Narrative:

Contacted ful tower after departing cno airport. Advised 12 mi east inbound with ATIS. Followed localizer in 3 mi haze with poor horizontal visibility backlit by sun. Tracked localizer inbound while VFR to help identify airport boundary. Maintained 2000 ft MSL until passing qewti (5.6 DME). Started descent to 880 ft as published with expectation to continue descent to airport after conga. At approximately 5.0 DME while descending, a male voice came on the 119.1 tower frequency and stated 'you are too low.' as there are some tall obstacles around this airport, I commenced with a rapid climb to 1700 ft MSL until I was within 2.5 DME of the airport and had positive identify of the airport threshold. I don't believe this voice was the single controller on duty. It sounded like a hand-held portable radio. This could have produced a disaster if other traffic was overheard. Callback conversation with reporter revealed the following information: pilot reported he was flying a piper PA32 aircraft. Visibility was poor due to typical lax smog. Pilot was following the instrument approach procedure 'localizer runway 24' procedure and was descending on the instrument step down profile. He has not seen this before, although he has heard of it happening to others. He did not report it to ful tower. He stated that the approach is over homes and he suspects that someone there was responsible.

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Original NASA ASRS Text

Title: SMA ACFT PLT WAS FOLLOWING THE PUBLISHED LOC RWY 24 APCH AT FUL. HE RECEIVED AN UNIDENTED RADIO XMISSION STATING 'YOU ARE TOO LOW.'

Narrative: CONTACTED FUL TWR AFTER DEPARTING CNO ARPT. ADVISED 12 MI E INBOUND WITH ATIS. FOLLOWED LOC IN 3 MI HAZE WITH POOR HORIZ VISIBILITY BACKLIT BY SUN. TRACKED LOC INBOUND WHILE VFR TO HELP IDENT ARPT BOUNDARY. MAINTAINED 2000 FT MSL UNTIL PASSING QEWTI (5.6 DME). STARTED DSCNT TO 880 FT AS PUBLISHED WITH EXPECTATION TO CONTINUE DSCNT TO ARPT AFTER CONGA. AT APPROX 5.0 DME WHILE DSNDING, A MALE VOICE CAME ON THE 119.1 TWR FREQ AND STATED 'YOU ARE TOO LOW.' AS THERE ARE SOME TALL OBSTACLES AROUND THIS ARPT, I COMMENCED WITH A RAPID CLB TO 1700 FT MSL UNTIL I WAS WITHIN 2.5 DME OF THE ARPT AND HAD POSITIVE IDENT OF THE ARPT THRESHOLD. I DON'T BELIEVE THIS VOICE WAS THE SINGLE CTLR ON DUTY. IT SOUNDED LIKE A HAND-HELD PORTABLE RADIO. THIS COULD HAVE PRODUCED A DISASTER IF OTHER TFC WAS OVERHEARD. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: PLT RPTED HE WAS FLYING A PIPER PA32 ACFT. VISIBILITY WAS POOR DUE TO TYPICAL LAX SMOG. PLT WAS FOLLOWING THE INST APCH PROC 'LOC RWY 24' PROC AND WAS DSNDING ON THE INST STEP DOWN PROFILE. HE HAS NOT SEEN THIS BEFORE, ALTHOUGH HE HAS HEARD OF IT HAPPENING TO OTHERS. HE DID NOT RPT IT TO FUL TWR. HE STATED THAT THE APCH IS OVER HOMES AND HE SUSPECTS THAT SOMEONE THERE WAS RESPONSIBLE.

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.