Engine Fuel Faults
The fuel-side faults form an escalating chain: a clogged filter (contamination's first cough — single-engine, awareness) → both filters clogged, or both metering valves misbehaving (contamination diagnosed — ENG FUEL CONTAMINATED, LAND ASAP) → and the side branch, a jammed HP fuel valve (the switch itself broken). What makes the contamination scenario fearsome is that it attacks both engines by nature — two engines drinking from the same tank — which is why its procedure philosophy is unique in this syllabus: pin one engine, manoeuvre with the other.
1. FUEL FILTER CLOG — the first cough
"This alert triggers when the fuel filter is clogged. — Crew awareness. Maintenance action is due. The fuel filter is bypassed and short term engine operation is not affected. Dual fuel filter clog is likely an indication of fuel contamination."
The same bypass-preserves-flow design as the oil filter (article 30) — but the note's last sentence is the real hook: one filter clogged means that filter needs changing; both filters clogged means the fuel itself is the problem. Two independent filters blocking simultaneously can only share an upstream cause — what's in the tank. That sentence is the preview of trigger combination one below.
2. HP FUEL VALVE — a broken switch, two directions
"This alert triggers when fuel valve is failed in close, or open position. — Associated engine below idle: HP FUEL VALVE NOT OPEN — MAN START OFF / ENG MASTER OFF. — Associated engine at or above idle: HP FUEL VALVE NOT CLSD — Engine will shut down by closure of the fuel low pressure valve. MAN START OFF / ENG MASTER OFF — If the affected engine is still running 10 s after the engine master lever is set to OFF: ENG FIRE P/B PUSH. — Note: In case there is no fuel in engine fuel system, the high pressure fuel valve may be unduly detected open while being closed."
The two branches are the fault side of article 09's dual-valve shutdown chain. With the HP valve jammed open, the LP valve substitutes as the shutdown gate — the outer lock standing in for the inner one. But the LP valve sits upstream, so the line fuel between it and the nozzles still has to burn off (the same physics as the 1 min 30 s of article 24) — hence the 10-second observation window. Still running past it → the FIRE pushbutton, the LP valve's second command line (article 24's "second key" again).
The closing note guards maintenance against a misdiagnosis: a fuel system with no fuel in it cannot report valve position honestly — don't repair a "jammed-open valve" that is really a dry-system false reading.
3. ENG FUEL CONTAMINATED — diagnosis, and the pinned-thrust strategy
3.1 The trigger
"The ENG FUEL CONTAMINATED alert triggers 10 s after the following combination of alerts: ‐ Both fuel filters are detected clogged (ENG 1(2) FUEL FILTER CLOG alerts), or ‐ Both ENG 1 CTL SYS FAULT and ENG 2 CTL SYS FAULT alerts associated with ENG 1(2) SLOW RESPONSE in the case of FMV failure. … Note: (a) Inhibited during the first 60 s."
The two combinations are contamination's two targets (articles 09/19): the filters (particles blocking) and the fuel metering valves (the constant-ΔP precision spool seized by particles → metering astray → SLOW RESPONSE and EPR fluctuation). Ten seconds of debounce; the first 60 seconds after takeoff — the busiest interval — inhibited.
3.2 The ECAM procedure
LAND ASAP + A/THR OFF + the absolute prohibition: WING X FEED — DO NOT OPEN — crossfeeding would deliver contaminated fuel to the still-healthy supply line (the each-drinks-its-own discipline). Newer-batch aircraft add centre-pump OFF / trim-tank forward transfer / centre tank unusable. Then two handling rules: AVOID RAPID THR CHANGES and MOVE THR LVR ONE BY ONE — at every moment, one engine holds stable thrust (the same philosophy as the 30-second offset of article 29).
3.3 The QRH confirmation logic — autothrust as a reagent
"If ENG 1(2) CTL SYS FAULT alert triggered … with rapid and continuous EPR fluctuation indications on both engines: A/THR OFF — If EPR fluctuations stop on both engines: ECAM PROC APPLY / A/THR KEEP OFF — If EPR fluctuations continue on both engines: FUEL CONTAMINATION CONFIRMED."
One alert but both EPRs fluctuating: switch the autothrust off as a test reagent. Fluctuations stop = they arose from the interplay between the autothrust and a mis-metering engine — not contamination; follow ECAM, keep the autothrust off. Fluctuations continue = contamination confirmed. (Both alerts together = confirmed directly.)
3.4 The pinned-thrust strategy
"MAN THR (1st affected engine) SET and MAINTAIN — MAINTAIN THRUST UNTIL FINAL APPROACH."
