HWD Tower controllers reported confusion and failure to clearly explain intentions of conflicting traffic; resulted in a pilot reported NMAC.
Synopsis
HWD Tower controllers reported confusion and failure to clearly explain intentions of conflicting traffic; resulted in a pilot reported NMAC.
Narrative
I was manning the Local Control position when Aircraft X began flying north of the field. Aircraft Y departed the runways on a Left 270 departure northbound. I exchanged traffic early and had Aircraft Y keep the 3 Crosses off their right for the Aircraft X traffic on the other side (the '3 Crosses' is a VFR reporting point 2.5mi North of the field). They obliged; but then reported the Aircraft X in sight shortly afterwards. Aircraft X also reported Aircraft Y in sight. I allowed Aircraft Y to resume their own navigation since both aircraft had each other in sight. Less than a minute later; Aircraft X broadcasted that they had a near-miss with Aircraft Y. When prompted; Aircraft Y stated that they had not expected the Aircraft X to turn back around towards their aircraft; but had the Aircraft X in sight the whole time and also avoided them. Later; the Aircraft X pilot called the tower to state that they had lost sight of Aircraft Y while making a Northeast-bound turn in their orbit; and when turning back around Northwest-bound; they encountered Aircraft Y at a distance of 50 ft vertically and 150ft laterally. They said that Aircraft Y had cut it in too close passing behind them.Recommendation: HWD is a Delta airspace and frequently manages multiple aircraft in VFR flight in close proximity. Since both pilots in this event were operating VFR and had declared each other in sight; it stands to reason that ATC expected them to see and avoid one another. That being said; in the future; I could initially prompt Aircraft Y for his destination (prior departure) and work on turning him more in that direction to begin with; so that he possibly would not have made such a direct turn in the Easterly direction. Additionally; the Aircraft X was in orbit; so maybe I could have expected them to lose sight of Aircraft Y.
Second reporter narrative
Aircraft X; was orbiting 2 miles north of the airport. Aircraft Y was given a left 270 departure northbound towards Aircraft X. Once Aircraft Y turned northbound; LCL1 (Local Control) gave Aircraft Y the Aircraft X traffic and positive control to keep a local reporting point off their right. Aircraft Y pilot reported Aircraft X in sight. Aircraft X was also given traffic; a positive control instruction to stay on the other side of the reporting point. Aircraft X also reported Aircraft Y in sight. Once Aircraft Y appeared to be past Aircraft X (was on a south heading) a 'resume own navigation' instruction was given. Aircraft Y proceeded to turn on their desired course which was towards the northeast behind Aircraft X. At the same time Aircraft X turned back the north/northeast with Aircraft Y passing near them. Aircraft X reported the 'near miss'. Aircraft Y reported that they might have been confused on what the Aircraft X was doing; but had them in sight the whole time.Recommendation: LCL1 exchanged traffic in a timely manner and gave positive instructions. However; the intentions of Aircraft Y could have been asked to get a better picture of their desired route. Aircraft Y was turned away from their route to pass in between Aircraft X and Oakland airspace. With rising terrain; being restricted below the Charlie airspace shelf; and staying out of the lateral Oakland airspace; the pilot turned on course as soon as they could. The 'resume own navigation' also could have been delayed just a moment longer since it was known that Aircraft X could swing back around.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.