PLT OF PA28-180 DSNDING FOR A DOWNWIND PATTERN ENTRY FINDS HIMSELF AT PATTERN ALT AND ABEAM AN ACFT ON DOWNWIND WHO QUERIES HIM AS TO HIS INTENTIONS.

Narrative

I WAS APPROACHING AN UNCONTROLLED ARPT (PETALUMA; CA.) AT 1700 FT FROM THE S FOR LNDG. THE ARPT IS 87 FT MSL AND THE PATTERN IS 1087 FT MSL. I WAS GOING TO OVERHEAD THE AIRPORT AND THEN TURN L AND DSND INTO A 45 FOR A R DOWNWIND TO RWY 29. THERE ARE HILLS N OF THE FIELD RISING TO ABOUT 1700-1800 FT. I CALLED ON THE CTAF AND OBSERVED PLANES IN THE PATTERN. AS I WAS CROSSING WHAT WOULD HAVE BEEN A WIDE (BUT ACCEPTABLE) DOWNWIND; I HEARD A BEECH DUCHESS YELLING ABOUT A CHEROKEE'S INTENTIONS. I QUICKLY LOOKED AND SAW HIM DIRECTLY OUT MY L SIDE WINDOW. I LOOKED AT MY ALTIMETER AND WAS AMAZED TO SEE I WAS JUST OVER 1000 FT. I HAD JUST FLOWN DIRECTLY THROUGH THE DOWNWIND LEG OF THE PATTERN. THERE WAS SOME MORE YELLING ON THE RADIO AND BY THIS TIME I WAS COMPLETELY DEVASTATED BY MY STUPIDITY. I TRY VERY HARD TO BE A SAFE PLT AND COULD NOT BELIEVE I HAD JUST DONE THIS. I AM ALSO VERY FAMILIAR WITH THIS ARPT. I THINK THERE WERE SEVERAL FACTORS LEADING UP TO THIS. I HAVE BEEN VERY CONCERNED ABOUT MY JOB AND EVENTS HAD TRANSPIRED EARLIER THAT DAY THAT WERE STILL WEIGHING HEAVILY ON MY MIND. I ALSO HAD THE ALTERNATOR TRIP OFF-LINE WHEN I TURNED ON THE LNDG LIGHT; COMING UP OVER THE FIELD. I WAS THINKING ABOUT THIS AND DECIDING WHETHER TO RESET IT NOW (AND LOSE COM CAPABILITY) OR WAIT TILL I WAS ON THE GROUND. I ALSO THINK A CONTRIBUTING FACTOR IS THAT THE WINDSCREEN IS 'FULL OF MOUNTAINS' PRIOR TO MAKING THE TURN; SO THE HORIZON IS LOST. MY LACK OF RECENT FLT EXPERIENCE DIDN'T HELP EITHER.