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Switchover problem in the ZDV host computer caused the pvd's (radar screens) to freeze up during a busy period. Change to darc was accomplished, but darc was not current with all the traffic in the system. Outage lasted 6 mins then returned to normal. Data is being analyzed to determine the problem.
| Attributes | |
| ACN | 336393 |
| Time | |
| Date | 199605 |
| Day | Wed |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : den |
| State Reference | CO |
| Altitude | agl bound lower : 0 agl bound upper : 0 |
| Person 1 | |
| Affiliation | government : faa |
| Function | other personnel other |
| Qualification | controller : radar |
| ASRS Report | 336393 |
| Events | |
| Anomaly | other anomaly other |
| Independent Detector | other controllera |
| Resolutory Action | other |
| Consequence | faa : investigated |
| Supplementary | |
| Primary Problem | Navigational Facility |
| Air Traffic Incident | other |
| Situations | |
| ATC Facility | other physical facility |
Narrative:
At XA35 a switchover failure in the host computer caused the pvd's (radar screens) to freeze up. Immediately, air traffic controllers started to change to the backup darc computer. However, the darc system did not stay current with the host system. The effect of these errors were that the radar displays from the main host system were frozen, and not all data blocks for aircraft were displayed in the backup darc system. There were 290 tracks (aircraft) in ZDV at the time of the occurrence. Controllers were left with the main system frozen, unusable, and the backup system provided limited or no data blocks on aircraft which they were working during one of the busiest times of the day. The host computer was returned to service 6 mins later at XA41. The system is still being analyzed to determine why the switchover failure occurred, and why the backup system was not current.
Original NASA ASRS Text
Title: SWITCHOVER PROB IN THE ZDV HOST COMPUTER CAUSED THE PVD'S (RADAR SCREENS) TO FREEZE UP DURING A BUSY PERIOD. CHANGE TO DARC WAS ACCOMPLISHED, BUT DARC WAS NOT CURRENT WITH ALL THE TFC IN THE SYS. OUTAGE LASTED 6 MINS THEN RETURNED TO NORMAL. DATA IS BEING ANALYZED TO DETERMINE THE PROB.
Narrative: AT XA35 A SWITCHOVER FAILURE IN THE HOST COMPUTER CAUSED THE PVD'S (RADAR SCREENS) TO FREEZE UP. IMMEDIATELY, AIR TFC CTLRS STARTED TO CHANGE TO THE BACKUP DARC COMPUTER. HOWEVER, THE DARC SYS DID NOT STAY CURRENT WITH THE HOST SYS. THE EFFECT OF THESE ERRORS WERE THAT THE RADAR DISPLAYS FROM THE MAIN HOST SYS WERE FROZEN, AND NOT ALL DATA BLOCKS FOR ACFT WERE DISPLAYED IN THE BACKUP DARC SYS. THERE WERE 290 TRACKS (ACFT) IN ZDV AT THE TIME OF THE OCCURRENCE. CTLRS WERE LEFT WITH THE MAIN SYS FROZEN, UNUSABLE, AND THE BACKUP SYS PROVIDED LIMITED OR NO DATA BLOCKS ON ACFT WHICH THEY WERE WORKING DURING ONE OF THE BUSIEST TIMES OF THE DAY. THE HOST COMPUTER WAS RETURNED TO SVC 6 MINS LATER AT XA41. THE SYS IS STILL BEING ANALYZED TO DETERMINE WHY THE SWITCHOVER FAILURE OCCURRED, AND WHY THE BACKUP SYS WAS NOT CURRENT.
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.