Narrative:

The tower local control positions were de-combined. Traffic was easterly operations. I was monitoring local north. A VFR B350 was awaiting departure. I received a point out of a flight of two H60s that were transitioning from west to east that would definitely effect any north field traffic. I also anticipated the helicopters to be traffic for any departures on the northside. The local north controller issued traffic to the B350 that had departed referenced the H60s and a cherokee. The B350 reported the helicopter traffic in sight. Once I heard that the conflict appeared to be resolved; I resumed to assigning duties for the position rotation. The controller switched the B350 and advised TRACON that they were looking for the traffic.I was not aware of a cessna inbound. The C172 was on the south local controller frequency. At the time; the atm (air traffic manager) was in the cab talking to other controllers about other things; and during the occurrence he was standing directly behind the two controllers on position watching them work; obstructing my view. If he saw something peculiar; he could have brought it to the attention of any one of us at the time. After the fact; the atm discussed with me that the B350 did not have the cessna in sight. I assume this was after he reviewed the audio. I explained to him that I was not aware of the C172 until after the audio and falcon replay. Prior to this revelation; the north controller had called the cessna a cherokee but did give the traffic call. I heard the collision alert; which alarmed well after the B350 was switched to the sector. I heard externally the south controller give traffic alerts to a cessna that appeared to be not answering. The controller was making transmissions to provide the traffic. The controllers (and I am not sure if they did; you cannot hear from my distance) could have coordinated the cessna and B350 intentions. If I had known in time about the cessna; I could have suggested to the local south controller to give a suggested VFR heading i.e. (For more positive control) vice the 'turn southbound' instruction. I would recommend a group review of the situation with all parties involved to discuss; learn and prevent any possible future re-occurrence.having an atm in the cab and talking to other controllers; and then literally standing behind the local controllers watching them; while they were working traffic during that event; may have been a contributing human factor to their performance. Especially when they are working [non]- standard operation.

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Original NASA ASRS Text

Title: ATC Tower Supervisor and Local Controller reported a NMAC.

Narrative: The Tower Local control positions were de-combined. Traffic was easterly operations. I was monitoring Local North. A VFR B350 was awaiting departure. I received a point out of a flight of two H60s that were transitioning from West to East that would definitely effect any North field traffic. I also anticipated the Helicopters to be traffic for any departures on the Northside. The Local North Controller issued traffic to the B350 that had departed referenced the H60s and a Cherokee. The B350 reported the Helicopter traffic in sight. Once I heard that the conflict appeared to be resolved; I resumed to assigning duties for the position rotation. The controller switched the B350 and advised TRACON that they were looking for the traffic.I was not aware of a Cessna inbound. The C172 was on the South Local Controller frequency. At the time; the ATM (Air Traffic Manager) was in the cab talking to other controllers about other things; and during the occurrence he was standing directly behind the two controllers on position watching them work; obstructing my view. If he saw something peculiar; he could have brought it to the attention of any one of us at the time. After the fact; the ATM discussed with me that the B350 did not have the Cessna in sight. I assume this was after he reviewed the audio. I explained to him that I was not aware of the C172 until after the audio and Falcon replay. Prior to this revelation; the North controller had called the Cessna a Cherokee but DID give the traffic call. I heard the collision alert; which alarmed well after the B350 was switched to the sector. I heard externally the South Controller give traffic alerts to a Cessna that appeared to be not answering. The controller was making transmissions to provide the traffic. The controllers (and I am not sure if they did; you cannot hear from my distance) could have coordinated the Cessna and B350 intentions. If I had known in time about the Cessna; I could have suggested to the Local South controller to give a suggested VFR heading i.e. (for more positive control) vice the 'turn southbound' instruction. I would recommend a group review of the situation with all parties involved to discuss; learn and prevent any possible future re-occurrence.Having an ATM in the cab and talking to other controllers; and then literally standing behind the local controllers watching them; while they were working traffic during that event; may have been a contributing Human Factor to their performance. Especially when they are working [non]- standard operation.

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.