Operators of stretched Bombardier CRJs must inspect engine pylon fasteners after several reports of problems prompted the manufacturer to issue new maintenance instructions mandated by authorities. In the U.S. the FAA bypassed its usual process of issuing a draft, suggesting the problem is more urgent than a routine fix.
The FAA order came on May 26—just one month after Transport Canada published the original AD. Models affected are the CL-600-2C10/CRJ-700, -701 and -702; CL-600-2D15/CRJ-705; CL-600-2D24/CRJ-900; and CL-600-2E25/CRJ-1000. The FAA calculates that 531 U.S.-registered aircraft are affected. Aviation Week’s Commercial Fleet Discovery database shows a total of 773 in the global fleet.
“There have been several reported findings of loose or missing Hi-Lite fasteners on the left-hand (LH) and right-hand (RH) upper and lower engine pylon structure common to the upper and lower pylon skin panels and engine thrust fitting,” the FAA says in its directive, using Transport Canada’s original language verbatim. “Missing fasteners in these areas are shown to significantly reduce the safety margins and could result in a structural failure of the engine pylon.”
The European Aviation Safety Agency adopted Transport Canada’s directive on the same day the Canadian version was issued, but such moves are common and not necessarily indicative of an issue’s severity.
Bombardier first alerted operators of the problem in late 2015, triggering some to perform initial inspections. In early March 2016 the OEM released a new maintenance manual task detailing the inspection procedure as well as repair guidance for addressing findings. The ADs mandate both the initial check and repetitive inspections. Aircraft with more than 840 in-service hours must conduct initial checks within 660 hr., while those with 840 or fewer hours must do the checks before 1,500 total hours.
The AD does not make clear whether the issue is tied to non-compliant fasteners, production-line problems or another root cause. It also does not explain how the issue came to light.
Bombardier did not respond to queries about the directive.