Air carrier medium large transport altitude deviation excursion from clearance altitude in response ...

Attributes
ACN	189718
Time
Date	199109
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ind
State Reference	IN
Altitude	msl bound lower : 10700 msl bound upper : 11000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 9000
ASRS Report	189718
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

ATC advised us of unknown traffic at 11-12 O'clock 500 ft above out altitude, unverified, crossing left to right at approximately 5 mi. We got a visual on that traffic just as we both were about to enter clouds. At that time the traffic was at 11:30-12 O'clock and our onboard TCASII system gave us an RA to descend. We descended approximately 300 ft and the TCASII announced that we were clear of conflict. We then advised center of our deviation and climbed back to our assigned altitude. Center advised us that they would try to identify this unknown aircraft.

Original NASA ASRS Text

Title: ACR MLG ALT DEV EXCURSION FROM CLRNC ALT IN RESPONSE TO TCASII RA.

Narrative: ATC ADVISED US OF UNKNOWN TFC AT 11-12 O'CLOCK 500 FT ABOVE OUT ALT, UNVERIFIED, XING L TO R AT APPROX 5 MI. WE GOT A VISUAL ON THAT TFC JUST AS WE BOTH WERE ABOUT TO ENTER CLOUDS. AT THAT TIME THE TFC WAS AT 11:30-12 O'CLOCK AND OUR ONBOARD TCASII SYS GAVE US AN RA TO DSND. WE DSNDED APPROX 300 FT AND THE TCASII ANNOUNCED THAT WE WERE CLR OF CONFLICT. WE THEN ADVISED CENTER OF OUR DEV AND CLBED BACK TO OUR ASSIGNED ALT. CENTER ADVISED US THAT THEY WOULD TRY TO IDENT THIS UNKNOWN ACFT.

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.

Air carrier medium large transport altitude deviation excursion from clearance altitude in response to TCASII RA.