Aircraft on descent gets TCASII RA after deviating for WX.

Attributes
ACN	273014
Time
Date	199406
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : scy
State Reference	TX
Altitude	msl bound lower : 10700 msl bound upper : 11000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : dfw tracon : lax
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	arrival other
Flight Plan	IFR
Aircraft 2
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : atp
Experience	flight time last 90 days : 220 flight time total : 3300
ASRS Report	273014
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 1500 vertical : 1000
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Center had held us higher than usual and then asked us to slow to 280 KTS and descend to 11000 ft at seago on the scurry arrival to dfw. Our rate of descent was over 2000 FPM but to complicate things there was WX on the 296 degree radial at 18 mi, just about seago and when asked to talk to arrival approach we were unable due to frequency congestion. The captain was flying and took us off the arrival radial to avoid the 'build-ups.' just about the time I told the captain we were out of 12000 ft for 11000 ft, approach called and asked us to identify and where we were going, etc. Next I heard the TCASII TA. The captain had turned sharply. As it turned out, just to return to the radial about the same time the TCASII started to sing out so I wasn't sure if he was avoiding someone at that very second. I turned all my attention to the TCASII screen which was in WX mode 30 mi and turned it to 10 mi when I saw an aircraft slightly left, nearly under us 2600 ft and climbing fast. We started to get an RA to climb. The captain was still in a slight turn left and looking for the traffic visually. He had added power and the nose attitude had come up so I immediately rechked the TCASII on 5 mi (no WX) and started calling off range and direction. The opposing aircraft was slightly left, less than a mi, climbing, and closing and when I reported 1000 ft to target, the captain said he had him visually. I looked back up at third altimeter which we set to MSL (the other 2 are set AGL). To my surprise we were nearly at 10700 ft and sinking. The flight engineer and I shouted out about the same time the controller did that we were not level at 11000 ft. We told him we had the traffic visually and while he was leveling at 10000 ft we were on our way back to 11000 ft MSL. This all occurred between 18 mi and 24 mi and possible 1 mi north of the 296 degree radial and the 296 degree radial of scy. We did receive a 'monitor vertical speed' and probably would not have all these troubles if we did not have TCASII installed in this aircraft on this particular day.

Original NASA ASRS Text

Title: ACFT ON DSCNT GETS TCASII RA AFTER DEVIATING FOR WX.

Narrative: CTR HAD HELD US HIGHER THAN USUAL AND THEN ASKED US TO SLOW TO 280 KTS AND DSND TO 11000 FT AT SEAGO ON THE SCURRY ARR TO DFW. OUR RATE OF DSCNT WAS OVER 2000 FPM BUT TO COMPLICATE THINGS THERE WAS WX ON THE 296 DEG RADIAL AT 18 MI, JUST ABOUT SEAGO AND WHEN ASKED TO TALK TO ARR APCH WE WERE UNABLE DUE TO FREQ CONGESTION. THE CAPT WAS FLYING AND TOOK US OFF THE ARR RADIAL TO AVOID THE 'BUILD-UPS.' JUST ABOUT THE TIME I TOLD THE CAPT WE WERE OUT OF 12000 FT FOR 11000 FT, APCH CALLED AND ASKED US TO IDENT AND WHERE WE WERE GOING, ETC. NEXT I HEARD THE TCASII TA. THE CAPT HAD TURNED SHARPLY. AS IT TURNED OUT, JUST TO RETURN TO THE RADIAL ABOUT THE SAME TIME THE TCASII STARTED TO SING OUT SO I WASN'T SURE IF HE WAS AVOIDING SOMEONE AT THAT VERY SECOND. I TURNED ALL MY ATTN TO THE TCASII SCREEN WHICH WAS IN WX MODE 30 MI AND TURNED IT TO 10 MI WHEN I SAW AN ACFT SLIGHTLY L, NEARLY UNDER US 2600 FT AND CLBING FAST. WE STARTED TO GET AN RA TO CLB. THE CAPT WAS STILL IN A SLIGHT TURN L AND LOOKING FOR THE TFC VISUALLY. HE HAD ADDED PWR AND THE NOSE ATTITUDE HAD COME UP SO I IMMEDIATELY RECHKED THE TCASII ON 5 MI (NO WX) AND STARTED CALLING OFF RANGE AND DIRECTION. THE OPPOSING ACFT WAS SLIGHTLY L, LESS THAN A MI, CLBING, AND CLOSING AND WHEN I RPTED 1000 FT TO TARGET, THE CAPT SAID HE HAD HIM VISUALLY. I LOOKED BACK UP AT THIRD ALTIMETER WHICH WE SET TO MSL (THE OTHER 2 ARE SET AGL). TO MY SURPRISE WE WERE NEARLY AT 10700 FT AND SINKING. THE FE AND I SHOUTED OUT ABOUT THE SAME TIME THE CTLR DID THAT WE WERE NOT LEVEL AT 11000 FT. WE TOLD HIM WE HAD THE TFC VISUALLY AND WHILE HE WAS LEVELING AT 10000 FT WE WERE ON OUR WAY BACK TO 11000 FT MSL. THIS ALL OCCURRED BTWN 18 MI AND 24 MI AND POSSIBLE 1 MI N OF THE 296 DEG RADIAL AND THE 296 DEG RADIAL OF SCY. WE DID RECEIVE A 'MONITOR VERT SPD' AND PROBABLY WOULD NOT HAVE ALL THESE TROUBLES IF WE DID NOT HAVE TCASII INSTALLED IN THIS ACFT ON THIS PARTICULAR DAY.

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.