TM  1-1520-240-10 2-3-16            Table  2-3-1. T55-GA-714A DECU BIT Fault Code List/Matrix (Continued) DECU Fault Code(s) Fault Operational Effect Pilot Action Mission Impact FF (all other BIT checks) DECU internal fault. N/A N/A Abort Mission Hex Display Blank (on Pre-start BIT check) N/A N/A Move PRI/REV switch to PRI. Then cycle back- up power. Continue Mission if 88 Hex Display Blank (all other BIT checks) DECU internal fault. N/A N/A Abort Mission 2-3-41.  Engine Air Particle Separator (EAPS). The engine air particle separating system (EAPS)system protects the engine from harmful effects of dust and sand erosion, snow and foreign objects and salt spray fouling and corrosion. The system removes contamination from the air and exhausts it overboard continuously using a scavenge system. The EAPS assembly is mounted on rails which enable it to be easily moved to permit engine inspections. During flight, the assembly is locked in the aft position against the engine inlet with two lock pins installed through the rails at the forward mounting blocks of the unit. The  basic  axial  flow  of  contaminated  air  entering  the vortex tube is forced into a spiral flow by the fixed blades of the EAPS fan. The swirling motion causes the heavier dirt particles to be separated from the air stream by virtue of their inertia. The particulate is thrown outwards to the periphery of the vortex tube by centrifugal force, concen- trated into the scavenge air flow, and ducted away for discharge. The bulk of the air flow, from which the particu- late has been separated, passes axially down the center for the outlet tube. The EAPS control panel, located on the overhead panel, provides control of the EAPS with a FAN ON/OFF switch and DOORS CLOSE/OPEN switch for each engine. The switches are marked for ENG 1 and ENG 2 and receive their power from the No. 1 and No. 2 28-volt DC buses through the NO 1 EAPS and NO 2 EAPS FAN CONT circuit breakers. When the FAN switch is placed in the ON position, the fan is operating and providing particu- late separation to that engine. Power to operate the fans is provided by the No. 1 and No. 2 115-volt AC buses through the NO 1 EAPS and NO 2 EAPS FAN circuit breakers on the respective PDP’s. The EAPS has a high electrical power requirement. Be- cause of this, both EAPS fans should not be turned on simultaneously. Allow 10 - 15 seconds between the first and second fan activation. 2-3-42.  EAPS Bypass Doors. The EAPS is provided with a by-pass mechanism which enables  the  engine  to  continue  run  in  the  event  of  a blockage of the EAPS unit due to airborne debris block- ing the separator. Two by-pass doors resembling curved rectangular panels (fig. 2-3-9) are mounted flush with the outer  surface  of  the  EAPS  and  opened  by  electronic actuators.  The  door  mechanism  includes  two  tubular guide  rods  per  door  to  achieve  a  smooth  transitional movement along with structural strength and stiffness. When the EAPS ENG 1 or 2 DOORS switch is placed in the OPEN position, the two bypass doors for that side are activated,  bypassing  engine  air  around  the  separator inlet.  In  snow  and  icing  conditions  the  by-pass  doors must be kept in the closed position, otherwise ice may be injected into the engine. Power to operate the by-pass doors  are  supplied  from  No.  1  and  No.  2  28-volt  DC buses   through   the   EAPS   1   and   EAPS   2   BYPASS DOORS circuit breakers. CAUTION The  by-pass  door  must  be  kept  closed during snow and icing conditions other- wise ice may be injected into the engine causing possible damage or failure. CAUTION With EAPS installed and the bypass pan- els open FADEC primary channel may fail when rearward airspeed exceeds 40 knots airspeed 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 cabin RH side at station 415 and LH side at station 390. Each box  contains  press-to-test  lights  labeled  EAPS  NO.  1 BYPASS  DOORS  OPEN  and  EAPS  NO.  2  BYPASS DOORS OPEN. They illuminate when their respective