What happened
On April 13, 2015, a Bombardier Canadair CL-300, operated by Jet Story sp. z o.o., experienced a technical issue shortly after takeoff within the Warsaw TMA (EPWA). While the crew was performing the after-takeoff checklist, a non-normal cyan-colored message, "PROX SYS FAULT," appeared on the flight deck displays.
Following standard procedures, the crew executed the specific checklist for the proximity system fault. Although all landing gear indicators confirmed the gear was in the retracted position, the crew elected to halt their climb at FL380 and enter a holding pattern. After consulting with the operator's technical department, the crew decided to return to Warsaw Chopin Airport. The crew notified Air Traffic Control of their intention to return, explicitly stating that the situation was not an emergency. The aircraft landed safely without further incident.
The investigation
The investigation, conducted by the operator, focused on the origin of the system fault message. Technical inspections performed by maintenance personnel following the landing identified a malfunction in the Proximity Sensor Electronic Unit (PSEU). The faulty component was replaced, and subsequent operations showed that the error did not recur.