B737 Undifferentiated or Other Model
Flight Crew Last 90 Days 150; Flight Crew Total 8899; Flight Crew Type 3167
Situational Awareness; Confusion
ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Flight Crew Requested ATC Assistance / Clarification
Human Factors; Manuals; Procedure
In EUG using no Tower communications due to early morning the Tower was not open. Got ATC clearance from Center; void if not off by XA:57. We were rolling down the runway with XA:57 on the UTC clock. ATC starts to call us saying they haven't heard from us and we are passed our void time. I look down at the clock and it still says XA:57. We lifted off and the aircraft clock still showed XA:57. My question is if we are told a clearance is void if not off by XA:57; does that mean we have to be airborne by XA:56 or is it like I think XA:57? To me it would be the clock showing XA:58; that would be the void time. Also our clocks don't show the time in seconds so starting a takeoff with the clock showing us right at the minute before our clearance voids seems appropriateOur clocks are synced to GPS so I think they are accurate. I obviously wasn't going to high speed abort a takeoff due to ATC calling me saying my clearance was void; but it was distracting. We were transmitting on UNICOM but monitoring Seattle center on takeoff. Also I am certain my clock still showed XA:57 at liftoff so why does ACARS show XA:58. Does ACARS round up?
B737 Captain reported ATC told them they took off after their clearance void time.