Air carrier X TCASII RA unauthorized descent to occupied altitude had less than standard separation from air carrier Y. Air carrier Z possible altitude deviation caused air carrier X TCASII RA. Pilot deviation.

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Attributes
ACN	226493
Time
Date	199209
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : ord
State Reference	IL
Altitude	msl bound lower : 23000 msl bound upper : 23000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau artcc : zau
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 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, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
ASRS Report	226493
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance non adherence : required legal separation
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action
Consequence	faa : investigated
Miss Distance	horizontal : 12000 vertical : 0
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Frequency was extremely busy. Air carrier X (ord inbound) heading 230 degrees south level FL240. Air carrier Y (ord departure) wbound level FL230. Air carrier Z (ord inbound) eastbound descending FL250. Air carrier Z coming towards air carrier X still descending just leveling off at FL250 (air carrier Z might have went to FL248, data block never showed any altitude lower than FL250). With air carrier Z just off of air carrier X's right side, air carrier X received a TCASII instruction to descend. Pilot advised ZAU of his situation. At the same time, air carrier Y was right under air carrier X at FL230. Air carrier Y said the air carrier X was between 1 to 2 mi at the same altitude. After occurrence ZAU climbed air carrier X back to FL240.

Original NASA ASRS Text

Title: ACR X TCASII RA UNAUTH DSCNT TO OCCUPIED ALT HAD LTSS FROM ACR Y. ACR Z POSSIBLE ALTDEV CAUSED ACR X TCASII RA. PLTDEV.

Narrative: FREQ WAS EXTREMELY BUSY. ACR X (ORD INBOUND) HDG 230 DEGS S LEVEL FL240. ACR Y (ORD DEP) WBOUND LEVEL FL230. ACR Z (ORD INBOUND) EBOUND DSNDING FL250. ACR Z COMING TOWARDS ACR X STILL DSNDING JUST LEVELING OFF AT FL250 (ACR Z MIGHT HAVE WENT TO FL248, DATA BLOCK NEVER SHOWED ANY ALT LOWER THAN FL250). WITH ACR Z JUST OFF OF ACR X'S R SIDE, ACR X RECEIVED A TCASII INSTRUCTION TO DSND. PLT ADVISED ZAU OF HIS SIT. AT THE SAME TIME, ACR Y WAS RIGHT UNDER ACR X AT FL230. ACR Y SAID THE ACR X WAS BTWN 1 TO 2 MI AT THE SAME ALT. AFTER OCCURRENCE ZAU CLBED ACR X BACK TO FL240.

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.