Narrative:

GPWS was deferred by maintenance due to false warnings on previous flts. One of the restrs from the MEL was that no visual approachs were allowed, instrument approachs only. Meteorological conditions were unrestr ceiling and visibility in early morning daylight. We idented the airport and landing runway environment more than 40 mi out. The final approach controller advised that we could expect a visual approach to runway 12L. Abeam the final approach fix, the controller vectored us for a base-leg turn and asked if we had the airport in sight. We advised that due to an equipment limitation we had to conduct an instrument approach. The controller seemed mildly irritated asking why we didn't tell him 60 mi earlier and that he couldn't clear us for an approach so close to the final fix. I stated that a close-in turn was okay. The controller gave a final vector and a clearance to maintain 2500 ft and intercept the localizer for runway 12L. Intercepting the localizer virtually on top of the final approach fix, I started a descent to track the electronic glide path. The controller asked again if we had the airport in sight. Knowing that he would clear us for a visual approach which my MEL prohibited, I again stated that yes I could see the airport but we could not accept a visual approach. The controller asked our altitude. We were at approximately 2000 ft MSL and descending. The controller said he had not cleared us below 2500 ft. Immediately recognizing my error I executed a missed approach. The controller then gave us a full vector and clearance for the ILS approach and an uneventful landing was accomplished. My analysis: 1) I, and probably my crew, was very tired. We were at the end of a long duty day in the early am and still had a commercial deadhead remaining to return to domicile. I am aware of the insidious nature of fatigue and do my best to be aware of its onset. Fatigue is a factor we are constantly trained against and warned about due to our night freight flying. I didn't fully realize it at the time, but looking back I am certain my performance was less than 100%. This was also the last leg of a week long trip sequence. I don't believe there was a get-homeitis factor but it may have been a subtle influence. 2) complacency was certainly involved here. I wrongly assumed that my MEL restr due to the malfunctioning GPWS was of no consequence.I knew the WX was excellent and it was my intent to fly a half-baked visual instrument approach. There is no such procedure. One should either fly visually (where appropriate) or execute all the correct procedures of a proper instrument approach. My mindset was such that I heard the clearance but my predisposition to land visually caused me to neglect proper procedure. 3) I was inconsiderate of the approach controller. He had no knowledge of my equipment limitations and properly anticipated assigning us a visual approach. I should have informed him early on of our need to fly a full instrument approach. By excluding him from my planning loop I gave away part of my aviation safety net.

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Original NASA ASRS Text

Title: FLT CREW OF DC87 WITH MEL REQUIREMENT TO FLY ONLY INST APCHS MAKES A GAR AT STL WHEN CONFUSION BTWN THEIR NEEDS AND APCH CTL'S INTENTIONS RESULTS IN DSCNT BELOW CLRED ALT.

Narrative: GPWS WAS DEFERRED BY MAINT DUE TO FALSE WARNINGS ON PREVIOUS FLTS. ONE OF THE RESTRS FROM THE MEL WAS THAT NO VISUAL APCHS WERE ALLOWED, INST APCHS ONLY. METEOROLOGICAL CONDITIONS WERE UNRESTR CEILING AND VISIBILITY IN EARLY MORNING DAYLIGHT. WE IDENTED THE ARPT AND LNDG RWY ENVIRONMENT MORE THAN 40 MI OUT. THE FINAL APCH CTLR ADVISED THAT WE COULD EXPECT A VISUAL APCH TO RWY 12L. ABEAM THE FINAL APCH FIX, THE CTLR VECTORED US FOR A BASE-LEG TURN AND ASKED IF WE HAD THE ARPT IN SIGHT. WE ADVISED THAT DUE TO AN EQUIP LIMITATION WE HAD TO CONDUCT AN INST APCH. THE CTLR SEEMED MILDLY IRRITATED ASKING WHY WE DIDN'T TELL HIM 60 MI EARLIER AND THAT HE COULDN'T CLR US FOR AN APCH SO CLOSE TO THE FINAL FIX. I STATED THAT A CLOSE-IN TURN WAS OKAY. THE CTLR GAVE A FINAL VECTOR AND A CLRNC TO MAINTAIN 2500 FT AND INTERCEPT THE LOC FOR RWY 12L. INTERCEPTING THE LOC VIRTUALLY ON TOP OF THE FINAL APCH FIX, I STARTED A DSCNT TO TRACK THE ELECTRONIC GLIDE PATH. THE CTLR ASKED AGAIN IF WE HAD THE ARPT IN SIGHT. KNOWING THAT HE WOULD CLR US FOR A VISUAL APCH WHICH MY MEL PROHIBITED, I AGAIN STATED THAT YES I COULD SEE THE ARPT BUT WE COULD NOT ACCEPT A VISUAL APCH. THE CTLR ASKED OUR ALT. WE WERE AT APPROX 2000 FT MSL AND DSNDING. THE CTLR SAID HE HAD NOT CLRED US BELOW 2500 FT. IMMEDIATELY RECOGNIZING MY ERROR I EXECUTED A MISSED APCH. THE CTLR THEN GAVE US A FULL VECTOR AND CLRNC FOR THE ILS APCH AND AN UNEVENTFUL LNDG WAS ACCOMPLISHED. MY ANALYSIS: 1) I, AND PROBABLY MY CREW, WAS VERY TIRED. WE WERE AT THE END OF A LONG DUTY DAY IN THE EARLY AM AND STILL HAD A COMMERCIAL DEADHEAD REMAINING TO RETURN TO DOMICILE. I AM AWARE OF THE INSIDIOUS NATURE OF FATIGUE AND DO MY BEST TO BE AWARE OF ITS ONSET. FATIGUE IS A FACTOR WE ARE CONSTANTLY TRAINED AGAINST AND WARNED ABOUT DUE TO OUR NIGHT FREIGHT FLYING. I DIDN'T FULLY REALIZE IT AT THE TIME, BUT LOOKING BACK I AM CERTAIN MY PERFORMANCE WAS LESS THAN 100%. THIS WAS ALSO THE LAST LEG OF A WK LONG TRIP SEQUENCE. I DON'T BELIEVE THERE WAS A GET-HOMEITIS FACTOR BUT IT MAY HAVE BEEN A SUBTLE INFLUENCE. 2) COMPLACENCY WAS CERTAINLY INVOLVED HERE. I WRONGLY ASSUMED THAT MY MEL RESTR DUE TO THE MALFUNCTIONING GPWS WAS OF NO CONSEQUENCE.I KNEW THE WX WAS EXCELLENT AND IT WAS MY INTENT TO FLY A HALF-BAKED VISUAL INST APCH. THERE IS NO SUCH PROC. ONE SHOULD EITHER FLY VISUALLY (WHERE APPROPRIATE) OR EXECUTE ALL THE CORRECT PROCS OF A PROPER INST APCH. MY MINDSET WAS SUCH THAT I HEARD THE CLRNC BUT MY PREDISPOSITION TO LAND VISUALLY CAUSED ME TO NEGLECT PROPER PROC. 3) I WAS INCONSIDERATE OF THE APCH CTLR. HE HAD NO KNOWLEDGE OF MY EQUIP LIMITATIONS AND PROPERLY ANTICIPATED ASSIGNING US A VISUAL APCH. I SHOULD HAVE INFORMED HIM EARLY ON OF OUR NEED TO FLY A FULL INST APCH. BY EXCLUDING HIM FROM MY PLANNING LOOP I GAVE AWAY PART OF MY AVIATION SAFETY NET.

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.