Amateur/Home Built/Experimental
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Engineer; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 20; Flight Crew Total 13500; Flight Crew Type 300
Communication Breakdown; Other / Unknown
Conflict NMAC; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Took Evasive Action; Flight Crew Became Reoriented
Human Factors
I was waiting for takeoff from RWY 27. Aircraft Y called in from north of the airport with the stated intention of crossing the airport midfield to enter a left downwind for RWY 27. Someone on the radio stated that there were two aircraft ahead of him; presumably for takeoff. The pilot of Aircraft Y stated on the radio that they would have time to take off because he was slow and would extend his downwind. From my perspective it appeared that the two airplanes waiting for takeoff were still in the run up area.I checked that final was clear; announced my takeoff intentions; and commenced my roll. At that point the Aircraft Y pilot stated that he was turning base. Then the pilot made some snarky comment and announced his intention to go around. I don't know how close we came because I didn't see him until I was departing on my crosswind leg to the south. When I finally spotted him he was bizarrely circling around midfield. Apparently he had cut his base leg extremely short instead of following the standard pattern procedure; which required a longer downwind leg for noise abatement considerations. This procedure was well circulated among the users of the airport; and is depicted in Title 19; the document which governs airport operations.I don't know why he did that after stating his intention to go further downwind; but it caught me by surprise. I just didn't see him anywhere in the air; and he certainly wasn't on final or a normal base leg. This pilot has a history of weirdness in traffic patterns; so the next time I hear him on the radio I will be even more alert than I am in the traffic area.
Experimental pilot reported an airborne conflict with a small aircraft at CXP when the arriving pilot apparently did not follow his CTAF stated intentions to enter the pattern.