Overview
ISO 1151-4:1994 - Flight dynamics: Concepts, quantities and symbols - Part 4 defines the standardized terminology, quantities and symbols used in the study of aircraft stability and control. This second edition (1994) cancels and replaces the first edition (1974) and addendum 1 (1986). It provides consistent definitions, sign conventions and reference axis systems used in theoretical, experimental and practical work on flight dynamics.
Key topics
- Controls and control inputs: standardized definitions for pitch, roll and yaw controls (stick/wheel, pedals) and helicopter collective (lift control). Includes control displacements, pilot efforts and trim control concepts.
- Reference frames and sign conventions: three-dimensional, orthogonal, right‑handed axis systems; center of gravity/centre of mass conventions and specification of aircraft reference plane.
- Stability parameters: concepts used for simplified stability studies (longitudinal and lateral), including assumptions about independent variables and fixed/free control surfaces.
- Aerodynamic centres and centre of pressure: definitions for aerodynamic centres referenced to angle of attack, sideslip and control deflections; point and coordinate definitions for the centre of pressure.
- Static margins and stability criteria: descriptors for static margin (motors free/fixed), longitudinal static stability and the relationship between aerodynamic centre location and centre of mass.
- Quantities for aircraft behaviour evaluation: practical metrics such as manoeuvring displacement, control gradients, load factor relationships and other quantities used in plotting and assessing behaviour.
Practical applications
ISO 1151-4:1994 is used to:
- Harmonize terminology and symbols in design documentation, flight manuals and research papers.
- Support flight dynamics modeling, simulation and control-law development by providing consistent variable and sign conventions.
- Guide flight-test engineers in data reporting and analysis for stability and control testing.
- Assist certification authorities and technical reviewers in interpreting aerodynamics and stability data.
- Serve educators and researchers as a reference for standard definitions in aeronautics courses and publications.
Typical users: aerospace/flight dynamics engineers, flight-test teams, control-systems designers, regulators, researchers, technical writers and educators focused on aircraft stability and control.
Related standards
ISO 1151 is a multipart series on flight dynamics - Concepts, quantities and symbols. Related Parts include:
- Part 1: Aircraft motion relative to the air
- Part 2: Motions of aircraft and atmosphere relative to Earth
- Part 3: Derivatives of forces, moments and coefficients
- Part 5: Quantities used in measurements
- Part 6: Aircraft geometry
- Part 7: Flight points and flight envelopes
- Part 8/9: Dynamic behaviour concepts and atmospheric motion models
Keywords: ISO 1151-4:1994, flight dynamics, aircraft stability, aircraft control, aerodynamic centre, static margin, centre of pressure, manoeuvring displacement, flight-test, control deflection, symbols.
Open preview (PDF)Flight dynamics — Concepts, quantities, and symbols — Part 4: Concepts and quantities used in the study of aircraft stability and control
