ezap and ewis - aviation africa siasa... · siasa project this project is funded by the european...

SIASA project

This project is funded by the European Union and implemented by EASA.

TE.GEN.00409-001

EZAP and EWIS

Graeme Riddick Airworthiness Engineer Head of Structure and Systems installation certification Technology Evolution – Impact on Airworthiness 23-24 September 2014, Windhoek, Namibia

Ageing Aircraft - Wiring

CONTENTS

Historical background

Regulation status

Airbus implementation status

Enhanced logic – summary

A320 family EZAP implementation

Minimisation of maintenance burden

23-24 September 2014 Technology Evolution - Impact on Airtworthiness, Windhoek, Namibia 2

History

Safety concerns about wiring systems brought to public attention by a midair explosion in 1996 involving a B747-100 manufactured in July 1971


History

The NTSB conclusions included: Existing standards for wire separation may not provide adequate protection against damage from short circuits.

A short circuit producing excess voltage that was transferred to the center wing tank (CWT) fuel quantity indication system wiring is the most likely source of ignition energy for the CWT explosion.

The condition of the wiring system in the accident airplane was not atypical for an airplane of its age, and the airplane was maintained in accordance with prevailing accepted industry practices.

Until recently, insufficient attention has been paid to the condition of aircraft electrical wiring, resulting in potential safety hazards


History

In 1997 a White House commission requested FAA to expand their Aging Aircraft Program to include systems

FAA issued an Aging Systems Plan focussing, initially, on wiring systems. The Aging Transport Systems Rulemaking Advisory Committee (ATSRAC) was formed to provide FAA with advice and recommendations


History

An accident in September 1998 following an in-flight fire of an MD-11 manufactured in 1991


History

TSB Conclusions: A segment of in-flight entertainment network (IFEN) power supply unit cable (1-3791) exhibited a region of resolidified copper on one wire that was caused by an arcing event. This resolidified copper was determined to be located near manufacturing station 383, in the area where the fire most likely originated. This arc was likely associated with the fire initiation event; however, it could not be determined whether this arced wire was the lead event.

Examination of several MD-11 aircraft revealed various wiring discrepancies that had the potential to result in wire arcing. Other agencies have found similar discrepancies in other aircraft types. Such discrepancies reflect a shortfall within the aviation industry in wire installation, maintenance, and inspection procedures.


Regulation status

Aircraft ageing in general:

Introduction of a change to Part 21 to require TC and STC Holders to update their ICAs to take account of ageing aircraft/systems issues when they have been identified and agreed by the Agency.

EWIS NPA 2007-01 published in 2007 and adopted in 2008


Regulation status

Changes to CS 25

Introduction of a new subpart H

Including specific reference to ICA for:

Perform EZAP

Produce Electrical Standard Wire Practices Manual (ESWPM)

Wiring identification

Wiring separation

Electrical load analyses


Regulation status

Part M (Maintenance Requirements)

to require operators to include the output of EZAP into their maintenance programmes,

amend subpart D to reflect EWIS maintenance / inspection standards


Regulation status

Existing TC

Incorporation of a new CRI H-01 into existing TCDS

All changes to type design are now required to review the impact of the change on EWIS and update ICA when appropriate


Airbus is required Maintenance and inspection requirements for the EWIS developed with the use of an enhanced zonal analysis procedure (EZAP)

So what is EZAP?



Primary concern is the potential fire hazard

EZAP must identify tasks to minimize this potential

Two approaches

Minimize occurrence of ignition source

Minimize consequences of ignition source

The results must be realistic and any new tasks must not increase potential for new discrepancies



For each zone, application of the enhanced logic either:

Confirms that existing zonal inspection is adequate

or

Leads to identification of:

GVI (standalone) of some or all wiring in a zone

Detailed Inspections of some or all wiring in a zone

Restoration (cleaning) tasks to reduce likelihood of significant build-up of combustible materials


A320 EZAP Implementation


On-aircraft WG – Shannon, Ireland May 2005

A321-200 msn 1080 of DLH

8 operators – ANA, BAW, CIT, MON, NWA, SAS,TAP, UAL

3 Authorities – CAA, DGAC, FAA

111 dossiers

for

A320 family

WG used around 3100

photos of zones

3 aircraft other inspected prior to WG

(NWA msn 48, GFA msn 466 and CCM msn 548)


Number of tasks (For the A320 Family)


Interval (Months)

GVI DET RST Total

24 1 5 - 6

48 6 - 1 7

72 10 6 13 29

144 19 - 17 36

Total 36 11 31 78


A320 Zone 211/212

Area behind circuit breaker panel 121VU

(behind co-pilot)

Continuous air flow leads to dust accumulation

Cleaning recommended every 72 months



A320 Zone 127/128 - Feeder cables in avionics bay Existing Zonal Inspection every 48 months. Access to these cables requires galley / lavatory removal which is normally scheduled every 72 months.

Level upgraded to DET to avoid heavy access requirement at 48 months


Minimisation of maintenance burden

Maximum credit taken for existing Zonal Inspection Program to avoid dedicated tasks

Task intervals selected to coincide with Zonal Inspections

With few exceptions, new tasks will fit escalated 4C and 8C checks

No requirement to remove furnishings, galleys or lavatories earlier than already recommended

Need for cleaning tasks identified from examination of aircraft having at least 10 yrs in service


EZAP Output

The output of the EZAP is used to determine all the EWIS related ICA.

These tasks are implemented under the MRB process.

A compliance source document is delivered to the authorities listing sumarising EWIS related ICA in the various Airbus documents (MRBR, AMM, etc).


SIASA project

This project is funded by the European Union and implemented by EASA.

End slide

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