TM  55-1520-240-T CHAPTER   2 VIBRATION ANALYSIS AND DYNAMIC ABSORBER  TROUBLESHOOTING CHAPTER OVERVIEW Chapter 2 contains procedures for vibration analysis and dynamic absorber troubleshooting. Each system and failure symptom is listed below. Included in this chapter are locations and views of all electrical connectors, receptacles, relays, and ground connections involved withvibration analysis. Refer to TM 55-1520-240-23 for required maintenance procedures. SYSTEM PARA VIBRATION ANALYSIS 2-1 DYNAMIC  ABSORBER 2-2 FAILURE   SYMPTOM   LIST VIBRATION   ANALYSIS SYMPTOM TASK SYMPTOM TASK LOW  FREQUENCY  VIBRATION  ISOLATION  PROCEDURE 2-1.1 HIGH  FREQUENCY  VIBRATION    ISOlATION  PROCEDURE 2-1.1 ROTOR BLADE SHOCK ABSORBER ISOLATION PROCEDURE 2-1.1 VIBRATION FREQUENCY TOO RAPID TO COUNT,VIBRATION FELT IN STRUCTURE (6/REV) LATERAL  BALANCE  IS  1  IPS  OR  GREATER  DURING  GROUND TRACKING VIBRATION FREQUENCY IDENTIFIED AS 225 RPM (1/REV) 2-1.1 TRACKING  IS  ERRATIC  AFTER  SEVERAL  ATTEMPTS VIBRATION  FREQUENCY  IDENTIFIED  AS  675  CYCLES  PER SECOND  (3/REV) 2-1.1 BLADE CHANGES MORE THAN 1 INCH BETWEEN GROUND AND  HOVER DYNAMIC  ABSORBER SYMPTOM TASK SYMPTOM TASK CTR VIB ABSORB CIRCUIT BREAKER WILL NOT STAY CLOSED 2-2.4 LH VIB ABSORB CIRCUIT BREAKER WILL NOT STAY CLOSED 2-2.4 NO INDICATION ON TEST BOX METER WHEN TEST SWITCH IS SET TO EXTEND OR RETRACT, SWITCH AT CENTER 2-2.4 NO INDICATION ON TEST BOX METER WHEN TEST SWITCH IS SET TO EXTEND OR RETRACT, SWITCH AT LEFT 2-2.4 NO INDICATION ON TEST BOX WHEN TEST SWITCH IS SET TO EXTEND OR RETRACT, SWITCH AT RIGHT 2-2.4 RH VIB ABSORB CIRCUIT BREAKER WILL NOT STAY CLOSED 2-2.4 TEST BOX METER INDICATES ONE DIRECTION BUT NOT EX- TEND AND RETRACT WHEN TEST SWITCH IS SET TO EX- TEND AND RETRACT, SWITCH AT CENTER 2-2.4 2-1.1 2-1.7 2-1.8 2-1.9 SYMPTOM TASK TEST BOX METER INDICATES ONE DIRECTION BUT NOT EX- TEND AND RETRACT WHEN TEST SWITCH IS SET TO EX- TEND AND RETRACT, SWITCH AT LEFT 2-2.4 TEST BOX METER INDICATES ONE DIRECTION BUT NOT EX- TEND AND RETRACT WHEN TEST SWITCH IS SET TO EX- TEND AND RETRACT, SWITCH AT RIGHT 2-2.4 Change  10 2-2.1