What is SC on Airbus A320? (Single Chime)

Single Chime (SC) is a crucial alert system on the Airbus A320 aircraft that is designed to provide audio signals to the pilots and cabin crew. It is part of the aircraft’s comprehensive warning and notification system, ensuring effective communication between the various systems and personnel on board.

The Single Chime plays an essential role in notifying the flight crew about specific events or conditions during various phases of flight. This simple yet effective audio signal is known for its distinct sound and is recognized by experienced aviators around the world.

The Functions of Single Chime

The Single Chime on the Airbus A320 serves multiple functions, each indicating a different event or situation. Let’s explore some of its key functions:

Cabin Crew Call

One of the primary purposes of the Single Chime is to indicate a cabin crew call. When a passenger requests assistance or when the flight crew needs to communicate with the cabin crew, they use the interphone system. Activating this system triggers a single chime, alerting the cabin crew that their attention is required in the flight deck or the cabin.

The Single Chime serves as a reminder for the cabin crew to promptly respond to the call, ensuring efficient coordination and communication between the flight crew and the cabin crew. This helps in providing a safe and comfortable travel experience for the passengers.

Master Caution Warning

An important function of the Single Chime is to indicate a master caution warning to the flight crew. This warning is activated when a non-normal condition or system malfunction is detected on the aircraft. Examples of such conditions include low fuel, open doors, or engine abnormalities.

Upon hearing the Single Chime, the flight crew is alerted to check the caution messages displayed on the central warning panel (CWP) located on the overhead panel. The CWP presents important information related to the abnormal condition, allowing the crew to take appropriate actions to address the issue.

Passenger Seatbelt Sign

The Single Chime also plays a vital role in signaling the activation or deactivation of the passenger seatbelt sign. When the seatbelt sign is turned on or off, a single chime is played throughout the cabin, notifying the passengers to fasten or unfasten their seatbelts accordingly.

This is especially important during critical phases of flight, such as takeoff and landing, where it is necessary for passengers to be securely seated with their seatbelts fastened. The Single Chime helps in ensuring compliance with safety regulations and promoting a safe travel environment.


The Single Chime system on the Airbus A320 is a crucial component of the aircraft’s alerting system, providing audio signals to the flight crew and cabin crew for effective communication and coordination. From cabin crew calls to master caution warnings and passenger seatbelt sign activations, the Single Chime plays a significant role in ensuring the safety and comfort of everyone on board.

For More: What is TK on Airbus A320? (Tank, Track Angle)