Aero.FixedWing Class

Namespace: Aero

Define fixed-wing aircraft

Description

An object of the Aero.FixedWing class defines a fixed-wing aircraft. Use this object to model and analyze a fixed-wing aircraft. It contains the static data for the aircraft, such as reference values, coefficients, and deflection angles.

To perform static analysis of fixed-wing aircraft, use this object in conjunction with the Aero.FixedWing.State object. The Aero.FixedWing.State object contains the aircraft information at a particular aircraft state.

For more information on fixed-wing aircraft definitions, see More About.

Class Attributes

Sealed

true

For information on class attributes, see Class Attributes.

Creation

Description

fixedWing = Aero.FixedWing creates a single Aero.FixedWing object with default property values.

fixedWing = Aero.FixedWing(N) creates an N-by-N matrix of Aero.FixedWing objects with default property values.

fixedWing = Aero.FixedWing(M,N,P,...) or Aero.FixedWing([M N P ...]) create an M-by-N-by-P-by-... array of Aero.FixedWing objects with default property values.

fixedWing = Aero.FixedWing(size(A)) creates an Aero.FixedWing object that is the same size as A and all Aero.FixedWing objects.

fixedWing = Aero.FixedWing(__,property,propertyValue) creates an array of Aero.FixedWing objects with property, propertyValue pairs applied to each of the Aero.FixedWing array objects. For a list of properties, see Properties.

Input Arguments

N — Number of fixed-wing objects

scalar

Number of fixed-wing objects, specified as a scalar.

M — Number of fixed-wing objects

scalar

Number of fixed-wing objects, specified as a scalar.

P — Number of fixed-wing objects

scalar

Number of fixed-wing objects, specified as a scalar.

A — Size of fixed-wing object

scalar

Size of fixed-wing object, specified as a scalar.

Properties

Public Properties

UnitSystem — Unit system

'Metric' (default) | 'English (kts)' | 'English (ft/s)' | scalar string | character vector

Unit system, specified as a scalar string or character vector.

Attributes:

GetAccess	public
SetAccess	public

Data Types: string | char

AngleSystem — Angle system

'Radians' (default) | 'Degrees'

Angle system, specified as 'Radians' or 'Degrees'.

Attributes:

GetAccess	public
SetAccess	public

Data Types: string | char

TemperatureSystem — Temperature system

'Kelvin' (default) | 'Celsius' | 'Rankine' | 'Fahrenheit'

Temperature system, specified as 'Kelvin', 'Celsius', 'Rankine', or 'Fahrenheit'.

Attributes:

GetAccess	public
SetAccess	public

Data Types: string | char

ReferenceArea — Reference area

0 (default) | scalar numeric

Reference area, specified as a scalar numeric, commonly denoted as 'S', in units of:

Units	UnitSystem
meters squared (m2)	'Metric'
feet squared (ft2)	'English (kts)' or 'English (ft/s)'

Attributes:

GetAccess	public
SetAccess	public

Data Types: double

ReferenceSpan — Reference span

0 (default) | scalar numeric

Reference span, specified as a scalar numeric, commonly denoted as 'b', in units of:

Units	UnitSystem
meters squared (m)	'Metric'
feet squared (ft)	'English (kts)' or 'English (ft/s)'

Attributes:

GetAccess	public
SetAccess	public

Data Types: double

ReferenceLength — Reference length

0 (default) | scalar numeric

Reference length, specified as a scalar numeric, commonly denoted as 'c', in units of:

Units	UnitSystem
meters squared (m)	'Metric'
feet squared (ft)	'English (kts)' or 'English (ft/s)'

Attributes:

GetAccess	public
SetAccess	public

Data Types: double

Coefficients — Aero.FixedWing.Coefficients class instance

scalar

Aero.FixedWing.Coefficients class instance, specified as a scalar that contains the coefficients defining the fixed-wing aircraft. This object ignores this property if no value is set.

Attributes:

GetAccess	public
SetAccess	public

Data Types: double

DegreesOfFreedom — Degrees of freedom

'6DOF' (default) | '3DOF' | 'PM4' | 'PM6'

Degrees of freedom, specified as a string or character vector.

Degrees of Freedom	Description
'6DOF'	Six degrees of freedom. Describes translational and rotational movement in 3-D space.
'3DOF'	Three degrees of freedom. Describes translational and rotational movement in 2-D space.
'PM4'	Fourth order point-mass. Describes translational movement in 2-D space.
'PM6'	Sixth order point-mass. Describes translational movement in 3-D space.

Attributes:

GetAccess	public
SetAccess	public

Data Types: string | char

Surfaces — Aero.FixedWing.Surface definitions

vector

Aero.FixedWing.Surface definitions, specified as a vector that contains the definitions of the surfaces on the fixed-wing aircraft. The object ignores this property if no value is set.

Attributes:

GetAccess	public
SetAccess	public

Data Types: double

Thrusts — Aero.FixedWing.Thrust definitions

vector

Aero.FixedWing.Thrust definitions, specified as a vector that contains the definitions of the thrust on the fixed-wing aircraft. The object ignores this property if no value is set.

