Thrust Lever Faults

Article 08 established that every thrust lever speaks through two resolvers — one per FADEC channel — cross-checked against a consistency threshold. This article covers what happens when that dual-signal system fails: the two signals disagree (THR LEVER DISAGREE — one of them may still be correct, but there is no way to tell which) and both signals are lost outright (THR LEVER FAULT — the lever position becomes unknowable).

The FADEC's philosophy is consistent throughout: when it cannot tell what you want, it gives the thrust least likely to hurt you for the current flight phase — generous in the air (frozen around CLB; too little thrust is more urgent than too much), conservative on approach (gear or slat extension commands idle automatically; you cannot land with a runaway). Both DISAGREE and FAULT carry LAND ASAP in their applicable branches — the attribution previewed in article 18, confirmed here.

1. THR LEVER ABV IDLE — the asymmetry reminder at landing

"This alert triggers when: ‐ One thrust lever is above idle while the other thrust lever is in the reverse detent at landing. ‐ One thrust lever is above idle while the other thrust lever is at idle at landing. — THR LEVER (AFFECTED ENGINE) IDLE."

The plainest alert in the family: you have landed, both levers should have come home together, and one is still standing — usually a hand that didn't carry it all the way. The system calls it out. What it prevents is the single-sided version of the embarrassment that article 13's interlock excludes: one side in reverse while the other still pushes forward.

2. THR LEVER DISAGREE — two resolvers, two stories (LAND ASAP)

"This alert triggers when a discrepancy between both resolvers of a thrust lever is detected."

The alert-shaped incarnation of article 08's consistency threshold. The FADEC cannot tell which signal is right, so it takes over that engine's thrust by flight phase — the full logic reconstructed:

The heart of the procedure is summoning the autothrust:

"If A/THR is ON: KEEP ON / If A/THR is not ON: A/THR ON — With A/THR active, thrust is automatically managed between idle and the highest TLA position as long as the landing gear is up."

The lever's signal is no longer trustworthy — but the autothrust command chain never passes through the lever (articles 04/06: the flight-management computer's EPR target travels via the EIVMU). When the human hand breaks, you substitute the autopilot's hand. If that engine's EIVMU has also failed (severing the autothrust chain too), a fallback closes the story by Mach number: automatic idle below Mach 0.33 (the Trent 700 value). The STATUS page completes the approach picture: FLAP LVR 3 / LDG DIST PROC APPLY; INOP: that side's THR LVR, and GA SOFT where fitted.

3. THR LEVER FAULT — both resolvers gone (LAND ASAP)

"This alert triggers when both resolvers on one thrust lever are failed."

One layer deeper than DISAGREE: there is no longer even a pair of signals to arbitrate. On the ground the case is STUCK AT IDLE — the FADEC idles the engine automatically, and a deployed reverser is commanded back to stow (with the lever's signal lost, the reverser command chain is severed with it, article 13). In flight, the outcome splits by where the lever was at the moment of failure:

"TOGA or FLEX: FADEC freezes takeoff or flex takeoff thrust until slat retraction. At slat retraction, the FADEC selects CLB thrust. / Between IDLE and MCT: In manual thrust setting mode, engine rating increases and freezes at CLB thrust. At slats or landing gear extension, FADEC selects idle power automatically. / It is possible to activate the A/THR. If selected, A/THR mode will manage thrust between idle and CLB as long as the landing gear is up and the slats are in."

"Increases and freezes at CLB" is the most counter-intuitive detail in this family (synthesis): the lever failed at a low position, yet thrust actively rises — because in flight, when the system doesn't know how much you want, a thrust deficit (losing altitude, losing speed) is more dangerous than a surplus. CLB is the floor that flies every phase. The two extreme branches:

• STUCK AT IDLE — failed while already at idle, or slats/gear already extended: that engine flies the remainder as an idle engine.
• HI PWR ONLY — "If EIVMU not avail and FLX/MCT/TOGA selected — Engine thrust is frozen at takeoff power." The triple stack: lever signals all gone + the EIVMU interface down (so the autothrust rescue chain is severed too) + the lever at a high position at failure. The FADEC can only conservatively pin thrust at the moment-of-failure high value. How do you land an engine that only knows how to run flat out? By choosing the moment to shut it down with the MASTER — the special single-engine-approach case of article 25; its on-ground cousin is the non-standard shutdown paper procedure of article 24.

