|37000 Feet||Browse and search NASA's
Aviation Safety Reporting System
|Local Time Of Day||1201 To 1800|
|Locale Reference||airport : zzz.airport|
|Altitude||msl single value : 37000|
|Operator||common carrier : air carrier|
|Make Model Name||MD-80 Super 80|
|Operating Under FAR Part||Part 121|
|Flight Phase||cruise : level|
|Affiliation||company : air carrier|
|Function||flight crew : captain|
oversight : pic
|Qualification||pilot : atp|
|Affiliation||company : air carrier|
|Function||flight crew : first officer|
|Anomaly||aircraft equipment problem : critical|
other anomaly other
|Independent Detector||aircraft equipment other aircraft equipment : autoplt and autothrottle disconnect|
other flight crewa
other flight crewb
|Problem Areas||Maintenance Human Performance|
After established at FL370 for cruise the automatic pilot and automatic throttles disconnected and circuit breaker-C18 (digital flight guidance system switch) popped. The aircraft yawed right then left. I was concerned about an upset and started a descent while the first officer got a clearance from ATC. The digital flight guidance panel was inoperative on 1 and 2. The altitude alert system was frozen. The speed command bug was frozen and the pms was inoperative. Because of the yaw we disconnected the yaw damper system and descended in steps to FL240. We hand flew the rest of the trip and approach. Maintenance in contact with ZZZ1 tech, changed the flight guidance panel and reset the circuit breaker and cleared us for departure back to ZZZ. Passing about 13000 ft the circuit breaker tripped again with the same results. We again advised ATC of our problem and continued to ZZZ. Callback conversation with reporter revealed the following information: the reporter stated the first incident occurred at FL370. The autoplt and automatic throttles disconnected and a circuit breaker tripped. The reporter said the airplane yawed to the right, held momentarily then centered, then yawed to the left held momentarily then centered. The reporter stated the yaw damper was switched off and the airplane hand flown. The reporter said after maintenance replaced the flight guidance panel and tested per the maintenance manual the airplane was then dispatched. The reporter said climbing through 13000 ft the discrepancy was repeated again and the airplane was hand flown to the trip termination. The reporter stated the airplane was removed from service and was found to have a broken wire on the dual elevator servo drive unit.
Original NASA ASRS Text
Title: AN MD80 WAS DISPATCHED AFTER REPLACEMENT OF THE FLT GUIDANCE PANEL, AT 13000 FT HAD AUTOPLT AND AUTO THROTTLES DISCONNECT AND CIRCUIT BREAKER TRIP. ACFT YAWED R AND THEN L.
Narrative: AFTER ESTABLISHED AT FL370 FOR CRUISE THE AUTO PLT AND AUTO THROTTLES DISCONNECTED AND CB-C18 (DIGITAL FLT GUIDANCE SYSTEM SWITCH) POPPED. THE ACFT YAWED R THEN L. I WAS CONCERNED ABOUT AN UPSET AND STARTED A DSCNT WHILE THE FO GOT A CLRNC FROM ATC. THE DIGITAL FLT GUIDANCE PANEL WAS INOP ON 1 AND 2. THE ALTITUDE ALERT SYSTEM WAS FROZEN. THE SPEED COMMAND BUG WAS FROZEN AND THE PMS WAS INOP. BECAUSE OF THE YAW WE DISCONNECTED THE YAW DAMPER SYSTEM AND DSNDED IN STEPS TO FL240. WE HAND FLEW THE REST OF THE TRIP AND APCH. MAINT IN CONTACT WITH ZZZ1 TECH, CHANGED THE FLT GUIDANCE PANEL AND RESET THE CB AND CLRED US FOR DEP BACK TO ZZZ. PASSING ABOUT 13000 FT THE CB TRIPPED AGAIN WITH THE SAME RESULTS. WE AGAIN ADVISED ATC OF OUR PROB AND CONTINUED TO ZZZ. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE FIRST INCIDENT OCCURRED AT FL370. THE AUTOPLT AND AUTO THROTTLES DISCONNECTED AND A CIRCUIT BREAKER TRIPPED. THE RPTR SAID THE AIRPLANE YAWED TO THE RIGHT, HELD MOMENTARILY THEN CENTERED, THEN YAWED TO THE LEFT HELD MOMENTARILY THEN CENTERED. THE RPTR STATED THE YAW DAMPER WAS SWITCHED OFF AND THE AIRPLANE HAND FLOWN. THE RPTR SAID AFTER MAINT REPLACED THE FLT GUIDANCE PANEL AND TESTED PER THE MAINT MANUAL THE AIRPLANE WAS THEN DISPATCHED. THE RPTR SAID CLBING THROUGH 13000 FT THE DISCREPANCY WAS REPEATED AGAIN AND THE AIRPLANE WAS HAND FLOWN TO THE TRIP TERMINATION. THE RPTR STATED THE AIRPLANE WAS REMOVED FROM SVC AND WAS FOUND TO HAVE A BROKEN WIRE ON THE DUAL ELEVATOR SERVO DRIVE UNIT.
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.