Altitude deviation altitude overshot in evasive action descent after TCASII RA.

Attributes
ACN	239832
Time
Date	199304
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : obk airport : ord
State Reference	IL
Altitude	msl bound lower : 9500 msl bound upper : 10100
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : on vectors enroute airway : zau
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : flight engineer pilot : instrument pilot : commercial pilot : cfi
Experience	flight time total : 1600
ASRS Report	239832
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

TCASII system gave a false RA when we were descending through 10100 ft for 10000 ft. TCASII displayed an intruder at an 11 O'clock position from our aircraft at 200 ft above our altitude. The RA called for an immediate descent at a minimum rate of 1500 FPM. We immediately began a 4000 FPM descent and descended to 9500 ft before we were clear of conflict. We notified ATC promptly as we descended and climbed back to 10000 ft as soon as we were clear. We suspect a faulty TCASII system because ATC advised us that there was no such traffic in our vicinity. We asked him this after we were well into the descent.

Original NASA ASRS Text

Title: ALTDEV ALT OVERSHOT IN EVASIVE ACTION DSCNT AFTER TCASII RA.

Narrative: TCASII SYS GAVE A FALSE RA WHEN WE WERE DSNDING THROUGH 10100 FT FOR 10000 FT. TCASII DISPLAYED AN INTRUDER AT AN 11 O'CLOCK POS FROM OUR ACFT AT 200 FT ABOVE OUR ALT. THE RA CALLED FOR AN IMMEDIATE DSCNT AT A MINIMUM RATE OF 1500 FPM. WE IMMEDIATELY BEGAN A 4000 FPM DSCNT AND DSNDED TO 9500 FT BEFORE WE WERE CLR OF CONFLICT. WE NOTIFIED ATC PROMPTLY AS WE DSNDED AND CLBED BACK TO 10000 FT AS SOON AS WE WERE CLR. WE SUSPECT A FAULTY TCASII SYS BECAUSE ATC ADVISED US THAT THERE WAS NO SUCH TFC IN OUR VICINITY. WE ASKED HIM THIS AFTER WE WERE WELL INTO THE DSCNT.

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.