Less than standard separation between air carrier and GA small transport. Operational error.

Attributes
ACN	173764
Time
Date	199103
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : jax
State Reference	FL
Altitude	msl bound lower : 10000 msl bound upper : 10000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zjx tracon : jax artcc : zla
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Transport, Low Wing, 2 Recip Eng
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
ASRS Report	173764
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : less severe conflict : airborne less severe non adherence : required legal separation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 3000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error Inter Facility Coordination Failure

Narrative:

Small transport Y was an overflt to fxe, my flight progress strip indicated its altitude as 9000'. Air carrier X called me at 1200' landing jax, I descended X to 10000' and told him to proceed to the dinns outer compass locator for a visibility approach. The air carrier X was on a converging course with small transport Y and was issued traffic several times. Jax ARTCC then called to see if I was in contact with aircraft Y. I wasn't and they said to consider it NORDO. Air carrier X was issued traffic again. After the targets diverged air carrier X advised me the traffic was at 10000' and they turned to avoid it. I called jax ARTCC to check on aircraft Y's altitude it was assigned 10000', its mode C had been erroneous and they had instructed it to turn it off. There obviously was a breakdown in the transmission of flight data. After landing air carrier X captain called and said he had the traffic on his TCAS ii and had avoided it by turning his autoplt 25 degrees right. Supplemental information from acn 173916. We were given a descent to 10000' and issued traffic at 1 O'clock at 9000'. We had a target (TA) traffic advisory on our TCAS but no altitude readout. When we showed approximately 2 mi from the traffic we finally picked him up visly at our altitude. We were then level at 10000'. We soon determined that on our present heading we would not miss the aircraft, so we turned approximately 25 degree to the right so as to pass behind the aircraft, which then passed in front of us from right to left. We were able to complete the turn on the autoplt and passed comfortably behind small transport Y. We estimate we probably passed 3000' behind him. We advised approach control of our turn and the altitude of the traffic. Approach control stated that he was supposed to be at 9000'. After landing at jacksonville, with no further incident, I called jacksonville center and talked with the supervisor who said that aircraft Y had been advised earlier of an altitude readout error and was asked to turn mode C off.

Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION BETWEEN ACR AND GA SMT. OPERATIONAL ERROR.

Narrative: SMT Y WAS AN OVERFLT TO FXE, MY FLT PROGRESS STRIP INDICATED ITS ALT AS 9000'. ACR X CALLED ME AT 1200' LNDG JAX, I DSNDED X TO 10000' AND TOLD HIM TO PROCEED TO THE DINNS OUTER COMPASS LOCATOR FOR A VIS APCH. THE ACR X WAS ON A CONVERGING COURSE WITH SMT Y AND WAS ISSUED TFC SEVERAL TIMES. JAX ARTCC THEN CALLED TO SEE IF I WAS IN CONTACT WITH ACFT Y. I WASN'T AND THEY SAID TO CONSIDER IT NORDO. ACR X WAS ISSUED TFC AGAIN. AFTER THE TARGETS DIVERGED ACR X ADVISED ME THE TFC WAS AT 10000' AND THEY TURNED TO AVOID IT. I CALLED JAX ARTCC TO CHK ON ACFT Y'S ALT IT WAS ASSIGNED 10000', ITS MODE C HAD BEEN ERRONEOUS AND THEY HAD INSTRUCTED IT TO TURN IT OFF. THERE OBVIOUSLY WAS A BREAKDOWN IN THE XMISSION OF FLT DATA. AFTER LNDG ACR X CAPT CALLED AND SAID HE HAD THE TFC ON HIS TCAS II AND HAD AVOIDED IT BY TURNING HIS AUTOPLT 25 DEGS R. SUPPLEMENTAL INFO FROM ACN 173916. WE WERE GIVEN A DSNT TO 10000' AND ISSUED TFC AT 1 O'CLOCK AT 9000'. WE HAD A TARGET (TA) TFC ADVISORY ON OUR TCAS BUT NO ALT READOUT. WHEN WE SHOWED APPROX 2 MI FROM THE TFC WE FINALLY PICKED HIM UP VISLY AT OUR ALT. WE WERE THEN LEVEL AT 10000'. WE SOON DETERMINED THAT ON OUR PRESENT HDG WE WOULD NOT MISS THE ACFT, SO WE TURNED APPROX 25 DEG TO THE R SO AS TO PASS BEHIND THE ACFT, WHICH THEN PASSED IN FRONT OF US FROM R TO L. WE WERE ABLE TO COMPLETE THE TURN ON THE AUTOPLT AND PASSED COMFORTABLY BEHIND SMT Y. WE ESTIMATE WE PROBABLY PASSED 3000' BEHIND HIM. WE ADVISED APCH CTL OF OUR TURN AND THE ALT OF THE TFC. APCH CTL STATED THAT HE WAS SUPPOSED TO BE AT 9000'. AFTER LNDG AT JACKSONVILLE, WITH NO FURTHER INCIDENT, I CALLED JACKSONVILLE CTR AND TALKED WITH THE SUPVR WHO SAID THAT ACFT Y HAD BEEN ADVISED EARLIER OF AN ALT READOUT ERROR AND WAS ASKED TO TURN MODE C OFF.

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.