow

n

Signal intensity [dB]

Numero di eventi di EMI prodotta da cellulari

nelle diverse fasi di volo

GSM filed signals drops

to 0 above 3.000 m

Frequenza del numero di eventi per volo

2

7%

3

10%

4

4%

5

6% >5

0%

1

73%

Invecchiamento dei cablaggi

Wiring integrity and safety issues have emerged as a

major aerospace problem associated with the loss of

SwissAir 111 and TWA 800.

Wiring is the nervous system of every electronic system.

Wiring problems have been known to cause loss of

signals, system shutdowns, smoke, fires and

explosions.

In lesser forms, wiring problems cause millions of dollars in

troubleshooting and maintenance. Modern technology

provides a viable solution.

Electrical Wiring Problems

Electrical wiring is usually not a significant problem in new

aircraft, because designers specify a life of over eighteen

years (which is the expected life of the aircraft).

Wiring normally easily lasts the design service life, say 20

years. As systems near the design service life wiring

becomes a major cost driver. Many aircraft are refurbished

and overhauled to stay in service for thirty or more years.

At the Aging Aircraft Conference 2000 the Air Force stated

that it takes 18 months to rewire a C130 aircraft. Because of

the huge cost, and time, wiring is usually not replaced.

Some wiring problems are caused by build up of corrosion

on exposed metal wire surfaces and loosening of connector

pins due to repeated opening of connectors. Other problems

come from abuse during maintenance.

NASA experienced a shutdown of space shuttles due to

rubbing against a sharp screw.

The onboard network is constituted by nearly 12-17

thousands of wires, grouped in 300-500 bundles.

There are: single-core and multi-core shielded and

unshielded cables, data-bus and coaxial cables are.

Cables are classified according their EMC category:

E : emitting

S: susceptible

P: power

R: radio-audio

D: data-bus

Cable bundles of different category running along the same

route are collected to form complex harnesses enclosed or

not in overall screen or in dielectric sheath.

The cable bundle configurations are extremely variable, and

are installed inside the aircraft. Nearly 25 different installation

typologies are schematized.

Examples of complex bundles

Troubleshooting Wiring Problems

Trouble shooting Wiring is a maintainer’s worst nightmare.

It is not unusual to take several hours to find intermittent

shorts and opens in aircraft wiring.

The process usually requires a cart full of electronic

equipment, extensive traning and years of on the job

experience.

Records in 1988 show that Navy maintainers spent over

240,000 hours troubleshooting wiring problems for the

fleet of F14 aircraft.

Wiring problems are known to be a significant portion of

aircraft maintenance costs.

Safety Concerns

Shorts, arcing, opens circuits, or intermittent problems are

a real flight safety concern.

Sandia National Laboratory scientists have shown that

build up of sulfur on wiring from immersion in jet fuel could

have ignited the fuel tank vapors in the Trans World Airlines

800 disaster.

The Navy has a special team working on use of inert gases

to put out fires caused by wiring arc tracking. Open circuits

or arcing can result in inadvertent mid-air actuation of flaps

or retracted landing gear.

The spurious signals also present a major problem in

diagnosing whether a system is failed or the wiring is

deteriorated causing spurious signal conditions.

Sviluppo di tecniche di diagnostica

per individuare la presenza di

guasti e difetti sui cablaggi a

bordo di aeromobili

The FAA’s Aging Aircraft Systems responds to a February 1997

recommendation by the White House Commission on Aviation

Safety and Security, chared by Vice President Al Gore.

“The White House Commission specifically recommended that the

FAA work in cooperation with airlines and manufacturers to expand

the FAA’s aging aircraft program to include a variety of systems”,

e.g. “electrical wiring, connectors, wiring harnesses, and cables”.

(Washington D.C. 10.01.98)

FAA “Aging Transport Systems Rulemaking Advisory

Committee” (ATSRAC) - Wiring Group: wire diagnostics, smart

wire, arc fault circuit breakers.

IL TEMA DI RICERCA A LIVELLO

INTERNAZIONALE

Il National Transportation Safety Board (NTSB) degli

Stati Uniti raccomanda lo sviluppo di nuove

tecnologie che consentano la diagnostica continua

dello stato di “salute” del cablaggio e cioè durante il

volo e non solo come attualmente avviene nelle

operazioni di manutenzione.

Prove a bordo

dell’Airbus 321 Alitalia

Notes: O=Open; S=Short; D=Defect

Conductor AWG Cable Test

or Size Jacket/Sheath Impedance Application (*)

Basic Cores (ohm)

Nickel Plated Copper

Spiral Shield

Nickel Plated Copper

Spiral Shield

ShieldType

SJ 1 CF 22

SJ 20

/

/1 CF

Insulation

/

/

PI Tape+FEP

PI Tape+FEP

O/S

O/S

Airframe Wiring

Airframe Wiring

Only the use of the portable scalar analyser is possible

The choice of the central frequency and span is critical

Pannello

Cabina Vano Bagagli

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

0,0

0

1,4

8

2,9

7

4,4

5

5,9

3

7,4

2

8,9

0

10,3

8

11,8

7

13,3

5

14,8

3

16,3

2

17,8

0

19,2

8

20,7

7

22,2

5

23,7

3

25,2

2

26,7

0

28,1

8

29,6

7

31,1

5

32,6

3

34,1

2

35,6

0

37,0

8

38,5

7

40,0

5

41,5

3

43,0

2

44,5

0

m

db

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

0,0

1

1,3

6

2,7

2

4,0

7

5,4

3

6,7

9

8,1

4

9,5

0

10,8

6

12,2

1

13,5

7

14,9

2

16,2

8

17,6

4

18,9

9

20,3

5

21,7

1

23,0

6

24,4

2

25,7

7

27,1

3

28,4

9

29,8

4

31,2

0

32,5

5

33,9

1

35,2

7

36,6

2

37,9

8

39,3

4

40,6

9

m

db

SJ22

(12,45 m)

