(6)
Anti-ice heating element (Ref 30-34-00/001)
C.
The PT2/TT2 probe housing is made of beryllium copper. It has a scoop at the end to flow air through and around the hermetically sealed temperature sensing elements. A port, on the leading edge of the PT2/TT2 probe near the end, lets air pressure go into the pitot tube.
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7. EEC Programming Plug (Fig. 1)
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A. The EEC programming plug is connected to a receptacle at the top aft corner of the EEC. The EEC is installed to the fan case at the 1 o'clock position.
B. The EEC programming plug supplies a discrete data code to the EEC about the engines EPR/thrust relationship and selected engine rating.
C. The EEC programming plug includes a 26-contact connector and backshell. It is permanently attached to the engine by a lanyard.
D. During initial test cell operation of an engine, an EEC programming plug is made for configuration of that engine. Jumper wires are installed, in the EEC programming plug, between selected contact pairs. This supplies the EEC data to correctly control the engine. The jumper wire configuration (class number) is stamped on the backshell of the EEC programming plug and on the engine identification plate.
NOTE: The EEC programming plug must stay with the engine if the EEC is
____
replaced.
8. EEC Fuel Temperature Thermocouple Probe (Fig. 1)
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A. The thermocouple probe for the EEC fuel temperature supplies a voltage signal to the EEC to permit the EEC to control fuel and oil temperature.
B. The thermocouple probe is installed on the fuel pump which is installed on the forward face of the main gearbox at the 5 o'clock position. The thermocouple probe measures the temperature of fuel which goes into the fuel pump from the fuel/oil cooler and of the bypass fuel from the fuel metering unit.
C. The thermocouple probe for the EEC fuel temperature includes two chromel/alumel thermocouples which supply similar and independent signals, through four threaded stud terminals, to each channel of the EEC.
9. EEC Oil Temperature Thermocouple Probe (Fig. 1)
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A. The thermocouple probe for the EEC oil temperature supplies a voltage signal to the EEC to permit the EEC to control fuel and oil temperature. The signal is also used for flight compartment indication of oil temperature (AMM 79-34-00/001).
B. The thermocouple probe is installed on the forward face of the main gearbox at the 7 o'clock position. The thermocouple probe measures the temperature of scavenged oil which goes into to the oil tank through the main gearbox.
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////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
C. The thermocouple probe for the EEC oil temperature includes two chromel/alumel thermocouples which supply similar and independent signals, through four threaded stud terminals, to each channel of the EEC.
10. EEC Thermocouple Probe (TT3) (Fig. 1)
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A. The TT3 probe supplies a signal to the EEC to synthesize TT2 if the EEC finds that the actual TT2 input is invalid.
B. The TT3 probe is installed to a boss on the diffuser case at the 3 o'clock position. It extends through the diffuser case to measure total air temperature for the HPC exit.
C. The TT3 probe includes two chromel/alumel thermocouples which supply similar and independent signals, through four threaded stud terminals, to each channel of the EEC.
11. EEC Wiring Harnesses
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A. There are six EEC wiring harnesses on the engine. The EEC wiring harnesses connect the EEC to the engine sensors, probes, actuators, solenoids, and valves.
B. The EEC wiring harnesses are an open bundle construction and are line replaceable. Each wire has a shield with nickel plated copper braiding which is grounded at the connector backshells. This single-shielding supplies electromagnetic interference (EMI) and lightning protection. The connector backshells supply strain relief and anti-rotation for the wires.
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