Thrust Levers & Thrust Setting

"The thrust levers can only be moved manually. The range of movement is divided into 3 operating segments. The sector has 4 positions defined by detents or stops. Thrust lever position is transmitted to the FADEC which computes and displays the thrust rating limit and the EPR TLA."

"Can only be moved manually" is this lever's defining temperament. When A/THR is working, the lever does not move — it stays where you put it and serves as the thrust ceiling, beneath which the FMGC commands the engine. From that single fact an entire mental model unfolds: lever position = the maximum thrust you have authorised; a detent = a standardised level of authorisation; and the blue circle on the E/WD (the lever-position symbol) normally follows the lever — except in exactly one scenario, where it walks away on its own (§6, automatic TOGA).

1. The quadrant — angles, arcs and one hidden switch

                      TOGA (= GA) ── 55° TLA (MAX TO stop)
                     ╱   ▲
            GA SOFT ╱    │  manual-only territory (44.2° – 55°)
              FLX/MCT ── 42° TLA (MAX CONT / FLEX TO / DERATED TO detent)
                   ╱   ◄─┼── A/THR electrical activation ceiling: 44.2° TLA
                  ╱      │
              CL ─── 30° TLA (MAX CLIMB detent)
                ╱        │
               ╱   ① two engines: A/THR active range = idle → CL
          IDLE ── 0°
              ╲    ② one engine out: A/THR active range = idle → FLX/MCT
               ╲
                ╲  reverse sector (lift reverse levers past idle): RLA 0 → 96°
                 ╲   REV IDLE detent = 51.5° RLA
                  ╲  (A/THR never available anywhere in reverse)

Three reading points. First, the A/THR activation range is drawn as two arcs: with both engines running it spans idle → CL; with one engine inoperative it extends to idle → FLX/MCT — after an engine failure, parking the live engine's lever in the MCT detent raises the autothrust ceiling by one notch (the hardware basis for the single-engine technique of article 25). Second, GA SOFT is annotated as a small region above the FLX/MCT detent — soft go-around is not a separate detent but a gesture (TOGA, then back to FLX/MCT — §5). Third, the lever heads carry the red A/THR instinctive-disconnect pushbuttons.

The AMM supplies the angle ledger: TLA runs 0° (idle stop) to 55° (MAX TO stop); the detents sit at CL = 30°, FLX/MCT = 42°, TOGA = 55°; A/THR can be electrically activated only between 0° and 44.20°, leaving 44.2°–55° purely manual; the reverse levers run 0–96° RLA with the REVERSE IDLE detent at 51.5° RLA, and A/THR is never available anywhere in the reverse sector.

From hand to electricity. The mechanical chain runs lever → upper rod → an artificial-feel unit (friction plus cam gearing, defining the gated feel positions) → lower rod → the throttle control unit (TCU), which converts angle to signal:

"The EEC interfaces with two throttle resolvers angle (TRA), one dedicated to each channel of the EEC. … The accuracy of the throttle control unit (error between the input lever position and the resolver angle) is 0.5 TRA. The maximum discrepancy between the signals generated by the two resolvers is 0.25 TRA."

Each lever carries two resolvers — one per EEC channel — and the 0.25-TRA consistency gate between them is the mechanical foundation of the THR LEVER DISAGREE alert in article 22. The TCU also houses a quiet but important switch wired to the EIVMU, closed when the reverse lever angle is below its threshold — the physical embodiment of "valid TCU data" that energises relay R4 in the reverser power chain (articles 06/13).

2. The rating-selection rule: round up

"If the thrust lever is set in a detent, the FADEC selects the rating limit corresponding to this detent. If the thrust lever is set between two detents, the FADEC will select the rating limit corresponding to the higher detent."

Rounding up is the conservative direction: an ambiguous lever position is charged against the higher rating limit, never the lower. The FCOM's accompanying figure adds a dynamic layer: the rating label displayed for the same lever region changes with aircraft state — on the ground with engines running, the region between CL and FLX/MCT displays FLEX (a takeoff context); in flight, the same region displays MCT/FLEX/GA SOFT (cruise and go-around contexts). The rating label on the E/WD is a function of lever position × flight state, not of lever position alone.

