Narrative:

Runway 2 ILS at sgf, mo, first officer flying using autoplt coupled to ILS. At approximately 800 ft AGL, I noticed GPWS fail light illuminate, followed immediately by localizer and GS off flags, and flight director command bars biasing out of view. This condition lasted a very short time, (less than 2 seconds) until all instruments returned to normal. Autoplt remained engaged. Between 400 ft AGL and 300 ft AGL, the above condition repeated itself, except at this time, the localizer and GS off flags remained in view. We executed the published missed approach. In the next 10-15 mins, 2 other aircraft attempted this same approach, and reported instrument failure at or near decision ht. At least 1 other aircraft behind us attempted and competed the approach with no reported problem. On our second approach, instrumentation was normal, but WX was not adequate for landing. On our third approach, instrumentation was again ok. We saw the runway at decision ht and landed. Throughout this time frame, I queried the controller several times as to the condition of the ILS transmitter. His reply was 'I have 2 green lights, no problem indicated, everything looks ok here' etc, etc.

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Original NASA ASRS Text

Title: AN ACR LGT, ALONG WITH SOME OTHER NON-RPTING ACFT, SUFFERED ILS FAILURE INDICATIONS TO SGF IN THE WX. SEVERAL GARS HAD TO BE PERFORMED.

Narrative: RWY 2 ILS AT SGF, MO, FO FLYING USING AUTOPLT COUPLED TO ILS. AT APPROX 800 FT AGL, I NOTICED GPWS FAIL LIGHT ILLUMINATE, FOLLOWED IMMEDIATELY BY LOC AND GS OFF FLAGS, AND FLT DIRECTOR COMMAND BARS BIASING OUT OF VIEW. THIS CONDITION LASTED A VERY SHORT TIME, (LESS THAN 2 SECONDS) UNTIL ALL INSTS RETURNED TO NORMAL. AUTOPLT REMAINED ENGAGED. BTWN 400 FT AGL AND 300 FT AGL, THE ABOVE CONDITION REPEATED ITSELF, EXCEPT AT THIS TIME, THE LOC AND GS OFF FLAGS REMAINED IN VIEW. WE EXECUTED THE PUBLISHED MISSED APCH. IN THE NEXT 10-15 MINS, 2 OTHER ACFT ATTEMPTED THIS SAME APCH, AND RPTED INST FAILURE AT OR NEAR DECISION HT. AT LEAST 1 OTHER ACFT BEHIND US ATTEMPTED AND COMPETED THE APCH WITH NO RPTED PROB. ON OUR SECOND APCH, INSTRUMENTATION WAS NORMAL, BUT WX WAS NOT ADEQUATE FOR LNDG. ON OUR THIRD APCH, INSTRUMENTATION WAS AGAIN OK. WE SAW THE RWY AT DECISION HT AND LANDED. THROUGHOUT THIS TIME FRAME, I QUERIED THE CTLR SEVERAL TIMES AS TO THE CONDITION OF THE ILS XMITTER. HIS REPLY WAS 'I HAVE 2 GREEN LIGHTS, NO PROB INDICATED, EVERYTHING LOOKS OK HERE' ETC, ETC.

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.