Summary
The FAA proposes to adopt a new airworthiness directive (AD) for all Columbia Helicopters, Inc. Model 234 helicopters and all Restricted Category Model CH-47D helicopters. This proposed AD was prompted by reports of corrosion detected on certain flight control rigid connecting links (connecting link). This proposed AD would require repetitive borescope inspections of the connecting links for corrosion and, depending on the results of the inspection, repair of the corrosion or replacement of the connecting link with a serviceable part. This proposed AD would also require reporting the results of these inspections and would prohibit installing a certain part-numbered connecting link or a connecting link with an unknown part number on a helicopter unless certain requirements are met. The FAA is proposing this AD to address the unsafe condition on these products.