Definition
In the context of autopilots, digital systems are flight control systems that process sensor inputs and generate control outputs as discrete numerical values handled by a computer, rather than as continuously varying electrical signals. They use software-based logic to interpret aircraft attitude, heading, altitude, and navigation data, and then command the servos that move the flight controls.
Plain English
Autopilot systems whose 'brain' is a computer working with numbers rather than continuous electrical signals. The computer reads the aircraft's instruments, decides what corrections are needed, and tells the autopilot servos how to move the controls.
Context Anchor
Seen in discussions of modern autopilots, flight directors, displays, and other avionics that use computer processing instead of older purely mechanical or analog methods.
Derivation
Digital' comes from the Latin digitus, meaning 'finger,' which led to its use for individual numbers (the way fingers are used to count). A digital system therefore handles information as distinct numerical values, which fits how a computer processes data in steps rather than as a smooth, flowing signal.
Why Pilots Care
Digital autopilots are generally smoother, more accurate, and able to handle more complex tasks (such as coupled approaches and integration with GPS navigators) than older analog systems. Knowing the autopilot is digital also tells the pilot that its behavior is governed by software logic, which is why following the manufacturer's procedures and software version notes matters.
Analogy
A dimmer switch that smoothly changes a light is like an analog signal. A light control with numbered brightness steps is more like a digital system: it works in separate values.
Intuition Check
Digital does not just mean there is a screen in the cockpit. Here it means the system handles aircraft information as numbers and uses computer logic to act on it.
Example Sentence 1
The aircraft's digital autopilot system held altitude within a few feet, even in light turbulence.
Example Sentence 2
Transitioning from analog to digital systems in the cockpit improved the autopilot's ability to manage complex flight modes.