A320 Autopilot and Flight Director Behavior: When the AP Steps Aside

What are the preconditions for engaging the A320 autopilot?

The AP can be engaged within the normal flight envelope, 5 seconds after liftoff and at least 100 ft. Before engaging it, fly the aircraft on the intended path, confirm the appropriate FD modes, and center the FD bars. The architecture works in the order the FCTM puts it in: pilot first, FD second, AP third. Engaging the autopilot before the airplane is already stable on the intended path is asking the AP to chase the airplane to a place the pilot has not yet decided on.

Reference: FCOM DSC-22_30-30; FCTM OP-030.

When can both A320 autopilots be engaged at the same time?

Two APs may be engaged at a time when LOC/G/S, rollout, or go-around mode is armed or engaged. In that configuration, AP1 is active and AP2 is in standby. The candidate-intuitive picture of "both APs flying together simultaneously" is not what the FCOM describes — one AP does the active guidance work, the other parallel-tracks and is ready to step in if the active AP fails. This active/standby architecture is what enables fail-operational autoland and produces the CAT 3 DUAL availability indication.

Reference: FCOM DSC-22_30-30, DSC-22_30-80-30-10.

What is the difference between CAT 3 SINGLE and CAT 3 DUAL on the A320?

The cascade matters operationally — pilots who notice the indication drop from DUAL to SINGLE need to know whether their planned minima are still flyable on the degraded capability.

Reference: FCOM DSC-22_30-30.

How does the A320 autopilot disconnect when the pilot uses the sidestick takeover pushbutton?

Pressing the sidestick takeover pushbutton disconnects the AP. When disconnected that way, the cavalry charge audio warning is temporary; a second press is only needed if the crew wants to cancel the warning early. Candidates who describe this as a required two-press sequence ("press to disconnect, press to silence") have memorized a rhythm that is not in the FCOM. The pushbutton disconnect is one press; the second press is optional housekeeping.

Reference: FCOM DSC-22_30-30.

What happens when the A320 pilot disconnects the autopilot by sidestick force?

Sidestick override above the disconnect threshold — heavy force on the sidestick rather than the pushbutton — produces a non-standard automation override, and the cavalry charge does not silence on its own. The pilot must intentionally press the instinctive disconnect pushbutton to clear the warning. The cockpit treats force-based disconnect as a different kind of event than pushbutton disconnect — the system wants to know the pilot made an intentional decision to take the airplane back, not that the sidestick got bumped by a knee in turbulence.

Reference: FCOM DSC-22_30-30.

What automatic conditions disengage the A320 autopilot?

AP1 or AP2 disengages on a defined set of pilot actions and limit conditions. In normal law with all protections available, additional protection-related triggers apply.

The architecture is honest about its own limits: the moment any boundary is crossed, the AP steps aside.

Reference: FCOM DSC-22_30-30.

Is the A320 autopilot available in alternate law?

Alternate law is usually triggered by dual failures. AP availability in alternate law is failure-dependent and cannot be presented as guaranteed — some alternate-law cases leave AP 1+2 inoperative as part of the consequence cascade. The candidate who says "AP is available in alternate law" without naming the cascade is making a statement that is sometimes true and sometimes flatly wrong, depending on what produced the alternate law in the first place. The right candidate posture is to name the cascade first, then name what is available given that cascade.

Reference: FCTM OP-020; FCOM PRO-ABN-AUTO_FLT and PRO-ABN-ELEC.

What is lost in alternate law on the A320 in cases where the autopilot remains available?

Alpha-floor protection is lost in alternate law. The low-energy aural alert is inhibited. Both functions are tied to the protection logic that alternate law steps away from. The crew must now monitor energy state manually — the FAC will no longer command TOGA when AoA crosses the threshold because the threshold-based command is part of normal-law protection. Reactive windshear detection follows its own failure logic and is not automatically lost simply due to law degradation; it depends on the specific failure that caused the alternate law. Lateral control reverts to roll direct law in alternate law, so the airplane responds more directly to sidestick deflections.

Reference: FCOM DSC-22_40-30; FCTM OP-020.

Is the A320 autopilot available in direct law?

