<< >> NASA ASRS Report 673103, September 2005

A B747-200 was dispatched with the 'a' and 'B' yaw damper circuit breakers pulled for maintenance action and not reset.

Attributes
ACN	673103
Time
Date	200509
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	agl single value : 0
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B747-200
Operating Under FAR Part	Part 121
Person 1
Affiliation	company : air carrier
Function	maintenance : technician
Qualification	technician : powerplant technician : airframe
Experience	maintenance technician : 32
ASRS Report	673103
Person 2
Affiliation	company : air carrier
Function	maintenance : technician
Events
Anomaly	aircraft equipment problem : critical maintenance problem : improper maintenance maintenance problem : improper documentation non adherence : published procedure non adherence : far inflight encounter : weather
Independent Detector	other other : 3
Resolutory Action	none taken : detected after the fact
Consequence	other
Factors
Maintenance	contributing factor : non availability of parts contributing factor : schedule pressure performance deficiency : logbook entry performance deficiency : non compliance with legal requirements
Supplementary
Problem Areas	Flight Crew Human Performance Maintenance Human Performance Aircraft Company Environmental Factor
Primary Problem	Maintenance Human Performance

Narrative:

As a certified staff; a mechanic who is trained and able to certify an aircraft for flight for air carrier X; I was assigned to help an aircraft electronic tech to troubleshoot a yaw dampening system on a B747-200 cargo aircraft. This discrepancy was troubleshot in ZZZZ. Our system signed off as operations check good. Subsequently; the aircraft system took a hit and was written up on the inbound flight. I called for an aircraft electronic tech from air carrier Y; of which I'm an employee. The aircraft electronic tech tested the system by swapping the a and B computers. The trouble followed the swap and the aircraft electronic tech determined the 'a' system computer to be the cause. The aircraft electronic tech then placed the computer to the normal position. The aircraft electronic tech failed to reset the a and B yaw dampener circuit breakers. The MEL 22-16-00 was applied and the aircraft dispatched.

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Original NASA ASRS Text

Title: A B747-200 WAS DISPATCHED WITH THE 'A' AND 'B' YAW DAMPER CIRCUIT BREAKERS PULLED FOR MAINT ACTION AND NOT RESET.

Narrative: AS A CERTIFIED STAFF; A MECH WHO IS TRAINED AND ABLE TO CERTIFY AN ACFT FOR FLT FOR ACR X; I WAS ASSIGNED TO HELP AN ACFT ELECTRONIC TECH TO TROUBLESHOOT A YAW DAMPENING SYS ON A B747-200 CARGO ACFT. THIS DISCREPANCY WAS TROUBLESHOT IN ZZZZ. OUR SYS SIGNED OFF AS OPS CHK GOOD. SUBSEQUENTLY; THE ACFT SYS TOOK A HIT AND WAS WRITTEN UP ON THE INBOUND FLT. I CALLED FOR AN ACFT ELECTRONIC TECH FROM ACR Y; OF WHICH I'M AN EMPLOYEE. THE ACFT ELECTRONIC TECH TESTED THE SYS BY SWAPPING THE A AND B COMPUTERS. THE TROUBLE FOLLOWED THE SWAP AND THE ACFT ELECTRONIC TECH DETERMINED THE 'A' SYS COMPUTER TO BE THE CAUSE. THE ACFT ELECTRONIC TECH THEN PLACED THE COMPUTER TO THE NORMAL POS. THE ACFT ELECTRONIC TECH FAILED TO RESET THE A AND B YAW DAMPENER CIRCUIT BREAKERS. THE MEL 22-16-00 WAS APPLIED AND THE ACFT DISPATCHED.

Data retrieved from NASA's ASRS site as of January 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.