Narrative:

On the ILS approach to runway 9R at ord at approximately the deana OM, our aircraft experienced an interference/power surge/lost signal. Some type of unidentifiable interference to our navigation instruments and flight guidance. The loss of signal was immediate and sustained. A missed approach was executed due to loss of los and GS. The flight guidance and navigation instruments continued to be erratic throughout the missed approach procedure. After climbing to a safe altitude, we were vectored for a second attempt, which was entirely normal. Callback conversation with reporter revealed the following information: on the second approach, all the instrumentation operated normally. The reporter said when on the ground, maintenance tested the ILS system and found no faults. The reporter stated a call was made to the ATC controller and the incident was reported and ATC had no warnings of any failure on the localizer/GS facility. The reporter said the airplane maintenance history reviewed and no reports of instrumentation failure were found.

Related reports:

Google
 

Original NASA ASRS Text

Title: A B737-800 ON FINAL APCH AT 2500 FT EXECUTED A MISSED APCH DUE TO INTERFERENCE AND LOSS OF SIGNAL ON #1 AND #2 ILS AND GS.

Narrative: ON THE ILS APCH TO RWY 9R AT ORD AT APPROX THE DEANA OM, OUR ACFT EXPERIENCED AN INTERFERENCE/PWR SURGE/LOST SIGNAL. SOME TYPE OF UNIDENTIFIABLE INTERFERENCE TO OUR NAV INSTS AND FLT GUIDANCE. THE LOSS OF SIGNAL WAS IMMEDIATE AND SUSTAINED. A MISSED APCH WAS EXECUTED DUE TO LOSS OF LOS AND GS. THE FLT GUIDANCE AND NAV INSTS CONTINUED TO BE ERRATIC THROUGHOUT THE MISSED APCH PROC. AFTER CLBING TO A SAFE ALT, WE WERE VECTORED FOR A SECOND ATTEMPT, WHICH WAS ENTIRELY NORMAL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: ON THE SECOND APCH, ALL THE INSTRUMENTATION OPERATED NORMALLY. THE RPTR SAID WHEN ON THE GND, MAINT TESTED THE ILS SYS AND FOUND NO FAULTS. THE RPTR STATED A CALL WAS MADE TO THE ATC CTLR AND THE INCIDENT WAS RPTED AND ATC HAD NO WARNINGS OF ANY FAILURE ON THE LOC/GS FACILITY. THE RPTR SAID THE AIRPLANE MAINT HISTORY REVIEWED AND NO RPTS OF INSTRUMENTATION FAILURE WERE FOUND.

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.