Engine Tachometer System Schematic  502 
77-12-0  Figure 2  Jan 20/82 
Page 4 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

ENGINE TACHOMETER SYSTEM - TROUBLE SHOOTING ENGINE TACHOMETER SYSTEM -ADJUSTMENT/TEST

502 
May 15/69  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  77-12-0 Page 101 

1.  Engine Tachometer System Test
A.  General
(1)  The engine tachometer system is tested with the engines shut down. N1 and N2 tachometer generators are disconnected and a standard test generator is connected in their place. The test consists of driving a standard test generator at predetermined speeds while obtaining readings on N1 and N2 tachometer indicators.
B.  Equipment and Materials
(1)  
Tachometer tester CA-11-FS

(2)  
Electrical motor for driving test generator at specified speeds.

(3)  
Adapter harness F80228-15, adapter cable provided from G77001-4 test box, or manufacture locally for CA-11-FS (Fig. 501).

C.  Test Engine Tachometer System
(1)  
Obtain access to N1 tachometer generator by removing engine nose dome, and N2 tachometer generator by opening right engine cowl panel. Refer to Chapter 71, Power Plant.

(2)  
Disconnect N1 and N2 tachometer generators and connect standard test generator in their place using adapter harness. Connect adapter harness grounding lug to one tachometer generator-mounting stud (Fig. 501).

(3)  
With standard test generator set to values listed in Table I, both indicators (N1 and N2) on pilots’ engine instrument panel shall read the following percentage rpm within tolerances noted.

500 
May 01/98  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  77-12-0 Page 501 

CA-11FS rpm  Indicator % rpm  Tolerances % RPM 
0  0  ±0.50 
840  20  ±0.50 
2520  60  ±0.50 
4200  100  ±0.50 

NOTE:  Tap indicators lightly before reading. Cover glass on each indicator must be tight and free of cracks. Indicator pointers must operate smoothly over scale.
(4)  
Disconnect test generator adapter harness and reconnect N1 and N2 tachometer generators.

(5)  
Install engine nose dome and close right engine cowl panel.

Adapter Harness and Test Connections  500 
77-12-0  Figure 501  May 01/98 
Page 502 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

ENGINE TACHOMETER GENERATOR - REMOVAL/INSTALLATION
1. Remove Engine Tachometer Generator
A.  Obtain access to N1 tachometer generator by removing engine nose dome (Ref 71-11-51/401).
B.  Obtain access to N2 tachometer generator by opening right cowl panel (Ref 71-11-11/401).
C.  Cut lockwire and disconnect electrical connector from tachometer generator (Fig. 401).
D.  Remove attaching nuts and washers fastening tachometer generator to drive.
E.  For N1 tachometer generator, remove ground wire terminal from generator mounting stud.
F.  For N1 tachometer generator, remove nose dome interference bracket, if installed.
G.  Remove generator (bearing type) or stator (bearingless type) from studs and discard old gasket.
H.  If generator is the bearingless type proceed as follows:
NOTE: In the following step, remember that it is a left-hand thread. Turn CW to loosen.
(1)  
Loosen rotor assembly using a 9/16 inch, hex, box wrench, approximately 3 turns clockwise.

(2)  
Lightly tap the end of the rotor assembly with a brass or plastic hammer to release the tapered threaded shaft.

(3)  
Remove rotor assembly by hand.

NOTE: 1)  If rotor assembly cannot be removed by hand, repeat steps (1) and (2) until it can be removed.
2)  If a tool is necessary to remove the rotor assembly, grip only on the large diameter of the collar. Pulling on the rotor will tend to tighten the assembly.
2.  Install Engine Tachometer Generator
A.  Equipment and Materials
(1)  Grease - MIL-G-81322 (Ref 20-30-21/201)
B.  Lightly hand coat splines of tachometer generator drive shaft with grease.
C.  If generator is the bearing less type proceed as follows (Fig. 402):
CAUTION:  DO NOT REASSEMBLE COLLAR TO ROTOR BEFORE CLEANING AND LUBRICATING. WITHOUT LUBRICATION THE ROTOR HUB DIAMETER AND ITS MATING COLLAR COUNTERBORE MAY TEND TO SEIZE. AN ATTEMPT TO SEPARATE MAY CAUSE GALLING OR SCORES.
　
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