During climb-out from Darwin, passengers on the British Aerospace Bae146 advised the cabin manager that about 3 metres of cable was trailing from the trailing edge of the right wing. After the first officer had conducted a visual inspection, the crew advised Darwin ATC that they had a problem and required a return for landing. Fuel was burnt-off to achieve maximum landing weight. Controllability checks found no handling problems with the aircraft, which was landed safely.
An inspection identified the trailing cable as an aileron trim cable (upper). Failure of the cable had occurred at the outboard pulley located at wing rib 14. The cable was found to have failed as a result of significant corrosion between the pulley bank and the wing rear spar. Corrosion was also present on the failed cable coinciding with the location of the inboard pulley at wing rib 14. No corrosion was found on the left-wing aileron trim cables. Previous inspection of the area was reportedly carried out during a 6C check in May 1999, 3,495 flight hours earlier.
The aileron trim cable material was zinc coated carbon steel (MIL-W-83420, Type 1, Composition A). Stainless steel trim cables were not available from the aircraft manufacturer.
No other reported failures of BAe146 aileron trim cables were found in a search of the Civil Aviation Safety Authority major defect and ATSB incident databases. The operator advised that corroded cables and seized pulleys at that location had been recorded on various BAe146 aircraft since 1992. The aircraft maintenance manual required special attention for corrosion during inspection of cable sections in contact with pulleys.
The operator replaced both right wing aileron trim cables and
chains on the aircraft. As a result of this incident the operator
carried out an aileron trim cable inspection of its fleet of twelve
BAe146 aircraft. Notable corrosion in the rib 14 pulley area was
found in both wings of another aircraft. All aileron trim (wing
loop) cables of that aircraft were subsequently replaced.
On 27 July 2000 the operator issued an Engineering Release (ER) that required a more thorough inspection of aileron trim cables for corrosion at each C check. The inspection aimed to ensure that any hidden corrosion at pulley locations did not pass through major checks undetected. Inspection highlighted the need to operate flight controls over their complete range of movement allowing inspection of cable obscured by pulleys. The ER also called for cleaning and lubrication of cables, paying particular attention to the lengths of cable passing through the pulley bank.
|Date:||22 June 2000||Investigation status:||Completed|
|Time:||0730 hours CST|
|Location:||28 km E Darwin, Aero.|
|State:||Northern Territory||Occurrence type:||Flight control systems|
|Release date:||25 May 2001||Occurrence class:||Technical|
|Report status:||Final||Occurrence category:||Incident|
|Highest injury level:||None|
|Aircraft manufacturer||British Aerospace PLC|
|Aircraft model||BAe 146|
|Type of operation||Air Transport High Capacity|
|Damage to aircraft||Minor|
|Departure point||Darwin, NT|
|Departure time||0712 CST|