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
