Airworthiness Directives; MD Helicopters, LLC Helicopters
Key claim: Operators of certain MD Helicopters 369 and 500N models must do a one-time visual inspection of the main transmission drive shaft coupling for spline cracks and replace the coupling if cracks are found.
Abstract
(Rule · Transportation Department, Federal Aviation Administration) The FAA is adopting a new airworthiness directive (AD) for certain MD Helicopters, LLC (MDHI) Model 369D, 369E, 369F, 369FF, 369H, and 500N helicopters. This AD was prompted by a report of mechanical damage to the main transmission drive shaft coupling (coupling). This AD requires a one-time visual inspection of the couplings for cracks of the splines and, depending on the results, replacement of the couplings. The FAA is issuing this AD to address the unsafe condition on these products.
Why this matters
MD 369 and 500N series helicopters are widely used in law enforcement, utility, and tour operations, where a cracked main transmission drive shaft coupling could lead to loss of drive to the main rotor. Mandating a one-time spline inspection and replacement when defects are found is a narrow but safety-critical maintenance action for affected operators.