ATC facility experiences intermittent mode C ommision on altitude readout.

Attributes
ACN	207620
Time
Date	199204
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : aus
State Reference	TX
Altitude	msl bound lower : 2000 msl bound upper : 6000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : aus
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Retractable Gear
Flight Phase	climbout : intermediate altitude
Route In Use	departure other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : departure
Qualification	controller : radar
Experience	controller radar : 4
ASRS Report	207620
Person 2
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument
Events
Anomaly	other anomaly other
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	none taken : unable
Consequence	Other
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	other
Situations
ATC Facility	other physical facility

Narrative:

Austin approach/departure control has had an ASR-9 radar installed, and since that radar has been commissioned, there have been numerous instances where an aircraft's 'mode C' altitude readout is not displayed, even though the aircraft's transponder is working properly (mode C verified by adjacent facilities). An IFR small aircraft departed aus nwbound on V76. Between 5 northwest of aus and 15 northwest of aus, no mode C was displayed on my ARTS iia data block, although houston center was receiving the small aircraft's readout the entire time. When this mode C failure happened on other occasions, changing secondary radar channels (beacon) immediately brings the correct mode C readout back. This is not confirmed to either channel 1 or channel 2. Both channels have had this problem and it corrects when switching to the channel not in use. All aircraft on the radar scope do not drop their mode C, usually it is just one.

Original NASA ASRS Text

Title: ATC FACILITY EXPERIENCES INTERMITTENT MODE C OMMISION ON ALT READOUT.

Narrative: AUSTIN APCH/DEP CTL HAS HAD AN ASR-9 RADAR INSTALLED, AND SINCE THAT RADAR HAS BEEN COMMISSIONED, THERE HAVE BEEN NUMEROUS INSTANCES WHERE AN ACFT'S 'MODE C' ALT READOUT IS NOT DISPLAYED, EVEN THOUGH THE ACFT'S TRANSPONDER IS WORKING PROPERLY (MODE C VERIFIED BY ADJACENT FACILITIES). AN IFR SMA DEPARTED AUS NWBOUND ON V76. BTWN 5 NW OF AUS AND 15 NW OF AUS, NO MODE C WAS DISPLAYED ON MY ARTS IIA DATA BLOCK, ALTHOUGH HOUSTON CTR WAS RECEIVING THE SMA'S READOUT THE ENTIRE TIME. WHEN THIS MODE C FAILURE HAPPENED ON OTHER OCCASIONS, CHANGING SECONDARY RADAR CHANNELS (BEACON) IMMEDIATELY BRINGS THE CORRECT MODE C READOUT BACK. THIS IS NOT CONFIRMED TO EITHER CHANNEL 1 OR CHANNEL 2. BOTH CHANNELS HAVE HAD THIS PROBLEM AND IT CORRECTS WHEN SWITCHING TO THE CHANNEL NOT IN USE. ALL ACFT ON THE RADAR SCOPE DO NOT DROP THEIR MODE C, USUALLY IT IS JUST ONE.

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.