Aerospace Blockset™

COESA Atmosphere Model - Implement 1976 COESA lower atmosphere

Library

Environment/Atmosphere

Description

The COESA Atmosphere Model block implements the mathematical representation of the 1976 Committee on Extension to the Standard Atmosphere (COESA) United States standard lower atmospheric values for absolute temperature, pressure, density, and speed of sound for the input geopotential altitude.

Below 32,000 meters (approximately 104,987 feet), the U.S. Standard Atmosphere is identical with the Standard Atmosphere of the International Civil Aviation Organization (ICAO).

The COESA Atmosphere Model block icon displays the input and output units selected from the Units list.

Dialog Box

Units

Specifies the input and output units:

Units	Height	Temperature	Speed of Sound	Air Pressure	Air Density
`Metric (MKS)`	Meters	Kelvin	Meters per second	Pascal	Kilograms per cubic meter
`English (Velocity in ft/s)`	Feet	Degrees Rankine	Feet per second	Pound-force per square inch	Slug per cubic foot
`English (Velocity in kts)`	Feet	Degrees Rankine	Knots	Pound-force per square inch	Slug per cubic foot

Specification

Specify the atmosphere model type from one of the following atmosphere models. The default is 1976 COESA-extended U.S. Standard Atmosphere.

MIL-HDBK-310

This selection is linked to the Non-Standard Day 310 block. See the block reference for more information.

MIL-STD-210C

This selection is linked to the Non-Standard Day 210C block. See the block reference for more information.

Action for out of range input

Specify if out-of-range input invokes a warning, error, or no action.

Inputs and Outputs

Input	Dimension Type	Description
First		Contains the geopotential height.

Output	Dimension Type	Description
First		Contains the temperature.
Second		Contains the speed of sound.
Third		Contains the air pressure.
Fourth		Contains the air density.

Assumptions and Limitations

Below the geopotential altitude of 0 m (0 feet) and above the geopotential altitude of 84,852 m (approximately 278,386 feet), temperature values are extrapolated linearly and pressure values are extrapolated logarithmically. Density and speed of sound are calculated using a perfect gas relationship.

Examples

See the aeroblk_calibrated model, the aeroblk_indicated model, and the airframe in the aeroblk_HL20 demo for examples of this block.

Reference

U.S. Standard Atmosphere, 1976, U.S. Government Printing Office, Washington, D.C.