Air carrier Y TCASII RA unauthorized descent non adherence to ATC clearance had less than standard separation from air carrier X evasive action taken.

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Attributes
ACN	247276
Time
Date	199304
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ord
State Reference	IL
Altitude	msl bound lower : 6000 msl bound upper : 7000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ord
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : departure
Qualification	controller : radar
Experience	controller radar : 7
ASRS Report	247276
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller radar : 20
ASRS Report	247277
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : required legal separation non adherence : clearance
Independent Detector	atc equipment other atc equipment : unspecified aircraft equipment other aircraft equipment : unspecified
Resolutory Action	controller : issued new clearance flight crew : took evasive action other
Consequence	faa : investigated
Miss Distance	horizontal : 1500 vertical : 300
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

The controller was working air carrier X, an eastbound departure. The controller turned air carrier X to a 090 degree heading and climbed air carrier X to 6000 ft. The controller then pointed out arrival traffic air carrier Y to air carrier X as 1 O'clock, 4 mi, 7000 ft. Air carrier X reported the traffic in sight. The arrival controller then yelled out that air carrier Y was responding to an RA on his TCASII. The controller then noticed the conflict alert going off with air carrier Y at 6500 ft, immediately followed by 6100 ft. The controller advised air carrier X to maintain visual separation. Air carrier X told the controller he still had air carrier Y in sight and was descending a few hundred ft. The targets then passed. The TCASII aircraft deviation was 1100 ft. Supplemental information from acn 247277: air carrier Y advised he was descending in response to an RA. I told him there was no traffic above him, everything was below him. When I observed his altitude was 6500 ft, I told him to level off, but he continued descending. There was traffic below him at 6000 ft.

Original NASA ASRS Text

Title: ACR Y TCASII RA UNAUTH DSCNT NON ADHERENCE TO ATC CLRNC HAD LTSS FROM ACR X EVASIVE ACTION TAKEN.

Narrative: THE CTLR WAS WORKING ACR X, AN EBOUND DEP. THE CTLR TURNED ACR X TO A 090 DEG HDG AND CLBED ACR X TO 6000 FT. THE CTLR THEN POINTED OUT ARR TFC ACR Y TO ACR X AS 1 O'CLOCK, 4 MI, 7000 FT. ACR X RPTED THE TFC IN SIGHT. THE ARR CTLR THEN YELLED OUT THAT ACR Y WAS RESPONDING TO AN RA ON HIS TCASII. THE CTLR THEN NOTICED THE CONFLICT ALERT GOING OFF WITH ACR Y AT 6500 FT, IMMEDIATELY FOLLOWED BY 6100 FT. THE CTLR ADVISED ACR X TO MAINTAIN VISUAL SEPARATION. ACR X TOLD THE CTLR HE STILL HAD ACR Y IN SIGHT AND WAS DSNDING A FEW HUNDRED FT. THE TARGETS THEN PASSED. THE TCASII ACFT DEV WAS 1100 FT. SUPPLEMENTAL INFO FROM ACN 247277: ACR Y ADVISED HE WAS DSNDING IN RESPONSE TO AN RA. I TOLD HIM THERE WAS NO TFC ABOVE HIM, EVERYTHING WAS BELOW HIM. WHEN I OBSERVED HIS ALT WAS 6500 FT, I TOLD HIM TO LEVEL OFF, BUT HE CONTINUED DSNDING. THERE WAS TFC BELOW HIM AT 6000 FT.

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.