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Landing gear failure leads to runway excursion

A runway excursion involving a Fairchild Industries Metro 23 aircraft shows why it’s important that maintenance and inspection programs adequately provide for the detection of corrosion and cracking.

Fairchild Industries Metro 23 aircraft after runway excursion at Portland, Vic

On 20 February 2014, the aircraft was being operated on a charter flight from Avalon to Portland, Victoria with 10 passengers and two crew on board.

Shortly after touch-down, the torque link on the left, main landing gear (MLG) failed. This resulted in the aircraft veering left and coming to rest beside the runway. Fortunately no one was injured.

The runway excursion resulted from failure of the lower torque link attachment lug on the left main landing gear’s yoke. This allowed the wheels to rotate through 90 degrees, producing a large braking effect on the left side.

The flight crew were unable to counteract this and the aircraft veered to the left and off the runway.

The failure of the lug on the yoke resulted from pre-existing cracks that had progressively grown until the part had insufficient strength to support normal landing loads.

The cracks initiated principally from areas of pitting corrosion in the lug’s bore and were propagated by cyclic stresses imposed during operation.

The ATSB found the maintenance and inspection program for the aircraft’s landing gear did not adequately provide for the detection of corrosion and cracking in the yoke lug bore.

This occurrence highlights the importance of developing and conducting appropriately detailed maintenance inspections on susceptible parts and assemblies.

The Civil Aviation Safety Authority (CASA) has released Airworthiness Bulletin AWB 32-023 to alert all Fairchild Swearingen Metro and Merlin operators of the need for detailed inspection of the internal bore of the landing gear torque link lugs for any signs of corrosion or wear outside of the manufacturer’s specified limits and to take appropriate action per the aircraft’s structural repair manual, where necessary.

In addition, the aircraft’s Type Certificate Holder has drafted service bulletins 226-32-083, 227-32-065, CC7-32-030 titled “inspection of Main Landing Yoke for Corrosion and/or Damage” that will significantly increase the effectiveness of maintenance inspections for the affected parts.

This occurrence highlights the importance of developing and conducting appropriately detailed maintenance inspections on susceptible parts and assemblies.

Read the ATSB investigation report AO-2014-028

 
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Last update 20 October 2016