Tower Controller and flight crew reported a misunderstanding regarding a takeoff clearance which resulted in tower issuing go-around instructions to an aircraft on final.
Synopsis
Tower Controller and flight crew reported a misunderstanding regarding a takeoff clearance which resulted in tower issuing go-around instructions to an aircraft on final.
Narrative
I had previously launched Aircraft A on a 190 heading off Runway 19. Followed by clearing Aircraft Z for takeoff on Runway 15 on a 170 heading. While clearing Aircraft Z for takeoff; the readback was somewhat garbled but over everything; I heard Aircraft Z read back the correct clearance. I assumed that maybe someone checked in on final at the same time. While following Aircraft Z down the runway to observe an eastbound heading off departure; the ASDE-X alerted for Runway 19. Initially; my thoughts were that this was a malfunction with the ASDE-X but shortly after giving Aircraft Y go-around instructions; I observed Aircraft X was on the numbers of Runway 19. At that point I was not sure if Aircraft X was LUAW or taking off. While issuing go around instructions to Aircraft Y; I then observed Aircraft X on departure roll. By the time I was done keying up I thought it was too late to cancel his takeoff clearance.At that time; my biggest concern was to make sure Aircraft Y turned as quickly as possible while Aircraft X was rolling underneath. After observing Aircraft Y turning away; I then observed Aircraft X turning to what appeared to be a 170 heading. I then instructed Aircraft X to turn to heading 190 to keep them separated from Aircraft Z. Prior to this last transmission; it was my belief that I had never given Aircraft X a control instruction. Recommendation - In hindsight; any time I hear a garbled transmission; I would want to reiterate my previous control instruction transmission to event a re-occurrence of this event.
Second reporter narrative
The flight was from DCA to ZZZ. It was a typical busy day at DCA with many departures and arrivals being sequenced in rapid-fire succession. We were in the number one position of the hold bay for Runway 19. Tower told us that were number three for departure (behind Aircraft Z and Aircraft A). After those two had taken off; it sounded to me like they cleared an aircraft to take off from Runway 15 and then gave us takeoff clearance; warning us that the other traffic would cross in front of us. From the right seat; I could not see the landing traffic due to the angle created by the River Visual 19 approaches being flown. It looked a little tight on TCAS; but DC Tower is known for tight clearances between takeoff and landing traffic. I've seen and been part of several go-arounds due to this; so I didn't question it. I had read back the clearance and Tower didn't correct me. While taking the active; the aircraft on 15 crossed 19 as (in my mind) Tower had told us to expect. As the Captain advanced the throttles for takeoff; Tower directed Aircraft Y to go around. Obviously (again; to my mind); Tower had been too aggressive in their spacing. On departure leg; Tower called us and said 'Aircraft X; possible pilot devi... disregard.' The Captain and I were confused at this; but they had said disregard. After being passed to Departure; ATC did inform us of the possible pilot deviation and gave us a phone number to call. The flight was long (almost two hours) and the Captain and I discussed what the deviation could have been. Neither of us could figure out what we might have done wrong. We believed we were given takeoff clearance and read it back. Tower did not correct us or tell us to hold short of the runway; which there was plenty of time for. After landing; the Captain called the number and spoke to ATC personnel. Apparently; there had only been one takeoff clearance given and that was for the 15 departure. Both that aircraft and I had acknowledged the clearance simultaneously and Tower did not catch it.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.