The crew of the Boeing 737 reported that when the speed brake was selected, during descent into Sydney with the autopilot engaged, the aircraft rolled slightly to the right. The autopilot was disengaged, and the speed brake was again selected with the same result. The speed brake was restowed and the flight continued and landed without further incident.
The operator reported that inspection of the aircraft, on 15 February 2001, revealed that the left-wing number three flight spoiler "UP" cable (P/No. WSA2-3) had failed at a pulley in the left wheel well at Wing Buttock Line (WBL) 73.00. The failure was due to corrosion as evidenced by rust deposits at the failure location. During rectification, all other left wing spoiler cables were replaced due to evidence of minor corrosion. Following repair, the aircraft was returned to service.
The operator reported that, after a previous spoiler cable failure in 1997 due to corrosion, an Engineering Release (ER) had been issued to require the inspection of all spoiler cables at the next Phase 20 check and subsequent 2C check with cable replacement at the next 4C check. Replacement at the 4C check terminated the inspection requirements of the ER.
As a result of the cable failure on 15 February 2001, the ER was revised to require inspection of the cables on an ongoing basis with cable replacement at every 4C check interval to preclude recurrence.
Subsequently, on 28 February 2001, the incident aircraft underwent overnight maintenance at Melbourne. During the maintenance inspection, the left-wing spoiler cables, that had previously been changed at Sydney on 15 February 2001, were found to be mis-routed. The operator's investigation revealed that the maintenance engineers involved in the original rectification had travelled from Brisbane to Sydney that day and had worked a period in excess of 24 hours with minimal breaks. Excessive hours worked and fatigue of the maintenance engineers was considered to have contributed to the misrouting of the cables and the failure to detect the misrouting during a duplicate inspection of the spoiler control system.