used to troubleshoot the aircraft's tachometer
steel, and plastic. The major components of the
system. After testing the exhaust gas temperature
analyzer are the thermocouples, RPM and EGT
and engine speed systems, you may use selected
indicators, resistance and insulation check circuits,
portions of the JETCAL analyzer circuits to
and the overheat detection test circuits.
establish the proper relationship between exhaust
On the EGT system functional test and the
gas temperature and engine speed.
thermocouple and harness checks, the JETCAL
analyzer has an accuracy of 4C at the test
The JETCAL analyzer requires a power
supply of 95 to 135 volts, 50 to 400 hertz. It will
temperature. The test temperature is usually the
maximum operating temperature of the jet
operate in temperatures from 55C to +70C.
You must use a 95- to 135-volt ac power
engine. To find the maximum engine operating
supply for the TAKCAL unit check and the
temperatures, you should check the applicable
MIMs.
thermocouple check. You may perform all other
operations using emergency batteries when an
The first test you perform is a functional test
external power supply is not available. You
of the EGT system. In this test, you heat the
actuate the batteries by a push-button switch.
engine thermocouples in the tail cone of the engine
When the switch is released, the batteries are out
to test temperature. This heat comes from the
of the circuit. However, you can depress the
JETCAL heater probes through the necessary
switch when using ac without damaging the
cable connections. To measure the temperature
of the heater probes, thermocouples are embedded
batteries. To preserve the life of the emergency
batteries, use an external ac power supply
in the probes. You may read the heater probe
whenever possible.
temperature on the JETCAL potentiometer. At
The JETCAL analyzer has the following
the same time, you can read the aircraft
primary and separate functions:
thermocouple temperature on the aircraft EGT
indicator. You can then compare the readings for
accuracy.
To check the entire jet aircraft exhaust gas
temperature system for error without running
On engines that have a balancing type of
the engine or disconnecting the wiring.
thermocouple system, you must remove the
balancing thermocouple from the circuit. Then,
To check individual thermocouples before
you can check the remaining thermocouples
placing them in the aircraft.
individually or together. Check the balancing
thermocouple using a single probe. Read the
output of the balancing thermocouple on the
To check each engine thermocouple for
JETCAL potentiometer, and compare it to the
heater probe thermocouple reading.
To check the thermocouples and harness
Gas temperature is critical to engine operation;
for accuracy of output.
therefore, use the JETCAL for nozzle scheduling.
During temperature adjustments, make all
temperature readings on the JETCAL potenti-
To check the resistance of the EGT circuit,
without the EGT indicator, to assure al-
ometer. This is necessary because you must read
lowable limits.
engine temperature accurately to ensure the engine
is operating at optimum engine conditions. When
checking and adjusting the engine exhaust gas
To check the insulation of the EGT circuit
for shorts or grounds.
temperature, install a switch box in the EGT
circuit before starting the test. You will use the
switch box to switch the cockpit indicator into the
To check the EGT indicators.
circuit, or to switch the temperature indication of
To check engine thermocouples and
the engine thermocouple and harness to the
harness on the engine with the engine
JETCAL potentiometer. You can also read
removed from the aircraft.
temperature readings from the engine thermo-
couple and harness on the JETCAL analyzer by
To read engine RPM to an accuracy of
making the necessary connections.
0.1-percent engine runup.
Incorporated in the analyzer is the TAKCAL
unit (RPM indicator) check circuit. This circuit
reads engine speed with an accuracy of 0.1
To use the RPM check (TAKCAL) and
potentiometer to establish the proper rela-
percent. The TAKCAL unit check can also be
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