TCASII. RA to climb. ATC didn't have intruder on radar.

Attributes
ACN	318217
Time
Date	199510
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : pdx
State Reference	OR
Altitude	msl bound lower : 5400 msl bound upper : 5400
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : pdx
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Flight Phase	descent other
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Flight Plan	None
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	318217
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
ASRS Report	318761
Events
Anomaly	conflict : airborne less severe other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 2000 vertical : 200
Supplementary
Air Traffic Incident	other

Narrative:

We were on the bonvl 3 arrival 079 degree radial 20 DME to pdx. In the descent through 5400 ft, we received a TCASII RA. There was no TCASII TA given first. Intruder was 400 ft below and at 1.5 mi at first indication of RA. The RA called for a climb. We followed the RA and saw the aircraft off to our right about 2-3 seconds after the first indication on the TCASII. The event was over in about 10 seconds. The intruder was a single engine cessna level at 5000 ft. Both aircraft at closest point came within about 200 ft vertically and about 2000 ft horizontally. Aircraft were on a converging course at the time of the event. No evasive action was taken other than a reversal of our descent and about a 200 ft climb to follow the RA. TCASII never showed a TA. It just went directly to a RA. I asked the controller if he saw the cessna on his radar and he said he did not.

Original NASA ASRS Text

Title: TCASII. RA TO CLB. ATC DIDN'T HAVE INTRUDER ON RADAR.

Narrative: WE WERE ON THE BONVL 3 ARR 079 DEG RADIAL 20 DME TO PDX. IN THE DSCNT THROUGH 5400 FT, WE RECEIVED A TCASII RA. THERE WAS NO TCASII TA GIVEN FIRST. INTRUDER WAS 400 FT BELOW AND AT 1.5 MI AT FIRST INDICATION OF RA. THE RA CALLED FOR A CLB. WE FOLLOWED THE RA AND SAW THE ACFT OFF TO OUR R ABOUT 2-3 SECONDS AFTER THE FIRST INDICATION ON THE TCASII. THE EVENT WAS OVER IN ABOUT 10 SECONDS. THE INTRUDER WAS A SINGLE ENG CESSNA LEVEL AT 5000 FT. BOTH ACFT AT CLOSEST POINT CAME WITHIN ABOUT 200 FT VERTLY AND ABOUT 2000 FT HORIZLY. ACFT WERE ON A CONVERGING COURSE AT THE TIME OF THE EVENT. NO EVASIVE ACTION WAS TAKEN OTHER THAN A REVERSAL OF OUR DSCNT AND ABOUT A 200 FT CLB TO FOLLOW THE RA. TCASII NEVER SHOWED A TA. IT JUST WENT DIRECTLY TO A RA. I ASKED THE CTLR IF HE SAW THE CESSNA ON HIS RADAR AND HE SAID HE DID NOT.

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.