Date: 201210
Local time of day: 1801-2400
Location: BWI.Airport, MD
Flight conditions: VMC
Light: Daylight
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
Airspace: Class B BWI
ATC / advisory: Tower BWI
Reporter organization: Air Carrier
Reporter function: Pilot Flying; First Officer
Human factors: Confusion; Distraction; Time Pressure; Communication Breakdown
Anomaly: ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Clearance
Contributing factors: Procedure
Primary problem: Procedure

Narrative: The confusion began when we were given instructions to 'line up and wait' on Runway 33L. A heavy had just landed and was rolling out long and we were taking our position on the runway as cleared. Additionally; there was an inbound aircraft on an approximately 4 mile final at this time; and it was obvious the Controller was attempting to speed our departure along in an effort to prevent a go-around by the inbound aircraft. Next; the Controller issued departure instructions to us while we were in position; which we believe included a heading and something regarding contacting Departure Control. Unfortunately; the aforementioned instructions were very hurried; mumbled and quite ambiguous. Both the Captain and I were unsure of what the Tower Controller had just said; although we were certain no takeoff clearance had been issued. The landing aircraft was still on the runway. The Captain; who was the pilot not flying; queried the Controller on the aforementioned instructions. In fact; the instructions were so vague and confusing that we asked the Tower Controller if he wanted us to contact Departure at that time while we were in position. No reply was received; instead several seconds later we were cleared for takeoff as the heavy aircraft was exiting the runway. During the initial climb out; the Captain again asked the Controller to verify the heading at 250 degrees and the response we received was '150' with no turn direction included. As a result; he turned the heading indicator to 150 and we initiated a turn to the right; absent any directional instructions. We turned right since this was the shortest direction to that heading (runway heading 335). We were approximately 30 degrees into the turn and approaching acceleration altitude when the Captain asked the Tower Controller to switch to Departure frequency. The response from the Tower was to inform us the 150 degrees heading was to be a left turn. As a result; we immediately initiated a turn direction back to the left. Shortly thereafter we contacted Departure Control. We received no traffic alerts and nothing extraordinary was said on the Departure frequency regarding our initial turn to the right. The flight continued to our destination without incident. ATC Controller should issue clear; appropriate departure instructions at the appropriate time. Flight crew should not begin takeoff roll without being 100% certain of departure instructions; regardless of proximity of inbound aircraft.




Synopsis: An Air Carrier issued a hurried takeoff clearance from BWI was not given a clear departure vector heading and after a takeoff track deviation were given a new heading by the TRACON.