Narrative:

I was flying bonanza, IFR equipped, but under VFR on a cross country flight, without a flight plan, from apa to 1v5. My intention was to use a route beneath the den class B airspace according to the approved and current sectional chart. The route was to be at a segment on the west side of the class B and at 7500 ft MSL. The floor in the area is 8000 ft MSL. I departed boulder intending to return by the same route as earlier. Sensing that den. Approach was busy I did not call for flight following. I set my altimeter to the boulder field elevation and noticed no problems with either the setting knob or the altimeter itself. In-flight on the return, I had an update from apa ATIS. When resetting the altimeter I noticed that the kohlsman knob was extremely stiff and became completely bound up. I discontinued trying to set it in favor of flying the aircraft. On final at apa about XA45 mdt I was requested by apa tower to call approach by telephone. I did and explained the malfunction. At no time did any instruments indicate I was in the class B airspace, not did I believe I was in the class B airspace. My transponder was also on and functioning on both flts. Since this event I had the altimeter checked and replaced. This was the first indication of any problem and after discovery I landed immediately and did not fly again until it was repaired.

Related reports:

Google
 

Original NASA ASRS Text

Title: A BEECH BONANZA PLT ENTERED D01 CLASS B AIRSPACE WITHOUT CLRNC DUE TO AN ALTIMETER FAILURE.

Narrative: I WAS FLYING BONANZA, IFR EQUIPPED, BUT UNDER VFR ON A XCOUNTRY FLT, WITHOUT A FLT PLAN, FROM APA TO 1V5. MY INTENTION WAS TO USE A RTE BENEATH THE DEN CLASS B AIRSPACE ACCORDING TO THE APPROVED AND CURRENT SECTIONAL CHART. THE RTE WAS TO BE AT A SEGMENT ON THE W SIDE OF THE CLASS B AND AT 7500 FT MSL. THE FLOOR IN THE AREA IS 8000 FT MSL. I DEPARTED BOULDER INTENDING TO RETURN BY THE SAME RTE AS EARLIER. SENSING THAT DEN. APCH WAS BUSY I DID NOT CALL FOR FLT FOLLOWING. I SET MY ALTIMETER TO THE BOULDER FIELD ELEVATION AND NOTICED NO PROBS WITH EITHER THE SETTING KNOB OR THE ALTIMETER ITSELF. INFLT ON THE RETURN, I HAD AN UPDATE FROM APA ATIS. WHEN RESETTING THE ALTIMETER I NOTICED THAT THE KOHLSMAN KNOB WAS EXTREMELY STIFF AND BECAME COMPLETELY BOUND UP. I DISCONTINUED TRYING TO SET IT IN FAVOR OF FLYING THE ACFT. ON FINAL AT APA ABOUT XA45 MDT I WAS REQUESTED BY APA TWR TO CALL APCH BY TELEPHONE. I DID AND EXPLAINED THE MALFUNCTION. AT NO TIME DID ANY INSTS INDICATE I WAS IN THE CLASS B AIRSPACE, NOT DID I BELIEVE I WAS IN THE CLASS B AIRSPACE. MY XPONDER WAS ALSO ON AND FUNCTIONING ON BOTH FLTS. SINCE THIS EVENT I HAD THE ALTIMETER CHKED AND REPLACED. THIS WAS THE FIRST INDICATION OF ANY PROB AND AFTER DISCOVERY I LANDED IMMEDIATELY AND DID NOT FLY AGAIN UNTIL IT WAS REPAIRED.

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.