TM 1-1520-240-102-3-16 Table 2-3-1. T55-GA-714A DECU BIT Fault Code List/Matrix (Continued)DECU FaultCode(s)FaultOperational EffectPilot ActionMission ImpactFF(all otherBIT checks)DECU internal fault.N/AN/AAbort MissionHex DisplayBlank(on Pre-startBIT check)N/AN/AMove PRI/REVswitch to PRI.Then cycle back-up power.Continue Missionif 88Hex DisplayBlank(all otherBIT checks)DECU internal fault.N/AN/AAbort Mission2-3-41. Engine Air Particle Separator (EAPS).The engine air particle separating system (EAPS)systemprotects the engine from harmful effects of dust and sanderosion, snow and foreign objects and salt spray foulingand corrosion. The system removes contamination fromthe air and exhausts it overboard continuously using ascavenge system. The EAPS assembly is mounted onrails which enable it to be easily moved to permit engineinspections. During flight, the assembly is locked in theaft position against the engine inlet with two lock pinsinstalled through the rails at the forward mounting blocksof the unit.The basic axial flow of contaminated air entering thevortex tube is forced into a spiral flow by the fixed bladesof the EAPS fan. The swirling motion causes the heavierdirt particles to be separated from the air stream by virtueof their inertia. The particulate is thrown outwards to theperiphery of the vortex tube by centrifugal force, concen-trated into the scavenge air flow, and ducted away fordischarge. The bulk of the air flow, from which the particu-late has been separated, passes axially down the centerfor the outlet tube.The EAPS control panel, located on the overhead panel,provides control of the EAPS with a FAN ON/OFF switchand DOORS CLOSE/OPEN switch for each engine. Theswitches are marked for ENG 1 and ENG 2 and receivetheir power from the No. 1 and No. 2 28-volt DC busesthrough the NO 1 EAPS and NO 2 EAPS FAN CONTcircuit breakers. When the FAN switch is placed in theON position, the fan is operating and providing particu-late separation to that engine. Power to operate the fansis provided by the No. 1 and No. 2 115-volt AC busesthrough the NO 1 EAPS and NO 2 EAPS FAN circuitbreakers on the respective PDP’s.The EAPS has a high electrical power requirement. Be-cause of this, both EAPS fans should not be turned onsimultaneously. Allow 10 - 15 seconds between the firstand second fan activation.2-3-42. EAPS Bypass Doors.The EAPS is provided with a by-pass mechanism whichenables the engine to continue run in the event of ablockage of the EAPS unit due to airborne debris block-ing the separator. Two by-pass doors resembling curvedrectangular panels (fig. 2-3-9) are mounted flush with theouter surface of the EAPS and opened by electronicactuators. The door mechanism includes two tubularguide rods per door to achieve a smooth transitionalmovement along with structural strength and stiffness.When the EAPS ENG 1 or 2 DOORS switch is placed inthe OPEN position, the two bypass doors for that side areactivated, bypassing engine air around the separatorinlet. In snow and icing conditions the by-pass doorsmust be kept in the closed position, otherwise ice may beinjected into the engine. Power to operate the by-passdoors are supplied from No. 1 and No. 2 28-volt DCbuses through the EAPS 1 and EAPS 2 BYPASSDOORS circuit breakers.CAUTIONThe by-pass door must be kept closedduring snow and icing conditions other-wise ice may be injected into the enginecausing possible damage or failure.CAUTIONWith EAPS installed and the bypass pan-els open FADEC primary channel may failwhen rearward airspeed exceeds 40 knotsairspeed or 40 knots tailwind. These con-ditions should be avoided.2-3-43. EAPS Control Boxes.EAPS control boxes (fig. 2-3-10) are installed in the cabinRH side at station 415 and LH side at station 390. Eachbox contains press-to-test lights labeled EAPS NO. 1BYPASS DOORS OPEN and EAPS NO. 2 BYPASSDOORS OPEN. They illuminate when their respective
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