Narrative:

I assumed the tower local and controller in charge position following the position relief briefing. The previous controller briefed me on the traffic; particularly one that he had tagged up on the radar display - aircraft X. This call sign was displayed onto the limited VFR-1200 beacon code data block by the other controller. The position identifier on the radar display for dpa local control position is 7. Aircraft X was transitioning through the class D from west to east to the [off airport location] approximately 5 miles southeast of dpa. It is not typically routine to tag VFR aircraft transitioning through the class D; some controllers do it some don't. After reviewing the radar data on falcon; it shows aircraft Y was on a right downwind for ord descending out of 6000 feet approximately 5-6 miles southeast of dpa airport. The aircraft Y data block had the position identifier of Z. The playback showed that aircraft X and aircraft Y data blocks passed over on top of one another. The falcon playback shows aircraft Y with a full data block although the actual radar displays a limited data block instead. Another thing I noticed on the falcon playback; it did not show the aircraft X data block going into a suspended/coast mode which I am almost certain it did. In the recent past C90 and its satellite facilities have upgraded from ARTS III radar systems to stars radar systems. Since then we have had numerous occasions where data tags from arriving aircraft would go into a suspended/coast mode and just linger on the display.as stated above I am almost certain that aircraft X's data block had gone into coast mode (not tracked). To get aircraft X data block to drop I used the 'terminate control' button on the stars keyboard and then used the slew ball to drop the track. I believe what happened next is; the stars displayed an error message; still thinking that aircraft X's data block had gone into a coast/suspended mode I then used the 'terminated control space ok' function to delete it for sure. Still not realizing that the aircraft Y limited data block with the position identifier of Z was also in the very near vicinity of the aircraft X tag whose identifier of 7 and I inadvertently deleted the aircraft Y limited data block by mistake.I would never delete or drop a data block that wasn't under my control. I should have been more cautious in my attempt to delete aircraft X's data tag. I should have used the keyboard method by which you use the terminate control button but instead of the slew ball to identify the track.

Google
 

Original NASA ASRS Text

Title: DPA Tower Controller inadvertently deleted the Radar Data Tag of an aircraft in the TRACON's airspace.

Narrative: I assumed the Tower Local and Controller In Charge position following the position relief briefing. The previous controller briefed me on the traffic; particularly one that he had tagged up on the RADAR display - Aircraft X. This call sign was displayed onto the limited VFR-1200 beacon code data block by the other controller. The position identifier on the radar display for DPA Local Control position is 7. Aircraft X was transitioning through the Class D from west to east to the [off airport location] approximately 5 miles southeast of DPA. It is not typically routine to tag VFR aircraft transitioning through the class D; some controllers do it some don't. After reviewing the Radar data on FALCON; it shows Aircraft Y was on a right downwind for ORD descending out of 6000 feet approximately 5-6 miles southeast of DPA airport. The Aircraft Y data block had the position identifier of Z. The playback showed that Aircraft X and Aircraft Y data blocks passed over on top of one another. The FALCON playback shows Aircraft Y with a full data block although the actual radar displays a limited data block instead. Another thing I noticed on the FALCON playback; it did not show the Aircraft X data block going into a Suspended/Coast mode which I am almost certain it did. In the recent past C90 and its satellite facilities have upgraded from ARTS III radar systems to STARS radar systems. Since then we have had numerous occasions where data tags from arriving aircraft would go into a suspended/coast mode and just linger on the display.As stated above I am almost certain that Aircraft X's data block had gone into Coast Mode (not tracked). To get Aircraft X data block to drop I used the 'Terminate Control' button on the STARS keyboard and then used the slew ball to drop the track. I believe what happened next is; the STARS displayed an error message; still thinking that Aircraft X's data block had gone into a coast/suspended mode I then used the 'Terminated Control space OK' function to delete it for sure. Still not realizing that the Aircraft Y limited data block with the position identifier of Z was also in the very near vicinity of the Aircraft X tag whose identifier of 7 and I inadvertently deleted the Aircraft Y limited data block by mistake.I would never delete or drop a data block that wasn't under my control. I should have been more cautious in my attempt to delete Aircraft X's data tag. I should have used the keyboard method by which you use the Terminate Control button but instead of the slew ball to identify the track.

Data retrieved from NASA's ASRS site 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.