A B757-200 responded to a TCASII in holding approaching ord by descending slightly to avoid a king a...

Attributes
ACN	658859
Time
Date	200505
Local Time Of Day	1201 To 1800
Place
Locale Reference	intersection : benky
State Reference	IL
Altitude	msl single value : 12000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau.artcc
Operator	common carrier : air carrier
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zau.artcc
Make Model Name	Super King Air 200 HDC
Flight Phase	cruise : level
Flight Plan	VFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
ASRS Report	658859
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : nmac
Independent Detector	aircraft equipment : tcas
Resolutory Action	flight crew : took evasive action
Miss Distance	vertical : 300
Supplementary
Problem Areas	Airspace Structure ATC Human Performance Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

Holding at benky intersection turning outbound we received a TCASII 'traffic' alert followed by ATC issuing a traffic warning for a VFR aircraft at our 1 O'clock position climbing out of 11000 ft. We visually acquired -- we were behind and slightly to the left of the target aircraft; but we were closing. Soon thereafter; we were issued a 'climb; climb now' advisory from TCASII. The target was then 300 ft below us climbing and we were approximately 1 mi and closing slowly. We judged that if we initiated a climb that we would increase the conflict. Also; other aircraft were holding above. Shortly thereafter; we received and responded to a 'descend' command from TCASII and leveled at 11700 ft passing under the VFR target as it continued to climb. The conflict aircraft was a beech king air (large type; perhaps a -400). We notified ATC and returned to 12000 ft.

Original NASA ASRS Text

Title: A B757-200 RESPONDED TO A TCASII IN HOLDING APCHING ORD BY DSNDING SLIGHTLY TO AVOID A KING AIR BY 300 FT.

Narrative: HOLDING AT BENKY INTXN TURNING OUTBOUND WE RECEIVED A TCASII 'TFC' ALERT FOLLOWED BY ATC ISSUING A TFC WARNING FOR A VFR ACFT AT OUR 1 O'CLOCK POS CLBING OUT OF 11000 FT. WE VISUALLY ACQUIRED -- WE WERE BEHIND AND SLIGHTLY TO THE L OF THE TARGET ACFT; BUT WE WERE CLOSING. SOON THEREAFTER; WE WERE ISSUED A 'CLB; CLB NOW' ADVISORY FROM TCASII. THE TARGET WAS THEN 300 FT BELOW US CLBING AND WE WERE APPROX 1 MI AND CLOSING SLOWLY. WE JUDGED THAT IF WE INITIATED A CLB THAT WE WOULD INCREASE THE CONFLICT. ALSO; OTHER ACFT WERE HOLDING ABOVE. SHORTLY THEREAFTER; WE RECEIVED AND RESPONDED TO A 'DSND' COMMAND FROM TCASII AND LEVELED AT 11700 FT PASSING UNDER THE VFR TARGET AS IT CONTINUED TO CLB. THE CONFLICT ACFT WAS A BEECH KING AIR (LARGE TYPE; PERHAPS A -400). WE NOTIFIED ATC AND RETURNED TO 12000 FT.

Data retrieved from NASA's ASRS site as of January 2009 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.

A B757-200 responded to a TCASII in holding approaching ord by descending slightly to avoid a king air by 300 ft.