ISO 1151-11:2023

INTERNATIONAL ISO
STANDARD 1151-11
First edition
2023-12
Flight dynamics — Vocabulary —
Part 11:
Control system
Reference number
© ISO 2023
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Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Basic concepts . 1
3.2 Basic elements . 3
3.3 Control system classification . . . 6
Index .10
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Foreword
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INTERNATIONAL STANDARD ISO 1151-11:2023(E)
Flight dynamics — Vocabulary —
Part 11:
Control system
1 Scope
This document establishes the terms and definitions of the basic concepts applied in science, engineering
and manufacturing in the field of flight control systems of aircraft (airplane and helicopter).
2 Normative references
There are no normative references in this document.
3 Terms and definitions
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1 Basic concepts
3.1.1
system
combination of components, parts, and elements that are interconnected to perform one or more
specific functions
3.1.2
control system
set of mechanical or electronic devices that manages, commands, directs or regulates the behaviour of
other devices or systems (3.1.1) by controlling the output
3.1.3
flight control system
complex of mechanical and electronic devices of aircraft (airplane and helicopter) providing its stability
and controllability to allow the pilot to control the movement and attitude of aircraft at all stages and
the modes of flight by changing the external forces or moments acting on aircraft
3.1.4
automatic flight control system
AFCS
type of flight control system (3.1.3) which provides aircraft control by measuring controlled variables
and comparing them with reference input to reach the goal defined over measured values in terms of
quality
Note 1 to entry: The AFCS is composed of several sub-systems that work together to provide automatic flight
control. The main components of the AFCS are the autothrottle system (3.3.9), flight director system (3.3.10),
autopilot system (3.3.11), flight management system (FMS) (3.3.12).
Note 2 to entry: The crew can select whether to put the aircraft under autopilot (3.3.9) or manual control mode.
Under the autopilot mode, the aircraft flight control surfaces (3.1.7) move automatically; under the manual control
mode, the pilot follows the displayed flight director (3.3.10) commands to achieve the desired status.
3.1.5
effector
control effector
external device that directly changes forces and/or moments acting on aircraft to control aircraft
position and attitude
3.1.6
inceptor
control inceptor
cockpit controller
cockpit device for enabling pilot input through direct linkage or a flight control system (3.1.3) or
computer to control effectors (3.1.5)
3.1.7
control surface
flight control surface
aerodynamic control surface
movable airfoil that provides reactive force when in motion relative to the surrounding air for guiding
or controlling an aircraft in flight
3.1.8
primary flight control surface
primary control
control surface (3.1.7) used as effector (3.1.5) providing force or moment for aircraft stability or
manoeuvring control
3.1.9
secondary flight control surface
secondary control
control surface (3.1.7) used to modify an aerodynamic characteristic of aircraft
3.1.10
actuator
device for producing motion of effector (3.1.5) and/or force acting on effector
3.1.11
sensor
physical device for detection of inceptor (3.1.6) positions, feedback measurements or scheduling
information
3.1.12
longitudinal control
control of airplane’s pitching about the lateral axis
3.1.13
lateral control
control of airplane’s rolling about the longitudinal axis
3.1.14
directional control
control of airplane’s yawing about the normal or vertical axis
3.1.15
control effectiveness
measure of the effect of utilizing a control effector (3.1.5), either moment, moment coefficient, or angular
acceleration produced for a given control surface (3.1.7) deflection
3.1.16
control power
aircraft angular acceleration per unit of control effector (3.1.5) deflection
3.1.17
authority
permissible maximum amplitude of a signal or physical parameter
3.1.18
control authority
aggregate effect of the effectiveness of all the control effector (3.1.5) in whatever combination
3.1.19
control sensitivity
magnitude of aircraft response to forces applied on the control inceptor (3.1.6) or control effector (3.1.5)
3.1.20
attitude control
control of the orientation of aircraft with respect to inertial frame of reference
3.1.21
trim system
part of a flight control system (3.1.3) that adjusts the aerodynamic forces on the primary flight control
