An F900 and a B777 had coordinated TCASII RA's in C90 class B airspace.

Attributes
ACN	500609
Time
Date	200102
Day	Wed
Local Time Of Day	0001 To 0600
Place
Locale Reference	airport : mdw.airport
State Reference	IL
Altitude	msl bound lower : 3000 msl bound upper : 4100
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : c90.tracon
Operator	general aviation : corporate
Make Model Name	Falcon 900
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	climbout : vacating altitude climbout : initial
Route In Use	departure : on vectors departure sid : ns
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : c90.tracon
Operator	common carrier : air carrier
Make Model Name	B777 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other other
Flight Phase	descent : approach
Route In Use	arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Experience	controller radar : 19 controller time certified in position1 : 11
ASRS Report	500609
Person 2
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 60 flight time total : 10000 flight time type : 1000
ASRS Report	500825
Events
Anomaly	conflict : airborne critical non adherence : required legal separation
Independent Detector	aircraft equipment : tcas other controllera other flight crewa other flight crewb
Resolutory Action	flight crew : took precautionary avoidance action
Miss Distance	horizontal : 3000 vertical : 500
Supplementary
Problem Areas	Flight Crew Human Performance Airspace Structure ATC Human Performance
Primary Problem	Ambiguous

Narrative:

Falcon 900 departing mdw restr to 3000 ft by mdw tower. B777 arriving into ord, on base leg at 4000 ft for ILS runway 22L approach. Falcon 900, while still on mdw tower frequency, said he was receiving TCASII alert, told to climb above 3000 ft by RA. Climbed up to 4100 ft, then descended back down to 3000 ft. It was at this point I first talked to FA900. Verified altitude. Asked him a few questions, claimed he got a TCASII alert very shortly after takeoff. B777 pilot apparently saw FA900 pop up through low level cloud/fog layer. I believe he also got RA from TCASII but from FA900's climb. FA900 busted through 3000 ft to avert collision with who? That is the million dollar question. All I can think of is that the FA900 got a TCASII alert from a previous ord arrival. Even though that previous ord arrival would be well off his right, no other traffic would have been in the area due to WX. Callback conversation with reporter revealed the following information: reporter had a chance to review the 'raptor' ATC radar tape. He states that there was no third aircraft present. He also states that raptor does not show all radar traffic present. The original falcon TCASII RA occurred in mdw airspace so this controller was not involved until the falcon was handed off to him. Supplemental information from acn 500825: on departure from mdw got a TA traffic. Advised tower and was told no traffic in the area. Continued climb for 3000 ft assigned. TA went to RA with climb command. Advised tower and departure control we were starting a TCASII climb. Climbed above assigned altitude. When clear of conflict, returned to 3000 ft.

Original NASA ASRS Text

Title: AN F900 AND A B777 HAD COORDINATED TCASII RA'S IN C90 CLASS B AIRSPACE.

Narrative: FALCON 900 DEPARTING MDW RESTR TO 3000 FT BY MDW TWR. B777 ARRIVING INTO ORD, ON BASE LEG AT 4000 FT FOR ILS RWY 22L APCH. FALCON 900, WHILE STILL ON MDW TWR FREQ, SAID HE WAS RECEIVING TCASII ALERT, TOLD TO CLB ABOVE 3000 FT BY RA. CLBED UP TO 4100 FT, THEN DSNDED BACK DOWN TO 3000 FT. IT WAS AT THIS POINT I FIRST TALKED TO FA900. VERIFIED ALT. ASKED HIM A FEW QUESTIONS, CLAIMED HE GOT A TCASII ALERT VERY SHORTLY AFTER TKOF. B777 PLT APPARENTLY SAW FA900 POP UP THROUGH LOW LEVEL CLOUD/FOG LAYER. I BELIEVE HE ALSO GOT RA FROM TCASII BUT FROM FA900'S CLB. FA900 BUSTED THROUGH 3000 FT TO AVERT COLLISION WITH WHO? THAT IS THE MILLION DOLLAR QUESTION. ALL I CAN THINK OF IS THAT THE FA900 GOT A TCASII ALERT FROM A PREVIOUS ORD ARR. EVEN THOUGH THAT PREVIOUS ORD ARR WOULD BE WELL OFF HIS R, NO OTHER TFC WOULD HAVE BEEN IN THE AREA DUE TO WX. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR HAD A CHANCE TO REVIEW THE 'RAPTOR' ATC RADAR TAPE. HE STATES THAT THERE WAS NO THIRD ACFT PRESENT. HE ALSO STATES THAT RAPTOR DOES NOT SHOW ALL RADAR TFC PRESENT. THE ORIGINAL FALCON TCASII RA OCCURRED IN MDW AIRSPACE SO THIS CTLR WAS NOT INVOLVED UNTIL THE FALCON WAS HANDED OFF TO HIM. SUPPLEMENTAL INFO FROM ACN 500825: ON DEP FROM MDW GOT A TA TFC. ADVISED TWR AND WAS TOLD NO TFC IN THE AREA. CONTINUED CLB FOR 3000 FT ASSIGNED. TA WENT TO RA WITH CLB COMMAND. ADVISED TWR AND DEP CTL WE WERE STARTING A TCASII CLB. CLBED ABOVE ASSIGNED ALT. WHEN CLR OF CONFLICT, RETURNED TO 3000 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.