Air carrier X TCASII RA with VFR aircraft. See and avoid concept.

Attributes
ACN	247010
Time
Date	199306
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ord
State Reference	IL
Altitude	msl bound lower : 10500 msl bound upper : 11000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ord
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	VFR
Person 1
Affiliation	government : faa
Function	other personnel other
Qualification	controller : radar
ASRS Report	247010
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	vertical : 800
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Air carrier X said he was climbing due to a TCASII RA. The controller then noticed a VFR target Y showing 10500 ft on mode C. The VFR's transponder appeared intermittent. The VFR's mode C was verified by another aircraft. Air carrier X advised when he had returned to assigned altitude. There was an altitude deviation of at least 300 ft by the TCASII aircraft. Communications did not take place until after the TCASII maneuver.

Original NASA ASRS Text

Title: ACR X TCASII RA WITH VFR ACFT. SEE AND AVOID CONCEPT.

Narrative: ACR X SAID HE WAS CLBING DUE TO A TCASII RA. THE CTLR THEN NOTICED A VFR TARGET Y SHOWING 10500 FT ON MODE C. THE VFR'S XPONDER APPEARED INTERMITTENT. THE VFR'S MODE C WAS VERIFIED BY ANOTHER ACFT. ACR X ADVISED WHEN HE HAD RETURNED TO ASSIGNED ALT. THERE WAS AN ALTDEV OF AT LEAST 300 FT BY THE TCASII ACFT. COMS DID NOT TAKE PLACE UNTIL AFTER THE TCASII MANEUVER.

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.