Transport Canada issued an emergency airworthiness directive (AD), requiring operators of specific Canadair Challenger 600, 601, 601-3A/3R aircraft to inspect inboard flap fasteners.
According to the AD, there have been three in-service reports on Challenger 604 Variant aircraft of a fractured fastener head on the inboard flap hinge-box forward fitting at Wing Station (WS) 76.50, which were found during a routine maintenance inspection.
Investigation revealed that the installation of these fasteners on the inboard flap hinge-box forward fittings at WS 76.50 and WS 127.25, on both wings, does not conform to the engineering drawings. Incorrect installation may result in premature failure of the fasteners attaching the inboard flap hinge-box forward fitting. Failure of the fasteners could lead to the detachment of the flap hinge box and consequently the detachment of the flap surface. The loss of a flap surface could adversely affect the continued safe operation of the airplane.
On August 15, 2014, an AD had been issued, mandating a detailed visual inspection (DVI) of each inboard flap hinge-box forward fitting, on both wings, and rectification as required. Incorrectly oriented fasteners require repetitive inspections until the terminating action is accomplished.
After the issuance of the original AD, there has been one reported incident on a Challenger 604 where four fasteners were found fractured on the same flap hingebox forward fitting. The investigation determined that the fasteners were incorrectly installed. Although there have been no reported fractured fastener heads found to date on any model Challenger 600, 601, 601-3A/3R aircraft , incorrectly oriented fasteners were found on some of these models.
The AD requires repeated inspections until the fasteners have been replaced.
- EAD CF-2013-39R2 (PDF)