Glossary of Terms

A-B

Accident (aircraft):

an unintended event that causes death, injury, environmental or material damage

Active control technology:

the use of feedback control to enhance the performance or controllability and handling of a vehicle

Actuator:

physical device for producing motion and/or force

Adaptive control:

real-time parameter identification and controller update

Aerodynamic derivative:

partial derivative defining changes in vehicle force or moment due to changes in control or motion parameters

Air data system:

provides flight-condition and velocity vector information from external aircraft measurements

Airworthiness:

an all-embracing term to describe an aircraft's ability to fulfil its role safely

Aliasing:

phenomenon in digital systems in which input signal frequencies above half the sampling frequency appear at lower frequencies on the output signal, owing to the sampling process

Analogue (computer):

using electrical signals that are directly proportional (i.e. analogous) to a continuous physical parameter

Angle of attack (AoA):

the angle formed by the vector addition of the aircraft body-axis normal and longitudinal velocity components

Anti-aliasing filter:

function for reducing aliasing by restricting the band-width of the signal to be sampled - usually an analogue filter with a natural frequency set to less than half the sampling frequency

Authority limit:

permissible maximum amplitude of a signal or physical parameter

Autopilot:

outer-loop automatic control system for reducing pilot workload and/or augmenting weapon-system performance

Autostabiliser:

simple stability-augmentation system, usually to provide increased damping and often with limited authority

Averaging (rolling average):

digital process used to provide a smoothing and anti-aliasing function

Backlash:

a form of...