DC10 flight crew overpwr autoplt from uncommanded descent.

Attributes
ACN	505476
Time
Date	200103
Day	Sat
Local Time Of Day	0001 To 0600
Place
Locale Reference	airport : mco.airport
State Reference	FL
Altitude	msl bound lower : 23600 msl bound upper : 25000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zjx.artcc
Operator	common carrier : air carrier
Make Model Name	DC-10 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : enroute altitude change
Route In Use	enroute other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : instrument pilot : flight engineer pilot : commercial pilot : cfi pilot : atp
Experience	flight time last 90 days : 100 flight time total : 13000 flight time type : 6000
ASRS Report	505476
Person 2
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : commercial pilot : flight engineer pilot : instrument pilot : multi engine pilot : private
Experience	flight time last 90 days : 210 flight time total : 7400 flight time type : 1900
ASRS Report	505371
Events
Anomaly	aircraft equipment problem : critical altitude deviation : overshoot other anomaly
Independent Detector	other flight crewa
Resolutory Action	aircraft : automation overrode flight crew controller : issued new clearance flight crew : overcame equipment problem flight crew : took precautionary avoidance action flight crew : overrode automation
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

Cleared to descend from FL310 to FL240. At FL250, autoplt initiated an uncommanded nose down pitch which reached nearly 6000 FPM. Manual control was attempted but autoplt would not disconnect. By overpwring the autoplt, manual control was regained, however, the resulting maneuver caused the airplane to level off at approximately FL236. ATC was immediately informed of the malfunction and the inability to level at FL240. ATC responded with an immediate descent clearance to 11000 ft. Remainder of flight in manual flight was normal.

Original NASA ASRS Text

Title: DC10 FLC OVERPWR AUTOPLT FROM UNCOMMANDED DSCNT.

Narrative: CLRED TO DSND FROM FL310 TO FL240. AT FL250, AUTOPLT INITIATED AN UNCOMMANDED NOSE DOWN PITCH WHICH REACHED NEARLY 6000 FPM. MANUAL CTL WAS ATTEMPTED BUT AUTOPLT WOULD NOT DISCONNECT. BY OVERPWRING THE AUTOPLT, MANUAL CTL WAS REGAINED, HOWEVER, THE RESULTING MANEUVER CAUSED THE AIRPLANE TO LEVEL OFF AT APPROX FL236. ATC WAS IMMEDIATELY INFORMED OF THE MALFUNCTION AND THE INABILITY TO LEVEL AT FL240. ATC RESPONDED WITH AN IMMEDIATE DSCNT CLRNC TO 11000 FT. REMAINDER OF FLT IN MANUAL FLT WAS NORMAL.

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.