Incident Summary
On December 4, 2017, at approximately 19:23 UTC, an Embraer 170-100 aircraft departed from Warsaw Chopin Airport (EPWA) on a scheduled flight to Paris Charles de Gaulle Airport (LFPG). The aircraft was dispatched in accordance with the Minimum Equipment List (MEL) with the BLEED2 system inoperative (MEL 36-00-00).
Flight Details
Takeoff and initial climb proceeded without issues. After transiting a cloud layer in icing conditions at around FL100, the crew received a BLEED 1 LEAKAGE caution, followed by an A-I WING FAIL indication. The crew requested air traffic control to stop the climb at FL140 and performed the appropriate Quick Reference Handbook (QRH) procedures. The situation was discussed with the Maintenance Control Center (MCC) via radio.
Due to a malfunction of the number 1 Nacelle Pressure-Regulating Shutoff Valve (NAPRSOV), combined with the already inoperative number 2 valve, the crew decided to return to Warsaw. The landing was completed without further incident.
Technical Issues
The valve malfunction was a known issue to the aircraft manufacturer. A service bulletin was planned for the fourth quarter of 2018 to introduce a modified NAPRSOV design incorporating additional vibration damping mass and an isolator to improve valve lifespan.
Investigation Findings
The operator's technical department was requested to analyze the defect. The number 1 valve defect recurred several times until it was replaced on February 9, 2018. The abnormal valve operation—intermittent opening and closing—was attributed to engine-induced vibrations.
The incident was recorded in the operator's Safety Management System (SMS) database, classified per operator criteria, and included in safety performance indicators (SPI).
Probable Cause
Faulty valve design causing pressure fluctuations.
Preventive Actions
The operator recommended the earliest possible introduction of the modified valves. The investigation commission did not issue any safety recommendations.