PA-28R Cherokee Arrow All Series
Air Traffic Control Developmental
Situational Awareness
Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Human Factors; Procedure
I was working Local Control and cleared a PA-28 for takeoff from Runway X on the appropriate IFR heading for eastbound prop departures of 050. Upon PA-28's departure; a Cessna 182 checked on to Tower frequency requesting departure from Runway X. The C182 is a local aircraft that typically departs VFR from this airport and I had not noticed an IFR strip belonging to him in front of me prior to his departure. I departed the C182 from Runway X believing the C182 was a VFR aircraft and there was enough separation between the PA-28 and C182. The PA-28 was given frequency change to Departure Control. At approximately 1 mile off the departure end of Runway X; the C182's IFR tagged appeared on the RADAR. I promptly assigned the C182 the appropriate heading for eastbound IFR prop departures of 050. After observing PA-28 had a 20 knot faster speed than the C182; and what I believed to be 3 NM separation between the two aircraft; I gave frequency change to Departure Control. Approach notified ZZZ of loss of separation between the PA-28 and the C182.  I would make a better effort to check my workspace for IFR strips more thoroughly. We have no strip bay on local position. This can cause misplaced and/or unobserved IFR departure strips.
I was CIC and I was planning the break rotation; when Local Control departed an IFR aircraft; a PA-28; off of Runway X on a heading of 050. LC then launched a C182; who often departs VFR; thinking the aircraft was VFR off of Runway X and then I hear LC say; 'Oh he was IFR.' I look up and see the C182 tagged up about 1 Mile NE of the airport. I immediately walked over to LC and told them to watch the speeds on the aircraft as the [aircraft were a] C182 and a PA-28R. We looked at the mileage and it appeared to be three miles and the Aero was moving 20 knots faster than the C182 flight which would be increasing the distance. LC then switched the C182 flight. About an hour later Approach called and advised me that separation had been lost.  I would recommend to check all aircraft for an IFR flight plan and to not assume that an aircraft is VFR.
Tower Controller experienced a loss of separation event when failing to note a second departure was IFR assuming VFR status as was usually the case for this airport based aircraft.