Narrative:

Standard ILS approach. Captain flying. Given standard heading to intercept localizer. Cleared from 4000 ft to 3000 ft maintain 3000 ft until established cleared for the ILS 28L approach. Captain intercepted localizer, but did not stop at 3000 ft to intercept GS. My radio was on VOR to give DME information. Told to contact tower at the marker and maintain 170 KTS until marker. That's why I stayed on VOR (mmj). I called joining on ILS frequency (also identification on localizer frequency), at about 7.5 DME, contacted tower and called 1000 ft above ground (standard company call, ILS). I was busy. At 2000 ft GPWS went off. I looked at my raw data and exclaimed 'where's the GS'. Then I checked to see that both radios matched proper ILS 28 frequency. Radios set correctly. I again exclaimed where's the GS. Captain stayed at 2000 ft. We had visual ground contact. Tower asked our altitude and I responded 2000 ft. I asked if GS was working per captain's request. Then we intercepted GS from below at 2000 ft and landed normally. I do not know why the captain descended below 3000 ft as instructed without intercepting the GS. The captain was a check airman and instructor. He trained me to be first officer on the airplane we were flying last 5/91. I was so confident he would do an ILS correctly. I must learn never to assume the captain is infallible.

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Original NASA ASRS Text

Title: ACR HAS GPSW ACTIVATE AS THEY DSND BELOW GS AND ASSIGNED ALT.

Narrative: STANDARD ILS APCH. CAPT FLYING. GIVEN STANDARD HDG TO INTERCEPT LOC. CLRED FROM 4000 FT TO 3000 FT MAINTAIN 3000 FT UNTIL ESTABLISHED CLRED FOR THE ILS 28L APCH. CAPT INTERCEPTED LOC, BUT DID NOT STOP AT 3000 FT TO INTERCEPT GS. MY RADIO WAS ON VOR TO GIVE DME INFO. TOLD TO CONTACT TWR AT THE MARKER AND MAINTAIN 170 KTS UNTIL MARKER. THAT'S WHY I STAYED ON VOR (MMJ). I CALLED JOINING ON ILS FREQ (ALSO ID ON LOC FREQ), AT ABOUT 7.5 DME, CONTACTED TWR AND CALLED 1000 FT ABOVE GND (STANDARD COMPANY CALL, ILS). I WAS BUSY. AT 2000 FT GPWS WENT OFF. I LOOKED AT MY RAW DATA AND EXCLAIMED 'WHERE'S THE GS'. THEN I CHKED TO SEE THAT BOTH RADIOS MATCHED PROPER ILS 28 FREQ. RADIOS SET CORRECTLY. I AGAIN EXCLAIMED WHERE'S THE GS. CAPT STAYED AT 2000 FT. WE HAD VISUAL GND CONTACT. TWR ASKED OUR ALT AND I RESPONDED 2000 FT. I ASKED IF GS WAS WORKING PER CAPT'S REQUEST. THEN WE INTERCEPTED GS FROM BELOW AT 2000 FT AND LANDED NORMALLY. I DO NOT KNOW WHY THE CAPT DSNDED BELOW 3000 FT AS INSTRUCTED WITHOUT INTERCEPTING THE GS. THE CAPT WAS A CHK AIRMAN AND INSTRUCTOR. HE TRAINED ME TO BE FO ON THE AIRPLANE WE WERE FLYING LAST 5/91. I WAS SO CONFIDENT HE WOULD DO AN ILS CORRECTLY. I MUST LEARN NEVER TO ASSUME THE CAPT IS INFALLIBLE.

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.