Piper PA-32R-301 N43450

The Piper and Cessna pilot were both inbound to the same airport in visual meteorological conditions (VMC).The Cessna pilot reported to the local controller (LC) that he was 1 mile south of a published reporting point located 13.5 miles to the northeast of the airport. The LC directed the pilot to report entering a left downwind, and the pilot continued on southerly heading for 4 miles before turning right to a southwesterly heading. The Piper pilot contacted the LC and reported 10 miles to the north of the airport. The LC directed the Piper pilot to enter a left downwind stating, "Cessna four five zero republic report entering left down", and the Piper pilot acknowledged, "left downwind for runway one ninner." The LC subsequently informed the Cessna pilot that he had possible traffic off his eleven o'clock position at a half-mile westbound at 1,000 feet. The Cessna pilot responded, "seven two mike looking for traffic." Forty one seconds later, the Piper pilot informed the LC of the collision and declared an emergency. The LC stated in an interview with the National Transportation Safety Board that he scanned the runways, traffic pattern, final approach course, and the remote automated radar display (RACD), when he noticed two VFR targets northeast of the field close to one another. Assuming the target on a southwesterly heading was a VFR helicopter passing to the north of the airport, the LC issued possible traffic to the southbound aircraft, assuming it was the Cessna pilot when it was actually the Piper pilot, and the Cessna pilot acknowledged the traffic call. Federal Aviation Administration (FAA) Order 7110.65, Air Traffic Control, paragraph 2-1-1, Air Traffic Service: "The primary purpose of the ATC system is to prevent a collision between aircraft operating in the system and to organize and expedite the flow of traffic, and to provide support for National Security and Homeland Defense. In addition to its primary function, the ATC system has the capability to provide (with certain limitations) additional services. The ability to provide additional services is limited by many factors, such as the volume of traffic, frequency congestion, quality of radar, controller workload, higher priority duties, and the pure physical inability to scan and detect those situations that fall in this category. The provision of additional services is not optional on the part of the controller, but rather is required when the work situation permits." According to the FAA, traffic advisories to VFR aircraft is considered an additional service. In addition, paragraph 2-1-21, Traffic Advisories: "Unless an aircraft is operating within Class A airspace or omission is requested by the pilot, issue traffic advisories to all aircraft (IFR or VFR) on your frequency when, in your judgment, their proximity may diminish to less than the applicable separation minima. Where no separation minima applies, such as for VFR aircraft outside of Class B/Class C airspace, or a TRSA, issue traffic advisories to those aircraft on your frequency when in your judgment their proximity warrants it.

Quoted verbatim from the NTSB record.