Narrative:

En route from columbia, sc, to florence, sc, 3500 ft in a C172 with 2 radios. Leaving cae airspace we squawked 1200. When coming close to ssc airspace we tried to contact ssc approach on frequency 125.4 and 118.85 (both frequencys on both radios). Unable to establish radio contact we started climbing to go above. (We did not have any problems with the radios anywhere else.) approximately abeam the airport the controller becomes audible on 125.4. Evaluating the situation afterwards, we remembered that when passing the same area on an east to west heading at 4500 ft about 1 hour earlier with radio contact, the frequency became suspiciously quiet after passing the airport. This raises the question if there was something blocking this signal on the west side of the airport at this time. I have flown in this area before and have not had any similar problem. Callback conversation with reporter revealed the following information: reporter states that this is not a problem most of the time. He has discussed this with several other flight instructors who have experienced the problem on occasion. It is such an intermittent problem that he did not notice until he was close to the class C airspace and climbed above to avoid it. The flight instructors and students have all been made aware of the frequency problem so hopefully no one else will get caught unaware.

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Original NASA ASRS Text

Title: TRAINING FLT ENCOUNTERS FREQ PROB TRYING TO MAKE CONTACT WITH TRACON FOR PASSAGE THROUGH CLASS C AIRSPACE.

Narrative: ENRTE FROM COLUMBIA, SC, TO FLORENCE, SC, 3500 FT IN A C172 WITH 2 RADIOS. LEAVING CAE AIRSPACE WE SQUAWKED 1200. WHEN COMING CLOSE TO SSC AIRSPACE WE TRIED TO CONTACT SSC APCH ON FREQ 125.4 AND 118.85 (BOTH FREQS ON BOTH RADIOS). UNABLE TO ESTABLISH RADIO CONTACT WE STARTED CLBING TO GO ABOVE. (WE DID NOT HAVE ANY PROBS WITH THE RADIOS ANYWHERE ELSE.) APPROX ABEAM THE ARPT THE CTLR BECOMES AUDIBLE ON 125.4. EVALUATING THE SIT AFTERWARDS, WE REMEMBERED THAT WHEN PASSING THE SAME AREA ON AN E TO W HDG AT 4500 FT ABOUT 1 HR EARLIER WITH RADIO CONTACT, THE FREQ BECAME SUSPICIOUSLY QUIET AFTER PASSING THE ARPT. THIS RAISES THE QUESTION IF THERE WAS SOMETHING BLOCKING THIS SIGNAL ON THE W SIDE OF THE ARPT AT THIS TIME. I HAVE FLOWN IN THIS AREA BEFORE AND HAVE NOT HAD ANY SIMILAR PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT THIS IS NOT A PROB MOST OF THE TIME. HE HAS DISCUSSED THIS WITH SEVERAL OTHER FLT INSTRUCTORS WHO HAVE EXPERIENCED THE PROB ON OCCASION. IT IS SUCH AN INTERMITTENT PROB THAT HE DID NOT NOTICE UNTIL HE WAS CLOSE TO THE CLASS C AIRSPACE AND CLBED ABOVE TO AVOID IT. THE FLT INSTRUCTORS AND STUDENTS HAVE ALL BEEN MADE AWARE OF THE FREQ PROB SO HOPEFULLY NO ONE ELSE WILL GET CAUGHT UNAWARE.

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.