Incident Description
On 31 March 2015, a Bombardier DHC-8-400 aircraft was on approach to Krakow Airport (EPKK). During configuration change to flaps 15, the flap movement stopped near the 10-degree position. The Master Caution warning activated along with the "FLAP POWER" caption on the Crew Warning Panel. The crew aborted the approach and executed a go-around. They did not declare an emergency but requested five minutes to perform the appropriate procedure.
Crew Actions
The crew performed the "FLAP POWER" checklist, which included resetting the flap control controller. The error warning disappeared and flap control was restored. After reporting ready for approach, the crew landed without further issues in Krakow.
Previous Occurrence
The same aircraft had experienced a similar flap indication problem on 19 March 2015. Ground tests were conducted but no definitive cause was found.
Investigation Findings
On 31 March, the malfunction occurred during the described flight and also on another flight that day during acceleration after takeoff (the last flight of the day). A thorough check of the entire flap control system and continuity of all connections was performed. Water was found in connector 2752P23 at the Flap Power Unit. The connector was dried, and tests were conducted (procedure 27-52-00-720-801 rev. 19).
Probable Cause
The cause of the incident was water in the electrical connector at the Flap Power Unit.
Preventive Actions
The operator's maintenance performed a check of the entire flap control system and continuity of all connections. Water was found in connector 2752P23 at the Flap Power Unit. It was dried and tests were conducted (27-52-00-720-801 rev. 19).