Air carrier flight crew reported a communication breakdown between flight crew and ATC which resulted in a critical ground conflict.
Synopsis
Air carrier flight crew reported a communication breakdown between flight crew and ATC which resulted in a critical ground conflict.
Narrative
[The flight] pushed on time. Ground Control instructed taxi to Runway XXL for departure and gave us a wheels up time of +15 min. We were then switched to Tower frequency with Aircraft Y holding short of Runway XXL full length and us as Aircraft X. Tower asked us to pull into the hold block for XXL to allow Aircraft Z behind us to access the runway via intersection Taxiway 1. Tower then gave Aircraft Z take off clearance from intersection Taxiway 1 but denied back taxi for full length. Aircraft Z then declined the takeoff clearance and informed Tower they would need to reload data and perform a checklist. After landing traffic on XXL; Tower asked Aircraft Z if they could move to give us access to the Runway via Taxiway 1; so we could make our wheels up time. Aircraft Y had a later wheels up time and was still holding short full length XXL. Aircraft Z was cleared to taxi down Runway XXL and clear Taxiway 2 back onto Taxiway 3. We were instructed to hold short of Runway XXL at Taxiway 1. I chose to hold our position in the hold block while we dealt with the additive condition of task loading with a runway change. Tower asked if we could take Taxiway 1. We replied on the radio that we needed a minute to load new data and run a checklist. Tower responded that we had 50 seconds to make our wheels up time or we would need a new wheels up time. I responded to please get us a new wheels up time. Traffic permitting; Tower then cleared Aircraft Y and Aircraft Z for departure; leaving us as the only aircraft in the holding block. Tower informed us of our new wheels up time. We asked Tower if we should now expect a full length departure from XXL to which they replied; 'Stand by.' Approximately five minutes passed with no response from Tower on departure point. Approaching our new wheels up time; Tower instructed us to taxi up to and hold short of Runway XXL full length. With the intersection data loaded; I told Tower that each time they change our departure point; we need to load new data and run a checklist. Tower changed out taxi instructions to taxi up to and hold short of Runway XXL at Taxiway 1. As we taxied; the First Officer had deleted our data; when our clearance was for full length; but then reloaded when our taxi instructions changed to the intersection of Taxiway 1. As we approached XXL at Taxiway 1; Tower issued what we thought was position and hold on Runway XXL at Taxiway 1. With the additive conditions of task loading to accomplish the Before Take Off Checklist and the operational pressure to make our wheels up time along with meeting minimum fuel requirements for the flight; I was getting behind and did not hear Towers second clearance. I believe both the First Officers and I's expectation bias led us to believe that a second instruction from Tower would be a line up and wait. I did rely on my First Officers response to the call; which was line up and wait XXL at Taxiway 1. Tower did not catch our error nor make any correction. As I entered the runway at Taxiway 1; I cleared final and saw company aircraft at 800 ft on final approach. I thought it was tight but it fit into my expectation bias that Tower was trying to make our wheels up time since they had emphasized our first wheels up time. As I lined up on centerline for Runway XXL; I expected a takeoff clearance but none was received. After an awkward silence and glancing at the TCAS display and now seeing company at 600 ft on final I got the sinking feeling that there may have been a miscommunication. The next radio call was Tower instructing company to go around. Tower then asked us to copy down a phone number for possible pilot deviation. I think several things led to this communication error and runway incursion. I think the Tower Controller could understand the task loading created with multiple runway changes for intersection departures. Our error was allowing additive conditions to put us behind as a crew and then letting our expectation bias for makingour wheels up time. This resulted in the communication error of reading back the wrong clearance. In the future I will not allow myself to take the runway if I feel behind for any reason regardless of a wheels up time.
Second reporter narrative
While taxiing to Runway XXL for departure; Tower informed us of a flow time to ZZZ1 and instructed us to pull into the hold pad. There was an aircraft holding short of the runway at Taxiway 4 intersection for the full length. As our flow time approached; Tower told us that we would have to depart from Taxiway 1 intersection; and that we would not be able to back taxi. At this time we informed Tower that we would have to re-run our performance numbers and it would take a few minutes. Tower responded that they would have to get a new flow time for us; which we said was OK.After we had new performance numbers for the Taxiway 1 intersection departure; we let Tower know and received a new flow time. While we were waiting for our new flow time; the aircraft that was on Taxiway 4 for the full length departed. We asked which intersection we could plan on departing from; since we would have to re-run our numbers again for full length. Tower told us to standby; but never answered our question. As our new flow time approached; Tower told us to taxi to the full length intersection at Taxiway 4; at which time we informed them that we would have to change our performance numbers again. As we were in the process of changing our performance numbers; Tower instructed us to hold short of the runway at the Taxiway 1 intersection. It was during this time of high workload; while undoing the changes we had begun to make so we could meet our flow time; that we mistook Tower's instruction for a lineup and wait clearance. When reading back the instructions; we read back 'Runway XXL at Taxiway 1 lineup and wait;' and did not get any response or challenge from Tower. After lining up on the runway at Taxiway 1; we expected immediate takeoff clearance as there was an aircraft on final; but the clearance didn't come and the landing aircraft was instructed to go around. Once that aircraft was clear we were informed of the possible pilot deviation. We were then given takeoff clearance. If we had gotten earlier communications from Tower about the sequence of aircraft and the need for an intersection departure; we could've avoided the additive conditions that led us to be behind. If Tower had answered our question of what takeoff point we could expect for our new sequence we could've re-programmed our performance numbers while we were waiting; and we wouldn't have been task loaded at the last minute approaching our flow time. If we had told Tower we could only accept a Taxiway 1 intersection departure; when Tower instructed us to taxi for the full length; we could have avoided another last second change; which led to us being task loaded and miss hearing the second taxi instruction from Tower. If Tower had clarified our clearance after we read back XXL at Taxiway 1 lineup and wait we wouldn't have deviated from the initial instructions we were given.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.