CL65 descended through assigned altitude and conflicted with an L188 at FL210 descending to FL190.

Attributes
ACN	593349
Time
Date	200309
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : vhp.vortac
State Reference	IN
Altitude	msl single value : 21000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid.artcc
Operator	common carrier : air carrier
Make Model Name	Regional Jet CL65, Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zid.artcc
Operator	common carrier : air carrier
Make Model Name	Electra L-188
Operating Under FAR Part	Part 121
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar pilot : instrument pilot : private
Experience	controller radar : 21.3 flight time total : 1400
ASRS Report	593349
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial pilot : cfi
Experience	flight time last 90 days : 210 flight time total : 3100 flight time type : 1100
ASRS Report	593350
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne critical non adherence : far non adherence : company policies non adherence : clearance non adherence : published procedure
Independent Detector	atc equipment : conflict alert atc equipment other atc equipment : radar/mode c aircraft equipment : tcas other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance flight crew : returned to assigned altitude other
Consequence	faa : investigated
Miss Distance	horizontal : 21000 vertical : 600
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Ambiguous

Narrative:

Aircraft #1 was cleared from FL240 to FL220. Pilot read back FL270 I noticed aircraft #2 passing through FL217. I asked to 'verify' at FL220. Pilot said 'no, we're going to FL200.' I climbed aircraft #1 back up to FL220 and descended other aircraft (aircraft #2) from FL210 to FL190. I told both aircraft to expedite. Aircraft #1 said he saw aircraft #2. Aircraft #1 never mentioned anything about any TCASII alert. Supplemental information from acn 593350: we were on the tarne 2 arrival into cincinnati at FL240. We were told to descend to FL200 and the captain, the PNF, repeated this and then confirmed with me and set FL200 in the altitude preselector. Passing through about FL210, the controller queried if we were leveling at FL220. The captain responded no, that we were descending to FL200. The controller then told us to discontinue descent and climb immediately up to FL220. At about this time we received a TA on the TCASII. The controller told us about traffic ahead and we reported that we had the traffic in sight. We immediately began a climb up to and leveled at FL220. We did not receive an RA and we did not hear anything else from the controller about the incident. I believe that I heard the controller clear us to descend to FL200 and my captain believes that he heard the same thing.

Original NASA ASRS Text

Title: CL65 DSNDED THROUGH ASSIGNED ALT AND CONFLICTED WITH AN L188 AT FL210 DSNDING TO FL190.

Narrative: ACFT #1 WAS CLRED FROM FL240 TO FL220. PLT READ BACK FL270 I NOTICED ACFT #2 PASSING THROUGH FL217. I ASKED TO 'VERIFY' AT FL220. PLT SAID 'NO, WE'RE GOING TO FL200.' I CLBED ACFT #1 BACK UP TO FL220 AND DSNDED OTHER ACFT (ACFT #2) FROM FL210 TO FL190. I TOLD BOTH ACFT TO EXPEDITE. ACFT #1 SAID HE SAW ACFT #2. ACFT #1 NEVER MENTIONED ANYTHING ABOUT ANY TCASII ALERT. SUPPLEMENTAL INFO FROM ACN 593350: WE WERE ON THE TARNE 2 ARR INTO CINCINNATI AT FL240. WE WERE TOLD TO DSND TO FL200 AND THE CAPT, THE PNF, REPEATED THIS AND THEN CONFIRMED WITH ME AND SET FL200 IN THE ALT PRESELECTOR. PASSING THROUGH ABOUT FL210, THE CTLR QUERIED IF WE WERE LEVELING AT FL220. THE CAPT RESPONDED NO, THAT WE WERE DSNDING TO FL200. THE CTLR THEN TOLD US TO DISCONTINUE DSCNT AND CLB IMMEDIATELY UP TO FL220. AT ABOUT THIS TIME WE RECEIVED A TA ON THE TCASII. THE CTLR TOLD US ABOUT TFC AHEAD AND WE RPTED THAT WE HAD THE TFC IN SIGHT. WE IMMEDIATELY BEGAN A CLB UP TO AND LEVELED AT FL220. WE DID NOT RECEIVE AN RA AND WE DID NOT HEAR ANYTHING ELSE FROM THE CTLR ABOUT THE INCIDENT. I BELIEVE THAT I HEARD THE CTLR CLR US TO DSND TO FL200 AND MY CAPT BELIEVES THAT HE HEARD THE SAME THING.

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.