In the dimly lit cockpits of 1970s airliners, pilots faced a wall of analog gauges, each demanding constant attention. The transition to glass cockpits didn’t just change displays, it revolutionized control. At the heart of this transformation sits the Flight Control Unit (FCU), Airbus’s masterstroke in human-machine interface design.

the FCU serves as the tactical command center where human intuition meets digital precision.

What is the Flight Control Unit (FCU)

The Flight Control Unit (FCU) is the primary interface between pilots and the automatic flight systems in Airbus aircraft. Located centrally on the glareshield for easy access, it allows pilots to control autopilot functions, autothrust, and navigation modes without looking away from their primary instruments. Unlike traditional control panels, the FCU integrates multiple functions into a single streamlined interface, replacing dozens of individual controls and displays.

Flight Control Unit Parts

The FCU’s layout follows a logical design philosophy, with dedicated controls for each flight parameter:

• SPD/MACH Knob and Button: Toggles between speed (knots) and Mach number, with a range of 100-399 knots or 0.1-0.99 Mach
• HDG/TRK Knob: Sets heading or track angle from 0° to 359°
• Altitude Selector: Dual knobs (inner/outer) for precision altitude selection from 100-49,000 feet
• V/S or FPA Knob: Controls vertical speed (±6,000 ft/min) or flight path angle (±9.9°)
• Mode Buttons: LOC (localizer), APPR (approach), EXPED (expedite), and A/THR (autothrust) engagement

---

you’ll need this book before you start your Airbus A320 Type Rating “click here“

FCU Managed vs. Selected Modes

Airbus’s automation philosophy centers on two distinct control modes:

Managed Mode
Flight parameters are controlled by the Flight Management Guidance Computer (FMGC). The FCU displays three dashes and a dot, indicating the system is managing the aircraft’s trajectory based on pre-programmed flight plans.

Selected Mode
Pilots directly input values using the FCU knobs. The display shows numerical values without dots, indicating human-selected parameters .

The push-pull logic is intuitive: pushing a knob engages managed mode, while pulling activates selected mode. This design allows pilots to pre-select values before engaging selected mode.

Evolution of Flight Control Unit

The FCU represents the culmination of decades of interface evolution:

Table: Evolution of Flight Control Interfaces

Era	Interface Type	Key Characteristics	Limitations
1960s-1970s	Individual Analog Controls	Dedicated knobs/switches for each function	High workload, panel clutter
1980s-1990s	Early Digital Interfaces	Basic automation integration	Limited mode flexibility
2000s-Present	Integrated FCU Design	Dual-mode operation, intuitive push-pull logic	Initial pilot training requirement

---

Real-World Operational Scenarios

Normal Cruise Operations
During cruise, pilots typically use managed mode for optimal efficiency. The FCU displays dashes indicating the FMGC is controlling speed, altitude, and heading according to the flight plan. If ATC requests an altitude change, the pilot turns the altitude knob to the new value and pulls it to engage selected mode.

Approach and Landing
When preparing for an ILS approach, pilots press the APPR button to arm localizer and glideslope capture. The FCU displays appropriate cues showing the armed state. During difficult weather conditions, pilots might use selected mode for more precise control.

Emergency Situations
In case of unexpected weather or system failures, pilots can quickly disengage automation by pressing the instinctive disconnect buttons or switching to selected mode for direct control.

Integration with Other Systems

The FCU doesn’t operate in isolation, it’s part of an integrated network:

• Flight Management Guidance Computer (FMGC): Provides computed parameters for managed mode
• Autopilot/Flight Director: Executes commands from the FCU
• Electronic Flight Instrument System (EFIS): Displays current parameters and mode status “read about it“
• Autothrottle System: Controls thrust based on FCU inputs

Pilot Experience and Training Considerations

Transitioning to Airbus’s FCU requires understanding its unique philosophy. Experienced pilots from other aircraft types often need specific training to adapt to the managed/selected concept. However, once mastered, the system significantly reduces workload, especially during high-stress phases like approach and departure.

The consistent design across Airbus fleets (A320 to A380) means pilots can transition between types with minimal additional training, a significant operational advantage for airlines.

The Future of Flight Control Unit

While the basic FCU design has remained consistent, future developments may include:

• Enhanced touchscreen interfaces with haptic feedback
• Voice command integration for key functions
• Predictive mode selection based on flight phase and conditions
• Improved cybersecurity measures for critical flight controls

Frequently Asked Questions

What’s the difference between the FCU and MCDU?
The FCU is for short-term, tactical control of flight parameters, while the Multifunction Control and Display Unit (MCDU) is for programming and managing the overall flight plan. The FCU handles immediate changes, while the MCDU manages strategic navigation.

Can the FCU control the aircraft if other systems fail?
The FCU has redundant systems and can often continue operating even if some components fail. However, complete failure of all automation would require pilots to revert to manual flying using backup instruments.

Why do Airbus aircraft have two FCU panels?
Some larger Airbus aircraft have dual FCU panels (captain and first officer) for redundancy and flexibility. Each can control all functions, and if one fails, the other takes over.

How do pilots know which mode is active?
The Flight Mode Annunciator (FMA) on the Primary Flight Display shows currently active and armed modes, providing clear visual indication of the automation state.

What happens if pilots disagree on FCU inputs?
Airbus control systems are designed to prioritize captain inputs in case of conflicting commands, though standard operating procedures emphasize crew coordination to prevent such situations.

Is the FCU design the same across all Airbus aircraft?
The basic design philosophy and operation remain consistent across Airbus types, though specific implementations may vary slightly between models.