Digital DATCOM Forces and Moments

Compute aerodynamic forces and moments using Digital DATCOM static and dynamic stability derivatives

  • Library:
  • Aerospace Blockset / Aerodynamics

Description

The Digital DATCOM Forces and Moments block computes the aerodynamic forces and moments about the center of gravity using aerodynamic coefficients from Digital DATCOM.

Limitations

  • The Digital DATCOM Forces and Moments block supports only Digital DATCOM, which is the 1976 version of DATCOM.

  • The operational limitations of Digital DATCOM apply to the data contained in the Digital DATCOM structure parameter. For more information on Digital DATCOM limitations, see Section 2.4.5 of reference [1].

  • The Digital DATCOM structure parameters alpha, mach, alt, grndht, and delta must be strictly monotonically increasing to be used with the Digital DATCOM Forces and Moments block.

  • The Digital DATCOM structure coefficients must correspond to the dimensions of the breakpoints (alpha, mach, alt, grndht, and delta) to be used with the Digital DATCOM Forces and Moments block.

Ports

Input

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Angle of attack, specified as a scalar.

Data Types: double

Sideslip angle, specified as a scalar, in radians.

Data Types: double

Mach number, specified as a scalar.

Data Types: double

Altitude, specified as a scalar, in selected length units.

Data Types: double

Dynamic pressure, specified as a scalar, in selected pressure units.

Data Types: double

Velocity, specified as a three-element vector, in selected velocity units and selected force axes.

Data Types: double

Angle of attack rate, specified as a scalar, in radians per second.

Dependencies

Appears when DAMP Control Card is used in input to Digital DATCOM.

Data Types: double

Body angular rates, specified as a three-element vector, in radians per second.

Dependencies

Appears when DAMP Control Card is used in input to Digital DATCOM.

Data Types: double

Ground height, specified as a scalar, in select units of length.

Dependencies

Appears when GRNDEF Namelist is used in input to Digital DATCOM.

Data Types: double

Control surface deflection, specified as a scalar, in radians.

Dependencies

Appears when ASYFLP or SYMFLP and GRNDEF namelists are used in input to Digital DATCOM.

Data Types: double

Output

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Aerodynamic forces at the center of gravity, returned as a three-element vector, in selected coordinate system: Body (F, Fyx, and Fz), or Wind (FD, Fy, and FL).

Data Types: double

Aerodynamic moments at the center of gravity, returned as a three-element vector, in body coordinates (Mx, My, and Mz).

Data Types: double

Parameters

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Input and output units, specified as:

Units

Force

Moment

Length

Velocity

Pressure

Metric (MKS)

Newton

Newton-
meter

Meters

Meters per second

Pascal

English (Velocity in ft/s)

Pound

Foot-pound

Feet

Feet per second

Pound per square inch

English (Velocity in kts)

Pound

Foot-pound

Feet

Knots

Pound per square inch

Programmatic Use

Block Parameter: units
Type: character vector
Values: 'Metric (MKS)' | 'English (Velocity in ft/s)' | 'English (Velocity in kts)'
Default: 'Metric (MKS)'

MATLAB® structure containing the digital DATCOM data. This structure is generated by the datcomimport function. To include dynamic derivatives in the generated output file, call the datomimport function with the damp keyword.

For more information on creating the digital DATCOM structure, see Importing from USAF Digital DATCOM Files (Aerospace Toolbox). This example shows how to bring United States Air Force (USAF) Digital DATCOM files into the MATLAB environment using the Aerospace Toolbox software.

Programmatic Use

Block Parameter: dcase
Type: character vector
Values: factstruct{1} | structure
Default: factstruct{1}

Coordinate system for aerodynamic force, specified as Body or Wind.

Programmatic Use

Block Parameter: fmode
Type: character vector
Values: 'Body' | 'Wind'
Default: 'Body'

Interpolation method, specified as None (flat) or Linear. The block uses the interpolation method to interpolate the static and dynamic stability coefficients in the Digital DATCOM structure.

Programmatic Use

Block Parameter: imethod
Type: character vector
Values: 'None (flat)' | 'Linear'
Default: 'None (flat)'

Extrapolation method, specified as None (clip) or Linear. The block uses the extrapolation method to extrapolate the static and dynamic stability coefficients in the Digital DATCOM structure.

Programmatic Use

Block Parameter: emethod
Type: character vector
Values: 'None (flat)' | 'Linear'
Default: 'None (flat)'

Handle out-of-range input action, Linear Extrapolation or Clip to Range.

Programmatic Use

Block Parameter: rmethod
Type: character vector
Values: 'Clip to Range' | 'Linear Extrapolation'
Default: 'Clip to Range'

Out-of-range block behavior, specified as follows.

ActionDescription

None

No action.

Warning

Warning in the MATLAB Command Window, model simulation continues.

Error (default)

MATLAB returns an exception, model simulation stops.

Programmatic Use

Block Parameter: action
Type: character vector
Values: 'None' | 'Warning' | 'Error'
Default: 'None'

Algorithms

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Algorithms for calculating forces and moments build up the overall aerodynamic forces and moments (F and M) from data contained in the Digital DATCOM structure parameter:

F = F static + F dyn (1)
M = M static + M dyn (2)

Fstatic and Mstatic are the static contribution, and Fdyn and Mdyn the dynamic contribution, to the aerodynamic coefficients. If the dynamic characteristics are not contained in the Digital DATCOM structure parameter, their contribution is set to zero.

References

[1] The USAF Stability and Control Digital Datcom, AFFDL-TR-79-3032, 1979.

[2] Etkin, B., and L. D. Reid. Dynamics of Flight Stability and Control, Hoboken, NJ: John Wiley & Sons, 1996.

[3] Roskam, J. "Airplane Design Part VI: Preliminary Calculation of Aerodynamic, Thrust and Power Characteristics", Roskam Aviation and Engineering Corporation, Ottawa, Kansas: 1987.

[4] Stevens, B. L., and F. L. Lewis. Aircraft Control and Simulation, Hoboken, NJ: John Wiley & Sons, 1992.

Introduced in R2006b