Narrative:

After taking the position a few minutes prior; an aircraft departed ZZZ airport on an IFR tag; and to my knowledge no release given. It turned out to be a citation departing VFR; who happened to be squawking the code of an IFR in the system. My attention intially is given to fixing this; as the aircraft was moving fairly fast towards another approach control's airspace about 15 miles away. Then a routine IFR departure off of ZZZ1; aircraft X destined to ZZZ2 checks in. I climb aircraft X to 3;000 (which is a standard altitude for the destined airport); and leave the aircraft on the tower assigned heading to outclimb a VFR aircraft to its right. When I see that aircraft X has outclimbed the VFR I turn aircraft X northbound towards ZZZ2. After the turn northbound I notice that the VFR aircraft is continuing to climb; I then issue traffic to aircraft X and an instruction to climb. No readback is heard and I issue a climb 2 more times. Aircraft X later states that I was stepped on at least twice. At the time I had a mix of aircraft on both the 133.75 and 126.1 frequencies. At the time that aircraft X was in close proximity to the VFR aircraft climbing out; aircraft Z departs IFR from ZZZ1. On check in I climb aircraft Z to 4;000; which is the appropriate SOP altitude for the route; leaving the aircraft on tower assigned heading. When I turn aircraft Z northbound there was the same VFR that was issue for aircraft X climbing off to the right. At the time there were a few hundred feet separation; but the VFR was still in a climb and northbound turn was poorly planned. I instruct aircraft Z to climb to 4;500 multiple times in an attempt to gain altitude. There was no response heard to my instruction. Aircraft Z shortly after states that they climbed for an RA. Throughout this happening; there were multiple calls from what turns out to be aircraft Y. At the time of the initial calls the aircraft was squawking 1200 and not yet receiving any radar services. At one point I requested the aircraft Y to 'stand-by' as I tried to resolve all of my current traffic workload. Eventually I am able to get the neccesary information from aircraft Y and provide radar services until the aircraft left my airspace. After aircraft Z declared that they responded to an RA; I informed my supervisor. An OM [operations manger] at my facility reviewed the event about 15 minutes after it happend; and did not remark about a near midair collision; acknowledged the frequency congestion; and recommended that I should have issued traffic alerts in both situations. During a performance review of this situation that I had with my supervisor of record yesterday; I was informed that both situations were considered a loss and near midair collision. The supervisor said the pilot declared a near midair collision on frequency; which I did not hear at the time; nor did I hear the phrase 'near mid air collision' during the playback with my supervisor. I did not correctly take into account the performance of all the aircraft involved. Though the two jets did initially outclimb the VFR; they were both capped at a low altitude; combined with the rather good rate of climb of the VFR to lead to the aircraft being too close. Secondly the turn radius of both of the jets put them right in the path of the VFR. Not knowing the type; route of flight or altitude climbing to for the VFR did add an unknown variable to decide when to turn the jets northbound. The planning of actions were poor. Frequency congestion was a partial factor while trying to resolve the situation. Our LOA with ZZZ1 specifies that departures are to be given the departure frequency of 126.1. In the past when we combine sectors we have asked ZZZ1 tower to give a different frequency to departures (133.75) to alleviate congestion; the tower has refused to issue it since the LOA states 126.1. To my knowledge management has been aware of this for over a year. The volume of traffic that arrives and departs ZZZ1 during the summer months definitely warrants class C airspace in my opinion. ZZZ1 in on an island with no land for hundreds of miles to its south and east. Most traffic departs the island going either northbound or westbound; constantly creating this exact situation. If the airspace was class C there would be more tools at the controller's disposal to control the VFR departures to positively separate ifrs and vfrs. There is a designed time based scheduling program used at for ZZZ1 arrivals in the summer that is run by ZZZ3 [center]; yet the airspace of the airport is class D; which can hurt the effectiveness of the program; since vfrs can easily bypass it.

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Original NASA ASRS Text

Title: A90 Controller stated aircraft reported a NMAC while he was vectoring to separate from unknown VFR. Controller stated this is common between these two airports.

