HIGH FREQUENCY VIBRATION ISOLATION PROCEDURE (Continued)

2-1.2.2 HIGH FREQUENCY VIBRATION ISOLATION PROCEDURE

2-1.3 VIBRATION FREQUENCY IDENTIFIED AS 225 RPM (1 /REV)

TM-55-1520-240-T-1 CH-47D Heilcopter Manual
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TM 55-1520-240-T 2-1.2.2 HIGH FREQUENCY VIBRATION ISOLATION PROCEDURE (Continued) 2-1.2.2 NOTE AT THE PRESENT TIME, NO COMPREHENSIVE VIBRATION DATA OR VALID DIAGNOSTIC CRITERIA EXISTS FOR THE VARIOUS CH-47D MECHANICAL DRIVE COMPONENTS AND SYSTEMS. HOWEVER, SOURCES OF UNUSUALLY HIGH Vl- BRATION CAN BE LOCATED USING THE CHADWICK HEL- MUTH MODEL 192 SPECTRUM ANALYZER WITH ITS HAND HELD VIBRATION PROBE. ONCE THE SOURCE OF THE ABNORMAL VIBRATION IS FOUND, THE REPAIR, RE- MOVAL, AND REPLACEMENT OF COMPONENTS SHOULD BE DETERMINED BY QUALIFIED FIELD PERSONNEL. KNOWN IS APPROXIMATE LOCATION OF VIBRATION SOURCE INSTALL STEEL BLOCKS AT STA 95 AND 482. CONNECT VIB PICKUP LEAD TO INPUT A OF SPECTRUM ANALYZER. US- ING SPECTRUM ANALYZER AND VIB PICKUP, LOCATE GEN- ERAL AREA OF VIBRATION SOURCE BY STARTING AT STEEL BLOCK AT STA 95 AND WORKING TOWARD THE REAR OF THE A/C CHECKING FOR HIGH FREQUENCY VIBRATION ON A/C CEILING AT EACH BULKHEAD UNTIL THE APPROX- IMATE AREA OF HIGH FRE- QUENCY VIBRATION IS FOUND. PROBE AREA OF HIGH VIBRATION WITH VIB PICKUP UNTIL MAXIMUM AM- PLITUDE OF VIBRATION IS OBTAINED. REFER TO TABLE 2-1.2.2 TO IDENTIFY POSSIBLE SOURCE OF HIGH FREQUENCY VIBRATION. CAN SOURCE OF VIBRATION BE IDENTIFlED BY USING TABLE 2- RECHECK ALL SYNC SHAFT MOUNTING AND COUPLING BOLTS; ENG DRIVE SHAFT COUPLING BOLTS; FORWARD, AFT, COMBINING, AND ENGINE TRANSMISSION MOUNTING BOLTS FOR PROPER TORQUE 1 . 2 . 2? AND/OR WEAR TABLE 2-1.2.2. CH-47D EXCITING FREQUENCIES A T 225 RPM (100% N2) END OF TASK Change 5 2-4.7

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