ISO 1151-2:1985

Overview

ISO 1151-2:1985 is part of the ISO 1151 flight dynamics series and defines fundamental concepts, quantities and symbols for the motions of the aircraft and the atmosphere relative to the Earth. This second edition (1985) provides standardized terminology and coordinate conventions used to describe aircraft kinematics when the atmosphere is assumed either at rest or in uniform translational motion relative to the Earth. The standard assumes a rigid aircraft (though most definitions apply to flexible vehicles) and establishes consistent symbols, axis systems and sign conventions for flight dynamics work.

Key topics

• Coordinate and axis systems
  • Definition of kinematic triads (aircraft, kinematic, and normal terrestrial triads) and guidance on selecting a reference plane.
  • Right-handed, orthogonal triads and sign conventions for positive rotations.
• Velocity vectors and components
  • Definition of the velocity-of-the-aircraft relative to the Earth (velocity-Terre / ground-velocity) and its components in different triads (e.g., u, v, w).
  • Definition of the wind vector (air motion relative to Earth), its magnitude and components.
• Flight path and wind angles
  • Azimuth (heading/route) and pente (flight path slope) of the velocity-Terre vector relative to the terrestrial triad.
  • Azimuth and slope of the wind vector, including sign conventions (e.g., positive ascent for upward wind).
• Notation and conventions
  • Standard symbols, naming rules and numerical indexing used throughout ISO 1151.
  • Rules for local vertical variations and definition qualifiers when needed.

Applications

ISO 1151-2:1985 is used where unambiguous, standard definitions of motion and angles are required:

• Flight dynamics analysis and mathematical modelling
• Aircraft design (aerodynamics, stability and control)
• Flight simulation, avionics and navigation system development
• Flight test data reduction and instrumentation interpretation
• Interface between meteorology (wind modelling) and aircraft performance studies
• Regulatory and standards documentation where consistent symbols and sign conventions are required

Who uses this standard

• Aerospace engineers (flight dynamics, aerodynamics, controls)
• Flight test engineers and simulation developers
• Avionics and navigation system designers
• Researchers and educators in aerospace mechanics
• Standards bodies and certification authorities referencing consistent terminology

Related standards

• ISO 1151 series (Parts 1–7) - other parts cover aircraft motion relative to air, derivatives of forces/moments, stability parameters, measurement quantities, geometry and flight domains.
• Prepared by ISO/TC 20 (Aeronautics and Space)

Keywords: ISO 1151-2:1985, flight dynamics standard, motions of the aircraft, atmosphere relative to the Earth, axis system, velocities, flight path angles, wind direction angles.