Which statement describes an Inertial Navigation System (INS)?

• A. A computer-based navigation system that tracks movement via onboard accelerometers; initial location entered; does not require outside signals.
• B. A system that relies on GPS satellites.
• C. A ground-based radio navigation system.
• D. An autopilot component.

Answer: (A)

An Inertial Navigation System determines position by using the aircraft’s own motion data from onboard sensors, rather than signals from outside. It relies on accelerometers (and angular rate sensors) to measure how the aircraft accelerates and turns; those measurements are integrated over time to compute velocity and then position. Because you start the process with an initial position and velocity that you enter, the system can navigate without any external navigation aids. That ability to function independently of external signals is what sets an INS apart.

Inertial navigation is often paired with other systems to keep error drift in check, since tiny sensor biases accumulate over time. This is why you’ll sometimes see INS fused with GPS for improved accuracy.

The other options don’t describe an INS: one relies on GPS satellites, another on ground-based radio beacons, and another refers to flight control rather than navigation.