Narrative:

Sux runway 21 reporting 1800 ft RVR. I had a directional gyro which was precessing off heading excessively, but I opted to attempt the approach anyway. I kept moving the heading bug right, trying to correct for instrument error. It took all my concentration to stay on localizer and glide. I got to 1630 ft which is MSL minimums and looked out. All I saw was fog. I suddenly saw ground contact to my left and turned my head to look. I saw an air carrier B757 waiting to depart. I looked ahead and the altimeter said 1500 ft, 130 ft under minimums with nothing visible ahead. I pulled up hard, applied full power, and climbed out. I missed the ground by perhaps 70 ft. I attribute this near accident to 3 factors: 1) I was preoccupied with an instrument problem, 2) I did not immediately execute a missed, and 3) having done 4 near minimums ILS's in the last month, I had every expectation that I would be successful. I forgot to raise the gear until 2000 ft AGL and didn't get rid of approach flaps until en route to my VFR alternate. I reported to approach control that my directional gyro was shot and they let me divert to pir which was VFR at the time. I will never again be so complacent about fog and I will not attempt it with defective equipment. And I will expect to go missed.

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Original NASA ASRS Text

Title: A PA34 PLT ATTEMPTS AN ILS APCH WITH A GYRO THAT IS MALFUNCTIONING AND LETS HIMSELF GET 130 FT BELOW MINIMUMS BEFORE GOING MISSED.

Narrative: SUX RWY 21 RPTING 1800 FT RVR. I HAD A DIRECTIONAL GYRO WHICH WAS PRECESSING OFF HDG EXCESSIVELY, BUT I OPTED TO ATTEMPT THE APCH ANYWAY. I KEPT MOVING THE HDG BUG R, TRYING TO CORRECT FOR INST ERROR. IT TOOK ALL MY CONCENTRATION TO STAY ON LOC AND GLIDE. I GOT TO 1630 FT WHICH IS MSL MINIMUMS AND LOOKED OUT. ALL I SAW WAS FOG. I SUDDENLY SAW GND CONTACT TO MY L AND TURNED MY HEAD TO LOOK. I SAW AN ACR B757 WAITING TO DEPART. I LOOKED AHEAD AND THE ALTIMETER SAID 1500 FT, 130 FT UNDER MINIMUMS WITH NOTHING VISIBLE AHEAD. I PULLED UP HARD, APPLIED FULL PWR, AND CLBED OUT. I MISSED THE GND BY PERHAPS 70 FT. I ATTRIBUTE THIS NEAR ACCIDENT TO 3 FACTORS: 1) I WAS PREOCCUPIED WITH AN INST PROB, 2) I DID NOT IMMEDIATELY EXECUTE A MISSED, AND 3) HAVING DONE 4 NEAR MINIMUMS ILS'S IN THE LAST MONTH, I HAD EVERY EXPECTATION THAT I WOULD BE SUCCESSFUL. I FORGOT TO RAISE THE GEAR UNTIL 2000 FT AGL AND DIDN'T GET RID OF APCH FLAPS UNTIL ENRTE TO MY VFR ALTERNATE. I RPTED TO APCH CTL THAT MY DIRECTIONAL GYRO WAS SHOT AND THEY LET ME DIVERT TO PIR WHICH WAS VFR AT THE TIME. I WILL NEVER AGAIN BE SO COMPLACENT ABOUT FOG AND I WILL NOT ATTEMPT IT WITH DEFECTIVE EQUIP. AND I WILL EXPECT TO GO MISSED.

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.