<< >> NASA ASRS Report 404323, June 1998

DC9 crew received a TCASII TA and then an RA. Controller had given descent clearance that crossed another aircraft's altitude.

Attributes
ACN	404323
Time
Date	199806
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : fwa
State Reference	IN
Altitude	msl bound lower : 24000 msl bound upper : 29000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau
Operator	common carrier : air carrier
Make Model Name	DC-9 30
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	arrival other arrival star : star
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B747 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : commercial pilot : cfi pilot : atp pilot : instrument
Experience	flight time last 90 days : 200 flight time total : 15000 flight time type : 2800
ASRS Report	404323
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	conflict : airborne less severe non adherence : published procedure
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 : 21000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I had been receiving step dscnts on the mizar 3 arrival en route to dtw. At approximately 31 mi from ft wayne, descending through FL290 to FL240 ATC asked if we could do our best to cross 20 mi from fwa at FL240. We agreed to do our best but indicated to ATC the restr was going to be tight. We increased our descent rate to 3600 FPM. Descending through FL258 ATC asked us to hurry through FL250. At the same time ATC made this request we got a TCASII TA, followed shortly by a TCASII RA to increase descent. We complied with the TCASII RA and also established visual contact with the aircraft. ATC asked if we were out of FL250 and we replied affirmative and we also indicated we had visual contact. ATC sounded a bit shaken. I'm not sure where ATC lost separation but we were in full compliance with ATC instructions. The TCASII worked great and proved to be a valuable instrument.

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Original NASA ASRS Text

Title: DC9 CREW RECEIVED A TCASII TA AND THEN AN RA. CTLR HAD GIVEN DSCNT CLRNC THAT CROSSED ANOTHER ACFT'S ALT.

Narrative: I HAD BEEN RECEIVING STEP DSCNTS ON THE MIZAR 3 ARR ENRTE TO DTW. AT APPROX 31 MI FROM FT WAYNE, DSNDING THROUGH FL290 TO FL240 ATC ASKED IF WE COULD DO OUR BEST TO CROSS 20 MI FROM FWA AT FL240. WE AGREED TO DO OUR BEST BUT INDICATED TO ATC THE RESTR WAS GOING TO BE TIGHT. WE INCREASED OUR DSCNT RATE TO 3600 FPM. DSNDING THROUGH FL258 ATC ASKED US TO HURRY THROUGH FL250. AT THE SAME TIME ATC MADE THIS REQUEST WE GOT A TCASII TA, FOLLOWED SHORTLY BY A TCASII RA TO INCREASE DSCNT. WE COMPLIED WITH THE TCASII RA AND ALSO ESTABLISHED VISUAL CONTACT WITH THE ACFT. ATC ASKED IF WE WERE OUT OF FL250 AND WE REPLIED AFFIRMATIVE AND WE ALSO INDICATED WE HAD VISUAL CONTACT. ATC SOUNDED A BIT SHAKEN. I'M NOT SURE WHERE ATC LOST SEPARATION BUT WE WERE IN FULL COMPLIANCE WITH ATC INSTRUCTIONS. THE TCASII WORKED GREAT AND PROVED TO BE A VALUABLE INST.

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.