Narrative:

2ND altitude incursion in 4 days. On this day the autoplt was showing 100 ft too high. ATC said he was showing we were at 7500 ft. Altimeter was only off the setting of .3 (30.06). I had maintenance take a look upon my return. ATC showed me at 7500 ft 2 mins after I reset the altimeter, and descended 100 ft. ATC has said nothing on both occasions, however, they are used to me, and me of them. I am concerned with my mental errors this week and I wonder if they are surprised at me. We have worked together during the hurricane season with no problems. Contributing factors: maybe the complacency of excellent VFR WX, combined with changing from 2 pilot crews, to single pilot operations. Both sits are similar, and I feel it's more my mental error, than mechanical. Corrective actions: when switching from 2 pilot to single pilot -- now, instead of just mentally 'noting' the altitude limit, I have started using a post-it note each time a change is made, concerning altitude changes. Also, I have told passenger each and every time about the 'critical phase of flight.' sometimes I used to do in the past and apparently fell short a few times. Also, a pilot memo was posted concerning my errors, and asked if anyone has had similar problems. Suggestions from the pilot crews are now being accepted. An 'altitude alert box' would be nice in a single or multi-engine operation, however, owners see the money side of its implementation.

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Original NASA ASRS Text

Title: C208 PLT HAD A MODE C READOUT THAT DIFFERED FROM THE ACFT ALTIMETER.

Narrative: 2ND ALT INCURSION IN 4 DAYS. ON THIS DAY THE AUTOPLT WAS SHOWING 100 FT TOO HIGH. ATC SAID HE WAS SHOWING WE WERE AT 7500 FT. ALTIMETER WAS ONLY OFF THE SETTING OF .3 (30.06). I HAD MAINT TAKE A LOOK UPON MY RETURN. ATC SHOWED ME AT 7500 FT 2 MINS AFTER I RESET THE ALTIMETER, AND DSNDED 100 FT. ATC HAS SAID NOTHING ON BOTH OCCASIONS, HOWEVER, THEY ARE USED TO ME, AND ME OF THEM. I AM CONCERNED WITH MY MENTAL ERRORS THIS WEEK AND I WONDER IF THEY ARE SURPRISED AT ME. WE HAVE WORKED TOGETHER DURING THE HURRICANE SEASON WITH NO PROBS. CONTRIBUTING FACTORS: MAYBE THE COMPLACENCY OF EXCELLENT VFR WX, COMBINED WITH CHANGING FROM 2 PLT CREWS, TO SINGLE PLT OPS. BOTH SITS ARE SIMILAR, AND I FEEL IT'S MORE MY MENTAL ERROR, THAN MECHANICAL. CORRECTIVE ACTIONS: WHEN SWITCHING FROM 2 PLT TO SINGLE PLT -- NOW, INSTEAD OF JUST MENTALLY 'NOTING' THE ALT LIMIT, I HAVE STARTED USING A POST-IT NOTE EACH TIME A CHANGE IS MADE, CONCERNING ALT CHANGES. ALSO, I HAVE TOLD PAX EACH AND EVERY TIME ABOUT THE 'CRITICAL PHASE OF FLT.' SOMETIMES I USED TO DO IN THE PAST AND APPARENTLY FELL SHORT A FEW TIMES. ALSO, A PLT MEMO WAS POSTED CONCERNING MY ERRORS, AND ASKED IF ANYONE HAS HAD SIMILAR PROBS. SUGGESTIONS FROM THE PLT CREWS ARE NOW BEING ACCEPTED. AN 'ALT ALERT BOX' WOULD BE NICE IN A SINGLE OR MULTI-ENG OP, HOWEVER, OWNERS SEE THE MONEY SIDE OF ITS IMPLEMENTATION.

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.