TM 55-4920-244-14
cater must show a temperature rise as each en-
has cooled to ambient temperature, make another
gine thermocouple is checked.
test. If there is a transposition, the difference in
h. Place switch SW- 6in MECH. ZERO
the readings will probably be large because of
position.
the thermals that were present in the first test.
c. Disconnect and check each terminal
with a magnet. Chromel (+) is nonmagnetic;
alumel (-) is magnetic.
An odd number of crossed lead wires (1,
3, etc ) can be easily detected, since the aircraft
minal. A temperature rise or fall on the aircraft
EGT indicator will read backwards upon applica-
EGT indicator indicates a transposition when the
tion of heat to the engine thermocouples. An
crossed terminal is touched.
even number of crossed lead wires (2, 4, etc),
while much more difficult to detect, can be found
by several methods:
a. Place switch SW-1 in OFF position.
a. The simplest method is with an ohm-
b. Place TEMP. REGULATOR knob in
meter. Chromel wire has approximately two and
OFF position.
one-half times the resistance of alumel wire. To
c. Remove heater probes from engine
have a transposition, the chromel wire would
thermocouples and disconnect from outlets of
have to be connected to the alumel wire. The
junction box.
resistance reading would be different than the
2-1/2 to 1 ratio.
NOTE
If continuity check probe
b. Where possible, make a normal engine
is connected, remove in
thermocouple test with tester connected to a hot
accordance with c above.
engine (shortly after being run). When engine
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