What is FGC on Airbus A320? (Flight Guidance Computer)

The Flight Guidance Computer (FGC) is a critical component of the Airbus A320 aircraft. It is an advanced computer system that plays a crucial role in providing flight guidance and control to the aircraft. The FGC works in conjunction with other systems, such as the Flight Management System (FMS) and autopilot, to ensure safe and efficient flight operations.

The FGC is responsible for calculating and displaying essential flight-related information to the pilots, including routes, speeds, altitudes, and vertical and lateral navigation. It also controls the autopilot and autothrust systems, helping to maintain the aircraft’s stability and performance during various phases of flight.

Flight Guidance Computer

The Flight Guidance Computer on the Airbus A320 is a highly advanced and sophisticated computer system. It is designed to perform complex calculations and execute precise flight control commands. The FGC is composed of various components, including processors, memory units, and input-output interfaces.

The FGC uses redundant architecture to ensure reliable and fault-tolerant operation. It typically consists of two identical computers known as FGC1 and FGC2. These computers are constantly cross-checking and comparing their outputs to enhance system integrity and safety. If a discrepancy is detected between the two computers, the system automatically isolates the faulty unit and transfers control to the remaining operational unit.

The FGC operates using multiple software modules that are responsible for different functions. These modules include the Flight Management System, Autopilot, Flight Director, and Autothrust. Each module has specific roles and interacts with the other systems to ensure accurate and precise flight guidance.

Functions of the Flight Guidance Computer

The Flight Guidance Computer performs several vital functions on the Airbus A320. Let’s take a closer look at some of its key functions:

Flight Management System (FMS)

The Flight Management System (FMS) is an integral part of the Flight Guidance Computer. It is responsible for flight planning, performance calculations, and navigation. The FMS receives inputs from various sources, such as the Inertial Reference System (IRS), Global Navigation Satellite System (GNSS), and Air Data Inertial Reference System (ADIRS), to determine the aircraft’s position, speed, and heading.

The FMS uses this information to compute the most efficient route, taking into account factors such as wind, altitude restrictions, and airspace limitations. It also helps manage fuel consumption by optimizing the flight profile. Pilots can input the desired parameters, such as the destination airport and cruising altitude, into the FMS, which then generates a flight plan accordingly. The FMS communicates with the Flight Guidance Computer to provide the necessary guidance and control commands during the flight.

Autopilot and Flight Director

The Flight Guidance Computer also controls the autopilot and flight director systems on the Airbus A320. The autopilot is a sophisticated system that can automatically control the aircraft’s attitude, altitude, and heading based on the commands received from the FGC. It provides a hands-off flying experience for the pilots, allowing them to focus on other essential tasks.

The flight director, on the other hand, provides guidance to the pilots by displaying cues on the Primary Flight Display (PFD). It shows the desired flight path, including the correct attitude, altitude, and heading, based on inputs from the FGC. Pilots can follow the flight director cues to manually control the aircraft or engage the autopilot to fly the selected flight path automatically.


The Flight Guidance Computer also interfaces with the autothrust system, which automatically controls the aircraft’s thrust to maintain the desired speeds during different phases of flight. The autothrust system uses inputs from the FGC, including the selected flight mode and target speed, to determine the appropriate thrust setting for the engines.

For example, during takeoff, the autothrust system will adjust the engine thrust to achieve the desired takeoff speed. Similarly, during descent and landing, it will control the engines to maintain the selected approach speed. The autothrust system works in conjunction with other systems, such as the Flight Management System and autopilot, to ensure smooth and precise speed control.

Overall, the Flight Guidance Computer plays a crucial role in providing accurate flight guidance and control on the Airbus A320. It incorporates advanced technology and redundancy measures to ensure the highest levels of safety and reliability. Pilots rely on the FGC to navigate through various flight phases while maintaining optimal performance and efficiency.

For More: What is FPD on Airbus A320? (Flight Path Director)