Comment from David Loftus

Subject: Public Comment on Notice of Proposed Rulemaking (NPRM) for Diamond Aircraft Industries Inc. Model DA 40, DA 40 F, and DA 40 NG Airplanes (Passenger Door Latching Mechanism)I am writing to advocate for a targeted modification to the applicability scope of the proposed Airworthiness Directive. While mitigating the risk of in-flight passenger door separations is a valid safety objective, a blanket mandate across the entire Model DA 40, DA 40 F, and DA 40 NG fleet ignores critical, factory-installed type design evolutions.The mechanical root cause of historic door separation events stems primarily from early-generation locking architectures. Recognizing this vulnerability, Diamond Aircraft structurally revised the production line, implementing a robust, dual-stage secondary safety latch mechanism as a standard factory feature on later-model airframes, including the DA 40 XLS series.On factory-equipped secondary safety latch aircraft, the mechanical redundancy completely eliminates the risk of an un-commanded door release, even if the primary latches experience minor wear or misalignment. Forcing late-model fleet operators to apply redundant cabin placards, disrupt active flight operations, and absorb repetitive 100-hour inspection costs provides zero measurable net safety margin.The FAA should consider historical precedents for component-specific risk mitigation. Narrowing the final rule's applicability exclusively to legacy serial numbers manufactured prior to the integration of the standard factory secondary safety latch is recommended. Applying the directive solely to unmodified legacy hulls preserves the intended safety outcome while preventing an unjustified administrative and financial burden on operators of modern airframes already equipped with the safety mechanism.To submit such a justification, the official Federal Register Docket number or the Regulations.gov public comment portal can be used to provide formal feedback during the open comment period for the NPRM.