In the digital heart of the Airbus A320 lies a system that quietly runs the show from takeoff to touchdown: the Flight Management and Guidance Computer, or FMGC. For pilots, this isn’t just another black box — it’s the brain behind every managed descent, every lateral navigation leg, and every precision approach. The FMGC doesn’t just assist pilots — it thinks ahead, guiding the aircraft with remarkable precision and reliability.
Table of Contents
Let’s break down what the FMGC does, how it works, and why it’s considered one of the most vital components of modern airliner automation.
What Is the FMGC?
The FMGC is the central computer system that powers the Airbus A320’s Flight Management and Guidance System (FMGS). Its main function? To automate the flight by:
- Predicting and optimizing speed, altitude, time, and fuel
- Managing flight paths and navigation profiles
- Reducing crew workload through intelligent automation
Paired with the MCDU and FCU, the FMGC provides both fully automated and pilot-selected modes of control.
How the FMGC Works Within the FMGS
The FMGS is an umbrella system that manages flight trajectories. The FMGC is the core processor inside that umbrella. Once the pilot loads a route into the MCDU — including SIDs, STARs, waypoints, and approaches — the FMGC:
- Builds lateral, vertical, and speed profiles
- Calculates aircraft performance in real-time
- Continuously monitors position via GPS, DME/DME, or IRS inputs
If one FMGC fails, the other takes over — ensuring redundancy and safety at all times.
Managed vs. Selected Guidance
The A320’s FMGC supports two distinct guidance modes:
- Managed Guidance: The FMGC flies the aircraft based on the entered flight plan. It controls lateral and vertical navigation (NAV and CLB/DES modes) and optimizes fuel and performance.
- Selected Guidance: Pilots override the automation by selecting headings, speeds, or vertical speeds using the FCU knobs. This gives the crew full control — and always takes priority over managed inputs.
This dual-mode flexibility allows pilots to adapt instantly to ATC instructions or tactical changes.
Core Components of the FMGC
Each Airbus A320 is equipped with two FMGCs, operating in sync or as backups. The FMGC consists of two functional halves:
Flight Management (FM)
- Flight planning
- Navigation radio tuning
- Performance predictions
- Display control (ND, MCDU)
Flight Guidance (FG)
- Autopilot (AP) commands
- Flight Director (FD) logic
- Autothrust (A/THR) management
FMGC Databases and Customization
The FMGC operates based on five key databases:
| Database | Function | Airline Editable? |
|---|---|---|
| Navigation DB | Waypoints, airways, airports, runways, SIDs/STARs | ✅ Yes |
| Airline Modifiable Info (AMI) | Thrust reduction altitudes, fuel policy, AOC customization | ✅ Yes |
| Performance DB | Engine and aerodynamic models | ❌ No |
| Magnetic Variation | Geographic magnetic deviation | ✅ Yes |
| Pilot-Defined Data | 20 waypoints, 5 routes, 10 user-defined runways/navaids | ✅ Yes (via MCDU) |
The navigation database is updated every 28 days, either manually (~20 min) or by cross-loading (~5 min).
Why the FMGC Is Central to Modern Flight
Without the FMGC, modern jet operations would be slower, riskier, and more demanding on pilots. This system allows for:
- Precise lateral/vertical navigation
- Reduced pilot fatigue
- Seamless integration with ATC requirements
- Increased safety through prediction and automation
In short: the FMGC is what turns the Airbus A320 into a high-performance, automated flying machine — with pilots remaining in full control when needed.
✅ Final Thoughts
Whether you’re programming the route into the MCDU or taking manual control via the FCU, the FMGC is your constant partner. It’s no exaggeration to say the Airbus A320 couldn’t fly the way it does without it.
If you’re a student pilot or aviation enthusiast, understanding the FMGC is a major step toward mastering modern aircraft operations.
People Also Ask
How does the FMGC integrate with other avionics systems in the A320?
What are the key features and capabilities of the A320 FMGC?
The A320’s FMGC is a multi-role powerhouse. Its main features include:
-
Automated Flight Planning from departure to arrival, including SIDs, STARs, approaches, and alternates.
-
Lateral and Vertical Navigation Management using computed profiles.
-
Performance Prediction (fuel, time, speed, altitude) in real-time.
-
Guidance Control via both managed and selected modes.
-
Navigation Radio Tuning (ILS, VOR, DME) automatically or manually.
-
Database Access including navigation data, performance models, and airline policies.
-
Redundancy — dual FMGCs that back each other up in case of failure.
These capabilities work together to reduce pilot workload and enhance flight precision.
How does the FMGC handle navigation and flight planning for the aircraft?
What are the common issues or failures associated with the FMGC in the A320?
The FMGC is robust, but like any avionics system, it's not immune to issues. Some common problems include:
-
Dual FMGC failure (rare): Reverts aircraft to backup raw-data flying using HDG/V/S and manually tuned radios.
-
MCDU freezing or blanking: May require a reset of the unit or switching to the other FMGC.
-
Route discontinuities: Occur when transitions between waypoints or procedures are incomplete or misconnected.
-
Incorrect performance entries: Can lead to erroneous predictions (e.g. wrong fuel burn or climb profile).
-
Database loading errors: Navigation DB updates can sometimes fail or produce "invalid" data if not correctly managed.
Most issues are either handled automatically via system reversion or easily resolved by trained crew through standard procedures.
How do pilots interact with the FMGC during flight operation?
Pilots use two primary interfaces: the MCDU and the FCU.
-
On the MCDU, pilots enter or modify the flight plan, performance data (weight, cost index, cruise altitude), and review predictions.
-
On the FCU, they engage or override the system using managed (automatic) or selected (manual) guidance — adjusting heading, altitude, speed, and vertical speed.
-
During the flight, pilots monitor FMGC behavior through the PFD and ND displays, and make inputs if ATC changes routing or if conditions require tactical decisions (e.g. avoiding weather).
The FMGC is designed to be intuitive, but its full power is unlocked when pilots understand both its automation and its limitations.
How does the FMGC contribute to flight safety and efficiency?
In short: it helps the aircraft fly smarter, not harder.
-
Safety: The FMGC reduces pilot workload, enhances situational awareness, and minimizes the chance of human error. Its prediction features help anticipate fuel needs, altitude changes, and missed approaches long before they become time-critical.
-
Efficiency: It optimizes flight paths for time, fuel, and cost, adjusting in real-time for winds, weight, and airspace constraints. It also automates tedious tasks like radio tuning and profile management, freeing up cognitive space for monitoring and decision-making.
The FMGC is one of the main reasons a two-pilot crew can safely and efficiently fly 180+ passengers across continents.