British Aerospace Undifferentiated or Other Model
Air Traffic Control Developmental
Situational Awareness; Time Pressure
ATC Issue All Types; Conflict Airborne Conflict; Ground Incursion Runway; Inflight Event / Encounter Fuel Issue
Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition
Human Factors
I was in the Local Control position.   Aircraft Y was in the VFR traffic pattern doing touch and goes/low approaches.   Aircraft X was inbound on a visual approach to Runway 23L.  Aircraft Y was issued a go around due to runway separation on a prior aircraft not involved in this event.  On the go Aircraft Y was given right closed traffic and told to extend his download.  Aircraft Y declared minimum fuel at this time.  Traffic to follow on Aircraft X was given to Aircraft Y to follow.  Aircraft X was on a 3 or 4 mile final at this time.  Aircraft Y flew a mile downwind and then declared emergency fuel.  Aircraft X was in a critical phase of flight short final and I allowed him to land but advised him minimal time on the runway and that the aircraft behind him must land.  Aircraft Y was told to follow Aircraft X and cleared to land.  Aircraft Y turned directly behind Aircraft X.  Aircraft X was given another expedite request off of the runway.  Aircraft X was turning off at the A4 intersection as Aircraft Y crossed the landing threshold. The time from the declaration of minimum fuel to emergency fuel was very short.  The traffic to follow would not require Aircraft Y any undue delay.  Had emergency fuel been called earlier then the citation could have been sent around before his critical phase of flight; allowing the then priority emergency aircraft a clean runway.
Tower Controller reported a runway incursion involving a Citation and a UAV.