Loss of radio communication resulted in a near miss.

Attributes
ACN	429608
Time
Date	199903
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : sln.vortac
State Reference	KS
Altitude	msl single value : 33000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdv.artcc
Operator	common carrier : air carrier
Make Model Name	DC-10 10
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zdv.artcc
Operator	common carrier : air carrier
Make Model Name	L-1011 Tri-Star All Series
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 16
ASRS Report	429608
Person 2
Affiliation	government : faa
Function	controller : radar oversight : supervisor
Qualification	controller : radar
Experience	controller non radar : 9 controller radar : 6
ASRS Report	430230
Events
Anomaly	conflict : nmac
Independent Detector	other controllera other controllerb other flight crewa other flight crewb
Resolutory Action	flight crew : took precautionary avoidance action none taken : detected after the fact
Miss Distance	horizontal : 2700
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I was working ARTCC as the radar/interphone controller. I recognized a potential confliction between a widebody transport #1 and a widebody transport #2 at FL330 on converging courses. When the L1011 entered my airspace, communication had not been established. I then called the previous sector to re-atttempt communication xfer, with no success. I then asked my supervisor to initiate a commercial radio call to widebody transport #2 flight. This too was unsuccessful. Thereafter, the xferring controller for the widebody transport #2 flight informed me that they had also lost communication with the flight. A commercial radio call to widebody transport #2 flight was also unsuccessful. I informed my supervisor that the situation was getting critical (about 10 mins to target merge) I attempted to establish communication with ATC emergency guard frequency 121.5 with no success. I alerted the ZKC receiving controller of the situation. Next, I observed the 2 targets merge, and come out the other side. Supplemental information from acn 429530: TCASII on either aircraft would have stopped the entire chain of events. Supplemental information from acn 429610: neither aircraft was equipped with TCASII.

Original NASA ASRS Text

Title: LOSS OF RADIO COM RESULTED IN A NEAR MISS.

Narrative: I WAS WORKING ARTCC AS THE RADAR/INTERPHONE CTLR. I RECOGNIZED A POTENTIAL CONFLICTION BTWN A WDB #1 AND A WDB #2 AT FL330 ON CONVERGING COURSES. WHEN THE L1011 ENTERED MY AIRSPACE, COM HAD NOT BEEN ESTABLISHED. I THEN CALLED THE PREVIOUS SECTOR TO RE-ATTTEMPT COM XFER, WITH NO SUCCESS. I THEN ASKED MY SUPVR TO INITIATE A COMMERCIAL RADIO CALL TO WDB #2 FLT. THIS TOO WAS UNSUCCESSFUL. THEREAFTER, THE XFERRING CTLR FOR THE WDB #2 FLT INFORMED ME THAT THEY HAD ALSO LOST COM WITH THE FLT. A COMMERCIAL RADIO CALL TO WDB #2 FLT WAS ALSO UNSUCCESSFUL. I INFORMED MY SUPVR THAT THE SIT WAS GETTING CRITICAL (ABOUT 10 MINS TO TARGET MERGE) I ATTEMPTED TO ESTABLISH COM WITH ATC EMER GUARD FREQ 121.5 WITH NO SUCCESS. I ALERTED THE ZKC RECEIVING CTLR OF THE SIT. NEXT, I OBSERVED THE 2 TARGETS MERGE, AND COME OUT THE OTHER SIDE. SUPPLEMENTAL INFO FROM ACN 429530: TCASII ON EITHER ACFT WOULD HAVE STOPPED THE ENTIRE CHAIN OF EVENTS. SUPPLEMENTAL INFO FROM ACN 429610: NEITHER ACFT WAS EQUIPPED WITH TCASII.

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.