An MD80 pilot reports primary horizontal stabilizer trim control failure and that the stabilizer tri...

Narrative:

Descending on vectors; the first officer who was hand flying reported that he didn't have any stabilizer trim. I briefly took the airplane and tried my trim and the suitcase handles without success and gave the airplane back to the first officer. I turned on the circuit breaker lighting and looked at the panel behind me but didn't see any breakers out. First lesson: it's best on the MD80 to have the right seat look for breakers as he/she has the best angle. I had missed the stabilizer trim brake circuit breaker as it was behind my O2 hose and shadowed in the corner of the panel. I had been more focused on the 3 on the gen bus circuit breaker panel. I got out the QRH and flight-C 1 stabilizer inoperative in-flight. Reviewing the circuit breaker list in the checklist I found the brake circuit breaker popped. After the cool down period we reset the breaker which popped after several seconds. We left it out. First officer utilized the autoplt to trim until inside of 1000 ft on final and landed without incident. Subsequent inspection by maintenance revealed the frame is arced all the way through as well as the inner pulley. There is also some aircraft damage as reported to me by the chief pilot. It was also brought to my attention that the circuit breaker is a 3-PHASE; single breaker.callback conversation with reporter revealed the following information: reporter stated neither his; nor the co-pilot's; horizontal stabilizer primary electrical trim switches on their control wheel would function. The mechanical control dual 'suitcase' handles also would not operate the horizontal stabilizer trim. The stabilizer trim brake circuit breaker had popped and would not hold a reset. Reporter stated maintenance found the stabilizer brake electrical wire bundle for the primary system motor drive had arced and welded to a frame support in the stabilizer compartment. This shorted and grounded the wire bundle causing the circuit breaker to pop. The brake function side of the 'suitcase' mechanical handles could not function because the burnt wire bundle was downstream of the brake control relays.

Original NASA ASRS Text

Title: AN MD80 PLT RPTS PRIMARY HORIZ STAB TRIM CONTROL FAILURE AND THAT THE STAB TRIM BRAKE CIRCUIT BREAKER TRIPPED WHILE DSNDING ON VECTORS TO RWY. PROB WAS TRACED TO A FAILED WIRE BUNDLE; WHICH ARCED AND PURPORTEDLY WELDED ITSELF TO THE FRAME SUPPORT.

Narrative: DSNDING ON VECTORS; THE FO WHO WAS HAND FLYING RPTED THAT HE DIDN'T HAVE ANY STABILIZER TRIM. I BRIEFLY TOOK THE AIRPLANE AND TRIED MY TRIM AND THE SUITCASE HANDLES WITHOUT SUCCESS AND GAVE THE AIRPLANE BACK TO THE FO. I TURNED ON THE CB LIGHTING AND LOOKED AT THE PANEL BEHIND ME BUT DIDN'T SEE ANY BREAKERS OUT. FIRST LESSON: IT'S BEST ON THE MD80 TO HAVE THE R SEAT LOOK FOR BREAKERS AS HE/SHE HAS THE BEST ANGLE. I HAD MISSED THE STAB TRIM BRAKE CB AS IT WAS BEHIND MY O2 HOSE AND SHADOWED IN THE CORNER OF THE PANEL. I HAD BEEN MORE FOCUSED ON THE 3 ON THE GEN BUS CB PANEL. I GOT OUT THE QRH AND FLT-C 1 STABILIZER INOPERATIVE IN-FLT. REVIEWING THE CB LIST IN THE CHKLIST I FOUND THE BRAKE CB POPPED. AFTER THE COOL DOWN PERIOD WE RESET THE BREAKER WHICH POPPED AFTER SEVERAL SECONDS. WE LEFT IT OUT. FO UTILIZED THE AUTOPLT TO TRIM UNTIL INSIDE OF 1000 FT ON FINAL AND LANDED WITHOUT INCIDENT. SUBSEQUENT INSPECTION BY MAINT REVEALED THE FRAME IS ARCED ALL THE WAY THROUGH AS WELL AS THE INNER PULLEY. THERE IS ALSO SOME ACFT DAMAGE AS RPTED TO ME BY THE CHIEF PLT. IT WAS ALSO BROUGHT TO MY ATTENTION THAT THE CB IS A 3-PHASE; SINGLE BREAKER.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED NEITHER HIS; NOR THE CO-PILOT'S; HORIZ STAB PRIMARY ELECTRICAL TRIM SWITCHES ON THEIR CONTROL WHEEL WOULD FUNCTION. THE MECHANICAL CONTROL DUAL 'SUITCASE' HANDLES ALSO WOULD NOT OPERATE THE HORIZ STAB TRIM. THE STAB TRIM BRAKE CB HAD POPPED AND WOULD NOT HOLD A RESET. RPTR STATED MAINT FOUND THE STAB BRAKE ELECTRICAL WIRE BUNDLE FOR THE PRIMARY SYSTEM MOTOR DRIVE HAD ARCED AND WELDED TO A FRAME SUPPORT IN THE STAB COMPARTMENT. THIS SHORTED AND GROUNDED THE WIRE BUNDLE CAUSING THE CB TO POP. THE BRAKE FUNCTION SIDE OF THE 'SUITCASE' MECHANICAL HANDLES COULD NOT FUNCTION BECAUSE THE BURNT WIRE BUNDLE WAS DOWNSTREAM OF THE BRAKE CONTROL RELAYS.

Data retrieved from NASA's ASRS site as of May 2009 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.

Attributes
ACN	786758
Time
Date	200805
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 8000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : zzz.tracon
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Route In Use	arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
ASRS Report	786758
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	other other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

An MD80 pilot reports primary horizontal stabilizer trim control failure and that the stabilizer trim brake circuit breaker tripped while descending on vectors to runway. Problem was traced to a failed wire bundle; which arced and purportedly welded itself to the frame support.