Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Bell Textron Canada Limited (Bell) Model 427 helicopters. This proposed AD was prompted by a report of a cracked transmission oil check valve (check valve). This proposed AD would require inspecting and measuring certain check valves and, depending on the results, repetitively inspecting and removing the check valve from service if it has leaks or is cracked. This proposed AD would also prohibit installing the affected check valves on any helicopter. The FAA is proposing this AD to address the unsafe condition on these products.