Air carrier descent below GS while on coupled approach for autoland.

Attributes
ACN	326159
Time
Date	199601
Place
Locale Reference	atc facility : iad
State Reference	VA
Altitude	agl bound lower : 200 agl bound upper : 200
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	tower : iad
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent : approach landing other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 20000 flight time type : 2000
ASRS Report	326159
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	inflight encounter : weather other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	other

Narrative:

ATIS gave visibility at 1 mi at iad, overheard RVR 3000 ft on runway 12. We were cleared for approach runway 1R. Elected to perform autoland due to fog and light snow. After passing alert ht with everything indicating normal I looked outside and saw the approach lights. It took a few seconds but I realized we were headed for the approach lights. I disconnected the autoplt, flew it back to the GS and made a normal landing. I then realized the 'too low, GS' aural had sounded and missed approach was warranted but my entire focus was on not landing in the approach lights and did not realize what the noise was about until after landing. The mystery is why the approach was so low in so short of time when everything looked good.

Original NASA ASRS Text

Title: ACR DSCNT BELOW GS WHILE ON COUPLED APCH FOR AUTOLAND.

Narrative: ATIS GAVE VISIBILITY AT 1 MI AT IAD, OVERHEARD RVR 3000 FT ON RWY 12. WE WERE CLRED FOR APCH RWY 1R. ELECTED TO PERFORM AUTOLAND DUE TO FOG AND LIGHT SNOW. AFTER PASSING ALERT HT WITH EVERYTHING INDICATING NORMAL I LOOKED OUTSIDE AND SAW THE APCH LIGHTS. IT TOOK A FEW SECONDS BUT I REALIZED WE WERE HEADED FOR THE APCH LIGHTS. I DISCONNECTED THE AUTOPLT, FLEW IT BACK TO THE GS AND MADE A NORMAL LNDG. I THEN REALIZED THE 'TOO LOW, GS' AURAL HAD SOUNDED AND MISSED APCH WAS WARRANTED BUT MY ENTIRE FOCUS WAS ON NOT LNDG IN THE APCH LIGHTS AND DID NOT REALIZE WHAT THE NOISE WAS ABOUT UNTIL AFTER LNDG. THE MYSTERY IS WHY THE APCH WAS SO LOW IN SO SHORT OF TIME WHEN EVERYTHING LOOKED GOOD.

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.