Narrative:

I was in level flight under the ZZZ arsa at 1950 ft MSL. The floor of the arsa is 2000 ft where I was. The reason I am sending this in, is that sometimes the ZZZ radar will have me up to 100 ft off the altitude that my altimeter reads. So, by their radar, I could have been between 1850 ft and 2050 ft MSL. The latter would put me in the arsa by 50 ft. My altimeter was set correctly at the time. Callback conversation with reporter revealed the following: reporter states that error in altitude reading between the aircraft and ATC has not been confirmed to be an aircraft altimeter error. Reporter states that error must be in mode C. Reporter was en route to hospital with patient on interfacility transfer.

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Original NASA ASRS Text

Title: UNAUTH PENETRATION OF AIRSPACE. PROX OF ARSA.

Narrative: I WAS IN LEVEL FLT UNDER THE ZZZ ARSA AT 1950 FT MSL. THE FLOOR OF THE ARSA IS 2000 FT WHERE I WAS. THE REASON I AM SENDING THIS IN, IS THAT SOMETIMES THE ZZZ RADAR WILL HAVE ME UP TO 100 FT OFF THE ALT THAT MY ALTIMETER READS. SO, BY THEIR RADAR, I COULD HAVE BEEN BTWN 1850 FT AND 2050 FT MSL. THE LATTER WOULD PUT ME IN THE ARSA BY 50 FT. MY ALTIMETER WAS SET CORRECTLY AT THE TIME. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: RPTR STATES THAT ERROR IN ALT READING BTWN THE ACFT AND ATC HAS NOT BEEN CONFIRMED TO BE AN ACFT ALTIMETER ERROR. RPTR STATES THAT ERROR MUST BE IN MODE C. RPTR WAS ENRTE TO HOSPITAL WITH PATIENT ON INTERFAC TRANSFER.

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.