Narrative:

My aircraft 5 miles northeast of the paso robles airport (prb) inbound for landing and monitoring unicom traffic. Two other aircraft reported inbound. One aircraft 10 miles east of prb; one aircraft 5 miles north west of prb. Aircraft east advised maneuvering to allow me to enter downwind left traffic runway 19. I made several unicom traffic announcements and reported inbound on the 45 for runway 19; left traffic; full stop. No other traffic was observed and no further radio traffic heard. I then advised my downwind abeam runway 19 position. No other traffic was in the pattern that we observed. When about to begin my left turn to base with a descent; my right seat passenger advised 'stop the descent; aircraft going underneath me from right to left (westbound). I stopped the descent and observed a cherokee at around 800 ft. On a tight base to final turn; landing on 19. The other pilot made a radio position call when on short final; giving his north number. I extended my downwind at that time and called the pilot asking if he was aware that he almost caused an incident? The pilot did not answer my call. The pilot exited the runway and taxied to a permanent ramp tie down. I picked up my car and drove to the ramp where this plane had taxied. The pilot had left the area. We were within 500 ft of a mid-air collision on downwind due to the gross negligence and reckless disregard for other aircraft in the pattern by this pilot. When speaking with another pilot on the ground; he said he heard this pilot make a weak and broken radio announcement when he took off; apparently without regard for other area traffic.

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Original NASA ASRS Text

Title: A pilot approaching a non-towered airport is surprised by the close proximity of another aircraft that had not identified his location and seemingly aware of conflicting traffic.

Narrative: My aircraft 5 miles northeast of the Paso Robles Airport (PRB) inbound for landing and monitoring UNICOM traffic. Two other aircraft reported inbound. One aircraft 10 miles east of PRB; one aircraft 5 miles north west of PRB. Aircraft east advised maneuvering to allow me to enter downwind left traffic runway 19. I made several UNICOM traffic announcements and reported inbound on the 45 for runway 19; left traffic; full stop. No other traffic was observed and no further radio traffic heard. I then advised my downwind abeam runway 19 position. No other traffic was in the pattern that we observed. When about to begin my left turn to base with a descent; my right seat passenger advised 'stop the descent; aircraft going underneath me from right to left (westbound). I stopped the descent and observed a Cherokee at around 800 ft. on a tight base to final turn; landing on 19. The other pilot made a radio position call when on short final; giving his N number. I extended my downwind at that time and called the pilot asking if he was aware that he almost caused an incident? The pilot did not answer my call. The pilot exited the runway and taxied to a permanent ramp tie down. I picked up my car and drove to the ramp where this plane had taxied. The pilot had left the area. We were within 500 ft of a mid-air collision on downwind due to the gross negligence and reckless disregard for other aircraft in the pattern by this pilot. When speaking with another pilot on the ground; he said he heard this pilot make a weak and broken radio announcement when he took off; apparently without regard for other area traffic.

Data retrieved from NASA's ASRS site 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.