What happened
On January 13, 2018, a Bombardier Learjet 60, operated by AMC Aviation Sp. z o.o., was performing a flight from Modlin Airport (EPMO) to Nice (LFMN). After completing takeoff procedures and climbing above flight level 100, the first officer attempted to increase the cabin temperature by adjusting the temperature control knob to the 12 o'clock position. However, the cabin temperature indicator failed to reflect the heat being supplied to the cabin, remaining stuck at a value of "0."
The crew attempted to rectify the reading by switching between automatic and manual modes, but these efforts were unsuccessful. Due to the inability to monitor or control the cabin environment, the crew decided to return to the departure airport. The captain requested a descent and approach to Modlin to burn off fuel, ensuring the aircraft remained below its maximum landing weight (MLW). The aircraft landed at EPMO without incident after approximately 40 minutes of flight.
The investigation
Following the landing, maintenance personnel inspected the aircraft and discovered a loose wire. This disconnected connection was identified as the source of the malfunction in the cabin temperature control system. After the loose connection was repaired, the aircraft was released from maintenance service, and subsequent flight tests confirmed that the temperature indicator was functioning correctly.
Findings
- The primary cause of the incident was a lack of electrical continuity in the Cabin Temp. Controller power supply wire.
- The specific reason for the disconnection of the wire could not be determined.
- Atmospheric conditions at the time of the incident had no impact on the event.