surfaces (3.1.8) to maintain the aircraft at the set altitude without control input
3.2 Basic elements
3.2.1
aileron
primary flight control surface (3.1.8), movable airfoil at the trailing edge of an airplane wing used as
effector (3.1.5) to change rolling moments for lateral control (3.1.13) about the longitudinal axis of the
aircraft
3.2.2
elevator
primary flight control surface (3.1.8), movable (auxiliary) airfoil hinged to the rear of the left and right
horizontal stabilizer (3.2.17) of the aircraft tail used as effector (3.1.5) to change pitching moments for
longitudinal control (3.1.12) about the transversal axis of the aircraft
3.2.3
rudder
primary flight control surface (3.1.8), movable (auxiliary) airfoil hinged to the rear of the vertical
stabilizer (fin) of the aircraft tail used as effector (3.1.5) to change yawing moments for directional
control (3.1.14) about the normal axis of the aircraft
3.2.4
elevon
control surface (3.1.7) on an airplane that combines the functions of elevator (3.2.2) and aileron (3.2.1)
to control both roll and pitch attitudes
3.2.5
ruddervator
control surface (3.1.7), usually a on ‘V’ or 'butterfly' tail airplane, that combines the functions of elevator
(3.2.2) and rudder (3.2.3) to control both yaw and pitch attitudes
3.2.6
canard
horizontal control surface (3.1.7) mounted ahead of the wing to provide longitudinal stability and
control and to control pitch attitude
3.2.7
flap
secondary control (3.1.9), movable airfoil usually attached to the trailing edge of a wing on an airplane
that changes its camber to increase both its lift and its drag
3.2.8
leading-edge flap
secondary control (3.1.9), movable element of an airplane wing attached near its leading edge that
changes its camber to increase both its lift and its drag
3.2.9
slat
secondary control (3.1.9), movable element of an airplane wing attached near its leading edge that
produces a slot aft of the leading edge in order to allow air from below the wing to pass through and
maintain laminar flow at high angle-of-attack
3.2.10
spoiler
uncambered control surface (3.1.7) deflected symmetrically upward above the aft surface of the wing
for reducing the wing lift during landing and for increasing drag to act as speed brakes (3.2.11) or
deflected on one side only to act as aileron (3.2.1) for roll control
3.2.11
speed brake
uncambered control surface (3.1.7) deflected symmetrically upward above the aft surface of the wing
for increasing drag to reduce aircraft speed during final approach to touchdown
3.2.12
stabilator
stabilizer elevator
airplane control surface (3.1.7) that combines the functions of an elevator (3.2.2) and a horizontal
stabilizer (3.2.17)
3.2.13
balance tab
auxiliary hinged airfoil on the trailing edge of the aircraft control surface (3.1.7) used to balance, either
fully or partially, the aerodynamic loads on the control surface, thus reducing stick loads
3.2.14
servo tab
Flettner tab
auxiliary hinged airfoil (movable surface) on the trailing edge of the aircraft control surface (3.1.7) to
assist the movement of the control surface
Note 1 to entry: A servo tab is integrated into the flight control's operating components in such a way as to drive,
or help to drive, the control surface during normal control inputs.
Note 2 to entry: The pilot controls the tab not the control surface. The movement of the tab makes the control
surface move.
3.2.15
anti-servo tab
anti-balance tab
movable surface on the trailing edge of the stabilator (3.2.12) providing force acting against the
movement of the stabilator to reduce the sensitivity to pilot input
3.2.16
drag-rudder
split drag rudder
control device for directional control (3.1.14) on tailless or flying wing type airplane designed as
assembly of two flaps (3.2.7) mounted together on each wing
Note 1 to entry: Deflection of drag-rudder means that both flaps are symmetrically deflected at a certain angle in
opposite directions.
3.2.17
horizontal stabilizer
tailplane
horizontal surface, fixed or adjustable, of an aircraft empennage, to provide angular stability for
rotations about the lateral axis
3.2.18
trimmable horizontal stabilizer
adjustable horizontal stabilizer
fully moving horizontal tail surface, not in response to inceptor (3.1.6) movement but in response to the
trim system (3.1.21) settings depending on flight mode
3.2.19
taileron
left and right tailplanes (3.2.17) used as primary flight control surfaces (3.1.8) in both pitch and roll
3.2.20
main rotor collective control
changing the pitch of all the main rotor blades by the same amount (or
collectively) with re
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