Altitude deviation overshot on descent.

Attributes
ACN	123112
Time
Date	198909
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : mco
State Reference	FL
Altitude	msl bound lower : 8000 msl bound upper : 9000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mco
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 35 flight time total : 9800 flight time type : 35
ASRS Report	123112
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot non adherence : clearance
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Ambiguous
Air Traffic Incident	Pilot Deviation

Narrative:

Regarding the incident in question, I am not sure if the controller gave us an altitude to descend to and we correct set, verified, and descended to that altitude and he changed his mind, or, we set, did not verify long enough and descended thru the assigned altitude due to a 1000' downward jump in the MCP. As we reached 8000' the controller said level off at 9000'. An unusual call. We climbed back up to 9000'.

Original NASA ASRS Text

Title: ALT DEVIATION OVERSHOT ON DESCENT.

Narrative: REGARDING THE INCIDENT IN QUESTION, I AM NOT SURE IF THE CTLR GAVE US AN ALT TO DSND TO AND WE CORRECT SET, VERIFIED, AND DESCENDED TO THAT ALT AND HE CHANGED HIS MIND, OR, WE SET, DID NOT VERIFY LONG ENOUGH AND DESCENDED THRU THE ASSIGNED ALT DUE TO A 1000' DOWNWARD JUMP IN THE MCP. AS WE REACHED 8000' THE CTLR SAID LEVEL OFF AT 9000'. AN UNUSUAL CALL. WE CLIMBED BACK UP TO 9000'.

Data retrieved from NASA's ASRS site as of August 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.