An air carrier MD80 flight crew reports an encounter with a twin engined aircraft at 10000 ft while ...

Attributes
ACN	372078
Time
Date	199706
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : las
State Reference	NV
Altitude	msl bound lower : 10000 msl bound upper : 10000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : las
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	cruise other
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	372078
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
ASRS Report	372073
Events
Anomaly	conflict : airborne less severe other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew Other
Miss Distance	horizontal : 1500 vertical : 100
Supplementary
Air Traffic Incident	other

Narrative:

Level at 10000 ft, 25-30 mi east of las in contact with approach control. Target appeared on TCASII at approximately 10 O'clock position, level at our altitude close in on 20 mi range, I selected 10 mi then immediately 5 mi range to fix his position while asking first officer to ask approach about traffic. At same time target was rapidly closing going to TA and then immediately to an RA. This happened within a span of possibly 4 seconds. We responded to the RA command to climb after which approach gave us a conflict alert and told us to descend. We informed him we were climbing in response to an RA and began a turn to the right as target appeared to be climbing into us. After a few seconds the target stopped his climb and began a descent. We ended our maneuver. Traffic appeared at approximately 2 mi, possibly less, was not talking with approach or center and was level at 10000 ft. Approach picked up traffic about the time we began to climb. We never saw the traffic, however, several passenger on deplaning reported seeing a twin engine aircraft approximately 1000 ft from us. Due to the maneuver I'm not sure about the accuracy of their estimate. Based on TCASII I would guess traffic was within 1/4 mi +/-100 ft at closest approach. Talking with approach control supervisor, we were told the aircraft continued northbound and was not talking with anyone.

Original NASA ASRS Text

Title: AN ACR MD80 FLC RPTS AN ENCOUNTER WITH A TWIN ENGINED ACFT AT 10000 FT WHILE TALKING TO APCH CTL. THE OTHER ACFT WAS NOT ON THE COM FREQ OR, APPARENTLY, REQUIRED TO BE.

Narrative: LEVEL AT 10000 FT, 25-30 MI E OF LAS IN CONTACT WITH APCH CTL. TARGET APPEARED ON TCASII AT APPROX 10 O'CLOCK POS, LEVEL AT OUR ALT CLOSE IN ON 20 MI RANGE, I SELECTED 10 MI THEN IMMEDIATELY 5 MI RANGE TO FIX HIS POS WHILE ASKING FO TO ASK APCH ABOUT TFC. AT SAME TIME TARGET WAS RAPIDLY CLOSING GOING TO TA AND THEN IMMEDIATELY TO AN RA. THIS HAPPENED WITHIN A SPAN OF POSSIBLY 4 SECONDS. WE RESPONDED TO THE RA COMMAND TO CLB AFTER WHICH APCH GAVE US A CONFLICT ALERT AND TOLD US TO DSND. WE INFORMED HIM WE WERE CLBING IN RESPONSE TO AN RA AND BEGAN A TURN TO THE R AS TARGET APPEARED TO BE CLBING INTO US. AFTER A FEW SECONDS THE TARGET STOPPED HIS CLB AND BEGAN A DSCNT. WE ENDED OUR MANEUVER. TFC APPEARED AT APPROX 2 MI, POSSIBLY LESS, WAS NOT TALKING WITH APCH OR CTR AND WAS LEVEL AT 10000 FT. APCH PICKED UP TFC ABOUT THE TIME WE BEGAN TO CLB. WE NEVER SAW THE TFC, HOWEVER, SEVERAL PAX ON DEPLANING RPTED SEEING A TWIN ENG ACFT APPROX 1000 FT FROM US. DUE TO THE MANEUVER I'M NOT SURE ABOUT THE ACCURACY OF THEIR ESTIMATE. BASED ON TCASII I WOULD GUESS TFC WAS WITHIN 1/4 MI +/-100 FT AT CLOSEST APCH. TALKING WITH APCH CTL SUPVR, WE WERE TOLD THE ACFT CONTINUED NBOUND AND WAS NOT TALKING WITH ANYONE.

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.

An air carrier MD80 flight crew reports an encounter with a twin engined aircraft at 10000 ft while talking to approach control. The other aircraft was not on the communication frequency or, apparently, required to be.