FLT CREW OF B737-400 ENCOUNTER VIBRATION IN THEIR HGS AT ENG THRUST SETTINGS CONSISTENT WITH THOSE USED DURING APCHS.

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I FLEW A FLT TO TPA. DURING THE INITIAL DSCNT INTO TPA; I FOUND THAT THE SYMBOLOGY IN THE HGS 4000 WAS IN CONSTANT MOTION AT N1 PWR SETTINGS OF 55%-62%. I SPOKE WITH TPA MAINT AND WAS TOLD THAT THE SYS CHKED OUT FINE. DURING TKOF AND CLB TO OUR NEXT CITY; THE HGS OPERATED NORMALLY. DURING THE DSCNT WITH N1 SET BTWN 55%-62%; THE ACFT VIBRATED A LITTLE MORE THAN AT THE OTHER PWR SETTINGS. THIS VIBRATION WAS MAGNIFIED IN THE HGS. THIS VIBRATION MADE IT SOMEWHAT DIFFICULT TO READ ALL THE INFO IN THE COMBINER. IF YOU PLACED YOUR FINGER ON THE MOUNTING FRAME; YOU COULD FEEL JUST A HINT OF VIBRATION. AS YOU MOVED YOUR FINGER DOWN THE MOUNTAIN ARM; TO THE BOTTOM OF THE COMBINER GLASS; THE VIBRATION CAME MORE PRONOUNCED. WITH THE ACFT CONFIGURED WITH GEAR DOWN AND FLAPS 30 DEGS; THE N1 WAS IN THIS PWR SETTING MOST OF THE APCH. THE FO AGREED THAT THE COMBINER WAS VIBRATING A GREAT DEAL MORE THAN THE ACFT WHEN HE TOUCHED THE COMBINER GLASS. I SPOKE WITH MAINT ABOUT THIS ISSUE AND THEY SAID THEY WOULD LOOK AT IT; I BELIEVE; AT OUR MAINT BASE. THE PLANE NEEDED TO HAVE ITS APU MEL REPAIRED. I ALSO PASSED ALONG WHAT I HAD SEEN TO THE NEW CAPT. HE SAID HE WOULD LOOK FOR IT AND PASS THE INFO ALONG TO MAINT. ON A DIFFERENT FLT TO TPA; ON A DIFFERENT ACFT; I ENCOUNTERED THE SAME THING WITH THE HGS. I HAVE NEVER NOTICED THIS BEFORE ON ANY OTHER ACFT WITH THE HGS4000 OR THE STANDARD HGS. BECAUSE I ONLY HAD THE PROB INFLT AND AT THE SPECIFIED PWR SETTINGS; I AM NOT SURE HOW MAINT CAN DUPLICATE THE PROB. MYSELF; I WOULD NOT HAVE WANTED TO FLY A CAT III APCH TO MINIMUMS WITH THE HGS SYMBOLS MOVING AROUND SO MUCH. I JUST WANTED TO PASS ALONG WHAT I HAD SEEN; SO SAFETY CAN INVESTIGATE IF THIS IS A POSSIBLE PROB WITH THE HGS 4000.