<< >> NASA ASRS Report 542634, March 2002

4 engine medium large transport flight crew stopped descent and climbed in response to observing another aircraft below and a subsequent TCASII RA to climb.

Attributes
ACN	542634
Time
Date	200203
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : pxv.vortac
State Reference	IN
Altitude	msl single value : 27000
Environment
Flight Conditions	IMC
Weather Elements	Rain
Light	Night
Aircraft 1
Controlling Facilities	artcc : zid.artcc artcc : zme.artcc
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zme.artcc artcc : zid.artcc
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 220 flight time total : 5100 flight time type : 2600
ASRS Report	542634
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	conflict : airborne less severe
Independent Detector	aircraft equipment : tcas other flight crewa other flight crewb
Resolutory Action	flight crew : took precautionary avoidance action
Consequence	faa : investigated faa : reviewed incident with flight crew Other
Miss Distance	horizontal : 36000 vertical : 600
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

While in cruise at roughly above position, we were given a descent clearance from FL270 to FL240. Conditions were IMC/night. As my first officer started the descent we noticed an aircraft at FL260 about 18 mi north of our position. The autoplt was set for a descent at 1000 FPM. I questioned ATC about the target before I took evasive action. The center controller seemed to be somewhat confused and now realizing the possibility of a midair we disconnected the autoplt and started an immediate climb. TCASII also became active and a TA became an RA. At the closest point, we estimated a distance of +600 ft and 5 mi. I did contact the center manager on the ground, there was conflicting distance differences between ZMP and ZID. Also, the controller did initiate the error and was removed pending an investigation. Without TCASII the outcome could have been different.

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Original NASA ASRS Text

Title: 4 ENG MLG FLC STOPPED DSCNT AND CLBED IN RESPONSE TO OBSERVING ANOTHER ACFT BELOW AND A SUBSEQUENT TCASII RA TO CLB.

Narrative: WHILE IN CRUISE AT ROUGHLY ABOVE POS, WE WERE GIVEN A DSCNT CLRNC FROM FL270 TO FL240. CONDITIONS WERE IMC/NIGHT. AS MY FO STARTED THE DSCNT WE NOTICED AN ACFT AT FL260 ABOUT 18 MI N OF OUR POS. THE AUTOPLT WAS SET FOR A DSCNT AT 1000 FPM. I QUESTIONED ATC ABOUT THE TARGET BEFORE I TOOK EVASIVE ACTION. THE CTR CTLR SEEMED TO BE SOMEWHAT CONFUSED AND NOW REALIZING THE POSSIBILITY OF A MIDAIR WE DISCONNECTED THE AUTOPLT AND STARTED AN IMMEDIATE CLB. TCASII ALSO BECAME ACTIVE AND A TA BECAME AN RA. AT THE CLOSEST POINT, WE ESTIMATED A DISTANCE OF +600 FT AND 5 MI. I DID CONTACT THE CTR MGR ON THE GND, THERE WAS CONFLICTING DISTANCE DIFFERENCES BTWN ZMP AND ZID. ALSO, THE CTLR DID INITIATE THE ERROR AND WAS REMOVED PENDING AN INVESTIGATION. WITHOUT TCASII THE OUTCOME COULD HAVE BEEN DIFFERENT.

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.