Narrative:

A C182 was handed off to me from richmond sector 7 miles northwest of oak for a transition to hwd. I was informed by the C1-1 coordinator that the pilot was very unfamiliar and was on a 130 heading at 2;500 ft. I instructed the pilot to continue on his heading and 'begin a VFR descent at or below 1;400.' the pilot read this back correctly. A few minutes later; I observed a P180 on a 9 mile final for runway 27R on the visual approach. I estimated that on the present heading the C182 would pass behind and below the P180 at about a 5 mile final. When the C182 was 7 miles from hwd I pointed out the airport to him and he called the airport in sight. I called hwd; and informed them that the C182 was very unfamiliar and had the airport in sight. I terminated radar services on the C182 and instructed him to contact hwd tower. At this point the C182 was at about 2;100 ft and was tracking to pass behind the P180. About 1 minute later I noticed that the C182 kept tracking towards the P180 and was not descending. I attempted to call hwd twice; when I got them I asked what they planned to do about the conflict involving the C182 and the P180; they asked for a 360 in my airspace; I approved any operation to keep the C182 north of the runway 27R final. My next call was my first transmission to the P180; I called traffic; and he said he was looking. There was another aircraft departing hwd to the north and I chose not to issue traffic to this target as I considered it no-factor. As the C182 and the P180 targets continued to merge; I told the P180 to stop his descent if he didn't have traffic in sight. The P180 and the C182 targets appeared to merge and the P180 had to climb to avoid. The P180 described the traffic as 'close;' he indicated that he wasn't aware that there were two targets and he only saw the C182 when they were close. I wasn't aware that the P180 had been given that traffic by approach control. The P180 climbed to about 2;300 ft and was unable to land due to his altitude. I instructed the P180 to go around and kept him on my frequency in a right turn for runway 27R. I coordinated this go-around with local control 1 and grove sector. The P180 landed without incident. I could have ensured the descent was completed before I transferred the C182 to hwd. I could have chosen to talk to the P180 first and given him a climb in time to safely avoid traffic. I could have turned the C182 on a heading 090 as a guarantee to pass behind the P180. I don't know when the C182 actually switched to hwd frequency or what instructions he was given; but this could have been a factor. It's normal operation for hwd tower to miss IFR aircraft on approaches to runways.

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Original NASA ASRS Text

Title: OAK Local Controller described a conflict between a VFR arrival to HWD and an aircraft inbound to OAK Runway 27R on a visual approach; the reporter listing several actions which would have prevented the event.

Narrative: A C182 was handed off to me from Richmond Sector 7 miles northwest of OAK for a transition to HWD. I was informed by the C1-1 Coordinator that the pilot was very unfamiliar and was on a 130 heading at 2;500 FT. I instructed the pilot to continue on his heading and 'begin a VFR descent at or below 1;400.' The pilot read this back correctly. A few minutes later; I observed a P180 on a 9 mile final for Runway 27R on the Visual Approach. I estimated that on the present heading the C182 would pass behind and below the P180 at about a 5 mile final. When the C182 was 7 miles from HWD I pointed out the airport to him and he called the airport in sight. I called HWD; and informed them that the C182 was very unfamiliar and had the airport in sight. I terminated radar services on the C182 and instructed him to contact HWD Tower. At this point the C182 was at about 2;100 FT and was tracking to pass behind the P180. About 1 minute later I noticed that the C182 kept tracking towards the P180 and was not descending. I attempted to call HWD twice; when I got them I asked what they planned to do about the conflict involving the C182 and the P180; they asked for a 360 in my airspace; I approved any operation to keep the C182 north of the Runway 27R final. My next call was my first transmission to the P180; I called traffic; and he said he was looking. There was another aircraft departing HWD to the north and I chose not to issue traffic to this target as I considered it no-factor. As the C182 and the P180 targets continued to merge; I told the P180 to stop his descent if he didn't have traffic in sight. The P180 and the C182 targets appeared to merge and the P180 had to climb to avoid. The P180 described the traffic as 'Close;' he indicated that he wasn't aware that there were two targets and he only saw the C182 when they were close. I wasn't aware that the P180 had been given that traffic by Approach Control. The P180 climbed to about 2;300 FT and was unable to land due to his altitude. I instructed the P180 to go around and kept him on my frequency in a right turn for Runway 27R. I coordinated this go-around with Local Control 1 and Grove Sector. The P180 landed without incident. I could have ensured the descent was completed before I transferred the C182 to HWD. I could have chosen to talk to the P180 first and given him a climb in time to safely avoid traffic. I could have turned the C182 on a heading 090 as a guarantee to pass behind the P180. I don't know when the C182 actually switched to HWD frequency or what instructions he was given; but this could have been a factor. It's normal operation for HWD Tower to miss IFR aircraft on approaches to Runways.

Data retrieved from NASA's ASRS site as of April 2012 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.