ABSTRACT
Lift, drag, thrust, and weight are the four fundamental forces on an aircraft in general. The lift and drag are determined by the aerodynamic features of the aircraft. Aerofoils produce “lift” when airflow passes them. This chapter focuses on lift coefficient and drag coefficient. The airflow discussed is subsonic. The design of the physical appearance of aircraft affects the lift and drag coefficients. The chapter also discusses the relationship between the coefficients and the features of aerofoil and the shapes of aircraft. If airflow is subsonic and air can be treated as incompressible, air speed and pressure around the aerofoil can be analyzed by Bernoulli’s equation. Assuming it is level flow, because the elevation difference between the free-stream and over the aerofoil is negligible comparing the size of the aircraft. The aspect ratio of small subsonic aircraft can be approximately 5 or 6, and the aspect ratio of a jet fighter could be as low as 2 to 3.5.
