What happened
On February 6, 2016, during ground maintenance operations at Warsaw Chopin Airport (EPWA), a short circuit occurred in the connection plug of an external ground power source. The incident took place approximately 30 minutes after the plug had been connected to the Airbus A320. The sequence of events and the resulting impact were identical to a previous incident that occurred at the same parking stand on January 16, 2016. No injuries were reported among the ground personnel, and no damage was sustained by the aircraft's electrical systems.
Although no precipitation had been recorded in the hours preceding the event, a maintenance mechanic noted the presence of moisture on both the aircraft's receptacle and the ground power plug. Following the incident, the airport authority decommissioned the specific parking stand from service.
The investigation
The PKBWL investigation examined the operational history of the parking stand, noting it had been used 19 times without failure between the two incidents. The investigation confirmed that the personnel responsible for connecting the 400 Hz ground power sources were properly qualified and that their training materials were adequate.
While the airport's technical staff performed routine checks during every shift change, the investigation found that the manufacturer's manual for the power equipment lacked specific instructions for daily maintenance, leading to potential variations in how inspections were performed. Furthermore, while a third-party contractor was responsible for periodic maintenance of the power units, the investigation could not find specific maintenance logs or checklists confirming that the equipment at this particular parking stand had been serviced according to the manufacturer's guidelines.
Findings
- The investigation could not definitively determine the exact cause, but the unnoticed presence of moisture or contamination on the ground power plug was identified as the most probable cause.
- There was a lack of documented evidence (logs or checklists) confirming that periodic maintenance had been performed on the specific power supply unit involved in the incident.
- The ambiguity in the manufacturer's technical instructions regarding daily maintenance tasks contributed to inconsistent inspection practices.
Safety action
Following the incident, several preventive measures were implemented by the airport authority, including:
- Developing internal instructions and procedures to improve oversight of the 400 Hz installation.
- Defining specific daily maintenance tasks and creating standardized checklists for technical staff.
- Increasing supervision of third-party contractors regarding their service activities and qualifications.
- Enhancing the verification of documentation related to periodic maintenance.
- Introducing additional physical tags (PIT) to alert personnel to equipment failures.
- Strengthening training programs to emphasize the hazards associated with using contaminated or moist ground power plugs.