What does the Airbus A320 FCU do, and how do you use it?
In Airbus A320 flight simulation, the FCU is the glareshield panel you use to command the aircraft's guidance system. It lets you set speed, heading, altitude and vertical modes, then either fly those values directly in selected mode or let the FMS fly them in managed mode.
FCU means Flight Control Unit. It sits above the main panel and works with the flight directors, autopilot and autothrust. If you want the wider cockpit context first, our guide to the main A320 cockpit controls and displays shows where the FCU fits.
What does the Airbus A320 FCU control?
The FCU is the A320's immediate flight-guidance control panel. It does not replace the MCDU or flight plan; it tells the aircraft how to follow that plan, or how to override it for a while.
- Speed or Mach targets
- Heading or track targets, or a return to managed lateral navigation
- Target altitude and the choice between managed climb/descent and open climb/descent
- Vertical speed or flight path angle when you want a specific vertical path
- Automation controls such as flight director, autopilot, autothrust, localiser and approach arming
Even when you are hand-flying, the FCU still matters because the flight director bars follow the modes and targets set there. A simple way to think about it is this: the MCDU plans the flight, the FCU tells the aircraft what to do right now.
How do selected and managed modes work?
This is the part that catches most sim pilots. On the A320 FCU, pull usually means 'fly the value I have just chosen', while push usually means 'hand control back to the managed flight plan'.
| FCU control | Selected action | Managed or alternate action |
|---|---|---|
| Speed | Pull to fly the chosen speed or Mach | Push to return to managed speed from the FMS |
| Heading/Track | Pull to fly the chosen heading or track | Push to return to managed lateral navigation |
| Altitude | Pull to use open climb or open descent to the selected altitude | Push to use managed climb or descent if the flight plan supports it |
| V/S-FPA | Select a vertical speed or flight path angle and engage it deliberately | Mode behaviour varies by aircraft state and sim model, so confirm on the FMA |
The key instrument is not the FCU window. It is the FMA at the top of the primary flight display, because that tells you what mode the aircraft has actually accepted. A mistake we see constantly is pilots rotating a knob, seeing the number change, and assuming the aircraft will obey without checking the FMA.
How do you use the A320 FCU in a flight simulator?
Use the FCU whenever you need to change the aircraft's immediate behaviour without rewriting the whole route. A normal sim workflow looks like this.
- Set the altitude window. Rotate the FCU altitude to the cleared altitude. In Airbus logic, that number is more like an authorised limit than a promise to climb or descend by itself.
- Choose the lateral mode. If you want to stay on the programmed route, use managed lateral navigation. If ATC gives you vectors, weather avoidance, or pattern work, choose a heading and use selected lateral mode.
- Choose the speed mode. Managed speed is best for a normal departure, climb, cruise and approach profile. Selected speed is better when spacing, restrictions or training needs matter more than the computed profile.
- Command the vertical mode. This is where many descents go wrong. Simply winding the altitude down does nothing unless you also select a descent mode such as managed descent, open descent, or a chosen vertical speed or flight path angle.
- Engage the automation you want. Use the flight directors, AP1 or AP2, and A/THR as needed. In most A320 simulations, the FCU can still provide guidance with the autopilot off as long as the flight director is on.
- Confirm every change on the FMA. If the top of the PFD does not show the mode you expected, fix that first before making the next input.
If you want to see how those FCU inputs fit into a full departure, cruise and arrival, we also show how the FCU is used through a complete A320 flight in Microsoft Flight Simulator.
When should you use selected mode instead of managed mode?
Use selected mode when you need direct control now: ATC vectors, speed control for spacing, weather avoidance, visual pattern work, or recovery from a bad flight plan. Use managed mode when the route and performance setup are correct and you want Airbus automation to follow them efficiently.
Do you need the MCDU as well?
Yes, for proper managed guidance you usually do. The FCU can command selected modes on its own, but managed lateral and vertical modes depend on a sensible route, correct performance setup and a valid approach in the FMS. If that part is incomplete, the FCU can appear to ignore you when it is really dropping into a different mode. Our guide to programming the A320 MCDU and managed flight plan correctly covers the setup that makes the FCU behave properly.
Why is the FCU not doing what I selected?
Most A320 FCU problems in a simulator come from mode logic, not from a broken aircraft. Check these first.
- You changed the number but not the mode. Rotating a value is only half the job. In many cases you must then push or pull the selector to tell the aircraft how to use that value.
- You did not check the FMA. The aircraft may still be in NAV, CLB, DES, ALT or APPR even though the FCU window shows a new target.
- The flight plan is weak or incomplete. Managed heading, managed descent and approach capture can behave oddly if the route has gaps, bad constraints or no valid arrival setup.
- You used too much vertical speed. Aggressive V/S commands can bleed speed quickly. If the aircraft starts chasing altitude while the speed decays, reduce the rate or return to a managed or open mode.
- You expected the FCU to fix a poor intercept. LOC and APPR are not magic capture buttons. The aircraft still needs a sensible intercept angle, correct frequency or approach data, and stable geometry.
- Your aircraft model simplifies Airbus behaviour. Some lighter or default A320s do not model every push-pull nuance. When that happens, trust the PFD mode annunciations and the aircraft's own documented behaviour rather than assuming study-level Airbus logic.
Once you understand three habits - set the target, choose selected or managed, then verify the FMA - the Airbus A320 FCU stops feeling mysterious and becomes one of the most logical panels in the cockpit.