Incident Overview
While the aircraft was level at 3,000 feet above mean sea level and receiving radar vectors for an instrument approach, the flight crew received a traffic advisory (TA) from the Traffic Alert and Collision Avoidance System (TCAS). The co-pilot, who was flying the aircraft at the time, began a visual scan for the traffic. The pilot-in-command then took control by "yanking the controls" from the co-pilot and initiated a banking left turn.
Shortly after, TCAS issued a resolution advisory (RA) commanding a climb. The pilot-in-command increased the aircraft's pitch attitude and climbed approximately 800 feet while simultaneously rolling the wings level. Neither pilot made visual contact with the other aircraft. During the maneuver, the flight attendant sustained a fracture to her left leg.
Maneuver Details
The aircraft that triggered the TA passed within 0.75 nautical miles laterally and 100 feet vertically of the accident aircraft. Air traffic control did not consider the aircraft to be on a collision course but had notified the accident crew of its position. The flight data recorder indicated a maximum angle of attack of 15.6 degrees, a maximum bank of 32 degrees, and an altitude increase from 3,000 to 3,778 feet over 16 seconds. The entire maneuver lasted 40 seconds, with a peak rate of climb of 2,628.75 feet per minute and a maximum acceleration of 2.3 Gs.
Operator Guidance
According to the operator, a typical RA response involved a maneuver requiring a G-force of +/-0.25g. The operator advised that when using the TCAS traffic advisory display, flight crews should commence a visual search for the intruder and, only if visually acquired, maneuver to maintain separation. Maneuvers based solely on TCAS TAs without visual acquisition were not recommended. The operator also cautioned that certain vertical speeds were not safe and that crews should monitor the vertical speed indicator (VSI) and keep the pointer out of the "red prohibited area." The guidance advised crews to be prepared to maneuver should an RA sound 10 to 15 seconds later, and that the pilot flying should respond "promptly and smoothly" to an RA.