Incident Overview
On January 13, 2017, at Cologne Bonn Airport (EDDK), an ATR72 aircraft was departing and climbing to flight level 160 (FL160) toward waypoint DIK. While passing through FL140, the crew received a Master Warning indicating "EXCES CAB ALT" (excessive cabin altitude).
Crew Actions
The flight crew identified the malfunction, discontinued the climb, and descended to FL100. They performed the procedures specified in the Quick Reference Handbook (QRH). Unable to resolve the cabin pressurization issue, they decided to return to EDDK.
Casualties and Damage
No injuries were reported among the two persons on board (both crew members). The aircraft sustained no damage.
Investigation Findings
The investigation determined that the incident was caused by a crew error: the overspeed bleed valve (OVBD Valve) switch, which regulates pressure between the aircraft interior and the external environment, was left in the "FULL OPEN" position. No safety recommendations were issued by the investigation commission.
Operator's Preventive Actions
The operator briefed flight personnel on the circumstances and sequence of the event.