The aerodynamic design of the Sukhoi S-54 was based on the Su-27 to make the trainer’s flight performance close to that of production combat aircraft such as the Su-27 and the MiG-29. Unstable aerodynamics improved its maneuverability and decreased its structural weight. The designers considered alternate single-engined and twin-engined trainer configurations. Preference was given to the single-engined design.
Sukhoi S-54 has a conventional aerodynamic arrangement with a twin-fin vertical stabilizer and a low-set horizontal stabilizer attached to the tail booms. Dorsal fins are the same as those seen on the Su-27. High-lift devices on the thin, low-aspect-ratio wing include rotary leading edge flaps and trailing edge flaps.
The fuselage and wing are integrated like those of the Su-27. The original design, incorporating rectangular, ventral air intakes had horizontal flow control panels. A boundary layer air bleed wedge was placed between the air intake and the lower fuselage. Newer S-54 designs have a bifurcated intake design.
Similar to the Su-27, the instructor’s seat is above that of the cadet. The forward fuselage and the radome have an elliptical cross section, with the long axis in the horizontal plane, to improve the aircraft’s directional stability and to reduce the fuselage side surface area ahead of the center of gravity. The instructor’s and student’s cockpits have a common canopy like the Su-27.
The aircraft has tricycle landing gear with a nose gear strut that retracts (in the original design) into a well under the air duct. In the extended position, the nose wheel is behind the air inlet, decreasing the probability of foreign object ingestion during taxiing, takeoff and landing. The Sukhoi S-54′s structural arrangement is similar to the Su-27.