Controller claims that radar gives erroneous mode C readouts on targets in various areas.

Attributes
ACN	225365
Time
Date	199211
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : tpa
State Reference	FL
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : tpa
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent : approach
Route In Use	arrival other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller military : 5 controller radar : 10
ASRS Report	225365
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	other anomaly other
Independent Detector	other controllera
Resolutory Action	none taken : unable
Consequence	Other
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	other
Situations
Navigational Aid	Unspecified

Narrative:

Aircraft on the dades arrival continually display erroneous mode C readouts while on descent in the vicinity of the dades intersection. Air carrier X, an medium large transport, TCASII equipped, altitude 13300 ft, leveling at 13000 ft, jumps to a readout of 76900 ft. Air carrier Y, an large transport, level at 13000 ft starts blinking 7600. Air carrier Z, an medium large transport, level at 12000 ft jumps to a readout of 17700 ft. This was reported to airway facilities. Callback conversation with reporter revealed the following information: reporter claims that this is still an ongoing problem. They have 2 radar sites with 1 of them digitized. The erroneous mode C generally happens with every third aircraft. Most controllers have become used to working with this problem, so there has not been any reported incidents. The erroneous altitude usually lasts from 30 seconds to 1 min. Facility is tracking the problem, but it has been ongoing for about 3 yrs. Ucr was filed 4 weeks ago. Reporter states the facility management is good to work with, but they apparently do not think that this is a safety issue. Track dropping was another problem for awhile, however, airway facilities discovered that a new building is being constructed nearby was causing the problem and are in the process of rectifying it now. Reporter also stated that 2 facility 'ARTS problem report' forms have been submitted on this.

Original NASA ASRS Text

Title: CTLR CLAIMS THAT RADAR GIVES ERRONEOUS MODE C READOUTS ON TARGETS IN VARIOUS AREAS.

Narrative: ACFT ON THE DADES ARR CONTINUALLY DISPLAY ERRONEOUS MODE C READOUTS WHILE ON DSCNT IN THE VICINITY OF THE DADES INTXN. ACR X, AN MLG, TCASII EQUIPPED, ALT 13300 FT, LEVELING AT 13000 FT, JUMPS TO A READOUT OF 76900 FT. ACR Y, AN LGT, LEVEL AT 13000 FT STARTS BLINKING 7600. ACR Z, AN MLG, LEVEL AT 12000 FT JUMPS TO A READOUT OF 17700 FT. THIS WAS RPTED TO AIRWAY FACILITIES. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR CLAIMS THAT THIS IS STILL AN ONGOING PROBLEM. THEY HAVE 2 RADAR SITES WITH 1 OF THEM DIGITIZED. THE ERRONEOUS MODE C GENERALLY HAPPENS WITH EVERY THIRD ACFT. MOST CTLRS HAVE BECOME USED TO WORKING WITH THIS PROBLEM, SO THERE HAS NOT BEEN ANY RPTED INCIDENTS. THE ERRONEOUS ALT USUALLY LASTS FROM 30 SECONDS TO 1 MIN. FACILITY IS TRACKING THE PROBLEM, BUT IT HAS BEEN ONGOING FOR ABOUT 3 YRS. UCR WAS FILED 4 WKS AGO. RPTR STATES THE FACILITY MGMNT IS GOOD TO WORK WITH, BUT THEY APPARENTLY DO NOT THINK THAT THIS IS A SAFETY ISSUE. TRACK DROPPING WAS ANOTHER PROBLEM FOR AWHILE, HOWEVER, AIRWAY FACILITIES DISCOVERED THAT A NEW BUILDING IS BEING CONSTRUCTED NEARBY WAS CAUSING THE PROBLEM AND ARE IN THE PROCESS OF RECTIFYING IT NOW. RPTR ALSO STATED THAT 2 FACILITY 'ARTS PROBLEM RPT' FORMS HAVE BEEN SUBMITTED ON THIS.

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.