What happened
On July 15, 2018, a Cessna 560XLS was performing a climb from Warsaw Chopin Airport (EPWA) toward Manchester (EGCC). Upon reaching approximately FL150, the crew noted an increasing whistling noise originating from the lower left corner of the main door. Because the cabin pressurization system appeared to be functioning correctly at that time, the pilots elected to continue the climb.
However, once the aircraft reached its cruising altitude of FL400, the crew observed more frequent and prolonged cycles of the cabin altitude indicator compared to normal operations. During a secondary inspection of the area where the noise was first heard, the crew detected an airflow sensation near the main door. Consequently, the commander decided to return to EPWA, landing the aircraft safely without further incident.
The investigation
Following the landing, maintenance personnel conducted a cabin pressure leak test. The inspection successfully identified the source of the air escape: a deficiency in the sealant at the gasket mounting flange located at the bottom of the main door. To rectify the issue, technicians replenished the missing sealant and performed functional tests on both the main door gasket and the cabin pressurization system. The aircraft passed all subsequent tests.
Findings
- The primary cause of the incident was damage to the door gasket at the lower edge of the main door, specifically a loss of sealant at the mounting flange.