Narrative:

I departed tvl airport on jan/mon/07 at approximately XA20 local. During the climb out on the richy 5 SID; I was in radio contact with ZOA but was not in radar contact. I was listening to ZOA talk with a PA28 that was northwest of the swr VOR at 12500 ft heading south. I was assigned 12000 ft. I heard ZOA call the PA28 and tell them that I was at 12000 ft. When I heard that from ZOA; I was indicating 11300 ft. I thought that I had missed part of the radio transmission and that he was telling the PA28 I was stopping at 12000 ft. ZOA gave me an advisory for traffic at 1-2 O'clock position and 2 mi at 12500 ft and asked what altitude I was passing. I called that I was passing through 11800 ft when I saw the PA28 at my 2 O'clock position and closing quickly at my altitude. I made a 30 degree turn to the right at the same time the PA28 saw me and made a turn to his right. I would estimate that we passed within about 400-500 ft horizontally. I called that I had the traffic and was maneuvering to the right. I then asked for a current altimeter setting which showed me at 12700 ft; not 12000 ft as I had thought. I told the center operator that I was returning to 12000 ft as directed and apologized over the radio for any inconvenience. I was not asked to contact any ATC authority/authorized. The remainder of my flight was without incident. Callback conversation with reporter revealed the following information: the reporter stated that he simply forgot to set his altimeter. Tvl is a non tower airport; which is where he usually obtains the altimeter setting.

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Original NASA ASRS Text

Title: CE210 PILOT DEPARTS TVL WITHOUT SETTING THE LOCAL ALTIMETER; WHICH CAUSES A CONFLICT WITH VFR TRAFFIC DURING THE DEPARTURE.

Narrative: I DEPARTED TVL ARPT ON JAN/MON/07 AT APPROX XA20 LCL. DURING THE CLBOUT ON THE RICHY 5 SID; I WAS IN RADIO CONTACT WITH ZOA BUT WAS NOT IN RADAR CONTACT. I WAS LISTENING TO ZOA TALK WITH A PA28 THAT WAS NW OF THE SWR VOR AT 12500 FT HEADING S. I WAS ASSIGNED 12000 FT. I HEARD ZOA CALL THE PA28 AND TELL THEM THAT I WAS AT 12000 FT. WHEN I HEARD THAT FROM ZOA; I WAS INDICATING 11300 FT. I THOUGHT THAT I HAD MISSED PART OF THE RADIO XMISSION AND THAT HE WAS TELLING THE PA28 I WAS STOPPING AT 12000 FT. ZOA GAVE ME AN ADVISORY FOR TFC AT 1-2 O'CLOCK POS AND 2 MI AT 12500 FT AND ASKED WHAT ALT I WAS PASSING. I CALLED THAT I WAS PASSING THROUGH 11800 FT WHEN I SAW THE PA28 AT MY 2 O'CLOCK POS AND CLOSING QUICKLY AT MY ALT. I MADE A 30 DEG TURN TO THE R AT THE SAME TIME THE PA28 SAW ME AND MADE A TURN TO HIS R. I WOULD ESTIMATE THAT WE PASSED WITHIN ABOUT 400-500 FT HORIZLY. I CALLED THAT I HAD THE TFC AND WAS MANEUVERING TO THE R. I THEN ASKED FOR A CURRENT ALTIMETER SETTING WHICH SHOWED ME AT 12700 FT; NOT 12000 FT AS I HAD THOUGHT. I TOLD THE CTR OPERATOR THAT I WAS RETURNING TO 12000 FT AS DIRECTED AND APOLOGIZED OVER THE RADIO FOR ANY INCONVENIENCE. I WAS NOT ASKED TO CONTACT ANY ATC AUTH. THE REMAINDER OF MY FLT WAS WITHOUT INCIDENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE REPORTER STATED THAT HE SIMPLY FORGOT TO SET HIS ALTIMETER. TVL IS A NON TOWER AIRPORT; WHICH IS WHERE HE USUALLY OBTAINS THE ALTIMETER SETTING.

Data retrieved from NASA's ASRS site as of January 2009 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.