This paper presents developing a suboptimal design of an autopilot system, using singular perturbation approach, to
replace a classical system existing in some Russian (MIG-21) aircrafts. The existing conventional design is discussed. Study of system dynamics leads to two-time scale simplified piece-wise linear model. Applying singular perturbation algorithm to the obtained model; a new suboptimal controller was developed. Numerical simulation is used to compare between the performances of the existing design, and that of the proposed suboptimal design. The proposed design shows better response than the existing one, especially in pitch attitude. The suboptimal controller can be implemented using modern digital electronics, which might help to save larger room in the (1IG-21) aircraft for other running modifications. The digital controller would also ensure higher reliability and better accuracy.