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move the ENG COND levers.
The ENG COND panel is located in the overhead switch
panel (fig. 2-3-5).
NO.1 and NO. 2 ENG COND Levers. The ENG COND
Levers (ECL) provide the pilot with proportional acceleration
and deceleration authority. The ECLS are springloaded
outboard creating a gated motion when advanced
from the STOP to GND and to FLT positions.
ENG COND lever friction is provided to reduce the possibility
of over-torque transmissions by resisting rapid
movement of the levers.
2-3-32. FADEC Panel. 714A
The FADEC panel is located on the overhead switch
panel (fig. 2-3-6). It comprises of the following:
a. NR % Switch. The NR% switch controls a rheostat
which allows the operator to select any RRPM between
97% and 103%. There are detents at 97%. 100%
and 103%. With the ECL(s) in FLT, NR will be maintained
at the selected speed. 100% is the normal position.
b. PRI/REV Switches. The primary mode is the normal
mode of operation. The REV (reversionary) mode is
selected as a backup mode or is automatically selected
if the primary system has a hard fault failure. A hard fault
failure is defined as one in which normal primary system
performance might be jeopardized. Other failures are
classified as soft failures when the system is fault tolerant
and can continue fully operational with the fault signal
present.
c. BU/PWR Switch. The Back-Up Power switch
when ON connects the aircraft battery relay and essential
relay.
Figure 2-3-5. Engine Condition Panel 714A
TM 1-1520-240-10
2-3-9
This provides the FADEC system with back up electrical
power in the event of a HMU integral alternator failure
thus preventing loss of the PRI mode. Placing the B/U
PWR switch to OFF will reduce operating time on the
FADEC circuitry. The B/U PWR switch should always be
ON during engine operation.
d. OSPD 1, 2 Switch. The Over Speed test switch is
a three position switch used to test the FADEC overspeed
system. In the event of a NR overspeed of 114.8
percent, FADEC reduces fuel flow to a ground idle condition.
The system remains activated until the overspeed
condition no longer exists, and will re-activate as soon as
an overspeed re-occurs. The system contains provisions
to inhibit overspeed trip command if the other engine has
experienced a overspeed trip condition. To prevent inadvertent
operation during flight, this test is locked out if NR
is greater than 81.3 percent. When performing an overspeed
test with the engine running and the RRPM
79.01%, pressing the test switch to 1 or 2, lowers the
overspeed trip threshold to 79.01% NR. At this time the
system senses an overspeed and reduces the fuel flow.
e. LOAD SHARE, PTIT/TRQ Switch. The primary
FADEC system provides pilot selectable engine torque
PTIT matching to govern the engines. Torque matching
is normally the preferred option. The selected parameter
is constantly compared between the two engines until the
RRPM stabilizes at datum figure. The PTIT option may
be used when one engine is running hot. N1 matching is
engaged automatically if the selected matching mode
fails.
f. ENG START Switch. It is a three position switch,
spring loaded to the center position, labeled 1 and 2. It is
used to commence the start sequence on the respective
engine.
2-3-33. DECU Unit. 714A
The two airframe mounted DECU’s, one for each engine,
contain the primary and reversionary mode electronics.
The DECUs are located on the left (sta 390) and right (sta
410) side of the aft cabin.
Figure 2-3-6. FADEC Panel 714A
2-3-34. BIT. 714A
The DECU contains a two-digit BIT display. When active,
the display indicates the operating status of the FADEC
system and power assurance test results. A complete list
of the FADEC BIT fault codes are located at Table 2-3-1.
The fault monitoring carried out by the DECU consists of:
a. Power up tests.
b. Fault tests designed to discover dormant faults.
c. A set of repeated monitoring tests to detect faults
occurring during normal operation.
Fault information for the previous or current engine cycle
can be seen on the DECU BIT display. The last engine
cycle is reset on the first occurrence of start mode and not
on engine shutdown. During engine shutdown (when
ECL is at STOP or N1 is less than 10 percent) faults are
not stored. Fault indications are stored in the DECU and
are retained throughout the life of the control unit. However,
fault information prior to the previous cycle can only
be accessed with specialized test equipment. During engine
start the DECU BIT displays 88 for satisfactory test
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