TS ISO 1151-2

TS ISO 1151-2 is a terminology standard for the concepts, quantities and symbols used to describe the motion of an aircraft and the atmosphere relative to the Earth. It provides a common technical language for axis systems, velocities, flight path angles and wind direction angles, all of which are fundamental to flight dynamics and aircraft motion analysis.

Reference frames used in flight motion

The standard is built around Earth-referenced motion. Under the stated assumptions, the atmosphere is either at rest or moving in translational motion at constant velocity relative to the Earth, and the aircraft is assumed to be rigid. This framework allows the relative motion between aircraft and atmosphere to be described consistently across calculations, measurements and technical communication.

In general flight-dynamics practice, the same physical motion may be expressed through different coordinate systems, such as Earth axes, aircraft axes and wind-related axes. Distinguishing these systems is essential because velocity components, orientation angles and wind directions have different meanings depending on the reference frame being used.

Why the shared terminology matters

A controlled vocabulary for axes, velocities and angles reduces ambiguity in performance analysis, guidance, stability studies and data reporting. The rigid-aircraft assumption supports clear definitions, while the standard also notes that most of the terminology can be applied to flexible aircraft with suitable interpretation.

• Basic definitions for motion relative to the Earth
• Axis-system terminology for aircraft and atmosphere
• Shared symbols for velocities, flight path angles and wind direction angles
• A terminology framework mainly intended for consistent technical use