3. FLEX takeoff: a temperature comparison with a built-in trap

"If the flight crew enters a valid flexible takeoff temperature on the PERF TAKEOFF page and sets the thrust levers to the FLX/MCT detent, the engine will run at: ‐ The FLEX takeoff thrust rating mode if the flexible takeoff temperature is more than the current OAT, or ‐ The MCT rating mode if the flexible takeoff temperature is less than or equal to current OAT. Note: Any change on the flexible temperature during the takeoff has no effect on the thrust. The flight crew can always get the maximum available thrust by setting the thrust levers to the TOGA detent at any time."

The FLX ≤ OAT clause is a designed-in idiot-proof (synthesis): "pretending it is hotter" only means something if the pretended temperature is actually hotter — pretend it is cooler than reality and the system refuses to grant a takeoff rating on that basis, handing you MCT instead. The E/WD rating label will betray the error — which is precisely why checking the displayed takeoff rating is a meaningful crew action. And "changes during the takeoff have no effect" closes the other misuse: nobody edits the assumed temperature mid-roll and expects the thrust to follow.

4. DERATE — and the gear-change gesture after takeoff

DERATE works the same way at the lever: enter the derate level on the PERF TAKEOFF page, set the levers to FLX/MCT, and the derated rating applies. Changing the displayed rating from FLX to MCT after takeoff has a fixed hand movement:

"To change the thrust rating mode from FLX to MCT (on the EWD), the flight crew should move: ‐ The thrust levers either to TOGA or CL detent ‐ Then to FLX/MCT detent. Note: The flight crew must ensure that the detents are correctly reached in order to change the thrust rating mode. If not, there is no effect."

Why the detour (synthesis): FLX and MCT share one physical detent, so the system reads your departure and return as the signal that the meaning should change. A half-hearted movement that never seats in a detent counts for nothing — hence the note. And the availability of TOGA carries one crucial asymmetry:

"The flight crew can always get the maximum available thrust by setting the thrust levers to the TOGA detent: ‐ At any time for a flexible takeoff, or ‐ Above F speed for a derated takeoff."

This is the operational face of the limitation from article 00: DERATE's performance accounting — including VMC — is built around a smaller engine, and an impulsive TOGA at low speed would break that accounting. F speed is the unlock line (procedural demands such as windshear escape excepted, as the limitation itself states).

5. Soft go-around: a gentler GA

"The flight crew performs a soft go-around when the thrust levers are set to TOGA then to FLX/MCT detent: 1. The flight crew sets the thrust levers to the TOGA detent 2. Then, the flight crew sets the thrust levers to FLX/MCT detent. The engines apply: ‐ A computed thrust to a target vertical speed of approximately 2 000 ft/min, or ‐ TOGA if 2 000 ft/min cannot be reached."

The design intent (synthesis): a light-weight go-around at full TOGA routinely overshoots — aggressive pitch, ballooning altitude, a rushed level-off. Soft GA computes just enough thrust for roughly 2 000 ft/min, turning the manoeuvre composed — with the safety clause written in: if 2 000 ft/min cannot be achieved, the engines give TOGA anyway. Gentleness never costs climb capability. Soft GA is prohibited with one engine inoperative (article 00) — a single-engine go-around has no margin to spend on comfort. Note that this gesture — TOGA then back to FLX/MCT — is the same physical trajectory as the FLX→MCT gear change of §4 and the automatic-TOGA cancellation of §6: the flight phase disambiguates the meaning (go-around phase = soft GA; after-takeoff = rating change).

6. Automatic TOGA: a 3-second warning, a 5-second takeover, an 8-second gate

The scenario: neither FLEX nor DERATE has been entered in the FMS — today is a full-TOGA takeoff — but the levers are advanced only to the FLX/MCT detent. By the round-up rule the FADEC has selected TOGA as the takeoff rating; the lever position does not authorise it. The system responds in three beats:

"The ENG THR LEVERS NOT SET alert triggers 3 s after the flight crew sets the thrust levers to FLX/MCT detent … If the flight crew does not set the thrust levers to TOGA detent within 5 s (as requested by the ENG THR LEVERS NOT SET alert), then the automatic TOGA function will activate and the FADEC will automatically select the maximum available thrust (TOGA)."

"The automatic TOGA function activates when all of the following conditions are applicable for at least 8 s: ‐ The aircraft is on ground with the flaps and slats extended ‐ Neither a flexible nor a derated takeoff is entered on the PERF TAKEOFF page of the FMS ‐ At least one thrust lever is set to the FLX/MCT detent. The automatic TOGA function deactivates when one of the following conditions occurs: ‐ At least one thrust lever is set to either TOGA or CL detent, or ‐ The thrust reversers are selected."

