AN AVRO RJ85 REJECTED TKOF DUE TO #4 ENG VIBRATION CAUTION LIGHT. THE MAINT CTLR AFTER STARTING AND IDLING ENG DEFERRED THE #4 VIBRATION SYS PER THE MEL.

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ON JUL/SUN/06 A PLT CALLED AND RPTED THAT ON TKOF THE CWP (COCKPIT WARNING PANEL) ENG VIBRATION CAUTION LIGHT MOMENTARILY CAME ON AND THE #4 ENG VIBRATION INDICATOR SHOWED 1.9 BEFORE RETURNING TO NORMAL. HE INDICATED THAT ALL OTHER PARAMETERS WERE NORMAL AND THAT NO VIBRATION WAS DETECTED. NO DISCREPANCIES PERTAINING TO THE POSTFLT OR PREFLT INSPECTIONS WERE DISCLOSED. IN ORDER TO OBTAIN A BETTER UNDERSTANDING OF THE SITUATION; I ASKED THE PLT A NUMBER OF FOLLOW-UP QUESTIONS INCLUDING: ON TKOF DOES THE CREW KEEP THEIR HANDS ON THE PWR LEVERS? THE PLT INDICATED THAT THEIR HANDS WERE ON THE LEVERS AND THAT NO VIBRATIONS WERE NOTED. I ALSO ASKED IF THERE WERE ANY VIBRATIONS NOTED THROUGH THE YOKE; SEATS AND AIRFRAME. AGAIN THE PLT RESPONDED THAT NO VIBRATIONS WERE FELT. I THEN PROCEEDED TO ASK ABOUT THE ENG PARAMETERS AND AGAIN THE PLT STATED THAT ALL PARAMETERS WERE NORMAL. THE CALL WAS CONCLUDED WITH MY OBTAINING THE PLT PHONE NUMBER SO I COULD CALL HIM BACK AFTER REVIEWING THE SITUATION WITH MY SUPVR. I NOTIFIED MY MGR; THE MAINT CTL SHIFT MGR ON DUTY AT THE TIME OF THE INCIDENT; OF THE ABORTED TKOF. I REITERATED THE INFO THAT THE PLT HAD PROVIDED AND WE DISCUSSED THE SITUATION. MY MGR THEN MENTIONS MEL 77-30-1(B). I INDICATED THAT I HAD REVIEWED THE MEL. MY MGR THEN DECIDED TO HAVE A CONFERENCE CALL WITH A MECH AND RUN QUALIFIED ON THE RJ85. I ALSO ASKED ANOTHER MAINT CTLR ON DUTY AT THE TIME TO PARTICIPATE IN THE CALL. DURING THIS CONFERENCE CALL; MY MGR ASKED THE MECH TO DISCLOSE HIS THOUGHT ON WHAT MAY HAVE OCCURRED. THE MECH INDICATED THAT IN HIS EXPERIENCE; IF THE CREW HAD AN ACTUAL VIBRATION OF 1.9 THERE WOULD BE MORE OF A VIBRATION THAN WHAT THE PLT HAD EXPERIENCED. THE MECH RECOMMENDED THAT THE CREW START AND IDLE THE ENG AT THE GATE TO FURTHER ASSESS THE SITUATION. AFTER THE CONFERENCE CALL; MY MGR; ANOTHER CTLR AND I AGREED TO HAVE THE CREW START AND IDLE THE ENG AT THE GATE AND IF NO FURTHER DISCREPANCIES WERE NOTED; WE WOULD PROCEED WITH MEL 77-30-1. I THEN CALLED THE PLT BACK AND HAD HIM START AND IDLE THE ENG. I ASKED HIM TO PAY PARTICULAR ATTN TO THE START AND IDLE PARAMETERS AND TO CALL ME BACK WITH THE RESULTS. AFTER THE ENG HAD BEEN STARTED AND IDLED; THE PLT CALLED BACK AND RPTED THAT THE ENG HAD STARTED AND IDLED NORMALLY AND THAT NO VIBRATIONS WERE NOTED. BASED ON THE INFO ORIGINALLY OBTAINED; DISCUSSIONS WITH MY SUPVR AND CO-WORKERS AND REVIEWING MEL 77-30-1; IT WAS DETERMINED THAT THE DEFERRAL WAS APPROPRIATE AND THAT THE DISCREPANCY WAS AN ANOMALY. A SECOND TKOF TOOK PLACE AT APPROX XA45 WITH AN INFLT SHUTDOWN OCCURRING AT APPROX XB11. WHILE I WAS ON DUTY WHEN THESE EVENTS TOOK PLACE; I WAS NOT NOTIFIED OR INVOLVED IN THE SUBSEQUENT EVENTS. WHILE THE ABOVE INFO PROVIDES A SUMMARY OF THE EVENTS; I WOULD ALSO LIKE TO OFFER THE FOLLOWING INFO FOR CONSIDERATION IN THIS MATTER: MEL 77-30-1; WHICH HAS BEEN APPROVED BY THE FAA; WAS FOLLOWED WITHOUT EXCEPTION. NO SPECIFIC MAINT PROCS OR OPERATING PROCS ARE REQUIRED AS PART OF THE MEL. CONSULTING WITH MY MGR; BRINGING IN TECHNICAL ASSISTANCE AND HAVING THE ENG STARTED AND IDLED IN ORDER TO TEST THE SYS WAS ABOVE AND BEYOND THE REQUIRED MEL PROCS.