Narrative:

While distraction by several mechanical problems, and with icing forecast at our altitude south of our position, I elected to make a precautionary landing at prb, rather than air file an IFR flight plan and continue on to our destination. I asked for and received a pop-up IFR clearance to the field and was instructed to fly direct prb in VFR. The undercast tops were approximately 5500 ft MSL. We were sebound in VFR at 9500 ft. I descended to approximately 7000 ft and was direct prb VOR. In my anxiety to troubleshoot the mechanical problems, including a faulty fuel gauge and engine surging, I misread the approach plate for the runway 19 VOR DME approach and lost situational awareness. Arriving at the VOR at 6500 ft, I asked for and received the approach clearance, which would have necessitated a 180 degree turn to fly outbound on the inbound radial. I should have told the controller at ZOA that I declined the clearance, but, distraction as I was, I intercepted the 192 degree radial and flew outbound on that heading away from the airport. When asked by ZOA where I thought I was going, I told them of the engine troubles, and received vectors to the VOR from my position. There was no danger. I never descended below 5500 ft. The MEA on the inbound leg is 4000 ft. Descending into the clouds, the engine started to surge and I canceled the approach. After climbing into VFR conditions, I asked for vectors to the nearest VFR airport, king city, ca. I got the engine smoothed out and proceeded without incident to the field, although the elevator trim remained jammed in the nose down position. After arrival, it was determined that the surging was probably caused by changes in oil pressure, in turn caused by a faulty fitting in the oil system of the newly overhauled engine.

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Original NASA ASRS Text

Title: M20P PLT LOST SITUATIONAL AWARENESS WHEN BEGINNING APCH AT PRB.

Narrative: WHILE DISTR BY SEVERAL MECHANICAL PROBS, AND WITH ICING FORECAST AT OUR ALT S OF OUR POS, I ELECTED TO MAKE A PRECAUTIONARY LNDG AT PRB, RATHER THAN AIR FILE AN IFR FLT PLAN AND CONTINUE ON TO OUR DEST. I ASKED FOR AND RECEIVED A POP-UP IFR CLRNC TO THE FIELD AND WAS INSTRUCTED TO FLY DIRECT PRB IN VFR. THE UNDERCAST TOPS WERE APPROX 5500 FT MSL. WE WERE SEBOUND IN VFR AT 9500 FT. I DSNDED TO APPROX 7000 FT AND WAS DIRECT PRB VOR. IN MY ANXIETY TO TROUBLESHOOT THE MECHANICAL PROBS, INCLUDING A FAULTY FUEL GAUGE AND ENG SURGING, I MISREAD THE APCH PLATE FOR THE RWY 19 VOR DME APCH AND LOST SITUATIONAL AWARENESS. ARRIVING AT THE VOR AT 6500 FT, I ASKED FOR AND RECEIVED THE APCH CLRNC, WHICH WOULD HAVE NECESSITATED A 180 DEG TURN TO FLY OUTBOUND ON THE INBOUND RADIAL. I SHOULD HAVE TOLD THE CTLR AT ZOA THAT I DECLINED THE CLRNC, BUT, DISTR AS I WAS, I INTERCEPTED THE 192 DEG RADIAL AND FLEW OUTBOUND ON THAT HDG AWAY FROM THE ARPT. WHEN ASKED BY ZOA WHERE I THOUGHT I WAS GOING, I TOLD THEM OF THE ENG TROUBLES, AND RECEIVED VECTORS TO THE VOR FROM MY POS. THERE WAS NO DANGER. I NEVER DSNDED BELOW 5500 FT. THE MEA ON THE INBOUND LEG IS 4000 FT. DSNDING INTO THE CLOUDS, THE ENG STARTED TO SURGE AND I CANCELED THE APCH. AFTER CLBING INTO VFR CONDITIONS, I ASKED FOR VECTORS TO THE NEAREST VFR ARPT, KING CITY, CA. I GOT THE ENG SMOOTHED OUT AND PROCEEDED WITHOUT INCIDENT TO THE FIELD, ALTHOUGH THE ELEVATOR TRIM REMAINED JAMMED IN THE NOSE DOWN POS. AFTER ARR, IT WAS DETERMINED THAT THE SURGING WAS PROBABLY CAUSED BY CHANGES IN OIL PRESSURE, IN TURN CAUSED BY A FAULTY FITTING IN THE OIL SYS OF THE NEWLY OVERHAULED ENG.

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.