Narrative:

Aircraft X requested a westbound departure and was cleared for takeoff. There were three other aircraft in the south downwind: aircraft Y (pattern work); followed by aircraft Z; inbound from the west; and aircraft a who was entering the pattern and departed ahead of aircraft X. On departure; aircraft X turned a crosswind southbound instead of going westbound; which put him in the path of aircraft Z. At first I thought I confused aircraft Z and aircraft X; but I issued traffic immediately to aircraft Z and watched as he had to maneuver to avoid aircraft X. I then issued traffic to aircraft a as he was also going to be in conflict. Aircraft X was not answering at first; and then when he responded; I asked his intentions; thinking that I misunderstood him. He decided that he would go to mzb VORTAC before turning north; which is contrary to what 99.99% of our pilots do. Though the aircraft is based here; I do not believe the pilot is based here; and he does not know the airspace and procedures. I thought he was going westbound; and I could not have anticipated his moves. I issue traffic normally on this situation; (westbound departures with inbounds from the west) and was in that process when he turned into the traffic. Aircraft Z pilot said 'that was pretty close.' then on the phone later; he described aircraft X as 'that guy who tried to crash into me.'this pilot needs to be found and educated.

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Original NASA ASRS Text

Title: MYF Tower controller describes a NMAC caused by a pilot not familiar with the local procedures while airborne.

Narrative: Aircraft X requested a westbound departure and was cleared for takeoff. There were three other aircraft in the south downwind: Aircraft Y (pattern work); followed by Aircraft Z; inbound from the west; and Aircraft A who was entering the pattern and departed ahead of Aircraft X. On departure; Aircraft X turned a crosswind southbound instead of going westbound; which put him in the path of Aircraft Z. At first I thought I confused Aircraft Z and Aircraft X; but I issued traffic immediately to Aircraft Z and watched as he had to maneuver to avoid Aircraft X. I then issued traffic to Aircraft A as he was also going to be in conflict. Aircraft X was not answering at first; and then when he responded; I asked his intentions; thinking that I misunderstood him. He decided that he would go to MZB VORTAC before turning north; which is contrary to what 99.99% of our pilots do. Though the aircraft is based here; I do not believe the pilot is based here; and he does not know the airspace and procedures. I thought he was going westbound; and I could not have anticipated his moves. I issue traffic normally on this situation; (westbound departures with inbounds from the west) and was in that process when he turned into the traffic. Aircraft Z pilot said 'That was pretty close.' Then on the phone later; he described Aircraft X as 'That guy who tried to crash into me.'This pilot needs to be found and educated.

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.