Narrative:

While on the ILS approach to runway 13R, I executed a go around due to, what I perceived as, unreliable navigation information. As we were approaching the FAF and beginning to capture the GS, the GS indications became very erratic. Indications were normal when suddenly the GS deflected full scale up and almost immediately full scale down. I stopped my descent upon the first GS deviation, at about 2600 ft still IMC, then executed a go around once the GS deflected again. We informed tower of the go around and received a rather confusing instruction to 'climb to 2000 ft on runway heading, then at departure end climb to 3000 ft.' these instructions were impossible to comply with at the time, since we were climbing, go around procedures, and still IMC, unable to identify departure end. I initially attempted to comply with a descent to 2000 ft from about 3000 ft, after the go around, but this was a very uncomfortable and difficult maneuver. Once the descent was started we received a 'traffic, traffic' alert from our TCASII, and at the same time received a new clearance to 'climb to 3000 ft immediately.' when stable at 3000 ft and on a vector back to dal, we asked if the ILS to runway 13R was operating normally and the response was 'yes.' 2 factors started out for me affecting this situation. First the GS indications were very unusual and I have seen this happen before with the use of cell phones on board the aircraft. On downwind for our next approach into dal, I asked the passenger to turn off and not use their cell phones. Secondly, the conflicting altitude instructions during our go around were very confusing. My first officer was reading the missed approach procedures, which include a climb to 5000 ft, and receiving the 'climb to 2000 ft,' later changed to 'maintain 3000 ft.' of course, traffic concerns played a major role in the instructions we received. With our unexpected go around, as visual approachs were being flown, some quick decisions had to be made. Everyone involved was tested during this short time frame, and correct actions were taken. Our second approach into dal was uneventful and all ILS indications were normal during our visual approach.

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Original NASA ASRS Text

Title: GS INDICATOR GIVES ERRONEOUS INFO. FLC EXECUTES GAR.

Narrative: WHILE ON THE ILS APCH TO RWY 13R, I EXECUTED A GAR DUE TO, WHAT I PERCEIVED AS, UNRELIABLE NAV INFO. AS WE WERE APCHING THE FAF AND BEGINNING TO CAPTURE THE GS, THE GS INDICATIONS BECAME VERY ERRATIC. INDICATIONS WERE NORMAL WHEN SUDDENLY THE GS DEFLECTED FULL SCALE UP AND ALMOST IMMEDIATELY FULL SCALE DOWN. I STOPPED MY DSCNT UPON THE FIRST GS DEV, AT ABOUT 2600 FT STILL IMC, THEN EXECUTED A GAR ONCE THE GS DEFLECTED AGAIN. WE INFORMED TWR OF THE GAR AND RECEIVED A RATHER CONFUSING INSTRUCTION TO 'CLB TO 2000 FT ON RWY HDG, THEN AT DEP END CLB TO 3000 FT.' THESE INSTRUCTIONS WERE IMPOSSIBLE TO COMPLY WITH AT THE TIME, SINCE WE WERE CLBING, GAR PROCS, AND STILL IMC, UNABLE TO IDENT DEP END. I INITIALLY ATTEMPTED TO COMPLY WITH A DSCNT TO 2000 FT FROM ABOUT 3000 FT, AFTER THE GAR, BUT THIS WAS A VERY UNCOMFORTABLE AND DIFFICULT MANEUVER. ONCE THE DSCNT WAS STARTED WE RECEIVED A 'TFC, TFC' ALERT FROM OUR TCASII, AND AT THE SAME TIME RECEIVED A NEW CLRNC TO 'CLB TO 3000 FT IMMEDIATELY.' WHEN STABLE AT 3000 FT AND ON A VECTOR BACK TO DAL, WE ASKED IF THE ILS TO RWY 13R WAS OPERATING NORMALLY AND THE RESPONSE WAS 'YES.' 2 FACTORS STARTED OUT FOR ME AFFECTING THIS SIT. FIRST THE GS INDICATIONS WERE VERY UNUSUAL AND I HAVE SEEN THIS HAPPEN BEFORE WITH THE USE OF CELL PHONES ON BOARD THE ACFT. ON DOWNWIND FOR OUR NEXT APCH INTO DAL, I ASKED THE PAX TO TURN OFF AND NOT USE THEIR CELL PHONES. SECONDLY, THE CONFLICTING ALT INSTRUCTIONS DURING OUR GAR WERE VERY CONFUSING. MY FO WAS READING THE MISSED APCH PROCS, WHICH INCLUDE A CLB TO 5000 FT, AND RECEIVING THE 'CLB TO 2000 FT,' LATER CHANGED TO 'MAINTAIN 3000 FT.' OF COURSE, TFC CONCERNS PLAYED A MAJOR ROLE IN THE INSTRUCTIONS WE RECEIVED. WITH OUR UNEXPECTED GAR, AS VISUAL APCHS WERE BEING FLOWN, SOME QUICK DECISIONS HAD TO BE MADE. EVERYONE INVOLVED WAS TESTED DURING THIS SHORT TIME FRAME, AND CORRECT ACTIONS WERE TAKEN. OUR SECOND APCH INTO DAL WAS UNEVENTFUL AND ALL ILS INDICATIONS WERE NORMAL DURING OUR VISUAL APCH.

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.