Summary
We propose to supersede airworthiness directive (AD) 2014-16- 01 for MD Helicopters, Inc. (MDHI) Model MD900 helicopters. AD 2014-16- 01 requires an eddy current inspection of the main rotor upper hub assembly (upper hub) for a crack. Since we issued AD 2014-16-01, three additional upper hub cracks were reported. This proposed AD would require additional inspections and replacing the fillet seal. These proposed actions are intended to prevent an unsafe condition on these products.