The thrust setting comes from an N1 table by gross weight — 120 t → 58.1 %, 150 t → 60.1 %, 180 t → 62.5 %, 210 t → 65.0 %, 240 t → 67.7 %. In cruise, the other engine is set as required, minimising thrust changes. For descent: other engine to idle, speedbrakes as required, levelling off at approximately 3 000 ft AGL and 20 NM from the threshold. For landing: resume normal SOPs, FLAP FULL — and once fully configured:
"‐ In case of overspeed adjust the thrust on the 1st affected engine ‐ If the speed trend decreases below VAPP, adjust the thrust on the other engine."
Three layers of logic in the strategy (synthesis): ① N1, not EPR — EPR is the fluctuating symptom (the metering valve astray); N1 is the only trustworthy thrust ruler left (article 07 applied in anger). ② Pin one engine — converting two unstable engines into one constant pedestal plus one manoeuvring throttle: energy management returns to a single variable. ③ The final-approach division of labour splits the risk: overspeed → reduce the pinned (affected) engine (its response is already unreliable; a small reduction has bounded downside); speed trend decaying below VAPP → add on the other engine (recovering speed demands a reliable response). One engine, one direction, at a time.
4. Scenario walk-throughs
Cruise, both fuel flows rising together, both EPRs trembling. The alerts haven't assembled yet — but your common-cause radar should already be sounding: this is about the fuel.
Contamination confirmed, gross weight 210 t. Pin the affected engine at 65.0 %, hand the energy problem to the other engine, and start the 3 000 ft / 20 NM geometry.
Final approach, gusting +10. Speed ballooning: take two percent off the pinned engine and steady it. Short final, speed decaying: the other engine answers — immediately, because that's the reliable one.
After landing. That tank's fuel, both engines' filters, and both metering valves all go under inspection — the aircraft-side fuel chapter takes the baton.
Self-test
[!note]- Q1. One clogged fuel filter versus two — the essential difference? One = that filter needs changing (the bypass carries it; awareness). Two = a shared upstream problem — the fuel — which is exactly trigger combination one of ENG FUEL CONTAMINATED.
[!note]- Q2. With the HP valve jammed open, how does the engine stop? And if it won't? The LP valve substitutes (the outer lock of the dual-valve chain) — the engine stops when the line fuel burns off. Still running 10 s after MASTER OFF → ENG FIRE pushbutton (the LP valve's second command line).
[!note]- Q3. One alert plus dual-engine EPR fluctuation — how is the autothrust used as a discriminator? Switch it off as a reagent: fluctuations stop = the interplay was the cause (not contamination; follow ECAM, A/THR stays off); fluctuations continue = contamination confirmed, into the pinned-thrust procedure.
[!note]- Q4. Gross weight 195 t — what N1 is the affected engine pinned at, and until when? Interpolating the table ≈ 63.7 % (190 → 63.3, 200 → 64.1); held until fully configured on final approach — only then does the two-way division of labour begin.
[!note]- Q5. Overspeed on final — which engine do you adjust, and why? The pinned (first affected) engine — its response is already unreliable, and a small reduction has bounded downside. Only a speed trend below VAPP earns an addition on the other engine, where reliable response matters. One engine, one direction, at a time.
Key takeaways
| Topic | Essentials |
|---|---|
| The chain | one filter = a cough · both filters or both FMVs = diagnosis (LAND ASAP) · jammed HP valve = the side branch |
| Trigger | two combinations, 10 s debounce, first 60 s inhibited |
| Prohibitions | WING X FEED never — each engine drinks its own; levers one at a time; no rapid thrust changes |
| Reagent | A/THR off: fluctuations stop = interplay; continue = contamination confirmed |
| Pinned thrust | N1 table by weight (58.1–67.7 %), held to final; other engine manoeuvres; 3 000 ft AGL / 20 NM level-off |
| Division of labour | overspeed → reduce the pinned engine · below VAPP → add on the other |
| HP valve | LP valve substitutes; 10 s window; FIRE pb as second key; dry systems misreport valve position |
References
- FCOM PRO (engine abnormal procedures: FUEL FILTER CLOG; HP FUEL VALVE both branches; ENG FUEL CONTAMINATED both fleet versions — triggers, ECAM procedure, configuration items) — quoted verbatim.
- QRH (engine fuel contaminated) — the reagent logic, the N1 pinned-thrust table (key values transcribed; full table per the QRH), the energy profile, the two-way division of labour.
- Integrative synthesis (marked in text): the shared-upstream inference; the three-layer logic of the pinned-thrust strategy; the 195 t interpolation example.
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.