////////////////////////A / /
CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH EIS ú

 77-12-00
 ú ú C01 Page 8 ú Nov 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
28V DCSTBY BUS24-54-00

N2%RPM N1

EGT
`C

N2
%RPM

FF/FUX1000
120 11
1102
PULL
9 3
TO 8 4
SET
75
6
N1 FUEL USEDRESET

LIMITING SHAPING

T422 N2 TACH
TRANSMITTER

ULA EPROM RAMDAC ENGINE 1 BITE RELAY
80-11-00LOW VOLTS
OVER LIMITPOWER SUPPLY 1 A
LAMP DRIVE 31-42-00MDT ENGINE 1 N2 INDICATOR CIRCUITRY
28V DC
STBY BUS
24-54-00

C1185
EIS-PRI 4

P6-2 CIRCUITBREAKER PANEL 80-11-00

31-42-00
INTERNALS
SAME AS
ENGINE 1

77-31-00
31-42-00
INTERNALS
SAME AS
ENG 1

ENGINE 2 N2 INDICATOR CIRCUITRY
ENGINE 2 N182 PRIMARY ENGINE DISPLAY (P2 CENTER INSTRUMENT PANEL)
N2 Tachometer Indication Systems Simplified SchematicFigure 4 (Sheet 2)

PULL
TO
SET
N1

////////////////////////A / /
CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
(5)  
Overlimit indication is provided by a red warning light in the indicator dial that is illuminated when the engine is operating at, or above, the red line limit.

 (6)  
A target value of N1 can be set and displayed on the indicator either automatically or manually. In the automatic mode (manual set knob, located in lower right hand corner of indicator front bezel, is depressed), target N1 is determined by the Flight Management Computer (FMC). This value is displayed on the indicator by an index marker (bug) mounted on the dial periphery and positioned with a DC motor driven by a closed loop servo. System failure results in the index marker (bug) returning to lower stop and after 5 seconds a second LED digital display illuminating a single line of bars across its horizontal centerline. The FMC can be disconnected from the indicator allowing the target value to be set manually. Manual setting of the target value is accomplished by pulling out and rotating manual set knob. Pulling out the knob disables the computer generated signal, illuminates a four-digit 7-bar LED display in the lower half of the dial face, and allows the index marker (bug) and LED display to be driven in unison by rotating the knob.

 (7)  
An internal switch in the indicator transmits a signal to the Idle Control System.

 (8)  
Actual N1 data is also transmitted to the Autothrottle System and Flight Data Recorder as a 0-5v dc output proportional to engine N1 speed. In addition, a discrete 0v dc or 28v dc is provided to indicate the validity or non-validity of the actual N1 data signal.

 (9)  
AIRPLANES WITHOUT EIS; A light sensitive cell in the dial face is used by the auto-dimmer within the indicator to control the intensity of the LED numeric displays within specified limits.

 B. N2 Indication System (Fig. 4)
 (1)  
N2 rotor speed is measured by an alternator which provides an ac signal whose frequency is proportional to the core rotor speed. The alternator incorporates dual windings with one winding providing N2 speed signal to the PMC and the other winding to the N2 tachometer indicator.

 (2)  
The N2 tachometer indicator displays actual N2% RPM and operates in similar manner as the N1 indicator with pointer indication and numeric display of data, overlimit indication, and light sensitive cell for controlling LED intensity.

 (3)  
An internal switch in the indicator transmits a signal to the engine start circuit. This signal ensures starter disengagement at the maximum starter run speed (46.33%) and prevents starter re-engagement at engine speeds (above 30.43%) which could damage the starter or engine. This switch also inhibits the PMC INOP light.

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 77-12-00
 ALL  ú ú C02 Page 9 ú Mar 12/00
　
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