Air carrier X TCASII TA RA with large transport twin aircraft. See and avoid concept. Evasive action...

Attributes
ACN	302270
Time
Date	199504
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : sbv
State Reference	VA
Altitude	msl bound lower : 10000 msl bound upper : 9300
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : sna
Operator	common carrier : air carrier
Make Model Name	Fokker 100
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	arrival star : star enroute airway : zdc
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	other : unknown
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	VFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 230 flight time total : 7800 flight time type : 650
ASRS Report	302270
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 25 flight time total : 7000 flight time type : 25
ASRS Report	302277
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 0 vertical : 800
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

ZDC descended us, air carrier X, from 17000 ft to 10000 ft. As we were descending through 11000 ft, center warned us about VFR traffic at 10500 ft (unverified) at our 10 O'clock and 3 mi. At about the same time, TCASII called 'traffic.' I looked out and saw a light twin converging with us. TCASII then issued an RA (descend, descend) which my copilot who was flying immediately obeyed. This caused us to descend to about 9300 ft. When called 'clear of conflict' by TCASII, we returned to 10000 ft. Center was advised of the RA. We passed very close to and beneath the twin. Supplemental information from acn 302277: ZDC didn't advise us of converging traffic from left to right. Our TCASII didn't show traffic until we were within a few mi of a light twin. We were descending and he was possibly level. TCASII gave us a command to descend below our assigned altitude 10000 ft and as soon as this command was given by TCASII, ZDC gave us a TA. We responded to ZDC that we had an RA on our TCASII. Nothing further was said.

Original NASA ASRS Text

Title: ACR X TCASII TA RA WITH LGT TWIN ACFT. SEE AND AVOID CONCEPT. EVASIVE ACTION DSCNT.

Narrative: ZDC DSNDED US, ACR X, FROM 17000 FT TO 10000 FT. AS WE WERE DSNDING THROUGH 11000 FT, CTR WARNED US ABOUT VFR TFC AT 10500 FT (UNVERIFIED) AT OUR 10 O'CLOCK AND 3 MI. AT ABOUT THE SAME TIME, TCASII CALLED 'TFC.' I LOOKED OUT AND SAW A LIGHT TWIN CONVERGING WITH US. TCASII THEN ISSUED AN RA (DSND, DSND) WHICH MY COPLT WHO WAS FLYING IMMEDIATELY OBEYED. THIS CAUSED US TO DSND TO ABOUT 9300 FT. WHEN CALLED 'CLR OF CONFLICT' BY TCASII, WE RETURNED TO 10000 FT. CTR WAS ADVISED OF THE RA. WE PASSED VERY CLOSE TO AND BENEATH THE TWIN. SUPPLEMENTAL INFO FROM ACN 302277: ZDC DIDN'T ADVISE US OF CONVERGING TFC FROM L TO R. OUR TCASII DIDN'T SHOW TFC UNTIL WE WERE WITHIN A FEW MI OF A LIGHT TWIN. WE WERE DSNDING AND HE WAS POSSIBLY LEVEL. TCASII GAVE US A COMMAND TO DSND BELOW OUR ASSIGNED ALT 10000 FT AND AS SOON AS THIS COMMAND WAS GIVEN BY TCASII, ZDC GAVE US A TA. WE RESPONDED TO ZDC THAT WE HAD AN RA ON OUR TCASII. NOTHING FURTHER WAS SAID.

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.

Air carrier X TCASII TA RA with large transport twin aircraft. See and avoid concept. Evasive action descent.