An air carrier large transport climbed in response to a TCASII command. Both aircraft were in IMC.

Attributes
ACN	251781
Time
Date	199309
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : gso
State Reference	NC
Altitude	msl bound lower : 26000 msl bound upper : 27000
Environment
Flight Conditions	IMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : ztl
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	climbout : intermediate altitude cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 150 flight time total : 13000 flight time type : 7000
ASRS Report	251781
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance non adherence : required legal separation other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	vertical : 700
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were given TA by ATC of opposite direction small transport at FL250, 8 mi. We received TCASII TA confirmation of traffic 1200 ft below our altitude (no visual due IMC). At approximately 6 mi separation, we received TCASII RA with compulsory 500 FPM climb to avoid traffic now annunciated at 800 ft below our altitude and climbing. We had no visual contact and initiated immediate climb to comply and simultaneously advised ATC of our action. At FL270 we received TCASII TA that traffic was diverging behind our position now 1600 ft below our altitude. This indicated that traffic had climbed to within 600 ft of our assigned altitude. With ATC clearance, we descended back to FL260. Trip continued with no further incident.

Original NASA ASRS Text

Title: AN ACR LGT CLBED IN RESPONSE TO A TCASII COMMAND. BOTH ACFT WERE IN IMC.

Narrative: WE WERE GIVEN TA BY ATC OF OPPOSITE DIRECTION SMT AT FL250, 8 MI. WE RECEIVED TCASII TA CONFIRMATION OF TFC 1200 FT BELOW OUR ALT (NO VISUAL DUE IMC). AT APPROX 6 MI SEPARATION, WE RECEIVED TCASII RA WITH COMPULSORY 500 FPM CLB TO AVOID TFC NOW ANNUNCIATED AT 800 FT BELOW OUR ALT AND CLBING. WE HAD NO VISUAL CONTACT AND INITIATED IMMEDIATE CLB TO COMPLY AND SIMULTANEOUSLY ADVISED ATC OF OUR ACTION. AT FL270 WE RECEIVED TCASII TA THAT TFC WAS DIVERGING BEHIND OUR POS NOW 1600 FT BELOW OUR ALT. THIS INDICATED THAT TFC HAD CLBED TO WITHIN 600 FT OF OUR ASSIGNED ALT. WITH ATC CLRNC, WE DSNDED BACK TO FL260. TRIP CONTINUED WITH NO FURTHER INCIDENT.

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.