Incident Overview
On 29 April 2017 at 08:12 UTC, the crew of a Boeing 737-800 was conducting a departure from runway 27 at Katowice Airport (EPKT) on a scheduled flight to Ben Gurion Airport (LLBG). During the takeoff roll, at a speed between 80 knots and V1 (110 knots), a Takeoff Configuration Warning sounded in the cockpit, indicating the aircraft was not properly configured for takeoff. The crew rejected the takeoff and taxied safely to the first available taxiway.
Post-Flight Findings
While taxiing, the trailing edge (TE) flaps indicator showed an asymmetry: left flap at -5° and right flap above 5°. This asymmetry had not been present before the takeoff roll. After the crew selected the flaps to the UP position, the flaps remained extended (left at -1°, right at -1.5°). The captain decided to return to the apron.
After parking, the captain made an entry in the technical log and handed the aircraft over to maintenance personnel.
Maintenance Actions
Maintenance performed an operational test of the Flap Slat Electronic Unit (FSEU), which detected an error with FLAP SKEW sensor number 6. The faulty sensor was replaced, along with the flap position indicator. The flap extension system was retested and found to be serviceable. The aircraft was released for further operation.
Cause
The incident was caused by a malfunction of the FLAP SKEW sensor number 6 in the flap extension system.
The investigating body issued no safety recommendations.