Attributes:

GetAccess	public
SetAccess	public

Data Types:

Protected Properties

AspectRatio — Aspect ratio

scalar numeric

Aspect ratio, specified as a scalar numeric, commonly denoted as 'AR'. This value depends on the values of ReferencedArea and ReferenceSpan, with this equation:

AspectRatio = ReferenceSpan²/ReferencedArea

The object ignores this property if no value is set.

Attributes:

GetAccess	Restricts access
SetAccess	protected

Data Types: double

Methods

Public Methods

analyzeFlyingQualities	Compare aircraft static and dynamic stability against requirement specification
criteriaTable	Construct criteria table for fixed-wing static stability analysis
datcomToFixedWing	Construct fixed-wing aircraft from Digital DATCOM structure
forcesAndMoments	Calculate forces and moments of fixed-wing aircraft
getCoefficient	Get coefficient value for Aero.FixedWing object
getControlStates	Get control states for Aero.FixedWing object
jsbsimToFixedWing	Construct aircraft from JSBSim aircraft configuration file
linearize	Return linear state-space model
nonlinearDynamics	Calculate dynamics of fixed-wing aircraft
saveFixedWingToScript	Save FixedWing aircraft definition to MATLAB script
setCoefficient	Set coefficient value for Aero.FixedWing object
staticStability	Calculate static stability of fixed-wing aircraft
update	Update Aero.FixedWing object

Examples

Create and Use Fixed-Wing Object

Create and set up dynamic behavior and the current state for an Aero.FixedWing object aircraft.

Create a fixed-wing object.

aircraft = Aero.FixedWing()

aircraft = 
  FixedWing with properties:

        ReferenceArea: 0
        ReferenceSpan: 0
      ReferenceLength: 0
         Coefficients: [1×1 Aero.FixedWing.Coefficient]
     DegreesOfFreedom: "6DOF"
             Surfaces: [1×0 Aero.FixedWing.Surface]
              Thrusts: [1×0 Aero.FixedWing.Thrust]
          AspectRatio: NaN
           Properties: [1×1 Aero.Aircraft.Properties]
           UnitSystem: "Metric"
    TemperatureSystem: "Kelvin"
          AngleSystem: "Radians"

Define the reference area, span, and length. These quantities are used to compute forces and moments from nondimensional coefficients.

aircraft.ReferenceArea = 16;
aircraft.ReferenceSpan = 11;
aircraft.ReferenceLength = 1.5

aircraft = 
  FixedWing with properties:

        ReferenceArea: 16
        ReferenceSpan: 11
      ReferenceLength: 1.5000
         Coefficients: [1×1 Aero.FixedWing.Coefficient]
     DegreesOfFreedom: "6DOF"
             Surfaces: [1×0 Aero.FixedWing.Surface]
              Thrusts: [1×0 Aero.FixedWing.Thrust]
          AspectRatio: 7.5625
           Properties: [1×1 Aero.Aircraft.Properties]
           UnitSystem: "Metric"
    TemperatureSystem: "Kelvin"
          AngleSystem: "Radians"

To define the aircraft dynamic behavior, set lift and drag coefficients.

aircraft = setCoefficient(aircraft, ["CD", "CD", "CL", "CL"], ["Zero", "Alpha", "Zero", "Alpha"], [0.027, 0.121, 0.307, 4.41])

aircraft = 
  FixedWing with properties:

        ReferenceArea: 16
        ReferenceSpan: 11
      ReferenceLength: 1.5000
         Coefficients: [1×1 Aero.FixedWing.Coefficient]
     DegreesOfFreedom: "6DOF"
             Surfaces: [1×0 Aero.FixedWing.Surface]
              Thrusts: [1×0 Aero.FixedWing.Thrust]
          AspectRatio: 7.5625
           Properties: [1×1 Aero.Aircraft.Properties]
           UnitSystem: "Metric"
    TemperatureSystem: "Kelvin"
          AngleSystem: "Radians"

Define the current state of the aircraft.

state = Aero.FixedWing.State(...
  "Mass", 1400,...
  "Airspeed", 67,...
  "AltitudeMSL",2000)

state = 
  State with properties:

