B757 flight crew has erroneous GS indication at sdf.

Attributes
ACN	715129
Time
Date	200610
Local Time Of Day	0001 To 0600
Place
Locale Reference	airport : sdf.airport
State Reference	KY
Altitude	msl bound lower : 1400 msl bound upper : 2400
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : sdf.tracon
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 35r other
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : flight engineer pilot : cfi
Experience	flight time last 90 days : 30 flight time total : 6000 flight time type : 700
ASRS Report	715129
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	altitude deviation : crossing restriction not met non adherence : published procedure other spatial deviation
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : returned to assigned altitude flight crew : overcame equipment problem
Consequence	Other
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

We were cleared for visual approach to runway 35R and given a vector to the OM. GS captured slightly prior to localizer capture. We began following GS and then received a 'GS degraded' indication. I continued following flight director as I intercepted localizer. The flight director with erroneous GS information took us approximately 1000 ft low just inside the OM (1400 ft MSL-900 ft AGL as opposed to 2400-1900 ft AGL). We promptly recognized the error and leveled off until we intercepted PAPI. Contributing factor was the fact that we had both been on duty for about 15 hours. I had been awake for 18 hours.

Original NASA ASRS Text

Title: B757 FLT CREW HAS ERRONEOUS GS INDICATION AT SDF.

Narrative: WE WERE CLRED FOR VISUAL APCH TO RWY 35R AND GIVEN A VECTOR TO THE OM. GS CAPTURED SLIGHTLY PRIOR TO LOC CAPTURE. WE BEGAN FOLLOWING GS AND THEN RECEIVED A 'GS DEGRADED' INDICATION. I CONTINUED FOLLOWING FLT DIRECTOR AS I INTERCEPTED LOC. THE FLT DIRECTOR WITH ERRONEOUS GS INFO TOOK US APPROX 1000 FT LOW JUST INSIDE THE OM (1400 FT MSL-900 FT AGL AS OPPOSED TO 2400-1900 FT AGL). WE PROMPTLY RECOGNIZED THE ERROR AND LEVELED OFF UNTIL WE INTERCEPTED PAPI. CONTRIBUTING FACTOR WAS THE FACT THAT WE HAD BOTH BEEN ON DUTY FOR ABOUT 15 HRS. I HAD BEEN AWAKE FOR 18 HRS.

Data retrieved from NASA's ASRS site as of January 2009 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.