ATC equipment problem radar data tag drop.

Attributes
ACN	266157
Time
Date	199403
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : sfo
State Reference	CA
Environment
Flight Conditions	VMC
Aircraft 1
Controlling Facilities	tracon : oak tower : sfo artcc : zse
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : local
Qualification	controller : radar
ASRS Report	266157
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
Navigational Aid	Unspecified

Narrative:

The ARTS data tags on aircraft landing sfo disappear on about a 7 mi final and may or may not reappear on a 2 mi final. Occasionally the primary and secondary radar returns disappear as well. This condition has been happening for at least 2 weeks and airways facilities have not fixed the problem. It is true that the vast majority of tags disappearing occurred when pilots turned off their xponders as a result of TCASII alerts fix the problem of pilots turning off their xponders due to TCASII. This is the action that initiates the sequence of disappearing tags. There has been substantial work done to investigate the reason that the tags do not 'coast' as the ARTS system is designed to do. I don't believe that the reason for the tags not coasting has been discovered, let alone a fix for that problem. Callback conversation with reporter revealed the following information: reporter stated FAA management and maintenance had investigated a ucr and declared the dropped data tag problem solved. Reporter stated data tags are not going into coasting mode, which gives the controller some warning the data tag is going to drop off the radar scope. When the tag drops due to lack of target resolution side by aircraft appear as 1 target. This happens during side-by visual approach's.

Original NASA ASRS Text

Title: ATC EQUIP PROB RADAR DATA TAG DROP.

Narrative: THE ARTS DATA TAGS ON ACFT LNDG SFO DISAPPEAR ON ABOUT A 7 MI FINAL AND MAY OR MAY NOT REAPPEAR ON A 2 MI FINAL. OCCASIONALLY THE PRIMARY AND SECONDARY RADAR RETURNS DISAPPEAR AS WELL. THIS CONDITION HAS BEEN HAPPENING FOR AT LEAST 2 WEEKS AND AIRWAYS FACILITIES HAVE NOT FIXED THE PROB. IT IS TRUE THAT THE VAST MAJORITY OF TAGS DISAPPEARING OCCURRED WHEN PLTS TURNED OFF THEIR XPONDERS AS A RESULT OF TCASII ALERTS FIX THE PROB OF PLTS TURNING OFF THEIR XPONDERS DUE TO TCASII. THIS IS THE ACTION THAT INITIATES THE SEQUENCE OF DISAPPEARING TAGS. THERE HAS BEEN SUBSTANTIAL WORK DONE TO INVESTIGATE THE REASON THAT THE TAGS DO NOT 'COAST' AS THE ARTS SYS IS DESIGNED TO DO. I DON'T BELIEVE THAT THE REASON FOR THE TAGS NOT COASTING HAS BEEN DISCOVERED, LET ALONE A FIX FOR THAT PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED FAA MGMNT AND MAINT HAD INVESTIGATED A UCR AND DECLARED THE DROPPED DATA TAG PROB SOLVED. RPTR STATED DATA TAGS ARE NOT GOING INTO COASTING MODE, WHICH GIVES THE CTLR SOME WARNING THE DATA TAG IS GOING TO DROP OFF THE RADAR SCOPE. WHEN THE TAG DROPS DUE TO LACK OF TARGET RESOLUTION SIDE BY ACFT APPEAR AS 1 TARGET. THIS HAPPENS DURING SIDE-BY VISUAL APCH'S.

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.