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Examination of damaged wing leading edge wiring:
Airbus Industrie A320 Aircraft

 

1. Introduction

3. Analysis & Conclusions


FACTUAL INFORMATION

Introduction

A selection of individual bundles of twisted pair electrical wires (figure 1) removed from the right wing leading edge of an A320 aircraft were received for the characterisation of damage to the wiring insulation.

Wiring Bundle

Figure 1: Wiring Bundle

While numerous wiring bundles were received, only five were identified with respect to their installed location. For the purposes of correlating damage characteristics to the wire path, only those identified bundles were subject to study. Diagrams and photographs showing the wire and damage locations were presented to assist with the investigation.

The wiring bundles examined were as follows (all from raceway ‘1S’):

Wire Identification Damage Location Wing Pos’n  



 
2793 – 4537 – Blue 18 inches outboard from R/H engine pylon plug 4018VC 1  



 
2793 – 4537 – Red 4 feet inboard from wingtip plug 4054VC 4  



 
2793 – 4535 – Red 10 feet outboard from R/H engine pylon plug 4018VC 2  



 
2793 – 4535 – Blue 15 feet outboard from R/H engine pylon plug 4018VC 3  



 
2793 – 4533 – Blue 15 feet outboard from R/H engine pylon plug 4018VC 3  



 
2793 – 4549 – Red 18 inches inboard from wingtip plug 4054VC 5  



 
2793 – 4549 – Blue Alongside the red wire above
5
 

Damage locations

Figure 2: Damage locations

 

EXAMINATON

Visual Examination

The damaged areas of each wire strand previously identified were studied under the low power stereomicroscope.

2793 – 4537 – Blue

This wire displayed a broad area of flat, tapering damage, consistent with rubbing against a flat surface at a shallow angle. The damage extended through to the inner insulator (figure 3). No related damage to the adjacent red wire was noted, however there was a small sliver of shaved or lifted insulation approximately two millimetres away.

Damage to the inner insulator of the 2793-4537 Blue wire

Figure 3: Damage extending to the inner insulator

2793 – 4537 – Red

Both blue and red wires at this location showed sharp, angular notches consistent with pressure against a rigid corner or similar (figure 4). Some shaving and lifting of the red wire outer insulation was shown, as was a set of parallel, much less extensive indentations (arrowed) roughly 3mm from the main damage marks.

Sharp angualr notches

Figure 4: Sharp angular notches

2793 – 4535 – Red

This wire showed another extended and tapering flat area of damage – in this case extending for around 3mm. The inner insulating material had been exposed for around half of this distance (figure 5). No related marks were noted on the blue wire.

Exposed inner insulating material

Figure 5: Exposed inner insulating material

2793 – 4535 – Blue

Again, this wire showed the characteristic angled edge rubbing features - in this case just contacting the inner insulation (figure 6). A profile view showed the acute angle of the indentation and the radius around the corner of the indenting object (figure 7).

Angled edge rubbing features

Figure 6: Angled edge rubbing damage

Acute angle of the indentation

Figure 7: Acute angle of the indentation (arrowed)

2793 – 4533 – Blue

This wire was the most severely damaged of the selection studied, with exposure of the copper conductor over roughly half a millimetre (figure 8). The damage profile was similar to most previously examined wires, with the shallow angular face clearly shown. Some flattening of the red wire insulation was also noted around ten millimetres from the main damage point (figure 9).

Exposed copper conductor

Figure 8: Exposed copper conductor

Flattening of the red wire insulation

Figure 9: Flattening of the red wire insulation

2793 – 4549 – Red
2793 – 4549 – Blue

These two areas were alongside to each other and were similar in terms of their sharp intrusive profile. While not the type of cuts produced by a knife or similar, these notches were clearly produced by a sharp rigid edge (figures 10 & 11). With the red wire, some lifting of the insulation had also occurred, disclosing the inner sheath. Around 15mm away, a similar set of notches was also shown by both red and blue wires, however these were less significant and had not exposed the inner insulator (figure 12).

Notches due to sharp rigid edge

Figure 10: Notches due to sharp rigid edge

Notches due to sharp rigid edge

Figure 11: Notches due to sharp rigid edge

Notches

Figure 12: Similar less extensive damage - 15 mm away from the main area

Harpoon Tie

Studying an unused harpoon tie of the type used to secure the wiring within the raceways showed both the central tongue and outer plate to have rigid flat surfaces with rounded edges. The form and dimension of these features was consistent with the flat, rubbing type damage experienced by some of the wires.

Harpoon tie assembly

Figure 13:Typical harpoon tie assembly used for securing wiring within raceways

Next section...

1. Introduction
2. Examination
3. Analysis & Conclusions

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  Updated 6 June 2001
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