STATUS closes the same way: FLAP LVR 3 / LDG DIST PROC; INOP: THR LVR + REV 1(2) + GA SOFT — the reverser is lost together with the lever.

4. THR LEVERS NOT SET — the takeoff rating and the lever don't match

"This alert triggers when at least one FADEC engaged a takeoff thrust mode that is not in accordance with the position of the thrust levers. Note: 1. The takeoff thrust mode is engaged when the flight crew sets the thrust levers above the CL position. 2. The flex thrust mode is armed only if the flight crew entered a FLEX TO TEMP on the MCDU that is above the OAT. 3. The derate thrust mode is armed only if the flight crew entered a DERATE level on the MCDU."

Four branches, one principle — the lever goes where it belongs:

Spliced with article 08's timeline, the picture completes: 3 seconds of warning (this alert) → 5 more seconds uncorrected → auto-TOGA takes over — but only in the "reduced thrust not armed" cases. A wrong lever position with FLEX or derate properly armed has no auto-TOGA safety net; this four-branch table is your correction guide.

5. The family in one table

6. Scenario walk-throughs

Cruise, DISAGREE. Engage the autothrust and let it take over — and file "gear extension = that engine goes to idle" into the approach briefing now: the single-engine-approach mindset of article 25 starts building early.

FAULT just after takeoff, lever was at FLEX. Thrust will rise to CLB and freeze on slat retraction. Recognise it for what it is — the designed behaviour, not a runaway.

FAULT and EIVMU FAULT together. Recognise the face of HI PWR ONLY: this engine will fly at takeoff power until the moment you shut it down. The descent and approach strategy reorganises around choosing that moment (article 25).

NOT SET during the takeoff roll. The principle is "go where it belongs": check the MCDU armed state against the four-branch table, lever in position within the 3 seconds.

Self-test

[!note]- Q1. DISAGREE vs FAULT in one line each? DISAGREE = the two resolver signals disagree (one may still be correct, but unidentifiable). FAULT = both signals lost — the lever position is unknowable.

[!note]- Q2. In-flight DISAGREE — maximum available thrust? When does it drop to idle automatically? CLB (highest TLA, capped at CLB). Landing gear extension commands automatic idle; on go-around, the CLB ceiling returns after nose gear retraction.

[!note]- Q3. Lever FAULT during takeoff with the lever at TOGA — when does thrust come down? Takeoff thrust is frozen until slat retraction, then CLB. The design logic: in the takeoff phase, err on the side of more thrust.

[!note]- Q4. How does HI PWR ONLY stack up? THR LEVER FAULT + that side's EIVMU unavailable + lever at FLX/MCT/TOGA at failure. The autothrust rescue chain is severed too, so thrust is pinned at takeoff power — the only remaining thrust management for that engine is the MASTER lever.

[!note]- Q5. Why can the autothrust rescue both LAND ASAP faults? Because its command chain (flight management → EIVMU → EEC) never passes through the thrust lever — a dead lever doesn't touch it. Engaged, it manages thrust automatically between idle and the ceiling (DISAGREE: highest TLA; FAULT: CLB, gear up and slats in).

Key takeaways

References

• FCOM PRO (engine abnormal procedures: THR LEVER ABV IDLE; THR LEVER DISAGREE complete section incl. phase logic, A/THR rescue, Mach fallback, STATUS/INOP; THR LEVER FAULT complete section incl. branch logic, STUCK AT IDLE / HI PWR ONLY, reverser restow, INOP incl. REV; THR LEVERS NOT SET with its three notes and four branches) — quoted verbatim. Trent 700-applicable Mach values taken per engine-type discipline.
• Integrative synthesis (marked in text): the generous-in-air / conservative-on-approach philosophy; the substitute-hand reading of the A/THR rescue; the rise-to-CLB design logic; the MASTER-timing preview for HI PWR ONLY.

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.