An MD80 in cruise at FL330 declared an emergency due to autoplt and autothrottles disengaged with master caution yaw damper and mach trim inoperative lights. After landing found dfg 'a' circuit breaker tripped.

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Attributes
ACN	494217
Time
Date	200012
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : atl.airport
State Reference	GA
Altitude	msl single value : 33000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sbgr.tracon
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Route In Use	enroute airway : j4.airway
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : commercial pilot : instrument
ASRS Report	494217
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : master caution light other flight crewa other flight crewb
Resolutory Action	flight crew : declared emergency
Consequence	other other
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Aircraft

Narrative:

Cruising at FL330, autoplt and autothrottles disengaged seemingly concurrent with master caution yaw damper off and mach trim inoperative lights. Flew aircraft in to atl with only slightly degraded control due to yaw damper inoperative. Occasionally, during speed and trim changes, we could feel the tail yaw. We notified the flight attendants of condition and they reported a slight feeling of abnormal aircraft movement and no unusual noises. The captain and I could not locate any suitable abnormal procedures to match aircraft condition. After it was imminent that we were going to get vectors and prominent speed changes, the captain declared an emergency and we landed without incident. After landing, while waiting for traffic, we noticed the C17 dfg system 'a' circuit breaker was popped.

Original NASA ASRS Text

Title: AN MD80 IN CRUISE AT FL330 DECLARED AN EMER DUE TO AUTOPLT AND AUTOTHROTTLES DISENGAGED WITH MASTER CAUTION YAW DAMPER AND MACH TRIM INOP LIGHTS. AFTER LNDG FOUND DFG 'A' CIRCUIT BREAKER TRIPPED.

Narrative: CRUISING AT FL330, AUTOPLT AND AUTOTHROTTLES DISENGAGED SEEMINGLY CONCURRENT WITH MASTER CAUTION YAW DAMPER OFF AND MACH TRIM INOP LIGHTS. FLEW ACFT IN TO ATL WITH ONLY SLIGHTLY DEGRADED CTL DUE TO YAW DAMPER INOP. OCCASIONALLY, DURING SPD AND TRIM CHANGES, WE COULD FEEL THE TAIL YAW. WE NOTIFIED THE FLT ATTENDANTS OF CONDITION AND THEY RPTED A SLIGHT FEELING OF ABNORMAL ACFT MOVEMENT AND NO UNUSUAL NOISES. THE CAPT AND I COULD NOT LOCATE ANY SUITABLE ABNORMAL PROCS TO MATCH ACFT CONDITION. AFTER IT WAS IMMINENT THAT WE WERE GOING TO GET VECTORS AND PROMINENT SPD CHANGES, THE CAPT DECLARED AN EMER AND WE LANDED WITHOUT INCIDENT. AFTER LNDG, WHILE WAITING FOR TFC, WE NOTICED THE C17 DFG SYS 'A' CIRCUIT BREAKER WAS POPPED.

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.