Aircraft equipment problem malfunction mandates immediate altitude deviation altitude excursion.

Attributes
ACN	239518
Time
Date	199304
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : mem
State Reference	TN
Altitude	msl bound lower : 31000 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zme
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	cruise other other 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 : 180 flight time total : 14000 flight time type : 5500
ASRS Report	239518
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 2500 flight time type : 200
ASRS Report	239568
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly
Independent Detector	other flight crewa
Resolutory Action	flight crew : exited adverse environment flight crew : overcame equipment problem flight crew : declared emergency other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

While at cruise at FL310, the autoplt and automatic throttles disconnected, the digital flight guidance failed with annunciators yaw damp off, mach trim inoperative and altitude alert off. The aircraft began dutch-rolling. We stabilized aircraft and began to run abnormal checklist 'aircraft oscillating and yaw displacement.' we found circuit breaker for dfgc switch 'a' popped. Checklist called to select second dfgc. After it was selected to no avail we reinstated circuit breaker and aircraft began a moderate dutch roll. We pulled circuit breaker and advised ZME we were leaving FL310 with a flight control problem and we were going to divert into mem. As we continued the checklist during descent the aircraft stabilized when rudder control was moved to manual. As we approached mem, asked to have equipment standing by. Landed without any problems.

Original NASA ASRS Text

Title: ACFT EQUIP PROB MALFUNCTION MANDATES IMMEDIATE ALTDEV ALT EXCURSION.

Narrative: WHILE AT CRUISE AT FL310, THE AUTOPLT AND AUTO THROTTLES DISCONNECTED, THE DIGITAL FLT GUIDANCE FAILED WITH ANNUNCIATORS YAW DAMP OFF, MACH TRIM INOP AND ALT ALERT OFF. THE ACFT BEGAN DUTCH-ROLLING. WE STABILIZED ACFT AND BEGAN TO RUN ABNORMAL CHKLIST 'ACFT OSCILLATING AND YAW DISPLACEMENT.' WE FOUND CIRCUIT BREAKER FOR DFGC SWITCH 'A' POPPED. CHKLIST CALLED TO SELECT SECOND DFGC. AFTER IT WAS SELECTED TO NO AVAIL WE REINSTATED CIRCUIT BREAKER AND ACFT BEGAN A MODERATE DUTCH ROLL. WE PULLED CIRCUIT BREAKER AND ADVISED ZME WE WERE LEAVING FL310 WITH A FLT CTL PROB AND WE WERE GOING TO DIVERT INTO MEM. AS WE CONTINUED THE CHKLIST DURING DSCNT THE ACFT STABILIZED WHEN RUDDER CTL WAS MOVED TO MANUAL. AS WE APCHED MEM, ASKED TO HAVE EQUIP STANDING BY. LANDED WITHOUT ANY PROBS.

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.