ZSE controller described a confused data block event when a VFR aircraft cycling through an IFR arri...

Narrative:

Aircraft X VFR was flashing hand off to sector 6 and data was flashing as well. Associated with the target was a aircraft Y data tag. From talking to sea approach; apparently aircraft X had cycled through the aircraft Y assigned code and since aircraft Y had just touched down and was not tracking anymore that data tag jumped onto aircraft X. When aircraft X finally got to his assigned code we had two data tags on the same target. I could see where the aircraft Y data tag was showing aircraft X's altitude and aircraft X's altitude was not showing. Tried to move the aircraft Y data block but it was not my control. Aircraft X finally went into coast mode and I could not get it to track back up because of aircraft Y. Had to remove strips on aircraft Y in order to get aircraft X to track normal. Having two data blocks tracking one target is just flat out wrong; unsafe and should never be allowed to happen. Recommendation; change the parameters to prevent this type of occurrence from happening in the future.

Original NASA ASRS Text

Title: ZSE Controller described a confused Data Block event when a VFR aircraft cycling through an IFR arrival's beacon code resulted in erroneous information being displayed.

Narrative: Aircraft X VFR was flashing hand off to Sector 6 and DATA was flashing as well. Associated with the target was a Aircraft Y Data tag. From talking to SEA Approach; apparently Aircraft X had cycled through the Aircraft Y assigned code and since Aircraft Y had just touched down and was not tracking anymore that data tag jumped onto Aircraft X. When Aircraft X finally got to his assigned code we had two data tags on the same target. I could see where the Aircraft Y data tag was showing Aircraft X's altitude and Aircraft X's altitude was not showing. Tried to move the Aircraft Y Data Block but it was not my control. Aircraft X finally went into coast mode and I could not get it to track back up because of Aircraft Y. Had to remove strips on Aircraft Y in order to get Aircraft X to track normal. Having two data blocks tracking one target is just flat out wrong; unsafe and should never be allowed to happen. Recommendation; change the parameters to prevent this type of occurrence from happening in the future.

Data retrieved from NASA's ASRS site as of April 2012 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	972318
Time
Date	201109
Local Time Of Day	0601-1200
Place
Locale Reference	ZSE.ARTCC
State Reference	WA
Aircraft 1
Make Model Name	PA-44 Seminole/Turbo Seminole
Flight Phase	Cruise
Route In Use	None
Flight Plan	VFR
Person 1
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types

ZSE controller described a confused data block event when a VFR aircraft cycling through an IFR arrival's beacon code resulted in erroneous information being displayed.