What is TMR on Airbus A320? (Timer)

The Airbus A320 is a widely used commercial aircraft known for its reliability and advanced technology. One of the crucial components of the A320 is the Timer, abbreviated as TMR. The Timer plays a vital role in various aircraft systems, ensuring timely operations and contributing to the overall safety of the aircraft. In this article, we will explore the Timer on the Airbus A320, its functions, and its significance in maintaining smooth flight operations.

Functions of the Timer

The Timer on the Airbus A320 is responsible for monitoring and controlling several critical systems during flight. Its primary functions include:

1. Cockpit Voice Recorder (CVR) Duration Timer: The Timer ensures that the Cockpit Voice Recorder, which records all voice communications in the cockpit, operates for the maximum duration specified by aviation authorities. This duration typically ranges from two to four hours, depending on the regulatory requirements. The Timer starts counting as soon as the aircraft’s electrical power is supplied and stops when the power is turned off.

2. Flight Data Recorder (FDR) Duration Timer: Similar to the CVR Duration Timer, the Timer is responsible for monitoring the Flight Data Recorder’s recording duration. The FDR records various flight parameters such as altitude, speed, heading, and control inputs. Just like the CVR, the FDR has a specific recording duration, typically ranging from two to twenty-five hours. The Timer ensures that the recording duration remains within the mandated thresholds.

3. Auto Throttle Closed Loop Timer: The Auto Throttle system in the A320 controls the engine thrust based on the aircraft’s speed and altitude. The Timer is involved in monitoring the Auto Throttle’s closed-loop control system, which ensures accurate engine thrust adjustments. It measures the time interval between throttle commands and engine response, constantly adjusting to maintain optimal performance and fuel efficiency.

4. Flight Mode Annunciator (FMA) Timer: The Flight Mode Annunciator on the Airbus A320 displays the current mode of the flight control systems, such as takeoff, climb, cruise, descent, or approach. The Timer controls the timing functions of the FMA, indicating the duration of each mode and ensuring smooth transitions between them. The FMA Timer plays a crucial role in maintaining situational awareness for the flight crew.

5. Cockpit Door Unlock Timer: In the interest of enhanced security, the Airbus A320 is equipped with a cockpit door lock system. The Timer manages the timing functions related to cockpit door access, ensuring safe and controlled entry and exit procedures. It allows authorized personnel to gain access to the cockpit when required but imposes time restrictions to prevent unauthorized access.

Significance of the Timer

The Timer on the Airbus A320 is an essential component that enhances the safety, efficiency, and reliability of the aircraft. Its significance can be understood through the following aspects:

1. Safety: The Timer ensures the proper functioning of critical systems like Cockpit Voice Recorder and Flight Data Recorder. By accurately monitoring their recording durations, the Timer facilitates the retrieval of valuable information in the event of accidents or incidents. This data aids in accident investigations and improves overall aviation safety.

2. Compliance: Aviation authorities prescribe specific recording durations for the Cockpit Voice Recorder and Flight Data Recorder. The Timer ensures that the A320 complies with these regulatory requirements by controlling the recording duration. This enables the aircraft to meet legal obligations and ensures adherence to industry standards.

3. Performance: The Auto Throttle Closed Loop Timer plays a crucial role in optimizing engine performance. By continuously monitoring the timing between throttle commands and engine responses, the Timer enables precise control of engine thrust. This results in improved fuel efficiency, better flight performance, and enhanced passenger comfort.

4. Flight Control: The Flight Mode Annunciator Timer contributes to the smooth operation of the Airbus A320’s flight control systems. It ensures that the flight crew has accurate indications of the current flight mode, facilitating proper decision-making and seamless transitions between different phases of flight. This enhances the crew’s situational awareness and promotes effective flight management.

5. Security: The Timer’s involvement in managing the timing functions related to cockpit door access enhances the security protocols of the A320. By imposing time restrictions on cockpit door unlock procedures, the Timer prevents unauthorized access and ensures the safety of the flight deck. This feature contributes to the overall security measures implemented in modern commercial aviation.


The Timer on the Airbus A320, abbreviated as TMR, is a critical component that performs various timing functions across multiple systems. From monitoring the recording durations of the Cockpit Voice Recorder and Flight Data Recorder to optimizing engine thrust control, the Timer ensures smooth flight operations and enhances the overall safety of the aircraft. Its role in managing the timing functions related to flight mode annunciator and cockpit door access further contributes to the efficiency and security of the A320. As aviation technology continues to evolve, the Timer remains an integral part of Airbus aircraft, enabling reliable and precise operation.

For More: What is FPV on Airbus A320? (Flight Path Vector)