Narrative:

On the transition from en route to approach, clarksburg approach asked if I wanted a visual approach. I opted for the ILS runway 21, not because I couldn't have done it visually, but because I wanted to try to the coupling of my autoplt with the localizer. Although on an IFR flight plan, the conditions were VFR, so I would see the runway when within about 5 mi and 1700 ft AGL. When I intercepted the approach course (with radar vectors), I engaged the autoplt. I also noticed that the GS indicator was not picking up a signal. I was handed off to the tower about then and asked the tower if the GS was working. They said they thought it was, but that someone earlier in the day also reported it not working. As I got within about 3 mi of the runway, I noticed I was well off the centerline and at that time I disengaged the autoplt and did a visual approach. After I landed, I asked the linking pilot as he had arrived just before me, and he said it was working. When I was taxiing for departure, I still couldn't pick it up. I then realized that I was tuned to the VOR rather than the ILS. The reason it seemed to work for the approach (ie, the autoplt was able to track a course) was that the VOR is in line with the runway, so the CDI was essentially tracking the VOR inbound and brought me near the runway, more or less. In effect, I mentally shifted to a localizer approach because the GS wasn't working and was actually doing a VOR approach because I was tuned to the VOR and it happened to be located in line with the runway. The control tower (and approach control) at airports where the VOR is in line with runway should be made aware of this potential mix-up. If a pilot asks if the GS is working, they should automatically come back with the correct frequency, assuming it is not actually OTS. Something like, 'we've had no previous reports of problems, confirm you are on 109.3.' this apparently happened to a pilot earlier in the day at this airport, so it is not unique. In fact, any time a pilot questions whether the GS is working, it would be a good idea for ATC to have them verify the frequency.

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Original NASA ASRS Text

Title: A PA28 PLT, ON AN ILS APCH TO CKB, WAS UNABLE TO VERIFY GS IDENT AND BECAME DISPLACED FROM RWY CTRLINE DUE TO HAVING THE VOR FREQ TUNED IN INSTEAD OF THE ILS FREQ!

Narrative: ON THE TRANSITION FROM ENRTE TO APCH, CLARKSBURG APCH ASKED IF I WANTED A VISUAL APCH. I OPTED FOR THE ILS RWY 21, NOT BECAUSE I COULDN'T HAVE DONE IT VISUALLY, BUT BECAUSE I WANTED TO TRY TO THE COUPLING OF MY AUTOPLT WITH THE LOC. ALTHOUGH ON AN IFR FLT PLAN, THE CONDITIONS WERE VFR, SO I WOULD SEE THE RWY WHEN WITHIN ABOUT 5 MI AND 1700 FT AGL. WHEN I INTERCEPTED THE APCH COURSE (WITH RADAR VECTORS), I ENGAGED THE AUTOPLT. I ALSO NOTICED THAT THE GS INDICATOR WAS NOT PICKING UP A SIGNAL. I WAS HANDED OFF TO THE TWR ABOUT THEN AND ASKED THE TWR IF THE GS WAS WORKING. THEY SAID THEY THOUGHT IT WAS, BUT THAT SOMEONE EARLIER IN THE DAY ALSO RPTED IT NOT WORKING. AS I GOT WITHIN ABOUT 3 MI OF THE RWY, I NOTICED I WAS WELL OFF THE CTRLINE AND AT THAT TIME I DISENGAGED THE AUTOPLT AND DID A VISUAL APCH. AFTER I LANDED, I ASKED THE LINKING PLT AS HE HAD ARRIVED JUST BEFORE ME, AND HE SAID IT WAS WORKING. WHEN I WAS TAXIING FOR DEP, I STILL COULDN'T PICK IT UP. I THEN REALIZED THAT I WAS TUNED TO THE VOR RATHER THAN THE ILS. THE REASON IT SEEMED TO WORK FOR THE APCH (IE, THE AUTOPLT WAS ABLE TO TRACK A COURSE) WAS THAT THE VOR IS IN LINE WITH THE RWY, SO THE CDI WAS ESSENTIALLY TRACKING THE VOR INBOUND AND BROUGHT ME NEAR THE RWY, MORE OR LESS. IN EFFECT, I MENTALLY SHIFTED TO A LOC APCH BECAUSE THE GS WASN'T WORKING AND WAS ACTUALLY DOING A VOR APCH BECAUSE I WAS TUNED TO THE VOR AND IT HAPPENED TO BE LOCATED IN LINE WITH THE RWY. THE CTL TWR (AND APCH CTL) AT ARPTS WHERE THE VOR IS IN LINE WITH RWY SHOULD BE MADE AWARE OF THIS POTENTIAL MIX-UP. IF A PLT ASKS IF THE GS IS WORKING, THEY SHOULD AUTOMATICALLY COME BACK WITH THE CORRECT FREQ, ASSUMING IT IS NOT ACTUALLY OTS. SOMETHING LIKE, 'WE'VE HAD NO PREVIOUS RPTS OF PROBS, CONFIRM YOU ARE ON 109.3.' THIS APPARENTLY HAPPENED TO A PLT EARLIER IN THE DAY AT THIS ARPT, SO IT IS NOT UNIQUE. IN FACT, ANY TIME A PLT QUESTIONS WHETHER THE GS IS WORKING, IT WOULD BE A GOOD IDEA FOR ATC TO HAVE THEM VERIFY THE FREQ.

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.