Incident Overview
On 15 July 2018, a Cessna 560XLS aircraft departed Warsaw Chopin Airport (EPWA) for Manchester Airport (EGCC) with three occupants onboard. During the initial climb, at approximately FL150, the crew noticed a gradually increasing whistling noise originating from the area of the lower left corner of the main cabin door. The cabin pressurization system was operating normally, so the crew decided to continue the climb.
In-Flight Observations
After reaching the cruising altitude of FL400, the pilots observed that the cabin altitude cycles (climb and descent) were occurring more frequently and lasting longer than usual. Upon re-examining the source of the noise, they detected a perceptible airflow in the same region near the main door. The commander then decided to abort the flight and return to Warsaw Chopin Airport. The aircraft landed without further incident.
Post-Flight Inspection
On the ground, maintenance personnel conducted a cabin pressurization test. The test identified an air leak at the lower part of the main door, caused by missing sealant at the mounting flange of the door seal. The missing sealant was replenished, and a functional test of the main door seal and the cabin pressurization system was performed. The test results were positive.
Findings
No injuries were reported among the three occupants. The aircraft sustained no damage.