The engine oil system supplies filtered oil at the correct pressure and rate of flow to lubricate and cool engine areas The oil flows to the engine bearings and the related seals, splines, and gears inside the engine, and to the accessory gearbox. The oil system includes storage, distribution, and indicating subsystems.

The storage system includes an oil tank, which is an integral part of the accessory gearbox. Venting is done by an internal opening between the accessory gearbox and the oil tank. A sight gauge is attached to the side of the accessory gearbox. An oil filler port is also on the accessory gearbox. A magnetic drain plug drains the oil from the accessory gearbox.

The oil distribution system supplies clean, filtered oil at the correct pressure and flow rate to different areas of the engine to remove heat and lubricate engine components. The oil distribution system includes an oil pump, oil filter, chip detectors, gearbox breather adapter, oil vent tubes, and an oil drain mast manifold.

The oil pump moves oil through the engine and AGB. The oil filter removes contamination from the oil before the oil goes into the engine. The oil filter has an electrical impending/mechanical bypass valve, pressure relief valve, and pressure adjusting valve.

There are five chip detectors in the system: four magnetic collectors and one electronic debris clearing detector. Metal chips sensed by the electronic chip detector supply a resistance measurement to the ECU to show an advisory message on the EICAS.

The gearbox breather adapter lets unwanted fluid pass from the AGB, through an air/oil separator, to the oil drain mast manifold. Oil vent tubes supply drainage for each part of each engine fire zone and the pylons and are connected to the drain mast manifold. The oil drain mast manifold supplies overboard routing of unwanted fluids.

The oil pressure pump supplies oil from the oil tank to the filter. The oil then flows to the fuel heater/oil cooler (FHOC) to decrease the oil temperature. The oil flows through a filter screen and then to the supply manifold. The supply manifold distributes the oil to the front, aft, and AGB sumps, which apply the oil directly to the engine and AGB components. Oil is scavenged from the sumps by the oil pump. The oil goes through the scavenge screens and the pump, to the chip detector, and is returned to the oil tank. Air in the oil system goes through the tank pressurization valve, which keeps a small positive pressure in the oil tank. The air/oil separator, turned by gears in the AGB, isolates the air from the oil. The unwanted air is then released through the drain mast.

The oil indicating system monitors the condition of the oil filter, engine oil temperature, engine oil pressure, and the level of the oil in the oil tank. The impending bypass indicator, oil temperature transducer, and oil pressure transducer send data through the electronic control unit (ECU) to the engine indicating and crew alerting system (EICAS). The oil level probe sends a signal to the fuel quantity computer of the FMQGS to display oil level on the refuel/defuel control panel.

---