Air Carrier departure from a foreign airport initiated a take off when reportedly ATC issued 'line up and wait' followed by 'after take off fly heading 030'; which was interpreted as a take off clearance.
Synopsis
Air Carrier departure from a foreign airport initiated a take off when reportedly ATC issued 'line up and wait' followed by 'after take off fly heading 030'; which was interpreted as a take off clearance.
Narrative
We pushed off the gate with low visibility and fog. First Officer was in the right seat and another First Officer was on the jump seat. The ATIS was reporting visibility of less than 800 meters and Low Visibility Procedures in Progress. Our departure clearance was given to us verbally because our ACARS request was rejected. We were cleared via Runway 09. We started our engines completed our check lists and called for taxi clearance. Ground Control cleared us to taxi to Runway 09 via Taxiway B. Ground reported that the RVR for Runway 09 was 300 meters at all 3 positions. Before releasing the brakes we all three verified our route and how many intersections we would pass prior to reaching the end of Runway 09; which was at Taxiways B and N5. When we reached N5 we stopped and mentioned there were red stop bar lights illuminated; for not entering the end of the runway. We contacted Tower and told them we were ready for take off; to which Tower replied; Runway 09; line up and wait. At that time the red stop bars were turned off. When we were taxiing onto N5 to line up and wait I thought I hear Tower say [to us]; new departure clearance; CLEARED FOR TAKEOFF; FLY HEADING OF 030 DEGREES; CLIMB TO FL60. The First Officer read back the clearance. I then briefed our clearance as; I'm flying; fly heading 030 and climb to FL60. I then asked if we were cleared for take off to which the First Officer said yes; clear to go. The other First Officer did not confirm nor dispute the take off clearance. We lined up the aircraft on the center line lights and advanced the thrust levers and took off. At 1;500 FT Tower called and said; 'Are you aware you took off without clearance? The First Officer replied; 'Negative; you cleared us for take off and I acknowledge. Tower responded; 'Negative; I did not clear you for take off; I only gave you a new departure instructions. The First Officer responded; 'Well; we are already airborne but we apologize.' All three of us instantly realized how grave of an error we just committed! Low visibility and no take off clearance could have been disastrous! We all agreed that we thought we had heard 'CLEARED FOR TAKEOFF;' but now question what the Tower had said. I have always been very firm that anytime all three pilots are not 100% positive on an ATC clearance we ALWAYS confirm. Whether it is taxi instruction; take off clearance; frequency change; altitude change or whatever; I always insist on verifying. The question is why didn't we this time? The answer is there is no excuse. I do however believe the break down happen for a couple of reasons. Instructions from the Tower were in accented English; and he used the word take off. I believe that if the Controller had used the verbiage 'AFTER DEPARTURE' rather than 'AFTER TAKEOFF' we would not have misunderstood the clearance. In the future I will insist that if ALL THREE pilots are not positive of a clearance we will verify.
Second reporter narrative
Contributing: Fatigue: I got mediocre sleep prior to this take off. This was the last day of a 6-day. It was my 9th day on the road. This trip was tougher than most. Two legs prior I departed the airport in similar weather conditions headed to the U.S. The leg prior I was in the U.S. for a departure during a snowstorm. We had what seemed like a loft that took about 90 minutes to get airborne; complete with deicing; runway closure; and almost exceeding our holdover time while dealing with a mechanical. That leg ended with a true CAT III landing in Europe complete with a low-vis taxi in. None of the three of us are sure of exactly what the Tower Controller said; but we all know that we heard the word 'take off'; and we all believe that this is what made us think that we were cleared for take off. Instead; and given our position at the time; Tower could have said something more like 'you are cleared to line up and wait; but I have new departure instructions for you; after departure turn left 030' I believe that if he had used verbiage similar to this; this incident would not have occurred. For myself: when the Captain asked; 'are we cleared for takeoff?' I should have just keyed the mike and reconfirmed our clearance with the Tower. We've all heard the discussion about not taking each others' word for stuff like this inside the cockpit; and that the better solution is to query the Controller. Why I did not do this I have no idea; but I obviously should have. And had I; this incident would not have occurred and you would not be reading this report right now. All three of us: Captain could have said: 'confirm with Tower that we are cleared for take off' instead of asking me if we were cleared for takeoff. I could have asked Tower instead of just answering him; as described above. Others could have spoken up and said 'I'm not sure; let's ask' The bottom line is that any one of us could have easily prevented this incident; but none of us did.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.