No. Autopilot engagement is blocked in direct law because the automated stabilization software loops have been bypassed. The relationship between sidestick input and control surface deflection is direct: deflect the stick, the surfaces move proportionally. There is no inner loop adding stability augmentation and no protection logic preventing the airplane from being commanded outside its envelope. If the autopilot was engaged at the moment the law degraded into direct law, the AP disconnected automatically during the transition. For the related flight control law cascade across ELAC, SEC, and FAC, see the ELAC/SEC/FAC hub.

Reference: FCOM DSC-27-20-20; FCTM AO-027.

Is direct law on the A320 a one-way trip?

Not always. While direct law is active, there is no autotrim and no protections, and manual pitch trim is required. However, abnormal-attitude law can revert to alternate law once the aircraft returns within the normal flight envelope, with alternate law then remaining for the rest of the flight. The pure-direct-law cascades (gear extension cases, dual ELAC cases) do stay until landing. The blanket answer "direct law stays until landing" overstates the architecture — the abnormal-attitude cascade has a recovery path back into alternate law. Knowing the difference is the candidate's signal of having read the law-transition diagrams, not just the headline.

Reference: FCOM DSC-27-20-20.

What is the engagement trigger for A320 GO-AROUND mode?

Setting at least one thrust lever to the TOGA detent engages go-around modes if the flaps lever is at least position 1 and the aircraft is in flight, or has been on ground for less than 30 seconds. Candidates who shorten the trigger to "slats extended" or to "thrust levers forward" are not naming the FCOM-precise conditions. The flaps lever position is what the FMGS checks — the slats extending is a consequence of the flaps lever moving, not the trigger itself. Use the lever wording on orals; examiners are listening for it.

Reference: FCOM DSC-22_30-80-40; FCTM NO-180.

What does the A320 FMA show after a successful go-around engagement?

For most A320/A321 aircraft, the FMA shows SRS/NAV after the go-around trigger is met; GA TRK applies when HDG or TRK is preset or applicable. SRS handles the vertical guidance toward the target speed; NAV continues lateral guidance along the F-PLN where the missed approach routing now sits. The candidate-intuitive assumption that the FMA always shows GA TRK on go-around is incorrect for this fleet — the published FMA for most A320/A321 aircraft is SRS/NAV, with GA TRK appearing only when HDG or TRK was preset for the missed approach.

Reference: FCOM DSC-22_30-80-40; FCTM NO-180.

What happens on the A320 if TOGA is not selected during a go-around?

If TOGA is not selected, the FMS remains in APPR phase and the AP/FD remain engaged in approach or landing mode; the primary F-PLN becomes PPOS-DISCONT. The retained mode could be G/S, LOC, LAND, or FLARE depending on where the airplane was in the approach sequence at the moment the pilot tried to go around without the TOGA detent. The FMA is still showing engaged approach guidance because the FMS still thinks the approach is happening. This is the classic examiner oral trap because it happens precisely at the moment of highest workload.

Reference: FCTM NO-180, PIR-010.

What do the A320 flight director bars show?

The pitch bar gives pitch orders for vertical guidance. The roll bar gives roll orders for lateral guidance. Each bar tells the pilot what the active mode is pointing toward, not what the airplane is currently doing. The bars are command targets, not state indicators. The FD bars are present whenever an FD is selected on, regardless of whether the autopilot itself is engaged — this matters operationally because the FD continues to show command guidance to a hand-flying pilot after the AP disconnects.

Reference: FCOM DSC-22_30-20.

Why do the A320 FD bars sometimes disappear from the PFD?

FD bars disappear from the PFD when the aircraft attitude exceeds specific thresholds — severe bank, severe pitch, or unusual attitude regimes. The disappearance is itself a visual prompt: the system has decided the airplane is no longer in a regime where command guidance is meaningful, and raw data manual recovery becomes the priority. Candidates who notice the FD bars vanishing are getting a signal that the airplane needs hands-on attention, not automation troubleshooting.

Reference: FCOM DSC-22_30-20.

Why is following the A320 FD bars blindly a candidate trap?

The FD bars are command targets, not state indicators. The FD pitch bar can freeze on an old mode target if a mode change has not happened cleanly, and following the frozen bar can produce an energy depletion event if speed is decaying. The discipline is to cross-check with the airspeed tape and the vertical speed indicator. The FD is a tool, not a flight plan. Trust the bars. Verify the energy. Both.

Reference: FCOM DSC-22_30-20; FCTM OP-030.