Aerodynamic  Factors Chapter4 Introduction Several factors affect aircraft performance including the  atmosphere, aerodynamics, and aircraft icing. Pilots need an  understanding of these factors for a sound basis for prediction  of aircraft response to control inputs, especially with regard  to instrument approaches, while holding, and when operating  at reduced airspeed in instrument meteorological conditions  (IMC). Although these factors are important to the pilot flying  visual flight rules (VFR), they must be even more thoroughly  understood by the pilot operating under instrument flight  rules (IFR). Instrument pilots rely strictly on instrument  indications to precisely control the aircraft; therefore, they  must have a solid understanding of basic aerodynamic  principles in order to make accurate judgments regarding  aircraft control inputs. 