Oil System Faults

Article 10 told the oil system as circulation plus pathology lab. This article is the lab report's five abnormal findings: pressure low (perfusion failing — the most urgent), temperature high (heat rejection losing), temperature low (the blood too thick), filter clogging (purification losing), and chips detected (an organ shedding metal). The handling intensities span the whole scale — from "awareness" (CHIP) to "idle, and if it persists, shut down" (LO PR) — and the intensity ordering is itself the lesson.

1. OIL LO PR — the hardest line of the five

"This alert triggers when the oil pressure is lower than 25 PSI. — THR LEVER (AFFECTED ENGINE) IDLE / IF WARNING PERSISTS: ENG MASTER OFF."

The triple identity of 25 PSI converges here (articles 00/10/15): the limitations minimum = the display red-band ceiling = the alert trigger. Why this alert is the hardest (synthesis, via article 10): its trigger chain is a vote — dual transmitters plus the independent low-pressure switch, the "indication and warning live apart" design — so this warning almost never accuses an innocent engine. And oil pressure is the herald of a minutes-scale disaster: a bearing running dry grinds itself to destruction on a very short clock.

The retard-and-wait logic matches article 28's: pump pressure scales with rotor speed, so if the low reading was a true shortfall at high speed, idle lets the pressure ledger re-balance. Still warning at idle = truly out of oil or pressure → shut down to save the bearings — while the engine can still stop gracefully.

2. OIL HI TEMP — the philosophy of REDUCE

"This alert triggers when the engine oil temperature is above 190 °C. — For aircraft equipped with RR engines: THR LEVER (AFFECTED ENGINE) REDUCE — Gradually reduce thrust on the affected engine in order to decrease oil temperature below the limit. — If the caution persists with the thrust lever at idle: ENG MASTER OFF."

REDUCE versus IDLE — one word of difference, a whole thermodynamics lesson (synthesis). The heat source is bearing friction (proportional to speed and load); the heat sinks are the two heat exchangers of article 10. Reduce a little, watch a little — the heat balance often recovers well short of idle, preserving thrust margin. And the measurement point sits in the scavenge return — the hottest point, with lag — so the gradual reduction also prevents overshoot. The failure line is congruent with LO PR's: if idle still can't hold it, the heat-rejection system is genuinely broken (the AOHE — a near neighbour of article 20's AIR EXCHANGER FAULT) → shut down.

3. OIL LO TEMP — two thresholds, and a check that waits for the exam

"This alert triggers when the engine oil temperature is lower than 20 °C." (On one fleet configuration: lower than 50 °C.) "Note: In phases 2 and 9, the warning will not be triggered, unless the T.O CONFIG pb is pressed. — THR LEVER (AFFECTED ENGINE) IDLE / DELAY T.O. FOR WARM UP."

A configuration trap worth a careful read: two thresholds coexist across the fleet (most aircraft 20 °C; one configuration 50 °C), while the limitation of article 00 — minimum 50 °C before takeoff — applies to every aircraft. The alert line is not the limit line: on a 20 °C-threshold aircraft, a silent ECAM does not certify you legal for takeoff — the oil temperature check is yours, not the warning computer's.

The phases-2/9 note is the FWC's "pre-exam check" logic (synthesis): cold oil during ground phases is ordinary and not worth announcing; press T.O CONFIG — declare you are about to sit the exam — and only then does this item step forward to stop you. The handling is one word: wait (warm up, delay the takeoff).

4. OIL FILTER CLOG — the monitoring duty after the bypass

"This alert triggers when the oil filter is clogged. — OIL PR MONITOR — Maintenance action is due."

The second half of article 10's "dirty flow beats no flow": a clogged filter opens its bypass, and flow never stops. Then why watch oil pressure (synthesis)? Because an open bypass means the system is running with contamination aboard. If the debris is heavy enough to threaten even the bypass path — or if the clogging's source is itself failure debris — the next indicator to fall is pressure. This caution deputises you as the human second-stage differential-pressure monitor.

5. OIL CHIP DETECTED — the electronic chip report

"This alert triggers when the metal particles are detected in the oil system. — Crew awareness."

This alert's very existence depends on configuration (article 10): the electric master chip detector activated by service bulletin reports chips in real time — without it, metal debris waits for the cap to come off on the ground. The awareness grade is proportion, not complacency: a chip is not a verdict — quantity, morphology, and origin decide everything. After landing, maintenance walks article 10's master-then-branch localisation (the master detector saw it; the six line detectors say which chamber). Your contribution is the accompanying evidence: the vibration trend (oil film and vibration are coupled — articles 10/29), the pressure and temperature curves, and the event's timestamp.

6. The intensity ladder — one closing table

7. Scenario walk-throughs

Cruise, oil pressure drifting down to 27 PSI. Nothing has triggered — but article 10's trend-and-distance instinct has already raised your internal alert.

Midsummer long climb, HI TEMP. Reduce moderately; the temperature settles to 185 °C — log it, continue, and report the AOHE running at its margin.

Cold-night first sector, T.O CONFIG pressed, LO TEMP appears. Back to the warm-up rule: 50 °C or better before you roll.

CHIP and VIB rising together. Two clues pointing at the same chamber multiply each other's worth — report them as one story, not two.

Self-test

[!note]- Q1. Why does OIL LO PR almost never accuse an innocent engine? Its trigger is a vote — dual transmitters plus the independent low-oil-pressure switch (article 10's indication/warning separation). And 25 PSI is simultaneously the limitation, the red-band boundary, and the trigger — three identities, one number.

[!note]- Q2. Oil temperature 195 °C — where does the lever go? Not straight to idle — REDUCE, gradually, watching the response: the heat balance often recovers at moderate thrust, and the laggy scavenge-side measurement punishes overshoot. Only "persists at idle" earns the shutdown.

[!note]- Q3. The two LO TEMP thresholds, and their relation to the takeoff limitation? Most aircraft trigger at 20 °C, one configuration at 50 °C — while the limitation (minimum 50 °C before takeoff) binds the whole fleet. Alert line ≠ limit line: on a 20 °C aircraft, ECAM silence is not takeoff legality.

[!note]- Q4. Why is the filter-clog action "monitor oil pressure" and nothing else? The bypass preserves flow but the system now runs contaminated — pressure is the next indicator on the sick chain to fall. You are the second-stage monitor.

[!note]- Q5. After CHIP DETECTED, maintenance's first move — and your homework? The master-then-branch localisation (master chip detector → six line detectors → which chamber). You hand over: the VIB trend, the pressure/temperature curves, and the event time — narrowing six to one.

Key takeaways

References

• FCOM PRO (engine abnormal procedures: OIL LO PR / OIL HI TEMP / OIL LO TEMP with its configuration thresholds and phase note / OIL FILTER CLOG / OIL CHIP DETECTED) — all five quoted verbatim; other-engine-type entries excluded per type discipline.
• Mechanisms via article 10: the voting chain, the differential-pressure regime, the bypass, the chip-detector hierarchy, the heat exchangers, the scavenge-side measurement point.
• Integrative synthesis (marked in text): the minutes-scale-disaster reading; the REDUCE thermodynamics; the alert-vs-limit distinction and pre-exam logic; the second-monitor deputisation; the accompanying-evidence list.

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.