Erroneous GS indicator.

Attributes
ACN	299713
Time
Date	199503
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : bos
State Reference	MA
Altitude	msl bound lower : 1650 msl bound upper : 2000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : bos
Operator	common carrier : air taxi
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 135
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 5500 flight time type : 1400
ASRS Report	299713
Person 2
Affiliation	company : air taxi
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : critical other anomaly other other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

On approach to runway 4R into boston, first officer's GS indicator started descent (first officer - flying). First officer started down and I noticed my GS was not centered. We were at 2000 ft and had descended to 1650 ft. ATC advised a 'low altitude alert.' first officer climbed back up to 2000 ft. I took over the approach and continued the approach as we had already missed once due to lack of forward visibility at decision ht. Upon arrival at boston, we were advised by maintenance that this was a recurring problem with this aircraft that can't be duplicated on the ground. I do not understand how our company can allow a problem like this to occur. Also, it was 3 days into a new logbook so that we were not aware of this problem until maintenance told us about it.

Original NASA ASRS Text

Title: ERRONEOUS GS INDICATOR.

Narrative: ON APCH TO RWY 4R INTO BOSTON, FO'S GS INDICATOR STARTED DSCNT (FO - FLYING). FO STARTED DOWN AND I NOTICED MY GS WAS NOT CTRED. WE WERE AT 2000 FT AND HAD DSNDED TO 1650 FT. ATC ADVISED A 'LOW ALT ALERT.' FO CLBED BACK UP TO 2000 FT. I TOOK OVER THE APCH AND CONTINUED THE APCH AS WE HAD ALREADY MISSED ONCE DUE TO LACK OF FORWARD VISIBILITY AT DECISION HT. UPON ARR AT BOSTON, WE WERE ADVISED BY MAINT THAT THIS WAS A RECURRING PROB WITH THIS ACFT THAT CAN'T BE DUPLICATED ON THE GND. I DO NOT UNDERSTAND HOW OUR COMPANY CAN ALLOW A PROB LIKE THIS TO OCCUR. ALSO, IT WAS 3 DAYS INTO A NEW LOGBOOK SO THAT WE WERE NOT AWARE OF THIS PROB UNTIL MAINT TOLD US ABOUT IT.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.