ZOB radar controller clears traffic into holding pattern to an occupied altitude.

Attributes
ACN	592118
Time
Date	200308
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	intersection : nakes
State Reference	OH
Altitude	msl single value : 18000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob.artcc
Operator	common carrier : air carrier
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : holding
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zob.artcc
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise : holding
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : commercial pilot : instrument pilot : multi engine
Experience	flight time last 90 days : 250 flight time total : 11000 flight time type : 600
ASRS Report	592118
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	conflict : airborne critical inflight encounter : weather non adherence : published procedure non adherence : required legal separation other anomaly other
Independent Detector	atc equipment other atc equipment : radar mode c aircraft equipment : tcas other controllera other flight crewa other flight crewb other other : 3
Resolutory Action	controller : issued advisory flight crew : took evasive action other
Consequence	faa : investigated
Miss Distance	horizontal : 1500 vertical : 0
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Flight to dtw was holding at nakes intersection, left turns, FL180. ZOB initially instructed us to hold at FL190, but changed the altitude to FL180 prior to us first arriving at the fix. Center was quite busy due to thunderstorms in the dtw area. After approximately 30-35 mins of hold, we heard the TCASII 'traffic, traffic' alert. I quickly expanded the range on my VNAV display to get a better awareness of the traffic's position. The traffic was at our 8 O'clock position, on a converging course, and in what appeared to be a hard left turn. After hearing the 'traffic' alert we heard 'climb, climb' immediately followed by 'descend, descend now.' the first officer quickly disconnected the autoplt, rolled wings level, and began a descent (all occurring simultaneously). I kept the traffic in sight, notified ATC of our RA and deviation, and advised the first officer when the traffic was no longer a factor. ATC apologized (more than once). He had obviously cleared 2 aircraft to occupy the same airspace at the same time. TCASII prevented a midair collision!

Original NASA ASRS Text

Title: ZOB RADAR CTLR CLRS TFC INTO HOLDING PATTERN TO AN OCCUPIED ALT.

Narrative: FLT TO DTW WAS HOLDING AT NAKES INTXN, L TURNS, FL180. ZOB INITIALLY INSTRUCTED US TO HOLD AT FL190, BUT CHANGED THE ALT TO FL180 PRIOR TO US FIRST ARRIVING AT THE FIX. CTR WAS QUITE BUSY DUE TO TSTMS IN THE DTW AREA. AFTER APPROX 30-35 MINS OF HOLD, WE HEARD THE TCASII 'TFC, TFC' ALERT. I QUICKLY EXPANDED THE RANGE ON MY VNAV DISPLAY TO GET A BETTER AWARENESS OF THE TFC'S POS. THE TFC WAS AT OUR 8 O'CLOCK POS, ON A CONVERGING COURSE, AND IN WHAT APPEARED TO BE A HARD L TURN. AFTER HEARING THE 'TFC' ALERT WE HEARD 'CLB, CLB' IMMEDIATELY FOLLOWED BY 'DSND, DSND NOW.' THE FO QUICKLY DISCONNECTED THE AUTOPLT, ROLLED WINGS LEVEL, AND BEGAN A DSCNT (ALL OCCURRING SIMULTANEOUSLY). I KEPT THE TFC IN SIGHT, NOTIFIED ATC OF OUR RA AND DEV, AND ADVISED THE FO WHEN THE TFC WAS NO LONGER A FACTOR. ATC APOLOGIZED (MORE THAN ONCE). HE HAD OBVIOUSLY CLRED 2 ACFT TO OCCUPY THE SAME AIRSPACE AT THE SAME TIME. TCASII PREVENTED A MIDAIR COLLISION!

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.