Fmax=106 MHz

Fmax=164 MHz

-43 dB

-22 dB

Alitalia Airbus 321

Cable no.1

Cable no.2

Open ended cable no.1

-80

-60

-40

-20

0

0 5 10 15 20 25

Distance [m]

Refl

ecti

on

co

eff

. [d

B]

Effective distance from OE termination: 10 m

Measured distance from OE termination: 9.72 m

Central Frequency = 36.16 MHz

Span = 137.28 MHz


-80

-60

-40

-20

0

0 5 10 15 20 25 30 35

Distance [m]

Re

fle

cti

on

co

eff

. [d

B]

Effective distance from OE termination: 14.5 m


Central Frequency = 10 MHz

Span = 163.45 MHz

Alitalia Airbus 321

Cable no.3 Cable no.4

-80

-60

-40

-20

0

0 10 20 30 40 50

Distance [m]

Refl

ecti

on

co

eff

. [d

B]


Effective distance from OE termination: 18 m



Span = 73.2 MHz

-80

-60

-40

-20

0

0 10 20 30 40 50 60

Distance [m]

Refl

ecti

on

co

eff

. [d

B]


Effective distance from OE termination: 18.8 m



Span = 73.2 MHz

Critical aspects

• Testing of cable sections with interconnection connectors

• Testing of single core unshielded cables

• Effect of the bundle on the cable under test

• Use of the reference return cable

• Use of the reference measurement of the undamaged cable

• Post processing of the measured data for fault location

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

0,0

0

1,2

5

2,5

1

3,7

6

5,0

1

6,2

7

7,5

2

8,7

7

10,0

3

11,2

8

12,5

3

13,7

9

15,0

4

16,2

9

17,5

5

18,8

0

20,0

5

21,3

1

22,5

6

23,8

1

25,0

7

26,3

2

27,5

7

28,8

3

30,0

8

31,3

3

32,5

9

33,8

4

35,0

9

36,3

5

37,6

0

m

db

disconnessi connessi

R&S FSH3:

Frequenza Centrale= 58 MHz

Span = 96 MHz

SJ20(8,12m) SJ20(10,68m)

SET-UP VNA

Modalità Low Pass Step

Formato Real

CARATTERISTICHE DEL CAVO (tripolare non schermato)

Lunghezza totale 1,385 m

Distanza dal guasto 0,93 m

Vf 0,828

MISURE ESEGUITE

X0 Cavo integro

X1 2 mm di guaina

X2 2 mm di schermo

X3 4 mm di schermo

Coefficiente di Autocorrelazione

N° di punti dell’intervallo 80

Ritardo temporale τ 2

Coefficiente di Correlazione Statistica


Prove di laboratorio su cavo JN1018 SK 004


Misure Riflettometriche

Postprocessing delle misure riflettometriche


Risultato delle elaborazioni statistiche in funzione degli obiettivi proposti


SET-UP VNA

Modalità Low Pass Step

Formato Real

CARATTERISTICHE DEL CAVO (tripolare schermato)


Distanza dal guasto 1 0,54 m

Distanza dal guasto 2 1,045 m

Vf 0,741

MISURE ESEGUITE

X0 Misura di riferimento

X1 Misura con i due guasti


N° di punti

dell’intervallo

100



N° di punti

dell’intervallo

250


guasto 1 guasto 2

Misure RiflettometrichePostprocessing delle misure riflettometriche


SET-UP VNA

Modalità Low Pass Impulse

Formato Log Mag

CARATTERISTICHE DEL CAVO (tripolare non schermato)


Distanza dal guasto 0,93 m

Vf 0,828

MISURE ESEGUITE

X0 Cavo integro

X1 2 mm di guaina

X2 2 mm di schermo

X3 4 mm di schermo







Misure Riflettometriche

Postprocessing delle misure riflettometriche

SET-UP VNA

Frequency range 30 kHz- 1000 MHz

CABLE CHARACTERISTICS

Total length 2,80 m

Distance from fault 1,2 m

Velcity factor 0,72

Propagation time to

fault

12 nS

Cable under test:

(M22759/3416)diametro int.:1,3 mm ; diametro est.:2 mm

;

Reference return cable:

(48T10C01G020)diametro int.:1mm ; diametro est.:1,4 mm

;

TESTS PERFORMED

x0 Undamaged cable

x1 30% of cable section broken



Single core unshielded cable inside a cable bundle with

reference return cable

0 5 10 15 20 25 30-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6Misure

tempo [nS]

coeff. riflessio

ne

x0x1x2x3

8 9 10 11 12 13 14 15 16

-0.06

-0.04

-0.02

0

0.02

0.04

0.06

0.08

0.1

Misure

tempo [nS]

coeff. riflessio

ne

x0x1x2x3

cable end

Measurement

Difference with respect to the reference

measurement of the undamaged cable

0 5 10 15 20 25 30-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

0.04Differenza tra le misure

tempo [nS]

coeff. corr

ela

zio

ne

(x1-x0)(x2-x0)(x3-x0)

fault

Post processing of the difference with respect to the reference measurement of

the undamaged cable

0 5 10 15 20 25 30-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8(Differenza*Correlazione) tra le misure

tempo [nS]

corr

ela

zio

ne m

odific

ata

(x1-x0)(x2-x0)(x3-x0)

Fault

localization

post

pro

cess

ed d

ata

fault localization at 12 ns !

Presentazione di PowerPoint hazards on... · 2014-03-13 · • La presenza del terreno •...

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Transcript of Presentazione di PowerPoint hazards on... · 2014-03-13 · • La presenza del terreno •...