Final answer:
The airplane's aerodynamic balance and controllability are primarily governed by its center of gravity and control surfaces, with the shape of the wings also playing a critical role in creating lift. Contour feathers help reduce drag in birds.
Step-by-step explanation:
An airplane's aerodynamic balance and controllability are governed by the center of gravity and control surfaces. These aspects are crucial for the effective control of an aircraft's pitch, roll, and yaw movements. The shape of the wings and their tilt, as described by Bernoulli's principle, also play a significant role in creating lift, allowing the plane to sustain flight. The development of reliable engines and electronic instrumentation, along with advances in construction materials, has further enhanced the aerodynamics and control systems in modern airplanes.
Answering the student's question, among the four types of feathers mentioned, the contour feathers help to reduce drag caused by wind resistance during flight. These feathers streamline a bird's shape and allow for smooth airflow over the body, thus minimizing turbulence and drag.