An air carrier large transport crew climbed in response to a TCASII command.

Attributes
ACN	253076
Time
Date	199309
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : ogd
State Reference	UT
Altitude	msl bound lower : 17700 msl bound upper : 18000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zlc
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	enroute airway : zlc
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Flight Plan	VFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi pilot : instrument pilot : commercial pilot : flight engineer
Experience	flight time last 90 days : 160 flight time total : 11000 flight time type : 400
ASRS Report	253076
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : took evasive action other
Consequence	Other
Miss Distance	horizontal : 3000 vertical : 200
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Center cleared us to 17000 ft. Descending out of 17700, ATC called VFR traffic at 11 O'clock at 17500 ft, crossing left to right. TCASII advised a climb of about 2000 FPM. I acquired the traffic, but due to the darkness, could not determine direction or closure rate. The captain stowed the speed brakes, disconnected the autoplt, added power and climbed to FL180. Traffic passed below us about 1/2 mi off our left wing.

Original NASA ASRS Text

Title: AN ACR LGT CREW CLBED IN RESPONSE TO A TCASII COMMAND.

Narrative: CTR CLRED US TO 17000 FT. DSNDING OUT OF 17700, ATC CALLED VFR TFC AT 11 O'CLOCK AT 17500 FT, XING L TO R. TCASII ADVISED A CLB OF ABOUT 2000 FPM. I ACQUIRED THE TFC, BUT DUE TO THE DARKNESS, COULD NOT DETERMINE DIRECTION OR CLOSURE RATE. THE CAPT STOWED THE SPD BRAKES, DISCONNECTED THE AUTOPLT, ADDED PWR AND CLBED TO FL180. TFC PASSED BELOW US ABOUT 1/2 MI OFF OUR L WING.

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.