An air carrier medium large transport turned and descended in response to a TCASII command.

Attributes
ACN	248108
Time
Date	199308
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : svm airport : dtw
State Reference	MI
Altitude	msl bound lower : 12000 msl bound upper : 12000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Retractable Gear
Flight Phase	cruise other
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 13000 flight time type : 6500
ASRS Report	248108
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 210 flight time total : 12000 flight time type : 9000
ASRS Report	248114
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : nmac other anomaly other other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	vertical : 400
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Deviation Pilot Deviation

Narrative:

Climbing through about 12000 ft at about 280 KTS, TCASII announced a conflict 'stop climb' once, then 'descend, descend now.' the captain, who was flying, took timely evasive action, rolling left and descending. The TCASII showed a vertical separation of 400 ft and we both spotted what appeared to be a single engine small aircraft directly overhead. I estimate the lateral separation at this point to be '0.' we advised ZOB of our evasive action and reported the aircraft overhead. We inquired if they had the traffic on radar. First response, 'he must be working detroit approach.' then another voice came on the air saying that 'we spotted the traffic just as you reported it' and then he apologized for the problem and switched us to another frequency. No injuries to passenger or crew resulted from the evasive maneuver. The head on profile of the small aircraft made him very hard to spot. I believe that a collision could very likely have occurred if not for TCASII.

Original NASA ASRS Text

Title: AN ACR MLG TURNED AND DSNDED IN RESPONSE TO A TCASII COMMAND.

Narrative: CLBING THROUGH ABOUT 12000 FT AT ABOUT 280 KTS, TCASII ANNOUNCED A CONFLICT 'STOP CLB' ONCE, THEN 'DSND, DSND NOW.' THE CAPT, WHO WAS FLYING, TOOK TIMELY EVASIVE ACTION, ROLLING L AND DSNDING. THE TCASII SHOWED A VERT SEPARATION OF 400 FT AND WE BOTH SPOTTED WHAT APPEARED TO BE A SINGLE ENG SMA DIRECTLY OVERHEAD. I ESTIMATE THE LATERAL SEPARATION AT THIS POINT TO BE '0.' WE ADVISED ZOB OF OUR EVASIVE ACTION AND RPTED THE ACFT OVERHEAD. WE INQUIRED IF THEY HAD THE TFC ON RADAR. FIRST RESPONSE, 'HE MUST BE WORKING DETROIT APCH.' THEN ANOTHER VOICE CAME ON THE AIR SAYING THAT 'WE SPOTTED THE TFC JUST AS YOU RPTED IT' AND THEN HE APOLOGIZED FOR THE PROB AND SWITCHED US TO ANOTHER FREQ. NO INJURIES TO PAX OR CREW RESULTED FROM THE EVASIVE MANEUVER. THE HEAD ON PROFILE OF THE SMA MADE HIM VERY HARD TO SPOT. I BELIEVE THAT A COLLISION COULD VERY LIKELY HAVE OCCURRED IF NOT FOR TCASII.

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.