Aerospace Blockset™

Wind Shear Model - Calculate wind shear conditions

Library

Environment/Wind

Description

The Wind Shear Model block adds wind shear to the aerospace model. This implementation is based on the mathematical representation in the Military Specification MIL-F-8785C [1]. The magnitude of the wind shear is given by the following equation for the mean wind profile as a function of altitude and the measured wind speed at 20 feet (6 m) above the ground.

where u_w is the mean wind speed, W₂₀ is the measured wind speed at an altitude of 20 feet, is the altitude, and is a constant equal to 0.15 feet for Category C flight phases and 2.0 feet for all other flight phases. Category C flight phases are defined in reference [1] to be terminal flight phases, which include takeoff, approach, and landing.

The resultant mean wind speed in the Earth-fixed axis frame is changed to body-fixed axis coordinates by multiplying by the direction cosine matrix (DCM) input to the block. The block output is the mean wind speed in the body-fixed axis.

Dialog Box

Units

Define the units of wind shear.

Units	Wind	Altitude
Metric (MKS)	Meters/second	Meters
English (Velocity in ft/s)	Feet/second	Feet
English (Velocity in kts)	Knots	Feet

Flight phase

Select flight phase:

• Category C — Terminal Flight Phases

• Other

Wind speed at 6 m (20 feet) altitude (m/s, f/s, or knots)

The measured wind speed at an altitude of 20 feet (6 m) above the ground.

Wind direction at 6 m (20 feet) altitude (degrees clockwise from north)

The direction of the wind at an altitude of 20 feet (6 m), measured in degrees clockwise from the direction of the Earth x-axis (north). The wind direction is defined as the direction from which the wind is coming.

Inputs and Outputs

Examples

See the Airframe subsystem in the aeroblk_HL20 model for an example of this block.

Reference

U.S. Military Specification MIL-F-8785C, 5 November 1980.

See Also

Discrete Wind Gust Model

Dryden Wind Turbulence Model (Continuous)

Dryden Wind Turbulence Model (Discrete)

Von Karman Wind Turbulence Model (Continuous)

Wind Angular Rates

World Magnetic Model 2000