RuAviation

As part of the import substitution program for the MC-21 aircraft, engineers are revising several wing and airframe design solutions and transitioning to domestically produced materials and systems. The effort targets reduced reliance on foreign suppliers and refinement of airframe aerodynamic performance, according to United Aircraft Corporation (UAC).

On April 6, 2026, the Russian Federal Service for Intellectual Property (Rospatent) granted Yakovlev PJSC a utility model patent covering an improved flap design for the MC-21-310. The modification reduces aerodynamic losses in cruise.

In the MC-21 wing, the inboard and outboard flaps converge at maximum deflection. In cruise, a structural gap forms at the interface between the flap sections. Air leaks through this gap from the lower to the upper wing surface. This leakage reduces local lift along the trailing edge.

On earlier MC-21-300 aircraft, engineers used an imported elastomeric seal at the flap section ends to mitigate this effect. Flight tests showed that the seal deforms under airflow and degrades local flow quality.

Yakovlev Engineering Center developed a movable flap tip element. It operates through the mechanism’s kinematics and requires no additional actuators. In the retracted configuration, the element closes the gap between flap sections, reducing leakage and associated vortex formation. During extension, it automatically moves clear of the interaction zone, preserving flap kinematics and avoiding additional drag or mechanism loads.

The new design is manufactured at the Kazan site of AeroComposit JSC (a Russian composite structures supplier). Tests are being conducted on an import-substituted MC-21-310 prototype, tail number 73057 (MS.0013).