Narrative:

I departed boulder municipal airport (1v5) runway 8 and climbed to 7400 ft MSL toward jeffco airport en route to centennial airport on a part 91 flight (1 pilot only, no passenger). Because jeffco tower was closed, I made a radio call on 118.6 and gave my position and intentions to fly over the airport at 7400 ft MSL. Again I reported at 7400 ft over the airport and again when I was 6 mi south of the airport. After my last report of reporting at 7400 ft, I immediately tuned in centennial ATIS while I was flying a course west of the denver city proper and west of I-25. At 10 mi northwest of centennial airport and then flew directly toward cherry creek reservoir. During that time I was listening to centennial ATIS, I noticed an aircraft with its landing light on at 12 O'clock position coming straight toward me and I decided to climb to 7700 ft MSL. At 15 mi on my GPS, I called centennial tower 118.9 and reported my position and intentions. The tower told me at that time that den departure had called her and said I had busted a corner of the class B airspace at over 8000 ft MSL. I came back to her and said that, how could that be true since my highest altitude I had been was 7700 ft MSL. She came back to me and asked me what my altitude was and I said 7700 ft. She then asked me to report over cherry creek reservoir. At that point I was cleared to land on runway 17R. The tower never mentioned the ATC incident with me again, nor did she ask me to call ZDV. I believe the cause of the problem might have been an error in the mode C transponder in my airplane since the beechcraft baron had been outside all night and was cold soaked or the ZDV center had a problem with their receiving my 1200 VFR transponder code. To prevent this recurrence again, I will talk to den departure and communicate with them through this corridor.

Google
 

Original NASA ASRS Text

Title: BE58 PLT INADVERTENTLY SHOWN ON RADAR AS IN CLASS B AIRSPACE WHEN HIS MODE C XPONDER XMITTED AN ALT NOT CORRESPONDING WITH THE ALT SHOWN ON HIS ALTIMETER.

Narrative: I DEPARTED BOULDER MUNICIPAL ARPT (1V5) RWY 8 AND CLBED TO 7400 FT MSL TOWARD JEFFCO ARPT ENRTE TO CENTENNIAL ARPT ON A PART 91 FLT (1 PLT ONLY, NO PAX). BECAUSE JEFFCO TWR WAS CLOSED, I MADE A RADIO CALL ON 118.6 AND GAVE MY POS AND INTENTIONS TO FLY OVER THE ARPT AT 7400 FT MSL. AGAIN I RPTED AT 7400 FT OVER THE ARPT AND AGAIN WHEN I WAS 6 MI S OF THE ARPT. AFTER MY LAST RPT OF RPTING AT 7400 FT, I IMMEDIATELY TUNED IN CENTENNIAL ATIS WHILE I WAS FLYING A COURSE W OF THE DENVER CITY PROPER AND W OF I-25. AT 10 MI NW OF CENTENNIAL ARPT AND THEN FLEW DIRECTLY TOWARD CHERRY CREEK RESERVOIR. DURING THAT TIME I WAS LISTENING TO CENTENNIAL ATIS, I NOTICED AN ACFT WITH ITS LNDG LIGHT ON AT 12 O'CLOCK POS COMING STRAIGHT TOWARD ME AND I DECIDED TO CLB TO 7700 FT MSL. AT 15 MI ON MY GPS, I CALLED CENTENNIAL TWR 118.9 AND RPTED MY POS AND INTENTIONS. THE TWR TOLD ME AT THAT TIME THAT DEN DEP HAD CALLED HER AND SAID I HAD BUSTED A CORNER OF THE CLASS B AIRSPACE AT OVER 8000 FT MSL. I CAME BACK TO HER AND SAID THAT, HOW COULD THAT BE TRUE SINCE MY HIGHEST ALT I HAD BEEN WAS 7700 FT MSL. SHE CAME BACK TO ME AND ASKED ME WHAT MY ALT WAS AND I SAID 7700 FT. SHE THEN ASKED ME TO RPT OVER CHERRY CREEK RESERVOIR. AT THAT POINT I WAS CLRED TO LAND ON RWY 17R. THE TWR NEVER MENTIONED THE ATC INCIDENT WITH ME AGAIN, NOR DID SHE ASK ME TO CALL ZDV. I BELIEVE THE CAUSE OF THE PROB MIGHT HAVE BEEN AN ERROR IN THE MODE C XPONDER IN MY AIRPLANE SINCE THE BEECHCRAFT BARON HAD BEEN OUTSIDE ALL NIGHT AND WAS COLD SOAKED OR THE ZDV CTR HAD A PROB WITH THEIR RECEIVING MY 1200 VFR XPONDER CODE. TO PREVENT THIS RECURRENCE AGAIN, I WILL TALK TO DEN DEP AND COMMUNICATE WITH THEM THROUGH THIS CORRIDOR.

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.