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It is also through the CAN system that the FADEC transmits information to two related instruments,
the CED 125 and the AED 125. The indications on these instruments occur through light emitting
diodes whose intensity may be adjusted by an adjacent additional rheostat.
a)
CED
stands for Compact Engine Display. It integrates all engine data which are to be
monitored during flight, namely the RPM, both in digits and range, the oil pressure(OP), the
oil temperature (OT), the coolant temperature (CT) and the gearbox temperature (GT), all in
range only, and finally the % of load both in digits and in range.
Range indication are colour coded green, amber and red. Any time a reading is in the amber
or red range, the “Engine Caution” warning light illuminates on the FADEC’s central warning
system and extinguishes only when the adjacent “CED Test/Ack” pushbutton is depressed
(see below).
b)
AED
stands for Auxiliary Engine Display. It displays the fuel temperature, the fuel tanks
contents and voltage.
FADEC’s central warning system
[HOP2]
The FADEC’s central warning system comprises a red “Engine Caution” annunciator and a common
“test/ack” pushbutton which can be used either for testing both instruments or to extinguish the light
if it is caused by a yellow or red warning showing on the CED.
A separate “GLOW” annunciator is located close to the Starter Key.
In addition, the central warning system includes two red warning lights, one for FADEC A and one for
FADEC B. Assuming that FADEC A, the active one, fails, its associated red warning light will flash, and
the system will normally switch over automatically to FADEC B. Should this not be the case, as made
evident by the engine’s abnormal behaviour, the switching from FADEC A to FADEC B can be done
manually by pulling the “Auto FADEC – Pull to Force B” breaker, adjacent to engine master switch.
Assuming that both these lights should flash simultaneously, this may be indicative that a fuel tank is
running dry (see fuel system above).
Assuming however that, although the fuel level status is satisfactory, both FADEC red warning lights
are flashing, according to the “Supplement”, this situation does not necessarily lead to an engine
failure but, even if the engine continues to run, the load display may not correspond to the current
value, and a total engine failure might be expected at any moment anyway.
The engine master switch, engine starting system
As mentioned earlier, because of its basic operating principle, no ignition system is required for diesel
engines. However, some engines are difficult to start when they are cold because the temperature of
the induction air at the end of the compression stroke is still too low to produce spontaneous ignition
and combustion. It is only once the engine is running that sufficient heat is produced to sustain
combustion.
This is particularly the case with IDI which requires induction air preheat assistance. This is achieved
by electrically heated glow plugs, one located in the combustion chamber of each cylinder, and which
momentarily produce a temperature close to 1000°C.
Although DI engines are less prone to starting problems, the TAE 125-1 is fitted with a similar glow
plug system to improve the starting behaviour when the engine is cold, particularly in combination
with low outside air temperatures. On the TAE 125-1, the glow plugs are FADEC-controlled, as are the
Versie oktober 07
