A descending B727 stops its descent at FL340 to avoid crossing traffic at FL330. ATC had requested the B727 to perform an expedited descent to FL310 and had issued a new heading to fly. The amended clrncs as issued by ATC contradicted the TCASII commands.

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Attributes
ACN	428070
Time
Date	199902
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : loz.vortac
State Reference	KY
Altitude	msl bound lower : 31000 msl bound upper : 34000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid.artcc
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	cruise : level cruise : enroute altitude change descent : intermediate altitude
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zid.artcc
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 200 flight time total : 4500 flight time type : 350
ASRS Report	428070
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : undershoot conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : radar aircraft equipment : tcas
Resolutory Action	controller : issued new clearance flight crew : took evasive action
Miss Distance	horizontal : 18000 vertical : 1000
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

We were at FL350 on an assigned heading of 005 degrees for traffic. We were then cleared to descend to FL310 for traffic. Approaching FL340 our TCASII announced 'traffic, reduce descent' about 2 O'clock and at FL330. ZID then gave us a heading of 330 degrees and told us to expedite descent to FL310. We turned to 330 degrees but stopped the descent at FL340 for traffic below at FL330. After the TCASII announced 'clear of conflict,' we continued our descent to FL310 and ATC turned us further left to a heading of 310 degrees. We continued our flight without further incident. I continued my flight engineer duties. The controller's request to expedite descent was a poor one due to the lack of separation between our aircraft and the aircraft below at FL330.

Original NASA ASRS Text

Title: A DSNDING B727 STOPS ITS DSCNT AT FL340 TO AVOID XING TFC AT FL330. ATC HAD REQUESTED THE B727 TO PERFORM AN EXPEDITED DSCNT TO FL310 AND HAD ISSUED A NEW HDG TO FLY. THE AMENDED CLRNCS AS ISSUED BY ATC CONTRADICTED THE TCASII COMMANDS.

Narrative: WE WERE AT FL350 ON AN ASSIGNED HDG OF 005 DEGS FOR TFC. WE WERE THEN CLRED TO DSND TO FL310 FOR TFC. APCHING FL340 OUR TCASII ANNOUNCED 'TFC, REDUCE DSCNT' ABOUT 2 O'CLOCK AND AT FL330. ZID THEN GAVE US A HDG OF 330 DEGS AND TOLD US TO EXPEDITE DSCNT TO FL310. WE TURNED TO 330 DEGS BUT STOPPED THE DSCNT AT FL340 FOR TFC BELOW AT FL330. AFTER THE TCASII ANNOUNCED 'CLR OF CONFLICT,' WE CONTINUED OUR DSCNT TO FL310 AND ATC TURNED US FURTHER L TO A HDG OF 310 DEGS. WE CONTINUED OUR FLT WITHOUT FURTHER INCIDENT. I CONTINUED MY FE DUTIES. THE CTLR'S REQUEST TO EXPEDITE DSCNT WAS A POOR ONE DUE TO THE LACK OF SEPARATION BTWN OUR ACFT AND THE ACFT BELOW AT FL330.

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.