PC-12
Communication Breakdown; Situational Awareness
ATC Issue All Types; Conflict NMAC
Flight Crew Took Evasive Action
Human Factors
As we were joining an extended left downwind for Runway 16 at 1;900 feet; a PC-12 contacted Tower for departure as they were holding short of Runway 11. Tower instructed the PC-12 to hold short for crossing downwind traffic for Runway 16. The PC-12 held short. As other traffic landed on Runway 16 Tower instructed the PC-12 to line up and wait on Runway 11; and to hold short for downwind traffic. After a few moments he then cleared the PC-12 for takeoff; afterwards telling us to watch out for the departing traffic off Runway 11. The timing was perfect for a collision as the PC-12 took off with no relative motion; climbing to directly intercept our flight path. After the TCAS announced 'TRAFFIC!' we were forced to adjust our downwind leg; with a climbing left turn to avoid a collision with the departing PC-12.Tower could have waited for us to cross the departure end of Runway 11 before clearing the other PC-12 for takeoff.
A PC-12 pilot reported that while on downwind ATC released another PC-12 for takeoff from a crossing way; resulting in an airborne conflict that required evasive action.