Regional Jet 900 (CRJ900)
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Communication Breakdown; Situational Awareness
ATC Issue All Types; Conflict Airborne Conflict; Inflight Event / Encounter CFTT / CFIT
Flight Crew Took Evasive Action
Human Factors; Procedure
Departing ABE as per tower instructions and Company SOPs; a TCAS RA was triggered at approximately 800 ft. AGL during initial climb out. Flaps had not yet been retracted (20 degrees) and autopilot had not yet been selected on. The TCAS RA was followed; as well as a late vectoring from ABE Tower. The TCAS RA's required descent triggered a 'Don't Sink' aural from the aircraft GPWS.TCAS TA was triggered at approximately 500 ft. AGL as well as pilot monitoring identifying the aircraft in sight. Tower simultaneously vectored [us] to heading 280; and general aviation aircraft to turn away. TCAS RA was triggered during the turn and the TCAS RA was followed until the situation was resolved. ABE Control Tower cleared [us] for departure; runway heading; up to 3;000 ft. (I believe). At the same time; ABE Approach vectored a general aviation light aircraft directly into [our] initial climb out path. Tower and Approach failed to communicate to one another the instructions given and caused two aircraft to be vectored onto a collision course.An immediate turn to heading 280 was initiated; however; during the turn the TCAS RA was triggered indicating the need for a 3;000 ft./min descent. The resolution was resolved before a full 3;000 ft./min descent was achieved. A GPWS 'Don't Sink' aural was triggered during the TCAS RA's required action. This event occurred at 800 ft. AGL. No limitations were broken during the TCAS RA maneuver. The previously instructed heading; climb; and initial climb SOP procedures were followed after the resolution.Due to lack of internal ATC communication between approach and tower; [we were] accidentally cleared for departure into another aircraft. The TCAS RA which occurred during the initial climb-out at 800 ft. suggested that [we] descend at 3;000 ft./min. Luckily the RA was resolved before 3;000 ft./min was achieved; and autopilot had not yet been activated (increasing reaction time from pilot flying). The rate of descent the TCAS required triggered a 'Don't Sink' call from the GPWS; leading me to believe that the resolution of one situation could have caused the creation of another.
CRJ-900 First Officer reported that a TCAS RA commanded a descent shortly after departure that caused a GPWS 'Don't sink' alert.