What is SPD LIM on Airbus A320? (Speed Limit)

When it comes to aviation, speed is a crucial factor. Every aircraft has its own speed limits, which are determined by a variety of factors including safety, performance, and regulations. In the case of the Airbus A320, an immensely popular narrow-body aircraft, the speed limit, also known as the SPD LIM, plays a vital role in ensuring the aircraft operates within safe parameters. In this article, we will explore the speed limits on the Airbus A320 and how they are managed.

Understanding the Speed Limit on the Airbus A320

The speed limit on the Airbus A320 is primarily regulated by two important factors: the Maximum Operating Mach Number (Mmo) and the Maximum Operating Speed (Vmo). Mmo refers to the maximum Mach number that the A320 can safely fly at various altitudes. Mach number is a dimensionless unit used to measure the speed of an aircraft relative to the speed of sound. On the other hand, Vmo represents the maximum indicated airspeed that the A320 should not exceed under normal flight conditions. By adhering to these speed limits, pilots can ensure the safety and structural integrity of the aircraft.

The Mmo for the Airbus A320 is 0.82, although this value may vary depending on specific aircraft configurations and the airline in question. This means that the A320 should not exceed 82% of the speed of sound. The actual speed of sound can vary based on factors such as temperature and altitude. It is important for pilots to closely monitor their aircraft’s performance and adjust their speed accordingly to stay within the safe Mmo limits.

Additionally, the Vmo for the Airbus A320 is typically 350 knots indicated airspeed (KIAS) or Mach 0.82, whichever is lower. This provides a clear margin for aircraft performance and structural limitations. It’s worth noting that the Vmo may also be influenced by other factors such as altitude, temperature, and aircraft weight. During flight, pilots rely on their aircraft’s instruments and flight management system to ensure they are operating within the prescribed speed limits.

Managing Speed Limits on the Airbus A320

Pilots on the Airbus A320 have several tools at their disposal to manage speed limits and keep their aircraft within the designated parameters. One such tool is the Autothrust System, which automatically adjusts the engine thrust to maintain the desired speed set by the pilots. The Autothrust System continuously receives inputs from the aircraft’s sensors and flight management system to ensure the aircraft remains within the defined speed limits.

In addition to the Autothrust System, pilots also rely on the Flight Management and Guidance Computer (FMGC) to maintain speed limits. The FMGC processes various flight parameters, including altitude, temperature, and weight, to provide accurate speed guidance and enforce the specified limits. The FMGC is an integral part of the aircraft’s fly-by-wire system, which enhances flight control and automation.

Furthermore, Airbus A320 pilots receive comprehensive training on managing speed limits as part of their type rating and recurrent training programs. They are educated on the applicable speed limits, how to interpret and react to speed warnings, and the necessary procedures to ensure safe and efficient flight operations. Regular simulator sessions also allow pilots to practice speed management during various flight scenarios, helping them to develop their skills and decision-making abilities.


The speed limit, or SPD LIM, on the Airbus A320 is a critical aspect of operating the aircraft safely and efficiently. By adhering to the Maximum Operating Mach Number (Mmo) and the Maximum Operating Speed (Vmo), pilots can ensure the structural integrity of the aircraft and mitigate the potential risks associated with exceeding these limits. Through advanced systems such as the Autothrust System and the Flight Management and Guidance Computer, pilots are equipped with the necessary tools to manage speed limits effectively. With comprehensive training, pilots can confidently navigate and control the Airbus A320 within its designated speed parameters.

For More: What is LGPIU on Airbus A320? (Landing Gear Position Indicator Unit)