Aviation occurrence briefs

Heat damaged wiring loom involving Boeing 737-476F, Brisbane Airport, Qld, on 6 September 2018

Status: Completed
Investigation completed


Occurrence Briefs are concise reports that detail the facts surrounding a transport safety occurrence, as received in the initial notification and any follow-up enquiries. They provide an opportunity to share safety messages in the absence of an investigation.

What happened

On 6 September 2018, a Boeing 737-476 freighter was in the hanger at Brisbane Airport, Queensland undergoing routine maintenance. The crew reported that the cockpit voice recorder (CVR) was not testing and the circuit breaker was tripping.

While engineers were conducting troubleshooting on the aircraft, they discovered a heat damaged wiring loom located in the aft[1] lower cargo hold ceiling, adjacent to the CVR mount rack. The wires were severely burnt in a localised area with melted insulation and evidence of a possible fire. Engineers suspect this may have been caused by swarf[2] damaging the wiring and causing it to arc. Swarf ingress in the wiring loom was discovered from previous cargo conversion work.

Figure 1: Heat damaged wiring loom

Figure 1: Heat damaged wiring loom. Source: Operator’s engineering department

Source: Operator’s engineering department

Safety message

This incident highlights the importance of ensuring that while an aircraft is in maintenance, that all aircraft components are checked thoroughly to ensure proper functionality. When conducting any work on an aircraft, it is also vital to ensure that all areas are thoroughly cleaned to ensure no debris is left behind, as it may cause faults to the aircraft and its systems.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.



  1. Aft - situated in or near the rear of the aircraft
  2. Swarf - chips of metal, wood or plastic.
General details
Date: 06 September 2018   Investigation status: Completed  
Time: 2100 EST    
Location   (show map): Brisbane Airport    
State: Queensland    
Release Date: 11 January 2019   Occurrence category: Serious Incident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer The Boeing Company  
Aircraft model 737-476F  
Type of operation Air Transport High Capacity  
Sector Jet  
Damage to aircraft Minor  
Last update 11 January 2019