Direct Law — Stick to Surface, Manual Trim, No Protections

Direct law is the lowest computer level of fly-by-wire: the sidestick moves the surfaces almost directly, there is no auto trim (the pilot must trim manually), and all protections are gone — only the overspeed and stall warnings remain. The defining cue is the amber USE MAN PITCH TRIM on the PFD, and the defining technique change is that conventional manual trimming returns.

Pitch direct law is a direct stick to elevator relationship (elevator deflection is proportional to stick deflection)... As there is no automatic trim, the pilot has to use manual trim. The "USE MAN PITCH TRIM" amber message is displayed on the PFD. All protections are inoperative. The α floor function is inoperative. — FCOM DSC-27-20-20-30

1. Pitch direct

Per FCOM DSC-27-20-20-30, pitch direct law is a direct stick-to-elevator relationship (elevator deflection ∝ stick deflection). The maximum elevator deflection varies with CG — a compromise between adequate controllability at forward CG and not-too-sensitive controllability at aft CG. There is no automatic trim, so the pilot trims manually, and the PFD shows amber USE MAN PITCH TRIM. All protections are inoperative, including alpha floor; only the overspeed and stall warnings remain (as in alternate law).

[!warning]- The big change is manual trim — conventional trimming returns The single most important handling difference: there is no auto trim in direct law (FCOM DSC-27-20-20-30). Per FCTM AS-CG, in normal/alternate law the pitch-trim (THS) automatically adjusts to maintain the flight path with no elevator deflection — that is the auto-trim that makes the neutral-stick-holds-path characteristic. In direct law that automation is gone: with every speed or configuration change the aircraft is out of trim until the pilot trims it with the manual pitch-trim wheel — the conventional-aircraft technique of anticipating and trimming returns. The amber USE MAN PITCH TRIM is the reminder, and pitch sensitivity also varies with CG, so the feel changes with loading.

2. Roll direct and yaw alternate

Per FCOM DSC-27-20-20-30, roll direct law is a direct stick-to-surface position relationship, gains auto-set by slats/flaps configuration, with a maximum roll rate of ~20–25°/s (depending on speed/config) and spoilers 2, 3 and 6 inhibited (except with additional lateral-control failures). Yaw stays in yaw alternate law: Dutch-roll damping is available with authority ±4° rudder (CONF 0) / ±15° (other configs), and turn coordination is provided except in CONF 0.

[!warning]- Roll is faster than normal law — 20–25°/s vs 15°/s Direct-law roll rate (20–25°/s) is higher than the 15°/s of Normal law (FCOM DSC-27-20-20-30) — the aircraft feels noticeably more responsive in roll, so make smaller lateral inputs. With spoilers 2/3/6 inhibited the roll comes mostly from ailerons + the remaining spoilers. Yaw is still computed (yaw alternate law, Dutch-roll damping) — the rudder is fly-by-wire, so the BCM only takes over on a total electrical/computer loss, not in direct law.

3. The PFD in direct law

Per FCOM DSC-27-20-20-30, the PFD changes:

• bank and pitch limitation symbols → amber X;
• the overspeed protection symbol (=) disappears;
• VαPROT / VαMAX → VSW;
• USE MAN PITCH TRIM (amber) in direct law (or in flare law without RA);
• MAN PITCH TRIM ONLY (red) if a left + right elevator fault is detected.

[!warning]- MAN PITCH TRIM ONLY (red) means the elevators are gone — THS only Distinguish the two messages: amber USE MAN PITCH TRIM means no auto trim, trim manually (elevators still work); red MAN PITCH TRIM ONLY means both elevators have failed and pitch is now only the mechanical THS trim wheel (FCOM DSC-27-20-20-30 / -10). Red is the deeper failure — the bridge to mechanical backup.

4. How you get there, and how it behaves at the edges

Direct law is reached by accumulating failures below alternate, by the alternate low-speed-stability boundary reverting to direct, or by the electrical emergency configuration on gear extension (LAND RECOVERY ON). At the high-speed edge, recall (12) that a severe overspeed gives an automatic protective pitch-up in alternate but not in direct law — so in direct law the overspeed recovery is entirely manual (AP not available, speedbrakes, idle thrust, manual pitch).

[!note]- Direct law removes the automatic helpers, not just the protections (integrative synthesis) The pattern across the degradation ladder: alternate keeps auto-trim and some automatic recoveries (the high-speed pitch-up); direct law removes auto-trim and the automatic pitch-up (12). So in direct law the crew is doing the trimming and the overspeed/stall recovery by hand — the warnings remain, but the automation that would have helped is gone. This is why the conventional manual-trimming technique is the key skill for direct law.

5. Counterintuitive points

[!warning]- No auto trim and no protections — only warnings Direct law removes auto trim and every protection including alpha floor; the overspeed and stall warnings (aural) are all that remain (FCOM DSC-27-20-20-30).

[!warning]- Roll is more sensitive, pitch feel depends on CG ~20–25°/s roll rate, and max elevator deflection set by CG (FCOM DSC-27-20-20-30) — make small inputs and anticipate trim.

[!warning]- The automatic overspeed pitch-up is gone in direct law Severe-overspeed auto pitch-up acts in alternate but not direct (FCTM/12) — recovery is manual.

6. Self-test

[!note]- Q1. What is pitch direct law, and what must the pilot do? Direct stick-to-elevator (∝), max deflection varying with CG; no auto trim → trim manually (USE MAN PITCH TRIM) with conventional anticipation.

[!note]- Q2. What protections remain in direct law? None — all inoperative including alpha floor; only overspeed and stall warnings remain (and no automatic overspeed pitch-up).

[!note]- Q3. Roll rate and inhibited spoilers in direct law? ~20–25°/s (vs 15°/s normal); spoilers 2, 3, 6 inhibited; yaw alternate law (Dutch-roll damping, turn coordination except CONF 0).

[!note]- Q4. Amber USE MAN PITCH TRIM vs red MAN PITCH TRIM ONLY? Amber = no auto trim (elevators OK, trim manually); red = both elevators failed, pitch via THS trim wheel only.

7. Key takeaways

References

• FCOM DSC-27-20-20-30 (Reconfiguration Control Laws — Direct Law) — pitch direct stick-to-elevator (∝ deflection), max elevator deflection varies with CG (forward-CG controllability vs aft-CG sensitivity compromise), no auto trim (manual trim, USE MAN PITCH TRIM amber on PFD), all protections inoperative, alpha floor inoperative, overspeed and stall warnings available; roll direct stick-to-surface, gains by slats/flaps config, max roll rate ~20–25°/s, spoilers 2/3/6 inhibited; yaw alternate law (Dutch-roll damping ±4° CONF 0 / ±15° other, turn coordination except CONF 0); PFD bank/pitch limitation → amber X, overspeed symbol disappears, VαPROT/VαMAX → VSW, USE MAN PITCH TRIM amber, MAN PITCH TRIM ONLY red on L+R elevator fault.
• FCTM AS-CG (Center of Gravity) — in flight the pitch-trim surface automatically adjusts to maintain the flight path with no elevator deflection (normal/alternate); position depends on CG, altitude, speed, weight, configuration; pre-takeoff trim set per CG for consistent rotation and trimmed at V2+10.
• FCOM DSC-27-20-20-10 / FCTM PR-AEP-MISC — degradation entry (low-speed-stability boundary to direct, ELEC EMER on gear down); severe-overspeed automatic pitch-up acts in alternate but not direct law.

Independent study material, not an Airbus publication and not endorsed by the manufacturer. Always defer to the current operator FCOM, FCTM, and QRH for operational use.