Narrative:

I flew in accord with an IFR flight plan to day. The approachs in use were parallel ILS approachs to runways 24L and 24R. We were cleared for the ILS runway 24L approach, having been vectored to the FAF, and commenced to fly same. During the initial phase of this maneuver we drifted 3 dots to the right of course (toward the course of the parallel ILS). There was a left crosswind at that altitude, but I do not believe it was an unusual one. I remember thinking that the localizer was shifting too quickly for it to be a true indication (in fact it did shift out and back very quickly several times), and I decided not to chase it. At this point ATC inquired if we showed ourselves to the right of course. I am not sure why this occurred. I think that part of the problem with this flight was fatigue. It was the second to last day of a 6 week business trip. I had had a meeting the preceding day in nd and had flown IFR with ice, turbulence, the possibility of thunderstorms and O2 (at 17000') first officer 4 hours the night before. I think part of the problem was that the transmitter was broadcasting a false localizer signal which was erratic out by the FAF and improved as it came closer to the transmitter. Callback conversation with reporter revealed the following: this report is 1 of 3 reporter turned in from a 5 day series of flts on personal business. All events were trivial.

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Original NASA ASRS Text

Title: PLT OF PERSONAL BUSINESS SMT TWIN ACFT DRIFTED 3 DOTS TO RIGHT OF ILS COURSE ON IMC APCH.

Narrative: I FLEW IN ACCORD WITH AN IFR FLT PLAN TO DAY. THE APCHS IN USE WERE PARALLEL ILS APCHS TO RWYS 24L AND 24R. WE WERE CLRED FOR THE ILS RWY 24L APCH, HAVING BEEN VECTORED TO THE FAF, AND COMMENCED TO FLY SAME. DURING THE INITIAL PHASE OF THIS MANEUVER WE DRIFTED 3 DOTS TO THE RIGHT OF COURSE (TOWARD THE COURSE OF THE PARALLEL ILS). THERE WAS A LEFT XWIND AT THAT ALT, BUT I DO NOT BELIEVE IT WAS AN UNUSUAL ONE. I REMEMBER THINKING THAT THE LOC WAS SHIFTING TOO QUICKLY FOR IT TO BE A TRUE INDICATION (IN FACT IT DID SHIFT OUT AND BACK VERY QUICKLY SEVERAL TIMES), AND I DECIDED NOT TO CHASE IT. AT THIS POINT ATC INQUIRED IF WE SHOWED OURSELVES TO THE RIGHT OF COURSE. I AM NOT SURE WHY THIS OCCURRED. I THINK THAT PART OF THE PROB WITH THIS FLT WAS FATIGUE. IT WAS THE SECOND TO LAST DAY OF A 6 WK BUSINESS TRIP. I HAD HAD A MEETING THE PRECEDING DAY IN ND AND HAD FLOWN IFR WITH ICE, TURB, THE POSSIBILITY OF TSTMS AND O2 (AT 17000') FO 4 HRS THE NIGHT BEFORE. I THINK PART OF THE PROB WAS THAT THE XMITTER WAS BROADCASTING A FALSE LOC SIGNAL WHICH WAS ERRATIC OUT BY THE FAF AND IMPROVED AS IT CAME CLOSER TO THE XMITTER. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: THIS RPT IS 1 OF 3 RPTR TURNED IN FROM A 5 DAY SERIES OF FLTS ON PERSONAL BUSINESS. ALL EVENTS WERE TRIVIAL.

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.