Narrative:

An updated tower-TRACON LOA went into effect recently. One of the changes requires tower to sequence VFR arrivals from the downwind. Approach is still responsible for sequencing all IFR and final traffic. A C182 was handed off 10 NM to the southwest and appeared to be on a left dog leg/base; for runway 34L. A B737 was then handed off to tower 15 NM to the southeast for runway 34L. The C182 checked on frequency for runway 34L and was cleared to land. Because the C182 appeared to be on base and not a downwind I assumed approach was sequencing. It became apparent that there was no way the C182 could beat the B737 to the runway. I asked the C182 if he was instructed to enter on the downwind. He said he was instructed to enter on a 45 for the left downwind runway 34L. I re-sequenced him to follow the B737 now on a 10 NM final. This portion of the report was a non event but there was confusion in the tower cab including a flm on who should be providing the sequence since it did not appear the C182 was in a position to enter a downwind. The C182 reported the B737 in sight and followed to runway 34L with a wake turbulence advisory. A T38 was on the left downwind handed off but not yet on frequency. The data tag indicated that the T38 would be flying the ILS runway 34L and then remaining in the tower pattern after the option. The C182 turned an approximate 3 NM base behind the B737 with the T38 still on the downwind. I was expecting approach to take the T38 out 10 NM or more for the ILS and to provide spacing behind the C182. As the C182 rolled out on a 3 NM final the T38 turned an 8 NM base for runway 34L still not on frequency. Winds at the time were out of the north at 20 KTS. The C182 slowed to 60 KTS on final with the T38 now inside of 8 NM and 250 KTS. I discussed with the flm on duty that I did not believe this scenario would work and wondered if approach was going to break out the T38. When the C182 was on approximate a 2 NM final the T38 was 4 NM in trail; still inbound with +200 KT overtake. I called approach to tell them I was not talking to the T38 and to break him off the approach. The approach controller at the time was very busy working other traffic but I heard her issue a left turn heading 270 to the T38 and I unkeyed. I was not aware that the T38 had already been switched to my frequency and did not get the instruction from the approach controller. During this time part of my focus was on an airport vehicle occupying runway 34R conducting a runway inspection and an airbus on final for runway 34R. The T38 reported on frequency final for runway 34L requesting the option. When the T38 checked on there was less than a mile between him and the cessna ahead with approximate a 200 KT overtake. I told the T38 to go around immediately and issued the traffic. The T38 passed in close proximity to the cessna on final while executing a go-around. The LOA should be clearer on who is responsible for sequencing arrivals. The cessna did not appear to be in a position to enter the downwind and I had no way of knowing until asking the pilot. It was assumed by those in the tower cab that straight in and base traffic would still be sequenced by approach. If an aircraft is told to maneuver to enter a downwind by approach maybe it should be coordinated with tower or explained in the LOA to avoid confusion. Once a VFR arrival is turned to follow traffic and on final; traffic on the downwind should be vectored to follow. I thought since the T38 was still on a downwind being vectored for an ILS that approach would see the cessna they handed off to me on final and vector accordingly to provide sufficient separation. When it became apparent that the T38 would overtake the cessna I should have reached out to see if the T38 was on frequency. When I overheard the heading issued by approach I did not think the T38 may have already been switched and thought the problem was solved. I also did not issue a traffic alert but at the time a more immediate instruction of 'go around?' was needed.

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Original NASA ASRS Text

Title: Tower Controller described a traffic pattern conflict event when less than clear procedures in a new LOA with the TRACON introduce confusion as to how and who was responsible for sequencing etc.

Narrative: An updated Tower-TRACON LOA went into effect recently. One of the changes requires Tower to sequence VFR arrivals from the downwind. Approach is still responsible for sequencing all IFR and final traffic. A C182 was handed off 10 NM to the southwest and appeared to be on a left dog leg/base; for Runway 34L. A B737 was then handed off to Tower 15 NM to the southeast for Runway 34L. The C182 checked on frequency for Runway 34L and was cleared to land. Because the C182 appeared to be on base and not a downwind I assumed Approach was sequencing. It became apparent that there was no way the C182 could beat the B737 to the runway. I asked the C182 if he was instructed to enter on the downwind. He said he was instructed to enter on a 45 for the left downwind Runway 34L. I re-sequenced him to follow the B737 now on a 10 NM final. This portion of the report was a non event but there was confusion in the Tower Cab including a FLM on who should be providing the sequence since it did not appear the C182 was in a position to enter a downwind. The C182 reported the B737 in sight and followed to Runway 34L with a wake turbulence advisory. A T38 was on the left downwind handed off but not yet on frequency. The data tag indicated that the T38 would be flying the ILS Runway 34L and then remaining in the Tower pattern after the option. The C182 turned an approximate 3 NM base behind the B737 with the T38 still on the downwind. I was expecting Approach to take the T38 out 10 NM or more for the ILS and to provide spacing behind the C182. As the C182 rolled out on a 3 NM final the T38 turned an 8 NM base for Runway 34L still not on frequency. Winds at the time were out of the north at 20 KTS. The C182 slowed to 60 KTS on final with the T38 now inside of 8 NM and 250 KTS. I discussed with the FLM on duty that I did not believe this scenario would work and wondered if Approach was going to break out the T38. When the C182 was on approximate a 2 NM final the T38 was 4 NM in trail; still inbound with +200 KT overtake. I called Approach to tell them I was not talking to the T38 and to break him off the approach. The Approach Controller at the time was very busy working other traffic but I heard her issue a left turn heading 270 to the T38 and I unkeyed. I was not aware that the T38 had already been switched to my frequency and did not get the instruction from the Approach Controller. During this time part of my focus was on an airport vehicle occupying Runway 34R conducting a runway inspection and an Airbus on final for Runway 34R. The T38 reported on frequency final for Runway 34L requesting the option. When the T38 checked on there was less than a mile between him and the Cessna ahead with approximate a 200 KT overtake. I told the T38 to go around immediately and issued the traffic. The T38 passed in close proximity to the Cessna on final while executing a go-around. The LOA should be clearer on who is responsible for sequencing arrivals. The Cessna did not appear to be in a position to enter the downwind and I had no way of knowing until asking the pilot. It was assumed by those in the Tower Cab that straight in and base traffic would still be sequenced by Approach. If an aircraft is told to maneuver to enter a downwind by Approach maybe it should be coordinated with Tower or explained in the LOA to avoid confusion. Once a VFR arrival is turned to follow traffic and on final; traffic on the downwind should be vectored to follow. I thought since the T38 was still on a downwind being vectored for an ILS that Approach would see the Cessna they handed off to me on final and vector accordingly to provide sufficient separation. When it became apparent that the T38 would overtake the Cessna I should have reached out to see if the T38 was on frequency. When I overheard the heading issued by Approach I did not think the T38 may have already been switched and thought the problem was solved. I also did not issue a traffic alert but at the time a more immediate instruction of 'Go Around?' was needed.

Data retrieved from NASA's ASRS site as of July 2013 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.