A CL65 flight crew misunderstands clearance and descends 1000 ft low resulting in a TCASII RA.

Attributes
ACN	521760
Time
Date	200108
Day	Sun
Place
Locale Reference	navaid : orl.vortac
State Reference	FL
Altitude	msl bound lower : 10000 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Regional Jet CL65, Undifferentiated or Other Model
Flight Phase	descent : intermediate altitude
Route In Use	arrival star : goofy 4
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 50 flight time total : 3200 flight time type : 1000
ASRS Report	521760
Events
Anomaly	altitude deviation : overshoot conflict : airborne critical non adherence : published procedure non adherence : clearance
Resolutory Action	flight crew : took precautionary avoidance action flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Flight to orlando, fl, on aug/sun/01. At approximately 37 mi from orl on the goofy 4 arrival, ZMA gave us a descent to 11000 ft MSL. I heard and read back 10000 ft MSL. Descending through 11000 ft, we noticed another aircraft on the same arrival at 10000 ft that was noticeably slower. First officer slowed descent rate and leveled aircraft at approximately 10500 ft MSL. We then received a TCASII TA followed by a TCASII RA. Orlando approach control issued a turn to our right approximately 30 degrees. We advised that we had the traffic in sight and turned to the new heading. Also, upon checking in with orlando approach, we advised them of our descent to 10000 ft MSL. The RA was resolved with the heading change and we were vectored for a visual approach to runway 17L at mco. Approach and landing were uneventful.

Original NASA ASRS Text

Title: A CL65 FLT CREW MISUNDERSTANDS CLRNC AND DSNDS 1000 FT LOW RESULTING IN A TCASII RA.

Narrative: FLT TO ORLANDO, FL, ON AUG/SUN/01. AT APPROX 37 MI FROM ORL ON THE GOOFY 4 ARR, ZMA GAVE US A DSCNT TO 11000 FT MSL. I HEARD AND READ BACK 10000 FT MSL. DSNDING THROUGH 11000 FT, WE NOTICED ANOTHER ACFT ON THE SAME ARR AT 10000 FT THAT WAS NOTICEABLY SLOWER. FO SLOWED DSCNT RATE AND LEVELED ACFT AT APPROX 10500 FT MSL. WE THEN RECEIVED A TCASII TA FOLLOWED BY A TCASII RA. ORLANDO APCH CTL ISSUED A TURN TO OUR R APPROX 30 DEGS. WE ADVISED THAT WE HAD THE TFC IN SIGHT AND TURNED TO THE NEW HDG. ALSO, UPON CHKING IN WITH ORLANDO APCH, WE ADVISED THEM OF OUR DSCNT TO 10000 FT MSL. THE RA WAS RESOLVED WITH THE HDG CHANGE AND WE WERE VECTORED FOR A VISUAL APCH TO RWY 17L AT MCO. APCH AND LNDG WERE UNEVENTFUL.

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.