Learjet 60 - Engine Diagnostic System; Engine Diagnostic Unit; ITT Indicators

Learjet 60

Pilot's Manual
ITT INDICATORS
An
ITT
indicator for each engine is installed on the center instrument
panel . Each indicator utilizes both a three-place digital display and a
circular scale with pointer to indicate
ITT
. The scale is marked from
0°C to 1000°C in 50°C increments . The digital display uses lighted
segments to show the turbine temperature to the nearest degree . In-
terstage turbine temperature for each engine is sensed by Chromel-
Alumel parallel wired thermocouples positioned between the high-
and low-pressure turbine sections at engine station
4
.5 . The thermo-
couples provide an average
T4
.5 signal to the
FADEC
. The
ITT
indica-
tor is driven by a signal from the
FADEC
. When electrical power is
not available to the instrument, the pointer will go to the lowest pos-
sible position and the digital display will be blank . Upon initial pow-
er-up, the indicator will conduct a self test . During the self test, the
digital display segments will illuminate and indicate "888" . Failure of
the self test is indicated by three dashes in the digital display and no
pointer movement . Electrical power for the indicators is 28 VDC sup-
plied through the 2-amp
L
and
R ITT
circuit breakers on the pilot's
and copilot's circuit breaker panels respectively . The
ITT
indicators
are operative during
EMER
BUS mode . Refer to Airplane Flight Man-
ual for instrument limit markings .
ENGINE DIAGNOSTIC SYSTEM
An Engine Diagnostic System (EDS) is installed to provide engine fault
recording and trend monitoring . The system periodically records en-
gine parameters and allows the crew to request that conditions be re-
corded at anytime . Normal use of the system entails downloading data
from the
EDS
and submitting to Pratt and Whitney Canada for analysis
on amonthly basis . The data may be downloaded at any time to assist
in diagnosing engine problems which may be encountered . The
EDS
is
intended for maintenance functions only and not for in-flight monitor-
ing or diagnosis by the flight crew . The system consists of an Engine
Di-
agnostic Unit (EDU), two isolation units (one for each engine), a
Control Display Unit (CDU), a white
EDSFAULT
annunciator and an
EDS RECORD
switch on the center switch panel . The system is pow-
ered by 28 VDC through the 5-ampere ENGINE DIAGNOSTIC SYS-
TEM
circuit breaker on the copilot's circuit breaker panel .
ENGINE DIAGNOSTIC UNIT
The Engine Diagnostic Unit (EDU) contains the memory used to store
the collected data for each engine . The unit's capacity allows approxi-
mately 200 hours of data storage . The unit is installed in the tailcone .
On the back of the
EDU
is a green, an amber, and a red light . The green
light illuminates to indicate the
EDS
is powered . The red light
illuminates to indicate the
EDS
has failed the self test .
PM-123
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