Medium Transport
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 8.0
Situational Awareness
ATC Issue All Types; Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Airport; Human Factors; Procedure; Staffing
At the time I was on Ground Control/Controller-in-Charge working on a flight plan.  Aircraft X called me; exiting wanting to go to the gate.  I started to issue instructions and looked up from the computer to see the aircraft just exiting the runway at the taxiway as I was speaking to him.  I then noticed a second aircraft just about to rotate prior to a taxiway.  It looked pretty bad but I thought maybe I'd missed something; or saw something wrong; or that some kind of anticipated separation was being used by the Local Controller.  None of the aircraft said anything; and I felt like I missed everything but the very last second.  But as I thought more and more about it; it just seemed less and less likely; it felt very wrong all that night; and kept eating at me.  So the following day I spent my breaks reviewing tapes and radar replays.  I put together a timeline to see if anticipated separation could have been possible.Based on timestamps from recording/replays; it appears the Local Control was trying to put Aircraft Y in position with Aircraft X still on short final (luckily another aircraft stepped on the transmission; possibly preventing that). A little while later; Local Control clears Aircraft Y for takeoff (from holding in position) and then 34 seconds later instructs Aircraft X to clear the runway.  I saw Aircraft X clearing 17 seconds after that point.  I don't think you can anticipate separation 51 seconds later (or even 34 seconds going by recording timestamps).  But if even by some miracle he didn't start his roll until Aircraft X was clear; he went from dead stop on the runway to being acquired on radar in 17 seconds; and then switched to departure ten seconds after that.  I believe the Local Controller completely forgot about the arrival aircraft.Honestly; I don't know what to do to prevent this in the future.  This was straight up controller error.  I think everybody has lapses in judgement/memory from time to time; but with the Local Controller involved here; it happens on a daily; and sometimes hourly basis.  I think the event should be fully investigated.  I am shocked that none of the aircraft involved said or did anything as the events were unfolding.  I wish that I could have given the situation my full attention (which isn't always possible working multiple positions combined).  I would definitely have instructed the Local controller to cancel the take-off clearance; if I were aware of what was happening at the time.
A Tower Controller in Charge (CIC) was also working Ground Control and Flight Data. While entering Flight Data an aircraft called exiting the runway. The CIC observed an aircraft departing behind the arrival with less than required separation. The next day the CIC reviewed time stamped tapes and confirmed their suspicion. The reporter states that the Controller working local control has errors like this on a daily basis.