Narrative: After taking the position a few minutes prior; an aircraft departed ZZZ airport on an IFR tag; and to my knowledge no release given. It turned out to be a Citation departing VFR; who happened to be squawking the code of an IFR in the system. My attention intially is given to fixing this; as the aircraft was moving fairly fast towards another approach control's airspace about 15 miles away. Then a routine IFR departure off of ZZZ1; Aircraft X destined to ZZZ2 checks in. I climb Aircraft X to 3;000 (which is a standard altitude for the destined airport); and leave the aircraft on the tower assigned heading to outclimb a VFR aircraft to its right. When I see that Aircraft X has outclimbed the VFR I turn Aircraft X northbound towards ZZZ2. After the turn northbound I notice that the VFR aircraft is continuing to climb; I then issue traffic to Aircraft X and an instruction to climb. No readback is heard and I issue a climb 2 more times. Aircraft X later states that I was stepped on at least twice. At the time I had a mix of aircraft on both the 133.75 and 126.1 frequencies. At the time that Aircraft X was in close proximity to the VFR aircraft climbing out; Aircraft Z departs IFR from ZZZ1. On check in I climb Aircraft Z to 4;000; which is the appropriate SOP altitude for the route; leaving the aircraft on tower assigned heading. When I turn Aircraft Z northbound there was the same VFR that was issue for Aircraft X climbing off to the right. At the time there were a few hundred feet separation; but the VFR was still in a climb and northbound turn was poorly planned. I instruct Aircraft Z to climb to 4;500 multiple times in an attempt to gain altitude. There was no response heard to my instruction. Aircraft Z shortly after states that they climbed for an RA. Throughout this happening; there were multiple calls from what turns out to be Aircraft Y. At the time of the initial calls the aircraft was squawking 1200 and not yet receiving any radar services. At one point I requested the Aircraft Y to 'stand-by' as I tried to resolve all of my current traffic workload. Eventually I am able to get the neccesary information from Aircraft Y and provide radar services until the aircraft left my airspace. After Aircraft Z declared that they responded to an RA; I informed my supervisor. An OM [Operations Manger] at my facility reviewed the event about 15 minutes after it happend; and did not remark about a NMAC; acknowledged the frequency congestion; and recommended that I should have issued Traffic Alerts in both situations. During a performance review of this situation that I had with my supervisor of record yesterday; I was informed that both situations were considered a LOSS and NMAC. The supervisor said the pilot declared a NMAC on frequency; which I did not hear at the time; nor did I hear the phrase 'Near mid air Collision' during the playback with my supervisor. I did not correctly take into account the performance of all the aircraft involved. Though the two jets did initially outclimb the VFR; they were both capped at a low altitude; combined with the rather good rate of climb of the VFR to lead to the aircraft being too close. Secondly the turn radius of both of the jets put them right in the path of the VFR. Not knowing the type; route of flight or altitude climbing to for the VFR did add an unknown variable to decide when to turn the jets northbound. The planning of actions were poor. Frequency congestion was a partial factor while trying to resolve the situation. Our LOA with ZZZ1 specifies that departures are to be given the departure frequency of 126.1. In the past when we combine sectors we have asked ZZZ1 tower to give a different frequency to departures (133.75) to alleviate congestion; the tower has refused to issue it since the LOA states 126.1. To my knowledge management has been aware of this for over a year. The volume of traffic that arrives and departs ZZZ1 during the summer months definitely warrants CLASS C airspace in my opinion. ZZZ1 in on an island with no land for hundreds of miles to its south and east. Most traffic departs the island going either northbound or westbound; constantly creating this exact situation. If the airspace was CLASS C there would be more tools at the controller's disposal to control the VFR departures to positively separate IFRs and VFRs. There is a designed time based scheduling program used at for ZZZ1 arrivals in the summer that is run by ZZZ3 [Center]; yet the airspace of the airport is Class D; which can hurt the effectiveness of the program; since VFRs can easily bypass it.

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.