Narrative:

Established on ILS final runway 17, captain and first officer both on ILS. Approximately 1500-1000 ft MSL flags appear both sides, ILS signal lost. Have ground contact clearly, but runway not in sight. Captain switched to LNAV. At 1000 ft AGL I call '1000 ft' no contact.' captain made a reference to ground contact and continuing, that we should pick it up soon. At approximately 300 ft we picked up the runway. We were approximately 3/4 mi out and approximately 1/2 mi left of runway centerline. Captain attempted to line-up with the runway unsuccessfully. Executed a missed approach at approximately 100 ft AGL. Vectored to ILS 35 to uneventful landing. After missed approach ATC apologized for inadvertently switching the ILS to runway 35 during our approach. We should have executed a missed approach as soon as the ILS signal was lost. We both felt like we would pick up the runway momentarily. The 'borderline' WX, flat terrain, LNAV backup and familiarity with the airport all made it possible to continue the approach. Should have executed a missed approach after picking up the runway since we were not in a position to make normal landing due to the maneuvering required. I know what we should have done and won't make the same mistake again.

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Original NASA ASRS Text

Title: MLG EXECUTES MAP DUE TO POOR ALIGNMENT WITH RWY CAUSED BY ATC SWITCHING THE ILS.

Narrative: ESTABLISHED ON ILS FINAL RWY 17, CAPT AND FO BOTH ON ILS. APPROX 1500-1000 FT MSL FLAGS APPEAR BOTH SIDES, ILS SIGNAL LOST. HAVE GND CONTACT CLRLY, BUT RWY NOT IN SIGHT. CAPT SWITCHED TO LNAV. AT 1000 FT AGL I CALL '1000 FT' NO CONTACT.' CAPT MADE A REF TO GND CONTACT AND CONTINUING, THAT WE SHOULD PICK IT UP SOON. AT APPROX 300 FT WE PICKED UP THE RWY. WE WERE APPROX 3/4 MI OUT AND APPROX 1/2 MI L OF RWY CTRLINE. CAPT ATTEMPTED TO LINE-UP WITH THE RWY UNSUCCESSFULLY. EXECUTED A MISSED APCH AT APPROX 100 FT AGL. VECTORED TO ILS 35 TO UNEVENTFUL LNDG. AFTER MISSED APCH ATC APOLOGIZED FOR INADVERTENTLY SWITCHING THE ILS TO RWY 35 DURING OUR APCH. WE SHOULD HAVE EXECUTED A MISSED APCH AS SOON AS THE ILS SIGNAL WAS LOST. WE BOTH FELT LIKE WE WOULD PICK UP THE RWY MOMENTARILY. THE 'BORDERLINE' WX, FLAT TERRAIN, LNAV BACKUP AND FAMILIARITY WITH THE ARPT ALL MADE IT POSSIBLE TO CONTINUE THE APCH. SHOULD HAVE EXECUTED A MISSED APCH AFTER PICKING UP THE RWY SINCE WE WERE NOT IN A POS TO MAKE NORMAL LNDG DUE TO THE MANEUVERING REQUIRED. I KNOW WHAT WE SHOULD HAVE DONE AND WON'T MAKE THE SAME MISTAKE AGAIN.

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.