Canadian regulators have ordered operators of certain Bell 429 helicopters to perform urgent tail rotor blade inspections after defects were found in the manufacturing process.
In an emergency airworthiness directive, Transport Canada says the airframer has recently received “several reports” of cracks found in the tail rotor abrasion strip.
“Upon investigation, it was determined that a crucial step in the fabrication of the abrasion strip was missed by one of the suppliers which could result in the presence of stress risers leading to fatigue cracking of the part,” says the directive.
It warns that cracking of the abrasion strip could lead to failure of the tail rotor blade and potentially “catastrophic consequences”, including the destruction of the tail rotor gearbox.
Prior to the next flight, 429 operators of helicopters with certain specified tail rotor assemblies installed should carry out a visual inspection of the abrasion strip for “chordwise cracks”, replacing the blades if required.
If no cracks are found, the blade should nonetheless be marked, says Transport Canada, and repetitive checks and inspections conducted.
Bell builds the 429 at its facility in Mirabel, Canada.
