Narrative:

I lined up on the runway centerline and turned on the pitot heat stall warning heat, propeller heat, and turned the transponder to altitude. On the takeoff roll, all the engine instruments were in the green for both engines. The airspeed was increasing and I rotated a few KTS above VMC. After climbing about 1000 ft, the pilot's airspeed went to zero. The vsi showed a climb of 500 FPM and the altimeter was showing a climb also. I thought I had a pitot problem and waited to see if the pitot heat would fix the problem. I clicked the pitot heat off and on to see if it was working and it showed an increase in amperage, when turned on, on the alternator ammeter. I also checked the copilot's airspeed indicator and it was functioning ok. I didn't inform ATC right away because I had the copilot airspeed indicator and thought I'd give the pitot heat a chance to work longer. When I was VMC above the clouds, I reached my assigned altitude of 12000 ft and began to level off. As I leveled off, the vsi and altimeter still showed a climb. I pointed the nose down and the vsi and altimeter still showed a climb. At this point I let ATC know I had a problem and they also queried me as to what altitude I was climbing to. I then referenced the copilot's altimeter and vsi. I was then at 13700 ft and in a slow descent. Using the copilot's vsi and altimeter I descended back to 12000 ft. When I leveled at 12000 ft the pilot's airspeed indicator began working, but showed 10 KTS less than the copilot's airspeed indicator. The pilot's vsi then began to show a 500 FPM descent until the altimeter reached 11800 ft. Also, at one point during the climb, before the static problem was discovered, the pilot's airspeed indicator increased to 90 KIAS before dropping back to zero. I soon discovered the alternate static source valve had been turned to 1/2 open. When I closed the alternate static source valve the pilot's altimeter jumped to 12000 ft and the airspeed indicator's speeds matched. Some time during the climb my left leg must have bumped the alternate static source to 1/2 open and that is when the pilot's airspeed indicator dropped to zero and the vsi indicated the cabin climb rate. To prevent the recurrence, I would xchk the copilot's pitot static instruments sooner. I would also let ATC know about the problem I thought I had sooner than I did.

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Original NASA ASRS Text

Title: PLT OF A TWIN ENG RECIPROCAL ACFT TURNS ON PITOT HEAT, STALL WARNING HEAT AND PROP HEAT PRIOR TO TKOF. AT ABOUT 1000 FT THE AIRSPD GOES TO ZERO BUT THE VSI AND ALTIMETER SHOW A CLB. TRYING TO SOLVE THE PROB, RPTR LEVELS OFF AT ASSIGNED ALT, HE IS CONTACTED BY ATC, AND QUERIED ABOUT HIS ALT. HE IS AT 13700 FT VERSUS 12000 FT. HE DISCOVERED THE ALTERNATE STATIC SOURCE HAD BEEN TURNED TO HALF OPEN. PROB SOLVED.

Narrative: I LINED UP ON THE RWY CTRLINE AND TURNED ON THE PITOT HEAT STALL WARNING HEAT, PROP HEAT, AND TURNED THE XPONDER TO ALT. ON THE TKOF ROLL, ALL THE ENG INSTS WERE IN THE GREEN FOR BOTH ENGS. THE AIRSPD WAS INCREASING AND I ROTATED A FEW KTS ABOVE VMC. AFTER CLBING ABOUT 1000 FT, THE PLT'S AIRSPD WENT TO ZERO. THE VSI SHOWED A CLB OF 500 FPM AND THE ALTIMETER WAS SHOWING A CLB ALSO. I THOUGHT I HAD A PITOT PROB AND WAITED TO SEE IF THE PITOT HEAT WOULD FIX THE PROB. I CLICKED THE PITOT HEAT OFF AND ON TO SEE IF IT WAS WORKING AND IT SHOWED AN INCREASE IN AMPERAGE, WHEN TURNED ON, ON THE ALTERNATOR AMMETER. I ALSO CHKED THE COPLT'S AIRSPD INDICATOR AND IT WAS FUNCTIONING OK. I DIDN'T INFORM ATC RIGHT AWAY BECAUSE I HAD THE COPLT AIRSPD INDICATOR AND THOUGHT I'D GIVE THE PITOT HEAT A CHANCE TO WORK LONGER. WHEN I WAS VMC ABOVE THE CLOUDS, I REACHED MY ASSIGNED ALT OF 12000 FT AND BEGAN TO LEVEL OFF. AS I LEVELED OFF, THE VSI AND ALTIMETER STILL SHOWED A CLB. I POINTED THE NOSE DOWN AND THE VSI AND ALTIMETER STILL SHOWED A CLB. AT THIS POINT I LET ATC KNOW I HAD A PROB AND THEY ALSO QUERIED ME AS TO WHAT ALT I WAS CLBING TO. I THEN REFED THE COPLT'S ALTIMETER AND VSI. I WAS THEN AT 13700 FT AND IN A SLOW DSCNT. USING THE COPLT'S VSI AND ALTIMETER I DSNDED BACK TO 12000 FT. WHEN I LEVELED AT 12000 FT THE PLT'S AIRSPD INDICATOR BEGAN WORKING, BUT SHOWED 10 KTS LESS THAN THE COPLT'S AIRSPD INDICATOR. THE PLT'S VSI THEN BEGAN TO SHOW A 500 FPM DSCNT UNTIL THE ALTIMETER REACHED 11800 FT. ALSO, AT ONE POINT DURING THE CLB, BEFORE THE STATIC PROB WAS DISCOVERED, THE PLT'S AIRSPD INDICATOR INCREASED TO 90 KIAS BEFORE DROPPING BACK TO ZERO. I SOON DISCOVERED THE ALTERNATE STATIC SOURCE VALVE HAD BEEN TURNED TO 1/2 OPEN. WHEN I CLOSED THE ALTERNATE STATIC SOURCE VALVE THE PLT'S ALTIMETER JUMPED TO 12000 FT AND THE AIRSPD INDICATOR'S SPDS MATCHED. SOME TIME DURING THE CLB MY L LEG MUST HAVE BUMPED THE ALTERNATE STATIC SOURCE TO 1/2 OPEN AND THAT IS WHEN THE PLT'S AIRSPD INDICATOR DROPPED TO ZERO AND THE VSI INDICATED THE CABIN CLB RATE. TO PREVENT THE RECURRENCE, I WOULD XCHK THE COPLT'S PITOT STATIC INSTS SOONER. I WOULD ALSO LET ATC KNOW ABOUT THE PROB I THOUGHT I HAD SOONER THAN I DID.

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.