Incident Overview
On 6 February 2016, during routine ground handling of an Airbus A320 at Warsaw Chopin Airport (EPWA), a short circuit occurred in the connector plug of the external 400 Hz ground power source. The short circuit happened approximately 30 minutes after the plug was connected to the aircraft's power receptacle. No injuries were reported among personnel, and there was no damage to the aircraft's electrical systems.
Investigation Findings
Investigators determined that the same parking stand had experienced an identical incident on 16 January 2016 (reference number 92/106). In the hours preceding the event, no precipitation (snow or rain) had been recorded. However, a maintenance mechanic's note made immediately after the incident indicated moisture on the aircraft's installed connector and on the plug itself. The parking stand was subsequently taken out of service by the airport's technical services.
Between 16 January and 6 February, the stand had been used 19 times without any issues. Checks on the qualifications and training of personnel connecting ground power showed no irregularities. The training materials were deemed adequate. Maintenance of the power equipment was contracted to an external company, and periodic inspections were confirmed via protocols. However, no protocol or checklist specifically verifying maintenance at the stand in question could be produced.
Daily inspections of the system were the responsibility of the airport's technical staff. Reports from the shifts before both incidents showed no system malfunctions. The manufacturer's maintenance instructions for daily inspections lacked specific descriptions, allowing varied interpretation.
The worker who connected the power stated that he checked the plug twice for moisture or contamination before connecting. CCTV footage could not verify this because the stand was not under surveillance.
Since both incidents involved the same aircraft, the operator was asked whether the aircraft's condition could be a factor. The operator responded that the aircraft was fully serviceable and had no history of similar issues with ground power.
Similar Event
The incident on 6 February was identical in sequence and outcome to the one on 16 January, occurring on the same parking stand and with the same aircraft.
Preventive Measures
Following the investigation, the airport implemented several preventive measures: preparation of internal instructions and procedures for supervising the 400 Hz installation; definition of daily inspection tasks with checklists; increased oversight of the subcontractor performing periodic maintenance; enhanced documentation control after maintenance; addition of warning tags (PIT) on faulty ground power equipment; and increased emphasis in personnel training on the hazards of using contaminated power plugs.
No safety recommendations were issued.