Narrative:

On jan/1992 at washington center air carrier X was going nebound to phl and air carrier Y swbound was at FL350. The sector I was working had just been split out from the low side. I now own FL350 and above. The sector below handed off all of the appropriate aircraft in my altitude stratum and I started to sequence all of my strips. While in the meantime, a data tag dropped off the radar scope (air carrier Y) and then not knowing about the missing data tag I descended air carrier X to FL330. At that point is when conflict alert went off. So I stopped air carrier X descent and turned him nwbound and climbed him again, after clear of confliction I put air carrier X back on course. This incident happened because the full data block key was not depressed so when taking the handoff, the sector appeared to operate normal but in fact after 4 mins the aircraft tag drops off the radar scope making him unaware of the aircraft. This button should not be an option to select, it should be kept depressed a tall times. It should be made to be locked in the on position at all times not allowing it to be depressed. This was and error caused by equipment.

Related reports:

Google
 

Original NASA ASRS Text

Title: DATA TAG DROPS OFF SCOPE CAUSING CTLR TO FORGET ABOUT ACFT AND INADVERTENTLY DSNDED ANOTHER ACFT THROUGH OCCUPIED ALT RESULTING IN LTSS.

Narrative: ON JAN/1992 AT WASHINGTON CTR ACR X WAS GOING NEBOUND TO PHL AND ACR Y SWBOUND WAS AT FL350. THE SECTOR I WAS WORKING HAD JUST BEEN SPLIT OUT FROM THE LOW SIDE. I NOW OWN FL350 AND ABOVE. THE SECTOR BELOW HANDED OFF ALL OF THE APPROPRIATE ACFT IN MY ALT STRATUM AND I STARTED TO SEQUENCE ALL OF MY STRIPS. WHILE IN THE MEANTIME, A DATA TAG DROPPED OFF THE RADAR SCOPE (ACR Y) AND THEN NOT KNOWING ABOUT THE MISSING DATA TAG I DSNDED ACR X TO FL330. AT THAT POINT IS WHEN CONFLICT ALERT WENT OFF. SO I STOPPED ACR X DSCNT AND TURNED HIM NWBOUND AND CLBED HIM AGAIN, AFTER CLR OF CONFLICTION I PUT ACR X BACK ON COURSE. THIS INCIDENT HAPPENED BECAUSE THE FULL DATA BLOCK KEY WAS NOT DEPRESSED SO WHEN TAKING THE HDOF, THE SECTOR APPEARED TO OPERATE NORMAL BUT IN FACT AFTER 4 MINS THE ACFT TAG DROPS OFF THE RADAR SCOPE MAKING HIM UNAWARE OF THE ACFT. THIS BUTTON SHOULD NOT BE AN OPTION TO SELECT, IT SHOULD BE KEPT DEPRESSED A TALL TIMES. IT SHOULD BE MADE TO BE LOCKED IN THE ON POS AT ALL TIMES NOT ALLOWING IT TO BE DEPRESSED. THIS WAS AND ERROR CAUSED BY EQUIP.

Data retrieved from NASA's ASRS site as of July 2007 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.