Cftt. GS indicator malfunction.

Attributes
ACN	295131
Time
Date	199501
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : hts
State Reference	WV
Altitude	msl bound lower : 1400 msl bound upper : 3000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : hts artcc : vtbb
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 135
Flight Phase	descent : approach
Route In Use	arrival other enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : commercial pilot : cfi
Experience	flight time last 90 days : 280 flight time total : 7900 flight time type : 280
ASRS Report	295131
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : less severe non adherence : clearance other spatial deviation
Independent Detector	other controllera other flight crewa
Resolutory Action	controller : issued new clearance other other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While being vectored for the ILS to runway 30 at hts, I noticed that the GS indicator showed that we were above the GS, which corresponded with our vectoring altitude of 3000 ft MSL. Approach cleared us for the approach and we descended to 2600 ft MSL as instructed and it still indicated that we were above the GS. Once established we could descend to 2100 ft MSL. Once we became established on the localizer, we were still showing 1/2 DOT above the GS. I assumed that we had received a bad vector from ATC, and began to descend to catch the GS, but was not aware of the altitude/rate of descent. The ground proximity warning started going off and I couldn't figure out why, because I was still indicating above the GS. We get a lot of false warnings, so I assumed this was another one, until I looked at the rate of descent, and realized that the GS indicator needle had stuck in position showing us 1/2 DOT high and I was below the GS. I immediately initiated a go around and climbed. Meanwhile ATC had noticed the deviation from the GS and was receiving a low altitude alert and called for us to climb immediately. What the first officer was doing, I do not know. I know that he was extremely tired from being on duty 6 straight days (reserve first officer). He said that he had received the same indication on his GS indicator, but it worked perfectly on the next ILS approach. If it had not been for the GPWS and ATC, we would have had a CFIT instead of a cftt.

Original NASA ASRS Text

Title: CFTT. GS INDICATOR MALFUNCTION.

Narrative: WHILE BEING VECTORED FOR THE ILS TO RWY 30 AT HTS, I NOTICED THAT THE GS INDICATOR SHOWED THAT WE WERE ABOVE THE GS, WHICH CORRESPONDED WITH OUR VECTORING ALT OF 3000 FT MSL. APCH CLRED US FOR THE APCH AND WE DSNDED TO 2600 FT MSL AS INSTRUCTED AND IT STILL INDICATED THAT WE WERE ABOVE THE GS. ONCE ESTABLISHED WE COULD DSND TO 2100 FT MSL. ONCE WE BECAME ESTABLISHED ON THE LOC, WE WERE STILL SHOWING 1/2 DOT ABOVE THE GS. I ASSUMED THAT WE HAD RECEIVED A BAD VECTOR FROM ATC, AND BEGAN TO DSND TO CATCH THE GS, BUT WAS NOT AWARE OF THE ALT/RATE OF DSCNT. THE GND PROX WARNING STARTED GOING OFF AND I COULDN'T FIGURE OUT WHY, BECAUSE I WAS STILL INDICATING ABOVE THE GS. WE GET A LOT OF FALSE WARNINGS, SO I ASSUMED THIS WAS ANOTHER ONE, UNTIL I LOOKED AT THE RATE OF DSCNT, AND REALIZED THAT THE GS INDICATOR NEEDLE HAD STUCK IN POS SHOWING US 1/2 DOT HIGH AND I WAS BELOW THE GS. I IMMEDIATELY INITIATED A GAR AND CLBED. MEANWHILE ATC HAD NOTICED THE DEV FROM THE GS AND WAS RECEIVING A LOW ALT ALERT AND CALLED FOR US TO CLB IMMEDIATELY. WHAT THE FO WAS DOING, I DO NOT KNOW. I KNOW THAT HE WAS EXTREMELY TIRED FROM BEING ON DUTY 6 STRAIGHT DAYS (RESERVE FO). HE SAID THAT HE HAD RECEIVED THE SAME INDICATION ON HIS GS INDICATOR, BUT IT WORKED PERFECTLY ON THE NEXT ILS APCH. IF IT HAD NOT BEEN FOR THE GPWS AND ATC, WE WOULD HAVE HAD A CFIT INSTEAD OF A CFTT.

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.