Prior to installing engine air inlet screen, area must be
inspected for cleanliness and foreign objects.
Install engine upper screen assembly (20222-043) and lower screen assembly (20222-041) using clamp from
air inlet. Torque nut on clamp to 62-69 inch-pounds.
Plug bleed-air tube with bleed-air tube plug (20114-109). Install plug using existing coupling and sleeve.
Torque clamp to 43-47 inch-pounds.
If balance studs are used, locate the three studs that connect engine output shaft flexible coupling to input
module flange, see figure 22. Pick one stud and label it No. 1 using a black grease pencil. If balance bolts are
used, locate the three bolts, which connect engine output shaft to the flexible coupling. Pick one bolt and label
it No. 1 using a black grease pencil.
Rotate engine output shaft in freewheeling direction to next stud or bolt (whichever is applicable). Label this
stud or bolt No. 2. Repeat rotation and label last stud or bolt No. 3.
h. Rotate engine output shaft until No. 1 stud or bolt appears in center of engine support tube access hole.
Using shop towel, item 227, Appendix D of TM 1-1520-237-23, dampened with dry-cleaning solvent, item 135,
clean an area on engine output shaft at least 2 inches wide by 2 inches long, see figure 23.
Install one piece of reflective tape, 1-inch by 1-inch square, on the engine output shaft, see figure 23. Rub
tape with clean, wooden spatula, item 386, Appendix D of TM 1-1520-237-23. Do not use fingers.
Measurement failure during Engine Output Shaft
Balance can result if reflective tape is dirty. Do not use
fingers to rub reflective tape. Keep reflective tape clean.
Reflective tape is installed in a different location on each
engine output shaft. Refer to figure 23 for location of
Install optical RPM sensor (29314700) into optical RPM sensor mounting bracket (29328301). Lockwire
sensor to mounting bracket.
m. Install photocell-mounting fixture (20114-041) or (20114-044) over forward support tube, see figure 24. Locate
dowel pins of mounting bracket in support tube cutout and slide bracket to aft end of support tube cutout. Do
not torque bracket at this time. Make sure photocell bracket ear is pointing forward.
Attach High Speed Shaft (HSS) optical RPM sensor mounting bracket (29328301) to photocell mounting fixture
(20114-041 or 201114-044) using one bolt (MS35308-455), see figure 24. Torque bracket to bracket mounting
bolt to 15-16 inch-pounds.
Adjust position of photocell mounting bracket until optical RPM sensor (29314700) is centered on reflective
tape. TORQUE BOLT ON BRACKET TO 15-16 INCH-POUNDS. Make sure Optical RPM Sensor is still
centered on tape after tightening bracket.
Route 20-foot long cables through tiedown ring and in gunners/crew-chief's window. Secure cables with
tiedown straps, item 359, Appendix D of TM 1-1520-237-23.