FAA Proposes Airworthiness Directive for Diamond DA50 C Over Flap Actuator Failures

The FAA has proposed an airworthiness directive (AD) that would apply to all Diamond DA 50 C aircraft, regardless of category. It addresses a condition that could prevent pilots from extending the flaps and potentially limit aileron travel. The FAA said investigations found that a failed flap actuator could interfere with the aileron control system, and one reported occurrence resulted in reduced aileron control. The agency said the condition, if left uncorrected, could reduce the pilot's ability to control the airplane.

The proposal follows European Union Aviation Safety Agency (EASA) AD 2026-0140, issued July 15, 2026, which addressed the same issue. Under the proposed directive, operators would have to inspect the flap actuator for displacement of the black slide grommet and check that the rod end bearing is properly secured. The actuator would also have to be modified, followed by recurring inspections of the torque seal on the jam nuts at the rod end bearing attachment.

The proposed compliance times are: an initial inspection within 50 hours time-in-service or 12 months after the AD's effective date, whichever comes first; the actuator modification within 100 hours or 12 months; and, after modification, repetitive inspections at intervals of no more than 200 hours or 12 months, whichever comes first. If an inspection reveals a discrepancy, corrective action would be required before the airplane's next flight. The proposal would also prohibit installing unmodified flap actuators on affected aircraft.

The FAA estimates the directive would affect 30 airplanes on the U.S. registry. It projects an initial inspection cost of $85 per aircraft and modification costs of up to $2,675 per aircraft, including parts. The agency is accepting public comments on the proposal through Dec. 28, 2026.

Airworthiness directives on a type often arrive in sequence: a European authority acts first, and the U.S. regulator follows with its own proposal for aircraft on its registry. Here the EASA directive of July 15, 2026 came ahead of the FAA proposal, and the compliance steps described are an inspection, a hardware modification and a recurring torque-seal check.

The FAA is treating the proposal as an interim action while the manufacturer continues investigating the issue, and additional rulemaking could follow depending on the investigation's findings. For a small U.S. fleet of 30 airplanes, the stated per-aircraft costs of $85 for inspection and up to $2,675 for modification are modest, but the recurring inspection interval means the obligation does not end with the modification.

The next dated milestone is the close of public comments on Dec. 28, 2026. The manufacturer's investigation findings are the other open item, since the FAA has tied any further rulemaking to them.