A319
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Last 90 Days 160; Flight Crew Total 10140; Flight Crew Type 2316
Training / Qualification; Situational Awareness; Human-Machine Interface; Fatigue; Confusion
Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Ground Excursion Runway
Flight Crew Became Reoriented
Environment - Non Weather Related; Airport; Human Factors; Weather; Chart Or Publication
During an early morning; low light departure from ZZZZ; we received our final weights and learned we would be departing at our absolute maximum allowable takeoff weight. We had to do everything we could to get every last bit of performance out of the plane due to our heavy weight; high altitude operation (ZZZZ is above 7;300 MSL) and distance to destination. We requested Runway XR for departure due to its longer length and therefor higher max takeoff weight. The Captain; who has been into and out of ZZZZ many times; remarked that he had never taken off XR in all the years he'd been operating into ZZZZ. ATC (Air Traffic Control) cleared us to cross runway XL and line up and wait on XR right as our weight reached our max takeoff weight. We entered the runway at a 45deg angle from taxiway A1. To our right there was additional concrete that the Captain; who was on the left side of the plane at a funny angle; thought was a displaced threshold. He remarked to me that he wanted to back taxi to make use of all available runway due to our weight concern after he began his right turn to back taxi. As he turned the airplane right to back taxi and my attention shifted from an expected left turn to a right turn; I saw chevrons painted on the ground indicating this was not a displaced threshold. At that point we were committed to the turn as he couldn't stop the turn and reverse direction with the pavement available. The Captain continued the right hand turn and completed a 315deg right turn and lined back up with the centerline of the Runway XR. As we did this maneuver the Tower Controller saw us turning right instead of left and became very agitated; confused and got upset with us over the radio in a very unprofessional way. After we lined up with the runway in the proper direction; we apologized to the controller and made a normal takeoff without incident. There were several small factors that contributed to this event in my opinion starting with our heavy weight and high altitude departure. It was night time operations leading to poor visibility combined with the captain's odd angle entering the runway and the runway taxi lights being at high intensity not allowing us to clearly see the painted; unlit; chevrons on the over run. The Captain was referencing the AMM chart and didn't have the map enlarged enough to show the chevrons on the chart; only the paved surface. His unfamiliarity with XR was a contributing factor as well as both pilots being a bit tired from the very early morning wake up.
A319 Flight Crew taxied onto unusable portion of runway.