I A P 2 0 2 3 . 0 0 1 - A F M / I R I S T E X A N I I P A G E | 24
FOR SIMULATION USE ONLY – NOT A TRAINING AID
scavenged oil from the bearings and gearbox. Cooling is accomplished by routing
scavenged oil through an oil cooler located in the lower aft cowl assembly before
returning to the oil tank.
The oil tank, integrally cast with the compressor air inlet, is vented into the
accessory gearbox by a four-point breather system that includes a breather valve
and centrifugal breather. The engine oil pressure indicator may display oil
pressures up to 4 psi with the engine shut down due to the design of the oil
pressure transmitter.
The oil is filtered by the main oil filter and then by several oil strainers. If the main
oil filter becomes clogged, a filter bypass valve allows unfiltered oil to continue to
lubricate the engine.
Oil pressure and temperature are sensed by transducers downstream of the main
oil pump and the signal is sent to the engine data manager (EDM). The EDM passes
the oil pressure data to a signal conditioning unit (SCU) computer that contains the
logic to illuminate the warning on the engine indication and crew alerting system
(EICAS) under the following conditions.
The SCU activates the red OIL PX warning if oil pressure drops to 40 psi or below
when above idle power, or when oil pressure drops to 15 psi or below at idle power.
Additionally, the SCU illuminates the amber OIL PX caution whenever sensed oil
pressure is between 15 and 40 psi at idle power, and if the oil pressure drops to
between 40 and 90 psi, for 10 seconds, above idle power.
If oil pressure is less than 15 psi at idle power, the amber OIL PX caution
extinguishes and the red OIL PX warning remains illuminated. If oil pressure
remains between 15 and 40 psi at idle power for 5 seconds or more, both amber
and red OIL PX caution/warning illuminate.
NOTE
Due to the sensitivity of the signal conditioning unit, a single, momentary
illumination of the amber OIL PX caution while manoeuvring is possible but
may not indicate a malfunction.
The SCU contains logic to prevent nuisance caution illumination on the EICAS from
normal oil pressure build-up during engine ground start.
Illumination of both red and amber OIL PX caution/warning while the oil pressure
gauge indicates normal pressure indicates an SCU failure.
To Next Page
Loading...