Operational error. Less than standard separation between two air carrier medium large transport.

Attributes
ACN	102400
Time
Date	198901
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : den
State Reference	CO
Altitude	msl bound lower : 10800 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : den
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
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 : 13500 flight time type : 2500
ASRS Report	102400
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	conflict : airborne less severe non adherence : far other anomaly other
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : took evasive action other
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 9000 vertical : 200
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Level at 10000' received climb clearance to FL200. First officer hand flying aircraft initiated climb at 10800'. ATC advised 'maintain 10000 and turn left 245 degree'. That was unusual. I glanced up, saw at 2 O'clock and almost level an medium large transport Y moving towards us at right angles. I took aircraft, chopped power and descended back to 10000. ATC acknowledged they had inadvertently assigned us a climb clearance. Sun position was at 12 O'clock, just inside upper part of windscreen and we had just completed approximately a 180 degree turn from 080 degree (departure runway heading) to 270 degree. I think the ATC conflict alert system alerted the controller as we initiated the climb.

Original NASA ASRS Text

Title: OPERATIONAL ERROR. LESS THAN STANDARD SEPARATION BETWEEN TWO ACR MLG.

Narrative: LEVEL AT 10000' RECEIVED CLIMB CLRNC TO FL200. F/O HAND FLYING ACFT INITIATED CLIMB AT 10800'. ATC ADVISED 'MAINTAIN 10000 AND TURN LEFT 245 DEG'. THAT WAS UNUSUAL. I GLANCED UP, SAW AT 2 O'CLOCK AND ALMOST LEVEL AN MLG Y MOVING TOWARDS US AT RIGHT ANGLES. I TOOK ACFT, CHOPPED POWER AND DESCENDED BACK TO 10000. ATC ACKNOWLEDGED THEY HAD INADVERTENTLY ASSIGNED US A CLIMB CLRNC. SUN POSITION WAS AT 12 O'CLOCK, JUST INSIDE UPPER PART OF WINDSCREEN AND WE HAD JUST COMPLETED APPROX A 180 DEG TURN FROM 080 DEG (DEP RWY HDG) TO 270 DEG. I THINK THE ATC CONFLICT ALERT SYSTEM ALERTED THE CTLR AS WE INITIATED THE CLIMB.

Data retrieved from NASA's ASRS site as of August 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.