A small gap between flap sections can be a source of additional aerodynamic losses for an aircraft. Yakovlev's developers proposed a mechanism that automatically closes this gap immediately after the flap is retracted.

Its main feature is the movable end of the root section of the flap. When the flap is retracted and its sections separate, two springs extend the profiled part and press it against the adjacent section. As a result, the formed gap closes.

When the flap is extended, the mechanism works in reverse. The sections move closer and press on the movable end, forcing it to move inside the root part. For precise movement, the developers provided two two-link hinge assemblies and a longitudinal rod that prevents longitudinal displacement and skewing of the structure.

Additional fluoroplastic elements should reduce friction during parts movement, and rubber seals should prevent air flow through the connection and protect the mechanism from moisture and dust.