Air carrier flight crew reported during takeoff roll two military helicopters flew across the departure runway in front of the aircraft at low altitude; causing the flight crew to delay rotation to avoid a collision. The Captain stated they were not advised in advance by ATC of the helicopter traffic.
Synopsis
Air carrier flight crew reported during takeoff roll two military helicopters flew across the departure runway in front of the aircraft at low altitude; causing the flight crew to delay rotation to avoid a collision. The Captain stated they were not advised in advance by ATC of the helicopter traffic.
Narrative
Departing [Runway] XXL ZZZ XA:35 on Date; a pair of military helicopters were passing left to right over Runway YY; below 100 ft. We switched to tower frequency and received immediate takeoff clearance w/ traffic advisory on 6 mi final. Not advised of military helicopters flying in formation over Runway and as we began takeoff roll we assumed they would hold short of XXL. As it became evident they would not; an abort was quickly considered; and I decided against it as we had entered the high speed regime. We delayed rotation as we ran directly below the two military helicopters; had we rotated we would have collided. Had the military helicopters had a midair; or descended we would have collided. Contacted ZZZ Tower upon arrival in ZZZ1; Supervisor initiated an investigation. Received a call several hours later from supervisor requesting additional info. Sup stated we should have been advised of military helicopters traffic; however a review of tapes indicated no advisory was made. He further stated that evidence reviewed warranted further investigation; that he was writing a report and submitting it for review of procedures.If we were made aware of the traffic there is 0% chance we would have accepted the takeoff clearance. Suspect local controller was distracted by traffic on final.This was an unsafe operation; we should not have been given takeoff clearance; or advised of traffic so we could have not taken off. In retrospect an immediate reject while still in low speed regime may have been the safest course of action; but we really expected them to hold short of our runway.
Second reporter narrative
We were approaching the approach end of [Runway] XXL when ground instructed us to switch to tower; which I did. Before I could get a word out we heard 'Aircraft X are you ready'. I replied yes and tower told us there was an aircraft on a 6 mile final (assumed for XXL) and we were clear for takeoff. As we are turning onto the runway the Captain gave me the jet and I began to advance the throttles. As this is happening I see 2 military helicopters flying down Runway YY (which was closed according to the latest ATIS). As we were now steadily accelerating I watched as these helicopters rapidly approached the Runway XXL/YY intersection. I assumed they would stop but it was becoming apparent that they were not. At that point I had so many things quickly cross my mind: are we going to abort; will we hit these guys if I rotate on time; is their rotor wash going to affect us; etc. I recall watching in horror as these very low (estimated by me at 100 feet AGL) helicopters were crossing our path right about the time V1 was happening. I lost sight of the helicopters and made a choice to delay my rotation hoping not to collide with them. The whole incident had the most unnerving affect on me as the PF because it almost completely distracted me from doing the only job that mattered which was flying the plane. I was so focused on the what-ifs of the situation that I would have been at a serious disadvantage had we experienced an engine failure or some other malady. As we climbed away from the runway I tried to refocus and push the incident out of my immediate thoughts. The Captain made a remark to tower when were handed off to departure and the reply from tower was 'visual separation'. This incident really shook me up.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.