What aircraft was involved and where did it happen?

The accident on 2016-12-16 involved a DE HAVILLAND CANADA, Dash 8 (400), at TMA Kraków, PL.

Pressurization Failure Prompts Return to Kraków for DH8D

On December 16, 2016, a DE HAVILLAND CANADA, Dash 8 (400) was involved in an aviation accident near TMA Kraków, PL. Investigators recorded the probable cause as: The probable cause determined by the investigation was a Cabin Pressurization Controller (CPC) error. This summary draws on records from the Polish State Commission on Aircraft Accidents Investigation (PKBWL).

On 16 December 2016, a DH8D aircraft departing Kraków experienced a pressurization failure during climb. The crew performed the pressurization failure checklist but could not resolve the issue, returning to land safely. No injuries reported. Probable cause: Cabin Pressurization Controller error.

Incident Overview

On 16 December 2016, a De Havilland Canada DHC-8-400 (DH8D) aircraft experienced a pressurization issue shortly after departure from Kraków Airport (Balice). The crew reported the problem and returned to the departure airport for a safe landing. There were no injuries among the 27 occupants.

Sequence of Events

At 06:19 UTC, after takeoff from Kraków, the crew requested to level off at FL100. During the climb, while performing the after-takeoff procedures, they discovered that the cabin pressurization was not operating correctly. The crew executed the "PRESSURIZATION FAILURE" checklist but did not achieve the desired effect. At 06:26 UTC, they advised Kraków Approach Control of their intention to return to the departure airport. They subsequently performed an ILS approach to Runway 25 and landed at 06:40 UTC.

Upon landing, ground maintenance personnel conducted a test of the pressurization system, which passed successfully, and the aircraft was returned to normal service. The flight data recorder (FDR) did not capture cabin pressure or pneumatic system parameters, only bleed valve positions. Initially, the bleed valves were in the NORM position, and about two minutes into level flight at FL100, they were set to MAX, consistent with the pressurization failure checklist. The bleed valves remained in MAX for the next seven minutes.

Investigation Findings

The investigation identified three possible causes for the pressurization issue: a malfunction of the pack valve or shut-off valve, a fault in the cabin pressurization controller (CPC) or electronic control unit (ECU), or a problem with the cargo door inflatable seals. The cargo door seal issue was considered unlikely as no such indication was present, confirmed by the captain. The FDR recorded no Master Warning or Master Caution from takeoff until the return to Warsaw. After landing, ground maintenance performed a reset of the cabin pressure controller, which restored normal operation.

Probable Cause

The probable cause of the incident was determined to be a fault in the Cabin Pressurization Controller (CPC).

2016-12-16: DE HAVILLAND CANADA, Dash 8 (400) — TMA Kraków, PL