An air carrier captain, on approach, descended before being cleared by mco.

Attributes
ACN	514070
Time
Date	200106
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : mco.airport
State Reference	FL
Altitude	msl bound lower : 4500 msl bound upper : 5000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : lhd.tower
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Flight Phase	descent : approach
Route In Use	arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 260 flight time total : 10000 flight time type : 2000
ASRS Report	514070
Events
Anomaly	altitude deviation : overshoot non adherence : clearance non adherence : company policies non adherence : far non adherence : published procedure
Resolutory Action	controller : issued new clearance
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

On approach into mco, given turn to 250 degrees, descended to 4000 ft. Next controller gave us a right turn to 250 degrees and descent to 5000 ft. Confirmed we were now cleared to 5000 ft. We were next given a heading to intercept the runway 17 localizer. We were already high on the GS. I started to descend, got an altitude alert and realized we hadn't been cleared out of 5000 ft. The controller then cleared us for the approach. We descended 400 ft or 500 ft below 5000 ft before receiving the approach clearance.

Original NASA ASRS Text

Title: AN ACR CAPT, ON APCH, DSNDED BEFORE BEING CLRED BY MCO.

Narrative: ON APCH INTO MCO, GIVEN TURN TO 250 DEGS, DSNDED TO 4000 FT. NEXT CTLR GAVE US A R TURN TO 250 DEGS AND DSCNT TO 5000 FT. CONFIRMED WE WERE NOW CLRED TO 5000 FT. WE WERE NEXT GIVEN A HEADING TO INTERCEPT THE RWY 17 LOC. WE WERE ALREADY HIGH ON THE GS. I STARTED TO DSND, GOT AN ALT ALERT AND REALIZED WE HADN'T BEEN CLRED OUT OF 5000 FT. THE CTLR THEN CLRED US FOR THE APCH. WE DSNDED 400 FT OR 500 FT BELOW 5000 FT BEFORE RECEIVING THE APCH CLRNC.

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.