Narrative:

A fly-in at [airport]. We were briefed that there could be 600 to 1;000 aircraft come to the event; but that almost all will be VFR. We inquired about what if we have lots of IFR arrivals; were there any procedures in place to help and were told that there will minimal IFR pilots. That the [event organization] is generally VFR private pilots.I took [sector] after a thorough briefing and a few minutes prior to that observing the sector. The relieving controller also remained at the sector for a few minutes after. We were working on creating a line of arrivals into [airport]; as one aircraft canceled IFR we would clear the next for the approach. We had a relay on the ground at [airport]; [organization] temporary traffic advisories; that would call and advise when aircraft cancel IFR. All aircraft were canceling either upon touchdown or shortly before and we would clear the next one in.at [one point] we were unable to contact the relay at [the airport]; and they had not advised us of the IFR cancellation on an arrival so I broke off the next two arrivals. I hoped this would give time to recontact the relay and/or get an IFR cancellation for the arrival. A couple minutes went by with no success so I instructed aircraft X to turn left heading 180. As I am giving this instruction the [airport ground personnel] relay calls and advised the arrival is canceling IFR. I realize this as soon as finished the transmission to aircraft X and tell him to disregard; cleared direct [fix]; maintain 4;000 feet until [fix]; cleared for approach [airport]. The pilot accepts. When I gave this clearance I believed the aircraft had not progressed [fix] and would stop his turn; if he had even started it; and go direct to [fix]. I then continue working on the arrival string trying to fit the two aircraft I had to peel out back in. Shortly after I see that aircraft X is turning to the left and I instruct him to fly heading 180. I then tell aircraft Y to climb up to 5;000 feet and give him a turn to the west shortly thereafter.there appeared to be a loss of separation standards (loss) and after review it seems the closest they were was approximately 4.8 NM and 900 feet.I then asked for a handoff to help with the recovery from turning four aircraft from the arrival to [airport] and re-sequencing.after reviewing the data I realize that aircraft X was either over [fix] or even possibly already progressed and that he either was turning back to [fix] or conducting a procedure turn. At the time I felt that the pilot had not started his turn; or if he had it would have been minimal; and I could give him [fix] and the approach instead of re-sequencing. I was definitely pressured; not by anyone in particular; to get the arrivals in as fast as possible as we had 9 arrivals on frequency and every sector around was holding for [airport]. If I did not think that the pilot would have flown straight ahead along the approach I would not have issued that clearance.this event was a long time in the works between both ARTCC and [event organization]; not sure exactly the time table but I became aware of it about 4 months prior to the event. Leading up to the event I noticed there seemed to be little being done for a plan. What we were told was that aircraft going to the fly-in will almost be all VFR and that [the organization] had procedures for them in which we would cancel radar services and tell them to 'monitor [airport] advisory on [frequency]' there was little to no planning for IFR as the ARTCC airspace planners believed there would not be any. There were a few discussions between the (union) area rep; (union) area airspace rep and the airspace office on how we believed these procedures were not sufficient. There was even an idea of splitting the sector by altitude to give us the ability to segregate normal overflights from the [airport] event aircraft utilizing the sector frequency for the low [sector] and using a neighboring sector frequency;high [sector].that was rejected on the basis of being told it would take over 6 months for frequency analysis to certify a frequency.for departures; which have not happened at this point; we were told that all aircraft will be instructed to not contact sector. We were also briefed that instructions will be given on what frequency to contact at certain points as they depart. In my opinion telling aircraft that we cannot provide a service does not constitute a primary plan. Not one word was mentioned about IFR departures.overall I feel that the coordination between airspace [office] and the [sectors] area could have been better; anytime the event was brought up airspace [office] reminded us that it will be almost all VFR and that we will switch them well before [airport]. I believe because of this mindset there was little thought and planning put into IFR arrivals and what to do with them. If there was a simple time slot system in place; say 4-5 aircraft every 15 minutes that a lot of this traffic and pressure could have been alleviated. Again though; anytime we went to airspace with ideas we were met with their belief that we would see very little IFR inbounds leading us to this point.

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Original NASA ASRS Text

Title: Controller cancelled an approach clearance for an aircraft due to not receiving previous arrival IFR cancellation. Upon cancelling the approach clearance ATC received the previous inbound cancellation. The Controller re-cleared the aircraft for approach via a fix it had already passed. The aircraft reversed course to the fix which put it into confliction with another aircraft behind it awaiting approach clearance. The airport was very busy due to a 'fly-in' with numerous aircraft conducting IFR approaches. The airport does not have a Tower and coordination was being accomplished through ground personnel at the fly-in. Coordination communication was intermittent with the ground personnel increasing ATC workload.

