Engine Oil System — Pumps, Heat Exchangers, Low Pressure and Chip Detection

The fuel system's fuel/oil heat exchanger is where fuel and oil meet. This article takes the oil side: how oil is supplied to the bearings and gearboxes, how it is scavenged back, how it is cooled (two heat exchangers), and how it is monitored (pressure, temperature, quantity, metal chips). It is the basis for oil faults, bearing-related vibration and the maintenance view later, and it closes the foundation tier (00–05).

1. System components

The oil system lubricates the engine components. It contains the : ‐ Oil tank ‐ Lube and scavenge pump modules ‐ Fuel/oil and/or air/oil heat exchanger ‐ Filters, pressure relief and bypass valves.

Per DSC-70-50: oil tank, lube and scavenge pump modules, fuel/oil and air/oil heat exchangers, and filters with pressure-relief and bypass valves.

2. The oil circuit

Per the oil-system schematic:

 SUPPLY (lube):
   OIL TANK ─► OIL PRESSURE PUMP ─► PRESSURE RELIEF VALVE (535 PSI)
                                          │
                                     OIL FILTER (OIL CLOG→FADEC→ECAM)
                                          │
                            cooled by air/oil + fuel/oil heat exchangers
                                          │
                                  bearings / gearboxes (lubricated)

 SCAVENGE (return):
   6 return points (strainers): intermediate gearbox / internal gearbox ×2 /
     front bearing / HP-IP turbine bearing / LP turbine bearing
                                          │
   6 × SCAVENGE PUMPS ─► MASTER CHIP DETECTOR ─► SCAVENGE FILTER (OIL CLOG→FADEC→ECAM)
                                          │
                                       back to OIL TANK

 COOLING: fuel/oil HX + air/oil HX (each with a bypass valve; the air/oil bypass is FADEC-controlled)
 MONITORING: OIL PRESS (P→FADEC→ECAM) / OIL LOW PRESS (→ECAM) / OIL TEMP (T→FADEC→ECAM) / OIL QTY (→FADEC→ECAM)

From the schematic: six scavenge pumps, a 535 PSI pressure-relief valve, a master chip detector, and OIL CLOG monitoring on both the supply and scavenge filters.

3. Supply and pressure relief

The oil-pressure pump draws from the tank and pressurises; a pressure-relief valve set at 535 PSI caps the system pressure; oil is then filtered, cooled, and delivered to the bearings and gearboxes.

[!warning]- 535 PSI is a hardware relief setting, not the low-oil-pressure warning threshold The 535 PSI on the schematic is the mechanical setting of the pressure-relief valve (the system pressure ceiling) — not the ECAM OIL PRESS low-pressure threshold the crew watches. They are different layers (a hardware-action layer vs a field-warning layer). The warning threshold is resolved in Oil Faults from FCOM LIM; do not read 535 PSI as a warning value.

4. Scavenge and chip detection

Six scavenge pumps draw used oil from six return points (intermediate gearbox, internal gearbox ×2, front bearing, HP-IP turbine bearing, LP turbine bearing) through the master chip detector and scavenge filter, back to the tank.

[!note]- What the master chip detector means (integrative synthesis) The chip detector catches metallic debris in the oil — bearing or gear wear produces metal chips, so it is an early indicator of internal mechanical health (a maintenance item, see Maintenance View). This article only confirms its existence and location on the scavenge path; the wear criteria are not given on this schematic and are not inferred.

5. Dual heat exchangers

Oil is cooled by two heat exchangers — fuel/oil and air/oil, each with a bypass valve; the air/oil bypass valve is FADEC-controlled. The fuel/oil heat exchanger is the same unit seen from the fuel side: the oil is cooled while the fuel is warmed (anti-icing the fuel).

6. Monitoring

OIL QUANTITY — Green : The oil quantity is in normal range. The scale goes from 0 to 22 QT. Pulses green : The needle and the oil quantity value pulse green. The advisory limit is 4 QT.

Per DSC-70-90-40, the OIL QUANTITY scale is 0–22 QT, and at 4 QT it pulses green (an advisory, not a warning).

7. Counterintuitive points

[!warning]- 535 PSI (relief) ≠ low-oil-pressure warning ≠ 0–250 PSI (display scale) Three different oil-pressure numbers live in three layers: the 535 PSI pressure-relief setting (this article), the low-oil-pressure warning value (25), and the 0–250 PSI display scale (10). Never mix them.

[!warning]- 4 QT is an advisory, not a warning OIL QTY at 4 QT pulses green (DSC-70-90-40) — an advisory, not an amber/red warning. Mind the ECAM colour grading.

Self-test

[!note]- Q1. What are the oil system's main components? Oil tank, lube and scavenge pump modules, fuel/oil + air/oil heat exchangers, filters with pressure-relief and bypass valves.

[!note]- Q2. How many scavenge pumps, and from where? Six, from the intermediate gearbox, internal gearbox ×2, front bearing, HP-IP turbine bearing and LP turbine bearing.

[!note]- Q3. How is the oil cooled? By two heat exchangers — fuel/oil and air/oil — each with a bypass valve (the air/oil bypass is FADEC-controlled).

[!note]- Q4. How are metal chips detected, and what is the relief-valve setting? A master chip detector on the scavenge path; pressure-relief valve at 535 PSI.

[!note]- Q5. Oil-quantity normal range and advisory limit? 0–22 QT normal (green); at 4 QT it pulses green (advisory).

Key takeaways

References

• FCOM DSC-70-50 — oil-system components (tank, lube/scavenge pumps, dual heat exchangers, filters with relief/bypass valves).
• FCOM DSC-70-90-40 — OIL QUANTITY scale 0–22 QT, advisory 4 QT pulsing green.
• Oil-system schematic (FCOM) — six scavenge pumps, 535 PSI relief, master chip detector, dual heat exchangers (FADEC-controlled air/oil bypass), OIL PRESS/LOW PRESS/TEMP/QTY monitoring, dual OIL CLOG.

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.