The maintenance program for the aircraft’s landing gear did not adequately provide for the detection of corrosion and cracking in the yoke lug bore.
The actions taken by both CASA and M7 Aerospace should facilitate the early identification of corrosion and cracking in the yoke lug bore.
M7 Aerospace has drafted service bulletins SB 226-32-083, 227-32-065, CC7-32-030 entitled “Inspection of Main Landing Gear Yoke for Corrosion and/or Damage”for all operators of SA226-and 227 aeroplanes with M7/Fairchild Main Landing Gear Yoke and Torque Link Shaft installed. The SB will require disassembly of the components and detailed visual inspection, liquid penetrant inspection, magnetic particle inspection and high-frequency eddy current inspections for cracks or corrosion on and inside the torque link lug and shaft of the MLG yoke.
This action requires appropriately detailed inspections to be conducted in the affected areas of the landing gear yoke and shaft and will adequately address the safety issue (once released).
The operator indicated that they had inspected all in-service landing gear assemblies for damage, and had replaced the lower yokes on all MLG fitted to their Metro 23s. Both the operator’s current Metro IIIs had new gears installed in 2012 and 2013, as part of an upgrade to the aircraft. The operator also advised that they were in the process of writing a new gear maintenance program for all their landing gears to increase vigilance in areas of the torque links, which will include removal of the pins at each Phase 3 inspection/overhaul.
This action requires appropriately detailed inspections to be conducted in the affected areas of the landing gear yoke and shaft and will adequately address the safety issue (once implemented).
The Civil Aviation Safety Authority (CASA) 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.
This action appropriately highlights the need for conducting detailed inspections in the affected areas of the landing gear yoke and shaft.