Narrative: A fly-in at [airport]. We were briefed that there could be 600 to 1;000 aircraft come to the event; but that almost all will be VFR. We inquired about what if we have lots of IFR arrivals; were there any procedures in place to help and were told that there will minimal IFR pilots. That the [event organization] is generally VFR private pilots.I took [sector] after a thorough briefing and a few minutes prior to that observing the sector. The relieving controller also remained at the sector for a few minutes after. We were working on creating a line of arrivals into [airport]; as one aircraft canceled IFR we would clear the next for the approach. We had a relay on the ground at [airport]; [organization] temporary traffic advisories; that would call and advise when aircraft cancel IFR. All aircraft were canceling either upon touchdown or shortly before and we would clear the next one in.At [one point] we were unable to contact the relay at [the airport]; and they had not advised us of the IFR cancellation on an arrival so I broke off the next two arrivals. I hoped this would give time to recontact the relay and/or get an IFR cancellation for the arrival. A couple minutes went by with no success so I instructed Aircraft X to turn left heading 180. As I am giving this instruction the [airport ground personnel] relay calls and advised the arrival is canceling IFR. I realize this as soon as finished the transmission to Aircraft X and tell him to disregard; Cleared direct [fix]; maintain 4;000 feet until [fix]; cleared for approach [airport]. The pilot accepts. When I gave this clearance I believed the aircraft had not progressed [fix] and would stop his turn; if he had even started it; and go direct to [fix]. I then continue working on the arrival string trying to fit the two aircraft I had to peel out back in. Shortly after I see that Aircraft X is turning to the left and I instruct him to fly heading 180. I then tell Aircraft Y to climb up to 5;000 feet and give him a turn to the west shortly thereafter.There appeared to be a Loss of Separation Standards (LOSS) and after review it seems the closest they were was approximately 4.8 NM and 900 feet.I then asked for a handoff to help with the recovery from turning four aircraft from the arrival to [airport] and re-sequencing.After reviewing the data I realize that Aircraft X was either over [fix] or even possibly already progressed and that he either was turning back to [fix] or conducting a procedure turn. At the time I felt that the pilot had not started his turn; or if he had it would have been minimal; and I could give him [fix] and the approach instead of re-sequencing. I was definitely pressured; not by anyone in particular; to get the arrivals in as fast as possible as we had 9 arrivals on frequency and every sector around was holding for [airport]. If I did not think that the pilot would have flown straight ahead along the approach I would not have issued that clearance.This event was a long time in the works between both ARTCC and [event organization]; not sure exactly the time table but I became aware of it about 4 months prior to the event. Leading up to the event I noticed there seemed to be little being done for a plan. What we were told was that aircraft going to the fly-in will almost be all VFR and that [the organization] had procedures for them in which we would cancel radar services and tell them to 'Monitor [airport] advisory on [frequency]' There was little to no planning for IFR as the ARTCC airspace planners believed there would not be any. There were a few discussions between the (Union) area rep; (Union) area airspace rep and the airspace office on how we believed these procedures were not sufficient. There was even an idea of splitting the sector by altitude to give us the ability to segregate normal overflights from the [airport] event aircraft utilizing the sector frequency for the low [sector] and using a neighboring sector frequency;high [sector].That was rejected on the basis of being told it would take over 6 months for frequency analysis to certify a frequency.For departures; which have not happened at this point; we were told that all aircraft will be instructed to not contact sector. We were also briefed that instructions will be given on what frequency to contact at certain points as they depart. In my opinion telling aircraft that we cannot provide a service does not constitute a primary plan. Not one word was mentioned about IFR departures.Overall I feel that the coordination between airspace [office] and the [sectors] area could have been better; anytime the event was brought up airspace [office] reminded us that it will be almost all VFR and that we will switch them well before [airport]. I believe because of this mindset there was little thought and planning put into IFR arrivals and what to do with them. If there was a simple time slot system in place; say 4-5 aircraft every 15 minutes that a lot of this traffic and pressure could have been alleviated. Again though; anytime we went to airspace with ideas we were met with their belief that we would see very little IFR inbounds leading us to this point.

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.