Narrative:

I was vectored to intercept the localizer back course outside frits intersection at 5200 ft. Around 10 ilbb DME, I started my descent from 5200 ft to 4800 ft. Approximately 6 or 5 ilbb DME the controller (I believe I was now on the tower) notified me he was receiving a low altitude alert. I checked my altitude and it read 4800 ft, and I started a climb back to 5200 ft. Now I'm passing frier and now I'm descending again to 3820 ft. I had ground contact, but did not have runway environment in sight. I was 2 dots right of course and correcting and the 'rabbits' came in visually at enzie and I landed without further incident. After taxiing to the ramp I asked the tower what altitude they thought I should be at between frits and frier and I was informed that I needed to be at 5200 ft. As you can see, the approach plate clearly showed 4800 ft is the altitude. By having to rechk my approach plate at the final approach fix, made for extra workload at a critical time of the approach. I climbed back to 5200 ft, because I would rather be alive, high, 'than be dead right.' I turned this information over to our safety director and suggested he check with commercial to see if there is a mistake on the approach plate. Callback conversation with reporter revealed the following information: reporter stated that other atx, and other company pilots, have also gotten a low altitude alert when making that same approach down to the chart depicted 4800 ft altitude. Therefore, when the controller stated that they should be at 5200 ft it seemed reasonable due to the altitude alerts. There are 2 high transmitting antennas just off to the left of the final approach course which probably causes the altitude alerts. He also checked the government chart and found it to show the 4800 ft.

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Original NASA ASRS Text

Title: ATX PLT OF A CESSNA 208B CARAVAN WAS INFORMED BY TWR CTLR DURING A BACK COURSE LOC APCH THAT A LOW ALT ALERT WAS RECEIVED JUST OUTSIDE OF THE FINAL APCH FIX. HE IMMEDIATELY CLBED BACK TO THE TRANSITION MINIMUM ALT. HOWEVER, HIS COMMERCIAL CHART DEPICTED THE LOWER ALT AT WHICH HE HAD DSNDED AS THE MINIMUM ALT FOR THE FINAL APCH FIX.

Narrative: I WAS VECTORED TO INTERCEPT THE LOC BACK COURSE OUTSIDE FRITS INTXN AT 5200 FT. AROUND 10 ILBB DME, I STARTED MY DSCNT FROM 5200 FT TO 4800 FT. APPROX 6 OR 5 ILBB DME THE CTLR (I BELIEVE I WAS NOW ON THE TWR) NOTIFIED ME HE WAS RECEIVING A LOW ALT ALERT. I CHKED MY ALT AND IT READ 4800 FT, AND I STARTED A CLB BACK TO 5200 FT. NOW I'M PASSING FRIER AND NOW I'M DSNDING AGAIN TO 3820 FT. I HAD GND CONTACT, BUT DID NOT HAVE RWY ENVIRONMENT IN SIGHT. I WAS 2 DOTS R OF COURSE AND CORRECTING AND THE 'RABBITS' CAME IN VISUALLY AT ENZIE AND I LANDED WITHOUT FURTHER INCIDENT. AFTER TAXIING TO THE RAMP I ASKED THE TWR WHAT ALT THEY THOUGHT I SHOULD BE AT BTWN FRITS AND FRIER AND I WAS INFORMED THAT I NEEDED TO BE AT 5200 FT. AS YOU CAN SEE, THE APCH PLATE CLRLY SHOWED 4800 FT IS THE ALT. BY HAVING TO RECHK MY APCH PLATE AT THE FINAL APCH FIX, MADE FOR EXTRA WORKLOAD AT A CRITICAL TIME OF THE APCH. I CLBED BACK TO 5200 FT, BECAUSE I WOULD RATHER BE ALIVE, HIGH, 'THAN BE DEAD RIGHT.' I TURNED THIS INFO OVER TO OUR SAFETY DIRECTOR AND SUGGESTED HE CHK WITH COMMERCIAL TO SEE IF THERE IS A MISTAKE ON THE APCH PLATE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT OTHER ATX, AND OTHER COMPANY PLTS, HAVE ALSO GOTTEN A LOW ALT ALERT WHEN MAKING THAT SAME APCH DOWN TO THE CHART DEPICTED 4800 FT ALT. THEREFORE, WHEN THE CTLR STATED THAT THEY SHOULD BE AT 5200 FT IT SEEMED REASONABLE DUE TO THE ALT ALERTS. THERE ARE 2 HIGH XMITTING ANTENNAS JUST OFF TO THE L OF THE FINAL APCH COURSE WHICH PROBABLY CAUSES THE ALT ALERTS. HE ALSO CHKED THE GOV CHART AND FOUND IT TO SHOW THE 4800 FT.

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.