Blind-Flying Demands on Stability and Control
Blind flying is controlled flight without reference to the outside scene, more specifically, the horizon. Simply put, there is no way that an airplane can be made suitable for blind flight by aerodynamic design alone. A pilot must rely on some form of gyroscopic device to retain control, either as a panel instrument or as part of an automatic pilot.
The need for instrumentation comes from the effects of spiral instability, or aileron control friction on airplanes that are spirally stable, as discussed in Sec. 5. Even if strong spiral stability were to be built into a design, at the expense of other desirable flying qualities, a pilot could lose control over altitude unless trained to damp the phugoid mode (Chapter 18, Sec. 9) by reference to airspeed alone.
Spatial disorientation due to illusions can be prevented by reference to instruments. The FAA’s Aeronautical Information Manual (1999) lists no fewer than 14 flight illusions that have been identified, such as a Coriolis, graveyard spin, somatogravic, and inversion illusions.