TASK 2-1.3.
TASK 2-1.4.
TASK 2-1.5.
TM 55-1520-240-T
2-1.2.1 LOW FREQUENCY VIBRATION ISOLATION PROCEDURE (Continued)
2-1.2.1
1. INTALL TWO 1-INCH STEEL BLOCKS, ONE AT STA 95 AND ONE AT
2. ATTACH MAGNETIC BASE FROM VIBREX ACCESSORY SET TO VIB
3. DISCONNECT VIBREX SWITCH BOX LEAD FROM VIBREX RECEPTACLE
A.
4. CONNECT VIB PICKUP CABLE TO VIBREX RECEPTACLE A.
5. HAVE PILOT ESTABLISH STABLE HOVER AT 100% N2.
6. PLACE VIB PICKUP ON BLOCK AT STA 95 IN VERTICAL POSITION.
7. SLOWLY TUNE VIBREX OVER THE RANGE FROM 225 RPM (1 /REV) TO
1350 RPM (6/REV). RECORD FREQUENCY AND MAGNITUDE. (THE
MODEL 192 SPECTRUM ANALYZER MAY BE USED HERE INSTEAD OF
VIBREX UNIT TO OBTAIN A RECORD OF ALL FREQUENCIES PRESENT.)
8. PLACE VIB PICKUP ON BLOCK AT STA 95 IN LATERAL POSITION. RE-
PEAT STEP 7.
9 PLACE VIB PICKUP ON BLOCK AT STA 482 IN VERTICAL POSITION.
REPEAT STEP 7.
10. PLACE VIB PICKUP ON BLOCK AT STA 482 IN LATERAL POSITION. RE-
PEAT STEP 7.
11. LAND HELlCOPTER AND ANALYZE RECORDED VIBRATIONS.
WERE ANY RECORDED VIBRA-
TION LEVELS AT 225 RPM
(1 /REV) ABOVE TABLE 2-
1.2.1 A VIBRATION LEVELS?
WERE ANY RECORDED VIBRA-
TION LEVELS AT 675 CYCLES
PER MINUTE (3/REV) ABOVE
TABLE 2-1.2.1 A VIBRATION
LEVELS?
WERE ANY RECORDED VIBRA-
TION LEVELS AT 1350 CYCLES
PER MINUTE (6/REV) ABOVE
TABLE 2-1.2.1A VIBRATION
LEVELS?
TABLE 2-1.2.1A NORMAL VIBRATION
LEVELS AT HOVER
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Change 5
2-4.3
