Background
A Beech 99 departed on a VFR flight and began a climb to 10,500 feet on a heading of 175 degrees. The flight was operating in an area heavily traveled by small VFR aircraft, which frequently used the Cresso 3 Arrival (STAR).
Incident Sequence
As the Beech 99 reached the boundary of Class B airspace at 7,000 feet, the TRACON controller terminated radar service. Forty seconds later, the pilots of a Boeing 737, which was on the Cresso 3 Arrival, contacted TRACON and were cleared to descend to 10,000 feet on a converging vector of 020 degrees. Fifty seconds after that, TRACON advised the Boeing 737 pilots of traffic—the Beech 99—3 miles ahead, in opposite direction, and 1,700 feet lower. TRACON did not mention that the traffic was climbing, nor did it issue a safety alert. Eighteen seconds later, TRACON told the Boeing 737 pilots they could "climb as you wish."
The first officer of the Boeing 737, who was the flying pilot, responded to a TCAS resolution advisory by using the autopilot but neglected to press the "level change" button, which delayed the avoidance maneuver. The Boeing 737 pilots sighted the Beech 99 at close range, and the first officer maneuvered abruptly to avert a collision. The Beech 99 pilot saw the Boeing 737 behind a window post, too late for evasive action. The aircraft passed with an estimated 200 feet of vertical separation and no lateral separation.
Aftermath
A flight attendant on the Boeing 737 was injured during the abrupt maneuver. A TCAS event analysis concluded that if the Boeing 737 pilots had responded to TCAS advisories within the system design parameters, there would have been 700 feet of vertical separation without the need for abrupt maneuvering.