Aviation safety investigations & reports

Boeing Co 737-33A, VH-CZX

Investigation number:
Status: Completed
Investigation completed


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 mis-routing of the cables and the failure to detect the mis-routing during a duplicate inspection of the spoiler control system.

Safety Action

As a result of this ocurrence, the aircraft operator updated the Flight Spoiler System Engineering Release to ensure the continued integrity of B737 spoiler cables. In addition, the operator subsequently reviewed the duty time limitations for maintenance personnel and issued guidance material indicating that duty times be limited to a maximum of 16 hours in any 24 hour period.

In February 2001, The Australian Transport Safety Bureau (ATSB) released an Air Safety Information Paper titled "ATSB Survey of Licenced Aircraft Maintenance Engineers in Australia" One of the safety deficiencies identified during the survey was a "current lack of programs to limit the extent of fatigue experienced by maintenance workers". As a result of that deficiency, the ATSB issued the following safety recommendation to the Civil Aviation Safety Authority (CASA):

R20010033 issued February 2001

"The Australian Transport Safety Bureau recommends that CASA ensures through hours of duty limits, or other means, that maintenance organisations manage work schedules of staff in a manner that reduces the likelihood of those staff suffering from excessive levels of fatigue while on duty."

The Civil Aviation Safety Authority responded to the safety recommendation on 31 August 2001. That response stated:

"Given that "fatigue was listed as a contributing factor in just over 12% of occurrences", CASA believes that there is clearly a need for the appropriate regulation of this issue.

CASA has addressed the issue of hours of duty rules and fatigue management in relation to aircraft maintenance engineers in the proposed Civil Aviation Safety Regulations Part 43 -Maintainers Responsibilities and Part 145 - Approved Maintenance Organisations, (CASR Part 43 and CASR Part 145).

Draft regulations for CASR Part 43 were released as a Discussion Paper for public comment on 22 February 2001. A working draft of the proposed regulations for CASR Part 145 was released for public comment on 5 July 2001.

Proposed sub-regulation 145.190 requires an approved maintenance organisation to ensure that each maintenance worker takes enough rest as specified in CASR Part 43.

Proposed sub-regulation 43.400 (2) specifies the following in relation to an appropriate work schedule for a maintenance worker:

At least 1 period of 24 hours of complete rest away from the workplace in any period of seven days; and

At least 10 hours of complete rest away from the workplace in any day.

Proposed sub-regulation 43.400 (3) provides that a maintenance worker must not continue for so long a period that the worker's capacity to carry out the work becomes significantly impaired.

I would like to note that the Authority has recently established a Fatigue Management Committee to review fatigue risk management issues, fatigue standards development and implementation.

As part of this review, the Committee will be asked to review the fatigue regulations contained in CASR Parts 43 and 145, for consistency against CASA's fatigue management approach.

CASA anticipates that following consideration and, if appropriate, incorporation of comments received from interested parties, including the Fatigue Management Committee, CASR Parts 43 and Part 145 will be released as Notices of Proposed Rule Makings for public comment later this year."

ATSB response status: CLOSED-ACCEPTED.

General details
Date: 15 February 2001   Investigation status: Completed  
Time: 0830 hours ESuT    
Location   (show map): 56 km SW Sydney, Aero.    
State: New South Wales   Occurrence type: Flight control systems  
Release date: 02 October 2001   Occurrence category: Incident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer The Boeing Company  
Aircraft model 737  
Aircraft registration VH-CZX  
Serial number 24029  
Type of operation Air Transport High Capacity  
Damage to aircraft Nil  
Departure point Adelaide, SA  
Departure time 0630 hours ESuT  
Destination Sydney, NSW  
Last update 13 May 2014