Excursion from assigned altitude. Tcassii induced.

Attributes
ACN	202573
Time
Date	199202
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : stv
State Reference	TX
Altitude	msl bound lower : 37000 msl bound upper : 37700
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zfw
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other
Route In Use	enroute : direct enroute : on vectors enroute airway : zfw
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 11000 flight time type : 5000
ASRS Report	202573
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe inflight encounter : weather non adherence : required legal separation other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	controller : issued new clearance flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 3000 vertical : 700
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Pilot Deviation Operational Error

Narrative:

Proceeding direct to stonewall VOR heading 120 degrees at FL370. East/west line of thunderstorms very active in cloud lightning tops to FL400. We requested and were given east deviation to avoid a build-up at our 12-1 O'clock position. Another cell at 9-10 O'clock was also a factor. When steady on our deviation heading, center called traffic at our altitude and 2 O'clock position. And gave us an immediate left turn of 45 degrees. We were aware of this aircraft on TCASII and could see him visually at all times. He was deviating around the same cell and we had been watching him. He was coming from the west and evidently began deviating more easterly than center anticipated causing a conflict. While making the 45 degree left turn, center asked for more turn to T he left. TCASII called 'traffic' and then a descend command followed almost immediately by a 'climb climb' command. As the left turn increased. Since we were visual and watching the other aircraft and aware of our co- altitude we had begun to climb in the turn as the initial climb command came out to insure separation. We climbed to FL377 and advised center of TCASII deviation. The eastbound aircraft remained in sight until passing below and behind. We reported the deviation and returned to FL370.

Original NASA ASRS Text

Title: EXCURSION FROM ASSIGNED ALT. TCASSII INDUCED.

Narrative: PROCEEDING DIRECT TO STONEWALL VOR HDG 120 DEGS AT FL370. E/W LINE OF TSTMS VERY ACTIVE IN CLOUD LIGHTNING TOPS TO FL400. WE REQUESTED AND WERE GIVEN E DEV TO AVOID A BUILD-UP AT OUR 12-1 O'CLOCK POS. ANOTHER CELL AT 9-10 O'CLOCK WAS ALSO A FACTOR. WHEN STEADY ON OUR DEV HDG, CTR CALLED TFC AT OUR ALT AND 2 O'CLOCK POS. AND GAVE US AN IMMEDIATE L TURN OF 45 DEGS. WE WERE AWARE OF THIS ACFT ON TCASII AND COULD SEE HIM VISUALLY AT ALL TIMES. HE WAS DEVIATING AROUND THE SAME CELL AND WE HAD BEEN WATCHING HIM. HE WAS COMING FROM THE W AND EVIDENTLY BEGAN DEVIATING MORE EASTERLY THAN CTR ANTICIPATED CAUSING A CONFLICT. WHILE MAKING THE 45 DEG L TURN, CTR ASKED FOR MORE TURN TO T HE L. TCASII CALLED 'TFC' AND THEN A DSND COMMAND FOLLOWED ALMOST IMMEDIATELY BY A 'CLB CLB' COMMAND. AS THE L TURN INCREASED. SINCE WE WERE VISUAL AND WATCHING THE OTHER ACFT AND AWARE OF OUR CO- ALT WE HAD BEGUN TO CLB IN THE TURN AS THE INITIAL CLB COMMAND CAME OUT TO INSURE SEPARATION. WE CLBED TO FL377 AND ADVISED CTR OF TCASII DEV. THE EBOUND ACFT REMAINED IN SIGHT UNTIL PASSING BELOW AND BEHIND. WE RPTED THE DEV AND RETURNED TO FL370.

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.