B767-300 and 300 ER
Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Troubleshooting; Time Pressure; Communication Breakdown
Aircraft Equipment Problem Critical
General Flight Cancelled / Delayed; General Maintenance Action; General Release Refused / Aircraft Not Accepted
Human Factors; Company Policy; Aircraft; Procedure
Specifically; in our case; one of the AMT's test's of the Stick-Shaker Systems revealed that one was inoperative. Granted; this is not a system that is needed often; but when needed; it must operate at 100%. While possibly coincidental; we suspect that other safety systems may have been affected by this status message as well; and that this fault was never discovered or addressed. It concerns us that this fault may have existed the entire time these previous entries were being addressed; and that the aircraft continued to fly while one 'fix' after another failed to correct the problem. The Captain contacted Maintenance Control by phone and expressed his concern regarding the continued flights while accomplishing one fix after another. He also expressed his dissatisfaction with the discovery that the stick-shaker problem was just now discovered; after several previous logbook entries. According to the reaction of the Maintenance Technician in the cockpit running these tests; the problem was most likely related to the original entry. [Mechanic noted that] he 'accomplished the Fault Isolation per the Fault Isolation Manual (FIM) and replaced the Right-Hand Stall Warning Module but that did not help. He than troubleshot the wiring per the FIM and found Diode R843 high resistance and replaced'. The Stall Warning System Operational Test was successful.
Company Air Carrier flight; was to depart early morning August 2012. We ended up departing more than five hours later; after a tail (aircraft) swap to another B767 aircraft. The major cause for this delay was a safety-related concern regarding our maintenance log entry--the fifth for the same problem--on our original aircraft: a... 'WARN ELEX' EICAS status message. The previous four entries failed to correct the problem as we encountered the problem again during our pre-flight inspection. This series of repair failures suggests that our Air Carrier Aircraft Maintenance Technicians (AMTs) have insufficient diagnostic guidance from Boeing; and/or; that that guidance is poorly written; and/or; poorly followed. All of the possible options suggest a compromise in safety; a compromise that requires attention. Reporter stated he was becoming quite concern that a Maintenance Fault Tree Test path for troubleshooting the recurring 'WARN ELEX' EICAS status message problem was not effective. Flight crews and Maintenance personnel are under constant pressure to 'get the airplane out'. But; he was present in the flight deck with the Mechanic who did figure out what was the cause for the chronic EICAS message. He doesn't know if the Mechanic performed a Non-Standard Test; but he flipped a switch on a side panel and immediately realized one of the stick shakers was not functioning. From there; he replaced a failed diode after replacement of the right-hand stall warning module did not help. Reporter stated that with one of the stick shakers inoperative for the whole time; if they had; had an electrical failure occur on the electrical bus that powered the 'Good' stick shaker; they would not have had a primary stall warning indicator functional in flight. Their Pre-Flight Checklist does not include a Stick-Shaker Test.
Recommend aircraft should not be continually worked on by changing one part at a time and then flight tested with passengers onboard. From the conversation that took place in the cockpit with the Maintenance personnel involved; it seemed apparent that this B767-300 aircraft was constantly being flown without a sure remedy for the problem. I consider this a safety issue that was stopped; only because I took the time to call Maintenance Control; and I made it clear that I thought what was going on was not appropriate. Had I not called; I strongly suspect I would have been sent on my way for another Test Flight with passengers. I commented more than once; where was the checklist that insured all related systems were checked. I never saw one.
Two pilots report about a recurring 'WARN ELEX' EICAS Status message on a B767-300 aircraft that had been written-up and signed-off multiple times without correcting the problem. Aircraft Maintenance Technician (AMT) isolated the fault to a diode with high resistance; but also noted that one of the stick-shakers was probably inoperative the entire time.