What is S/D on Airbus A320? (Step Descent)

Step Descent, abbreviated as S/D, is an aviation term used to describe a specific technique employed by pilots during the descent phase of a flight. It involves a series of planned altitude reductions made in a stepped manner, rather than a continuous descent from cruise altitude to the final approach altitude. This technique is commonly used by pilots of the Airbus A320 aircraft to ensure a safe and efficient descent profile.

Step Descent is typically initiated when the aircraft reaches its top of descent (TOD) point, which is calculated based on factors such as the distance to the destination, aircraft weight, and prevailing weather conditions. At this point, the flight management system (FMS) onboard the Airbus A320 provides the pilots with vertical navigation guidance to facilitate a step-by-step reduction in altitude.

The Benefits of Step Descent

Step Descent offers several advantages over a continuous descent approach, which is used when allowed by air traffic control. The key benefits of Step Descent on the Airbus A320 include:

The Reduction of Noise and Fuel Consumption

By descending in a series of steps, the aircraft is able to minimize its engine power, resulting in reduced noise levels and lower fuel consumption. This is especially important during the approach to airports near densely populated areas, where noise abatement procedures may be in place. Additionally, the reduced fuel consumption translates to cost savings for airlines and a smaller carbon footprint for the aviation industry.

Improved Air Traffic Management Efficiency

Step Descent allows air traffic controllers to better manage the sequencing of arriving aircraft. By implementing a series of altitude steps, pilots can be assigned different speeds and spacing, enabling controllers to achieve a more efficient flow of traffic. This helps to reduce congestion and delays, particularly during peak travel periods or at airports with high traffic volume.

Optimized Flight Profile

Step Descent enables pilots to maintain a stable and controlled descent profile, ensuring a smooth transition from cruising altitude to the final approach. This allows for better planning and coordination of the crew’s tasks, including the configuration of the aircraft for landing and the execution of necessary checklists. By following the step-wise descent path provided by the FMS, pilots can ensure a consistent and predictable approach, enhancing flight safety.

Step Descent Procedure on the Airbus A320

The Airbus A320 is equipped with advanced avionics systems that automate and aid the step descent procedure. To begin the descent, the pilots initiate the managed descent mode on the flight control panel, allowing the aircraft’s autopilot system to control the descent rate and vertical navigation. The Flight Management and Guidance System (FMGS) computes the optimal descent path based on various inputs, including the aircraft’s weight and the desired crossing altitude at each step of the descent.

Once the managed descent mode is engaged, the pilots monitor the descent profile and make any necessary adjustments or interventions as required. They can override the automation at any time by selecting the open descent mode, which allows for manual control of the descent rate.

During the step descent, the pilots follow the vertical navigation guidance provided by the FMGS, which includes specific altitudes at each step. These altitudes are typically determined by air traffic control or published approach procedures, taking into account factors such as terrain clearance, airspace restrictions, and noise abatement procedures.


Step Descent is a valuable technique employed by pilots operating the Airbus A320 aircraft to facilitate safe and efficient descents. By descending in a series of steps, pilots can achieve a controlled and predictable approach, reducing noise levels, fuel consumption, and overall flight costs. Additionally, Step Descent improves air traffic management efficiency and helps streamline the flow of arriving aircraft. With the advanced automation and guidance systems onboard the Airbus A320, pilots can effectively execute the step descent procedure and ensure a smooth transition from cruising altitude to the final approach.

If you want to learn more about the Airbus A320’s Step Descent procedure, you can refer to the official Airbus A320 Flight Crew Operating Manual. This comprehensive guide provides detailed information on aircraft operations and procedures, ensuring the safe and proficient handling of the aircraft.


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