B727 altitude bust. Crew descended 400 ft below their cleared altitude on descent.

Attributes
ACN	404420
Time
Date	199805
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : orl airport : mco
State Reference	FL
Altitude	msl bound lower : 9600 msl bound upper : 11000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mco
Operator	common carrier : air carrier
Make Model Name	B727-200
Operating Under FAR Part	Part 121
Flight Phase	descent : approach descent other
Route In Use	arrival other enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
ASRS Report	404420
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	404422
Events
Anomaly	altitude deviation : overshoot non adherence : clearance non adherence : far
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

During descent to 10000 ft from 11000 ft received a TCASII TA alert for traffic above. Started a turn to 360 degrees. While monitoring traffic, allowed aircraft to descend to 9600 ft before catching the error. Stopped descent and leveled at 10000 ft. ATC asked if we were descending and we responded that we were leveling at 10000 ft. ATC responded that there was no problem. First officer and captain were both watching for traffic during the descent while the flight engineer was completing the checklist when descending through 10000 ft.

Original NASA ASRS Text

Title: B727 ALT BUST. CREW DSNDED 400 FT BELOW THEIR CLRED ALT ON DSCNT.

Narrative: DURING DSCNT TO 10000 FT FROM 11000 FT RECEIVED A TCASII TA ALERT FOR TFC ABOVE. STARTED A TURN TO 360 DEGS. WHILE MONITORING TFC, ALLOWED ACFT TO DSND TO 9600 FT BEFORE CATCHING THE ERROR. STOPPED DSCNT AND LEVELED AT 10000 FT. ATC ASKED IF WE WERE DSNDING AND WE RESPONDED THAT WE WERE LEVELING AT 10000 FT. ATC RESPONDED THAT THERE WAS NO PROB. FO AND CAPT WERE BOTH WATCHING FOR TFC DURING THE DSCNT WHILE THE FE WAS COMPLETING THE CHKLIST WHEN DSNDING THROUGH 10000 FT.

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.