Reporter claims radar display map shifted as a result of a slew ball malfunction.

Attributes
ACN	399485
Time
Date	199804
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zau
State Reference	IL
Environment
Flight Conditions	IMC
Light	Daylight
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller non radar : 7 controller radar : 4
ASRS Report	399485
Person 2
Affiliation	company : air carrier
Function	oversight : supervisor
Qualification	controller : radar
Events
Anomaly	other anomaly other
Independent Detector	other controllera
Resolutory Action	none taken : unable
Consequence	faa : investigated
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	other
Situations
ATC Facility	other physical facility

Narrative:

I was working the burlon (super high) sector. Traffic was light. Suddenly, as I typed an entry into the computer, my radar display map moved about 85 mi to the south. This caused at least 1/2 of my airspace to 'drop off' my radar scope. When I reported this to my supervisor, I was told that it happened because a slew ball 'some place froze up.' 'not to worry, this will happen occasionally but it's not a major problem.' this time it did not cause a problem because traffic was light. If traffic is heavy or complex when this happens, the results could be catastrophic. Callback conversation with reporter revealed the following information: reporter stated that the radar display presentation, and not just the map, shifts from the center position and indicated the problem with the slew ball has not been corrected. Reporter alleges maintenance personnel have acknowledged that the shifting happens sometimes and that the controller will have to realign their displays. Reporter indicated a ucr report will be filed.

Original NASA ASRS Text

Title: RPTR CLAIMS RADAR DISPLAY MAP SHIFTED AS A RESULT OF A SLEW BALL MALFUNCTION.

Narrative: I WAS WORKING THE BURLON (SUPER HIGH) SECTOR. TFC WAS LIGHT. SUDDENLY, AS I TYPED AN ENTRY INTO THE COMPUTER, MY RADAR DISPLAY MAP MOVED ABOUT 85 MI TO THE S. THIS CAUSED AT LEAST 1/2 OF MY AIRSPACE TO 'DROP OFF' MY RADAR SCOPE. WHEN I RPTED THIS TO MY SUPVR, I WAS TOLD THAT IT HAPPENED BECAUSE A SLEW BALL 'SOME PLACE FROZE UP.' 'NOT TO WORRY, THIS WILL HAPPEN OCCASIONALLY BUT IT'S NOT A MAJOR PROB.' THIS TIME IT DID NOT CAUSE A PROB BECAUSE TFC WAS LIGHT. IF TFC IS HVY OR COMPLEX WHEN THIS HAPPENS, THE RESULTS COULD BE CATASTROPHIC. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THE RADAR DISPLAY PRESENTATION, AND NOT JUST THE MAP, SHIFTS FROM THE CTR POS AND INDICATED THE PROB WITH THE SLEW BALL HAS NOT BEEN CORRECTED. RPTR ALLEGES MAINT PERSONNEL HAVE ACKNOWLEDGED THAT THE SHIFTING HAPPENS SOMETIMES AND THAT THE CTLR WILL HAVE TO REALIGN THEIR DISPLAYS. RPTR INDICATED A UCR RPT WILL BE FILED.

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.