Tower controller experienced a loss of separation event when failing to note a second departure was ...

Narrative:

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.

Original NASA ASRS Text

Title: 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.

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1116717
Time
Date	201309
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Tower
State Reference	US
Aircraft 1
Make Model Name	PA-28R Cherokee Arrow All Series
Flight Phase	Initial Climb
Route In Use	Vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Skylane 182/RG Turbo Skylane/RG
Flight Phase	Initial Climb
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Local
Qualification	Air Traffic Control Developmental
Person 2
Function	Supervisor / CIC
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	Deviation - Procedural Published Material / Policy

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.