The timeline assembles cleanly: levers into FLX/MCT → 3 s alert → a further 5 s grace (3 + 5 = 8, matching the "conditions for at least 8 s" gate) → the system gives TOGA on your behalf, averting the two bad endings the function exists to prevent — taking off on MCT, or rejecting unnecessarily. And here appears the article's single exception to "the blue circle follows the lever":

"As the automatic TOGA function controls the engine thrust in manual mode, the blue circle (also referred to as Thrust Lever Position on the EWD) will move to the maximum available thrust regardless of the current thrust levers position."

The blue circle divorcing the lever is the visual signature that automatic TOGA is managing your thrust (article 15 for display detail, article 22 for the NOT SET handling). The cancellation paths are worth noting: seating a lever in TOGA (completing the takeoff properly) or CL (accepting climb thrust) deactivates it — and so does selecting reverse (the rejected-takeoff path).

7. Automatic mode and the FMA

"In the autothrust mode (A/THR function active), the thrust is computed by the FMGC and is limited to the value corresponding to the thrust lever position (except if the alpha-floor mode is activated)." — "The FADECs monitor the positions of the thrust levers, and trigger appropriate indications on the FMA."

"Lever position = ceiling" has exactly one exception: alpha floor — stall protection takes whatever thrust it needs, ceiling ignored (an ATA-22 subject). The manual-mode definition completes the picture: manual thrust exists when A/THR is not armed, or armed but not active (levers outside the activation range and no alpha floor). Combined with the angle ledger of §1: two-engine A/THR territory = idle → CL (30°); single-engine = idle → FLX/MCT (42°); the electrical ceiling is 44.2°; the TOGA region and all of reverse are forever manual.

8. Where the lever meets the failure chapters

Self-test

[!note]- Q1. The lever sits between CL and FLX/MCT. Which rating limit does the FADEC use? FLX/MCT — the higher detent. Ratings round up, never interpolate.

[!note]- Q2. You entered FLX 48 °C but today's OAT is 50 °C. Levers to FLX/MCT — what rating appears? MCT. A flex temperature at or below OAT earns no FLEX rating — which is exactly why verifying the E/WD rating label at takeoff is a meaningful check, not a formality.

[!note]- Q3. After takeoff you want the E/WD to change from FLX to MCT. Can you nudge the lever within the FLX/MCT detent? No. The gesture is out to TOGA or CL, then back into FLX/MCT — and each detent must be positively reached, otherwise the change simply does not happen.

[!note]- Q4. What three conditions, sustained how long, arm automatic TOGA — and where does the blue circle go when it fires? On the ground with slats/flaps extended + no FLEX and no DERATE in the FMS + at least one lever in FLX/MCT — sustained ≥ 8 s (3 s to the alert, 5 s grace). When it activates, the blue circle moves by itself to maximum available thrust, regardless of where the levers physically sit.

[!note]- Q5. After an engine failure, where does the live engine's lever go, and does A/THR still work? Into MCT — with one engine out the A/THR active range extends from idle to FLX/MCT (two-engine range stops at CL). Above 44.2° TLA remains manual-only territory in all cases.

Key takeaways

References

• FCOM DSC-70 (thrust levers) — manual-only statement, segments and detents.
• FCOM DSC-70 (thrust rating selection) — the round-up rule and state-dependent labels.
• FCOM DSC-70 (thrust setting modes) — manual-mode definition, FLEX temperature comparison and mid-takeoff note, FLX→MCT gear change, TOGA availability asymmetry, soft GA, automatic TOGA conditions/timeline/blue-circle behaviour/deactivation, autothrust ceiling and FMA monitoring.
• AMM 76-11 (throttle control, D/O) — angle ledger (30/42/55/44.2; 96/51.5 RLA), mechanical chain and artificial feel, dual resolvers with 0.5 accuracy and 0.25 discrepancy gates, the TCU switch to the EIVMU.
• FCOM quadrant figures (read directly) — the two A/THR arcs, GA SOFT region, instinctive-disconnect buttons; rating-label state dependence.
• Integrative synthesis (marked in text): the ceiling/budget mental model; the round-up-as-conservatism reading; the FLEX idiot-proof; the out-and-back semantics; the soft-GA intent; the 3+5=8 timeline assembly.

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.