Narrative:

On IFR flight to vny I had received my final vector for the ILS runway 16R to vny. The localizer was idented and both localizer and GS needles were alive -- no flags, and receiving proper identify. DME was giving distance readout to vny. The localizer and GS both captured and I began my descent on GS. Rate of descent was approximately 850 FPM, speed 120 KTS. At this point, I was instructed by socal approach to contact vny tower. I made initial call to tower, continuing the approach. Needles both centered. After crossing the OM, I received a low altitude alert call from tower to check altitude immediately. Again both needles were centered with no flags. I looked at my altimeter then back to the GS and at first glance everything seemed normal. Tower then called again and asked if the airport was in sight. I said no. They then asked was my GS working. I said yes, then received another altitude alert. At this point I leveled off and stopped the descent. There was no change on GS indication. Tower again asked if my GS was working. I replied, I am having problems with the GS and it may be inoperative. Tower replied, state intentions, which I replied, I am going missed approach. Tower gave me a heading and altitude and I was handed off to socal approach. Approach asked me what I would like to do. I told them I would like the VOR approach into vny. They were very helpful and gave me radar vectors for the VOR approach. I flew the approach, contacted vny tower and landed. The aircraft was being flown to vny for UHF radio maintenance. I explained what had happened to the avionics mechanic. The mechanic/technician informed me after testing the navigation radios, that indeed I was receiving the ILS signal. Hence, that is why there were no flags on my GS. However, the GS needle 'froze' at the center position, giving me a false indication of being right on GS. Hence, explaining my low altitude. GS's are great instruments. However, like everything else, they are subject to break or become inoperative. In hindsight, I should have realized this sooner by noting my distance and altitude from the airport. Low altitude alerts are there for a reason and I am grateful. Again I should have been quicker to realize something was amiss. After executing the missed approach and flying the VOR approach to land, I felt that filling out this report would be a help if I could share this with others. The GS was repaired that very day and I flew home to myf IFR to an ILS approach and landing. Only this time paying much more attention to my altitude!

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Original NASA ASRS Text

Title: A C182 ON AN ILS APCH TO VNY DSNDED BELOW GS ALTS WHILE FLYING THE APCH WITH A STUCK GS INDICATOR. VNY TWR NOTED THE DISCREPANCY AND WAS INSTRUMENTAL IN THE PLT GOING AROUND.

Narrative: ON IFR FLT TO VNY I HAD RECEIVED MY FINAL VECTOR FOR THE ILS RWY 16R TO VNY. THE LOC WAS IDENTED AND BOTH LOC AND GS NEEDLES WERE ALIVE -- NO FLAGS, AND RECEIVING PROPER IDENT. DME WAS GIVING DISTANCE READOUT TO VNY. THE LOC AND GS BOTH CAPTURED AND I BEGAN MY DSCNT ON GS. RATE OF DSCNT WAS APPROX 850 FPM, SPD 120 KTS. AT THIS POINT, I WAS INSTRUCTED BY SOCAL APCH TO CONTACT VNY TWR. I MADE INITIAL CALL TO TWR, CONTINUING THE APCH. NEEDLES BOTH CTRED. AFTER XING THE OM, I RECEIVED A LOW ALT ALERT CALL FROM TWR TO CHK ALT IMMEDIATELY. AGAIN BOTH NEEDLES WERE CTRED WITH NO FLAGS. I LOOKED AT MY ALTIMETER THEN BACK TO THE GS AND AT FIRST GLANCE EVERYTHING SEEMED NORMAL. TWR THEN CALLED AGAIN AND ASKED IF THE ARPT WAS IN SIGHT. I SAID NO. THEY THEN ASKED WAS MY GS WORKING. I SAID YES, THEN RECEIVED ANOTHER ALT ALERT. AT THIS POINT I LEVELED OFF AND STOPPED THE DSCNT. THERE WAS NO CHANGE ON GS INDICATION. TWR AGAIN ASKED IF MY GS WAS WORKING. I REPLIED, I AM HAVING PROBS WITH THE GS AND IT MAY BE INOP. TWR REPLIED, STATE INTENTIONS, WHICH I REPLIED, I AM GOING MISSED APCH. TWR GAVE ME A HDG AND ALT AND I WAS HANDED OFF TO SOCAL APCH. APCH ASKED ME WHAT I WOULD LIKE TO DO. I TOLD THEM I WOULD LIKE THE VOR APCH INTO VNY. THEY WERE VERY HELPFUL AND GAVE ME RADAR VECTORS FOR THE VOR APCH. I FLEW THE APCH, CONTACTED VNY TWR AND LANDED. THE ACFT WAS BEING FLOWN TO VNY FOR UHF RADIO MAINT. I EXPLAINED WHAT HAD HAPPENED TO THE AVIONICS MECH. THE MECH/TECHNICIAN INFORMED ME AFTER TESTING THE NAV RADIOS, THAT INDEED I WAS RECEIVING THE ILS SIGNAL. HENCE, THAT IS WHY THERE WERE NO FLAGS ON MY GS. HOWEVER, THE GS NEEDLE 'FROZE' AT THE CTR POS, GIVING ME A FALSE INDICATION OF BEING RIGHT ON GS. HENCE, EXPLAINING MY LOW ALT. GS'S ARE GREAT INSTS. HOWEVER, LIKE EVERYTHING ELSE, THEY ARE SUBJECT TO BREAK OR BECOME INOP. IN HINDSIGHT, I SHOULD HAVE REALIZED THIS SOONER BY NOTING MY DISTANCE AND ALT FROM THE ARPT. LOW ALT ALERTS ARE THERE FOR A REASON AND I AM GRATEFUL. AGAIN I SHOULD HAVE BEEN QUICKER TO REALIZE SOMETHING WAS AMISS. AFTER EXECUTING THE MISSED APCH AND FLYING THE VOR APCH TO LAND, I FELT THAT FILLING OUT THIS RPT WOULD BE A HELP IF I COULD SHARE THIS WITH OTHERS. THE GS WAS REPAIRED THAT VERY DAY AND I FLEW HOME TO MYF IFR TO AN ILS APCH AND LNDG. ONLY THIS TIME PAYING MUCH MORE ATTN TO MY ALT!

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.