Narrative:

We were instructed to line up and wait after an md-11 had received take off clearance. As my standard I started my clock for wake-turbulence separation as soon as the [departing md-11] began to roll. After only 1 minute of the md-11 rolling we were given our take off clearance with an initial heading (instead of the RNAV departure). I instructed the tower we still needed 30 sec for wake turbulence separation but that we were clear for takeoff. I omitted the heading portion as at the time I did not comprehend the change as my mind was thinking of why I was given a take off clearance behind a heavy after only 1 min. She replied roger. At approx. The 90 second mark after the 11 rolled we began our roll and I advised the tower. At 400 feet we hit navigate (navigation) on the flight computer plan (fcp) for our departure procedure. Before being switched to departure a different controller came on and chastised me for not telling them when we accepted the line up and wait that we would need more time on the runway than normal. I explained that there is a min separation for wake turbulence that should've been met. He quickly said that they have re-categorized wake turbulence separation-----it's on the ATIS. Upon switching to departure I inquired as to what instruction had been given to us--a heading or navigation departure. He said we should have been given a heading and cleared us to direct the next fix. [The] flight resumed [with] no further complications.the heading assignment was missed by us because it was not expected and I instantly switched thinking modes as we were given a take-off clearance before expected. So I blocked everything out after the early take-off clearance. Simply listening better could have avoided the mistake. However; I was not aware of any other or re-categorization of wake turbulence separation leading me to block out everything she said after the take-off clearance.

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Original NASA ASRS Text

Title: A CRJ-200 Crew were issued a takeoff clearance behind an MD-11 that included a change to runway heading instead of the briefed LNAV departure. The Captain was preoccupied with wake turbulence concerns and missed the runway heading instruction. At 400 feet; he engaged LNAV and the aircraft deviated from runway heading.

Narrative: We were instructed to line up and wait after an MD-11 had received take off clearance. As my standard I started my clock for wake-turbulence separation as soon as the [departing MD-11] began to roll. After only 1 minute of the MD-11 rolling we were given our take off clearance with an initial heading (instead of the RNAV departure). I instructed the tower we still needed 30 sec for wake turbulence separation but that we were clear for takeoff. I omitted the heading portion as at the time I did not comprehend the change as my mind was thinking of why I was given a take off clearance behind a heavy after only 1 min. She replied roger. At approx. the 90 second mark after the 11 rolled we began our roll and I advised the tower. At 400 feet we hit Navigate (NAV) on the Flight Computer Plan (FCP) for our departure procedure. Before being switched to departure a different controller came on and chastised me for not telling them when we accepted the line up and wait that we would need more time on the runway than normal. I explained that there is a min separation for wake turbulence that should've been met. He quickly said that they have re-categorized wake turbulence separation-----it's on the ATIS. Upon switching to departure I inquired as to what instruction had been given to us--a heading or NAV departure. He said we should have been given a heading and cleared us to direct the next fix. [The] flight resumed [with] no further complications.The heading assignment was missed by us because it was not expected and I instantly switched thinking modes as we were given a take-off clearance before expected. So I blocked everything out after the early take-off clearance. Simply listening better could have avoided the mistake. However; I was not aware of any other or re-categorization of wake turbulence separation leading me to block out everything she said after the take-off clearance.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.