What happened
On 12 December 2014, an Emirates A380-861, registration A6-EDD, was undergoing scheduled maintenance at the engineering hangar of Dubai International Airport. Following successful engine ground runs, the aircraft was being moved to a hangar for further work. During the process of switching external electrical power from the APU to the ground power supply, a flashing light was observed accompanied by smoke emerging from the lower avionics compartment, situated beneath the cockpit.
Upon investigation of the source, technicians discovered that a remote control circuit breaker (RCCB) within the primary electrical power distribution center (PEPDC) had melted and burnt.
The investigation
The UAE Air Accident Investigation Sector (AAIS) conducted an inquiry into the electrical failure. The investigation focused on the condition of the PEPDC and the specific circuit breaker, identified as RCCB 991JV6. Investigators examined the hardware design, maintenance records, and the presence of any contaminants within the electrical compartment.
Technical analysis revealed that the aircraft was equipped with an older version of the PEPDC fluid protection system. The investigation also reviewed maintenance logs, noting that while no fluid leaks had been previously reported for this airframe, a recent maintenance task for dust prevention had only recently been introduced into the maintenance planning document.
Findings
- The primary cause of the smoke and component melting was a short circuit occurring between phases B1 and C1 of the RCCB.
- This short circuit was triggered by a significant buildup of a mixture of dust and conductive fluid.
- The fluid, likely originating from a leak in the aircraft's toilet or sink systems, had bypassed the protection umbrella due to deteriorated seals.
- The design of the RCCB left certain phase screws exposed, providing a surface for dust and fluid to collect.
- Ventilation airflow within the PEPDC directed air—and potentially airborne particles—directly toward the vulnerable circuit breaker.
Safety action
Following the investigation, several safety measures were implemented:
- Airbus introduced new maintenance tasks for the visual inspection of the PEPDC to prevent dust accumulation.
- Emirates conducted a fleet-wide inspection of its 57 A380 aircraft to check for similar fluid traces and contamination.
- The operator reduced the interval for electrical circuit inspections from 72 months to 24 months to mitigate risks from environmental contaminants.