TABLE 2-1.2.1A NORMAL VIBRATION LEVELS AT HOVER

2-1.2.1 LOW FREQUENCY VIBRATION ISOLATION PROCEDURE

TABLE 2-1.2.1B. NORMAL VIBRATION LEVELS AT 130 KNOTS

TM-55-1520-240-T-1 CH-47D Heilcopter Manual
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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 GO TO NEXT PAGE Change 5 2-4.3

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