Air carrier flight crew and DFW Ground Controller reported weather ground stop; airport and frequency congestion with miscommunication resulted in a critical ground conflict.
Synopsis
Air carrier flight crew and DFW Ground Controller reported weather ground stop; airport and frequency congestion with miscommunication resulted in a critical ground conflict.
Narrative
ILS TO 36 L First Officer (FO) was pilot flying (PF). Briefed right turn off and one runway or cross. On the runway around 60 kts and me about to take the aircraft and taxi off the high speed; Tower called Aircraft X stay on the runway. I took the aircraft controls and eased off the brakes thinking we were going to the end. Then we got a quick Aircraft X turn right WK. It was a quick turn and took some effort; then got hold short echo to figure what I'm going to do with you; let me know if you have a gate. There were discussions about turning the airport around to South flow and we saw all the aircraft parked in the North pad. We were assigned gate and called ramp right away to find we had most likely an hour and a half delay to get a gate. I immediately thought we will go to the South pad where a widebody was already parked. We were told to taxi echo and hold short WL. We started taxiing South on echo and then were given a hold short at WM. This made total sense to me that we were facing East and spot XXX was right across the runway. I got to WM and turned left to hold short of 36R; after a short second we got a call to cross the runway and a traffic report. As I powered up to hustle across the runway I cleared left and when I looked right there was an aircraft taxiing into position. I thought he wanted us to go in front and hustle; but then I saw all the lights come on the aircraft on the runway and I hit the brakes…at the same time I got the call from Tower Aircraft X stop and the aircraft on the runway to stop. I also saw the red runway stop lights. I stopped short of the runway but unfortunately my momentum carried me past the hold short line. I can remember saying you cleared us to cross THE runway; Tower said that was not my plan for you. Thank God for the Tower Controller and the red hold lights. He then told us to cross 36R and turn right on F and hold short of the next taxiway. After giving way to the aircraft leaving the runway we taxied South all the way down to ER and stopped. We were given a number to call and talked about the confusion and my most likely misunderstanding. We then held for more than two hours before taxiing to our gate uneventfully.Cause: I believe fatigue was a large causal factor in our event; we started our day at XA:00 sign in and were delayed four hours before leaving to ZZZZ. We had many challenges during the day and the FO did an excellent job from the beginning calculating legality for takeoff with the high winds. We then faced weight restrictions in ZZZZ for the return leg as well as alternate requirements for forecast weather. We were also facing length of duty day limits. I also had an expectation bias. We have been trained to brief runway crossings and briefed we would have one runway to cross. I never even thought of crossing back over 36L and I think that was the controller's plan. Ultimately; it is my responsibility to taxi the aircraft on the ground and I own it. Lots of confusion for both controllers and pilots; this was definitely the perfect storm for me.Suggestions: It's embarrassing; I thought this would never happen to me. We train for this. Both pilots confirm and readback crossing instructions. I got so scope locked on helping out the controllers on such a busy day and getting out of their way. I thought we had one runway to cross; 36R; never thinking of his plan. All the talk and chatter on the frequency had me believe we were going to cross 36R at WM to go to the south pad. I need to write down and verify those instructions. We used to use the scratch pad on the FMC. Total expectation bias on my behalf. The long and challenging day got me off my game."
Second reporter narrative
After landing in DFW on 36L at XM:14; we were instructed to continue down the runway. We were abruptly asked to exit the runway via a right turn onto WK as we were nearly abeam the intersection. The aircraft was safely in a position to make the turn; so we accepted the clearance and vacated. We were instructed to hold short of Taxiway Echo and check on the availability of our gate; which I believe at the time was [gate] XX. Gate was occupied for an extended amount of time due to weather in DFW throughout the day. The airport was very congested with aircraft waiting for gates as well. Around this time; ATC announced on frequency that the airport was about to be switched to South flow. ATC was notified of the extended delay for our arrival gate. We were then instructed to continue south on Echo and to hold short of WL. Approaching/holding short of WL; we were then instructed to continue South on Echo. From this point; we interpreted/believed the instructions given were to turn onto WM and hold short of 36R; so that is what we did. The next clearance was given in an expeditious manner to cross 36L and turn right onto Charlie. This clearance did not make sense; and was impossible given our position on WM facing East. I queried ATC while looking at the taxi diagram and asked if they meant to cross 36R and turn right on Foxtrot or Gulf. Due to the confusion and the expeditious clearance to cross the runway due to traffic; we proceeded to cross the hold short line. ATC instructed us to stop the aircraft; which we did immediately short of the runway edge markings; and ATC instructed the aircraft that had commenced its takeoff roll to reject. ATC then informed us that we did not do what he planned for us to do; and we were then instructed to cross 36R and contact Ground. We followed Ground's instructions to the Southwest hold pad where we waited over two hours for a gate. After receiving the clearance from Ramp that the gate was open; we continued to [gate] XY with no further incidents/events.Cause: Factors that I believe were contributors or played a role in our event would be but not limited to: 1) long duty day; 2) weather; 3) taxiway/ramp congestion; 4) expectation biases; 5) frequency congestion/confusion; and 6) miscommunication. 1) Our day started with a sign in time of XA:05 time in DFW. At the time of the event; it was around XM:20 in DFW. We had dealt with weather; crosswind limits; runway changes; takeoff limits; delays; gate changes; etc. 2) The weather in DFW in the morning and throughout the day caused significant delays. It created a situation of arriving aircraft waiting for 2+ hours for a gate. Due to all the aircraft arriving; there were many aircraft in positions throughout the airfield waiting for gates. This created a sense of urgency; confusion; nonstandard instructions from ATC to hold aircraft out of the way. 3) The taxiways and ramps were subsequently very congested; leaving ATC to move aircraft in directions that were never briefed or expected by crews. 4) Our expectation bias was in play due to our arrival briefing consisting of crossing the inboard runway to our gate. This could have caused a misinterpretation of ATC instructions if we actually received a different clearance than what we executed/expected. Also with the airport being turned to Southflow; there could have been expectation bias when assuming we were cleared to cross a runway because it was being switched around. 5) The frequency was very congested which seemed to cause confusion amongst crews and ATC. ATC was issuing clearances to aircraft using the wrong callsigns. When queried by those aircraft ATC responded with 'I don't even know what I said; but yes I meant Aircraft X'. Crews and ATC were also stepping on the other's transmission inevitably due to the amount of aircraft on frequency. This could be a contributor to missing a clearance; reading back the wrong clearance; or not being corrected on a read back. 6) Somewhere along the way there was miscommunication ultimately. Either an instruction was given; read back properly and then turned the wrong direction; instruction was given by mistake and we complied; or an instruction was given and then read back incorrectly and it was not corrected by ATC. Suggestions: The miscommunication in the clearance we given/expected of us and what was executed put the aircraft in the wrong direction on a taxiway. This was not caught be either crew or ATC. Ultimately; this could have been corrected if any miscommunication was clarified before entering the taxiway. The runway incursion could have been prevented by; not moving the aircraft if unsure/unclear taxi instruction were received until confirmation of clearance. The runway incursion could have been prevented by ATC interpreting their data and tools to see the aircraft was not in position to perform an instruction that was impossible at the time.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.