The small-span extra support wing (5) can be displaced over the fuselage (2) via rollers under a U-shaped rail in controlled manner w.r.t. the centre of gravity of the aircraft. The extra wing may have grooves (6) on its underside and may have extending flaps. The lower support wing (4), is usually of wider span than the top wing. It has at its tips downwards pointing end plates (4a), or stabilisers. The whole assembly provides a biplane aircraft with improved reliability and low takeoff and landing speeds.
