(f)
Power trim
(2)
Design features of the MEC include (Fig. 1):
(a)
Power Lever Shaft Rotation Travel Arc of 130 degrees (75 degrees Forward Thrust, and 45 degrees Reverse Thrust)
(b)
Fuel Shutoff Shaft Rotation travel arc of 45 degrees
(c)
Drive Shaft Rotation is counterclockwise viewed looking forward.
(d)
Drive Shaft Speed is 6111 rpm at 100 percent N2 rotor speed.
(e)
VSV Feedback Cable retracts toward the MEC at the open VSV (rig) position.
(f)
VBV Feedback Cable moves toward the MEC at the closed VBV (rig) position.
3. Power Management Control (Fig. 2)________________________
A. The power management control (PMC) provides an electronic adjustment to
the MEC. The PMC provides scheduled corrected fan (N1) speed within
preset limits.
B. The PMC is an analog electronic supervisory control system with limited
authority. Primarily, it integrates inputs of N1 fan speed, fan inlet
temperature and pressure, and power lever angle, and provides signals to
the main engine control (MEC) to modify N1 fan speed for better control
of thrust settings.
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CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
SEEA
PS12 CONNECTION
T12 TEMPERATURE SENSOR
POWER MANAGEMENT CONTROL (PMC)
J2 J4
FWD J3 J5
OIL
TANK
A
Power Management Control Location Figure 2
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CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
C. The PMC, mounted on outer surface of the fan inlet case at approximately the 3 o'clock position, provides electronic adjustment commands to the MEC to provide a scheduled corrected N1 fan speed within the limited authority range of the PMC. This control is a solid-state electronic device that is powered by the N2 control alternator speed sensor. The PMC receives information and transmits commands through connectors PS12, J2, J3, J4 and J5. The PMC performs the following specific functions:
(1)
Controls N1 fan speed within limited authority range by energizing the MEC torque motor. This action is equivalent to an internal adjustment of the MEC power lever input.
(2)
Computes and schedules corrected N1 fan speed to the percent of maximum corrected fan speed selected by the flight compartment thrust lever. A power lever position transmitter on the MEC provides the necessary electrical input.
(3)
Computes and schedules the corrected fan speed required to maintain a flat-rated N1 fan speed. A separate T12 temperature sensor provides the necessary electrical input.
(4)
Computes and schedules the corrected N1 fan speed required to maintain a calculated maximum gas temperature above the flat-rated inlet temperature.
(5)
Computes and schedules the corrected N1 fan speed required to maintain the design level of altitude compensation. Manifolded PS12 pressures are provided to the PMC, which contains a pressure transducer for the necessary electrical signal representing the PS12 level.
(6)
Provides a contact closure that automatically senses an MEC or external sensor failure. The contact closure will stay closed until the fault is cleared or the PMC is turned off.
D. A combination PMC ON/OFF switch and PMC inoperative warning light is provided on the pilots' aft overhead instrument panel for each engine. In the event of a PMC failure, the PMC will deactivate itself and the appropriate INOP warning light will illuminate. The PMC ON/OFF switch may be used to deactivate the PMC manually.
4. Compressor Inlet Temperature Sensor (Fig. 3)
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