                     Mass: 1400
                  Inertia: [3×3 table]
          CenterOfGravity: [0 0 0]
         CenterOfPressure: [0 0 0]
              AltitudeMSL: 2000
             GroundHeight: 0
                       XN: 0
                       XE: 0
                       XD: -2000
                        U: 67
                        V: 0
                        W: 0
                 Airspeed: 67
                      Phi: 0
                    Theta: 0
                      Psi: 0
                        P: 0
                        Q: 0
                        R: 0
                    Alpha: 0
                     Beta: 0
                 AlphaDot: 0
                  BetaDot: 0
                   Weight: 13734
              AltitudeAGL: 2000
              GroundSpeed: 67
               MachNumber: 0.1969
             BodyVelocity: [67 0 0]
           GroundVelocity: [67 0 0]
                       Ug: 67
                       Vg: 0
                       Wg: 0
          FlightPathAngle: 0
              CourseAngle: 0
     InertialToBodyMatrix: [3×3 double]
     BodyToInertialMatrix: [3×3 double]
         BodyToWindMatrix: [3×3 double]
         WindToBodyMatrix: [3×3 double]
    BodyToStabilityMatrix: [3×3 double]
    StabilityToBodyMatrix: [3×3 double]
          DynamicPressure: 2.7495e+03
              Environment: [1×1 Aero.Aircraft.Environment]
            ControlStates: [1×0 Aero.Aircraft.ControlState]
         OutOfRangeAction: "Limit"
         DiagnosticAction: "Warning"
               Properties: [1×1 Aero.Aircraft.Properties]
               UnitSystem: "Metric"
        TemperatureSystem: "Kelvin"
              AngleSystem: "Radians"

Calculate the forces and moments on the aircraft.

[F, M] = forcesAndMoments(aircraft, state)

F = 3×1
103 ×

   -1.1878
         0
    0.2284

M = 3×1

     0
     0
     0

Limitations

You cannot subclass Aero.FixedWing.

More About

Fixed-Wing Definitions

The FixedWing object holds the main definition of a fixed-wing aircraft. The object has a main set of body coefficients defined by these tables:

Body Coefficients in Wind Frame

Body Coefficients	Wind Frame
	Zero	U	Alpha	AlphaRate	Theta	Beta	BetaRate	Phi	Psi
CD
CY
CL
CI
Cm
Cn

Body Coefficients in Body Frame

Body Coefficients	Wind Frame
	Zero	U	Alpha	AlphaRate	Theta	Beta	BetaRate	Phi	Psi
CX
CY
CZ
CI
Cm
Cn

Algorithms

Reference Quantities and Normalization

Aerodynamic coefficients in Aero.FixedWing are normalized using standard reference quantities:

• Reference Area (S_ref): The planform area of the main wing, as defined in the Fixed-Wing Definitions.

• Reference Span (b_ref): The full span of the main wing, measured tip-to-tip, used in lateral/directional coefficients (e.g., rolling/yawing moment coefficients).

• Reference Length (c_ref): The mean aerodynamic chord (MAC) of the main wing, used in longitudinal coefficients (e.g., pitching moment coefficients).

Coefficient Normalization

Use these conventions to calculate aerodynamic forces and moments:

• Lift Coefficient (CL): Represents the nondimensional measure of lift force generated by the aircraft, CL = L / (qS_ref)

• Drag Coefficient (CD): Represents the nondimensional measure of drag force experienced by the aircraft, CD = D / (qS_ref)

• Side Force Coefficient (CY): Represents the non-dimensional measure of lateral (side) force acting on the aircraft, CY = Y / (qS_ref)

• Pitching Moment Coefficient (Cm): Represents the nondimensional measure of the pitching moment (nose-up or nose-down) about the lateral axis, Cm = M / (qS_refc_ref)

• Rolling Moment Coefficient (Cl): Represents the nondimensional measure of the rolling moment (wing up/wing down) about the longitudinal axis, Cl = L_roll / (qS_refb_ref)

• Yawing Moment Coefficient (Cn): Represents the nondimensional measure of the yawing moment (nose left/nose right) about the vertical axis, Cn = N / (qS_refb_ref)

Where:

• q = 0.5ρV^² is dynamic pressure

• L, D, Y are aerodynamic forces

• M, L_roll, N are aerodynamic moments.

Reference Points

Reference points specify the locations on the aircraft where you apply different forces. Use these points to ensure consistency when defining and comparing aerodynamic coefficients and stability derivatives. What matters is the relative difference between the Center of Gravity (CG) and the Center of Pressure (CP).

• Center of Gravity: Apply body frame forces (CX, CY, CZ) to the CG.

• Center of Pressure: Apply wind and stability frame forces (CD, CY, CL) to the CP. Compute moments assuming aerodynamic forces act at the aero reference point, which may be offset from the CG.

In Aero.FixedWing.State, specify the CG and CP in body axes, with the X-axis positive toward the nose of the aircraft.

Stability and control derivatives may be referenced to either the CG or the aerodynamic reference point, depending on the analysis context.

Damping and Stability Analysis

Dynamic stability and damping derivatives are calculated using small-perturbation theory, consistent with standard aerodynamic texts. For example:

• Damping Derivatives: Rolling, pitching, and yawing moment damping derivatives (Clp, Cmq, Cnr) are computed using normalized rates:

  • Roll rate (p) normalized by b_ref / 2V

  • Pitch rate (q) normalized by c_ref / 2V

  • Yaw rate (r) normalized by b_ref / 2V

Assumptions and Limitations

• All aerodynamic coefficients assume small angle approximations unless otherwise specified.

• The aerodynamic model assumes steady, incompressible flow unless a compressibility correction is applied.

• Effects such as ground effect, propwash, or nonlinear aerodynamics are not included unless explicitly modeled.

Version History

Introduced in R2021a