Director versus autopilot
The difference between the two machines is who moves the controls: the flight director advises and the autopilot acts, on what are essentially the same computed commands. That overlap is useful in both directions. With the autopilot engaged, the flight director gives the crew a means of cross-checking the control and guidance commands sent to the autopilot: the bars show what is being asked of the servos, so a command that makes no sense is visible before the aircraft has finished obeying it.
Flying with it, and when not to
A shown flight director is a commitment: when the flight director is engaged and shown, it must be followed. Bars commanding one manoeuvre while the pilot flies another is the worst of both worlds, guidance distrusted but still hypnotically present in the middle of the scan, and every deviation between bar and symbol reads as an error asking to be corrected. The combinations are each legitimate:
flight director only — hand-flying the computed guidance.
autopilot only — the automatics flying with the bars removed.
flight director and autopilot together — the normal airline state, the bars now serving as the cross-check.
What is not legitimate is shown-but-ignored.
The crew shares the buttons by a standard division. With the autopilot engaged, the pilot flying (PF) makes the mode and target selections, commanding the automatics as the way of flying the aircraft. With the autopilot disengaged, the pilot flying's hands are on the controls, so the pilot monitoring (PM) makes the selections on the pilot flying's command. And the commitment to follow the bars has its stated limit: a flight director showing incorrect guidance, or guidance that no longer matches what the crew is actually flying, should not be followed but turned off, a visual circuit flown against approach-mode bars being the classic case.
Scenarios and indications
Reading the bars is a skill of translation, and the syllabus asks for examples:
A higher altitude is selected with a climb mode engaged: the pitch bar (or the V) rises above the symbol, commanding pitch up; as the aircraft rotates into the climb the displacement shrinks toward zero, the bars centring on the attitude that flies the climb.
LOC is armed and the localizer comes alive: at capture the roll bar (or the V's bank) commands the turn onto the beam, then centres as the aircraft rolls out on it, wind correction already inside the command.
The selected altitude approaches in a climb: the pitch command eases progressively toward level, the capture phase of the previous lesson drawn as a slowly sinking bar, and a pilot following it flies the level-off without overshoot.
Same modes, same panel
There is no separate mode set to learn: the modes available for the flight director are the same as those available for the autopilot, and the same FCU/MCP is normally used to select them. HDG, ALT, V/S, LNAV, APP and the rest of the previous lesson's families drive the bars exactly as they drive the servos; the only difference is who closes the loop, servo or hand.
That shared origin is why the syllabus insists on verification: when using the flight directors, check the flight management computer (FMC) data and the selected autopilot modes through the FMA. The bars are only as good as the plan and the modes behind them; bars fed by the wrong routing or an unintended mode will confidently command the wrong flight path. If the flight directors are showing incorrect guidance, they should not be followed and should be turned off. Which requires knowing where the truth is displayed, and that is the second half of this lesson.
The FMA: the only truth
The flight mode annunciator (FMA) exists to answer one question with authority: what is the automatic flight system actually doing? Its importance rests on a distinction this module has been circling since the mode control panel appeared: the FMA is the only indication of the state of the system, as opposed to a switch position. Pressing a button is a request; the panel shows what was asked. The FMA shows what was accepted, what is armed, what is engaged, and what quietly changed. A crew that reads switches instead of the FMA is flying on requests.
Where it is, and how it reads
The FMAs are normally shown at the top of the primary flight display (PFD), one of the screens of the EFIS module 4 met, sitting directly in the flying pilot's scan. The strip is divided into sections, as applicable to the aircraft's complexity: autothrust modes, lateral modes, vertical modes, autopilot and flight director annunciators, and landing capability. And within each mode column the state is typographically honest: engaged and armed modes differ in colour or font size, engaged annunciations commonly in one colour (green on most aircraft) with armed ones in another (blue or white) or in a smaller face, so a glance separates what is flying now from what is waiting to.