Calculate wind shear conditions

Environment/Wind

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.

$${u}_{w}={W}_{20}\frac{\mathrm{ln}\left(\frac{h}{{z}_{0}}\right)}{\mathrm{ln}\left(\frac{20}{{z}_{0}}\right)},\text{}3fth1000ft$$

where *u _{w}* is the mean
wind speed,

The resultant mean wind speed in the flat Earth 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.

**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.

Input | Dimension Type | Description |
---|---|---|

First | Contains the altitude in units selected. | |

Second | 3-by-3 direction cosine matrix |

Output | Dimension Type | Description |
---|---|---|

First | 3-by-1 vector | Contains the mean wind speed in the body axes frame, in the selected units. |

See ```
Wind
Shear Model
```

in `aeroblk_HL20`

for
an example of this block.

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