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
